US2254687A - Thermostat - Google Patents

Description

Sept. 2, 1941. 1 KOCI 2,254,687

`THERMOSTAT Original Filed Sept. lO, l1955 2 Sheets--Sheetl l L. J. KOCl THERMOSTAT sept. 2, 1941.

Original Filed Sept. l0, 1935 2 Sheets-Shea*I 2 Patented Sept. Y jl i' Flexible Shaft Comp ration of Illinois any, Chicago, Ill., a corpooriginal applications september io, less, semi Y No. 39,957, and June 26, 1939, Serial No. 281,080. Divided and this application September 1, 1939,v

Serial No. 293,028

4s claims. (ci. 20c-122) This invention relates to thermostats, and has special reference to a thermally operated timer mechanism.

An object of the invention is the provision of a generally improved thermostatlc timer.

Another object of the invention is the provision of a thermostat structure having a novel arrangement for compensating for change in the ambient temperature.

A still further object of the invention is the provision of a thermostat timer having improved means for adjusting the time interval.

I have also aimed to provide a snap acting thermostat formed of bimetal together with improved means for causing the strip to move from one to the other of its stable positions.

A still further object of the invention is the provision of a thermostat havingI a novel frame structure.

Other objects and advantages will appear from the following description and the accompanying drawings, in which- Figure 1 is a side elevation partly broken away showing the thermostat construction;

Fig. 2 is a longitudinal section through the thermostat frame; I

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 is a section on the line 4--4 of Figure 1;

Fig. 5 is a view of one end of the thermostat;

Fig. 6 is a view of the switch;

Fig. 7 is a side view of a modified form of the invention;

Fig. 8 is a section on the line 8-8 of Fig. 7;

Fig. 9 is a section on the line 9-9 of Fig. 8, but with the cam adjusted to a position diametrically opposite from that shown in Fig. 8; and l Fig. 10 is a wiring diagram of the thermostats shownin Figs. 1 to 8, inclusive, showing one way in which the thermostat mechanism may be connected into a circuit.

This is a division of my copending applications Serial No. 39,957, led September 10, 1935, entitled Toaster and the like, now -Patent No. 2,191,- 221, issued April 16, 1940, and Serial No. 281,- 080, led June 26, 1939, entitled Toaster.

The invention is directed to a thermal timer adapted to be connected into an electrical circuit in a number of different ways and for a number of different uses, as is well known in the art, one such waybeing shown in Fig. 10 wherein the numeral II designates a source of current connected to a load as indicated, the circuit including a switch I2 and a resistance I3, the latter serving to heat the thermally responsive element of the timer.

Referring to the form shown in Figs. l to 6,

inclusive, the numeral I4 designates a U-shaped frame having upstanding arms I5 and I8 at its ends and a central portion formed by side walls I1 and I8 (Fig. 4) and a top portion I9. The upper surface 2| of the central portion I4 is plain throughout a substantial portion of its length but has recesses 22 and 23 at the ends thereof. This 'top surface is preferablyy formed of high heat conductive material such, for example, as aluminum, and preferably the .entire frame structure may be formed from aluminum or similar metal. Secured in the frame adjacent the end -portion I5 is a bearing member 24 provided with a groove 25 substantially in the plane of the surface 2l, the bearing member 25 being of steel or similar hardened material. A ply metal strip, in this instance a bimetal strip 26, has one end seated in the groove 25 and extends longitudinally of the surface 2I, the opposite end thereof being seated in a groove formed in a spring metal strip 21. It will be seen that this provides pivotal bearings for both ends of the strip which renders its action more accurate and at the .same time givesk a minimum opportunity for thermal loss from the strip when it occupies its upper position and gives excellent contact with the cooling surface in the lower position. The upper end of the strip 21 is secured to the arm. I6 adjacent its upper ends by means of a bolt 2l, while the lower end of the strip extends through an opening 29 in the top I9 into. the space between the walls I1 and I8. A coil spring 3| of the type having a high deection to force ratio is positioned in the space between the walls I1 and I8, as best shown in Figs. 2 and 4. One,

nut 32 beyond this strip. The end of the pin 32y is slotted as shown at 34 for the purpose of turning the end of the pin with respect to the nut and thereby adjusting the tension on the spring 3l. The opposite end of the spring is looped over the hooked end 35 of an arm 38 of a bell crank lever 31 pivotally supported on a pin 38 seated in the arm I5 of the frame, the opposite arm 39 of the levez` riding on a cam 4I supported on a -pln 42 also seated in the arm I5 and carrying an adjusting knob 43 for the purpose of rotating the cam 4I and thereby changing the tension of the spring 3l. The cam 4I, the face of which is shown in Fig. 3, has an arcuate cam surface 44 bounded on its ends by stops 48 and 46 adapted at opposite ends of its rotation to abut against the arm 3! of the bell crank lever and thcreby terminate rotation of the knob and limit the tensional adjustment on the spring 6I. The spring Il and spring strip 21 i'unctionto apply a compressive force on the bixnetal strip 26 tending to cause it to normally occupy the position shown in Figure 1, which in this instance is the "Cold position of the strip, the arching of the strip being limited by a stop finger 41 attached to the wall I6 of the frame.

The bimetal strip 26 is preferably, though not necessarily, given a top surface coating to enhance the radiant heat absorption characteristics of the surface. This may be done by heavily oxidizing the surface or by imparting thereto a dull black coating of foreign matter such as a heat resisting lacquer, paint or the like. In this case the coating must have sufllcient elasticity to stand repeated bending without checking off. Such materials are well known in the art. The bimetal strip may also be preformed as to curvature, as, for example, I prefer to form the strip so that it is arched slightly between its ends at normal atmospheric temperatures, and by so forming the strip I am enabled to control the temperature at which it returns from its heated position shown in Fig. 2 to its cool position shown in Figure 1.

Because of the compressive force exerted against the strip 26, when the strip is heated to a predetermined temperature as determined by the shape of the strip and by the compressive force exerted thereon, it moves with a snap action from the position shown in Figure 1 to the position shown in Fig. 2. It will be observed that in the position of Fig. 2 the bimetal strip is in surface contact with the surface 2l throughout the full length of the surface 2l and throughout a substantial portion of the length of the strip. Since the surface 2l is of highly heat conductive material, the heat is rapidly drained away from the bimetal strip until it reaches a predetermined lower temperature, at which point it moves back to the position shown in Figure 1 with a snap movement. To facilitate this action the central portion i4 of the frame is provided with a plurality of spaced ribs 46 positioned on the walls I1 and I6 and acting to facilitate the dissipation of heat from the surface 2i. Where the timer is confined within an enclosure this action may further be facilitated by providing slots 49 in the bottom I of the enclosure (Fig. 4) so as to confine the ow of air past the ribs 46, since the flow of air will thus be generated in response to the action of the heating element, as will presently appear.

The bimetal plate 26 is heated by means of a resistance member 52 constituting a heating element for the blade which may be connected into an electric circuit as shown in Fig. 10, or otherwise, as is known in the art, in such way that electric current flows through the heating element at the prescribed time and thereby serves to heat the bimetal blade in a certain ratio or proportionality with some other action. The heating element 52 may advantageously be partly enclosed by a reflector 53 which acts to reflect the radiant heat downward against the bimetal blade and to partially shield the blade and the heating element from extraneous drafts.

A lever 54 is rotatably mounted on a pin 55 secured in the central portion of the frame, a. spring 56 normally tending to rotate the lever in a clockwise direction facing Figs. 1 and 2. The lever 54 has a laterally disposed finger 51 at one end adapted to project inwardly under the bimetal strip 26 (Fig. 4) in a position to be actuated in response to the movement of the strip and thereby rotate the lever 54. The opposite end of the lever 54 has a notch 56 adapted to receive a laterally disposed end 59 of a lever 6| pivoted at 62 to a fixed portion 62 of the mechanism with which the timer is associated. The lever 6i has a shoulder 64 on one edge thereof adapted to engage an obliquely extending spring strip support 65 for movable contacts 66, which movable contacts are positioned to engage stationary contacts 61 to complete the circuit through the load or through the heating element 52.

It will be seen that when the lever 6I is rotated about the pin 62 in a clockwise direction, the shoulder 64 engages the spring support 65 moving the contacts 66 against the contacts 61 and with the circuit shown in Fig. 10, thereby closing the circuit through the heating element 52. Upon such movement the lever 54 moves clockwise so that the laterally disposed end 56 of the lever 6l moves into the slot 58 thereby retaining the lever 6l and the contacts 66 in the closed position. Heating of the strip 26 by the heating element 52 proceeds until the predetermined temperature is reached, whereupon the strip snaps down to the position shown in Fig. 2. Toward the latter part of this movement the strip engages the finger 51, rotating the lever 54 and thereby lifting the notch 56 away from the laterally disposed portion 56 permitting the lever 6| to move to the position shown in Fig. 2 under the spring tension of the spring support 65, the contacts 66 and 61 simultaneously opening 4and deenergizing the heating element 52. Because of the contact of the strip 26 against the surface 2l, the strip is caused to return to its upper position upon the lapse of a very short period of time, thereby promptly re-positloning the parts for a subsequent timing operation. Attention is directed to the fact that with this arrangement, in every operation subsequent to the first, the strip 26 starts at the same temperature.

It will be seen that with frequent operation of the timer the parts surrounding the strip 26 will assume different temperatures and that these differences in temperatures would affect the timing operations. In order to compensate for these changes I provide a second bimetallic strip 66 having one end supported near the upper end of the arm i6 by means of the screw 28 and depending to a point adjacent to the end of the strip 26. On the lower end of the strip 66 is positioned a threaded sleeve 69 having an adjusting screw 1I therein adapted to project through the strip 66 and at least at times to make contact with the strip 21, its action being to augment the spring 3| and strip 21 in applying pressure to the end of the bimetal strip 26, the pressure thus appliedA varying with the ambient temperature, that is. the temperature of the frame and associated parts, whereby to compensate for such changes in temperature. By this means a desired correction or alteration may be applied to the operating characteristics of the thermostat.

In Figs. 7 to 9, inclusive, I have shown a second embodiment of the invention wherein the iframe structure is very similar to that heretofore described having a central portion 12, upstanding arms 13 and 14, and a top surface 16. The central portion likewise has spaced walls 16 and 11 providing a space for a spring 18, In this instance the space between the outer ends of the walls 16 and 11 is closed by a plate 16 attached to a base 8| by means of screws 82, the base 8| also functioning as a heat dissipating member analogous to the ribs 48. A threaded pin 8l supports one end of the spring 18 and has a nut 84 for adjusting the tension on the spring. As before, one end of the bimetal strip 88 is seated in a notch 88 in a block 81 of steel or other hard material secured in the frame against the arm 13. The opposite end of the bimetal blade is supported on a spring strip 88 attached at its upper end to the upper end of the arm 14 by means of a screw 88, the strip having laterally disposed side edges 8| throughout a substantial portion of its length and a short spring portion 82 adjacent its support, the spring portion 84 giving resiliency to the strip and the sides 8| rendering the strip rigid in its lower portion. The strip has a groove 88 for the reception of the end of the bimetal strip 88 in the areas adjacent the edges thereof, the central portion of the bimetal strip being bent downwardly in a tongue as shown at 84 and extending through an opening 88 in the spring strip 88. Secured to the upper end of the arm 14 by the screw 88 is a second bimetallic strip 88 which extends downwardly beyond the opening 88 and has a screw 81 seated therein adapted to bear against the end of the tongue 84, whereby the bimetallic strip 88 acts to' apply pressure on the end of the bi- -metallic strip v88 and at an angle with respect to the strip. The function of the tongue 84 and the strip 88 is to change the stress on the strip 88 with change in ambient lor mass temperature. As the temperature of the strip 88 increases the strip applies more pressure against the end of the tongue 84 which serves to increase the temperature yat which the strip 85 snaps down and also at which it returns, though not to as great a degree. The increase in temperature at which it will snap down is desirable to compensate for changes in mass temperature, while the eiect in the second position is for the purpose of reducing the time required for the blade to return; in other words, to prevent the cooling or returning time from becoming excessive upon repeated operations of the thermostat. The last result isobtained by applyingv the pressure of the secondary thermostat 88 below the line connecting the two pivot points so that the force thus applied has a substantial lateral component on the strip 85; in other Words, a component acting in the direction of movement of the strip. By varying the angularity of the tongue 84 these effects may be varied as desired. The spring '|8 is attached to the spring strip 88 and functions to apply. the main compressive force to the bimetallic strip 85 in a manner analogous toethat heretofore described. The upper or Cold" position of the bimetal strip 85 is determined by the linger 41, as in the previously described form.

The bimetal strip 85 is heated by means of a coil 88 supported on an insulatorl 88 and electrically and mechanically connected to electrical conductors by means of screws |8| and |82. Supported above and partly enclosing the heating element 88 is a cylindrical shield or reflector |88 comprising a substantial part of a cylinder but having an opening |84 extending longitudinally thereof. The cylinder is pivotally supported on a pair of spaced ears |88 and |88 by means of a pin |81 for rotation of the cylinder about the pin |81. Attached to a stationary portion |88 of the device with which the timer is employed and which also supports the ears |88 and |88 is a spring |88 which acts on a finger pro- 75 Jecting from the cylinder |88. normally urging the cylinder in a clockwise direction facing Pig. 8. This clockwise movement is arrested by a' second ilnger ||2 attached to the cylinder and bearing againstacam ||8 iixedto apin ||4 rotatably supportedin a stationary part of the device and adapted to be actuated by a knob III. The cam III, best shown in Fig. 8, has an arcuate recess ||8 receiving apin ||1 fixed in a stationary part of the device for the purpose of limiting the rotation of the cam. A

A lever ||8 is pivotally supported on theumemberl |88 and is spring pressed to occupy the position shown in Fig. 8, that is, t0 rotate in a counterclockwise direction i facing this gure. One end ||8 of the lever projects to a point below the bimetal strip 88 in a position to be engaged thereby as the strip snaps downward against the surface 18 and to be rotated through a short angularity. The opposite end of the le-v ver ||8 has a notch 2| adapted to receive the end |22 of a switch lever |28, the notch normally retaining the switch lever in the closed position but permitting it to rotate about its pivotal support |24 under the action of a spring |28 when theI end ||8 is depressed. 'Ihe switch lever |23 has a laterally disposed arm |28 to which the spring |28 is attached, and carries movable contacts |21 positioned to engage stationary contacts |28 on a stationary part of the device when the lever is moved to the closed position as shown in Fig. 8. It will be seen that by'rotation of the knob ||8 the cylinder |88 is rotated thereby serving to permit the passage of more or less heat from the coil 88 to the upper surface of the bimetal strip 85, thereby controlling the length of time required for the strip to reach the temperature at which it changes position.

While I have thus described and illustrated specific embodiments of the invention, numerous changes may be made within the spirit of the invention and the scope of the appended claims, in which I claim: l

1. A thermostat comprising a bimetallic element, means for changing the temperature thereoi in one direction for measurement purposes to cause temperature responsive movement in one direction, and means for causing prompt return of the element for a successive measuring movement comprising a heat dissipating body having a cooling surface against which the bimetallic element has surfacecontact substantially along its entire length for rapidly changing the temperature of the element in the opposite direction.

2. .A thermostat comprising a bimetal element, means vfor changing the temperature thereof in one direction for measurement -purposes to cause temperature responsive movement in one direction, means actuated in response to said movement, and means for causing prompt return of the element for a successive measuring movement comprising a heat dissipating body having a cooling surface congruous and in surface contact with a major portion of one side of the bimetal element when the latter is moved in the iirst mentioned direction for rapidly changing the temperature of the velement in the 'opposite tuated in response to said movement, and means for causing prompt return of the element for a successive measuring movement comprising a heat dissipating body having a cooling surface shaped and located so as to be congruous with a large portion of one side surface of the bimetal element and making contact with said surface when the bimetal element moves in snap action in the rst mentioned direction for rapidly changing the temperature oi' the element in the opposite direction.

4. A thermostat comprising a snap-acting bimetal element, means for changing the temperature thereof in one direction for measurement purposes to cause temperature responsive snap acting movement in one direction, means actuated in response to said movement, and means for causing prompt return of the element for a successive measuring movement comprising aheat dissipating contact member having a cooling surface shaped and located so as tobecongruous with and to contact said element in response to the first-mentioned snap acting movement to rapidly change the temperature of the element in the opposite direction, said cooling surface serving as a stop to limit the snap acting movement in the first mentioned direction.

5. A thermostat comprising in combination a thermally responsive strip subjected to a combined primary and a secondary temperature effeet, means for supporting the ends of said strip, means for exerting a compressive force on said strip through said supports to arch the strip to cause the same to move with a snap action under thermal changes, and means for varying said compressive force in response to the secondary o! said temperature effects to vary the operating characteristics of the strip in response thereto.

6. A thermostat comprising in combination a thermally responsive strip subjected to a combined primary and a secondary temperature e!- iect, means for supporting the ends of said strip, means for exerting a compressive force on said strip through said supports to arch the strip to cause the same to'move with a snap action under thermal changes, means for varying said compressive force in response to the secondary of said temperature eiiects to render` the movement of the strip solely responsive to the primary temperature eiect, and means independent of said last mentioned means for varying said compressive iorce to vary the degree of said primary temperature effect required to move said strip.

7. A thermostat comprising in combination a frame comprising a central portion having a plane face on one side thereof and a channel in the opposite side, and arms at the ends thereof, a thermally responsive strip, means on said arms substantially in the plane of said face for pivotally supporting the ends of said strip, and a coiled spring in said channel for applying a compressive force on said strip between said supports to arch said strip away from said face to cause the strip to move thereagainst with a snap action under thermal change in one sense, and means for maintaining said face at a temperature diierent in the opposite sense from that of said strip to cause the same to promptly return to the Aarched condition.

8. A thermostat comprising in combination, a frame comprising a central portion having upstanding arms, one of said arms having a notch, a resilient metal support positioned on the other arm and extending toward said central portion having a notch adjacent its free end, a bimetal strip having its ends seated in said notches for pivotal movement, a tension spring acting on said support to compress said strip to arch the same to cause it to move with a snap action under thermal changes, and manually operable means for changing the tension oi said spring to vary the temperature required to move said strip.

9. A thermostat comprising in combination a thermally responsive strip subjected to a combined primary and secondary heating effect, means for pivotally supporting the ends of said strip, means for exerting a compressive force on said strip through said supports to arch the strip to cause the same to move with a snap action under thermal changes, and means for applying to the strip a force in a direction parallel with the movement thereof and proportional to said secondary temperature effect to modify the temperature required to move said strip.

10. A thermostat comprising in combination a thermally responsive strip, means for pivotally supporting the ends of said strip, means for exerting a compressive force on said strip through said support to arch the strip and cause the same to move with a snap action under thermal changes, means for heating said strip to cause the same to move, and a metal surface of high heat absorbing power positioned to contact said strip in response to said movement for rapidly cooling the same to promptly return the strip.

11. A thermostat comprising in combination a thermally responsive strip, means for pivotally supporting the ends of said strip, means for exerting a compressive force on said strip through said support to arch the strip and cause the same to move with a snap action under thermal changes, means for heating said strip to cause the same to move, a metal surface oi high heat absorbing power positioned to contact said strip in response to said movement for rapidly cooling the same to promptly return the strip, switch means for controlling said heating means, and means responsive to the movement of said strip for actuating said switch means.

12. A thermostat comprising in combination a thermally responsive strip, resilient means acting on the end of the strip for compressing the strip to arch the same between its ends and cause it to move with a snap action under thermal changes, a heating element spaced from and extending longitudinally of said strip, and a reflector and shield of arcuate cross-section positioned above and partly enclosing said element to reflect heat from said element against the strip, and means for relatively adjusting said reflector and shield with respect to said heating element and said strip to vary the heat transfer to said strip.

13. An atmospheric thermostat comprising in combination a thermally responsive strip. resilient means acting on the ends of the strip for compressing the strip to arch the same between its ends and cause it to move with a snap action under thermal changes, a heating element spaced from and extending longitudinally of said strip, and a coating of heat absorbing material which has a high absorption co-eiiicient with respect to infra red radiation on the side of said strip adjacent to said heating element whereby to obtain more eiiicient and more uniform heat trans- Ier from said element to said thermally responsive strip and to obtain a longer time constant in the snap action functioning of said strip.

14. A thermostat comprising in combination a thermally responsive strip, resilient means acting on the end of the strip for compressing the .strip to arch tl same between its ends and cause it to muv' :ith a snap action under thermal changes. a heating element spaced from and extending longitudinally of said strip, a reflector and shield of arcuate cross-section partly enclosing said elementV to reflect heat from said element against the strip, and means for rotating said shield to control the supply of heat to the strip whereby to control the time for effecting said snap action in response to the rotative setting of the reflector and shield.

15. A thermostat comprising in combination a thermally responsive strip, means for pivotally supporting the ends of said strip, means for exerting a compressive force on said strip through said support to arch the strip and cause the same to move with a snap action under thermal changes, a heating element spaced from said strip to heat the same for thermally responsive movement, and temperature responsive means for applying to the strip a compressive force in response to the ambient temperature to modify the thermally responsive movement of the strip in response to changes in ambient temperature.

16. A snap actionv thermostat comprising a thermally responsive strip arched under a compression force and adapted to have snap action movement in response totemperature change, and a cooling surface having surface contact with a side of the thermally responsive strip over a major area thereof to effect rapid cooling of said strip at one extreme position to which the vstrip has been moved by snap action.

17. A snap acting thermostat comprising a thermally responsive strip arched under lengthwise compression and adapted to have snap action movement in response to temperature change, and a comparatively flat cooling surface arranged to have surface contact with a side face of the strip substantially co-extensive with the length thereof to limit the snap action movement of the strip in one direction and to effect rapid cooling of the strip.

18. A`snap acting thermostat comprising a thermally responsive strip arched under lengthwise compression and adapted to have snap action movement in response to temperature change, and a heat dissipating body of high thermal conductivity having a cooling surface of substantial area arranged in congruous relation with a side face of the strip for surface contact therewith to limit the snap action movement thereof in one direction and eilect rapid cooling thereof.

19. A thermostat comprisingua thermally responsive-strip, a fixed pivot supporting one end of the strip, a resilient member supporting the other end of the strip and adapted to hold the strip arched under a compression force so that the strip is adapted to have snap action movement in opposite directions in response to temperature change, a heat dissipating body having a cooling surface of substantial area located so as to have surface contact with said strip substantially throughout its length when the strip has been moved by snap action in one direction, whereby to effect rapid cooling of the strip and snap action movement thereof in the opposite direction.

20. A thermostat as set forth in claim 19, including a coil spring extending lengthwise of said heat dissipating body and connected at one end to the resilient member, and manually adjustable means at the opposite end of said body connected to the opposite end of said spring for varying the compression force against the strip.

21. A thermostat as set forth in claim 19, including a second thermally responsive strip acting through said resilient means for varying the compression force against the first mentioned thermally responsive strip.

22. A thermostat as set forth in claim i9, including a second thermally responsive strip arranged for imparting compression force to the first mentioned strip supplemental to that imparted by said resilient means.

23. A snapl action thermostat comprising a thermally responsive strip arched imder a compression force and adapted to have snap action movement in lresponse to temperature change, and a second thermally responsive strip arranged to act against one end of the first mentioned strip to vary said compression force.

24. A snap action thermostat as set forth in claim 23, including manually adjustable means for varying the compression force against the first mentioned thermally responsive strip independently of the second mentioned thermally responsive strip.

25. A snap action thermostat as set forth in claim 23, in which the compression force of the second thermally responsive member is applied so as to have a substantial lateral component in its effect on the ilrst mentioned thermally responsive strip.

28. A snap action thermostat as set forth in claim 23, in which the end of the first mentioned thermally responsive strip against which the second thermally responsive strip acts is laterally offset from a line connecting the ends of the first strip. i

2'1. A snap action thermostat as set forth in claim 23, in which the second thermally responsive `strip is arranged to apply increasing compression to the first strip as the temperature of the second strip increases to thereby increase the temperature at which the snap action movement of the first strip is effected, and in which the coaction between the strips is such as to reduce the time required for the first strip to return in a reverse snap acting movement.

28. A snap acting thermostat comprising a primary thermally responsive strip arched under lengthwise 'compression and adapted to have snap action movement in response to temperature change, and a secondary thermally responsive strip arranged to apply increasing lengthwise compression to the primary strip as the temperature of the secondary strip increases to thereby increase the temperature at which the snap action movement of the primary strip iS effected.

29. A snap acting thermostat comprising a primary thermally responsive strip arched under lengthwise compression and adapted to have snap` action movement in response to temperature change, a cooling surface arranged to have surface contact with said strip substantially coextensive with the length thereof to limit the snap action movement of said strip in one direction and to eect rapid cooling of -said strip and reverse snap action thereof, and av secondary thermally responsive strip arranged to apply increasing lengthwise compresslon to the primary strip as the temperature of the secondary strip increases to thereby increase the temperature at which the snap action movement of the primary strip is effected.

30. A snap acting thermostat as set forth in claim 29, in which the secondary strip is so arranged in coaction with the primary strip as to reduce the time required for the primary strip to return in a reverse snap acting movement.

31. A snap action thermostat comprising a thermally responsive element arched under a compression force and adapted to have snap action movement in response to temperature change, and a second thermally responsive element arranged to act upon the first mentioned thermally responsive element to impart an increasing degree of compression force thereto in proportion to increase of temperature of the second thermally responsive element to effect snap action movement of the first mentioned thermally responsive element in one direction.

32. A snap action thermostat as set forth in claim 31, in which the second thermally responsive element is arranged to impart compression force to the flrst mentioned thermally responsive element in such manner as to reduce the time required for the latter element to return in a snap action movement in the opposite direction.

33. A snap action thermostat comprising a thermally responsive strip arched under a compression force and adapted to have snap action movement in opposite directions in response to temperature change, and a second thermally responsive strip arranged to influence the temperature at which the ilrst mentioned strip operates, unequally in each of the opposite extreme positions of the first mentioned thermally responsive strip.

34. A snap action thermostat comprising a thermally responsive strip arched under a compression force and adapted to have snap action movement in opposite directions in response to temperature change, and a second thermally responsive strip arranged to influence the temperature at which the first mentioned strip operates so as to have a minimum effect on the first thermostat when it has moved by snap action to one extreme position and a maximum effect when it has returned by snap action to the opposite extreme position.

35. A thermostat having a thermally responsive element subjected to a combined primary and secondary temperature effect and arranged to move in a snap action under thermal changes, and means for applying to the strip an increasing force responsive to increase in temperature of said secondary effect to thereby increase the temperature at which the thermally responsive element moves in said snap action.

36. A thermostat as set forth in claim 35, in which the force applied in response to the secondary effect serves to reduce the time required' for the thermally responsive member to return from said snap action movement,

. 37. A thermostat comprising a thermally responsive strip subjected to a primary temperature effect, a. device adapted to be actuated by movement of the strip under temperature change, a second thermally responsive strip responsive to a secondary temperature effect and arranged so that by change in its temperature it will apply an increasing compression force against the flrst strip lengthwise thereof to thereby increase the temperature at which the flrst strip actuatessaid device.

38. A snap action thermostat comprising a thermally responsive strip arched under a compression force and adapted to have snap action movement in response to temperature change, a cooling surface arranged to have surface contact with the strip substantially throughout its length to limit said snap action movement and to effect rapid cooling of the strip and return thereof in a snap action movement in the opposite direction, a heating element extending lengthwise of the strip in juxtaposition thereto, and an adjustable reflector arranged to connne heat emanating from the heating element and to transmit heat rays thereof to the strip throughout a substantial length thereof in accordance with the adjustment setting of the reflector.

39. A thermostat as set forth in claim 38, in which the reflector is so shaped and arranged as to serve as a movable shield or baille, and means for adjusting the reflector to effect fast heating in one position and slow heating in another position in the latter of which the reflector serves to baille or intercept certain of the heat rays.

40. A snap action thermostat comprising a thermally responsive strip arched under a compression force and adapted to have snap action movement; in response to temperature change, a cooling surface arranged to have surface contact with the strip substantially throughout its length to limit said snap action movement and to effect rapid cooling of the strip and return thereof in a snap action movement in the opposite direction. a heating element in juxtaposition to said strip, a reflector arranged t0 confine heat emanating from the heating element and to transmit heat rays to the strip, and an adjustable baille arranged to intercept certain of said heat rays and adjustable to vary the heat transmission to the strip.

41. In combination, a thermostat, a heating element in juxtaposition to the thermostat, a reflector surface for reflecting radiant rays from the heating element to the thermostat, and a baille surface relatively adjustable with respect to the heating element to intercept certain of said radiant rays.

42. A thermostat adapted for operating in the air for the control of heating appliances and the like comprising, in combination, a thermally responsive member, a heating element for supplying heat to said member by convection and radiation, a device arranged to be actuated by said member in successive timed operations in response to temperature change of said member, and a coating on the face of said member exposed to said radiant heat comprising heat absorbing material having a high absorption co-eicient with respect to infra-red radiation, whereby to obtain increased efficiency of heat transfer by radiation between the heating element and the thermally responsive member, and whereby to obtain more uniform and improved response characteristics of the thermostat in its control of said device.

43. A thermal timer having, in combination, thermostat means responsive to radiant heat for terminating the timing interval,a heating element for supplying said heatl to the thermostat, and a reflector for reflecting heat from said heating element to said thermostat means adjustable to cut off a portion of said reflected radiant heat to vary the intensity of heat reflected to lsaid thermostat means and thereby vary the duration of the timing interval.

44. A thermal timer having, in combination, a primary thermally responsive strip supported at its ends and stressed by a compression force to move with a snap action to determine a timing interval in response to temperature change, and a secondary thermostat means positioned to apaction between cold and hot positions, said strip having a projection diverging laterally therefrom adjacent one end, and a secondary thermostat responsive to the mass temperature of the device positioned to apply a thrust to said projection supplemental to said stress and directly proportional to increasing temperature of said device to cause said snap action to occur at correspondingly increased temperatures.

LUDVIK J. KOCI.

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