US2556603A

US2556603A - Fluid pressure cycling system

Info

Publication number: US2556603A
Application number: US626342A
Authority: US
Inventors: Jurg A Senn
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-11-02
Filing date: 1945-11-02
Publication date: 1951-06-12
Anticipated expiration: 1968-06-12

Description

June l2, 1951 .J. A. SENN FLUID PRESSURE CYCLING SYSTEM Filed Nov. 2, 1945 June l2, 1951 J. A. sENN 2,556,603

FLUID PRESSURE CYCLING SYSTEM Filed Nov. 2. 1945 2 Sheets-Sheet 2 Patented .une 1.2, 1951 UNITED STATES PATENT OFFICE FLUID PRESSURE `CYCLING SYSTEM Jurg A. Senn, Milwaukee, Wis.

Application November 2, 1945, Serial No. 626,342

This invention relates to cycling systems and particularly to devicesvof this class which supply current to an electric heater in the increments necessary to replace the heat dissipated by a body heated by such heater. In supplying current to surface burner units of electric ranges, for example, it has been proposed to provide a temperature sensitive or feeler element centrally of the burner coil and in contact with the bottom of the pan to feel the temperature thereof. The heat received by the feeler unit is converted to fluid pressure acting upon a remotely located pressure diaphragm which serves to adjust the position of a pair of cooperating switch elements with respect to a switch-opening cycling cam. A

single cycling cam may be arranged to actuate several sets of switch elements spaced there about, four for example, corresponding to the number of surface plates of the usual electric range. This grouping of the switch arms for the respective heater plates about the central cycling cam is disadvantageous and difficult to attainy however, where only the customary long and relatively narrow range switch panel is available. n .g'An object of` this invention is to provide a cycling system for electric heaters in which the cycling source is fluid-coupled to the switch cycledthereby and hence may be located remote from the latter.

An additional object of the present invention is to provide a cycling system for electric heating plates in which both the feeler element and the cycling cam exert additive fluid pressure upon one or more expansible, switch-moving diav. Another object is to provide a cycling system for electric heaters in whichthe feeler element, cycling source and switch-actuating diaphragm are connected by a common, liquid-filled conduit.

Another object is to provide a cycling system for electric heaters in which the feeler element and cycling source are fluid-coupled to respective switch-actuating diaphragms.

A further Objectis to provide a cycling system for electric' heaters in which the cycling switch movement results from the periodic electric heating of the fluid within a sealed diaphragm by a resistance means located adjacent thereto.

Another object is to provide a switch for o cycling systems as described-in which the zero adjustment is effected by shifting a portion of the switch lever engaged by the range cam thereby effecting a considerable simplification in Switch construction.y f

21 Claims. (Cl. 20G-83) A further object is to provide a switch for cycling systems as described characterized by ilexible, hinge-mounted switch arms thus elimif nating lost motion, friction and misalignment of parts.

Other objects and advantages of the invention will appear as the description thereof proceeds.

Reference is now made to the drawing wherein Fig. l is a vertical sectional view of one form of my invention and is taken on the line l-I of Fig. 2;

Fig. 2 is a top View of the switch shown in Fig. l and is taken on the line 2-2 of Fig. 1; Fig. 3 is a modification of the construction of Fig. l and 'shows the replacement of the cycling cam l5 by an electrically heated sealed diaphragm;

Fig. 4 is a vertical sectional view of a simplied form of fluid actuated cycling switch according to the systems of Figs. l and 3 and taken on the line 4 4 of Fig. 5; and

Fig. 5 is a top View of the switch of Fig. 4 with the cover 6'1 removed.

Fig. 6 is a vertical sectional View of the form of my invention shown in Fig. l as modied by the construction shown in Fig. 3, taken on line E`G of Fig. 7, and Fig. '7 is a sectional elevation taken on the line '1 1 of Fig. 6.

Referring now to Fig. 1 there is indicated at I a switch housing having a bottom` wall 2 through which extends a threaded nipple 3 held in place by a nut 4 thereon. A flexible diaphragm assembly 5 including an upper element 5a and a similar lower element 5b peripherally united thereto is secured to the top of the nipple 3 as by welding and is centrally apertured as shown to receive liquid under pressure through the bore of the nipple. A follower spring 6 is secured by a screw 'l to a block 8 which may be mounted on the housing in any suitable manner and carries on its opposite end a contact block 9 for transmitting the pressure of the diaphragm element 5c to the switch mechanism properly described hereinafter. The bore of nipple 3 is suitably united to a conduit l0 which has a lateral portion Illa terminating in a constant volume heat detector or feeler member I l which in range application is usually placed at the center of the burner plate and in spaced, surrounded relation- Aship with the latter.

Thus, as the temperature of the pan contacting thevfeeler member Il is raised, the fluid therein will be forced through conduit l0 into the diaphragm 5 which is expanded thereby to move the block 9 upwardly. Another branch Ib of the conduit I connects to a bored nipple I2 serving as a mount for a variable volume liquid reservoir such as a centrally apertured, flexible diaphragm I3 which is adapted to be filled with the liquid from conduit Ib. A contact button I4 is mounted centrally of the outer element of diaphragm I3 and is adapted to be laterally displaced by the throw of an eccentric cam I5 mounted on a shaft I6 which is prefer ably driven at a uniform speed by a suitable motor (not shown) to periodically force the liquid out of diaphragm I3 and into diaphragm 5 to thereby move the block 9 upwardly against the influence of follow-up spring 5.

A pin I'I extends transversely of the switch housing I and through the side walls I8 thereof and constitutes a fulcrum for an angular lever block I5 preferably of insulating material and having an arm I9a adapted to contact an adjustable stop preferably in the form of a screw as 25 threaded through a block 2i fixed to the housing I by a screw 22. Lever block I9 serves as a rock.- ing support for a pair of spaced, parallel switch arms 23 secured to the block by screws 23a and having contacts 24 on the ends thereof adapted to be bridged by a bar contact 25 secured by rivet 25a to the end of a generally triangular lever 2S having parallel side walls 26a through which extends the shaft I1 as a pivot.

A generally triangular main lever 28 is provided below the lever 25 and includes side walls 28a of sufficient Width to eclipse the left end portions of walls 26a of lever 26 which portions and side walls are connected by pin 29. It will be noted that Walls 28a are cut away beneath the pin Il l sufficiently to clear the latter as the lever 28 moves vertically. l

The narrowed end of main lever 28 terminates in a vertical lip Z817 for engaging the adjustable temperature cam 3i) mounted on shaft 3l and movable by means of the calibrated knob 32. A centrally depressed portion of main lever 28 is apertured to receive the ball 33 which projects slightly through the former into contact with block Q where it is maintained by follow-up spring 34 fixed to lever 28 at 35. Proper relative positioning of the levers and switch arms is aided by a coil spring 36 centered on a projection on lever 26 and a similar provision on follow-up spring 34; coil spring 31 between lever block I9 and the short arm of lever 26 insures proper contact pressure between contacts 24 and bar 25.

Flexible connectors 38 unite switch arms 23 to pin connectors 39 which extend through the insulated housing closure block Ia; the latter connectors are electrically connected to spaced conductor strips 4U having lug screws 4I for connection in the electric power circuit to the range heater coil.

The operation of this form of my invention is as follows: With the component parts in the relation shiwn in Fig. l wherein diaphragm I3 is filled with fluid in the minimum throw position of the cam I5, feeler member I I is rllle'd with fluid at a relatively low temperature, at least lower than the lowest possible setting of the range cam 30, conduit Ill and its branches are filled; diaphragm 5 hence is in its collapsed position virtually empty of fluid; lip 28h of lever 28 is in engagement with the low temperature portion of cam 30, and with the

contacts

24, 25 in engagement, the stop screw 2D is engaged by a screw driver through an aperture (not shown) in housing I and is retracted just sufficiently to insure that said contacts remain closed as the cam I5 rotates 180 degrees to its high position. As the latter action takes place, the fluid in diaphragm I3 will be forced into diaphragm 5 expanding the latter and thereby raising the left end of lever 28 about the low temperature point of cam 30 as a fulcrum. Since the stop screw 20 in its adjusted position is ineffective to separate switch arms 23 and lever 26, these parts will oscillate as a unit about the pivot pin I1. Thus, the electrical circuit tc the range is maintained as long as the fluid transfer to the diaphragm 5 originates only in the diaphragm I3. However, as soon as the feeler member II heats up due to receiving heat from the heated pan, for example, the expansion of the fluid therein is superposed on that from the diaphragm I3 so that the clockwise arcuate movement of the lever 26 about the pin il exceeds that permitted the lever 23 by the stop screw 2E] and therefore, the

contacts

24, 25 are opened. As the cycling duid returns to the diaphragm I3, lever 26 moves in a counterclockwise direction to close the

contacts

24, 25. It will be observed that rotation of the range cam 3i) to its high temperature position will raise the fulcrum for the main lever 28 so that for the adjustment of stop screw 20 previously described a higher temperature of feeler member II and hence greater expansion of its contained fluid will be required to expand diaphragm 5 suiliciently to separate the

contacts

24, 25 and open the circuit to the heater.

Stop screw 20 is adjusted at the factory as follows: With the power source disconnected from terminals 4I, the low temperature portion of cam 30 engaging lip 28h and the cam I5 stopped in its maximum diaphragm compressing position, the feeler member I I is heated to a temperature slightly below the lowest temperature setting of the temperature adjustment knob r32 and the :screw 20 adjusted until the

contacts

24, 25 are just opening.

The arrangement of the fluid-filled components of the cycling system of Fig. 1 permits the location of the switch and its control knob 32 in the usual control panel position on the range with the da phragm I3, cam I5 and its driving motor located at any convenient and relatively cool place in the range enclosure such as near the base thereof. In the embodiment of Fig. l, furthermore, several diaphragms such as I3 corresponding to the number of burners of the range may be spaced about the cam shaft I6 for compression by the same cam I5.

The arrangement of Fig. l may be modified by employing in lieu of the single chambered dia phragm 5 specifically shown in this figure, a diaphragm having a rigid dividing wall between the similarly shaped upper and lower walls thereby dividing the diaphragm interior into upper and lower separated chambers. Such a, diaphragm is shown in my co-pending application Serial No. 600,862 led June 22, 1945, and entitled: Corrugated Diaphragms now Patent No. 2,487,947. By connecting the branch Illb from the diaphragm I3 into the upper nipple block leading into the upper chamber and connecting the branch IIIa from the feeler member I I to the conduit ID as in Fig. 1 and thence to the lower chamber, a thermally inert fluid might be used as the periodically circulated medium with the consequent advane tages of ambient stability. Also asingle large diaphragm I3 would suffice for several heater plates.

- It will be apparent that various forms Vof feeler member II may be employed in the systemof Fig. 1 subject only to the limitation that .the lic;-

uid"withirr the conduit Illa` be forced to the left orright dependent on the temperature of the feeler member. Thus, the latter may constitute with conduit Ia a continuous chamber filled with thermo-expansive liquid. Alternatively, element III may be filled with such a fluid and the conduit- Illa filled with an ambiently stable, incompressible liquid, the two fluids being separated by' a flexible wall within the element I I as shown in my copending application, Serial No. 599,383 filed June 14, 1945, and entitled Thermal Responsive'Device and Mounting Therefor, now Patent No.- 2,487,946.

Figs. 3, 6 and '7 show a variation of the sys-l tem-of Fig. 1 wherein the cyclic expansion of diaphragm is effected not bythe circulation of 4fluid due to the action of a rotated cam upon a fluid-connected diaphragm, but by the periodic heating and cooling of a fixed volume of fluid contained within the heater and the diaphragm. In these figures the feeler member II has fluid pressure connection to diaphragm 5 through conduit Illa and hence exerts lifting force on block `9 as the temperature of the former is raised. vBetween block 9 and the main lever 22 is provided an `'electrically operated, self-contained cycling unit which includes an elongated supporting lever 42 having a reversely bent portion provided with an electrical contact 43. The opposite end of lever 42 is provided with a block, 44 of -insulating material secured thereto by screws 45 which may extend also through an in sulating and reenforcing plate 46 as shown in Figure 3. Block 44 is laterally apertured to receive'a hinge pin 41 which also extends through similar apertures in a pair of parallels ears 48 closely tting the ends of said block. Ears 43 arefpreferably formed as welded projections of the main lever 28 and serve as a laterally stable mounting for the hinge pin 41 and the confined block 44. Screws 49 extending into the block 44 from above secure an electrical connector plate 53 andan elongated strip of spring metal 5I thereto. Spring strip 5I serves as a support for an -elongated switch arm 52 to which it is riveted at' 53 and permits said arm and its contact 52a to be moved downwardly upon the upward movement of the right end of a loop spring 54, the left end Aof `which is apertured to receive a hook projecting from one end of a slot 55 formed' in switch karin 52. As shown'the apertured right end'of vspring 54 receives the hooked end of a projection 56. carried-by main lever 28 but insulated- -therefrom'by suitable strips 5l. Centrally'of the lever 42 is mounted by means of a nut 59 a stud 58 to the lower end of which is xed a button 6U of suitable rigid insulating material which "is arranged to continuously engage block 9 during the operation of the switch. Resting on a sheet of electrical and thermal insulating `material 6I is a coil of thin-walled tubing made of electrical resistance material having one end lsealed as at 62 and the other end connecting with a suitable central bore in the stud 58. The lower Vwall of a diaphragm 5c is suitably fixed to the top of stud 58 and is apertured inline with `said bore to enable expansion fluid from the latter to enter and expand the diaphragm following connection of leads 59a and 62a to a source of electrical current and a closed condition of'contacts 43v and 52a. The path of the electric current through the

contacts

43, 52a isseen to be through the upper lead to electrical connector plate 50, metal strip 5I, switch arm 52,

contacts

52a,43, lever 42, nut 58, stud 58, the

6 coiled tubing 62 to lead 62a. heater assembly of Figs. 3, 6 and 7 is not claimed herein, in as much as it is fully described and claimed in my copending application Serial No. 600,862 supra.

The upper wall of diaphragm 5c has centrally secured thereto the tapered stud 53a adapte-:l to continuously engage a contact ball 63 such as a vitreous bead, held in a suitably tapered apela ture in the main lever 28 by spring 34. Adjust-' ment screw 64 threaded in a block 65 of insulat ing material secured to the lever 42 serves as lower stop for the spring mounted lever 52 as it snaps to its lower position and provides means for varying the ori-off cycle.

The operation of this embodiment of my invention will, it is thought, be apparent from the foregoing. The diaphragm 5c with its associated heater, lever and. switch elements provides the same cycling deflections for lever 28 as is provided by the driven cam I5 and diaphragm I3 of Fig. 1; adjustment of this form of my inven-` tion is carried out in the same way as in the arrangement shown in Figs. l and 2. Now visualiz.-

ing the complete switch of Fig. 3 as constituting the switch components of Fig. l modified by sube' stituting the Fig. 3 structure for the lever 28 and all parts therebelow, shown also in Figs. 6`and7, it will be apparent that the periodic heating and cooling of diaphragm 5c and its consequent ex pansion and contraction will raise and lower the left end of lever 28 with a periodicity dependent on the heat capacity of the diaphragm and the adjustment of screw 64. This will be evident since the right end of lever 42 is hinged to lever 28 and the distance between the ball 63 and the button 60 increases as the diaphragm 5c expands due to heat produced by the electric current flow-` ing through the tube 62. As the left end of lever 28 is moved upwardly, projection 56 is carried upwardly also to such a point that the loop spring 54 snaps the switch arm 52 downwardly against the stop 64 thus opening the

electrical contacts

43, 52a and allowing the diaphragm to cool and contract and the left end of lever 28 to fall and thus approach the lever 42. cooling has brought

levers

28 and 42 together suiciently to enable the projection 56 to swing the spring 54 to contact closing position, the electric circuit to the tube 62 will again be closed and the cycle will continue indefinitely.

It will be observed that the action of the heat..-` ed diaphragm corresponds to that of diaphragms 5 and I3 and the cam I5 of Fig. l. The fluid pressure transmitted by the feeler element II due to heating expands diaphragm 5 (Fig. 3*) and therefore acts to raise the left end of lever 28 and separate contacts 24-.25 controlling the energization of the range heater element until such contacts are closed for only such a fraction of the operative cycle of the diaphragm 5c,.heater 62 unit as will supply a quantity of heat equal to that dissipated by the cooking vessel, i. e., a stable heat transfer condition. In addition to the elimination of the motor and its .cycling cam I5, the diaphragm I3 and necessary tubing, the Figs. 3, 6 and 7 embodiment is quite compact and is cheaper to manufacture than the first-described form of my invention.

In Figs. 4 and 5 there is shown an extremely compact switch which may be most advantageousf.

The diaphragme.-

When diaphragm' of an adjustable 'stop for varying the relation of the main lever and the range cam. In Figs. 4 and 5 a housing 66 closed by a top wall 61 and end wall 68 of insulating material is secured to the range panel 69 by suitable means such as screws 10. The left end of the housing 66 is provided with an elongated block 1I of insulating material which is held in place by one or more recessed screws 12, and carries on its vertical face a spaced pair of riveted or otherwise connected spring strips 13. A laterally extending, elongated block 14 of insulating material serves to bridge by means of the connecting means 15, the upper ends of the spring strips 13 and carries on its upper surface a pair of spaced contact arms 16, 11 bearing

contacts

18, 19 respectively at the outer ends thereof. A spring contact arm in the form of a flat strip 80 has one end fixed to the top middle portion of the block 1I by means such as screw 6I and extends beneath the block 14 to which it is anchored as by a rivet 82 extending through the strip and block and terminating in a head 83 in a recess provided in the latter. A coil spring 84 disposed between the top wall 61 and the block 14 serves to flex the spring strip 80 downwardly against the vertex of a generally triangular level` 85 the opposite ends 86 of which are snapped over suitable hinge-forming projections 81 extending from the side walls of the housing 66. formed centrally of the lever 85 is adapted to transmit the pressure of spring 84 to the block 93 of diaphragm 5.

The right end of spring strip 80 carries in suitable insulating relationship a bridge member 89 secured thereto at 89a and having contacts 9| adapted to engage

contacts

18, 19, respectively as shown in Fig. 4. Strip 80 is reenforced by a stiff strip 92 riveted thereto at 89a and 93 and having a downwardly offset cani-engaging end which is adapted to be bent upwardly against an `adjustable abutment such as the camV 94 of the range knob 95 by means of the screw 96 threaded through bracket 91 welded to the offset end. Leads 90 connect the ends of switch arms16, 11 with terminal strips 99 as will be apparent from Figures 4 and 5.

Zero adjustment of the switch of Figs. 4 and 5 isI easily made following the procedure already described, the coarse adjustment being effected through positioning of the cam 94 prior to tightening of its retaining screw, followed by necessary movement of screw 9S which is accessible from the switch exterior by means of a suitable opening (not shown) in the housing 66. In operation the cycling travel of the block 98 of diaphragm 5 is such that separation of

contacts

18, 19 and 9| does not result from engagement of the right end of strip 92 with the cam S4, strip 80 merely flexing and the arms 16, 11 moving with it. When the feeler member pressure is superimposed on the cycling pressure, however', the movement of blocl; 98 is sufficient to flex strip 8E to such an extent that the block 14 is movedA upwardly and to the left and the arms 'I6 and 11 are moved away from the strip 89 and strip 92 with consequent opening of the contacts.

The spring-hinged modification of Figs. 4 and 5 provides in compact form the same operating advantages of the Figs. 1 and 2 construction and in addition eliminates the friction, lost motion and misalignment of parts inherent in greater or lessI degree in all pivoted lever systems.

While I have shown and described certain preferred embodiments of my invention, it will be.

A projection 88 8 understood that I do not intend to be limited thereto, but only as may be within the scope of the following claims.

I claim:

l. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a temperature-responsive, hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid filling said enclosure, fiuid circulating means also connected to said chamber means for cyclicly forcing liquid thereinto and withdrawing the same therefrom, and a switch having a pair of contactcarrying arms which are relatively movable to open and close the contacts thereof and one of which arms is disposed in pressure-receiving relation withsaid expansible chamber means and thereby movable with respect to the other of said arms whereby the relative positions of said contacts at any selected instant during the cyclic expansion of said expansible chamber is dependent on the temperature of said temperature-responsive member.

2. The combination set forth in claim l in which there is further provided cam means also disposed in pressure-receiving relation with said expansible chamber means and in pressuretransmitting relation with one of said arms for modifying the effect of said last means upon said last named arm.

3. The combination set forth in claim l in which the fluid displacement characteristics of said fluid circulating means are so chosen with reference to those-of said member and also the volumetric capacity of said diaphragm means that said contacts remain in one of said positions during the cyclic operation of said fluid circulating means alone but move to the other of said positions upon the further expansion of said diaphragm means by heating and resultant expansion of said member.

4. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a temperature-responsive, hollow member coupled to said means to constitute therewith a continuous enclosure, a thermo-expansive fluid filling said enclosure, cyclicly operated fluid circulating means located remote from said first means and fluid coupled thereto for forcing liquid thereinto land withdrawing the same therefrom, and a switch having a pair of contact-carrying arms wihich are mounted for relative movement to effect an open and a closed position, respectively, of said contacts and also movable in unison during a closed position interval of said contacts and one of which arms is disposed in pressurereceiving relation with said expansible chamber means and thereby movable with respect to the other of said arms, the fluid displacement characteristics of said fluid circulating means being so chosen with reference to those of said member and the volumetric capacity of said first means that said contacts remain closed during the operation of said fluid circulating means alone, but move to an open position upon the further expansion of said first means by heating and consequent expansion of said member.

5. The combination set forth in claim 4 in which there is further provided an adjustable abutment also disposed in pressure-receiving relation with said expansible chamber means and in pressure-transmitting relation with one of said arms for modifying the effect of said chamber means upon said one arm.

6. A fluid-pressure cycling system for electric -plurality of pivoted, arms spring-biased to closed-contact position j and a lever carried by one of said switch arms .1heaterscomprising expansible chamber means, a

temperature-responsive, hollow member coupled to Asaid means to constitute a continuous enclothereinto and withdrawing the same therefrom, a contact-carrying switch and disposed between the latter and said chamber means and adapted to transmit the pressure of the latter to said arms to move said arms synchronously` with the operation of said fluid circulating means and to effect opening and clos- Hing of said contacts in response to the temperature'of said member.

uw. A uid pressure cycling System for electric heaters comprising expansible chamberl means, a temperature-responsive, hollow member coupled to saidmeans to constitute a continuous enclosure, a thermo-expansive uid filling said enclosure, uid circulating means also connected to said chamber means for cyclicly forcing liquid Athereinto and withdrawing the sameA therefrom,

a A.plurality of pivoted, contact-carrying switch arms spring-biased to closed-contact position and a lever carried by one of said switch arms and disposed between the latter and said chamber means and adapted to transmit the pressure of the latter to said arms to move said arms synchronously with the operation of said fluid circulating` means and to eiect opening and closing of said contacts in response to the temperature of said member and an adjustable cam adapted to engage one end of said lever to vary `the temperature effect of said member upon the l opening and closing of said contacts.

disposed for relative, contact-opening movement and also unitary, closed-contact movement,

means for effecting said movements including a pressure-transmitting member disposed between said rst means and said arms, and a stationary abutment having an adjustable, intercepting positio'n with respect to said last means and'said arms, whereby the duration of the open-contact condition of said arms will be dependent on the temperature of said member and the position of said abutment.

9. A fluid-pressure cycling system for electric Vvheaters comprising a casing, expansible chamg -ber means mounted therein, a temperature-responsive hollow member outside said casing and `forming with said chamber a fluid-tight enclosure, a thermo-expansive fluid filling the latter, .an adjustable cam and a plurality of contact-car- -rying switch arms mounted in pressure-transmitting relation therewith within said casing and disposed in pressure-receiving relation with said chamber' means, and a cyclicly operated, corrugated diaphragm disposed to exert cyclicly ad- -ditive pressure on said cam and contact-carrying switch arms whereby the contacts of the latter will be cyclicly opened and closed in response to the total pressures exerted by said fluid and said diaphragm.

l0. A duid-pressure cycling system for electric heaters compriing a casing, a corrugated .diaphragm mounted therein, a temperature-responsive, hollow member outside said casing and forming with said diaphragm va fluid-tightenclosure, a thermo-expansive fluid lling the latter, an adjustable cam and a pluralityv of contact-carrying switch arms mounted in pressuretransmitting relation in said casing, a lever having one end fulcrumed on said cam and the other end pivotally connected to one of said arms and in pressure-transmitting relation with said diaphragm and adapted to transmit the pressure of the latter to said cam and arm and a cyclicly operated diaphragm fluid-coupled to said enclosure to exert additive pressure on said first-mentioned diaphragm whereby the contacts of said switch arms will be cyclicly opened and closed in response to the total pressure transmitted by said fluid.

11. A fluid-pressure cycling system for'electric heaters comprising a casing, expansible chamber means mounted therein, a temperature-responsive, hollow member outside said casing and forming with said chamber a fluid-tight enclosure, a thermo-expansive fluid filling the latter, an adjustable cam and a plurality` of contactcarrying switch arms mounted in said casing, a lever having one end fulcrumed on said cam and the other end pivotally connected to one of said arms and disposed in pressure-transmitting relation with said chamber means and adapted to transmit the pressure of the latter to saidcam and arm, an expansible chamber lled with Aa thermo-expansive fluid and disposed between said first chamber and said lever, and cyclicly energized, electrical heating means for said last chamber whereby the additive pressures of said chambers will be transmitted to said switch arms to cyclicly open and close the contacts thereof- 12. A huid-pressure cycling system for electric heaters comprising a casing, expansible chamber means mounted therein, a temperature-responsive, hollow member outside said casing and forming with said chamber a fluid-tight enclosure, a thermo-expansive fluid lling the latter, an adjustable cam and a plurality of contact-carrying switch arms mounted in said casing', a lever having one end fulcrumed on said cam and the other end pivotally connected to one of said arms and disposed in pressure-transmitting relation to said chamber means and adapted to transmit the pressure of the latter to said cam and arm, an expansible chamber filled with a thermoexpansive fluid and disposed between saidrst chamber and said lever, a tubular heater of electrical resistance material located beneath said chamber and forming a continuous enclosure therewith, a thermo-expansive fluid llingsaid enclosure and an electrical circuit for said heater which is cyclicly energized thereby for producing a cycling pressure in said last chamber which is added to that of the first chamber -tov cyclicly open and close the contacts carried by said switch arms.

13. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a temperature-responsive, hollow member .coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid filling said enclosure, fluid circulating means also connected to said chamber means fOr cyclicly forcing fluid thereinto and withdrawing the same therefrom, a plurality of contact-carrying switch arms arf ranged to be moved in unison to maintain the l l closed condition of said contacts in response to the cyclic expansion of said chamber means by said circulating means or relatively to each other to open said contacts when said chamber means further expands due to the attainment of an elevated temperature in said hollow member and an adjustable abutment disposed in the path of movement of one of said arms for blocking the movement of the latter to establish an opencontact position from which the remaining arms f are moved upon the further expansion of said chamber.

14. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a

temperature-responsive, hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid filling said enclosure, fluid circulating means also connected to said chamber means for cyclicly forcing iluid thereinto and withdrawing the same therefrom, e

a plurality of contact-carrying switch arms arranged to be moved in unison to maintain the closed condition of said contacts in response to the cyclic expansion of said chamber means by said circulating means or relatively to each other l to open said contacts when said chamber means further expands due to the attainment of an elevated temperature in said hollow member, an adjustable abutment disposed in the path of movement of one of said arms for blocking the latter to establish an open-contact position from which the remaining arms are moved upon the further expansion of said chamber means, and adjustable means carried by said one arm for deforming the latter to vary its interval of blocking by said abutment.

15. A fluid-pressure cycling system for electric heaters comprising eXpansible chamber means, a temperature-responsive hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid. filling said enclosure, fluid circulating means also connected to said chamber means for cyclicly forcing fluid thereinto and withdrawing the same therefrom, a support bearing a plurality of normally disposed spring strips, a second support carried by said strips, a plurality of contact-carrying switch arms disposed on either side of said second support and arranged to be moved in unison to maintain the closed condition of said contacts or relatively to each other to open said contacts and an adjustable abutment disposed in the path of movement of one of said arms for blocking the latter to thereby open said contacts upon the attainment of an elevated temperature in said hollow member.

16. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a temperature-responsive, hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid filling said enclosure, fluid circulating means also connected to said chamber means for cyclicly forcing fluid thereinto and withdrawing the same therefrom, a support bearing a plurality of normally disposed spring strips, a second support carried by said strips, a plurality of contact-- carrying switch arms disposed on either side of said second support and arranged to be moved in unison to maintain the closed condition of said contacts or relatively to each other to open said contacts, an adjustable abutment disposed in the path of movement of one of said arms for blocking the latter to thereby open said contacts upon the attainment of an elevated temperature i2 in said hollow member, and adjustable means carried by said arm for deforming the latter to vary its interval of blocking by said abutment.

17. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a temperature-responsive, hollow member forming with said chamber a fluid-tight enclosure, a thermo-expansive fluid lling the latter, a support having a plurality of normally disposed spring strips, a second support carried by said strips, a plurality of contact-carrying switch arms disposed on either side of said second support and arranged to be moved in unison to maintain the closed condition of said contacts or relatively to each other to open said contacts and an adjustable abutment disposed in the path of movement of one of said arms for blocking the latter to thereby open said contacts upon the attainment of an elevated temperature in said hollow member.

18. A duid-pressure cycling system for electric heaters comprising expansible diaphragm means, a temperature-responsive, hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid filling said enclosure for transmitting pressure to said means upon heating of said member, uid circulating means also connected to said diaphragm means for cyclicly forcing fluid thereinto and withdrawing the same therefrom.. a switch including a plurality of relatively movable, contact-carrying arms having a closed contact position and an open contact position, spring means disposed to urge said arms into one of said positions and means disposed between said diaphragm means and said arms for transmitting pressure from the former to the latter for moving said switch arms into the other of said positions in response to heating of said member.

19. A duid-pressure cycling system for electric heaters comprising expansible diaphragm means, a temperature-responsive, hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive uid filling said enclosure for transmitting pressure to said means upon heating of said member, fluid circulating means also connected to said diaphragm means for cyclicly forcing fluid thereinto and withdrawing the same therefrom, and a switch including a plurality of relatively movable, contact-carrying arms having a closed contact position and an open contact position, spring means disposed to urge said arms into closed Contact position and means disposed between said irst means and said arms for transmitting pressure from the :former to the latter for moving said arms to open contact position in response to heating oi said member.

20. A fluid-pressure cycling system for electric heaters comprising expansible chamber means, a temperature-responsive, hollow member coupled to said means to constitute a continuous enclosure, a thermo-expansive fluid filling said enclosure, fluid-circulating means also connected to said chamber means for cyclicly forcing liquid thereinto and withdrawing the same therefrom, a plurality of pivoted, contactcarrying switch arms spring-biased to closed contact position, and a lever disposed between one of said arms and said chamber means and adapted to transmit the pressure of the latter to said arms to move said arms Asynchronously with the operation of said fluid-circulating means and to eiect opening and closing of said 13 contacts in response to the temperature of said member.

21. A fluid-pressure operated, adjustable switch comprising a housing, an expansible chamber having a conduit adapted to be connected to an external source of fluid pressure, an adjustable abutment carried by said housing and spaced from said chamber, an elongated, contact-carrying switch arm having one end resiliently mounted with respect to said housing and remote from said abutment and having an opposite end portion adapted to be intercepted by the latter, said portion being adjustably deformable toward and away from said abutment and independently thereof, said arm having also an intermediate portion disposed in pressure receiving relation with said chamber, and a second contact-carrying switch arm resiliently mounted with respect to said housing and movable from a closed-contact position with said first arm to an open contact position away from the latter as said chamber expands and said rst arm moves to its abutment-intercepted position.

JURG A. SENN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,975,851 Kimball Oct. 9, 1934 1,976,843 Eskin Oct. 16, 1934 1,981,282 Smith Nov. 20, 1934 2,006,178 Piron June 25, 1935 2,091,734 Himes Aug. 31, 1937 2,150,674 Dudgeon Mar. 14, 1939 2,224,552 Sickinger Dec. 10, 1940 2,256,840 Haines Sept. 23, 1941 2,273,734 Pearce Feb. 17, 1944 OTHER REFERENCES Journal of the American Chemical Society, vol. 42, Jan. 1920, pages 60-68.