US2773649A

US2773649A - Circuit-controlling device

Info

Publication number: US2773649A
Application number: US411396A
Authority: US
Inventors: Adolph J Hilgert
Original assignee: Milwaukee Gas Specialty Co
Current assignee: Milwaukee Gas Specialty Co
Priority date: 1954-02-19
Filing date: 1954-02-19
Publication date: 1956-12-11
Anticipated expiration: 1973-12-11

Description

Dec. 11, 1956 A. J.H1LGERT J CIRCUIT-CONTROLLING DEVICE Filed Feb. 19, 1954 2 Sheets-Sheet l 6' i a 1 A4 United States Patent C CIRCUIT-CONTROLLING DEVICE Adolph J. Hilgert, Milwaukee, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis., a corporation of Wisconsin Application February 19, 1954, Serial No. 411,396

21 Claims. (Cl. 236-21) This invention relates to improvements in circuitcontrolling devices and more particularly to condition responsive circuit controlling devices of improved dual construction.

In certain condition controlling apparatus, for example apparatus for controlling the temperature within a space heated by burning fuel, it is desirable to provide a cycling type valve for controlling the flow of fuel to the burner in response to normal fluctuations in the condition, for

example temperature, and to provide a resettable or noncycling type valve in the fuel stream ahead of the aforementioned cycling valve for shutting off the fuel flow to the burner in response to an extreme condition, for example temperature.

In an apparatus of the aforementioned character it is also desirable to provide a cycling type circuit-controlling device for controlling the cycling valve, and a non-cycling or resettable circuit-controlling device for controlling the non-cycling valve.

It is a general object of the present invention to provide an improved dual circuit-controlling device adapted for use in a condition controlling apparatus of the aforementioned character and comprising a cycling condition responsive circuit-controlling device responsive to normal fluctuations in the condition and a resettable circuit-controlling device responsive to an extreme condition, there being condition sensing means common to both of said circuit-controlling devices for sensing the condition to which said devices are responsive.

Another object of the invention is to provide an improved dual circuit-controlling device of the class described wherein each of the individual circuit-controlling devices thereof comprises an expansible and contractible bellows or enclosure, said enclosures being in communication with each other, and there being a common expansible and contractible fluid fill for both of said bellows.

A more specific object of the invention is to provide an improved control apparatus of the aforementioned character wherein the fill for said bellows is sub-atmospheric in character, whereby in the event of a leak in either of' said bellows, both of said bellows are expanded by atmospheric pressure to disengage the contacts of both of said circuit-controlling devices.

Another object of the invention is to provide an im-' Another object of the invention is to provide an im-' proved dual circuit-controlling device of the character described wherein the individual circuit-controlling devices take the form of thermostats and are incorporated in a resilient, energy-storing portion.

ice

unitary assemblage provided with manually operable control point adjustment means for the cycling thermostat and means including a manually engageable drop-outindicating and reset button for the non-cycling thermostat.

Another object of the invention is to provide an improved dual thermostat assemblage which is simple in construction, easy to disassemble and reassemble, and otherwise well adapted for the purposes described.

Other objects and advantages of the invention will become apparent as the description proceeds, reference being had to the accompanying drawings illustrating one complete embodiment of the invention, and wherein like characters of reference indicate the same parts in all of the views. In the drawings:

Figure 1 is a semi-diagrammatic fragmentary elevational view of the improved fuel control system as applied to a water heater;

Figure2 is an enlarged vertical sectional view taken through the dual thermostat assemblage of the improved control system;

Figure 3 is an elevational view of the dual thermostat assemblage as viewed from the left in Figure 2, parts being broken away and shown in section;

Figure 4 is the electrical circuit wiring diagram of the improved control system; and I Figure 5 is a perspective view of one of the contacts of the non-cycling thermostat embodied in the improved control system.

Referring more particularly to Figure 1 of the drawing, the form of the invention selected for illustration is shown associated with a fluid fuel burning water heater 10 having a metal tank 11 in which water is heated by heat from a main burner 12 therebelow. The tank 11 may be encased in an insulating jacket 13 having a metal outer shell 14. An ignition or pilot burner 15 is mounted in coacting relationship with the main burner 12.

The illustrated fuel control system controls the flow of fuel to the main burner 12 and pilot burner 15 and comprises a cycling type electromagnetically operated valve 16 and a manually resettable electromagnetically controlled safety shut-off valve 17, both interposed in the fuel supply pipe 18 for the main burner 12. The

electromagnetic valves

16 and 17 are operable on an electric current of small magnitude, for example the non-arcing current available from a thermoelectric generator 19 positioned adjacent the pilot burner 15 and subject to the heat of a flame directed thereat from said pilot burner. current supplied to the

valves

16 and 17 by the generator 19 is under the control of the improved dual thermostat assemblage 20 to be described in detail hereinafter.-

The safety shut-off valve 17 may be of any well known type having an electromagnet 21 provided with insulated terminals 22 and 23, said valve having an armature 21 coacting with the electromagnet 21 and connected to a valve member 24 which is held open as long as the electromagnet is energized by current from the generator -19. A spring 24' biases the valve member 24 toward closed position to shut off the flow of fuel to both the main burner and pilot burner 15 when the electromagnet 21 is deenergized. Once closed, the valvevmember 24 remains closed until subsequently opened by actuation.

of a reset mechanism including a manual reset stem 25 and a flow interruption disk 26, the latter permitting fuel flow to the pilot burner '15 through a supply pipe 27, and preventing fuel flow to the main burner 12 during a resetting operation.

The valve 16 comprises an operator including an electromagnet 28 having terminals 29 and 30. An armature 31 coacts with the electromagnet 28 and is carried by a pivotally mounted arm 32 which preferably has a The arm 32 also car- The I ries a valve member 33 which controls the flow of fuel through the valve 16, there being means, for example a spring 34, biasing the arm 32 in a direction to close the valve member 33 and move the armature 3-1 away from the electromagnet 28. Energization of the electromagnet 28 by current from the thermoelectric generator 19 while the valve member 33 is closed causes initial movement of the armature 31 toward the electromagnet with storage of energy in the arm 32. When the energy stored in the arm 32 plus the pull on the armature 31 exerts a force on the valve member 33 greater than the forces tending to hold said valve member closed, i. e., fuel pressure plus the bias of the .spring 34, said valve member is moved to the open position shown. n deenergization of the electromagnet 28, the spring 34" plus the fuel pressure pivots the arm 32 to move the armature 31 away from the electromagnet and simultaneously move the valve member 33 to closed position. It is apparent that the valve 16 cycles in response to the energization and deenergization of the electromagnet 28, thereby permitting or preventing the flow of fuel to the main burner 12. v

Referring to Figures 2 and 3, the dual thermostat as,- semblage 20 may comprise a generally cup-shaped base casting 35 having fixed therein an annular ring 36 provided with upstanding l -sh aped lugs '37. The base casting 35 may be mounted on the casing of the valve 16 as shown, or in any other suitable location. The opcrating mechanism of the assemblage 20 is removably mounted on the base casting 35 and comprises a mounting plate 38 having depending lugs 39 which are removably interlocked with the lugs 37 by a turning movement of said plate. The operating mechanism may be locked in operative position by a screw 98 threaded into an lip-standing lug 99 on the mounting plate 38 and having its head portion positioned in a transverse bore in the wall of the base casting 35 as shown in Figure 3. Screw 98 prevents turning movement of the mounting plate 38 and thereby prevents disengagement of the

lugs

37 and 39. The mounting plate 38 may be formed of a single piece or may be of the laminated construction shown, wherein the laminations are sealingly connected, as by welding or the like. The mounting plate 38 is formed withspaced apertures 41 and 42 and provides a support for a cycling type thermostat '39, as well as a manually resettable non-cycling thermostat 40.

The illustrated thermostat 39 comprises a hermetically sealed expansible and con-tractible enclosure in the form of a bellows 43 having a fixed end Wall or base plate 44 and a movable end wall 45. The base plate 44 ha a portion of reduced diameter positioned in the mounting plate aperture 41 and is sealingly fixed to said mounting plate, as by soldering or the like. The base plate is centrally bored, as at 46, and is counterbored, as at 47. A fixed contact member 48 extends within the bore 46 and through a glass seal 49, terminating within the bellows 43 in a rounded tip 54]. The opposite end of' the contact member 48 is fixed to a terminal tip 51 insulatably mounted in the coun'terbore 47 as shown. Contact tip 50 coasts with a movable contact member 2- carried on the inner surface of and in circuit with the bellows end wall 39. i

The thermostat 40 comprises an expansible and contractible hermetically sealed enclosure in the form of a movable bellows end wall 55 and carries thereon, within the bellows 53, a movable contact member 62 and a nut '63. As shown in Figure 5, the contact 62 is generally U-shaped with the end portions of the arms thereof turned inwardly toward each other. The closed end of the U-shaped contact 62 is apertured, as at 63, to receive the screw 61, said closed end also being 'arcuate in conformation, being curved toward the open end of said contact as shown. The contact 62 is preferably made of resilient material which coacts with the ball-shaped contact tip 59 to effect a releasable frictional clamping engagement as well as an electrical engagement with said tip, The nut 63 may be formed with opposite axially extending peripheral slots 64 for receiving the arms of the con-tact 62 and preventing relative rotation of said nut and contact. It is apparent that by tightening the screw 61, the arcuate closed end of the contact 62 tends to be flattened out, and the ends of the arms of contact 62 tend to be drawn together, thereby increasing the frictional engagement of said arms with the contact tip 59. This provides factory adjustment of the temperature control point of the thermostat 40. After this adjustment is made, the head of the screw 61 is sealed to the end wall s s lde i As shown in Figures 2 and 3, the lower lamination of the mounting plate 38 is depressed downwardly as at 65 to provide, with the upper lamination of said plate, a transverse passage which communicates at its inner end with passages 66 and 67 formed respectively in the bellows base plates 54 and 64 opening into the interior of the

bellows

43 and 53 respectively. The outer end of the mounting plate portion 65 sealingly receives a capillary tube 68 which extends to a temperature sensing bellow-s 53. similar to the bellows 43 but somewhat longer- I in axial dimension. The bellows 53 has a fixed base plate or end wall 54 and an opposite movable end wall 55'. Base plate 54 has a portion of reduced diameter positioned within the mounting plate aperture 42, and is provided with a bore 55 and counterbore 56. A fixed contact member 57 extends within the'bore 55 and through a glass seal 58 into the bellows 53, terminating into a ball-shaped tip 59. The opposite end of the contact member 57 is fixed to a terminal tip 60 insulatably mounted in the counterbore 56.

A screw 61 extends through a central aperture in the bulb 69 positioned in good heat conducting contact with the outer surface of the water heater tank 11 as shown in Figure 1.

The bellows 43 and 53, tube 68 and bulb 69 all contain a common sub-atmospheric volatile fluid fill whose vapor pressure increases and decreases in response to increases and decreases in temperature. The fill is also of a type which will not react with the bellows contacts to form a film thereon or in any way increase the contact resistance. While the fills used in different applications may vary in acordance with the temperatures encountered in said applications, a satisfactory fill for the water heater application illustrated is normal propyl alcohol. Normal propyl alcohol has a boiling point of 207 F. and therefore provides a sub-atmospheric fill at water heater operating temperatures. Thus, in the event of a leak anywhere in the fluid system, i. e., in either of the bellows, in the tube 68 or in the bulb 69, atmospheric pressure enters the system and expands both bellows to separate the contacts therein.

Refe n to re 3. a gen r l u-shapsd ack 0 i fixed to h mcum s at a S s l d. straddle h el ws .3 and The upp Wall of the bracket 70 is formed with a central aperture 71 (Figure 2),, and the end ofsaid wall adjacent the bellows 5.3. has pressed therefrom a pair of depending lugs 72 and 73. The upper wall of the bracket '70 is also formed with an access aperture 74 coaxially alined with the bellows 43. Fixed within the aperture 71 is a bearing ee e .5. an c a ab v m u ted on aid. en s e s. a smpsr t rccon r l oin j s m n kn b t6 i h The sk r of the s nera ly Q n hane as h w knob 76 is positioned within the base casting 35 as shown,

bracket 70 and bellows 43 and 53 as shown.

surface 77.

A spring lever 78 is suitably fixed to the bracket 70,

as by screws 79, and extends diametrically across the rnovable wall '45 of the bellows 43 and through an open ing 80 in the side of the bracket '76, said lever having its free end portion 81 in engagement with the cam surface 77. A factory temperature control point adjustment screw 82 is carried by the spring lever 78 and coaxially engages the movable bellows end wall 45. The mounting of the screw 82 may include a generally C-shaped clip 83 having an internally threaded neck portion 84, said clip having end portions extending around the side edges of the spring arm 78 to fixedly confine a friction washer, for example a nylon washer 85, between the portion 84 and the arm 78. The washer 85 has a diameter to frictionally engage the screw 82 and maintain the latter in the selected position of adjustment. Access to the screw 82, for factory adjustment thereof, is afforded by an aperture 86 formed in the knob 76 and alignable with the bracket aperture 74. The force exerted on the bellows end wall by the screw 82 can be readily varied by manually rotating the knob 78. Through the cam surface 77, this rotation moves the free end of the spring lever 78 toward or away from said bellows end wall. The control point temperature for a given position for the knob 76 is indicated, for example, by a pointer on the body casting 35 and cooperating indicia on the outer surface of the knob 76 both as shown in Figures l and 3.

A cap 87 is centrally apertured and has a tubular portion 88 extending into the bearing sleeve as shown. The cap 87 is also provided with an inturned peripheral lip 89 positioned within a circumferential groove 90 formed in the knob 76.

As shown most clearly in Figure 2, a lever 91, which may be channel shape for the major portion of its length, is pivotally mounted at one end on a pin 92 supported by and extending between the lugs 72 and 73. The lever 91 extends diametrically across the movable bellows wall 55 and the under side of an intermediate portion of said lever is engageable with the rounded head of the screw 61 as shown. Adjacent its opposite end, the lever 91 is formed with an apertured, generally hemispherical, depending offset 93 which is positioned substantially coaxial with the bearing sleeve 75. Axially slidably positioned within the bearing sleeve 75 and the tubular portion 88 of cap 87 is a manually engageable dropout inclicator and reset button 94 having a diameter substantially equal to tthe inner diameter of the tubular portion 88. The button 94 is provided with an axially depending stem 95 having a rounded lower end portion seated in the offset portion 93, as shown, and provided with an integral guide pin portion 96 extending through the aperture of said offset portion. To prevent removal of the button 94 from the sleeve 75, said button is provided with a portion 97 having a diameter substantially equal to the inner diameter of the bearing sleeve 75 and therefore somewhat greater than the inner diameter cap portion 88. The button 94 and lever 91. are movable from the solid line position shown in Figure 2 to the released or dropout-indicating position shown in dot and dash lines in said figure on release of the ball-shaped contact tip 59 by the friction contact 62.

The

contacts

52 and 62 of the

bellows

43 and 53 are grounded to the body of the cycling valve 16 via said bellows, the mounting plate 38 and the base casting 35. Electrical connections to the terminal tips 51 and 60, and hence to

contacts

48 and 57, are provided by

spring contacts

101 and 102 which are insulatably mounted within the base casting 35 and which effect low resistance connections with said terminal tips when the mounting plate 38 is in the locked position shown. A pair of

terminal lugs

103 and 104 are insulatably positioned on the under side of the base casting 35. The lug 103 being connected in circuit with the spring connector 102 for example by rivets 105 insulatably extending through suitable apertures in the base casting 35. Similarly the spring connector 101 is connected in circuit with the terminal lug 104 by rivets 106 which also extend insulatably through suitable apertures in the base casting 35.

The electrical circuit for the illustrated fuel control apparatus will be most easily understood by referring to Figures 1 and 4 wherein it will be noted that one terminal of the thermoelectric generator 19 is connected by a conductor 105 to the terminal 23 of the safety shutoff valve 17. A conductor 106 connects the terminal 30 of the cycling valve operator in circuit with the conductor 105. A conductor 107 connects the terminal 22 of the safety shut-off valve 17 in circuit with the terminal lug 103 and hence with the contact 57 of the thermostat 40. A conductor 108 connects the terminal 29 of the cycling valve operator in circuit with the terminal lug 104 and hence with the contact 48 of the thermostat 39. As previously mentioned, the

contacts

52 and 62 of the

thermostats

40 and 39 respectively are grounded to the body of the valve 16. A conductor 109 connects the other terminal of the thermoelectric generator 19 in circuit with said valve body and hence with said

contacts

52 and 62.

It is apparent from the wiring diagram shown in Figure 4 that the thermostat 40 and the safety shut-01f valve 17 are connected in series circuit with each other and with the thermoelectric generator 19. The thermostat 39 is connected in series circuit with the operator of the valve 16 and with the thermoelectric generator 19, said thermostat and operator also being connected in parallel circuit relation with the thermostat 40 and the valve 17 as shown. With this arrangement, the valve 16 can be cycled under the control of the thermostat 39 without causing drop-out of the valve 17. On the other hand, interruption of the current flow to the safety shutoff valve by the thermostat 40 effects closure of said valve and percent shut-ofi of the fuel.

The thermostat 39 is calibrated for response to normal temperature fluctuations, Whereas the thermostat 40 remains in the position shown in Figures 2 and 4 during said normal fluctuations. The thermostat 40 is calibrated for response to extreme or high limit temperatures. On occurrence of an unsafely high temperature sensed by the bulb 69, expansion of the fluid fill exerts an expanding force on the bellows 53 suflicient to cause release of the contact 59 by the friction contact 62, thereby interrupting the current flow to the safety shut-off valve 17 and causing closure of the latter to provide the aforementioned 100 percent shut off of the fuel.

Expansion of the bellows 53 sufficient to cause release of the contacts 59 and 62 also moves the lever 91 and button 94 to the dot and dash line positions shown in Figure 2. Thus, the button 94 moves from an unobtrusive position where its outer end is substantially flush with the cap 87, to a projecting drop-out-indicating position. If desired, the outer wall of the button 94 may be colored similarly to the cap 87, with the side walls of said button having a contrasting color. It is apparent that the contrasting color is visible when the button 94 is in drop-out-indicating position, but is not visible when the button is in its normal depressed or reset position.

The bellows 53 has an inherent bias which holds the contacts 62 and 59 apart once the latter are released,

even though the temperature sensed by the bulb 69 may subsequently drop to normal or below. Thus, once the button 94 is moved to the drop-out-indicating position, it stays in that position and indicates to a service man that shut-off of the fuel flow was caused by the occurrence of an extreme temperature sensed by the bulb 6,9 or by a leak in the fluid fill system, and not by pilot burner outage. To reset the contact 62 to the contact 59, it is only necessary to depress the projecting reset button 94 to the solid line position shown in Figure 2, thereby returning the lever 91 and contact 62 to the solid line positions shown in said figure.

To set the illustrated control system into operation after complete shut-down and after resetting the contacts of the thermostat 40 by depression of the reset button .94, the e et-stem .5 of the sa e y h -s valve is depressed to open the valve member 24 and close the flowinterrupter disk 26. Fuel can now flow through the pilot fuel supply pipe ,27, and on ignition, said fuel heats the thermoelectric generator 19, causing the latter to generate current for energizing the electromagnet 21 of the safety shut-oif valve 17. Energization of the electromagnet 21 holds the valve 24 in open position and permits release of the reset button 25 and retraction of the flow interrupter disk 26 to open position so that fuel can flow to the valve 16. If the thermostat 3% is calling for heat, the thermoelectric generator 19 energizes the electromagnet 28 of the valve 16, causing opening of said valve and thus permitting fuel flow to the main burner '12. Thereafter the valve 16, is cycled by the thermostat 39 in response to temperature changes sensed by the bulb 69.

In the event of pilot burner outage, the generator 19 cools, and the electromagnets 21 and 28 are deenergized, whereupon the

valves

16 and 17 close. Closure of the valve 17 shuts off all fuel flow, and said valve remains closed until subsequently opened by depression of the reset stem 25 preparatory to relighting the pilot burner.

The incorporation of the cycling thermostat 39 and the non-cycling thermostat 40 in the single assemblage 20, and the utilization of the single temperature sensing bulb for both of said thermostats not only affords extreme compactness, but it also greatly simplifies installation procedures. The cycling thermostat 39 is characterized by high sensitivity and low differential and provides low resistance slow-make and slow-break contacts which may function as a variable resistance in the thermoelectric circuit. In view of the small electric energy in the thermoelectric circuit, the valve 16 may be cycled in response to temperatnre changes by varying the contact pressure between the contact tip 50 and the contact 52. Since the contacts of the

thermostats

39 and 40 are encapsulated, the contact resistance in said thermostat remains constant for a given contact pressure. Thus, the aforementioned high sensitivity and low differential are retained by the thermostat 39 throughout its life.

The inherently small differential of the thermostat 39 affords the illustrated control apparatus with greater sensitivity than can be afforded by conventional immersion type temperature control devices, and the fact that it is unnecessary for any portion of the improved apparatus to come in contact with the Water in the tank 11 avoids such problems as electrolysis or corrosion with which immersion type units must contend.

The specific illustrations and corresponding description are used for the purpose of disclosure only and are not intended to impose unnecessary limitations on the claims, or to confine the patented invention to a particular use. While the illustrated embodiment of the invention is shown applied to a water heater, it is obvious that its use is not limited thereto. Various changes and modifications may be made without departing from the spirit of the invention and all of such changes are contemplated as may come within the scope of the claims.

What is claimed as the invention is:

l. A condition responsive circuit-controlling device for low power circuits, comprising: A first hermetically sealed enclosure expansiblc and contractible in response to normal fluctuations in the condition; cooperating contacts encapsulated within said enclosure and relatively movable with expansion and contraction of said enclosure; a second hermetically sealed condition responsive expansible and contractible enclosure; relatively movable contacts encapsulated within said second enclosure, said last-mentioned contacts being normally in a first position and being movable by expansion of said second enclosure to a second position in response to a predetermined extreme n the condition; and a common condition sensing element for both of said enclosures.

2.1 1 a condition controlling apparatus having electromagnetic control means and electrical circuit means therefor: .A cycling condition responsive circuit-controlling device in said circuit means for controlling said electromagnetic control means and hence said apparatus in response to fluctuations in the condition; a resettable Condition responsive circuit-controlling device in said circuit means for overcalling said cycling circuit-controlling device and taking over the control of said apparatus in response to a predetermined condition, said resettable circuit-controlling device requiring resetting before control of said apparatus can be returned to said cycling circuit-controlling device; and common condition sensing means for both of said circuit-controlling devices.

.3. In a condition controlling apparatus having electromagnetic control means and electrical circuit means therefor: A cycling condition responsive circuit-controlling device in said circuit means for controlling said electromagnetic control means and hence said apparatus in response to fluctuations in the condition, said cycling circuit-controlling device comprising relatively movable cooperating contacts encapsulated within an hermetically sealed expansible and contractible enclosure; and a resettable condition responsive circuit-controlling device in said circuit means for overcalling said cycling circuitcontrolling device and taking over the control of said apparatus in response to a predetermined condition, said resettable circuit-controlling device comprising relatively movable cooperating contacts encapsulated with'n an hermetically sealed enclosure and requiring resetting before control of said apparatus can be returned to said cycling circuit-controlling device; a temperature sensing bulb in communication with said first and second enclosures; and a temperature responsive expansible and contractible fluid fill common to all of said enclosures.

4. In a condition controlling apparatus having electro magnetic control means and electrical circuit means therefor: A cycling condition responsive circuit-control ling device in said circuit means for controlling saId electromagnetic control means and hence said apparatus in response to fluctuations in the condition, said cycling circuit-controlling device comprising relatively movable cooperating contacts encapsulated within an hermetically sealed expansible and contractible enclosure; and a resettable condition responsive circuit-controlling device in said circuit means for overcalling said cycling circuit-controlling device and taking over the control of said apparatus in response toa predetermined condition, said resettable circuit-controlling device comprising relatively movable cooperating contacts encapsulated within an hermetically sealed enclosure and biased toward a first position, said contacts being movable against said bias to a second position, one of said contacts frictionally engaging the other to releasably hold said contacts in said second position when moved thereto; a condition sensing bulb in communication with said first and second enclosures; and a condition responsive expansible and contractible fluid fill common to both of said enclosures and said bulb, said fill being responsive to a predetermined change in the condition to expand said enclosure and disengage said contacts, said contacts requiring resetting before control of said apparatus can be returned to said cycling circuitcontrolling device.

5. A resettabl e condition responsive circuit-controlling deviGQ comprising: A hermetically sealed enclosure expansible and contraetible in response to changes in the condition; cooperating contacts operatively associated with said enclosure and biased toward a first position, said contacts being movable against said bias to a second position, one of said contacts frictionally engaging the other to releasably hold said contacts in said second position when moved'thereto against said bias; a condition responsive expansible and contractible fluid fill for said enclosure responsive to a predetermined change in the condition to expand said enclosure and disengage said frictionally engaged contacts; and means for resetting said contacts to said second position after movement thereof to said first position.

6. A resettable condition responsive circuit-controlling device, comprising: A hermetically sealed enclosure expansible and contractible in response to changes in the condition; cooperating contacts encapsulated within said enclosure and biased toward a first position, said contacts being movable against said bias to a second position, one of said contacts frictionally engaging the other to releasably hold said contacts in said second position when moved thereto; and a condition responsive expansible and contractible fluid fill for said enclosure responsive to a predetermined change in the condition to expand said enclosure and disengage said contacts; and means for resetting said contacts to said second position after movement thereof to said first position, said means comprising a manually engageable reset and indicator member movable to an indicating position on movement of said contacts to said first position in response to expansion of said enclosure.

7. A resettable condition responsive circuit-controlling device, comprising: A hermetically sealed enclosure expansible and contractible in response to changes in the condition; cooperating contacts operatively connected to said enclosure and biased toward a first position, said contacts being movable against said bias to a second position, one of said contacts frictionally engaging the other to releasably hold said contacts in said second position when moved thereto; a condition responsive expansible and contractible fluid fill for said enclosure responsive to a predetermined change in the condition to expand said enclosure and disengage said contacts; and adjustment means comprising means for varying the amount of friction between said contacts when the latter are in said second position for adjustment of the degree of change in the condition required to disengage said contacts.

8. A resettable condition responsive circuit-controlling device, comprising: A hermetically sealed enclosure expansible and contractible in response to changes in the condition; cooperating contacts encapsulated within said enclosure and biased toward a first position, said contacts being movable against said bias to a second position, one of said contacts having shoulder means, and the other of said contacts comprising at least one resilient arm having a portion frictionally engaging said shoulder means to releasably hold said contacts in said second position when moved thereto; a condition responsive expansible and contractible fluid fill for said enclosure responsive to a predetermined change in the condition to expand said onclosure and disengage said contacts; and adjustment means comprising means connected to said arm for varying the amount of friction with which said arm engages said shoulder means when said contacts are in said second position for adjustment of the degree of change in the condition required to disengage said contacts.

9. A condition-responsive circuit-controlling device, comprising: At least two pairs of cooperating circuitcontrolling contacts; first condition-responsive actuating means affording one of said pairs of contacts circuitcontrolling movement in response to normal fluctuations in the condition; second condition-responsive actuating means afiording the other of said pairs of contacts circuitcontrolling movement in response to an extreme in the condition; and condition sensing means common to both of said actuating means for sensing the condition to which said actuating means are responsive.

10. A condition-responsive circuit-controlling device, comprising: At least two pairs of cooperating circuitcontrolling contacts; first condition-responsive actuating means afiording one of said pairs of contacts circuitcontrolling movement in response to normal fluctuations in the condition; second conditionresponsive actuating means affording the other of said pairs of contacts circuitcontrolling movement in one direction only and only in response to an extreme in the condition; condition sensing means common to both of said actuating rrieans foi sens ing the condition to which said actuating means are responsive; and means for resetting said other contacts after movement thereof by said second actuating means in response to an extreme condition.

11. A dual temperature thermostat, comprising: At least two pairs of cooperating circuit-controlling contacts; first temperature-responsive actuating means affording one of said pairs of contacts circuit-controlling movement in response to normal temperature fluctuations, said first actuating means comprising an hermetically sealed enclosure expansible and contractible in response to said temperature fluctuations; second temperature-responsive actuating means affording the other of said pairs of contacts circuit-controlling movement in one direction only and only in response to an extreme temperature, said second actuating means comprising an hermetically sealed expansible and contractible enclosure provided with a movable wall having a first position and movable in response to said extreme temperature to a second position; a temperature sensing bulb communicating with both of said enclosures for sensing the temperature to which said actuating means are responsive; and a thermally expansible and contractible fluid fill common to both of said enclosures and said bulb.

12. A circuit controlling device, comprising: A first expansible and contractible enclosure having a movable wall; a second expansible and contractible enclosure having a movable wall; a bracket; a bearing sleeve carried by said bracket; a knob rotatably mounted on said bearing sleeve; means coacting with said knob and with the movable wall of the first enclosure for applying a variable force to the latter; and an indicating member having a portion movable within said bearing sleeve between first and second positions, said member coacting with the movable wall of said second enclosure and being movable to said second position by predetermined expansion of said second enclosure.

13. A circuit controlling device, comprising: A first expansible and contractible enclosure having a movable wall; a second expansible and contractible enclosure having a movable wall; a bracket; a bearing sleeve carried by said bracket; a knob rotatably mounted on said bearing sleeve; means coacting with said knob and with the movable wall of the first enclosure for applying a variable force to the latter; and an indicating button axially slidable within said bearing sleeve between a depressed position within said sleeve and a drop-out indicating position wherein a portion of said button projects a substantial distance from one end of said sleeve, said button coacting with the movable wall of said second enclosure and being movable to said drop-out indicating position by predetermined expansion of said second enclosure.

14. A circuit controlling device, comprising: A first expansible and contractible enclosure having a movable wall; a second expansible and contractible enclosure having a movable wall; a bracket; a bearing sleeve carried by said bracket; a knob rotatably mounted on said bearing sleeve; means coacting with said knob and with the movable wall of the first enclosure for applying a variable force to the latter; and a drop-out indicating and reset button having a portion movable within said bearing sleeve between a depressed position within said sleeve and a drop-out indicating position wherein a portion of said button projects a substantial distance beyond one end of said sleeve; connections between said button and the movable wall of said second enclosure for moving said button to drop-out indicating position on predetermined expansion of said second enclosure, said connections also effecting contraction of said second enclosure on manual resetting of said indicating button to said depressed position. I

15. In a condition controlling apparatus having electro magnetic control means and electrical circuit, means therefor: A cycling condition responsive" circuit controlling device in said circuit means for controlling said electromagnetic control means and .hence said .apparatus ,in responsetofluctuations in the condition, said cycling ,circuit controlling device comprising relatively movable cooperating contactsand an hermetically sealed expansible and contractible enclosure foractuating said contacts; and a resettable condition. responsive circuit controlling said resettable circuitcontrolling device comprising relatively movable cooperating contacts and an hermetically sealed enclosure for actuating said contacts in response to. said predetermined condition, said resettable circuit controlling device requiring resetting before control of .the apparatus can be returned to saidcycling circuit controlling device; means affording communication between saidfirst and second enclosures; and a condition responsive vexpansible and contractible fluid fill common to both enclosures, said fill at normal operating temperatures having a vapor pressure which is less than atmospheric pressure, whereby on occurrence of a leak in either of saidvenclosures entry of atmospheric pressure into both of said enclosures causes both of said enclosures to expand and move the contacts therein away from each other.

16. A condition responsive circuit controlling device,

comprising: A first hermetically sealed enclosure expansible and contractible in response to normal fluctuations in the condition; cooperating contacts relatively movable with expansion and contraction of said enclosure; a second hermetically sealed condition responsive expansiblc and contractible enclosure; relatively movable contact .means operatively coacting with said second enclosure and including releasable means for holding said contact means in a first position when moved thereto, said holding means being released and said contact means being movable to a second position by expansion of said second enclosure in response to a predetermined extreme in the condition; and a common conditionsensing element for both of said enclosures.

17. A resettable condition responsive circuit control- .ling device, comprising: .Contact means including relatively movable cooperating contact members biased toward separated relation and movable against said bias into'engagement, said contact means also including releasable friction means for holding said contact members in engagement when moved thereto against said bias; condition responsive actuating means for effecting release .of said friction means and movement of said contact members .to separated relation in response to a predetermined :change in the condition; and means for resetting said contact. members into engagement after movement thereof to separated relation in response to said condition change.

18. A resettable condition responsive circuit controlling evice, comprising: Contact means including relatively movable cooperating contact members biased toward separated relation and movable against said bias into engagement, said contact means also including releasable 'friction means for holding said contact members in engagement when moved thereto against said bias; condition responsive actuating means for effecting release of said friction means and separation of said contact members in response to a predetermined change in the condition, and adjustment means for varying the amount of friction in said friction means and thereby'the degree of change in the condition required to separate .said contact members.

19. In a condition controlling apparatus having electromagnetic control means and electrical circuit means therefor: A cycling condition responsive circuit controlling device in said circuit means for controlling said electromagnetic control means and hence said apparatus in response to fluctuations in the condition, said cycling circuit controllingdevice comprising relatively movable cooperating contacts and first condition responsive actuating means affording said contacts circuit controlling movement in response to normal fluctuationsiin the con- .dition; a resettable condition responsive circuit. controlling device in said circuit means for overcalling said cycling circuit controlling device and taking over the'control of said apparatus in response .to a predetermined condition, said resettable device comprising contact means .including relatively movable cooperating contact memtact members .to said first position in response toan extreme in the condition, said contact members requiring resetting to said second position before control of Said apparatus can be returned to said cycling circuit controlling device; and condition sensing means common to both of said actuating means for sensing the condition to which saidactuating means are responsive.

20. In a condition controlling apparatus having electromagnetic control means and electrical circuit means therefor: A cycling condition responsive circuit controlling device in said circuit means for controlling said electromagnetic control means and hence said apparatus in response to fluctuations in the condition, said cycling circuit controlling device comprising relatively movable cooperating contacts and an hermetically sealed expansible and contractible enclosure for actuating said contacts; a resettable condition responsive circuit controlling device in said circuit means for overcalling said cycling circuit controlling device and taking over the control of said apparatus in response to a predetermined condition, said resettable circuit controlling device comprising relatively movable cooperating contacts biased toward a first position and movable against said bias to a second position, one of said contacts frictionally engaging the other to releasably hold said contacts in said second position when moved thereto; an hermetically sealed expansible and contractible enclosure for actuating said last-mentioned cooperating contacts; means afiording communication between said enclosures; and a condition responsive expansible and contractible fluid fill common to both of said enclosures, said fill being responsive to a predetermined change in the condition to expand said last-mentioned enclosure and disengage said frictionally engaged contacts, said disengaged contacts requiring resetting before control of said apparatus can be returned to said cycling circuit controlling device.

21. .A circuit controlling device, comprising: A first movable member; a second member movable between first and second positions; a bearing having an opening therein; a knob rotatably mounted on said bearing; means coacting with said knob and with said first movable member for applying a variable force to the latter; and an indicating member coacting with said second movable member and having a portion movable within said bearing opening from a first to a second position in response to movement of said second movable member from its first to its second position.

References Cited in the file of this patent UNITED STATES PATENTS