US1851277A - Thermostat - Google Patents

Description

March 29, 1932. H GRAYSON 1,851,277

THERMOSTAT Filed Feb. 2l, 1929 Patented Mar. 29, 1932 r UNITED STATES-PATENT JOHN GBAYSON, OF LYNW OOD, CALIFORNIA, ASSIGNOB. TO L INC., k07F LYNWOOD, CALIFORNIA,` A CORPORATION OF CALIFORNIA i 1,851,277.LA y

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GBAYSON THERMOSTAT lApplication led February 21, 1929. Serial No. 341,608.

c This invention relates to a snap action thermostat adapted for use with water heaters and similar devices, the same being especially designed to suit the requirements of gas operated devices of that general description.

The principal object of my invention 1s to provide a thermostat which is extremely quick in its action, will function within a very short temperature range, can be easily adjusted to suit requirements, and can be easily taken apart and put together again whenever it is desired to clean or inspect the same. Still more particularly, it is the object of this invention to provide a snap action thermostat 1|, which does not require the use of a spring metal diaphragm but embodies a mechanism which will maintain the valve in wide open position up to the instant it is snapped closed and' will'likewise maintain the valve tightly $0 closed upto the instant it is snapped open, another advantage of this mechanism being in the fact that extreme temperature conditions cannot possibly result in any injury thereto.

According to my invention the valve is slidably mounted on'a plunger suitably mounted for reciprocation in the center of the valve seat. said plunger having a portion thereof profiled in the form of a double cone, preferably coaxial with the rest of the plunger, 36 and having one, two or more pins slidably mounted in radial ybores in the hub of the valve having their inner ends pointed and spring pressed into engagement with the double cone cam surface on eitherside of the middle there,- of,v whereby to hold the valvehyieldingly but with appreciable pressure either in the open or closed position, slight movement of the plunger 'in one direction serving to cause the valve to snap open, and rslight movement in the other direction causing the valve to snap closed by reason of the pins being caused to ride over the middle orV high point of the cam surface from one side to the other. The plunger is arranged to be operated positively 5 my invention will be discussed in the followin one direction bythe movable thermostatic' ing specification in which reference is'made to the accompanying drawings, wherein- Figure 1 is a section through a thermostatf ically controlled gas valve for a Water heater, embodying my invention, the valve being shown closed;

` Fig. 2 is a similar view of a part of Fig.

1 showing the parts changed lin position cor, responding to the open position ofthe valve;

Fig. 3 is a cross-sectionon the line 3 3 of Fig. 1, and y v Fig. 4 is a cross-section on the line 4--4 of Fig. 2. f

The same reference numerals are applied to corresponding parts throughout the views. The thermostat in connection with which I illustrate my invention comprisesthe usual rod and tube elements 5 and 6 respectively,v

the one being 'substantially non-expandin because of its low coeiiicient of expansion, an the other being expansible by reason of its comparatively high coeicient of expansion. I prefer to make the element 5 of a rod of invar, which, as is kWell known has substan-y tially no expansion or contraction withv changes in temperature, and prefer to make the element 6 of a brass or copper tube so as to expand and contract with temperature variations. The tube 6 is threaded `or otherwise suitably Iixed in the cast hollow valve body 7 inside the externally threaded lplug portion 8 thereof, by means'of which the valve body is arranged to be mounted in the side or bottom of the tank of a gas operated water heater or the like. The rod 5 is adjustably secured at its outer end in the outer end of the tube 6, as by threading into a plug 9, which in turn is preferably threaded and soldered in place in the end of the tube 6 so as to be held against turning. From this description it must be evident that expansion and con-v HEAT co'N'rnoI..

vso

pipes 12 and 13, the former extending from the gas main and the latter being connected to the burner of the heater. A by-pass connection (not shown) from the pipe 12 to the p'illlot light of the burner is usually provided.

e flow of gas from the pipe 12 to the pipe 13 is arranged to be controlled by means of a disc valve 14 slidably movable on a plunger i \15 toward or away from the seat 16 to cover in a center ho or uncover a plurality of ports 17 provided in the inner end of the hollow plug 18 threaded into the valve body 7, as shown at 19. The plug 18 is cylindrical and intermediate its ends has an annular groove 20 formed on the outside thereof with which a plurality of pprts 21 provided in the wall of the plug ve communication. In this way it is not nry to have the lug 18 assmne any certain position in the ody 7 to ermit the 'flow of gas from the pipe 12 to t e pipe 13 through the ports 17 and 21. The inner end of the plug 18 is slightly reduced to provide an annular shoulder 22 thereon for the purpose of compressing packing 23 between the plug and an annular shoulder 24 formed by a shght enlar ement of the cylindrical bore 25 of the y 7, whereby to prevent any leaka of as through the valve body about the p ug. plug 26 is threaded in the outer end of the plug 18 to seal the valve body.

The plunger 15 is slidably received at one Aend in a center hole 27 provided in the inner endof the 1plug 18 and at the other end e 28 provided in a plug 29 having a press fit in the bore 25 of the bod 7 A graphite-asbestos washer 30 is dispose in a recess in the plug 29 and fits snugly about the plunger 15 for a gas-tight joint, said washer bein suitably held in place by a metallic was er 31 havin a ress fit in the same recess therein. imi arly, another graphite-asbestos washer 32 is mounted in a in the face of the valve 14 and has a close fit on the plunger 15 to prevent v the leakage of gas between the valve and plunger when the valve is closed, a metallic washer 33 being also provided to hold the washer 32 in place. The plunger 15 is suitably cylindrical at both ends where it fits in the center holes 27 and 28, but has the intermediate portion thereof formed to provide a double cone cam, as indicated at 34, the middle or high point 35 thereof being defined by the bases of the two cones occupying the same plane.-

Now, one, two, or more, but preferably two, diametrically opposed, )ins 36 are slidably received in radial guide lioles 37 provided in the hub 38 on the back of the valve 14 and have conically pointed inner ends arranged in engagement with the double cone cam 34 0n either side of the high or mid point 35 of the latter. These pins are spring pressed inwardly suitably by means of a single semicircular or crescent shaped leaf spring 39 which has the reduced ends 40 of said pinS passed through' holes provided in the ends thereof to receive the same. The pressure of the spring 39 on the pins 36 tendin to cause the latter to move inwardly, resu ts in the movement of the valve 14 in either direction on the plunger 15 depending on which side of the mid or high point 35 of the double cone cam 34 the ends of the pins 36 happen to engage.A When the pointed ends of the pins 36 engage the cam 34 to the right of the mid point 35, as shown in Fig. 1, the valve 14 moves to the right until it engages the seat 16, being then held in such closed position under a definite appreciable pressure for which the spring 39 is, of course, responsible. On the other hand, let us assume that while the valve is closed, the plunger 15 is moved to the right from the position shown in Fig. 1, just enough to bring the mid point 35 of the cam 34 to the right of the pointed ends of the pins 36. When that occurs, the pointed ends of the pins 36 ride down the op ite inclination of the cam 34 on the left of the mid point 35 and cause the valve 14 to lnove tothe left to the open position shown in Fig. 2, the movement being limited by the engagement of the hub 38-of the valve with the plug 29. It will now be shown how the plunger 15 is arranged to be moved ositively to the right under the action o the thermostatic element 5, and is arranged to be returned under spring action.

A coiled compression spring 41 is provided inside the plug 18 and has its one end fitting over the reduced end 42 of the plunger 15 and engaging a washer 43 passed over the said reduced end whereby to tend normally to urge the plunger 15 toward the left, the other end of the spring 41 fitting about and held in position by a small boss 44 provided for the purpose on the inside of the plug 26. The opposite end of the plun er is rounded, as shown at 45, and has the inner ends of a pair of non-resilientlevers 46 enga ing the same, said levers being struck from s eet metal and suitably ribbed longitudinally, as indicated at 47, to lend stiffness. The outer ends of said levers rest on an annular, beveled seat 48 provided on the edge of an annular flange 9 formed on the plug 29. The beveling o seat 48 insures contact of the levers 46 therewith only at their extreme outer ends and also allows the levers a certain amount of freedom for rocking motion with res to the seat required in operation. A cy indrical plunger or follower 50 is slidably received in the end of the bore 25 and has a circular knife-edged shoulder 51 arranged to have line contact with the levers 46 near the outer ends thereof, or, more specifically, at points on the circumference of a circle of a radius slightly less than that of the plunger. The plunger has a central recess 52 on the back thereof in which the rounded end ofthe thermostatic element 5 engages. Since the and' side` loo levers 46 are supported at their extreme outer at points near the outer ends, it will be evident that the levers will have rocking motion communicated thereto in the movement of the rod and, vsince the inner ends of the levers 46 bear against the end of the plunger 15, the latter Will be given amplified movement, which, however, is always proportionate to the amount of movement,- of the rod 5.

In operation, it will be evident from the foregoing description that when the tubular thermostatic element 6 is hot and consequent- .ly slightly elongated,fthe rod element 5 is retracted to the left with reference to the body 7, and the plunger 15 is moved under action ofspring 41 to the positionshown in Fig. 1, in which the pointed inner ends of the pins 36 engage the cam 34 to the right of the mid point thereof. The spring-41 keeps the plunger 15 under a substantially constant end thrust toward the levers 46. The valve 14 remains closed until the tubular thermo- `static element 6 cools olf enough to result in sufficient contraction thereof for the rod element 5 tomove to the right and forcethe plunger 15 to the right against the action of the spring 41 enough to causethe pointed inner ends ofthe pins 36 to ride over the mid point 35 from the right hand'side thereof to the left hand side, whereupon the spring 39 causes the valve 14 to snap open. Obvious-V ly, the mid point 35 of the cam Will be defined bya sharp edge. Consequently, there can be no fluttering of the valve; it will remain fully closed up to the instant that it snaps open, and, conversely, it will remain fully opened up to the instant thatit snaps closed. The

-more or less sharply dened mid point 35 of the cam 34 and the more or 'less sharpened .cone pointed ends of the pins 36, as well as the guides 37 that cause 'the pins to move truly, in a predetermined plane, cooperate to make the valve function within an extremelyy short temperature range. Now, while it is apparent that avery slight movement of the plunger 15 will suffice to snap the valve from open to closed position, or `vice versa,

it will also be seen that anexcessive amount of movement of the plungerfl cannot possibly result in damage to any part of the mechanism; if, after the valve has been opened, as shown in Fig. 2, the plunger l5 is given still further movement by reason of additional contraction ofthe tubular thermostatic element 6, the valve. vwill still remain open, and the same is true in the .closing lof the valve, additional movement of the plunger having no effect whatever. This point is of yconsiderable importance from the standpoint that extreme temperature conditions will not result in injury to the device. If it is desired at any time to take the device apart for the purpose of inspection or cleaning, it is a simy valve seat 16; the spring 41 remains caged in placed improperly. If any adjustment of the device is desired at any time, that is taken care of by simply moving the lever 10. Hot or Cold markings may be provided on the outside of the valve body 7 adjacent the projecting end of the lever 10 and in that event, the shifting of the lever toward Hot results in unscrewin the rod element `5, and vice versa in the shi ing, of the lever toward Cold.

It is believed the foregoing description lmparts a good understanding of the various` features of my invention. While AI have illustrated and described the application thereof toa valve for a gas-operated water heater, yit should be understood that there are numerous other applications. Furthermore, as regards the various details of construction and arrangement illustrated, it should b'e understood that various changes mlght be made without;y seriously `departing from the invention. For example, I do not llmit myself to the use of the particular movement amplifying means herein shown,

namely, the plunger and levers 46, inasmuch as a compound fulcrum, such as is commonly employed in thermostatic devices of this kind, kmight be employed to transmit amplified movement to the plunger 15 in the movement of the rod 5.

I claim:

1. Inathermostatic device of the character described, a casing, a valve or other element therein to be operated, the same having an integral enlarged hub portion, said hub having an elongated hole therein for bearing support of the valve l011 a plunger, a plunger in said casing received in the holefinthe hub portion of said valve so that the latter is slidably mounted thereon for reciprocation toward and away from a seat therefor in` said casing, and means housed in the hubportion providing an operating connection between the plunger and the valve whereby the latter is arranged to be moved in one direction in the event of a predetermined movement lof the plunger .relative thereto in the opposite direction.

having a hub portion, a plunger in said cas-Jv .ing` concentric` with the valve and `having` `the hub portion of the latter slidably mounted thereon to serve as a guide therefor, said plunger havlng means for operating the same, sald plunger having a double cone cam yim thereon within the hub of the valve with respect to which the valve is slidable on the` lunger, the cones of said cam having their ases in the same plane to provide the high portion of the cam, one or more pins slidably mounted in transverse bores provided in the hub of the valve having their inner ends engaging the double cone cam on either side of the high ortion, depending on the position of the va ve, and spring means urging the pins inwardly into enga ement with the cam.

3. A device as set fort in claim 2 wherein the double cone cam has a sharply defined high portion and wherein the one or more pins have their inner ends conically pointed to ride abruptly from one side to the other over the hi h portion of the cam.

4. A device as set forth in claim 2 wherein the pin is mounted for substantially radial movement, and wherein the spring means for operating the same comprises a substantially semi-circular leaf spring fitting about the valve hub and suitabl held in place in such position and having t e outer end of the pin operatively connected with one end thereof.

5. A device as set forth in claim 2 wherein two diametrically opposed pins are provided mounted for substantially radial movement with reference to the valve and wherein the spring means comprises a single substantially senii-circular leaf spring tting about the valve hub substantially concentric therewith and having the opposite ends thereof operatively connected with the outer ends of said ins and tendin normally to urge the pins inwardly towar each other.

6. In a thermostatic device of the character described, the combination with a thermostatic element arranged to move in the event of temperature variation, of a casing providing a substantially cylindrical bore therein, there being a valve seat about a valve port provided at one end of said bore, a valve in said bore movable toward and away from the seat, a plunger reciprocably mounted in said casing having the valve slidably mounted thereon to serve as a guide therefor, spring means acting against one end of said plunger tending normally to move the same in one direction, one or more levers disposed radially with reference to the bore engaging the other end of the plunger at their inner ends and having their outer ends suitably supported in said bore, another lunger slidably received in said bore and liaving the thermostatic element engaging the back thereof to communicate movement thereto, the front of said plunger having an annular shoulder projecting therefrom arranged for engagement with the levers near the outer ends of the latter whereby in the movement of said plunger amplified movement is communicated through the levers to the first mentioned plunger, and means providing an operating connection between said plunger and valve whereby when the former is moved in one direction the latter is moved in the opposite direction.

7. A structure as set forth in claim 6 wherein the thermostatic element constitutes the inner element of a thermostat and is threadedly mounted at its outer end in the outer end of the outer element to permit endwise adjustment of the inner element with respect to the outer element by the turning of the former with reference to the latter, the said casing having an openin in one side thereof adjacent the end of sai adjustable thermostatic element, and a part attached to said element and operative throu h said opening.

8. A structure as set fortg in claim 6 including a hollow plug removably mounted in one endvof the bore in said casing and providing the valve seat and port on the inner wall thereof the first mentioned plunger bein slidably received in acenter ide openinggrovided in the inner wall o said plug, sai plug havin the plun r actuating 'spring mounted t erein, an a closure for said plug providing an abutment for the outer end of said sprin 9. A structure as set forth in claim 6 including a hollow plug removably mounted in the one end of the bore in said casing and having the valve seat and valve rt provided in the inner wall thereof, the rst mentioned plunger being slidably received at one end in a center guide o ning provided in the inner wall of said ug, and another plug stationarily mountedp in said bore and having a center guide opening slidabl receivin'g the other end of said first mentioned plunger.

10. In a thermostatic device of the character described, the combination with a thermostatic element arran d to move in the event of temperature variation, of a casin providing a mounting for said element, said casing having a substantially cylindrical bore therein, a hollow plug removably mounted in the one end of said bore rovided with a valve port in the inner wal thereof and a valve seatrabout said port, there being a center guide opening in the inner wall of said plug, a plunger slidably received in said guide opening, spring means in said plug acting against the end of said plunger tending normally to move it in one direction, means operated by the thermostatic element and operatively related to the other end of said plunger arranged to move the latter in the opposite direction against the action of said spring, a valve slidably mounted on said plunger for movement toward and away from the valve seat, and means providing.

an operating connection between the plunger and the valve whereby when the former is moved in one direction the latter is moved in the opposite direction.

11. A device as set forth in claim 10 including another part stationarily mounted in the bore of said casing behind the valve, said part having a center guide opening slidably receiving said pluunger, the said lll part serving to limit movement of the valve away from its seat.

- 12. In a thermostatic device of the char? acter described, a casin a valve or other element therein arrange to be operated and havinga hub portion, a plunger in said casinconcentric with the valve and having the hu `portion of the latter slidably mounted thereon to'serve asa guide therefor, said plunger having means for operating the same, said plunger being annularly. recessed within the hub of the valve to provide a double cone cam over which the valve hub is arranged to slide on the plunger, the cones of said cam having their bases in the same plane to provide'the high portion of the cam, one or more pins slida ly mounted in radial holes provided in the hub of the valve having their inner ends engaging the double cone cam onv either side'of the high portion, depending on the position of the valve, and spring means urging the pins inwardly into engagement with the cam.

` 13. In a device of the character described, the combination of a casing having a longitudinal bore, a plug entered in said bore to define one end of a valve chamber, another plug entered in the bore to define the other end of the valve chamber, .the last mentioned plug being provided with a ,valve port and a valve seat about said port, there being guide openings in alignment with one another in said plugs, a plunger slidably received in said guide openings, means for operating the plunger backand forth, a valve slidably mounted on said plunger inthevalve chamber and arranged by engagement with the iirst plug to have the movement thereof away fromthe seat limited, and means in the sliding joint between the valve and plunger providing an operating connection between the plungerand valve whereby when the former is lmoved in one direction the latter is moved in the opposite direction.

14. A device as set forth in claim 13 Where-A in the means for operating the plunger back and forth includes a coiled compression spring mounted within a hollow portion of the second plug and acting against the end of the plunger projecting into said plug through thev guide opening inthe inner wall thereof.

15. A device asset forth in claim 13 wherein the bore of the casing is enlarged at one end for reception of one of said plugs, thereby providing anannular shoulder in the bore, the device including a vpacking member received in the bore in abutment with the annular shoulder, there being an annular shoulder on said plug arranged to abut the packing member from the opposite side to compress said member between the shoulders whereby yto seal the joint at the plug.

16. In a 'device of the character described, the combination ofa casing4 having a bore provided therein, a valve seat in said bore defining one yend of a valve chamber, a plug entered into the bore to deine -the other end of the valve chamber, a plunger slidably mounted in said i plug and extending into the valve chamber, means for operating the plunger back and forth, a valve for coopera- `tion with the valve seat slidably mounted on the plunger in the valve chamber, and means in the oint vbetween the valve and plunger provi ing an operating connection Jetween the plunger and valve whereby when the former is moved in one direction the latter is moved in the opposite direction.

17. In a `device of the character described, the combination of a casing having a bore provided therein, a hollow plug removably mounted in said bore provided with a valve port in the inner wall thereof and a valve seat about said port, there bein a center guide opening in the inner wall o said plug, a plunger slidably received in the guide opening, means for operating the plunger back and forth, a valve slidablymounted on the plunger and arranged to move toward and away from the valve seat, and means in the jointbetween the valve and plunger providing an operating connection between the plunger and valve whereby when thek former is moved in one direction the latter is moved in the opposite direction.

18. In a device of the character described,

the combination of a casing having al bore provided therein, there being a valve seat in saidv bore at one end of a valve chamber, a plug entered in said bore and delining the other end of the valve chamber, aA plana er slidably received in an opening in said jpug and extending into the valve chamber,-A one or more leversdisposed radially with reference to the plug having their outer ends suitably supported onA the plugy and their inner ends engaging the end of the plunger, means for communicating amplified movement to the plunger by communicating movement to the levers near their outer ends, and a valve mounted on the plunger in the valve chamber for cooperation with the valve seat.

19. In a device of the character-described, the combination of a casing having a bore provided therein, there being a valve seat in said bore at one end of a valve chamber, a pluglentered in said bore and defining the other end of the valve chamber, a plunger slidably received in an opening in said plug and extending into the valve chamber, one or more levers disposed radially with reference to the plughaving their outer ends suitably supported on the plug andtheir inner endsv engaging vthe end of the plunger, means for `communicating amplified` movement to the plunger-by communicating movement tothe levers near their outer ends, a

valve slidably mounted on the plungerin movement away from the valve seat by engagement with the lug, and means in the ioint between the va ve and plunger providing a reversing operating connection wherebywhen the one element is moved in one direction the other element is moved inthe opposite direction.

20. In a valve, a casing, a valve therein arranged to be operated and havinga hub portion, a plunger in said casing concentric with the valve and having the hub portion of the latter slidably and rotatably mounted thereon to serve as a guide therefor, said plunger having means for operatin the same, said lunger having an annular y recessed portion thereon within the hub portion of the valve conformed to a double cone cam shape with respect to which the valve hub is slidable and rotatable, the cones of said cam having their bases in the saine plane to provide the high ortion of the cam, and a plurality of pins ra iall disposed with reference to the hub in a p ane exactly parallel with the bases of the cones and slidably received in radial holes provided in the hub of the valve with the inner ends thereof riding on the cam, and spring means for urging the pin inwardly into engagement with the cam.

21. In a sna -action mechanism, the combination of a p unger, means supporting the saine for endwise movement, a part having a hub ortion slidabl received on said plung er, the plunger an part thereon being arranged to cooperate so that when the one is given a predetermined movement in one direction relative to the other, the other .is arranged to be given abrupt movement in the opposite direction, said plunger havinga double cone cam thereon within said hub rtion, the cones of said cam having their ases in the same plane to provide the high portion of the cam, one or more pins slidably mounted in transverse bores provided in said hub portion and'having their inner ends engagi'ng the double c'one cam on either side of the high portion de ending on the position of the part with re ation to the plunger, and spring means urging the pins inwardly into engagement with the cani.

22. A mechanism as set forth in claim 21 wherein the double cone cam has a sharply defined high portion and wherein the one or more ins have their inner ends conically pointe to ride abruptly from one side to the other over the high portion of the cam.

23. A mechanism as set forth in claim 21 wherein the pin is mounted for substantially radial movement, and wherein the spring means for operating the same comprises a substantially semi-circular leaf spring fitting about the hub portion and suitably held in lace in such position and having the outer en of the pin operatively connected with one end thereof.

24. A mechanism as set forth in claim 2 wherein two diametrically opposed pins are provided mounted for substantially radial movement with reference to the hub portion and wherein the spring means com rises a single substantiall semi-circular lea spring fitting about the ub portion substantially concentric therewith and having the o osite ends thereof operatively connected wit the outer ends of said pins and tending normally to urge the pins inwardly toward eacli' other.

25. In a valve of the character described, the combination of a casing, a valve seat in said casing in closely spaced relation to a wall provided in said casing, a short plunger guided for movement in and projectin through a center hole in the seat at one en and projecting through a hole in the wall at its other en spring means cooo rating with one end of said plunger tending normally to move it in one direction, and means cooperating with the other end of the plunger to move it in the opposite direction against the action of said spring means, a valve disposed in the space between the wall and seat and having an enlarged hub portion slidably received on the plun er as a guide, said plunger having a dou le cone cam thereon within the hub of the valve, the cones of said cam having their bases in the same plane to provide the hi h ortion of the cam, one or more pins sli ab y mounted in transverse bores provided in said hub and having their inner ends engagin the double cone cam on either side of the high portion depending on the position of the valve with relation to the plunger, and spring means urging the pins inwardly into engagement with the cam.

26. A device as set forth in claim 13, wherein the bore of the casing is enlarged at one end for reception of one of said plugs, thereby providing an annular shoulder in the bore, and wherein said plug has an annular shoulder thereon arranged in the entr of the plug in the bore to approach the ot er shoulder whereby to seal the bore by means of the lug.

27. A device as set forth in claim 17, wherein the bore ofthe casing is enlarged at one end for reception of said plug, thereby providing an annular shoulder in the bore, and wherein the plug has an annular shoulder thereon arranged in the entry of the plug in the bore to a proach the other shoulder, whereby to sea the bore by means of the plug.

28. In a thermostatic device of the char'- acter described, a casing, a valve or other elel ment therein to be operated, the same havin an integral enlarged hub portion, said hu havi a hole therein for bearing support of the va ve on a plunger, a plun er in said casin received in the hole in the ub portion of said valve so that the latter is slidably mounted thereon for reciprocation toward and away from a seat therefor in said casing, said plunger being annularly recessed to provide lll a double cone cam thereon Within the hub of the valve, the cones of which have their bases in the same plane to provide the high portion i of the cam, said hub being elongated so that the hole therein is longer than the recessed cam portion of said plunger to provide proper bearing support of the valve in any position thereof on the plunger relative to the cam, one or morepins slidably mounted in l@ transverse bores provided in said hub and having their inner ends engaging the double cone cam.- on either side of the high portion depending on the position of the valve with respect to the plunger, and spring means urging the pins inwardly into engagement With the cam. 29. In a snap action mechanism, the combination of a plunger, means supporting the same for endwise movement, a parthaving a hub portion slidably received on said plunger, the plunger and part thereon being arranged to cooperate so that when the one is given a predetermined movement in one direction relative to the other, the other is arranged to be given abrupt movement in the opposite direction, said plunger having an annularly recessed portion providing a double cone cam thereon Within said hub portion, the cones of said cam having their bases in the 3 same plane to provide the high portion of the cam, the hub portion being elongated so that it is longer than the recessed cam portion of the plunger whereby to have proper bearing support on the plunger in any position of` the part with respect to thc cam, one or more pins slidably mounted in transverse bores provided in said hub portion and having their inner ends engaging the double cone earn on either side of the high portion depending on the 4 position of the part with relation to the plunger, and spring means urging the pins inwardly into engagement with the cam.

In Wit-ness of the foregoing I aiiix my Signature. JOHN H. GRAYSON.

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