REPORTS
OF PATENT, DESIGN, AND TRADE MARK CASESr EDITOR: FRANK G. UNDERHAY, M.A., BARRISTER-AT-LAW. Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 Vol. XLV.] 18TH JANUARY, 1928. [No.1.
IN THE HOUSE OF LORDS.
Present: Lords DUNEDIN, SUMNER AND BLANESBURGR.
March 7th, 8th, 10th, 11th, 17th, 18th, 21st and 22nd and July 25th and 29th.
BRITISH THOMSON-HoUSTON 00. LD. v. METROPOLITAN-VICKERS ELECTRICAL 00. LD.
5 Patent.-Action 101" inlringement.-Infringement.-Novelty.-Subject-matter. Patent held infringed but invalid.-Action dismissed.-Appeal.-Patent held: valid and to have been infringed.-Appeal to the Court of Appeal allowed.• Appeal to the House of Lords dismissed. A Patent was granted to R. for "Improvements relat·ing to Synchronous 10 "Dynamo Electric Machines." Claim 1 of the Specification was as follows:• " Arrangement lor starting synchronous dynamo electric machines by means of "an electric motor, in u,hich a series or electrically equivalent connection is "pro'vided between the windings of the starting motOr and the synchronous "machine, for the purpose 01 effecting in one operation both the speeding up 15 "and the synchronising of the synchronous machine with the supply current." The Plaintiffs alleged infringement of the Claim by the sale by the Defendants of a rotary converter to West Hartlepool Oorporation. The Defendants alleged that the Patent was invalid by reason of want of novelty and of subject-matter. At the trial the Defendants relied upon the publication of the Specification of an 20 U.S.A. Patent which showed an arranJ1ement which was capable of being user! in the manner ind.icated by R. They a,[so contended that the series connection in the alleged infringement did not perform the function specified in the Claim. The Plaintiffs contended that the prior arrangement was not suitable for the purpose claimed, and that the Patentee had selected useful members from a 25 krwwn class and applied them to a new object. The U.S.A. Patent had not been, used. .4t the trial it was held, that the Patent was anticipated by the" A 2
No. 1.] REPORTS OF PATmNT, D$IGN, AND TRADE MARK OASES. [Vol. XLV.
British Thomson-Houston 00. Ld. v. Metropolita'Tlr-Vickers Electrical 00. Ld.
U.S.A. Specification and was invalid, but that, if it had been valid, the Claim would have been infringed. The action was dismissed, tke PlaintiffB being ordered to pay tke general costs of the action and the costs of the issue raised by the Particulars of Objection, and tke Defendants being ordered to pay the Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 costs of the issues raised by the Particulars of Breackes with a set off· The 5 Plaintiffs appealed to tke Court of Appeal on the issue of validity. It was held that it is not enough to show that an apparatus described in an earlier specification alleged as an anticipa.tion could have been used to produce a certain result; it must also be shown that tke specification contains clear and unmistakable directions so to use it; that the Patent was not anticipated by the 10 U.S.A. Specification, and w'as valid and had been infringed. The Appeal was allowed with costs in the Oourt of Appeal and below, and an injunction and an inquiry as to damages were granted. The Defendants appealed to the House of Lords. The Appeal was dismissed with costs. 15 On the 23rd of April, 1912, Letters Patent (No. 9644 of 1912) were granted to Emanuel Rosenberg for "Improvements relating to Synchronous Dynamo " Electric Machines" and prior to the acts complained of in this action were assigned to the Plaintiffs. The Oomplete Specification, with the drawings, so far ws material for the purpose of this report, is set out in the report of the 20 trial of the action, 42 R.P.O. at p. 144 et seq. The Patentee claimed:- " 1. Arrangement for starting synchronous dynamo electri~ machines by , "means of an electric motor" in which a series or electricaHy equivalent con- :: nectihon is provihd~d bfetwetehn the windifngsff o!. the. starting mOt~or bantdh tthhe 21). sync ronous mac Ine, or e purpose 0 e eCLIng In one opera IOn 0 e "speeding up and the synchronising of the synchronous machine WIth the " supply current. "2. In an arrangement for starting synchronous dynamo electric machines " according to Olaim 1, means for reveNing the direction of the field exciting " current, or for opening the field cir·cuit or reducing the current in the field 30 " circuit of the synchronous machine during the starting period, substantially " as and for the purpose set forth. "3. In an arrangement according to Olaim 1 for starting a rotary converter " connected to a mechanically coupled alternating current booster machine, the 35 " provision of an additional winding on the booster machine, to enable this to ., be used as a starting and synchronising motor, substantially as described. " 4. Arrang·ements for starting and synchronising synchronous dynamo "electric machines, substantially as described and illustrated in any of the "figures of the accompanying drawings." Figures 1 and 2 of Rosenberg's Specification are shown on page 3- 40 The Plaintiffs by their Statement of Claim alleged as follows:- (1) 'l'he Plaintiffs were the registered legal owners of the Patent; (2) The Defendants had infringed and threatened and intended to infringe the Patent. By their Particulars of Breaches they alleged as follows:-(i) The Defendants had infringed the Patent by manufacturing, sel)ing and using rotallY con¥erters 45 3·
Vol. XLV.] REPORTS OF PATl!lNT, DESIGN, AND TRADE MARK CASES. [No.1.
British Thomson-Houston Co. Ld. v. Metropolita'flrVickers Electrical Co. Ld.
constructed in accordance with the invention as claimed in aU the claiming clauses of the Specification; (2) In particular the Plaintiffs co~plained of the sale towards the end of the year 1913 by the Defendants to the West Hartlepool Cornoration of two 300 K.W. rotary converters constructed as aforesaid. Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021
F,ig.l.
+ 5 The Defendants by the Defence (1) madie no admissions with regard to paragraph 1 of the statement of Claim; (2) alleged that they had not infringed and did not threaten nor intend to infringe; and (3) alleged that the Patent was invalid. The Particulars of Objections will be found set out in 42 R.P.C. at p. 149. 10 Of the prior documents therein specified only the U.S.A. Specification of l'esla (No. 459,772) was relied upon in the Court of Appeal and this is set out in 42 R.P.C. at p. 151 et seq. Figures 4, 5, 8 and 9 of Tesla are shown on page 4. A diagrammatic representation of the Defendants' apparatus is shown on page 5. 15 The action came on for trial on the 8th of July, 1924, before Mr. Justice P. O. Lawrence who held that the Plaintiffs' Patent was anticipated by the U.S.A. Specification of Tesla and WIIiS invalid, but that, if it had been valid, the Claim would have been infringed. The action was dismissed, the Plaintiffs being ordered to pay the general costs of the action and the costs of the issue 20 raised by the Particulars of Objection, and the Defendants being ordered to pay the costs of the issues raised by the Particulars of Breaches with a set off. The Plaintiffs appealed to the Court of Appeal...... It was held that it is not enough to show that an earlier specification alleged as an anticipation could have been used to pI\oduce a certain result; it must A2 4
No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [Vol. XLV. --"-"-""------British Thomson-Houston Co. Ld. v. Metropolita'llrVickers Electrical Co. Ld. also be sho~n that the specification contains clear and unmistakable instructions so to use it; that the Patent was not anticipated by the U. S.A. Specification and was valid and had been infringed. The Appeal was allowed with costs in the Oourt of Appeal and below, and an injunction and inquiry as to damages were granted. 50· Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021
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The Defendants appealed to the House of Lords. Sir Arthur Oole/a):}; K.O., W. Trevor Watson and B. Sandeman (instructed'. by A. R. Monks) appeared for the Appellants. Vol. XLV.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [No. 1.
British Thomson-Houston 00. Ld. v. MetropolitanrVickers Electrical Co. Ld.
Sir Duncan M. Kerly KO., J. Whitehead KO., J. M. McEwen 'and James Mould (instructed hy Faith/ull, Owen and Fraser) appeared for the Respondents. Sir A. Cole/ax, KG., for the Appellants.-The only cla-im of Rosenberg's Patent which is alleged to he infringed is Olaim 1, and, if the construction is Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 DIAGRAM OF COIYNecTiONS.
THROW SWITCH.
3 POLl! JINGLE THROW .5wlrCH WITH IIYTERMEOI•• TE CONTACTS.
STARTING MOTOR.
METHOD OF STARTING I. CLOSE SWI7'CHE5 / ~ 2. JO COtvtvECT/N(i THE STARTING MOTOR IN SI!RIE$ 11//TH THE" ROTARY. II. WHEN APPI(OX" FULL SPEED /5 REACHED, ClOSE SWITCH o.v fX)I'ITACTS 5 so C.lJNNECTING CHOKE
COILS IN PARALLEL WlrH STI'tI :> accepted which the Appellants have throughout contended for, there is no issue of infringement. If, on the other hand, the Respondents' const,ruction is accepted, there is an issue of infringement. The validity of Rosenberg's Patent is attacked on two grounds, novelty an,d subject-matter and the only document relied upon in this attack is Tesla's U.S.A. Specifica,tion, No. 459772 of 1891. 6 No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE :MARK CASES. [Vol. XLV. BNtiah Tho1n8on-Houston 00. Ld. v. Metropolitan-Vickers Electrical 00. Ld. In any dynamo electric' machine there are two parts, a stator and a rotor and the current to drive the mllichine, if it is a motor, may be supplied to either the rotor or to the stator. In a synchronous machine the non-supply part is always provided with polar projections whereas in a non-synchronous machine there are Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 no such polar projections. [Sir n. M. K,erl'l/ K.C.-That is a ne~ method. of :) approaching the matter I remember no eVidence below of the necessity of havmg polar projections and it is a matter of considerable controversy.] A non• synchronous motor can never run at synchronous speed, but it can start from rest and incidentally it has no axis along which it is most easily magnetisable, and hlUl therefore no tendency to lock in any position. When a synchronous machine lO• is in synchronism, its most easily magnetisable axis on the non-supply part is rotating in coincidence with the rotating axis of the maximum strength of the rotating magnetic field produced by the alternating current supplied to the supply part. This involves two things, one, that the ·speed is correct and two, the ooincidence of the magp.etic axes. [Viscount DUNEDIN.-What do you gain 1:) by synchronism 1] The machine works most efficiently, that is it will work with least current for a given load. If there is not coincidence between the magnetic axes, the air gap between stator and rotor will vary and cause the current sup• plied to vary, but with synchronism you have continuously the smallest air gap being preserved between the two. A non-sychronous motor is a torque motor for 2() the reason that the moment you put the current on to it you have a secondary magnetic field produced in the rotor and with the interaction between that :and the rotating field of the stator the machine runs up. As you approach synchrono?-s speed, the rotating ma.gnetic field cuts the coils of the rotor at a diminished rate and the secondary magnetic field is reduced and the torque falls 25· off. Both Rosenberg's and Tesla's Specifications deal with a problem of starting a synchronous machine, not merely in the sense of beginning to run from rest but in bringing the machine into synchronism. In Tesla's Specification the machine which has to be got into synchronism is a single phase machine. PolyphlUle machines mayor may not have been known at his date, but he only 30' dealt with single phase. There is no difference between single phase and poly• phase machines as regards what synchronism mea.ns applied thereto. Rosenberg includes ·single pha;se machines and his claim includes what is in Tesla, and is attacked: upon that ground. Rosenberg's claim may include more than is disclosed by Tesla but does include Tesla, and in any case there is no 35- patentable subject-matter in what may be added. A single phase motor is more difficult to start fr.om rest because you have got an alternation of poles instead of a r.otation and therefore it locks. This will prevent a single phase .synchronous motor starting from rest if you put it on the mains, because you have not .only got inertia to overcome but inertia and locking. Once you have 40 got sufficient speed to get over the lock there is a tendency to synchronism in the single phase just as in the polyphase machine. That is all the effort of self synchronisation. The difficulty of starting from rest and the difficulty of running up, unless you have got sufficiently near synchronous speed before you proceed to energise, is characteristic ofa single phase motor. The purpose of a 45 rotary converter is to produce direct current from alternating 'current, and it does so 'by the addition of a commutator. Ordinarily in a rotary converter there is direct current excitation of the polar projections of the non-supply part derived from the commutator. The direct current excitation does not occur unless and until the rotary converter is running in synchronism. A non- 50. synchronous motor is sometimes spoken of as a torque motor and sometimes as 7 Vol. XLV.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [No. 1. British Thomson-Houston Do. Ld. v. Metropolitan-Vickers Electrical Go. Ld. an induction motor. An, induction motor is the antithesis of a motor in which there is direct excitation of the polar projections, an induction motor may therefore be either a synchronous or a non-synchronous motor. Rosenberg's document is concerned with starting a synchronous machine, not Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 I') in the sense of getting it moving from rest, but in the sense of bringing it into an operative condition. At the date of the Patent there were three methods of starting asyn,chronous machine. One was to put it direct on the supply when at rest, and that was usually done by the interposition of resistance which would limit the current reaching the machine from the supply. The second method 10 was to interpose a transformer, so that the machine got only a fraction of the supply voltage, and: that was known as tap starting. The third method was pony motor starting where you turned the synchronous machine round by a pony motO'r untilsynchronO'us speed was reached and then, having got the phase of the generated E.'M.F. coincident with that of the supply by means of a lamp 16 device, switched it on to the supply. Rosenberg made a series connection between tlie synchronous machine and the pony motO'r, so that the same current went through bO'th and the two together were on the supply until the synchrO'nous machine got into synchronism, when they could continue to run together or the pony motor could be cut out. For the purpose O'f getting intO' 20 synchronism and taking advantage of the alleged invention it does not matter whether the synchronO'us machine is put in series at rest or whether you wait until substantially synchronous speed is reached. What is said to be the advantage of the Patent is that you dispense with the operation of synchronising with lamps, which is inherent in the third method. The Appellants rely upon 25 Tesla's document as destructive of novelty and subject-matter. It is concerned with starting a single phase synchronous machine from rest and it may be divided into three divisions describing three different methods of procedure. One of those divisions describes an ,arrangement which is identical with that claimed. If there is any distinction between the two arrangements, then the 30 Appellants call in aid common knowledge in 1891 supplemented as it was by 1912. Tesla was not common knowledge but it was public knowledge and should be read in the light of common knowledge, and is destructive of subject-matter in Rosenberg's Claim. The Court of Appeal has never cO'nstrued Rosenberg's Claim and have treated it as a claim to' a methO'd of user as distinct frO'm an 35 arr,angement, and said" Tesla does nO't tell you the advantage of the series con- • "nectiO'n." That is immaterial because Rosenberg claims an arrangement and the series connection cannO't help but O'perate in all cases in the same way. Of the three methods O'f starting twO' gave autO'matic synchronisation and the third, pony motO'r starting, was not automatic. Rosenberg is concerned with the third 40 method; he r,an the machine up with the PO'ny mO'tor to somewhere short of synchronous speed and then made the series connectiO'n, whereby, when synchronous speed was attained.. he :had his machine in synchronism. Tesla was concerned, in the first instance in getting 'a single phase machine started from rest. He then proposed ,a seriescO'nnection for running the machines together 45 on load, but also provides a means fO'r cutting out the starting motor. In one of his figures he has an arrangement which is identical with that claimed in Rosenberg. It is said Tesla does not tell you to use this arrang,ement in the way Rosenberg tells you to use it. That is immaterial because Rosenberg' 8 Claim is for an arrangement, not for a method of user. The consequence O'f the series 50 connection is the same in both arrangements. The starting motor must shield the synchronO'us machine though nO' doubt the extent of shielding is a matter of 8 ND. 1.J REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [Vol. XLV. British Thomson-Houston Co. Ld. v. Metropolitan-Vickers Electrical Co. Ld. design and will he small if the tWD are to run together Dn load. AnDth;er matter that flows from the series connectiDn is the transference of voltage whICh occurs at synchronism. That is inherent in the series ,connection, and, though there is nothing in Tesla about the starting motor acting as a shield or transference .of voltage, they must occur. It' is said synchrDnDus machines were small at the 5 Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 date of Tesla, that is true, but the conditions of synchronous action were well understood by engineers. It is suggested that Tesla never had in mind getting into step, but that is absurd because .a synchronous machine cannot· continue unless it is in step and Tesla understDDd that. It is true that Rosenberg came as a surprise tD engineers in 1912, but Tesla was not CDmmDn knDwledge but 10 only pubhc. Any engineer reading Tesla in 1912 wDuld have realised that shielding, transference Df voltag,e and automatic synchrDnising were the cDnse• quences Df the series cDnnectiDn. An attempt is made tD intrDduce a limitatiDn intD Rosenberg's Claim which necessitates pairing of the tWD ma.chines in such a way that the current is limited tD avoid reversal Df pDlarity. That cDuld Dnly 15 apply tD a rDtary cDnverter, but even SD there can be no such limitatiDn because he describes an arrangement, which is included in his Claim, in which he allDws sufficient current tD r,everse the polarity and then 'CDrrects it afterwards. Claim 1 of Rosenberg has nD limitatiDns at all, it is merely an arrangement using the series .cDnnectiDn tD avoid the step Df synchrDnising, and in figure 5 Df 20 Tesla there is an arrangement in which it is impossible for the synchrDnous motor toO get into synchronism except when it is in series with the starting motor. In that figure 5 there are no means of cutting Dut the starting motor. [Lord BLANESBURGH.-I suppDse your broad case is that Rosenberg's Specification has been framed in ignDrance of Tesla and, if it had been framed with Tesla before 25 him, it would have been very different.J Yes. [Lord BLANESBURGH.-DD you say, if the Respondent's view of the Patent is ·correct you have nOot infring,ed, because you have never used the machine.J Yes. [On the question of a paper anticipation, Hills v. Evans (186.2) 31 L.J. Ohancery 463; Otto v. Linford (1881) 46 L.T. 35; Flour Oxidising Go. Ld. v. Garr (1908) 25 R.P.O. 457; Armstrong, 30 Whitworth &; Go. Ld. v. Hardcastle (1925) 42 R.P.O. 543; King Brown &: Goo. v. Anglo .American Brush Go. (1892) 9 R.P.O. 313 and Ralston v. Smith (1865) 11 H.L.O. 223 were referred to.] Trevor Watson followed for the Appellants.-The Respondents have critici!sed Tesla's Specification from a number .of different points of view. They say 35 Tesla did n.ot make Rosenberg's discovery, get his iilea, make his invention- or appreei~ate his advantages, in short, Teslaand Rosenberg intended to opera.te their switches in a different order. Even if all these que.stions were resolved in the Respondents' favour, they would not dispose of the matter, because one has finally to settle two questions. First, do those considerations impose any 40 and what limitation on Rosenberg's Olaim 7 and secondly, the limita,tion being defined, is it one which will exclude Tesla? There are tIDree things in Rosen• berg's Claim :-1. The arrangement. 2. The apparatus and 3. The purpose. If the Claim means any torque motDr in series with any synchronous machine there is complete anticipation, because all Rosenberg has done is to discover 45 advantages of an existing arrangement. One must therefore see whether tIDe body of the SpecificatiDn imposes any limit Dn the claim. The purpose cannot limit the elaim, because it i1s for an arrangement and not a method of user. It is true Tesla contemplated making his series connection some time after the start and not at rest, but, if that is to make a limitation, it must limit the 50 arrangement and not the method, and that would come down tD tIDe difference Vol. XLV.] REPORTS OF PATEiNT, DESIGN, AND TRADE MARK CASES. [No. 1. British Thomson-Houston Co. Ld. v. MetropoZita'IV-Vickers Electrical Co. Ld. being that Rosenberg has omitted the switch by which Tesla cuts out his synchronous machine. Making the series connection from the start is admitted to be a disadvantage, and 'so by this means the Respondents are seeking to find subjectrmatter in a retrograde step. It cannot be that Rosenberg's Olaim 3 involves that you should put in the switch and then have nothing further to Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 do, because his Olaim covers all his arrangements and he shows some having pole ¢langing switches which have to be manipulated. In figure 5 Tesla gets the full advantage of Rosenberg if he makes the series connection when he hM got past the speed at which it will lock and before synchronous speed. The 10 only way that Respondents could get rid of figure 5 would be by showing that it requi!red some operation like 'synchronising. In seeing wihether the body of the specification imports limitations into the claim one is entitled to say that, where the patente,e sets out certain advantages which he is aimilng at, the Olaim should not be readJ so broadly as to cover ,something which does not give those 15 advantages; but tha,t is quite different from exduding from tihe ambit of the document cases where the advantage to be obtained is not a necessary one. If the Respondents are going to dispose of Tesla as an anticipation they fail upon another ground, ambiguity. National Colour Kinematograph Co. v. Bioschemes Ld. (1915) 32 R.P.C. 257. It is impossible to tell what the limitation 20 is to be. Another aspect of ambiguity raii!ed in this case is that the Claim is drawn in such a form tihat one cannot say whether it is an apparatus or a user claim. That has caused the difference betw,een Lawrence J. and the Oourt of Appeal. The Respondents 'Say it is an apparatus claim conditioned by user, but that raises an ambiguifty as to the kind of infringement against which the 25 claim may be directed. Sir D. M. Kerly K.O., for Respondents.-The case which the Appellants are asking your Lordships to ,accept is that a mere paper anticipation shall upset and destroy what is an unexpected and valuable invention which came as a surprise to el,ectrical engineers and met a long-felt want, and was adopted 30 by the Appellants themselvels. The question is not what Tesla claimed but what Tesla described. [Lord BLANESBURGH.-In construing Rosenberg you must begin as if you knew nothing of Tesla?] Theoretically; but, ilf one has one's attention directed toO a danger, one takes more care. It is Isaid you must treat Tesla as if it had been presented to a man who in 1912 was desiring to solve 35' Rosenberg's problem. That is wrong, many ,an invention finds its merit first of all in appreciating the problem. It may be in tihe ingenuity to appreciate and fo-rmulate your problem, and so go and look for your Tesla, that the merit of the invention lies. Tesla at most shows a couple of motors and a collection of 'switches He, never shows those thi'ngs set or arranged during the starting 40 period so as to fit Rosenberg's claims or his invention. He not only did not do so, but could not do soo because of the lock which we know existed on his maClhine. Tesla was a mere a,ttempt to deal with a particular and very curious synchronous machi!ne .and to overcome a defect which was peculiar to it, namely, to ge,t over tihe lock. Tesla neitiher stated, appreciated nor solved Rosenberg's 45 problem, which was to get a synchronous machine, and' a big synchronous machine, on to the mains without risk to the maOhine or inconvenience to the supply. Tesla had nothing to do with mai!ns, lie had his own separate generator and in the circumstances with which he was dealing tihere was no possibility of risk to his maehines. Further, Tesla's machine was absurd and ilmpracticable 50 and he himself did not understand it. There are, errors in Te.sla which are sufficient to. cause any modern engineer to whom it might have been pre'Sented 10 No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [Vol. XLV. British Thomson-Houston Co. Ld. v. Metropolita'flrVickers Electrical Co. Ld. to put it aside at onoo. [Lord BLANESBURGH.-If you are right in your last statement, you would be entitled in law to say it was not public knowledge qua Rosenberg's Patent 1] It would not be destructive public knowledge. There is authority to the effect that, if a thing is absurd in i11s setting, th6 Oourt may put it aside. It is asked, what possible iimiltations can be put upon Rosen·· 5 Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 berg? [Lord BLANESBURGH.-You begin by recognising 1iliat you have to put some limitations upon it in order to support it1] No. You may take ilt, first of all, as a mer6 collection of apparatus. That is clearly wrong. It must be a starting motor and a synchronous dynamo electric machine connected in ·series. They may be connected in seri~s either at rest or at some period! befor6 starting l() has been completed. Then comes the question, is Claim 1 to be further limited to such a collection of motors and switches as will give the advantages which are described alB the object of tihe invention 1 That ils pairing. The Respondents say it is to be so limited. A third possible construction is for a me1iliod of working. As regards infringement, that is of importance if Respondents are 15 to lose some of the costs of this action, but it is relatively unimportant com• pared with validity, because the machine actually sued on is a fr,eak and there are many othe·r machines of the Appellants which are clear infringements. 'lllie AppeUants say that, i1 you only get series, it does not matter what the relation between the macliines is, pairing is of no consequence, and at the 20 same time they are saying that the se,ries connection in the partilcular apparatus I am complaining of did not .ana. could not effect synchronisation without damage to the machines and danger. The starting motor has to be capable of pedorming its task, and it has three things to do. It must allow sufficient current to pass to synchronise, it must not allow so much to pass as will injure 25 the synchronous machine or upset tlie supply mains, and, lastly, the pair must be so designed! that there is a transference of voltage at synchronisation from the starting motor to the synchronous machine. UnleSs you get the transference of voltage, you cannot cut out the starti1ng motor as is contemplated by Rosenberg and if, as in Testa, the two are to Tun, together on load the starting 30 motor must always be absorbing some of the voltage, and if an attempt were made to cut it out a big voltage would suddenly be thrown on the synchronous ma.chine and on6 of the dangers which Rosenberg is trying to avoid would be incurred. [LoTd DUNEDIN.-Take the Rosenberg Claim; it says: "Arrangements "for startilng synchronous-dynamo electric machines by means of an electrio 35 "motor, in which a series connection is providJed between the windings," and so on. He says, "What I claim is ·an arrangement." If that mea.ns all arrange• ments in which series is used, would not ilt be made bad by its being shown that there had ,already been arrangements in which series was used n Yes, but iihat is not a proper construction of Rosenberg. My construction of Rosenberg 40 is this, an arrangement by which modern synohronous motors, such motors as had been started with a pony motor and lamp's or by tap starting, may be started on modern supply mains without danger of rush of current, such as would upset the supply or might injure the machine itself, merely by switching on alternating current from iihe mains, and constituted by a 'Starting motor 4-5 connected in seri'es with the synchronous machine, the arrangement being such that synchronous speed, step and transfer of voltage from the 'starting motor to the synchronous machine is automatic, without ,a.ny further manual action after switching on. This construction imports four things, firs.t, there must be a synchronous machi1ne with fixed magnets, second, a starting motor which 50 when running at or near the synchronous speed of the Isynchronous machine 11 Vol. XLV.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [No. 1. British Thomson-Houston. Co. Ld. v. Metropolitan-Vickers Electrical Co. Ld. will pass enough current to synchronise it, thilrd, a startIng motor which will absorb no appreciable voltage when the synchronous machine, is in 'Synchronism, so that it can be cut out without shock to the synchronous machine, and, fourth, an arrangement wihich will start from rest. There are nine reasons why Te,sla 5 does not come within this definiition of Rosenberg. Tesla describes a machine Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 which is not a mode,rn synchronous macliine at all, such as could be used with pony motor or tap starting. It had no fixed magnets nor direct-current excitation, and was merely' an induction machilne, though a peculiar one and capable of running at synchronous speed. Also, there was no dange.r of a rush 10 .of current. Tesla does not describe a sta.rOOr which will solve the Rosenberg probl.em. Except so far as it descrihes a series arrangement Tesla's specification is wholly iI:relevant, and so far as it doe's describe a series arrangement it is not a starter in the modern sense, i.e., a little auxiliary machine to start and then be cut out, but one to share the load with the main machine, take oonsider.able 15 current and Slhare the supply voltage. It follows from this that it cannot be cut out without ri~sk, it WaiS not intended to be cut out, and no cutting-out operation is described. Tesla·'s arrangement does not and cannot sta.rt from re'st when in series. Tesla only begins to Ulse a series arrangement a.fter what he describes as the .starting period is finished. [Lord DUNEDIN.- Does his starting period 20 end with synchronism or not n Tesla says, get up to speed and then switch on the current, he is only oonsidiering speed. Tesla w.as not conoerned with modern constant voltage mains at all, but with a sy.Sltem which has gone into limbo, viz. a const,ant-current system. [Lord DUNEDIN.- You must keep this in view. These things that you have been telling us are not set out as being a. b. c. in 25 Rosenberg's Specification, they have to be explained by a person who under• stands various things about electriciity. I do not complain about that, because specifica,tions are not made. to be read by Judges, but by people skilled in the ad at the time of the patent, and I ,am assuming that all these tihings might have been plain to an electrician iln 1911; but, on the other hand, it seems to a 30 certain extent a ·ca,se of empiricism. You obviously have to have it so pl'O~ portioned that you will get Rosenbe'rg's thing to work.] Ye·s. [That is a double• edged weapon, because it .can be turned against yourseU. As against that, we have not got, in dealing witih Tesla, to deal with whetiher a common workman or a Judge would understand it; you have to deal with the :practised electrician, 35 and, if he, by empiricism, could reach the same result WIth Tesla's machine, then you are hit by the whol,e 0'£ the cases.] You are re.ading Rosenberg's Specification, not only with the knowledge of 1911, but in the light of Rosenberg's discovery which he discloses in his Specification. He tells you what he is doing in quite plain language, but it is quite a different thing to say that Tesla, 4.() without Rosenberg's idea, would convey anything. [Lordi BLANESBURGH.-!s not the constructiive notice which Rosenberg had of Tesla, constructive notice of Tesla in 19121 So tihat that document, if read by him in 1912, would convey to him that which you say Rosenberg conveyed to the world n Although you have to take Tesla with common knowledg,e of 1912, you certainly have not got 45 to take Tesla in: re.lation to Rosenberg's problem, because the presentation of a suggested solution is part of the invention. [Lord DUNEDIN.-Suppose an electrician in 1911 knowing the difficultie's was saying to hims.elf, wha.t can I do 1 I ihave puzzled my brains, and then finding Tesla says: Here is exactly the thiing I want. W ouldl not that prevent Rosenberg n No. [Lord DUNEDIN.- 50 Surely that is exactly King, Brown &- Co. v. Anglo-American B1'ush Corpora• tion,] In that case it was agreed by counsel ·Jor the Plaintiff that the exact 12 No. 1.J REPORTS OF PATENT, DESIGN, AND TRADE MARK OASES. [Vol. XLV. British Thomson-Houston Co. Ld. v. Metropolitan-Vickers Electrical Co. Ld. thing that was claimed had been described in the earlier document. [Lord DUNEDIN.-On thi!s question of pai'ring, it is quite true Tesla does not mention pairing, but it oomes to this, that the thing will not work, as you wish it to work, unless the machines are properly paired. Why would Tesla say: my thing win not work as I mean it to work unless they are properly paired 1] Because :; Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 he hrus not in view the purpose and did not know the principle which would tell you how to pair, and Rosenberg has disclosed that. [Lord BLANESBURGH.• Does it help you to that oonclusion that there is a statement in Tesla that it may be prefer,able to have the synchronous machi!ne the, larger of the two n Yes, the other would be untlhinkable in Rosenberg. [On the limitation of the 10 claim British Thomson-Houston Co., Ld., v. Corona Lamp Works, Ltd. (1922), 39 R.P ..o. 49 was referred to, and on the question of anticipation the following cases were referred to, British Ore Concentration Syndicate, La., v. Minerals Separation, Ld. (1909) 26 R.P.O. 147, Otto v. Linford (1881) 46 L.T.N.S. 37, Plour Oxidising Co., Ld. v. Carr &; Co., Ltd. (1908) 25 R.P.O. 428, and King, Brown 15 & Co. v. Anglo-American Brush Corporation (1892) 9 R.P.O. 313.] Whitehead K. O. followed for the Respondents.-The two main attacks in this case are that Rosenberg's Patent is bad b2cause of anticipation and lack of subject-matt,cr. It is said no matter whether Tesla understood what he was doing or not, if his ,arrangement of apparatus were made subsequently to Rosen- 20 berg's Patent it would infringe Olaim 1 and the claim is invalid. It is a mix,ed question of fact and law, as to whether any figure of Tesla would infringe Rosenberg, but even if it did, it would not follow in law that Rosenberg was necessarily invalidated. There are three divisions of Tesla's Specification, figure 4 showing pony motor starting, figures 6 and 7 showing par,allel arrange- 25 ments and figures 5, 8 and 9. In the first two divisions there is no possibility of getting series connection and he says the manner of operating all his arrange• ments will be understood from what he has described in relation to figure 4. Looking at the differences and simiIarities between Tesla figure 5 and Rosen• berg, Tesla has no direct current ,excitation whilst Rosenberg has, the result is 30 that there is no generated back E.M.F. in Tesla to cause the transfer of voltage at synchronism, and there are no fixed magnet poles to do the lOCKing in and give the firm locking in of Rosenberg as compared with the tentative locking in which one gets in Tesla. An engineer reading Tesla finds a document not directed to the problem of getting over the disadvantages of pony motor and 35 tap starting, but one directed to the speci.al problem relating to the special motor. He finds one method of operating the switches described, not four, and a method in which series is never obtained. If he goes to figure 5 and tries it, he may switch into series before or after synchronous speed. In either event he may get some noise, but the,re is nothing to suggest Rosenberg's advantages, 40 why should an engineer select that figure to solve Rosenberg's problem 7 The formulation of the invention would have to come first to enable him to make the selection. Synchronous motorls a;nd rotary oonverters existed for twenty years after Tesla and yet nobody in fact made Rosenberg's invention. One is not to consider a document whioh has been deposited at the. Pat,ent Office for 45 twenty years in the light of the later knowledge. That would mean that a document which was hidden away in that way was constantly growing in its power to destroy other people's inventions. [On the question whether a prior patent which describes something which would be an infringement, if made subsequently to the patent in suit, is an anticipation the following cases 50 were referred to Pneumatic Tyre Co. Ltd. v. East London Rubber Co. (1897) Vol. XLV.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [No.1. British Thomson-Houston Vo. Ld. v. Metropolitan-Vickers Electrical Co. Ld. 14 R.P.C. 77; Daw v. Eley (1867) L.R. 3 Eq. 496; Murray v. Clayton (1872) L.R. 7 Ch. 585 and Re Brown's Patent (1908) 25 R.P.C. 108.] On the question of subject-matter this case is exactly similar to Armstrong Whitworth &; 00. Ltd. v. Hardcastle (1925) 42 R.P.C. 543. [Lord DUNEDIN :-It is not subject-matter 5 in the proper sense of the word, it is not that the thing had been discovered Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 before, but that it is not r,eally in itself properly patented.] Yes. There is no doubt that .automatic synchronisation in one step was new at the date of Rosenberg, and in view of that, the questioOn of subject-matter does not really arise. 10 Sir A. Cole/ax K.C. replied.-The Applicants cruse is that Tesla has some,thing which is included without qualification in Rosenberg's maim. One cannot have invention for adding common knowledge to publication and one must read Tesla in the light of common knowledge existing at the date of Rosenberg. On the question of subject-matter, there could be noO invention in applying Tesla to a. If> larger machine or to a polyphase machine as compared with a single phase· machine. [Lord BLANESBURGH-SUppose, when you look at the prior publicatioOn,. you find the author had not in his mind at all this particular method oOf doing Wlhat Rosenberg utimately achieved, are you entitled as .against Rosenberg to. read that perfectly disconnected document and add the co-related prior publica.- 20 tion to oommon knowledge ~]. Supposing Rosenberg had drawn a claim to a methoOd of operation and Tesla could in fact be used without arriving at or following the method of operation claimed, then public common knowledge would not be an anticipa,tion of Rosenberg. I am not s'l.ying Tesla describes the matter from the standpoint of an operation, he describes it as an arrange- 25 ment. [Lord DUNEDIN.-In the ]{ing Brown case neither plaintiff nor defendant knew what the advantage of the compound winding would be, that only came to light when you got the modern lighting system. The whole point was whether the compound winding was disclosed or not. If the whole question here was simply putting a pony machine in series with another machine, there 30 would be an end of it, but the question is, suppoEli:ng the disclosure had been simply to put a pony machine and another in series, would you necessarily get the result tha,t you do in R08enberg, indeed yoOU would not.] I am sub• mitting that Rosenberg has done no more than. your Lordship has said, with the one qualification that the curr,ent passed by the starting motor must be 35 sufficient to enable the synchronous machine to get into synchronism. There are no oOther limitations, tiliere is no upper limit in Rosenberg, because on the Specification you can have a synchronous machine which oould be put str,aight on to the line and therefoOre could not be damaged however much current the starting motor allowed to pass. Rosenberg expressly includes a dead machine 40 and the point about direct current excitation has nothing to do with the inven• tioOn. So far as taking direct current and sending it through the coils of a rotary conv,erter is concerned, that is doOne after the machi!ne is in synchronism. In some cases Rosenberg has his field circuit open during starting, that is what I call a de·ad motor. There is nothing in Rosenberg's Specification to exclude 45 any type of machine. Rosenberg's whole invention is oontained in the specifica• tion at p. 3 1. 50 to p. 4 1. 5, and: one is not to read the claim as limited to such designs as give some particular advantages. [Lord DUNEDIN.-I cavil at the word" limitations". We have to see what the Cla.im includes. There are I . tw.oexpressions in the Claim which seem to prevent us from taking the simple 50' broad view, they are" arrangement "and" fo:t: the·purpose of". They send UlS back to the Specification to see what the claim is.] One might take any 14 No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [Vol. XLV. British Thomson-Houston Va. Ld. v. Metropolitan-Vickers Electrical Co. Ld. starting motor one desired. The whole point of this invention is merely in having the series connection between the two machines to enable automatic synchronisation to take place. It is clear that Rosenberg includes in synchronous dynamo electric machines any synchronous motor or rotary converter and lie includes any starting motor. It is left to anyone to follow his desires as regards a Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 what he takes and ther,e is nothing aJbout direct current excitation being essential in his document. Rosenberg's Claim is drawn absolutely gener,ally to the linking together of a starting motor and a synchronous motor by series connection to attain the elimination of the synchronising step previously attendant when a starting motor was used. It is not a question of when the 10 series connection is made or of pairing. .Sir Duncan Kerl1l in construing the Claim said it applied only to such motors as had been st8lrted by pony motor and lamps or by tap starting; that omits the maohine, which could be put direct on to the mains, which Rosenberg clearly includes. Next he says it must be started on modern supply mains without danger of a rush of current. There 15 is nothing about that at aU in the document. He says his construction imports four things. First, fixed magnets and a dir<60t ourrent field, that is untrue, one may have the magnetism induoed. Seoond, a starter which when running near synchronous speed will pass suffioient ,current to synchronise hut will not pass dangerous rushes, but when one has the starting motor in series 20 one has got your shield no matter what its size may be. Thirdly, he says it involves a starting motor which absorbs no appreciable voltage when synchronism is reached so that it can be cut out witliout shock to the synohronous maohine. So far as transference of volts is ooncerned, exactly the same thing happens in Tesla, in f8lCt, if one imagines a larger starting motor in Tesla's case than 25 in Rosenberg's, one will have a bigger transf,erence of volts on the synchronous maohine going into synohronism. Fourihly, it is said Rosenberg starts from rest. That premise is entir,ely wrong and excludes a case which Rosenberg has contemplated. Reasons have he en given why Tesla is not within Rosenberg. It is said Te&la does not describe a modern maohine whioh could be started 3') by pony and tap starting and has no danger of a rush of current. There is no evidence to support that, and it is founded on Tesla having no direct current excitation before synchronism, but neither has Rosenberg. It is said Te&la does not describe a starter which solves Rosenberg's problem, but if one has starter and synchronous m8lChine in series nothing mOI'e is required, and as 35 regards the size of the starter there is no restriction in Rosenberg, and there is no evidenoe that one could not cut Tesla's starter out· after synchronism without risk. It is further said that Tesla only begins to use the series connec• tion after what he describes as t.he starting period is finished, but in figure 5 of Tesla the synchronous motor cannot be energised at all except through the 40 starting motor. Again on the question whether Tesla is automatic or requires two switching operations, it is true the starting motor has first to be connected to the mains and then the series connection established, but, in the cases where Rosenberg employs a reversing switch, lie equally has two switching operations, 1'10 that that oannot be of the essence of the invention. Lastly it is said that 45- Tesla was not dealing with modern constant voltage mains. It is true that most of his figures refer to constant current systems, but nobody has ever Buggested, nor is it the case that one oannot use figure 9 with either system. The Appellant's case here is that there is complete anticipation, and it does not matter what Tesla's knowledge was or what his intention was, if you find in 50 his document that which is claimed in Rosenberg. The last thing is infringe- 15 Vol. XLV.] REPORTS OF PATENT, DESIGN, Al'."'D TRADE MARK CASES. [No. 1. British Thomson-Houston '00. Ld. v. Metropolitan-Vickers Electrical Co. Ld. ment. [Lord DUNEDIN.-If we were with you on validity, there would be no need to go into infringement. Their Lordships have decided, without giving any opinion, to deal with the main point, and then, if they consider the Patent :> is good, to have a speech a side on infringement.] Further argument was heard on the 25th of July, 1927. Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 [Lord DUNEDIN.-In your argument yO'll will assume that the Judgment of the Oourt of Appeal is right.] Sir Arthttr Cole/ax K.O.-There i,s no conflict on the evidence as to infringe• ment. The Defendants' machine is so designed that for practical purposes yO'll 10 cannot start these machines without availing yourself of the choke coils. The Respondents' experts did, on one or two occasions, succeed in getting the synchronous machine into synchronism without using the choke coils, but they admitted that it could not be done safely as a day to day operation. The starting motor does not pass sufficient current to enable the synchronous 15 machine to synchronise with certainty, and the time of the effort to get into synchronism is so long that the starting motor gets hot and smokes. [Lord DUNEDIN.-I suppose there is question that this machine could be started with the choke coils only i] No. [Lord DUNEDIN.-SUppose you have a some• what improperly paired Rosenberg and you put that right by the choke coils, 20 does that take you out of infringement n The Appellants do not affect both speeding up and synchronising in one operation without any further manual operation, they have to manipulate the choke coil switch. [Lord DUNEDIN.-If you took away YO'Ilr series connection altogether, your machine would not work.] [Lord BLANESBURGH.-Does it not come to this that the starting motor and 25 choke coils are the mechanical equivalent of a larger starting motor 1] Whitehead K.O.-There is no doubt that the Appellants' maohine can be synchronised without the choke coils, though that may be too uncertain to do as a day to day No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [V 01. XLV. British Thomson-Houston Co. Ld. v. Metropolitan-Vickers Electrical Co. Ld. The Oourt of Appeal agreed as to in:flringement but disagreed as to anticipa• tion. They, therefore, reversed the judgment of the trial Judge, granted: an injunction against infringement and ordered an inquiry as to damages. Appeal from that judgment has been taken to your Lordships' House. The case has been argued at great length and with great care. ;) Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 The Patent has to dio with electrical machines known by the name of Synchronous Dynamo Electric mooliines. The moohines are made either as motors, i.e., as a machine to provide mechani·cal power, or as rotary con• verters, i.e., as a machin!\ whioh will receive an alternating current from an external source and will deliver it in the form of a direct current. Though 10 there are certain differences of arrangement acoording as the moohine is designed for the one purpose or the other, there is no essential difference in respect of the matters which are of moment in the present case, and they are both, in ordinary phraseology, included in the term synohronous dynamo electric machine. In both cases the moohine is energised by an electrical If> supply of alternating current provided from elsewhere, in modern times nearly always the mains o£ an electrical distributing authority, hut the supply might be given by any private generator. My Lords, the suhject to he handled is very technical andi very difficult of comprehension, because the phenomena which have to be considered are not 20 such as can ibe appreciated by the eye and are by no means easy to grasp by the mind. In essaying, therefore, to describe the machine in question, no person, who is not himself a scientific man skilled in this particular brancli of knowledge can undertake the tapk of descriptiQn without misgiving, and he cannot hope to be immune from criticism whatever words he may use. 25- Such has been the fate of both the trial Judge and the learned Judge who framed the judgment of the Oourt of Appeal. I am far from thinking that I shall have complete success where they have partially failed. None the less the question to be determined is a questi'On of law, and it is impossible to approaoh the question of law! without setting forth as hest one may the nature 30 of the maohines with which the Patents have to do. lt may be as well to begin with a statement of the cardinal properties on which all such machines depend and as to which there is no oontroversy. If the two poles of a magnet are a,pproached towards each other, the intervening space between them is called a magnetic field or polar field. If a conducting 35 loop of wire is mQved in a direction transv,erse to the conducting wire through the magnetic field, the resulting action is that a current of electricity is set up in the direction of the length of the loop, the direction 'Of that current depending upon whether it is passed through the, north or south polar field. That is to say, the direction depends upon the direction in which the loop is 40 moved relatively to .the north and south poles of the magnets which form the magnetic fields in which the loop is moved. Further, when current in a wire goes round a soft iron 'har it, for the time, makes the bar a rna,gnat, making one pole north and the other south, according to the direction in which the current traverses. Further, as the current in the wire creates a magnet, so 4f> magnetisation 'Of the bar creates a current. Thus, if you have a loop of wire and twist it round on two pivots in a magnetic field, a current will be set up along the upper limb, down the descending limb and book along thE.', lower limb to the end. That is the simplest form. If the motion which causes the wire to rotate is provided from an external source, suoh a's, e.g., a steam engine, 50- the machine will be a dynamo. But the prooess may be reversed. The current may be supplied to the wire from an external source and then rotary motion 17 Vol. XLV; 1 REPORTS OF PATENT, DESIGN, AND TRADEl M4Jl.K; ..eASElS. [No. 1. British Thomson-Houston Co. Ld. v. Metropolitan-Vic.kers Electrical Co. Ld. will ensue and the machine will then be called a mator. Also, it is all one whether you move the wire thr'Ough the magnetic field or .whether you turn the magnetic field round the wire. All that is necessary' is that the wire shall cut the lines of magnetic force. . . . 5 So. far all is comparatively simple. I have not· been ruble to" take what I Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 have so far said from the testimony o.f witnesses in this" case; as a co.urse was taken which may be co.nvenient at the time but is scarcely so if the case goes further. Sir Duncan Kerly made a speech to the learned trial Judge setting forth general princlples. lie had his principal witness, Dr. Eccles, in Court, 10 and, having satisfied himself that that gentleman ,had heard what had been said, he put a couple of questions tantam'Ount to the cateohismal query, "All this dost thou steadfastly believe 1 " and having received an .a.ffirmat~ve answer wa.s satisfied. But, as I would sooner be convicted of plagiarism than 'Of in• accuracy, I may say that my description is nearly textually taken from the 15 evidence of Mr. Imray, a distinguished engineer, as it was accepted by the Court and is reported in the case 'Of King Brown &; Co. v. Anglo-American Brush Corporation, 17 R. 1267,* to which further referep~, will fall to be made. Now, however, we enter the realm of complicati'On. Hithert'O reference has 20 been made to a simple motor; now we come to the machine with which we have directly to deal, namely, the synchron'Ous motor. The synehrQhous motor con• sists of an armature mounted on a shaft and capable of ·rotation. This is termed a rotor. It rQtates within the encircling embrace of a stationary part, which is called a stator. The machine may be energised either through the 25 rotor Qr the stator, but for simplicity of description I shall assume . that the energisation is to be effected through the rotor. I shall also assume that the machine to be described is a rotary converter, that being the type which, in this case, is embodied in the infringement. The machine will then have magnetic poles on the stator which may be two or more. Now the machine will be running 30 in synchronous speed when the time occupied by the passage of a fixed point on the rotor from the north pole on the sta,tor to. the north pole again, in the case of a tWO-Role machine, or from one north pole to the next' nQrth pole if there are more than two poles, exactly equals Qne complete alternation of the supply current. That is to say, taking the 'Ordinary Il'equericy' of fifty cycles per 35 second, a two-pole machine would have to run at 3,000 revolutions per minute, a four-pole machine at 1,500 revolutions per minute to be in synchronous speed. Synchronism, however, cannot be effected by the mere existence 'Of synchron'Ous speed, and here I must pause for further explanation. First, as to the expression" one complete alternation of the supply current," 40 let me revert to the loop of wire. Supposing a single loop to be a.t rest. It is then not cutting the lines 'Of force of the magnetic field andn'Othing will happen. As it begins to move and cuts the lines, the current will increase up to its maximum, which will be attained at 000 from the point of start. It will then decrease till it comes to the neutral position. It will then have described half 45 a revolution; when the other half-revolution i's begun the same thing will happen but the current will be in the opposite direction. That is a single-phase alternat• ing current. But now if, instead 'Of one loop, you have more loops than one set at a different angle on the axis of rotation, you then have. each of the loops following each other and giving rise to the same phenomena. If there are three, * 9 R P.C., 1lH!. B 18 NQ. 1.] REPQRTS OF PATENT, DESIGN, AND TRADE :MARK CASES. [VQl. XLV. British Thomson-Houston "00. Ld. v. Metropolita1lrVickers Electrical Co. Ld. that WQuid be a three-phase alternating current; in Qther wQrds, a three-phase current cQnsists Qf three single-phase currents, each of which passes through its zerQ value Qne-third Qf a periQd after the Qther. What I have been describing as loops Qf wire are in the machine designated Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 by the name of armature, which is mQunted Qn the rQtQr and is wQund rQund 5 an irQn CQre. Now if an electric current is passed thrQugh the CQils fQrming the armature, the CQils behave as if they were magnets, lines Qf fQrce passing frQm the ends SQ that Qne end Qf the wire becQmes the north and the 'Other the south pOole. If thedirecti'On Qf the current is reversed the P'Olarity Qf the ends is reversed; such a coil is called an electr'O magnet.. N ext reverting tOo the 10 three-phase current, if a ring comm'Only called a gramme ring, wQund with a C'Oil rQund the circumference, which has a tapping at each 'Of three segments, is fixed in space and at each tapping a vQltage is supplied SQ that a three-phase current is prQduced, the PQint in the ring which is where the wire by which the current is entering becQmes a SQuth P'Ole, and the PQint diametrically 15 QPposite tOo it 'On the ring is a nQrth pOole. Since in a three-phase system the current in each of the supply wires attains its maximum in turn Qne-third 'Of a periQd behind the other, the SQuth pOole will mQve prQgressively rQund the ring and will be mQved completely rQund the ring when the ourrent pr'Oducing it has passed thr'Ough Qne cQmplete cycle. This is called a r'Otating magnetic 20 field and will be the result 'Of m'Ounting the armature in the way described as a gramme ring. NQW these rQtating PQles are mQving in space relatively tOo the ,armature nQ matter whether the armature is stationary Qr mQving, but Qnce it is m'Oving the positiQn Qf the pOole in space will be effected thereby. If the mQtiQn is in the same directiQn as they ar·e gQing, the mQtion will be 25 accelerated; if in the QPPQsite directiQn, they can be sl'Owed dQwn and can be br'Ought tOo rest, 'Or nearly SQ. This is a sQmewhat difficult c'OnceptiDn-at least I have f'Ound it SQ-t'O realise, and may perhaps be facilitated by an anal'Ogy. Take a mQving staircase, such as is familiar tOo the users Qf the Tube Railways. Let a passenger Qn the mQving staircase represent the mQving magnetic field; 30 his PQsitiQn in space is shQwn by the· relati'On he bears tOo the walls Qf the building. The mQving staircase represents the armature. N QW if the passenger will use the staircasll in the reverse way that it is used in practice, viz. try tOo ascend a descending staircase, and will make his pace the same as the pace 'Of the staircase, it is evident that, th'Ough his 'Own mQtiQn fQrward cQntinues, his 35 PQsitiQn as regards the walls will never be altered. It is true that the pace 'Of the staircase is ODnstant while that 'Of the passenger is variahle, but the result would be, the same if y'OU reversed these attributes. I nQW revert tOo the machine. If the pDles are at rest Qr nearly SQ, they can be held in pDsiti'On in space 40 hy the attractiQn, 'Of anDther magnet, and there they will stay thDUgh the armature mDves Qn. This is what happens. Being hrDught tOo rest Dr nearly so by the mQtiQn 'Of the armature in the contr,ary directiDn tOo the processiDn of the pDles, they can he seized and held by the magnets 'On the statDr and the armature will cDntinue tD revDlve, but the pDles will Qnly seize each Qther when 45 the current which excites them is in step with the incDming oorrent and the machine-generated current has the phases at the same time as the incoming current. Given all these conditions perfect synchronisation ensues. 19 Vol. XLV.] REPDRTS .oF PATENT, DESIGN, AND TRADE MARK CAsEs. [No. 1. British Thomson-Ho'U8ton -Co. Ld. v. Metropolita'TlrVickers Electrical Co. Ld. I now turn to Rosenberg's Patent. To a great extent it speaks for itself. I quote the initial part of the Specification: "This invention relates to syn• " chronous dynamo electric machines and has for its object to provide improved " arrangements fDr sta.rting the same into operation. The methDds heretDfore :> commonly adDpted for starting synchronous dynamQ electric machines such as Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 " synchrDnous mDtors and rotary converters, consist in using either a starting "motDr or in cDnnecting the synchronous machine to the mains either directly " or through, a reducing transformer and permitting it to start itself. The pole " pieces of the machine are in the latter case usually fitted with a damper and 10 "the machine will start up in similar manner to a squirrel cage induction "motor, and, being near the synchronous speed, will pull into step. The first .. method has tihe disadvantage that after. the synchronous macihine has attained "the desired speed it must be synchronised, an operation which may take some "time and skill on the part of the operator, and the latter method, while 15 "possessing the advantage that the synchronisation is not required, has the " disadvantage that a large current is taken from the mains during part of the "starting period. Furthermore, when this method is employed with rotary " converters the brushes are apt to spark viDlently during the starting period " because a oDnsiderable voltage exists on the armature, an appreciable part oX 20 "which is shor,t circuited by each brush. To avoid this difficulty it has .been " proposed to lift the brushes during the starting period. This, however, entails "an undesirable mechanical complication. Another objection to the use .of "this method with rotary converters is that the large alternating current " passing into the armature may demagnetise the field so that when the machine 25 "is brought into synchronism the polarity may be reversed,this necessitating "the use of pole changing switches. According to the present invention a " motor is employed for starti.ng the synchronous machine, but the disadvantage " hereinabove mentioned is avoided by electrically connecting the motor wind• " ing with the armature of the synchronous machine by which means when the 30 "ma.chine has attained the desired speed, it will be aJready in synchronism, " thus avoiding a special synchronising operation. The starting motor may be " either a squirrel cage motor 'Or a slip ring motor and it may have, as is usual, " a smaller DlUmber of poles than the synchronous mllichine, in which case the " secondary circuit should have an appreciable resistance, or it may have the 35 "same number .of poles as the synchronous machine, in which case the resistance "in the secondary circuit should be made small. Also a commutator motor " fitted with any number of poles may be, used as starting motor. The pha,ses of " the primary winding of the starting motor are separated and one termina.l of " each phase winding is connected to the supply mains and the other termmal 40 "to a terminal of the synchronous mllichine or in the case of a rotary conver~er "tD a oDllector ring. With the above arrangement the synchronous machme " may be started with a much smaller current than would be required if it were "itself connected direct ,to the supply mains. The voltage impressed D.n its "terminals Dr on the collector rings in the case of a rotaxy converter WIll be 45 "very small during the starting period and no sparking will occur at the com• " mutator. By suitable design of the windings or 'the starting motor the "current flowing into the armature of the rotary converter can be kept so " small that it will have no appreciable demagnetising effect on the field, and ".the residual magnetism of the rotary converter remains unaffected, so that 50 "the rotary can excite itself r'eadily to the proper polarity. The field winding No. 1.] REPORTS· OF PATENT, DESIGN, AND TRADE :MARK CASEB. [V01. XLV. British Thomson-Houston Co. Ld. v. Metropolitan-Vickers Electrical Co.- Ld. " of the rotary may retain its normal oonnection and the field rheostat be kept " in its normal working position. If ,the ma.chine is going through synchronism, " or is in synchronism, the excitation of the rota.ry converter then ensuing will " cause the slip ring voltage to be near1y equal to the supply voltage, and the " stator windings of the starting motor can then be short circuited either in a 5 Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 " single step or gradually by means 'Of resistances or choke coils or tappings in "the winding of the starting motor." Appropriate drawings accompanied this description. The first thing that is abundantly clear is that the avowed object of the Patent is to provide an automatic means of attaining synchronism so that during the period nothing 10 . else will require to be done to allow, when synchronism is attained, the start;ing motor to be put out of action and! to avoid the disadvantage which had been found to ensue if the full current was turned on to the synchronous motor at once. The arrangement having a starting motor mounted on the same shaft, or 15 mechanically moving the s·8ime shaft as the shaft of the synchronous motor, is treated as a well known device. By the time of this Patent, synchronous motors were ordinarily large machines" and were gradually energised by polyphase alternating currents supplied by means of some electrical supply. Machines constructed according to the design of the Patent were found to be quite 20 successful. The most graphic representa,tion 'Of their a.ction was shown by an oscil• logr,am which was produced in the case and which shows very clearly the gradual transference of voltage which occurs when the two machines are, as the Patent directs, connected in' series. In other words, the promise contained in the words of the Specification is shown to be effectively kept. 25 The difficulties indicated by the Specification had not, in practice, been obviated till this Patent apperured. Taking first, as is convenient, the question of anticipation" the sole question is, whether 'the admittedly useful device disclosed in the Patent was anticipated by Tesla's Patent. Now Tefla.'s Patent must be primarily considered in the light of the practice and knowledge of Tesla's time. 30 I say primarily; there was a good deal of dliscussion about the date at which knowledge must be considered. My view is this: the knowledge which may be ascribed to a person who wished to grapple with the problem which Rosenberg so1VedTsthek~iiwledge at the date of the eve of Rosenberg's Patent. But it must not incEiae'~what Ro.~enberg disclosed. None the less I repeat that Tesla's Patent S5 must primarily be considered in the light of the knowledge of that time, because the knowledge that alone w,as in Tesla'.s possession and the problem of his day would be the only knowledge that would explain his Patent and the only problem with which he w,as dealing. . Now at the date of Tesla's Patent it is proved that the machines in use were 40 much smaller ; that they were, as a rule, two-pole machines, and that the supply available was single-phase current. I now quote the initi!al part of Tesla's Specification: "As is well known, certain forms of alternating-current machines "have the property, when connected in circuit with an Itlterna.ting-current "generator, of running as a motor in synchronism therewith; but while the 45 ",alternating current will run the motor after it has attained a rate of speed "synchronous with that of the generator it will not start it. Hence in all "instances heretofore when these' synchronising motors,' as they are termed, "have been run, some means have been adopted to hring the motors up to "synchronism with the generator, or approximately so, before the alternating 50 21 Vol. XLV.] REPDRTS OF PATENT, DESIGN, AND TRADE MARK OASES. [No. L British Thomson-Houston Do. Ld. v. Metr'Opolitan-Vickers Electrical Co. Ld. " current Df the generator is applied to. drive them. In an application, filed " February 18th, 1889, Serial No.. 300,220, I have shDwn and d\escribed an im• "prDved system Df Dperating this class of motors, which consists, broadly, in "winding or arranging the motor in such manner that by means of suitable 5 "switches it could be started as a multiple-circuit motor, or one operating by a Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 "progression of its magnetic poles, and then, when up to speed, or nearly "so, cDnverted into an ordinary synchronising motor, or one in wihioh "the magnetic poles were simply alternated. In some cases, as when "a large motor is used and when the number of alternatiDns iis very high, 10 "there is more or less difficulty in bringing the motor to speed as a" double or "multiple-circuit motor for the plan of construction which renders the motor " best adapted to run as a synchronising motor impairs its efficiency as a torque " or double circuit motor under the assumed conditions on the start. This will "be readily understood, for in a large synchronising motor the length of the 15 "magnetic circuit of the polar projections ,and their mass are so great that " apparently considerable time is required for magnetisation and deIDagnetisa• "tion. Hence with a current of a very high number of alternations the motor "may not respond properly. To avoid this objection and 0 start up a syn- " chronising motor in which these conditions abtain is the object of my present 20 "invention. I have therefore combined two motors, one a synchronising motor, "the other a multiple-circuit or torque motor, and by the latter I bring the " first-named up to speed, and then either throw the whole current into the syn• " chronising motor or operate jointly both of the motors." Now here again the Specification largely speaks for itself. The only problem 25 he was dealing with was the difficulty of starting. Once given starting, the attainment of synchronism did not trouble him. The reaSDn was, aooording to the testimony of all the witnesses, that with the smaller machines of his day, with a single-phase current and a, two-pole machine, and with, ordinarily speak• ing, a current which was a, constant current, but had not a constant voltage, the 30 machine, if synchronous speed, or nearly synchronous speed, was attained, would, as the witness,es put it, " worry itself into synchronism." It had not the difficulty of the complex rDtary field. If, therefore, the matter stopped thar'e, there would be no difficulty, but the difficulty arises from two. other circumstances-the first Tesla's drawings, and the second Rosenberg' 8 3 ~ d Claim. In Tesla's maste'r dr,awings he shows something quite dif£'erent from Rosenberg's method, that is to say, he shows a motor energised through the stator and not through the rotor. He never dealt with the question of how to get into synchronism. He assumed all along that would fDHow on synchronous speed or its approximation. But in a series of sketoh-dra,wings he indicated 40 different ways in which his two motors, the torque motor and the synchronous mDtor, might be arranged, and in tliree '0:11 them he showed the connection between the motors in series and not, as in the others, in parallel, and in one of these he indicated a set Df switches which would have allowae] of the torque motor, after it had attained its work in starting, being short-circuited. 45 The motive of this is not far to. seek; It is disclosed in line 57: "I have there• " fore combined two motors, one a synchronising motor, the other a multiple " circuit or torque motor, and by the latter I bring the first named up to speed "and then either throw the whole current into the synchronising motor or " operate jointly both of tlie motors." .. 50 Now, take along with this Rosenberg's Olaim, which is as follows: , " (1) " Arrangement for starting :synchronous dynamo electric machines by means of 22 No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [Vol. XLV. British Thomson-Houston Co. Ld. v.Metropolitan-Vickers Electrical Co. Ld. " an electric motor in whieh a series, or electrically equivalent oonnection, is "provided between the windings of the starting motor and the synchronous "machine, for the purpose ·of effecting i~ one operation both the speeding up " and the synchronising of the synchronous maohine with the supply current." The first legal question that therefore arises is, what is the proper construction 5 Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 of that Olaim 1 If its true construction is that, Rosenberg having discovered that the connection in series solved the problem with whieh he waH grappling, and being ignorant, as he well might be, of Tesla's Patent-for no one says that a single machine was ever made or wor,ked in accordance wi!th Tesla's Patent, it slumbered undisturbed in the Pa.tent Office-he claimed every arrangement 10 where two machines are put in series, he is then anticipa.ted. To take such a view would be a very easy way to dispose of a difficult case, but I do not think it would he fair to the Patentee. I think his Olaim was not such a claim, but was a claim for the particular arrangements he had described in his Specification and in his drawings, and the arrangements, 15 when analysed, sh9w considerably more than the mere series ()onnection, though no doulbt it is the serie.s connection which is the master move which leads to success. You can get from the Specification and the drawings the idea that the two motors must be properly paired, so that in his own words, "By suitable " design of the windings of the starting motor, the current flowing into the 20 " armature of the rotary converter can be kept so small that it will have no " appreciable de-magnetising effect on the field and the residual magnetism of "the rotary converter r·emains unaffected so that the rotary can excite itself " readily to the proper polarity." You can also get the idea of taking a· direct ·current firom the machine to 25 magnetise the poles on the stator which ensures that the current which magnetises them produces in the rotor a baek electromotive force which has the same phase as the current wnich is energising the armature and creating the rotary field. It is true that, if you do these things, the successful synchronism and the transference of voltage which allows of the short-circuiting of the torque 30 motor are an automatic consequence, and that he does not clearly set forth these advantages but is content with saying that synchronism will inevitably be obtained. And further you necessarily get the idea of the shielding effect of the torque motor which prevents too much current at the first coming to the synchronous motor. 35 Now that being my view of the Olaim, I turn to Tesla, and what I have to ask myself is this-Would a man who was grappling with Rosenberg's pr,dblem, without having seen Rosenbe;rg's Patent, and who had Tesla's Specification in his hand, have sa.id: "That gives me what I wish" ') I do not think he would. I do not think it would have oceurred,to.him that Tel}Za had actuallysoly~q a 40 problem which was not before him by.:opeof his .. .arrangements used in a particular way-for that must be dO~f" theswitcl!es must be .operated in a certain procession-in a machine which--wag. ..intended-tQ ..s..olv~~r:t0ther proolem altogether. . I do not say that I have come to this result without much thought 45 and difficulty. The case is a very intricate one, and I am certa.inly oppressed by my neeessarily imperfect knowledge as to electrical phenomena, but, as regards the law, I have no doubt how to expI'ess the puzzle whiich has to be solved-it may be expressed thus. Does this fall witliin the application of the law as shown in King Brown v. Anglo-American Brush Co., or within the 50 application of the law in the cases of Hill v. Evans, Otto v. Linford, and FloUt/" 23 Vol. XLV.] REPORTS OF PATENT, DESIGN, AND TRADE MARK OASES. [No. 1. Briti8h Thomson-Houston Co. Ld. v. Metropolitarv-Vicker8 Electrical Co. Ld. Oxidizing Company v. Carr &: Co. 1 I propose, therefore, to examine very closely what these cases decide. lJllJ.i!!:!ljJ.rown'8 .case" L.R. (1892) A.O .. 367,* the Brush Co"'!pany held a patent which claimed cOIIIlpound winding. Now the problem whICh cOlIIlpound 5 windling solved was this: At first dynamos were made by the magnetic field Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 being supplied by permanent magnets. Next came the substitution of electro magnets for permanent magnets, the current of the wire encircling the bar to be magnetised being supp-lied by a battery. It then suggested itself that the current might be supplied by the machine itself. The first arrangement was what was 10 known as series winding, the wire was taken froOm the brush of the armature to the magnets and then on to the external circuit whioh did the work, and then back to the armature. The disadvantage of this was that, if the external circuit were broken, or, as it is tel"IIled, opened, then the magnetisation of the magnets ceased. The next idea was called shunt windiing; the wire now was 15 bifurcated; one wire went to the magnets, the other to the circuit. This got over the first difficulty, as there was alw.ays ma.gnetisation, but there was this great disadvantage, that the current was not constant in strength or, as ~t is expressed, the potential was not constant. For the greater the resistance in the circuit which did the work, the less current it would get, because more would 20 then goO to the magnets. Now 'came the new device, called compound winding. This was simply to put the oOther two together. The wire was bifurcated as before, but now both the wires went round the magnets, and the wire to the circuit, i.e., the series wire, was made of a less resistance than the shunt wire. This had the shunt advantage of Illever losing 25 magnetisatioOn. It also had the compensating effect which led to constancy, for if, owing to loOad, the series wire offe·red greater resistan.ce and more of the current preferentially went to the shunt, the magnetisation was increased and so the current was increased. 30 Now this was the device claimed by Bru8h, but it was a.ctuaUy shown by Varley, who :t;Lot only gave a description but left a drawing wh!ioh showed quite clea.rly a. serIes-shunt arrangement. The objection urged against this as an anticipa- tIOn (apart from a denial of the clearness of the description, which was disposed of) was, first that Varley did not claim, and second that his specifica• tion was not clear enough for a workman to make a machine. The Oourt of 35 Session and the House of Lords held that, as cr-egards (1) his not having made any claim was neither here nor there if he disclosed the device, and as regards (2) that this objection might be good enough as an objection to Varley' 8 patent (it had long ag.o expir.ed and therefore there was noO questioOn as to it), it was not a good objection, it being enough if the disclosure showed the invention to 40 a skilled man. But the point to be kept in ~iew is that th~~tiQu.Qf.tlw winding was rea)lyi!!~!\ti<:lalill Y.arlell":'-!,£a.~":.nt as in B?·!t8h',~,t~el.~ealt with the same problem and gave th~,~_a~~~~,!:~~' In Otto v. Linford, (1881) 46 L.T., N.S. 35, at page 44, Lord Justice Holker expresses himself thus: "We have it declared, in Hill v. Evanst as the law, 45 ., and it seems very reasonable, that the specification which is relied upon as an " anticipation of an invention must give you the same knowledge as the speci• " ficatioOn of the invention itself". And ill Flour Oxidizing Company v. Carr & Co., (1908) 25 R.P.O. at page 457, Mr. Justice Parker (afterwards Lord * 9 R.P.O. 313. t 31 L.J. Ok. 457. 24 No. 1.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [Vol. XLV. British Thomson-Houston Go. Ld. v. Metropolitan-Vickers Electrical Co. Ld. Parker) says: "When the question is solely a question of prior publication " it is not, in my opinion, enough to prove that an apparatus described in an "earlier specifica,tJion could be made to produce this or that result; it must "also be shown tha,t the specifica,tion contains clear and unmistakable "direcions so to use it". . 5 Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 I may add that my own remarks in A1"IIIStf'OIlg Whitworth &: Co., v. H ard• castle, (1925) 42 R. P. O. 543, at page 555, are quite in line with these dicta. My Lords, these three cases specially cited are quite at olle as rega,rds the la,w and they only differ because the fa·cts differ. Taking the test I have already suggested, a man who, on the eve of the Brush pa,tent, had said: "I want to 10 "find a winding which will retain the advantages but get over the dis• " advantages of the series and shunt arrangements," and also ha,d been handed Va,r[ey's patent, would rinvariably have said: "Why, here is exactly what I want". In Otto v. Linford and in Flo·ur Oxidizing Company v. Carr &: Co. he could have made no. such remark. 15 Applying this test to the present case, I do not think that anyone who was cg,pfr1:l!!.ted, as Rosenberg, with the difficulty of getting ~,heavy machine inj;o synchronii;!m, and troubled with the too great consumpiiion of current if the synchronised motor were turned on a,t once, and who, looking over o.lder spec:i• fica.tions which had to do, with such machines, had come upon Tesla's Specifica- 20 tion-I do not tllink that such a man. would have been in the least likely to think that'the solution of his problem ,had been provided for him. True he w~Lin.,.tlle drawings, . ha,ve seen ,t'YQ,~.a:C~~!l~8Je series., butJhtL!"~~_s9n. suggested for that would'have been tIle idea ofget}~p~.J)()t,h...J.h~lllachines at work, and there would have been no indication, or even hint, thaCine'series 25 arrangement, with properly proportioned machines, got over the difficulty of getting into proper synchronism I am therefore of opinion that Rosenberg's Patent was not fOl'eclosed by Tesla. This opens the question of infringement. N ow the machine in question is shown by an agreed on drawing. That drawing shows a starting motor capable 30 of being connected in s~ries with the rotary of a synchronous motor, all exactly as in the Rosenberg Patent. But there is an addition in the shape of a choke coil through which a current may be passed in shunt past the starting motor direct to the rotary, the result being that there is a current in parallel with the current going through the starting motor. The legend appended to the drawing 35 shows that the way of working is to start matters by turning on the current which g02S through the starting motor and then, when approximately synchronous speed ~s re.ached, to open the. parallel connection. Synchr?ni~m being effected, a sWlt.ch IS then operated whICh cuts out both the choke COlI CIl'• cuitand the starting motor and the machine runs on a current direct to the 40 rotary of the synchronous motor. The Appellants' argument is that thi.s is not an infringement because the machine does not. work, as does Rosenberg's, by one operation but requires two. And further he says that the device of the choke coil is an independent device distinguishing it from the Rosenberg method which has no such device for that 45 purpose, i.e., for the actual attainment of synchronism. Rosenberg does men• tio,n a choke coil, but that is for the purpose of not shutting off the starting motor too suddenly and giving too much of a shock to the synchronous motor. 25 Vol. XLV.] REPORTS OF PATENT, DESIGN, AND TRADE MARK CASES. [No. 1. British Thomson-Houston Co. Ld. v. Metropolitan-Vickers Electrical Co. Ld. Now as regards the first of these arguments it is, I think, clear that you can• n!;!..t ~voi~JnfriIlgement !>r takin.ga patented m8iChine_~Ln~_t.h_en. IIla!~~~k a little worse..Ji1!ItIl ij; :naturJ},Ily. w:ou.l~.and then remeifYl!!K....that worseness by another device, and that is just what the Defendants have done. Tliey have 5 made their starting motor in such a fashion that, being in series with the Downloaded from https://academic.oup.com/rpc/article/45/1/1/1603592 by guest on 28 September 2021 synchronous motor, it will work up the revolutions to the appropriate speed but it will not always or invariably pass enough current to allow the synchronous motor to make that last effort which ensures synchronism, and then they remedy that defect by introducing a common electrical device by means 10 of a choke coil, or, in other words, a regulated shunt, t'o give the synchronous motor just that extr.a current which it requires. The law as to infringement of combinations is well settled. Of course, if the infringer takes the combination stock lock and barrel there is no question, but it is very easy to modify a combination and the modification may be effected 15 by either ,addition or subtraction. The question for the Oourt is not that of detecting absolute similarity, but is that of seeing whether the pith and marrow of the combination, to use Lord Cairns' phrase, has been taken, and if that has been done there is an infringement in spite of .any modification. I am, of course, excluding the case where a modification has patentable matter in it'self. 20 Now, applying that criterion, I have no doubt that the pith and marrow of RO'8e'nberg has been taken in this machine. There is the series connection; there is the avoidance of too great current passing to the synchronous motor in init~o; there is the shielding effect of the starting machine; there is the gradual trans• ference of voltage; ,but just because the starting machine has been designed with 25 such a resistance in its armature that it will nOot always or invariably pass sufficient current to allow the synchronous machine to get into synchronism, t~ere has bee~ a~ded a c0Il1:mon device .to get over that difficulty. That, in my VIew, le~ves mfrm.gement Just where It was, and I am therefore of opinion, aloug WIth the trIal Judge and the Court of Appeal, that here there was 30 infringement. I move that the Appeal be dismissed with costs. This is the Judgment of the House.