Thermostatically operated valve

Abstract

Claims

Oct. 5, 1954 v w E, JENKINS 2,690,875 THERMOSTATICALLY OPERATED VALVE Filed June 20, 1951 E w 2% 3 V v II ISLE-- INVENTOR. May/vs E. JE K/NS Patented Oct. 5, 1954 UNITED STATES FATENT OFFICE THERMGSTATICALLY OPERATED VALVE Application June 20, 1951, Serial No. 232,637 14 Claims. 1 The invention relates to thermostatically operated valves and particularly to those adapted to control the flow of fuel to a burner in a heat appliance in accordance with temperature changes. Thermostatically controlled valves of the type described have, among perhaps others, fallen into two general classes; in one, known generally as a graduating type control, the motion transmitting means used between the thermostat and the valve provides a direct, although sometimes amplified, movement effecting a gradual opening and closing of the valve in accordance with decreasing or increasing temperatures respectively. This type of control provides excellent regulation of temperature and is also usually relatively positive and fool-proof in its construction. Its principal disadvantage is in throttling down the fuel flow at and adjacent to closed position which produces instable operation of the burner and low burner efiiciency. Also in cracking open of the valve from its closed position there may be insumcient fuel flow for ignition by the customary pilot burner and a dangerous accumulation of fuel, and backfiring and the like may occur. To avoid the disadvantages of this type of control it has been proposed to remove the automatic graduating action adjacent the shutoff position by including in the control a constantly operating bypass passage which insures at all times the flow of a predetermined minimal amount of fuel. Where such a bypass is used the control is rendered semiautomatic, that is it responds over a predetermined temperature range but does not shut on the fuel flow completely even though the temperature of the medium being heated rises to an inordinate point. The second type of control, sometimes referred to as snap acting avoids the disadvantages of the graduating type control above discussed by the interposing in the motion transmitting means of a snap acting device which provides an abrupt snap action opening and closing of the valve at the limits of the temperature range for which the device is set. In this type of control the flow is either fully on or fully off. Also snap acting devices heretofore available have required an appreciable temperature change to effect their operation. Accordingly, the regulation of temperature is somewhat poorer with this type of device, which is called upon to function at frequent intervals as the terminal temperatures are reached, but it does have the advantage of insuring optimum burner efiiciency and fully automatic operation. In accordance with the present invention and as a principal object thereof, I provide a thermostatically operated valve which combines the inherent advantages in both the graduating and the snap acting types of mechanisms whereby excellent regulation of the controlled temperature, snap acting opening and closing of the valve and complete automatic operation are obtained. Another object of the present invention is to provide in a thermostatically controlled valve having the combination operation above described, an improved form of snap acting mechanism which may be operated upon the application thereto of a substantially reduced force dilierential, whereby the mechanism may be caused to respond over a much shorter temperature range than heretofore. A further object of the present invention is to provide a valve of rugged construction coupled with excellent sensitivity which is composed of a minimum number of sturdily formed parts arranged for minimum wear and deterioration whereby the mechanism will provide positive and fool-proof service over a very long period of time. A still further object of the invention is to provide a valve of the character described which may be quickly and conveniently set for a desired temperature range. The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is understood, however, that variations in the showing made by said drawing and description may be adopted within the scope of the invention as set forth in the claims. Referring to said drawings: Figure 1 is an end elevational view of a thermostatically controlled valve constructed in accordance with the present invention. Figure 2 is a longitudinal sectional view of the valve of Figure 1 and is taken substantially on the plane of the line 2-2 of Figure 1, and is shown with the valve in maximum open position. Figure 3 is a fragmentary enlarged section of the device similar to Figure 2 but showing the main valve closed and the bypass valve open. Figure 4 is a view similar to Figure 3 but with both valves closed. Figure 5 is a perspective view of the snap acting device used in the mechanism. The thermostatically controlled valve of the present invention consists briefly in the combination of the valve mechanism movable to fully open, partially open and fully closed positions, a thermostat movable in accordance with temperature changes, and motion transmitting means connecting the thermostat and valve mechanism and providing a graduating proportional movement of the former between its fully and partially open positions in response to a first range of movement of the thermostat, and further providing an abrupt snap action movement between the partially open and fully closed positions of the valve mechanism in response to a second and contiguous range of movement of the thermostat. Somewhat more specifically, the foregoing is accomplished by the provision within the motion transmitting means of a pair of relatively movable sections which are connected to an over-center snap acting device, the assem bly moving as a unit between the fully and partially open positions of the valve mechanism and providing relative snap action between the sections in the movement of the valve mechanism between its partially open and fully closed positions. Additionally, for convenience of manufacture, precision of operation and control, I prefer to divide the valve mechanism into a pair of valves mounted in parallel flow control position and which provide when both open, one closed, and both closed, the fully and partially open and fully closed positions respectively of the valve mechanism. In the present embodiment, one of such valves is connected for graduating movement while the other valve is connected for snap action movement. With reference to the accompanying drawing, the several parts are associated with and carried by a valve body or casing 6 formed with a valve chamber 1 therein for receipt of a valve mechanism 8, and being formed with inlet and discharge passages 9 and H adapted for connection to a source of fuel such as gas or the like and to the main burner of a heat appliance. The valve mechanism 8 is composed of a main valve member l2 which is mounted for movement to and from a main valve seat I3 provided in an interior wall l4 dividing the inlet and outlet portions of the flow passage. As will be seen from the drawing, the valve seat is here formed of a separate disk-like member set into an opening in the wall l4 and provided with a plurality of flow openings I6 bounded by an upstanding annular knife-edge seat I1, and being further provided with a central opening hub portion I8 in which is mounted for reciprocal movement a depending centrally arranged stem portion l9 carried by the valve member l2. Movement of the valve mechanism 8, and more particularly the main valve member [2, to and from the valve seat I1 is under the control of a thermostat 2| which is movable in accordance with temperature changes and appropriately connected to the valve mechanism by the aforesaid motion transmitting means. The thermostat may be of any suitable construction afiording adequate movement in response to desired temperature changes and in the present embodiment is shown as a conventional gas or vapor filled bellows type which provides a desired sensitivity and amplitude of movement and is particularly adapted for use where room air temperature is being controlled. It will of course be understood that other types of thermostats may and will be used for other types of temperature control applications. The bellows 2| is here mounted'within a cap section 22 adjustably carried on a closure member 23 for the valve body and has its opposite movable ends 24 and 26 connected between the cap section and the motion transmitting means. As here shown the valve body 6 is formed with an opening 2'! in the upper side thereof as seen in the drawing through which may be inserted the valve mechanism 8 and the connecting means, and which is normally sealed off by the closure member 23, the latter being fastened to the body by screws 28 mounted through the closure member and engaging through bosses 29 on the side of the valve body. The cap member 22 is of a generally inverted cup shape mounted over and around the bellows 2| and having a generally cylindrical base portion 3| threaded onto an upstanding cylindrical collar 32 formed on the closure member 23, thereby providing relative adjustment of the distance between the outer end 33hr the cap section and the valve body to control the relative position of the bellows and accordingly the limits of the temperature range for which the device may be set. Preferabl a dial skirt (it is provided around the base 3| of the cap member and may be marked with suitable calibrations and legend cooperating with an index pointer 36 on the closure member to indicate the setting of the device. The center portion of the closure 23 is here formed with a hollow hub section 3? which journals for reciprocation a tubular member 38 forming part of the motion transmitting means and connecting the lower end 26 of the bellows with the valve mechanism. Preferably the upper end of membe 38 i affixed, to the lower end 26 of the bellows in som suitable manner such as by brazing or the like. The upper end 24 of the bellows is supported by the rounded head end 39 of an adjustment screw having its shank portion 4! threaded through the upper end 33 of the cap and held in place by a lock nut 43. The outer end 42 of th shank is preferably slotted or otherwise formed for tool engagement to permit convenient rotation for initially setting the device to conform to the calibrations on the dial skirt 34. A helical spring 44 is positioned around the member 38 and with its opposite ends compressed against the under side 25 of the bellows and the closure member 23 so as to thereby constantly maintain the bellows under a desired amount of compression against the screw head 39. Accordingly it will be seen that on rotation of the cap 22 in a clockwise direction as viewed in the drawing there will be a downward displacement of the bellows against the spring 44, thereby moving the valve member I2 toward its seat and causing the valve to reach a closed position at a relatively lower temperature. Contrariwise, a reverse rotation of the cap member 22 releases the compressive force on the upper end of the diaphragm, thereby requiring a greater amount of expansive movement of the diaphragm to close the valve, resulting in a closing of the valve at a relatively higher temperature. It will also be seen that for any given setting of the cap member the bellows will expand on increase of temperature, thereby displacing the valve I2 toward its closed position and, on the other hand, the bellows will contract on decreasing temperature to provide a corresponding opening of the valve. As hereinabove discussed, the principal disadvantage of a graduating type control lies in the throttling down of the fuel flow adjacent a closed position of the valve to a point of low burner efficiency, burner instability, faulty or imperfect lighting and attendant hazardous conditions. To avoid this throttling condition of fuel flow adjacent the closing of valve I2, I provide a bypass passage for the fuel around the valve 82 so as to insure a predetermined minimal flow of fuel regardless of the position of valve i2. Additionally, and as hereinabove discussed, there is provided a second or auxiliary valve for this bypass passage which is motivated into open and closed position with snap action. In accordance with the present invention the valve member i2 is graduated to a closed position upon increasing temperature, leaving the bypass passage open to preserve minimal flow. If the temperature of the controlled medium continues to rise the auxiliary valve is then snapped to a closed position, thereby abruptly shutting off all flow to the main burner. Thereafter, upon decrease of the temperature of the controlled medium, the auxiliary valve is first snapped open to establish minimal flow through the bypass passage. This flow is suificient to insure proper lighting of the main burner of the appliance by the usual constantly burning pilot burner and to provide a certain relatively efficient source of heat. If the temperature of the controlled medium continues to decrease, the main valve 52 starts to open and graduates toward open position in response to such decreasing temperature until full fuel flow to the main burner is established. To accomplish the foregoing, the motion transmitting means is divided into successively operating elements, one providing a direct graduating action of the main valve I2 and the other a successive snap action movement of the auxiliary valve, the elements functionin in contiguous temperature ranges of movement of the thermostat. In the present construction the bypass passage is conveniently formed through the main valve it. With reference to Figures 3 and 4, it will be seen that the valve member I2 is of cup shape having a planar base 45 engageable with the seat ill and a surrounding upstanding peripheral wall or flange lit. The bypass passage is here provided by a plurality of openings All formed in the wall 136 communicating with openings 58 arranged centrally in the planar base 45 within an upstanding knife edged annular valve seat G9. As shown in the drawing, the valve seat 49 and the openings 48 may be formed in a separate member pressed into a central opening in the base the member here being formed with a tubular extension providing the aforementioned guide stem is and additionally affording a guide bore 52 for a depending stem 53 of a bypass valve member 54 thus mounted for vertical reciprocation to and from the seat 49. Dual graduation and snap action of the respective valves by the motion transmitting means is accomplished by the inclusion in such means of an assembly composed of a pair of relatively movable sections or elements 55 and 5'! which are interconnected by a snap acting device 58 actuated upon relative movement of the sections. The assembly moves as a whole during the gradual closing of the valve l2 with a differential movement between the sections following upcn closing of valve i2, resulting in a snap action movement of valve 54, which is connected to the snap acting device. The motion transmitting element 5% here includes the above described member 38 and a bell shaped member 59 secured to the lower end thereof with a base portion 61 of the member 59 in juxtaposition to the upper end 62 of the valve flange 46. The snap device 58 is formed to resiliently urge and yieldably maintain the sections 51 and 59 in spaced apart relation, that is, with the portion SI of section 59 in spaced relation above the upper end 62 of the section 57. The inherent resilience and normal bias of device 58 holds the sections in spaced apart relation and serves to transmit movement of the section 56 (displaced by thermostat 2!) to effect a joint movement of section 57, and attached valve l2, and hence graduate the valve open and closed in response to a first range of movement of the thermostat as aforesaid. The snap acting device 58 in the present embodiment is in the form of a self restoring concavo-convex annulus of spring material which is mounted with its normally concave side facing the valve l2 and with its periphery resting upon the flange face 52. The base 6| of the opposing section is here formed with a depending annular fulcrum bead 63 which engages the normally convex side of the annulus on a circumference concentric to and lying within the outer periphery of the annulus supported on the face 62. Accordingly, downward movement of the section 58 from a vertically spaced apart position of the fulcrums 62 and 63 (see Figure 3) toward a nearer or contracted position, in effect a relative movement of the sections toward each other, will cause the annulus to be distorted to a point at which it will snap into an opposite overcenter position as illustrated in Figure 4. Contrariwise, a release of the compressing forces, applied to the annulus by the opposed fulcrums, will allow the device to snap back from contracted position of the sections to its normal position as shown in Figure 3, with the sections spaced apart. As an important feature of the present construction, and assisting materially in reducing the force and movement required to effect snap action of the annulus, means is provided for adjustably preloading the annulus. Such means is here in the form of a ring member 64 here threaded onto the wall 46 and having aninturned flange 65 defining with the face 62 an annular channel or groove in which the base 8! is retained for limited reciprocation. Normally the resilience of the annulus will retain the sections in a distended or spaced apart position as shown in Figure 3, that is, with the base 6! in engagement with the inturnecl flange 66. By screwing down the ring member 55, the sections will be displaced toward their contracted position and the annulus will be displaced towards a flattened position thus reducing the force and movement required to efiect displacement to its critical snap acting position. In accordance with the above described construction, the assembly of the two sections and annulus will move as a unit toward and to a closed position of valve l2. Thereafter, upon further movement of the thermostat (downward as viewed in the drawing), a relative approaching movement of the sections will take place, that is, the fulcrum 63 will move toward the face 62, thereby causing upon sufficient of such movement a snapping of the annulus. In the present construction the bypass valve member 54 is carried by and actuated with the annulus. As seen in Figure 51, the latter is formed with integral inwardly extending arms or tongues 61 and 88 which are formed at their inner ends with cut-out portions defining opposed sockets engageable around a cylindrical portion of a pin 69 inserted through the valve member 54 and providing the stem 53 above noted, the arm ends being retained between an enlarged head 'i! on the pin and the outer side of the valve member. Since the annulus is mounted with its normally convex side uppermost (as viewed in the drawing), the arms til and S normally support the valve member 54 in elevated open position over its seat 4%. Upon downward deflection on the annulus, the arms abruptly displace the valve member 54 to its seat, as shown in Figure 4, to thereby shut oil the bypass flow. Preferably the opening 21 in the valve body is sealed off by a diaphragm T2, the latter here being clamped at its periphery between opposed shoulders 53 and hi on the closure member and body respectively, and clamped at its center between the lower end of member 38 and the upper end of bell member 59 by means of a screw '16 passing through and fastening together these members as illustrated in Figures 3 and i. ihe diaphragm is formed of a flexible material such as thin sheet brass so as to permit inward and outward displacement of the motion transmitting means. The valve body may, if desired, be provided with a pilot take-off passage Ii ahead of the valve mechanism so as to supply a constant flow of fuel to the pilot burner associated with the main burner receiving fuel through the valve mechanism. In operation the dial skirt is rotated to the temperature setting desired to be retained by the device. If the room temperature is well below this setting, the valve will be in fully open position as illustrated in Figure 2 and maximum flow to the burner will be had. As the room temperature increases the valve member [2 will be gradually displaced toward closed position, thereby reducing the fuel flow. If the room temperature approaches the temperature for which the device is set, an equilibrium will be reached whereby an amount of fuel is passed proportionately to the heat loss of the room and the main valve will graduate toward open and closed position to maintain the desired room temperature within very close limits. Should the room heat loss further decrease due, for example, to rising outside temperatures, the main valve i2 will graduate to its closed position as illustrated in Figure 3, leaving, however, the bypass valve open, thereby maintaining minimal flow. If this minimal flow will satisfy the heat loss, the parts remain in position illustrated in Figure 3. If such flow is insufficient, valve 12 will open and graduate to a position where the flow is sufficient. If the minimal flow is more than sufficient to overcome the heat loss, and the room temperature continues to rise, the bell section 1352 will be displaced towards the opposing valve section which is retained stationary by the valve seat 11, resulting, upon an appropriate rise in temperature, in the snapping shut of the bypass valve, thereby cutting ofi all fuel flow to the main burner. This position of the parts is illustrated in Figure 5, and the parts will remain so positioned until the thermostat again calls for heat, at which time a general reversal of the above described operation takes place, that is, the bypass valve will first snap open to provide a minimal flow for safe lighting and some burner heat. If this flow is insufficient to satisfy the thermostat, further movement will take place resulting in the opening of valve l2 and thereafter its graduated further opening to a point of equilibrium. From the foregoing it will be noted that the general coaxial mounting of the several parts and concentric application of forces results with the structure employed, in a close coupled and most compact assembly co-acting to produce the combination graduating and snap action movements as described. Also it will be noted that the several co-acting internal parts may be preassembled and tested as a unit prior to final assembly of the device. The forming of the snap acting member as an annulus, the amplifying action of the concentric application of forces thereto and of the integrally formed arms, and the precise preloading of the annulus by ring member 6 3, all cooperate to afford abrupt snap action of the bypass valve with relatively large valve opening and with the requirement of a minimum force on and displacement of the parts, thus providing improved temperature sensitivity and response to a short temperature range. The preloading means also enables convenient factory setting to a desired and uniform sensitivity notwithstanding minor non-uniformities in the parts resulting from normal mass production. I claim: 1. In a thermostatically controlled valve, a valve mechanism having a first closed position and a second partially open position providing a predetermined minimal flow and a third fully opened position providing a maximum flow, a thermostat movable in accordance with temperature changes, motion transmitting means having relatively movable sections connecting said thermostat and valve mechanism to provide direct graduating movement of said valve mechanism between said second and third positions in response to a first range of movement of said thermostat, said sections having relatively spaced apart and contracted positions, an over-center snap acting device mounted between said sections and being formed to yieldably maintain said sections in said spaced apart position during said first range of movement and actuated by relative movement of said sections to contracted position to provide an abrupt movement of said valve mechanism between said first and second positions, and means effecting said relative movement of said sections to contracted position in response to a second range of movement of said thermostat contiguous to said first range of movement. 2. In a motion transmitting means connecting a thermostat and a valve mechanism having a first closed position and a second partially open position providing a predetermined minimal flow and a third fully opened position providing maximum flow, said means including a pair of relatively movable sections connected and cooperating to provide a direct graduating movement of said valve mechanism between said second and third positions in response to a first range of movement of said thermostat, said sections having relatively spaced apart and contracted positions, a snap acting device mounted between said sections and being formed to yieldably maintain said sections in said spaced apart position during said first range of movement and being actuated by relative movement of said sections to said contracted position to provide an abrupt movement of said valve mechanism between said first and second positions, and means causing said relative movement of said sections to contracted position upon movement of said thermostat in a second and contiguous range of movement. 3. In a thermostatically controlled valve, a body formed with a passage therethrough, first and second valves mounted in parallel flow control position in said passage, a thermostat connected to said body movable in accordance with temperature changes, motion transmitting means connecting said thermostat and said first valve and providing a direct graduated opening and closing of said first valve in response to a first range of movement or" said thermostat, said means including a pair of sections which are movable between relatively spaced apart and contracted positions in response to a second range of movement of said thermostat past the end of said first range of movement corresponding to the closed position of said first valve, an over-center snap acting device mounted between said sections and having a normal position resiliently urging said sections to said spaced apart position and being connected to and holding open said second valve in its said normal position, said device providing an abrupt snap action closure of said second valve upon said relative movement of said sections to said contracted position, said device being resiliently self-restoring to provide a reverse snap action movement to abruptly open said second valve upon return movement of said thermostat to said first range of movement. 4. In a thermostatically controlled valve, a body formed with a passage therethroug-h, first and second valves mounted in parallel fiow position in said passage, a thermostat connected to said body and movable in accordance with temperature changes, motion transmitting means connecting said thermostat and said first valve and including sections which are relatively movable between spaced apart and contracted positions, a concavoconvex member of spring material mounted between said sections and having a normal position resiliently maintaining said sections in spaced apart position for joint movement and thereby providing a direct graduated opening and closing of said first valve in response to a first range of movement of said thermostat, said member being actuated by relative movement of said sections to contracted position following a closing of said first valve in a second and contiguous range of movement of said thermostat to provide a snap action movement, and means connecting said member to said second valve to provide an abrupt opening and closing thereof upon said snap action movement of said member. 5. In a thermostatically controlled valve, a body formed with a passage therethrough and first and second valves arranged in parallel flow control position therein, a thermostat connected to said body and movable in one direction upon increase of temperature and in a reverse direction upon a decrease in temperature, motion transmitting means connecting said thermostat and first valve and including a pair of relatively movable sections having an expanded position and being relatively displaceable to a relatively contracted position upon movement of said thermostat in said first direction after closing of said first valve, an over-center device having snap movement between opposite terminal positions mounted between said sections and having a normal position resiliently urging said sections to said expanded position and actuated between said terminal positions upon relative displacement of said sections to and from said contracted position, said device being connected to said second valve and holding the latter open in the aforesaid expanded position of said sections and effecting an abrupt closing of said second valve upon relative contracting movement of said sections and an abrupt opening of said second valve upon a relative expanding movement of said sections thereby effecting a delayed snap action closing of said second valve only after closing of said first valve upon movement of said thermostat in response to increasing temperature and providing a snap action opening of said second valve upon return movement of said thermostat prior to the opening of said first valve. 6. In a thermostatically controlled valve, a body formed with a passage therethrough and a valve seat in said passage, a valve member movable to and from said valve seat, a thermostat connected to said body and movable in one direction upon increase of temperature and in a reverse direction upon a decrease in temperature, motion transmitting means connecting said thermostat and said valve member to provide a direct graduated closing movement toward and opening movement away from said seat of said valve member in response to a first range of movement of said thermostat, said means including an element connected to said thermostat for movement therewith and providing an annular fulcrum and a second element connected to said valve member and providing a second annular fulcrum of different diameter than said first fulcrum and arranged in concentric axially spaced relation thereto, a concave-convex annulus of spring material having an over-center snap action mounted on and between said fulcrums for transmitting motion from said first to said second element during said closing movement of said valve member and being stressed to assume an over-center position by said fulcrums upon seating of said valve member and continuing movement of said thermostat into a second range of movement contiguous to said first range, said valve member being formed with a bypass passage and valve seat therein afiording a minimal flow when said valve member is closed, a second valve member connected to said annulus and normally supported thereby in open position with respect to said second named seat, said annulus effecting a closing of said second valve member on said second seat upon said annulus assuming its over-center position as aforesaid and thereby effecting a delayed snap closing of said second valve member only after closing of said first valve member upon movement of said thermostat into said second range in response to an increasing temperature and providing a snap action opening of said second valve member prior to the opening of said first valve member upon return movement of said thermostat in said second range in response to decreasing temperature. 7. In a thermostatically operated valve, a body formed with a passage therethrough and a main valve seat therein, a main valve member movable to and from said main valve seat, a by-pass valve seat mounted in said passage in parallel flow control position with respect to said main valve seat, a by-pass valve member movable to and from said by-pass valve seat, a thermostat movable in accordance with temperature changes, motion transmitting means including relatively movable sections connected to said thermostat and said main valve member respectively and providing opposed ooaxially arranged annular fulcrums of different diameters, a concavo-convex annulus of spring material having an over-center snap action and formed with an integral radially extending tongue for transmitting said snap action, said annulus being mounted between said fulcrums for transmission of movement to said main va-ve member and said tongue being connected to said by-pass valve member for effecting abrupt opening and closing thereof. 8. In a thermostatically operated valve, a body formed with a passage therethrough and a main valve seat therein, a main valve member movable to and from said valve seat and formed with a centrally positioned bypass passage therethrough and a bypass valve seat therein, a bypass valve member movable to and from said bypass valve seat in a direction aligned with the movement of said main valve member, a thermostat movable in accordance with temperature changes, motion transmitting means including relatively movable axially aligned sections connected to said thermostat and said main valve member respectively and providing opposed coaxially aligned annular fulcrums of different diameters, a concave-convex annulus of spring material having an over-center snap action and formed with an integral internally radially extending tongue for transmitting said snap action, said annulus being mounted in coaxial alignment with and upon said fulcrums for transmission of movement to said main valve member and said tongue being connected to said bypass valve member for effecting abrupt opening and closingthereof. 9. In a device of the character described, a main valve, a bypass valve, a thermostat movable in accordance with temperature changes, means connecting said thermostat and main valve and including relatively movable sections providing opposed coaxially arranged annular fulcrums of different diameters, a concave-convex member of spring material having an over-center snap action mounted on said fulcrums for actuation thereby upon relative axial movement thereof, said sections being movable coaxially of said fulcrums between relatively spaced apart and contracted positions so as to actuate said member, position for selectively preloading said member, and means connecting said member and said by pass valve for snap actuation thereof. 10. In a device of the character described, a main valve and a substantially cylindrical wall movable therewith providing an annular surface in a plane generally perpendicular to the axis of movement of said valve, 2. concavo-convex member of spring material having an over-center snap action mounted on said surface, an actuating member for said snap acting member and engaging the latter on a side opposite said surface in a concentric ring of different diameter, a ring member engaging said actuating member and threaded on said wall for adjustably preloading said snap acting member, a thermostat movable in accordance with temperature changes connected to said actuating member, and a bypass valve connected to and actuated by said snap acting member. 11. In a device of the character described, a 7 casing providing a fuel passage and a valve seat therein, a main valve movable to and from said seat to control the flow through said passage and being formed with a centrally arranged passage and valve seat therefor, a substantially cylindrical wall connected to and movable with said valve and providing an annular surface substantially concentric to the axis of said second named passage and in a plane substantially perpendicular to the direction of movement of said valve, a concavoconvex annulus of spring material having an overcenter snap action mounted at its periphery and with its normally concave side on said surface, an actuating member engaging the normally convex side of said annulus in a ring concentric to but spaced radially inwardly of said surface, means connecting said wall and actuating member for applying an adjustable clamping force to said annulus, a thermostat movable in accordance with temperature changes connected to said actuating member, said annulus being formed with a pair of internally extending arms, and a valve carried by said arms and displaceable thereby into and from engagement with said second named valve seat for controlling flow through the passage provided in said first named valve. 12. In a device of the character described, a main valve and a Wall movable therewith providing a surface in a plane generally perpendicular to the axis of movement of said valve, snap-acting means cooperating with said surface, an actuating member for said snap acting means and engaging the latter on a side opposite said surface, a member engaging said actuating member and adjustably mounted on said Wall for adjustably preloading said snap acting means, condition responsive means movable in accordance with condition changes connected to said actuating memher, and a bypass valve connected to and actuated by said snap acting means. 13. In a device of the character described, a main valve having a support member movable therewith, snap acting means having an operating portion carried by said member, an actuating member for said means engaging an opposed operating portion thereof, and means engaging said actuating member and adjustably connected to said support member for selectively preloading said snap acting means, condition responsive means movable in accordance with condition changes connected to said actuating member, and a bypass valve connected to and actuated by said snap acting means. 14. In a device of the character described, a main valve, a bypass valve, condition responsive means movable in accordance with condition changes, means connecting said condition responsive means and main valve and including relatively movable sections providing opposed fulcrums, spring means having an over-center snap ction mounted between said fulcrums for actuation thereby and biased to urge said fulcrum to a spaced apart position, manually adjustable means limiting the spacing between said fulcrums in said spaced apart position for selectively preloading said snap acting means, and means connecting said bypass valve to said snap acting means for actuation thereby. References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,988,345 Vaughn Jan. 15, 1935 2,004,597 Birtch June 11, 1935 2,055,133 Newell Sept. 22, 1936 2,608,352 Schuster et al. Aug. 26, 1952

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    US-2991012-AJuly 04, 1961Thermostatic control valve
    US-2993646-AJuly 25, 1961Robertshaw Fulton Controls CoCombined temperature regulator and flame failure control
    US-3204921-ASeptember 07, 1965Honeywell IncSnap-acting thermostatic valve
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