Sept. 21, 1943. ' é, MHSTER . 2,330,072 SEAL AND METHOD OF MANUFACTURE Filed May 14, 1941,

ATTORNEY Patented Sept. 21, 1943 . 2,330,072

UNITED STATES PATENT OFFICE 2,330,072 SEAL AND METHOD OF MANUFACTURE ' George Meister, Newark, N. J., assignor to West inghousevElectric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsyl Vania Application May 14, 1941, Serial No. 393,409 15 Claims. (0]. 49-81) This application is a continuation-in-part of illustrated in Figs. 1 and 2, there is shown an my application Serial No. 143,464, ?led May 19, electric discharge tube ll comprising a central 1937, and entitled “Seals and method of 'manu cylindrical or tubular portion l2, relatively small facture.” in cross section, and enlarged end portions I3. This invention relates to treated glass and Through the end portions I3 are sealed tungsten seals, and more particularly to those between lead-in conductors M, the inner end portions I5 quartz, or fused silica, and glass; and those be- '1 of which form electrodes between which a dis tween metal and glass. charge occurs through gas or vapor contained in The principal object ofv my invention, gener said tube. The tungsten, where ~it seals through ally considered, is the production of treated glass 10 the glass, should be clean and bright. This con and a simplified seal between such glass and dition may be obtained by beating the conductors quartz and the reduction of shrinkage in sealing l4 with degasi?ed “Pyrex” prior to sealing into metal wires into such glass. ' the tube ll, reference being made to the Sulli An object of my inventionls the production van et al. Patent No. 1,304,623, granted May 27, of a glass which will seal directly to quartz, there 15 1919, covering such glass. “Pyrex” glass, also by avoiding graded seals to quartz and the ac known as “702EJ” and“‘774” has about the fol . companying complications. lowing composition: SiOz, 80%; B203, 13%; Another object of my invention is the treat A1203, 2%; Na2O+K2O, ‘ii/2%; miscellaneous, ment of glass to improve its qualities for various 1/2%. The clean bright condition of the tung purposes, including that of sealing directly to 20 sten is obtainable by cleaning with sodium nitrite, low expansion vitreous material and receiving washing, and then inserting in the reducing por lead-in conductors composed of tungsten and tion of an oxyhydrogen ?ame where it is readily other suitable metals. beaded or coated with “Pyrex” or borosilicate A further object of my invention is the treat glass. This coated wire, up to more than 200 _ ment of “Pyrex" and other hard glasses to elim mil diameter, may then be united directly to an inate gas therefrom and adapt them for sealing article of borosilicate glass by ‘heat in the usual directly to quartz, at the same time rendering manner. ' such glasses better able to seal to lead-in con In the present embodiment, the intermediate I ductors of tungsten and other suitable metals. restricted portion I2 is formed ,of a quartz or A still further object of, my invention is the 30 fused silica tube, the end portions of which are method of treating glass, so that it will retain ?ared in cross section and decreased in thick a vacuum when tungsten is sealed therethrough nessvas indicated at IS. and seal directly to quartz, comprising removing The enlarged or bulbous end portions 13, of‘ gases therefrom as by heating to a temperature the present embodiment, are formed of boro of about 1700" C. 35 silicate glass, such as f‘Pyrex,” the inner end por An additional object of my invention is to seal tions of which are decreased in diameter, as tungsten wire, even of large size, through “Pyrex" indicated at IT, so as- to correspond with the glass. diameter of‘the end portions’ l6 of the quartz Other objects and advantages of the invention, tube. - - relating to the particular arrangement and con .40 In preparing “Pyrex” or other suitable prefer struction of the various parts, will become ap ably hard glass; for example, “Nonex,” which is parent as the description proceeds. a borosilicate glass with lead; or 1'12 A. J ., which Referring to the drawing illustrating my in is a borosilicate glass with aluminum; for'direct vention, ’ connection or sealing to quartz, the glass is Fig. 1 is a side elevational view of an electric 45 heated to a temperature of 1700“ C.; that is, to discharge tube. about the fusion temperature of quartz. When Fig. 2 is an enlarged longitudinal sectional view this is done, there is a considerable evolution of of one end portion of the tube illustrated in Fig. 1. gas. ' Fig. 3 is a side elevational view of another dise The fusion of “Pyrex," or other borosilicate charge tube embodying my invention. ' 50 ‘glass,effected for in degasi?cationa mass. Due purposesto the high may temperajg also Fig. 4 is an enlarged longitudinal sectional view of one end portion of the tube illustrated ture, however, such fusion should be e?ected in in Fig. 3. . vacuo where a-lower temperature, perhaps1500° Referring to the drawing in detail, and ?rst C., will be sut'?cientv to remove the gas. How this considering the embodiment of’ my invention 55 fusion may hey-accomplished will depend on the 2 2,330,072 reactivity of the constituents of the glass with in which the tungsten wire is beaded just be the container in which the fusion is eifected. yond the inner cone of the ?ame so that the Porcelain may be suitable, as well as graphite, metal remains bright and unoxidized while the and, in the‘ latter case, induction heating may glass ?ows thereon. Such beading has to be done be used. When fusing in porcelain, a furnace fast in order to avoid oxidation. In the pres wound with wire, formed of such refractory metal ent instance, the tube contains a quantity of mer as tantalum or tungsten, could be employed‘. It cury '21 in order to produce a high pressure mer— will, of course, be understood that even under cury discharge lamp. . such circumstances only a limited quantity of It may be wondered why borosilicate glass 10 which has a higher coe?lcient of expansion than glass could be degasi?ed at any one time. quartz will, when degasi?ed, seal directly to - If the deg'asi?cation is continued so that a quartz without the development of cracking clear melt results, an adherent seal l8 may be formed between the glass and the quartz, which strains on cooling. I advance the idea, merely is equivalent to that of any of the special glasses as a theory in support of the fact that the seal 15 can be effected, that when the glass is degasifled which have previously been used, reference be and heated to the same temperature as the quartz ing made to the Keyes et a1. Patent No. 1,014,757 to which it is fused, there is an‘interpenetration of January 16, 1912. ' ‘ between the molecules of the connected mate The foregoing description applies to the forma rials, so that the substance or compound at the tion of a direct seal between the edges of a 20 union therebetween is a combination or mix quartz tube and the degasi?ed edge portions of ture of .the'two, giving the e?ect of a graded a “Pyrex” bulb or tube of similar diameter. seal with a very short intermediate connection. Another way to e?ect the seal is to melt and In any event, my invention avoids the well-known spread on the edges of the quartz, a section of result which occurs when two vitreous materials, degasi?ed “Pyrex” which can then be used for 25 of fairly wide difference in coe?lcients of ex effecting the seal with "Pyrex.” In such an pansion, are directly sealed together. event, the degasi?ed “Pyrex” will extend an ap In view of the foregoing disclosure, it will be preciable distance between the portions l6 and seen that I have devised a degasi?ed glass and II. In other’ words, the junction between the simplified seal between quartz and glass, as well quartz and “Pyre ” will be degasi?ed and the 30 as an improved seal between tungsten and other melted “Pyrex” extend therebetween for an ap similar metals and said glass, thereby avoiding preciable distance, at the place designated l8, the necessity for using special glasses and graded after being melted and applied to the quartz. seals when connecting glass to quartz. In addition, the “Pyrex" or other glass, such It will be understood that usually three or more as those mentioned, which by test, apparently does 35 steps have been used in sealing glass to quartz, ' not lose any of its good properties by the treat see the Keyes et a1. patent previously referred ment; that is, its coe?icient of expansion, for to, because the single-step sealing will not with example, seals to a tungsten wire such as that stand the strains produced on cooling. A pre indicated at 14. Both the ‘Tyrex”-seal-to-quartz ferred method of treating the glass before fusing and tungsten-seal-to-“Pyrex” hold, even though it to quartz is to heat it to a temperature in the the tungsten wire is heated red-hot so that the 40 neighborhood of 1700" C.; that is, approximately “Pyrex” is collapsed and starts to ?ow from the the fusion temperature of quartz, until the evo quartz. ' ' lution of gas ceases and a clear melt results. Although, as above explained, the tungsten Such deeasi?ed "Pyrex" may be sealed to quartz wire Il may be sealed directly through the de to produce a ?rm and gas-tight connection equiv gasi?ed "Pyrex,” or the like, yet in the present alent to that of any of the special glasses. embodiment I have shown it beaded with "GT In effecting a union between “Pyrex" and 70” and. sealedthrough a tip IQ of uranium glass. quartz, alternative methods may be employed. "GT 70,” also called “778,” has about the follow In one instance, for example, I headed degassed ing composition: S102, 69%; B203, 26%; MgO, 50 “Pyrex" to quartz and worked it so that ?nally 1%: and NazO, 4%. Said tip is then sealed to I had a small tube section of degassed "Pyrex” the outer end of the adjacent “Pyrex” end cham which can readily be sealed to ordinary “Pyrex." ber l3, as indicated at 20. The outer portion of In another case I made a short section of a de each tip I9 is desirably composed of "GT 70,” gassed glass tube out of "Pyrex" and sealed it which also preferably extends, as a ?lm or wat 55 directly to the quartz. Polariscope examination ing, for example, along the entire length of the showed that both seals are equally good as far wire in the seal for effecting a gas-tight union, as strains are concerned. Compressive-.strains while the inner portion or remainder is com seem to predominate, which is a preferred state, posed of uranium glass for direct sealing with as cracks are less apt to develop under such the “Pyrex." - 60 " strains than under tensile‘ strains. Most glasses Referring to the embodiment of my invention that'have high fusion temperatures and are used illustrated in Figs.“3 and 4, a discharge, tube in making graded seals with quartz, require that 2| is‘shown comprising a central cylindrical sec metal sealed therein be clean or bright and free tion 22 of quartz and end sections 23 of “Pyrex” from oxide at the seal. With glass degassed in or other glass which has been degasi?ed, as above 65 accordance with my invention, this is the pre explained. and sealed directly to the quartz, as ferred state. However, since such degassed indicated at 24. Through the degasi?ed “-Pyrex" ' glasses are of the commonly known types which 23 at each end of the tube 2| is sealed a tungsten - are used in making metal-glass seals. a little ox— lead-in conductor 25, the inner portions 26 of ide is not believed to be a serious detriment. which form electrodes for the discharge through A degasi?catlon of the "Pyrex” or other glass the tube 2|. The tungsten should be clean and 70 is valuable in improving its qualities for receiv bright where it passes through the glass, as in ing lead-in conductors of tungsten or the like, Figs. land 2. Such a condition may be obtained as the glass will then sealto 25 mil tungsten, for by beadingv the conductors 25 with degasi?ed example, or larger, and retain ‘a vacuum. Presses “Pyrex” prior to sealing into the-tube '2l. Such so made are believed to have less strains than treatment is eifected with an oxyhydrogen ?ame 75

..._. "1v infirm,“ 7' ._r. .. 2,830,072 3 . when treated in accordance with ordinary meth silica glass having lower coemcients of expansion - ods; that is, merely baking at 450 to 500° C.,v on the one ‘hand, and metals such as tungsten ~ thereby avoiding considerable shrinkage. having higher coe?icients of expansion, on the Although the foregoing description applies par other hand, are tougher than 1those produced ticularly to borosilicate or hard glasses such as 5 without degasification. It is, therefore, believed “Pyrex,"- (and especially such manufactured un that I have produced a new glass which is useful der the Hood Patent No. 2,035,318 of March 24, , for various purposes in addition to those for seal 1936, which I have found necessary to degasify in ing to quartz and metal lead-in conductors. accordance with my invention in order to effect Although preferred embodiments of my inven direct sealing with quartz) “Nonex," "172 A. J.,” 10 tion have been disclosed, it will be understood‘ and uranium glass, yet ‘better results may be ob that modi?cations may be made within the spirit tained when making articles of soft glass by de and scope of the appended claims.

gasifying such glasses, rather than using them I claim: . > ' undegasi?ed. For example, soft glass presses 1. A seal comprising completely degasi?ed hard may be degasi?ed with desirable results, making 15 glass fused directly to silica. it possible to substitute copper or other cheaper 2. A seal comprising ‘completely’ degas'i?ed > metal for copper clad nickel steel; commonly borosilicate glass fused directly to quartz. - called “Dumet," provided the metal is kept clean A 3. A seal comprising completely degasi?ed and unoxidized. In other words, my invention "Pyrex” fused directly to quartz, ' > is not limited to the degasi?cation of hard glasses, . 20 4. A seal in which a wire passes through a com by which I means those at least as hard as "Py- _ pletely degasi?ed borosilicate glass, producing a rex," referring to the definition of_“hardness"'v gas-tight connection. ' as found in the paragraph beginning on line 63 5. A seal in which bright tungsten wire passes of page‘ 2 of Sullivan et al, Patent No. 1,304,623, through completely degasi?ed “Pyrex” without noted, but may be employed generally, except that 25 leakage. - ' I have not been able to seal soft glass directly to ‘ 6. The method of treating “Pyrex” for direct quartz. . connection with quartz comprising merely heat A further_ advantage of degasifying glass in ing to about 1700° 0., until evolution of the gas making metal-glass'seals is that the coefficient »ceases, and then sealing it directly to quartz. of expansion of such degasi?ed glass is believed to 30 , 7. The method of treating borosilicate glass to be more nearly linear, especially at highter tem receive a lead-in conductor comprising complete peratures; that is, in the neighborhood of 400° 0., ly degasifying said glass by heating to about and over. From data collected, it is known that 1700° 0., and then sealing said .conductorthere the coefficient of expansion of ordinary ' hard into. ‘ glasses diverges from linear at temperatures high 35 8. The method of connecting vitreous mate , er than about 450° C. Soft glasses show peculiar rials, comprising merely heating hard glass to maxima' in the expansivity curves at about 420° about 1700° 0., until evolution of gas ceases,_ and C. I therefore propose to degasify glass for over then sealing it directly to quartz. - ‘ coming these variations from the normal linear 9. The method of treating borosilicate glass, coefficients of expansion. ~ ' 40 comprising merely heating it to about 1700° 0.. The degassed glass produced in accordance until evolution of gas ceases, and sealing it di with my invention and through which a tungsten rectly to quartz. V wire was sealed, showed a lower strain than ordi 10. The method 'of making a seal, comprising nary “Pyrex” receiving a tungsten wire, even completely degasifying borosilicate glass by heat through the wire in each case was bright and un 45 ing to about 1700° 0., and then sealing a tungsten oxidized. _ _ . wire therethrough. By virture of degasi?cation of the “Pyrex," and _ 11. .The method of making a seal, comprising especially such produced under the Hood patent completely degasifying “Pyrex” by heating to before mentioned, I have been able to make seals about 1700° 0., and then sealing a tungsten wire in which the difference-in expansion between the 60 thereinto. - parts sealed is as high as 20x10-7, as compared 12. A seal in which tungsten wire passes with 5 to 10x10~1 for ordinary glass seals. through completely degasiiled-hard glass without Although I prefer using “Pyrex” as manufac leakage. ' . - . tured under said Hood patent, yet I may use boro 13. The method of treating hard glass to re silicate glasses having coe?icients of expansion 65 ceive a lead-in conductor, comprising completely varying from 28><10-"l to approximately that of degasifying said glass by heating to about 1700' tungsten at 42x10-". The glass of the Hood 0., and then sealing a tungsten wire there' patent, however, has a coe?icient of expansion through. . -. ' of 33x10“. Degasifying such glass slightly‘ re 14. A seal in which wire passes through a com duces its coe?icient of expansion 'as say to 66 pletely degasi?edglass, producing a gas-tight 31.7 x 10*", while slightly raising ‘its softening connection. ~ I. -' . point from 819° C. to 822° C. A further .effect of 15. The method of treating glass to receive a degasi?cation is to give the glass a more brilliant lead-in conductor, comprising completely degasi appearance, believed to be due to an increase fying said glass by heating to ‘about 1700° 0., and ' in the index of refraction. -Also the seals pro 65 then sealing said conductor therethrough. duced between my degasi?ed glass and quartz and the other vitreous materials including 96% anoaaa marina.