July 23, 1963 o. HERMANN 3,098,906 ZERO SPEED swzwcu Filed Feb. 2, 1962 2 Sheets-Sheet 1 LI 2628 22 24 \\ \\\\\\% 2 0 M.”/, a;a/wm mz/m m? m” July 23, 1963 o. HERMANN 3,098,906 ZERO SPEED SWITCH Filed Feb. 2, 1962 2 Sheets-Sheet 2 87 94 ‘225 80 I36 I26 I28 Err?. I88 /76 175/"?! 2 2/2 I, F7472 22o’ F164; -/.90 INVENTOR. 077a ?fe/1717M” 72AM- /7@ 1 31,698,996 United States Patent 0 we Patented July 23, 1963 l 2 switch arrangement of the nature referred to which is 3,h%,906 relatively simple to construct. ZERO SPEED SWITCH Otto Hermann, Cincinnati, Ulric, assignor to The ll. K. , Still another object is the provision of a rotary mercury Le Blond Machine Tool (10., Cincinnati, @hio, a'ccrpo switch in which there is substantially no deterioration or ration of Delaware contamination of the mercury on account of the making Filed Feb. 2, N62, Ser. No. 179,686 and breaking of the circuit through the switch. , 6 Claims. (Cl. zoom-so) A still further object of this invention is to provide a rotary mercury switch which is equally eilective in both This invention relates to electric switches and is particu directions of rotation. ~ larly concerned with a rotary switch employing mercury 10 Still another object of this invention is the provision as a conductive material. ' of a rotary mercury switch which is insensitive to direc In connection with many machine tools and the like, tion of rotation and which can be arranged for either mak it is important to be able to determine the instant of ing or breaking the circuit therethrough when the switch stopping or starting a rotating member, or to be able to is stationary while either breaking or making the circuit ?x a predetermined time before or after the instant of 15 therethrough when the switch is rotating. starting or stopping. Switches of the rotary type that can Still a furtherobject of this invention is the provision be connected to the rotating member are known but here of a rotary mercury switch in which any predetermined tofore such switches have been expensive and complex delay period can be built into the switch so [that the mak and are usually quite inaccurate with respect to ?xing the ing or breaking of the circuit by the switch can be caused instant of starting or stopping ‘of the rotating member. 20 to occur a predetermined time atter the switch either Among the faults of such switches according to the commences to rotate or comes to a halt. prior art is the fact that some thereof operate on the in These and other objects and advantages of this inven ertia principle, in which case, the rate of acceleration or tion will become more apparent upon reference to the deceleration of the rotating member may be in?uential following speci?cation, taken in‘ connection with the ac on the reaction time of the switch. In other cases, the 25 companying drawings, in which: switch will operate by means of friction and this can be FIGURE 1 is a. diagrammatic representation of a lathe objectionable on account of the heat developed and the showing a switch according to the present invention associ wear that takes place. ated therewith and connected in circuit with a control ele In my prior application, Serial No. 63,740, ?led Octo ment of the machine; ber 20, 1960, now Patent No. 3,094,595, I show a switch 30 FIGURE 2 is a vertical sectional View through the of the rotary type in which a pool of mercury is employed switch‘ as indicated by line 2--2, on FIGURE 1 and show for making and breaking the electrical connection between ing the switch as it appears when it is rotating; two terminals so that the switch can indicate either rota FlGURE 3 is a fragmentary view of the lower portion tion or non-rotation of the member to which it is attached. of the switch showing the appearance of the switch when This switch structure avoids the drawbacks referred to it is stationary and the pool of mercury as collected in above but has a drawback of its own which can become the bottom of the switch; ' . a serious matter where the switch is cycled a great many FIGURE 4- is a vertical sectional view indicated by line times as would be the case with certain machine opera 4A4- ori FIGURE 2 showing the construction whereby a tions. 40 predetermined time delay can be built into the switch; . This drawback comes about because the making and FIGURE 5 is a sectional view indicated by line 5—5 breaking of the circuit in my prior switch, as disclosed in on FIGURE 2 showing one manner in which the switch the above identi?ed application, is accomplished between. can be mounted on a rotating member; the mercury and a metal terminal or electrode within the ‘FIGURES 6*through 13 are vertical sectional views switch so that the making and breaking of the contact through modi?ed constructions of the switch; occurs between two dissimilar metals. This causes arcing FIGURE 14 is a vertical sectional View through still and burning and thereby deterioration of both the metal another modi?ed ‘form which the switch according to terminal and the mercury and possible severe contamina the present invention can take and which modi?cation is tion of the mercury. particularly characterized in that the circuit through the In the switch according to the present invention, this 50 switch is made when the switch is rotating and is broken _ drawback is eliminated and the making and the breaking when the switch is halted; and of the circuit is accomplished entirely within the pool of ‘FIGURE 15 is a vertical sectional view indicated by _mercury, the said mercury dividing into two pools to break line 15-45 on FIGURE 14 showing the arrangement in the circuit and combining into a single pool to make the the switch of the channel which the mercury ?lls when circuit. The making and breaking of the circuit thus 55 the switch is rotating thereby to make the circuit through does not take place by separating or joining two dissimilar the switch. ' metals but takes place by joining \or separating only one Referring to the drawings somewhat more in detail, in metal, namely, mercury. FIGURE 1 there is shown a lathe which may comprise a I have found that the switch according to my improved bed 10, a tailstock 12, a headstock ‘14 and a carriage 116. construction exhibits substantially no deterioration, even 60 The headstock includes a spindle adapted for being driven though cycled rapidly and over 'a long period of time, and, as by motor 18 through'rdrive belts 20. The headstock accordingly, the switch according to the present invention includes shiftable gearing under the control of a control is superior to those of the prior art and is even superior element *22. Control element 22 has associated there to the switch disclosed and described in my above iden with a brake 24 that is normally engaged by springs 26 so ti?ed co-p'ending application. 65 as to prevent movement of control element 22. Energiza With the foregoing in mind, it will be evident that the tion of a solenoid S1 is e?fective through linkage 28 to primary object of the present invention is to provide a release the brake so that the control element 22_can be , rotary switch utilizing mercury which is greatly impnoved shifted. in operating characteristics over switches according to Solenoid S1 is connected in circuit between power lines , 70 L1 and ‘L2. by a rotary mercury switch 30 constructed the prior art. according to this'invention. Switch 30‘ is normally closed Another object of this invention is the provision of a when it is halted so that when the ‘drive motor \18 is de 3,098,906 a (.1 energized and comes to a halt, the switch closes and the closed by a plug 70. This ?lling hole can be availed of solenoid S1 is energized to release brake 2-4 whereupon for introducing the mercury into the switch after it has control element 22 can be shifted. When motor 18 is been assembled and can also be availed of for flushing out again energized, however, switch 3% opens and de-en the switch with an inert gas such as nitrogen or carbon ergizes solenoid S1 and the brake 24 closes and control monoxide and ‘for entrapping ‘the inert ‘gas therein. This element 22 is held against shifting movement. plug can, of course, be availed of for removing the mer The construction of switch 30 will be seen in FIG cury from the switch and re?lling it in the event this should URES 2 through 5. This switch, generally, comprises a become necessary. generally cylindrical cavity in which there is a pool of A particularly important ‘feature of the switch of the mercury. The mercury engages two conductive slip rings 10 present invention is the provision therein of means for and, when the switch is stationary, the mercury bridges delaying the closing of the switch ‘when it is halted. This between the slip rings and, when the switch is rotating, is accomplished by restricting the movement of the mer the pool of mercury separates to form two pools, one en cury from its two pool condition to its single pool con gaging each of the said slip rings so that when the switch dition.