US3593253A

US3593253A - Thermostat actuator blade assembly

Info

Publication number: US3593253A
Application number: US845333A
Authority: US
Inventors: Ernest N Taylor
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-07-28
Filing date: 1969-07-28
Publication date: 1971-07-13
Anticipated expiration: 1988-07-13

Abstract

An actuator for use in a thermostat assembly comprising a blade formed from multilayered thermally responsive material. The blade includes spaced side legs joined at one end to define a blade area for connection to a heat source and further includes a compensating leg extending transversely between the spaced ends of said side legs and defining a point of actuation between the side legs. Each side leg defines an active leg portion adapted to quickly deform in response to heat to move the point of actuation a predetermined distance from an initial position. The compensating leg is adapted to receive heat from the side legs and respond by deforming so as to return the actuating point a predetermined distance toward its initial position to thereby compensate for additional movement of the actuation point induced by heat saturation of the side legs.

Description

United States Patent [72] Inventor Ernest N.Taylor 2,128,869 8/l938 Winborne 337/378 00 2231 E. 67th St.. Chicago. Ill. 60649 Primary Emmmu flamld Broom: 23532 Assistant Examiner-Dewitt M. Morgan l C 1 H I H & Pnemed J y Attorney ume C ement ume Lee ABSTRAT= An actuator for use in a thermostat assembly [54] TunkMosTA-r ACTUATOR BLADE ASSEMBLY comprising a blade formed from multilayered thermally 6 chum m Drum, Flss responsive material. The blade Includes spaced side legs i joined at one end to define a blade area for connection to a [52] US. Cl 337/379, heat source and f th indudes a compensating k8 unending 337/1o|337/378 transversely between the spaced ends of said side legs and [5 I] Int. Cl l-l0lh 37/52 d fi i a Point f actuation between he side Each side [50] Field of 337/l0l. |eg d fi es an iv le portion adapted to quickly deform in 365; response to heat to move the point of actuation a predeter- 73/353-5 mined distance from an initial position. The compensating leg is adapted to receive heat from the side legs and respond by [56] cued deforming so as to return the actuating point a predetermined UNITED STATES PATENTS distance toward its initial position to thereby compensate for 3,238,780 3/l966 Doyle 337/378 (X) additional movement of the actuation point induced by heat 3,22l,l 24 ll/l965 Mertler 337/354 saturation ofthe side legs.

422 :08 2: no l0 6 j I I '5 |O0 mun. "2 i04 4224 I l 4 l a "8 i t l rt us 104 H 1112" I20 T1 |32 I04 A I 34 L |Q2 H L 30 TI-IERMOSTAT ACTUATOR BLADE ASSEMBLY BACKGROUND AND GENERAL DESCRIPTION OF THE INVENTION This invention relates generally to an improved tempera ture-controlled device and more particularly relates to an improved actuator blade for use in thermostat assemblies.

As well known by those skilled in the art, many thermostat assemblies in current use have actuator blades which cause the thermostat to have undesirable operating characteristics. For instance, a principal defect in current thermostats is the inability of the actuator blade to respond quickly to a change in the temperature of the medium, such as a heating or cooling appliance, being controlled. Because of defects in the actuator blade design, most prior assemblies generally have been unable to closely control the application of heat to a medium without experiencing a substantial temperature differential between heating cycles.

Further, the designs of .many prior actuator blades have resulted in an undesirable lag between the time at which the medium being controlled reaches a desired temperature, and the time at which the thermostat responds by either cutting off the application of heat, if the medium is a heating appliance, or beginning the application of heat, if the medium is a cooling appliance. This temperature overshoot or undershoot is particularly prevalent in the first cycle of operation of these prior thermostats. The prior attempts to design a thermostat actuator blade wmch would eliminate the foregoing problems have generally resulted in complicated designs involving compound bimetal blades, and the like, which have been found to be expensive to manufacture, operate and maintain.

Accordingly, it is the purpose of this invention to provide an improved actuator blade for use in thermostat assemblies which overcomes the foregoing problems. The blade in accordance with this invention is of simple design and can be manufactured with low unit cost without using expensive compound bimetals. Moreover, the geometric shape and proportions of the actuator blade of this invention allows the temperature differential between operating cycles of a thermostat assembly to be closely controlled. The actuator blade further operates to substantially minimize temperature overshoot or undershoot during the first cycle of operation.

Generally, the actuator blade in accordance with this invention is formed from thermostat metal and includes side legs which are spaced at one end and preferably joined at the other end. A compensating leg is extended between the spaced ends of the side legs, and defines the point of actuation for the blade. The compensating leg serves to offset undesirable control characteristics growing out of the wide temperature gradient which normally exists along the active length of conventional thermostat-actuating blades sensing rapidly heated or rapidly cooled surfaces. The side legs of the blade include active portions which respond rapidly to the forced application of heat or cold to the blade and thereby minimize temperature overshoot (if heating) and temperature undershoot (if cooling) on the first cycle of operation. Moreover, the geometric shape and proportion of the side legs and compensating leg of the blade results in a net movement of the bladeactuating point which minimizes the temperature differential between successive heating or cooling cycles of the thermostat by quickening the making and breaking of the circuit being controlled by the thermostat.

Further features, objects and advantages of the present invention will be more fully understood from the following description of an exemplary embodiment, taken in conjunction with the accompanying drawings, in which:

FIG. 1 iso plan view of a thermostat assembly incorporating the actuator blade in accordance with the present invention;

FIG. 2 is a plan view of the actuator blade of the present invention which is incorporated in the thermostat assembly illustrated in FIG. I;

FIG. 3 is an end elevational view of the actuator blade, as viewed along the line 3-3 in FIG. 2, with selected parts of the assembly shown in phantom in the normal positions assumed before the assembly is actuated;

FIG. 3A is a view similar to FIG. 3, illustrating an alternate design for the push link in the thermostat assembly;

FIG. 4 is an elevational view of the thermostat assembly illustrated in FIG. I, showing the assembly components in their normal positions, with the thermostat contracts closed, before the actuation of the assembly;

FIG. 5 is an end elevational view of the assembly as shown in FIG. 4; a

FIG. 6 is a side elevational view of the thermostat assembly, showing the assembly components in the positions assumed after the assembly is actuated by an initial application of heat, and the blade has not attained uniform temperature in all of its parts.

FIG. 7 is an end elevational view of the assembly as shown in FIG. 6;

FIG. 8 is a side elevational view of the thermostat assembly, showing the components of the assembly in the positions assumed after the heat applied to the assembly has caused all of the parts of the blade to attain approximately the same temperature; and

FIG. 9 is an end elevational view of the thermostat assembly as shown in FIG. 8.

EXEMPLARY EMBODIMENT The improved thermostatic actuator blade embodying the advantages and features of the present invention is generally indicated by the reference numeral I0 in the drawings. The blade 10 is made of a suitable thermostat metal and is responsive to the application of heat. The preferred form of the blade I0 is made to have a unitary construction by stamping the blade from a single sheet of the thermostat metal. The blade 10 can be incorporated in a suitable thermostat assembly, such as the assembly illustrated in the drawings, to closely control the temperature of devices such as flat irons, table appliances, copying equipment, etc. More specifically, the blade 10 will operate in the thermostat assembly 100 to minimize the first cycle temperature overshoot and the temperature differential between operating cycles for the device being controlled. The blade 10 also will operate to minimize temperature undershoot when used with a thermostatic control assembly for a cooled appliance.

Referring to the drawings in more detail, the illustrated thermostat assembly 100 is a conventional friction-free, stacktype thermostat, similar to that described in U.S. Pat. No. 3,221,124, issued on Nov. 30, I965, to Charles S. Mertler. Of course, it will be appreciated by those skilled in the art that the blade 10in accordance with this invention can be utilized with other forms of thermostat assemblies, including snap-acting types, to control the temperature of heated or cooled appliances.

The illustrated assembly 100 includes a heat collector I02 positioned at the bottom of a stack of insulators 104. The heat collector I02 is made from a heat-conductive material, and is positioned in contact with the surface of the appliance A for which the temperature is being controlled. A cantilevered base 106 is positioned on the top of the stack of insulators I04 and projects a predetermined distance to the side of the insulator stack.

Electrical terminals

112 and 113 are mounted on the assembly I00 between adjacent insulators 104 and are electrically insulated from the hollow fastening rivet 108. The hollow rivet I08, formed either as a separate or integral part of heat collector I02, is used to firmly join the heat collector I02, the insulators 104, the electrical terminals I12 and 113, the

contact blades

114 and 116, and the base 106 in the stacked arrangement. Further, the assembly 100 can be firmly mounted on the appliance A by extending a screw 110, or other suitable fastener, through the interior of the hollow rivet 100, or by providing a suitably shaped heat collector for other means of securing to appliance A.

The thermostat assembly 100 also includes an upper contact blade 114 and a lower contact blade 116. As illustrated in FIG. 4, the

blades

114 and 116 are positioned directly below the base 106, and extend a predetermined distance transversely from the stack of insulators 104, in the same direction as the base 106. One end of the blade 114 is positioned between adjacent insulators 104 in electrical contact with the terminal 112, and one end of the blade 116 is positioned, in a similar manner, in electrical contact with the terminal 113. This arrangement spaces the contact blades 114 and 116 a predetermined distance apart. Further, the ceramic insulators 104 electrically insulate the

blades

114 and 116 and

terminals

112 and 113 from the heat collector 102, the rivet 108 and the appliance A.

In addition, the free ends of the

contact blades

114 and 116 carry

opposed contact points

118 and 120, respectively. The

contact points

118 and 120 operate in the conventional manner to close the circuit between the terminals 112 and 1 13 when the points are in contact, and to break the circuit between the terminals when the points are separated.

The assembly 100 also includes an adjusting screw 122, to permit the temperature of appliance A to be preset within a given temperature range. To accomplish this, the screw 122 carries an insulating tip 124 which extends through an aperture in the upper contact blade 114 and engages and positions the lower blade 116, which is otherwise biased upward. Adjustment of the screw 122 thus changes the position of the lower contact blade 116 with respect to the blade 114, and determines the temperature at which the

contact points

118 and 120 will separate. A suitable stop 126 can be arranged on the base 106 adjacent the screw 122 and a matching lug 123 attached to the adjusting screw for limiting the rotation of adjustment for the screw 122 within a predetermined range.

In the illustrated embodiment, the actuator blade is positioned in the thermostat assembly 100 so as to extend beneath the

contact blades

114 and 116. One end of the blade 10 defines a substantial surface area 11 which is fixed between the lowermost insulator 104 and the heat collector 102 of the assembly. This arrangement places surface area 11 of the blade 10 in direct heat-conductive relationship with the appliance A through the heat-conductive relationship with the appliance A through the heat collector 102. The outer free end of the actuating blade 10 is extended below the

contact blades

114 and 116 so that the blade 10 has a predetermined free length which can respond to a change in temperature in the appliance A. Metallic Washer 128 is mounted in the stack of insulators 104 on the top side of the fixed end of the blade 10 to accurately define the free length of the blade 10.

As illustrated in FIGS. 3 and 4, the thermostat assembly 100 also includes a push link 130 which is formed from ceramic or other suitable insulating material. The upper end of the link 130 projects through an aperture 115 provided in the upper contact blade 114. The aperture 115 is dimensioned to freely receive the link 130, and stabilizes the link from excessive horizontal movement in the assembly. The upper portion of the link 130 also includes shoulders 131 which engage with the lower surface of the contact blade 114 during operation of the assembly. Further, the main portion of the link 130 projects through an aperture 117 in the bottom contact blade 116. Lower shoulders 132 are vertically arranged on the link 130 to remain clear of the lower surface of the bottom contact blade 116 during the operation of the assembly 100, and to assure electrical spacing between blade 10 and blade 116 during any possible conditions of adjustment or operation of the assembly 100. The lower portion of the link 130 also projects through an aperture 32 provided in the blade 10, and seats upon a pair of nibs 34 on the blade 10. As clearly illustrated in FIG. 3, the link 130 and the other components of the assembly are arranged so that the shoulders 131 on the link are positioned slightly below or touching the contact blade 114 before the initial actuation of the assembly. and clearance is maintained between shoulders 132 and contact blade 116 before or during actuation.

FIG. 3A illustrates a modified push link 1300 for use in the thermostat assembly 100. Like the above-described link 130, the modified link 130a functions to transmit the motion of the actuating blade 10 to the upper contact blade I14 and to assure electrical spacing between the actuating blade 10 and the contact blade 116. The link 1304 is modified to have a generally H-shaped configuration, and the adjacent portions of the

contact blades

114 and 116 are modified to receive the link.

Thus, the contact blade 114 is modified to have a pair of apertures 1150 for receiving the upper end portions of the link 130 a, and a rounded nib 115!) is provided on the blade 114 between the apertures 115a for engagement with the link 1300. The upper center portion of the link 1304 is provided with a rounded shoulder 1310 which engages with the nib 115b. The rounded configuration of the nib 115b and the shoulder 131a assures that the link 1300 and upper contact blade 114 will engage with substantially point contact. The lower contact blade 116 also is modified to include a large aperture 117a for receiving the central portion of the link a.

As illustrated in FIG. 3A, the blade 10 is also modified for use with the push link 131a. The compensating leg 30 is provided with a pair of aligned apertures 32a for receiving the H- shaped lower portion of the link 1300. The central portion of the compensating leg 30 is further provided with a raised, rounded nib 34a which engages with a rounded shoulder 35 provided on the lower central portion of the link 1310. By this arrangement, the compensating leg 30 of the blade 10 and the link 131a will engage with substantially point contact.

Thus, the construction of the push link 1300, as shown in FIG. 3A, provides a link which has substantially two-point contact between the upper contact blade 114 and the actuating blade 10. Due to such construction of the link 130a, the operation of the thermostat assembly 100 will be essentially unaffected by slight misalignment of the link, or by the orientation of the assembly 100 in a position other than horizontal.

In the illustrated embodiment, the actuator blade 10 in accordance with this invention is arranged in the assembly 100 with its low-expansion side defined by the top of the blade, and its high-expansion side defined by the bottom of the blade. As indicated in FIG. 2, one end of the blade 10 is provided with an aperture 12 for receiving the rivet 108 of the assembly 100, as described above. The remaining portion of the blade 10 is formed to define a pair of diverging side legs 20 and a compensating leg 30 which extends transversely between the spaced free ends of the legs 20. The angle of divergency for the side legs 20 is approximately l2 from the blade centerline. in the illustrated embodiment. Of course, it will be appreciated that this divergency can be varied to adapt the blade 10 to the physical limitations of particular installations and to provide the compensating leg 30 with the desired length and operating characteristics.

In the preferred form of the blade 10, the side legs 20 are formed by cutting a notch 21 from the center of the sheet material from which the blade is stamped. The central notch 21 divides the blade into the two side legs 20, and reduces the width of the portion of the blade which receives the initial heat from the appliance A. The notch 21, generally V- or U-shaped in configuration, thereby reduces the amount of blade material which must be heated and allows the initial heat to saturate the area 11 of each side leg 20 very rapidly. The notch 21 also reduces warpage in the blade 10 by eliminating material which may otherwise react to heat by deforming transversely across the blade centerline.

As seen in FIG. 2, each of the side legs 20 of the blade 10 includes a flat, active portion 22 of a predetermined length and a formed inactive portion 24. The active portions 22 have a substantial cross-sectional area, and are adapted to respond quickly to the application of heat to the blade 10 by deforming in the vertical plane as viewed in the drawings. Since the highcxpamiion side of the blmetal is on the lower side of the blade 10. heat will cause the blade 10 to deform upwardly in this embndiment.

In contrast to the active leg portions 22. the inactive portions 24 of the blade are designed to be unresponsive to the application of heat to the blade. As seen from FIG. 3, this is accomplished by forming the blade material upwardly at the end of the active leg portions 22 so that the portions 24 comprise stifiening flanges having cross-sectional areas substantially less than the cross-sectional area of the connected active leg portion 22. Thus, the inactive portions 24 of each side leg are rigid, and are incapable of deforming in response to the flow of heat from the side legs 20. The resulting reduced cross section of the inactive portions 24 also operates as a heat choke and slows the flow of heat from the side legs 20 into the compensating leg 30.

As explained further below, this arrangement of the side legs 20 permits the side legs to respond rapidly to the application of heat by deactivating a major portion of the free length of the blade 10, as defined by the inactive leg portions 24. The rapid response of the side legs 20 to heat is facilitated further by the concentration of the heat in the active leg portions 22 as a result of the heat-choking action of the reduced leg portions 24. Of course, the cross section of the inactive leg portions 24 can be selected to suit the particular requirements of the appliance or the like under control.

The compensating leg 30 of the blade 10 is joined to the side legs 20 at the outer extremities of the inactive leg portions 24. in the illustrated embodiment, the leg 30 is integral with the side legs 20, and likewise has the thermostat metal arranged with the low-expansion side on the top, and the high-expansion side is on the bottom. The reduced cross section of the inactive leg portions 24 assure that the compensating leg 30 will receive heat from the side legs 20 slowly as the blade 10 becomes saturated.

Further, the arrangement of the leg 30 transversely across the ends of the side legs 20, with the high-expansion side of the thermostat metal on the bottom, will cause the leg 30 to deform downwardly in response to heat. After the initial heating cycle, this deformation of the leg 30, causing points of actuation 34 to move downward in a direction opposite from the upward movement of the side legs 20, thus will "compensate" for the additional deformation of the side legs 20, as the side legs become saturated by moving the points of actuation 34 (or 34a) downwardly through a predetermined distance.

The length of the compensating leg 30 is selected to provide the blade 10 with the desired amount of movement upon saturation by the heat flowing from the side legs 20. Since a longer bimetallic strip requires more time to saturate with heat than a shorter strip and results in further physical movement upon saturation, it is evident that an increase in the length of the leg 30 will increase the amount of such downward compensating movement, and a decrease in the length of the leg will correspondingly decrease the amount of movement. Of course, the characteristics of the leg 30 also can be changed to suit particular applications by forming the leg 30 from a thermostat metal strip which has the desired characteristics of heat conductivity and movement.

The configuration of the compensating leg 30 also can be selected to adapt the blade 10 to a particular installation. In the illustrated embodiment, the leg 30 is shaped and arranged so that its central portion along the centerline of the blade is raised. The point of actuation for the leg 30, where the leg engages with and transmits movement to the link 130, is thereby raised so that the link 130 will not interfere with the surface of the appliance A. As further indicated in FIG. 2, the central portion of the leg 30 is also widened to strengthen the leg adjacent the link aperture 32. The end portions of the leg 30, where the leg is joined to the inactive portions 24 of the side legs 20, are narrowed to delay the saturation of the leg 30 by partially choking the flow of heat to the leg 30 from the side legs 20. The narrow end portions of the leg 30 further minimize twisting or spherical deformation of the leg 30 and thereby assure that the compensating movement of the leg 30 will be substantially linear.

The various features and advantages of the actuator blade 10 in accordance with this invention will be apparent from a description of the operation of the blade in the thermostat assembly to control the temperature of the heating appliance A. Of course, it will be appreciated by those skilled in the art that the operation of the blade 10 to control the temperature of a cooled appliance would be similar. In an appliance wherein the actuation of a thermostat such as the assembly 100 was induced by cooling rather than heating, the positioning of the thermostat metal iorrnlng the blade 10 would be reversed, e.g., the low-expansion side of the bimetal would be on the bottom of the blade. However, the blade movement induced by a temperature change would be the same as described below.

As illustrated in FIGS. 3-5 under normal conditions, before the application of heat to the appliance A, as controlled by thermostat assembly 100, the

contact blades

114 and 116 are arranged to close the contact points 118 and 120. The circuit between the terminals "2 and 113 of the assembly is thereby completed so that heat may be applied to the appliance A by directing an electrical current through the terminals. The adjusting screw 122 is set so that the contacts 118 and will separate and break the circuit when the surface of the appliance. A has reached a predetermined temperature. As seen in H08. 3 and 4, the actuator blade 10 is undeformed under these normal unheated conditions and supports the point of actuation for the leg 30 in an initial position which places the

shoulders

131 and 132 on the link slightly below the contact blades 114 and l 16, respectively.

As heat is applied to the appliance A, the heat is transmitted through the heat collector 102 directly to the blade 10. Because of the geometric shape and proportions of the blade 10, the heat quickly flows into the active portions 22 of each of the blade side legs 20. Accordingly, when the appliance A has reached a predetermined temperature, the blade 10 will be deformed by the heat, with the greatest curvature occurring in the side leg portions 22 adjacent to the heat collector 102, due to the natural temperature gradient as heat flows from heat collector 102 toward the blade extremities. The blade 10 thereby will move quickly upward from the normal position illustrated in FIGS. 4 and 5 into a raised position, such as illustrated in FIGS. 6 and 7. During this first cycle of operation of the thermostat 100, inactive portions 24 of the blade legs 20 choke the passage of heat flowing from the active portions 22 of the blade and thereby accelerate the saturation of the leg portions 22. The rigidity of the leg portions 24 further prevents that portion of the legs from deforming in response to the flow of heat from the blade portions 22. This arrangement minimizes further movement of the side legs 20 as the heat continues to flow through the side legs after the initial

opening ofthe contacts

118 and 120.

In addition, the configuration of the blade 10 slows the flow of heat from the inactive'portions 24 of the side arms 20 to the compensating leg 30 during the initial heating cycle. The compensating leg 30 of the blade does not deform to any appreciable extent during the initial application of heat to the blade, and the movement of the points of actuation of blade 10 is initially controlled by the active portions 22 of the side legs 20.

Due to the configuration and design of the blade 10, the active portions 22 of the side legs 20, which are immediately adjacent the source of heat, will respond to a temperature change before the heat sheets the compensating leg 30. Thus, the initial application of the heat to the thermostat 100 will quickly deform the blade 10 and cause the free end of the blade 10 to swing upwardly toward the

contact blades

114 and 116. This upward movement of the blade 10 in turn forces the link 130 upwardly and engages the shoulders 13] of the link with the upper contact blade 114. The link 130 is further arranged so that the lower shoulders 132 do not engage the lower contact blade 116 during this movement of the link. The

movement of the blade 10 is thereby transmitted to the blade 114 and raises the blade 11 to break the contact 118 away from the contact 120.

The blade 10 in accordance with this invention therefore is capable of responding quickly to the initial application of heat to swing the free end of the blade through a predetermined arc and break the circuit of the thermostat before the heat has dissipated throughout the blade. The blade thus minimizes first cycle temperature overshoot, and thereby permits the heat to the appliance A to be cut off during the first cycle at a temperature which closely corresponds to the cutoff temperature of succeeding cycles.

As well known by those skilled in the art, the heat applied to the actuator blade 10 continues to dissipate throughout the blade after the

contacts

118 and 120 are separated, until the side legs are heat saturated. As this saturation occurs, the side legs 20 of the blade will continue to deform and will raise the blade 10 into a further elevated position, such as illustrated in FIGS. 8 and 9. The saturation of the side legs 20 thus continues the separation of the contacts 118 and [20 after the circuit has been broken by the initial application of heat to the blade 10.

ln conventional actuator blades, this additional separation of the contacts requires the blade to cool for an undesirably delayed time before the contacts can be closed to start the succeeding heating cycle for the appliance. This delay in conventional actuator blades in turn results in an undesirably large temperature differential between cycles. in contrast to conventional blades, the blade 10 in accordance with this invention minimizes the amount of this additional deformation, upon saturation of the side legs 20, by providing the inactive portions 24 on the free end of each side leg. Since these leg portions 24 cannot deform in response to heat, the continued deformation of the side legs will be minimized as the heat dissipates throughout the blade. The amount of cooling needed of the blade which must occur between the first and second heat cycles, as well as between succeeding cycles is thus appreciably reduced. The temperature differential between operating cycles for the thermostat 100 is thereby minimized.

Moreover, the compensating leg 30 included on the blade 10 also acts to permit close control of the temperature differential between cycles, by compensating for the additional deformation of the side legs 20. Because of the arrangement of the leg 30, the heat applied to the side legs 20 will ultimately flow into the leg 30 and cause the leg 30 to deform downwardly in a direction opposite from the deformation of the legs 20 from the position such as illustrated in FIGS. 6 and 7 to a lower position, as illustrated in FIGS. 8 and 9. Thus, as the heat saturates the blade to, the leg 30 compensates for the additional upward deformation of the legs 20, which otherwise would tend to separate the contact points I18 and 120 further, by returning the actuating point of the blade toward its initial position.

The net movement of the contact point 118 resulting from saturation of the blade 10 is thus substantially reduced in comparison to the total movement occurring in conventional blades, due to saturation of conventional blades after the contacts of the thermostat open. As seen by comparing FIGS. 6 and 7 to FIGS. 8 and 9, the blade 10 is preferably designed so that the compensating downward movement of the actuating points of leg 30 spaces the contacts "8 and I20 approximately the same distance apart as when the circuit was broken by the initial upward movement of the side legs 20. Hence, the

thermostat contacts

118 and 120 engage again very rapidly. The blade 10 will thus start the subsequent operating cycle for the assembly 100 when the temperature of the appliance A drops to a set level, and the temperature differential between cycles will be minimized.

The blade 10 operates in a similar manner in the succeeding cycles of the thermostat assembly I00. After the blade 10 has cooled sufliciently to return the contacts 118 and I20 into engagement, the appliance A will receive heat to initiate the second heating cycle. As heat is conducted to the blade 10, the active portions 22 of the side legs 20 again saturate very rapidly and deform upwardly. The legs 20 thereby raise the link 130 to break the circuit between the contacts 118 and I20. Then, as the heat is distributed throughout the blade 10, the compensating leg 30 eventually becomes saturated, and

deforms downwardly. The downward movement of the leg 30 therefore compensates for the increased upward movement of the side legs 20 and returns the contact point 118 into position for beginning the next heating cycle.

It is apparent from the above description that the blade 10 effectively quickens the separation of the

contacts

118 and 120, and the breaking of the circuit of the thermostat 100, especially during the first cycle, when the appliance A is heated from a cold temperature. The blade therefore reduces first cycle overshoot. The blade 10 also reduces the effective temperature differential on succeeding cycles of operation, by increasing the speed of making and breaking the engagement between the

contacts

118 and 120.

It is further apparent from the above description that the blade 10 can be proportioned and the assembly calibrated to operate in a normal fashion as a temperature control and still act as a rate-of-rise limit control" by responding to extreme rates of temperature rise as may occur due to abnormal conditions such as in a water-heating appliance when it runs dry or is started dry inadvertently. Typical examples are coffeemakers, or hot-beverage vendors or dispensers.

Although the invention has been described with a certain degree of particularity and in the heating mode, it should be understood that the present disclosure has been made only by way of example. Consequently, numerous changes in the details of construction and the combination and arrangement of components as well as the possible modes of utilization, will be apparent to those familiar with the art, and may be resorted to without departing from the spirit and scope of the invention as claimed.

What I claim is:

l. in a thermostat assembly having a pair of movable contact means for making and breaking an electrical circuit and thereby controlling the application of heat to a medium, the improvement comprising an actuator blade formed from multilayered thermally responsive material, said blade comprismg:

a pair of spaced side legs adapted at one end to define a substantial blade area for connection to a source of heat and spaced at the other end;

a compensating crossleg bridging transversely across the spaced ends of said side legs, said crossleg having said layers arranged in the same relative position as said side legs, and defining a point of actuation for said blade between said side legs; and

means linking said point of actuation to one of said contact means for transmitting the motion of said point to said one contact means;

each of said side legs defining an active leg portion adjacent said blade area formed from segments of said material having a substantial cross-sectional area and thereby adapted to receive heat quickly from said source and an inactive leg portion positioned between said active portion and said compensating leg adapted to be substantially unresponsive to the application of heat thereto and further having a reduced cross-sectional area relative to said active leg portions to choke the flow of heat from the connected active leg portion;

whereby said leg portions cooperate to concentrate the initial heat applied to said blade in said active portions of said side legs so that said active portions respond quickly to said initial heat to move said point of actuation from an initial position through a predetermined distance and thereby break said contact means with minimum temperature overshoot; and

said compensating leg being adapted to receive heat from said side legs through said inactive leg portions and to respond to the flow of heat therethrough by returning said point of actuation a predetermined distance toward said initial position;

whereby said compensating leg acts to bring said contact means together and compensates for the additional movement of said side legs induced by heat saturation of said active leg portionsand thereby accelerates the making of said contact means and reduces the temperature differential between succeeding heat cycles of said thermostat assembly.

2. A thermostat assembly in accordance with claim I wherein said linking means comprises a member which extends between said point of actuation and said one contact means and which engages said point and said one contact means at single locations, so that the operation of said thermostat assembly is not adversely affected by misalignment of said one contact means and said blade.

An actuator for use in a thermostat assembly comprising a blade formed from multiple layers of thermally responsive material, said blade including:

a pair of spaced side legs adapted at one end to define a blade portion for connection to a source of heat and transversely spaced at the other end; and

a compensating cross leg joined to said side legs and transversely bridging across said spaced ends, said compensating crossleg having said layers arranged in the same relative position as said side legs, and defining a point of actuation for said blade between said side legs;

each of said side legs defining an active leg portion formed from segments of said material having a substantial crosssectional area and thereby adapted to deform quickly in response to the flow of heat into said blade to move said point of actuation a predetermined distance from an initial position of said point;

each of s id legs further including an inactive portion positioned between said active portion and compensating leg and comprising portions formed from said material having a reduced cross-sectional area relative to said active leg portions and thereby being adapted to delay the flow of heat from said active portions to said compensating leg;

said compensating leg being adapted to receive heat from said side legs and to respond to such heat fiow by deforming with respect to said side legs to return said point of actuation a predetermined distance toward said initial position;

whereby said compensating leg acts to compensate for additional movement of said point induced by heat saturation of said side legs.

4. An actuator for use in a thermostat assembly comprising a blade formed from multiple layers of thermally responsive material, said blade including:

a pair of spaced side legs adapted at one end to define a said side legs being spaced to provide said compensating leg with a substantial length and each of said side legs defining an active leg portion formed from segments of said material having a substantial cross-sectional area and thereby adapted to deform quickly in response to the flow of heat into said blade to move said point of actuation a predetermined distance from an initial position of said point;

- each of said side legs further including an inactive portion positioned between said active portion and compensating leg and comprising substantial rigid leg portions having a reduced cross-sectional area relative to said active leg portions and thereby being substantially unresponsive to the application of heat thereto and adapted to choke the flow of heat from said active portions to said compensating leg;

said compensating leg being adapted to receive heat from said side legs and to respond to such heat flow by deforming with respect to said side legs to return said point of actuation a predetermined distance toward said initial position;

whereby said compensating leg acts to compensate for additional movement of said point induced by heat saturation of said side legs occurring after the initial heating cycle.

5. An actuator for use in a thermostat assembly comprising a blade formed from multiple layers of thermally responsive material, said blade including:

a compensating cross leg formed from a segment of said material joined to said side legs transversely across said spaced ends. said compensating crossleg having said layers arranged in the same relative position as said side legs and defining a point of actuation for said blade between said side legs;

said side legs diverging toward said spaced ends to provide said compensating leg with a substantial length and each of said side legs defining an active leg portion formed from segments of said material having a substantial crosssectional area and thereby adapted to deform quickly in response to the flow of heat into said blade to move said point of actuation a predetermined distance from an initial position of said point;

each of said side legs further including an inactive portion positioned between said active portion and compensating leg and comprising rigid flange portions formed from said material having a reduced cross-sectional area relative to said active leg portions and thereby being substantially unresponsive to the application of heat thereto and adapted to choke the flow of heat from said active portions to said compensating leg;

6. in a thermostat assembly having a pair of movable contacts for making and breaking an electrical circuit and thereby controlling the application of heat to a medium, the improvement comprising an actuator blade formed from multilayered thermally responsive material, said blade comprising:

a pair of diverging side legs adapted at one end to define a substantial blade area for connection to a source of heat and spaced at the other end;

a compensating leg formed from a substantially flat portion of said material integral with said side legs and extended transversely between the spaced ends of said side legs and further defining a point of actuation for said blade between said side legs; and

means linking said point of actuation to one of said contacts for transmitting the motion of said point to said contact;

each of said side legs defining an active leg portion adjacent said blade area comprising substantially flat segments of said material having a substantial cross-sectional area and adapted to receive heat quickly from said source; each of said side legs further defining an inactive leg portion adjacent said compensating leg formed from a rigid flange portion of said material having 'a reduced cross-sectional area relative to said active leg portions and adapted to be substantially unresponsive to the application of heat thereto and to choke the flow of heat from the connected active leg portion;

whereby said leg portions cooperate to concentrate the initial heat applied to said blade in said active portions of said side legs so that said active portions respond quickly to said initial heat to move said point of actuation from an initial position through a predetermined distance and stantial temperature gradient between the controlled medium and the compensating leg at said point of actuation occurring during the initial heating cycle. and further compensates for the additional movement of said side legs induced by heat saturation of said active leg portions. whereby said blade accelerates the making of said contacts and reduces the temperature differential of the heated medium during the heating cycles.

Claims

1. In a thermostat assembly having a pair of movable contact means for making and breaking an electrical circuit and thereby controlling the application of heat to a medium, the improvement comprising an actuator blade formed from multilayered thermally responsive material, said blade comprising: a pair of spaced side legs adapted at one end to define a substantial blade area for connection to a source of heat and spaced at the other end; a compensating crossleg bridging transversely across the spaced ends of said side legs, said crossleg having said layers arranged in the same relative position as said side legs, and defining a point of actuation for said blade between said side legs; and means linking said point of actuation to one of said contact means for transmitting the motion of said point to said one contact means; each of said side legs defining an active leg portion adjacent said blade area formed from segments of said material having a substantial cross-sectional area and thereby adapted to receive heat quickly from said source and an inactive leg portion positioned between said active portion and said compensating leg adapted to be substantially unresponsive to the application of heat thereto and further having a reduced cross-sectional area relative to said active leg portions to choke the flow of heat from the connected active leg portion; whereby said leg portions cooperate to concentrate the initial heat applied to said blade in said active portions of said side legs so that said active portions respond quickly to said initial heat to move said point of actuation from an initial position through a predetermined distance and thereby break said contact means with minimum temperature overshoot; and said compensating leg being adapted to receive heat from said side legs through said inactive leg portions and to respond to the flow of heat therethrough by returning said point of actuation a predetermined distance toward said initial position; whereby said compensating leg acts to bring said contact means together and compensates for the additional movement of said side legs induced by heat saturation of said active leg portions and thereby accelerates the making of said contact means and reduces the temperature differential between succeeding heat cycles of said thermostat assembly.

2. A thermostat assembly in accordance with claim 1 wherein said linking means comprises a member which extends between said point of actuation and said one contact means and which engages said point and said one contact means at single locations, so that the operation of said thermostat assembly is not adversely affected by misalignment of said one contact means and said blade.

3. An actuator for use in a thermostat assembly comprising a blade formed from multiple layers of thermally responsive material, said blade including: a pair of spaced side legs adapted at one end to define a blade portion for connection to a source of heat and transversely spaced at thE other end; and a compensating cross leg joined to said side legs and transversely bridging across said spaced ends, said compensating crossleg having said layers arranged in the same relative position as said side legs, and defining a point of actuation for said blade between said side legs; each of said side legs defining an active leg portion formed from segments of said material having a substantial cross-sectional area and thereby adapted to deform quickly in response to the flow of heat into said blade to move said point of actuation a predetermined distance from an initial position of said point; each of said legs further including an inactive portion positioned between said active portion and compensating leg and comprising portions formed from said material having a reduced cross-sectional area relative to said active leg portions and thereby being adapted to delay the flow of heat from said active portions to said compensating leg; said compensating leg being adapted to receive heat from said side legs and to respond to such heat flow by deforming with respect to said side legs to return said point of actuation a predetermined distance toward said initial position; whereby said compensating leg acts to compensate for additional movement of said point induced by heat saturation of said side legs.

4. An actuator for use in a thermostat assembly comprising a blade formed from multiple layers of thermally responsive material, said blade including: a pair of spaced side legs adapted at one end to define a blade portion for connection to a source of heat and transversely spaced at the other end; and a compensating crossleg formed from a segment of said material joined to said side legs transversely across said spaced ends, said compensating crossleg having said layers arranged in the same relative position as said side legs, and defining a point of actuation for said blade between said side legs; said side legs being spaced to provide said compensating leg with a substantial length and each of said side legs defining an active leg portion formed from segments of said material having a substantial cross-sectional area and thereby adapted to deform quickly in response to the flow of heat into said blade to move said point of actuation a predetermined distance from an initial position of said point; each of said side legs further including an inactive portion positioned between said active portion and compensating leg and comprising substantial rigid leg portions having a reduced cross-sectional area relative to said active leg portions and thereby being substantially unresponsive to the application of heat thereto and adapted to choke the flow of heat from said active portions to said compensating leg; said compensating leg being adapted to receive heat from said side legs and to respond to such heat flow by deforming with respect to said side legs to return said point of actuation a predetermined distance toward said initial position; whereby said compensating leg acts to compensate for additional movement of said point induced by heat saturation of said side legs occurring after the initial heating cycle.

5. An actuator for use in a thermostat assembly comprising a blade formed from multiple layers of thermally responsive material, said blade including: a pair of spaced side legs adapted at one end to define a blade portion for connection to a source of heat and transversely spaced at the other end; and a compensating cross leg formed from a segment of said material joined to said side legs transversely across said spaced ends, said compensating crossleg having said layers arranged in the same relative position as said side legs and defining a point of actuation for said blade between said side legs; said side legs diverging toward said spaced ends to provide said compensating leg with a substantial length and each of said side legs defining an active leg portion formed from segments of sAid material having a substantial cross-sectional area and thereby adapted to deform quickly in response to the flow of heat into said blade to move said point of actuation a predetermined distance from an initial position of said point; each of said side legs further including an inactive portion positioned between said active portion and compensating leg and comprising rigid flange portions formed from said material having a reduced cross-sectional area relative to said active leg portions and thereby being substantially unresponsive to the application of heat thereto and adapted to choke the flow of heat from said active portions to said compensating leg; said compensating leg being adapted to receive heat from said side legs and to respond to such heat flow by deforming with respect to said side legs to return said point of actuation a predetermined distance toward said initial position; whereby said compensating leg acts to compensate for additional movement of said point induced by heat saturation of said side legs.

6. In a thermostat assembly having a pair of movable contacts for making and breaking an electrical circuit and thereby controlling the application of heat to a medium, the improvement comprising an actuator blade formed from multilayered thermally responsive material, said blade comprising: a pair of diverging side legs adapted at one end to define a substantial blade area for connection to a source of heat and spaced at the other end; a compensating leg formed from a substantially flat portion of said material integral with said side legs and extended transversely between the spaced ends of said side legs and further defining a point of actuation for said blade between said side legs; and means linking said point of actuation to one of said contacts for transmitting the motion of said point to said contact; each of said side legs defining an active leg portion adjacent said blade area comprising substantially flat segments of said material having a substantial cross-sectional area and adapted to receive heat quickly from said source; each of said side legs further defining an inactive leg portion adjacent said compensating leg formed from a rigid flange portion of said material having a reduced cross-sectional area relative to said active leg portions and adapted to be substantially unresponsive to the application of heat thereto and to choke the flow of heat from the connected active leg portion; whereby said leg portions cooperate to concentrate the initial heat applied to said blade in said active portions of said side legs so that said active portions respond quickly to said initial heat to move said point of actuation from an initial position through a predetermined distance and thereby break said contacts with minimum temperature overshoot; and said compensating leg being adapted to receive heat from said side legs through said inactive leg portions and to respond to the flow of heat therethrough by returning said point of actuation a predetermined distance toward said initial position; whereby said compensating leg acts to move said contacts toward a closed position and compensates for the substantial temperature gradient between the controlled medium and the compensating leg at said point of actuation occurring during the initial heating cycle, and further compensates for the additional movement of said side legs induced by heat saturation of said active leg portions, whereby said blade accelerates the making of said contacts and reduces the temperature differential of the heated medium during the heating cycles.