US3354278A

US3354278A - Stack-type thermoresponsive switch having a supplemental heater with annularly-shaped heater portion and terminal regions

Info

Publication number: US3354278A
Application number: US483682A
Authority: US
Inventors: Frank T Piacent; John W Huffman
Original assignee: Emerson Electric Co
Current assignee: Occidental Chemical Corp; Emerson Electric Co
Priority date: 1965-08-30
Filing date: 1965-08-30
Publication date: 1967-11-21
Anticipated expiration: 1984-11-21

Description

Nov. 21, 1967 F. T. PEAQENT ETAL.

STACK-TYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITH ANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS Filed Aug. 30, 1965 3 Sheets-Sheet 1 INVENTORS FRANK T /ACE/VT &

BY JOHN m HUFFMAN I Filed Aug. 30, 1965 Nov. 21, 1967 F. T. PIACENT ETAL 3,354,278

STACK-TYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITH ANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS 5 Sheets-Sheet 2 TEMPERATURE INVENTORS FAAA/A/ Z P/ACE/VT & BY JOHN W HUFFMAN Maw Nov. 21, 1967 F. T. PIACENT ETAL 3,354,278

STACKTYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITH ANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS Filed Aug. 30, 1965 3 Sheets-Sheet 5 I -haw L:

VIII!!! INVENTORS FRANK Z /ACEA/7'5( BY JOHN W HUFFMAN United States Patent C) 3,354,278 STACK-TYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITH ANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS Frank T. Piacent and John W. Huffman, Mansfield, Ohio, assignors, by mesne assignments, to Emerson Electric Co., St. Louis, Mo., a corporation of Missouri Filed Aug. 30, 1965, Ser. No. 483,682 12 Claims. (Cl. 200122) This invention relates to thermoresponsive or thermostat switch means and more especially to a thermoresponsive switch means embodying manual control of the effective temperature operating range and incorporating auxiliary or supplemental heating means adapted to thermally influence the thermoresponsive means.

The invention particularly relates to thermoresponsive switches of the so-called stacked type wherein end regions of switch arms and a bimetal component are insulatingly mounted by circular members to provide a compact construction. Thermostat switches have been used extensively to maintain automatic control of a predetermined temperature embraced within a manual control particularly with appliances embodying heating elements, such as fiat irons, grills, fry pans and other electrically energizable appliances.

In conventional switches of this character, a substantial time lag occurs in the transfer of heat to the bimetal component resulting in a substantial temperature differential of the appliance between on and off conditions of the circuit. Supplemental heaters in the form of small resistance units have been utilized for accelerating the action of the bimetal element, and heretofore supplemental heaters have been positioned at regions spaced from the support means or stack assembly of the switch components. In such constructions where the resistance heater is spaced from the switch stack or extends outwardly from the stack, the heat responsive means or bimetal element is heated by convection and radiant heat. While such devices accelerate the operation of the thermoresponsive means and promote reduction in temperature diflerentials of the appliance in circuit with the switch means, appreciable over-run of the temperature is encountered in initial heating of the appliance and the repetitive cycling of the switch means by the thermoresponsive means or bimetal element is irregular and the temperature of the controlled appliance is not accurately maintained within a predetermined range.

The invention embraces a thermoresponsive switch mechanism embodying supplemental heating means for accelerating and stabilizing the action of the thermoresponsive means wherein heat from the supplemental heater is transmitted by conduction to the support region of the thermoresponsive means whereby temperature over-run during initial heating of an appliance is eliminated and wherein subsequent repeated cycling of the switch mechanism under the influence of the thermoresponsive means occurs at constant intervals to accurately maintain the appliance within narrow temperature range.

The invention further embraces a switch mechanism of the so-called stacked type wherein the components of the switch mechanism are supported by substantially cy- |lindrical mounting means and wherein a supplemental heating means is wholly contained within the support stack whereby the thermoresponsive means of the switch mechanism is influenced by heat of the supplemental heater conducted through the support stack.

Another object of the invention resides in an auxiliary or supplemental heater for influencing a thermoresponsive means of a stacked switch construction wherein the heating element is of generally circular contour for assembly in the support stack for the switch components where- 3,354,278 Patented Nov. 21, 1967 2 by the heat .developed by electric energy flow through the heater is eiTe-ctively transmitted through the support stack to the thermoresponsive means.

Another object of the invention resides in a circular shaped resistance heater for incorporation in the support means of a stacked switch wherein the heater is within the confines of the support arrangement to provide eliective control and transfer of heat by conduction to the bimetal means of the switch mechanism enabling the utilization of the switch mechanism mounted by the heated body or instrumentality of the appliance or which may be employed as a cycling switch disposed in a position remote from the heated body or instrumentality of the appliance.

Another object of the invention resides in a novel form of resistance heater for use in a thermostat switch mechanism wherein portions of the resistance heater are insulated one from another by' circular insulating means whereby the heating unit is embodied in a stacked switch mechanism without modification of other components of the switch mechanism.

A further object of the invention is the provision of a supplemental resistance heater which may be incorporated in other types of switch construction.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and tov combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE 1 is an enlarged longitudinal sectional view of a thermostat switch construction embodying a form of the invention, the switch construction being illustrated as mounted on an electrically heated appliance;

FIGURE 2 is an elevational view of the switch construction shown in FIGURE 1;

FIGURE 3 is a top plan view of the switch construction shown in FIGURE 2;

FIGURE 4 is an enlarged top plan view of one form of supplemental heater element of the switch construction;

FIGURE 4A is a side view of the construction shown p in FIGURE 4;

FIGURE 5 is an isometric view of an insulating mem her for assembly with the resistance heater element shown in FIGURE 4;

FIGURE 6 is a plan view of the heater element of FIGURE 4 illustrating the method of assembly of an in sulating member shown in FIGURE 5;

FIGURE 7 is a view similar to FIGURE 6 illustrating the method of assembly of the heater element with a second member of the character shown in FIGURE 5;

FIGURE 8 illustrates a time-temperature graph of a conventional thermostat switch mechanism embodying a conventional type of supplemental heater;

FIGURE 9 illustrates a time-temperature graph of the thermostat switch mechanism embodying the supplemental heater of the invention;

FIGURE 10 is an isometric view illustrating a modified form of supplemental heater construction for the thermostat switch and insulating members in dissembled relation;

FIGURE 11 is an isometric view showing another form of supplemental heater for thermostat switch and insulating members in dissembled relation;

FIGURE 12 is a fragmentary sectional view showing a method of controlling heat transfer from an appliance to the thermoresponsive element of the switch mechanlsm;

FIGURE 13 is a plan view of a control unit embodying a form of thermostat switch of the invention with certain portions broken away for purposes of illustration in association with a portion of an electrically-heated appliance controlled by the unit, and

FIGURE 14 is a longitudinal sectional view through the control unit and the portion of the appliance illustrated in FIGURE 13.

While the arrangement of the invention is particularly adaptable for controlling the temperature of electrically heated appliances, it is to be understood that the suppiemental heater arrangement may be employed in other forms of control mechanism for influencing a therrnoresponsive means.

Referring to the drawings in detail and initially to FIG- URES 1 through 3, there is illustrated a form of switch means embodying the invention as utilized for controlling the temperature of an electrically heated appliance, such as a flat iron. As shown in FIGURE 1, the electrically heated iron 10 is inclusive of a base portion or plate 11 embodying a conventional heating means 12 supplied with electric energy from current supply lines or conductors L1 and L2 through the switch mechanism. The iron is provided with a conventional housing 14.

In the arrangement illustrated in FIGURE 1, the base plate llprovides a support for the switch mechanism, but it is to be understood that the switch construction may be mountednpon any suitable portion of an electrically controlled appliance and may be disposed remote from an appliance where the switch mechanism is used as a cycling switch and not under the direct influence of the heat of an appliance. The switch construction illustrated in FIGURE 1 is approximately twice actual size and is the type of switch usually referred to as a stacked switch, viz. a switch mechanism wherein the switch components, the bimetal element or thermoresponsive means and circular insulating members are in vertically spaced stacked relation.

The switch construction is inclusive of a plate or member 16 forming a part of a support means for certain components of the switch, the plate 16 being provided with a bore through which extends a sleeve 13. Assembled on the sleeve are switch arms, a thermoresponsive means, a supplemental heater and insulating members. The switch construction constitutes a unit, as shown in FIGURE 2, which may be disposed remote from an appliance to be controlled. The base plate 11 is provided with a threaded opening to receive the threaded portion 20 of a securing screw 22 extending through the sleeve 18 for fixedly mounting the switch unit on the base plate.

The plate 16 is provided with an opening to receive a tenon portion 24 of a bushing or fitting 25, the bushing having a flange 26 engaging one surface of the plate 16, the tenon portion being swaged as at 27 into engagement with'the lower surface of, the plate 16 fixedly securing the bushing to the plate 16. Disposed within the bushing is a shaft 30 having a threaded portion 31 engaging an interiorly threaded region of the bushing 25, the shaft being rotatable for manually controlling the relative position of one of the switch arms in a manner hereinafter explained.

The fitting 25 is provided with an abutment 32 which cooperates with a stop means 34 carried by the shaft 30 for limiting the rotative movement of the shaft 39. A manipulating knob 36, shown in broken lines in FIG- URE 1, is telescoped onto the shaft 30, a portion 38 of the stop means 34 extending into a groove in the manipulating knob 36 whereby rotation of the knob effects rotation of the shaft 30. The range of rotation of the shaft 30 is slightly less than one complete revolution, being limited by engagement of the stop means 34 with the abutment 32. This movement limiting means for the shaft 30 determines the range of temperature within which the manual control means may 'be adjusted.

The switch construction is inclusive of a first switch arm or member 40 fashioned of a strip of metal adapted to be flexed or moved under the influenceof a thermoresponsive means, the switch member 40 being equipped with a contact 42.

A second flexible switch member 44, formed of a strip of metal, is equipped with a contact 46 arranged for cooperation with the contact 42 to complete and interrupt a circuit through the heating element 12in the plate 11 of the iron.

A circular end region of the switch member or arm 40 is provided with an opening to receive a tenon 47 of an annular disc or member 48 of insulating material which surrounds the support sleeve 18. A terminal member St is also provided with an opening to accommodate the tenon 47 on the insulating disc 43, the metal terminal 50 being in direct metallic contact with the switch arm 4t} as shown in FIGURE 1. An annular washer or disc 52 of insulating material on the sleeve 18 is disposed between the terminal 50 and the support plate 16. The tenon 47 insulates both the terminal 50 and the switch member 40 from the support sleeve 18, the terminal 59 being connected with a current supply conductor or line L2.

The second switch member 44 has an opening in an end region through which extends an annular insulating member 54. The insulating member 54 is provided with a flange 56 and disposed adjacent the flange 56 is a second terminal or connector 58 connected with the heater 12 in the base plate 11. Disposed between the switch member 44 and the terminal 58 and mounted on the annular insulating member 54 is a supplemental he'atingunit 60 for influencing the thermoresponsive means and which will be hereinafter described in detail.

The sleeve 18 is provided at its lower end with a flange 62. Mounted between the flange and the insulating member 54 is a thermoresponsive means or bimetal element 66, the bimetal element having an opening receiving the sleeve 18. It will be seen from FIGURE 1 that the above described components comprising the insulating washers or

members

52, 48 and 54 of circular exterior contour, the

switch members

40 and 44, the

terminals

50 and 58, and the supplemental heating unit 6% are arranged in stacked relation on the support sleeve 18. 7

After assembly of these components on the sleeve 18, the upper end region of the sleeve is swaged as at 68 to secure the support stack of components in assembled relation. The insulating members or

washers

48, 52 and 54 are fashioned of lava or insulating ceramic to withstand heat generated by the supplemental heating unit 60.

The switch member 44 is adapted to be manually adjusted with respect to the switch member 40 to a temperature at which it is desired to maintain the appliance 1i). Disposed between the lower end of the rotatable shaft 30 and the switch member 44 is an insulating strut or member 76 fashioned of lava or ceramic, one end of the strut being engaged in a socket or recess in the lower end of the shaft 30. The other end region of the strut 70 is fashioned with a wedge-shaped portion 72 which engages in a rectangular opening in the switch member 44, this construction preventing relative rotation of the strut ill when. adjusting the shaft 30.

The strut 70 extends through a clearance opening '74 in the switch arm d0 as shown in FIGURE 1. Through this arrangement manual rotation of the shaft 30,.through the medium of the strut '70, is effective to adjust or control the relative position of the switch arm 44 to secure the desired temperature for the base plate 11 of the appliance 1d. The bimetal element 66 is flexed by temperature variations for controlling the position of the switch member 49 to automatically maintain the plate 11 or other instrumentality at a predetermined temperature within the manual range of temperature setting or adjustment of the shaft 30. v i

The distal end of the bimetal element 66 is provided with an opening to receive an insulating member 76, formed of ceramic or lava which is secured to the bimetal element 66 by a'metal clip 78 fashioned with ear portions fit which, in assembly, are bent to embrace the edgesof ,FIGURES 1 and 2. The

the element 66, as shown in FIGURES 2 and 3. In the arrangement of switch mechanism and appliance shown in FIGURE 1, heat from the heated base plate 11 influences the bimetal element 66 to cause flexure of the element upwardly, engaging the lava member 76 with the switch arm 40 flexing the switch arm 40 to separate the contacts 42 and 46 and interrupt the energizing circuit to the base plate 12 when a predetermined temperature of the base plate is attained.

As heat is subsequently dissipated from the plate 11, the temperature of the bimetal element 66 is reduced and the element flexed in the opposite direction, moving the strut 76 away from the switch arm 40 and reengage contacts 42 and 46. The switch arm 40 is initially tensioned or stressed to bias the switch arm 40 in a direction to normally engage the contacts 42 and44 to complete the energizing circuit for the base plate 11.

The present invention embodies a supplemental, auxiliary or accelerating heater oriented or disposed in the support stack construction of switch components and insulating members shown in FIGURE 1 in a manner whereby heat from the supplemental heater is conducted through the support stack to the bimetal element 66 where-by the bimetal element is influenced principally by conducted heat rather than by convection as in supplemental heating units heretofore utilized to accelerate movement of a 'bimetal element.

The principle of the supplemental heater of the invention resides in fashioning the heating element of a configuration whereby it is wholly Within the confines of the support stack of the switch components. For such purpose the supplemental heater is preferably of circular shape or contour. One form of supplemental heater element and associated insulating means are'illustrated in FIGURES 4 through 7. The heater element is of the resistance type and is fashioned to provide a substantial length or path of resistance traversed by the current by fashioning the element to provide for traverse of the current in a generally circular path.

The heating element or resistance unit 86 of the supplemental heater 60 is shown per se in FIGURES 4 and 4A. The heating element 86 is fashioned of a fiat sheet of metal and is of generally circular shape and is comparatively thin as shown in FIGURE 4A. The circular central opening 88 of the annularly-shaped or circular heater 86 is of a dimension to slidably fit onto the exterior surface of the annular insulating member 54 shown in FIGURE 1. The annular configuration is split or slotted radially as at 90.

A circularly-shaped slot 92 preferably concentric with the circular periphery of the heating element 86 terminates' at regions 93, configurating the circular element into an annularly-sha-ped outer portion 95 and two semiannularly-shaped inner portions or

legs

97 and 99, the distal ends of the

semiannular portions

97 and 99 being separated by a radial slot 100. The

unslotted regions

102 and 104 form bridge or connector means integrally connecting the outer annular portion 95 to the inner semiannular portions of

legs

97 and 99, as particularly shown in FIGURE 4.

Regions of the semiannular portions or legs 97 and respectively with the switch arm 44 and the terminal 58 assembled in the stacked support formation shown in heater construction is inclusive of two annularly-shaped insulating members or

discs

106 and 106 which are of identical construction, member 106 being illustrated in FIGURE 5.

These insulating members are preferably fashioned of heat resistant insulating material, such as mica, and are made as thin as practicable so as to provide for compact assembly in the support stack construction.

Each of the annular members 106 and 106' is of an exterior diameter preferably slightly greater than the exterior diameter of the annular portion 95 of the resistance heater 86 to prevent possible current leakage. The circular opening 110 of each of the annular members 106 and 106' is of a diameter to snugly, yet slidably fit onto the annular insulating member 54, shown in FIGURE 1, each of the members being split or slotted as at 112 to enable assembly of the insulating members with the resis'tance heater element 86.

The method of assembling the insulating members 106 and 106' with the heater element 86 is illustrated in FIGURES 6 and 7. With reference to FIGURE 6, the

insulating member 106 is slidably moved laterally in the direction of the arrow in assembly with the heater 86 with the terminal leg portion 97 and the annular portion at the upper side of the insulating disc 106 as viewed in FIGURE 6, with the other terminal leg 99 adjacent the opposite major surface or lower side of the insulating disc 106, an assembly which is made possible through the use of the slot 112.

It should be noted that in assembly the disc 106 is preferably rotatably adjusted so that the slot 112 is adjacent the terminal region 93 of the circular slot 92 whereby a terminal portion 114 of the disc 106 straddles or covers the slot 90, as shown in FIGURE 6.

The insulating disc 106 is moved in the direction of the arrow in assembly until the exterior periphery of the insulating disc 106 is concentric with the circular portion 95, in which position the circular central opening 88 of the heating element 86 is in registry with the circular opening in the insulating disc 106.

With disc 106 and heater 86 pre-assembled as above described, these components are then assembled with the second insulating disc 106'. In assembling disc 106' with the heater element 86, the insulating disc is moved in the direction of the arrow, as shown in FIGURE 7, with preferably adjacent the terminal region 93 of the leg 97 so that a portion 114 of the insulating disc straddles or covers the slot 90 and the connecting bridges '102 and 104. The disc 106 has been omitted from FIG- URE 7 for purposes of illustration. As shown in FIG- URE 7, the terminal or leg portion 97 of the inner portion of the heater element 86 is above the insulating disc 106'.

Through this method of assembly of the resistance heating element 86 with the insulating

discs

106 and 106, one terminal leg 99 is exposed and adjacent an outer surface of the insulating disc 106, and the other terminal leg 97 is at the exposed or outer side of the insulating disc 106.

It should be noted that the slots 112 and 112' are at oppositely disposed regions of the slot 90 in the resistance heater so that the connecting or

bridge sections

102 and 104 are insulated one from the other.

In the final assembly of the pre-assembled heater element and insulating

discs

106 and 106 in the switch stack in the manner shown in FIGURE 1, the terminal leg 97 is in direct metallic contact with the switch arm 44 and the second terminal leg 99 in direct metallic contact with the terminal 58.

With respect to FIGURES l and 4, the current fiow path through the resistance heater element 86 is as follows: The terminal leg 97 is in engagement with the switch arm 44 and, when the contacts 42 and 46 are in circuit-closing or contacting position, current flows through the terminal leg 97 across the bridge section 102 through the annular portion 95, through slightly less than a complete circle to the bridge section 104, through the bridge section 104 to the terminal leg 99 thence to the terminal 58 which is in metallic contact with the terminal leg 99.

The effective resistance heating length of the element 86 is an elongated path of generally circular shape from the region of engagement of the terminal leg 97 with the switch arm 44 through the bridge 102, the annular portion 95, the bridge 104 and to the region of contact of the terminal leg 99 with the terminal or connector 58 of the switch construction. Through this method and arrange ment, a substantially long flow path of current through the resistance heater element is provided to produce a. substantial amount of heat in the support stack construction shown in FIGURE 1. Substantially all of the heat; is conducted through the stack, viz. through the insulating :member 54 and sleeve 18 to the region of the bimetal. adjacent the flange 56 of the insulating member and lengthwise through the bimetal element 66.

From the foregoing description it will be apparent that. the heat from the circular resistance heater construction or unit 86 is transferred to the bimetal element 66 substantially entirely by conduction through the stack so that a controlled transfer of heat from the heating unit 36- to the bimetal element 66 is through the support stack construction. By varying the thickness of the flange portion 56 of the insulating member 54, the rate of heat transfer by conduction to the bimetal element 66 may be accelerated or retarded depending upon the character of control desired for thermostatically controlling the position of the switch arm 40 and hence the automatic cycling of the circuit under the influence of the bimetal element 66. Y

The heating unit 86 and insulating discs 166 and 166' provide a compact, adequately insulated supplemental heater wholly embodied in the switch stack or support stack whereby the heat from the heating element for influencing the bimetal element is transferred solely through the stack. It is found that through this novel type of supplemental heater construction, more accurate automatic control of the desired temperature for an appliance is attained and over-run of temperature during the initial warm-up of an appliance is eliminated.

FIGURE 8 illustrates a time-temperature curve or graph of a conventional type of switch mechanism having a conventional type of supplemental heater disposed outside of the confines of the switch stack and is illustrative of temperature variations during actual cycling operation of such a switch.

During the initial warm-up period of the appliance, the rapid increase in temperature of the appliance is indicated at 120 and, in such conventional switch without a stack heater of the invention, the initial temperature of the appliance substantially over-ran the temperature range for which the switch is manually adjusted.

The extent of over-run is represented by the line 122, the initial interruption of the contacts occurring approximately at the point 121 of maximum amplitude of the temperature line 120. The line 122 of the graph illustrates the initial period of the circuit, the temperature of the appliance being reduced by normal cooling. Thereafter the on periods or the circuit closed heating periods of the appliance are illustrated by the lines 124, and the off periods or periods of circuit interruption represented by the lines 126. From FIGURE 8 it will be seen that the repetitive cycling of a switch embodying a conventional supplemental heater is non-uniform as indicated by the

lines

124 and 126 of the graph.

FIGURE 9 illustrates an actual time-temperature curve or graph of the switch mechanism of the instant application embodying the circular resistance heater assembled in the support stack and wholly within the confines of the stack. In the graph of FIGURE 9, the initial Warm-up period is indicated by the line 130. It Will be noted from FIGURE 9 that there is no initial over-run of tempera ture of the appliance above the temperature range for which the switch is manually adjusted.

Furthermore the off periods or nonheating periods represented by the line 134 are substantially repetitive in time and the on periods or circuit energizing periods represented by lines 136 are of substantially uniform amplitude whereby the temperature of the appliance is accurately held or maintained within the temperature range for which the switch mechanism is adjusted. It should also be noted from FIGURE 9 that the on and 8 off periods of energization of the appliance occur at substantially uniform periods of lapsed time, providing for a more even temperature of the appliance.

With this arrangement, the circular electrically energizable heater or element 86 is within the peripheral confines of the annular insulating members of the switch support stack and hence substantially all of the heat generated by current flow through the resistance heater 86 is transferred by conduction through the components in the stack to the supported area of the bimetal element 66 whereby improved control of heat transfer to the bimetal element is obtained over prior constructions.

The construction lends itself to varying the control of transfer of heat to the bimetal element. If a more rapid transfer of heat to the bimetal element 66 is desired, then the flange 56 of the insulating member 54 may be reduced in thickness to change the heat conducting path from the heater to the bimetal element.

The thickness of the circular-shaped

mica insulators

166 and 166 may be modified to vary the rate of heat transfer to the thermoresponsive element. If retarded transfer of heat is desired, the thickness of the flange 56 may be increased to thereby increase the length of the heat transfer path through the support stack.

With such arrangement the bimetal element 66, while under the influence of heat from the base member 11, receives heat by conduction through the support stack and by convection from the base member 11. The supplemental heat from the heater 86 may be modified as abovementioned to vary the amplitude of temperature differentials between current on and ed periods as well as the frequency of the on and off cycles depending upon the characteristics of control desired for the appliance.

The switch mechanism embodying the supplemental heater means, shown in FIGURE 2, may be used for controlling the temperature of an appliance with the switch mechanism disposed in a position remote from the influence of heat from the appliance. For such uses, the switch means is referred to as a cycling switch. Thus in use of the switch mechanism at a region not under the influence of heat from the appliance, the on and off periods of energization and de-energization of the appliance through the switch mechanism may be varied or modified by changing the rate or rapidity of transfer of heat through the support stack to the bimetal element 66, the supplemental heater being the only source of heat directly influencing the bimetal element.

The effective length of the resistance path of the resistance heater element shown in FIGURES 4 through 7 may be varied by changing the relative position of rotation of each of the insulating members 106 and 106' with respect to the bridges I02 and 104 between the annular portion and the semicircular

terminal leg portions

97 and 95 Thus by further rotating the mica insulating disc 106 in a counterclockwise direction, as viewed in FIGURE 6, the effective length of the leg portion 99 in contact with the terminal 58 is shortened.

By rotating the disc 106' a further distance in a clockwise direction as viewed in FIGURE 7, the slot 112 is moved farther away from the slot 99 and the length of the leg 97 in contact with the switch member 44 is shortened. By thus shortening the length of contact of the

legs

97 and 99 with the terminal 58 and switch member 44 respectively, the effective length of the resistance path of current flow through the heater is increased.

Thus the eifective resistance of the heater in developing heat from current flow therethrough may be varied in a measure by adjusting the relative rotational positions of the insulating

discs

166 and 106. After assembly of the insulating members, switch components, bimetal element 66 and the heater unit 86 on the sleeve 18, the swaging of the sleeve as at 68 compacts the assembly to hold the Q components, including the mica insulating discs 105 and 106, in assembled relatively fixed positions.

FIGURE 10 illustrates a modified form of generally circular resistance heater for incorporation in the support stack of the switch mechanism. The resistance heater 140 comprises a spirally configurated strip 142 providing an annular shape, the inner diameter of the open area defined by the spiral being of a dimension to slidably fit over the insulating member 54 shown in FIGURE 1. The strip 142 is comparatively thin and is of a width and thickness to secure the desired resistance factor to provide supplemental heat in the switch support stack. Insulating washers or discs of mica 106a and 106m, which are slotted as at 112a and 112aa, provide for assembling the insulating discs with the heater strip 142.

The heater strip 142 is preferably provided with two slightly offset

portions

144 and 146 to facilitate assembly and positioning of the insulating discs 1116a and 166m therewith. The spiral strip 142 has terminal portions 148 and 150 for contact respectively with the switch arm 44 and the terminal 58 when the heater construction of FIGURE 10 is embodied in the switch construction of FIGURE 1 in lieu of the heater unit 86. In assembling the disc 106ml with the heater strip 142, the slot 112aa accommodates the offset 144 whereby the terminal portion 148 of the heater strip 142 is above the insulating disc 106aa.

In assembling the insulating disc 106a with the heater strip 142, the slot 112a accommodates the offset 146 whereby the terminal portion 150 is beneath the insulating disc 106a. The effective resistance heating area or length of the heater strip 142 is the circular distance between the offset

regions

144 and 146 which distance is schematically indicated by the circular line 152, this portion being insulated by the insulating discs from the terminal portions 148 and 150.

It is to be understood that the effective length of the resistance portion of the strip indicated by the line 152 may be lengthened or shortened by changing the relative positions of the offset portions 144.and 146 so long as the resistance path is less than a complete circle and the offset

regions

144 and 146 maintained out of alignment or registration. The inner diameter of each of the insulating discs 106a and 106ml is of a dimension to snugly fit over the insulating member 54 shown in FIGURE 1. Thus the heater construction shown in FIGURE 10 in a stacked switch construction supplies supplemental heat for influencing a bimetal element such as bimetal element 66 of FIGURE 1.

FIGURE 11 illustrates another modification of resistance heater of a circular type for assembly within the confines of a switch support stack. The heater construction 1d0, shown in FIGURE 11, comprises a resistance element 162 which may be resistance wire of circular cross section, shaped to a spiral configuration with the circular area encompassed by the spiral of a dimension to snugly fit on the insulating member 54 shown in FIGURE 1.

The configuration of heater 160 is similar to that shown in FIGURE 10, the wire having offset

regions

164 and 166 providing

terminal portions

168 and 170 for contact respectively with the switch arm 44 and the terminal 58 when embodied in the switch construction shown in FIG- URE 1 as a supplemental support stack heater.

In this form, annularly-shaped mica insulating discs or members 106 b and 1106b]; are assembled with the resistance wire 162 in a manner similar to that shown in FIGURE 10. In assembling the insulating disc 106bb with the resistance wire 162, the slot 112bb accommodates the offset 164 with the terminal portion 168 above the insulating disc 106bb. In assembling the insulating disc 1116b with the resistance heater, the slot 112 b accommodates the offset 166 and the terminal portion 170 is beneath the insulating disc 1116b.

The effective spiral resistance path is that portion of the resistance wire 162 between the offset

regions

164 and 16 166, this circular path being indicated schematically by the circular line 172. The heater and insulating disc components shown in FIGURE 11, assembled as above described, may be embodied in the switch stack of the character shown in FIGURE 1 to provide supplemental stackconducted heat for influencing the bimetal element.

The effective resistance heating length of the Wire 1162, viz the length of the path indicated by the circular line 172 may be lengthened or shortened by changing the positions of the offset

regions

164 and 166 so long as the circular path 172 is less than a complete circle and the offset

regions

164 and 166 maintained out of alignment or registration.

FIGURE 12 is a fragmentary sectional view similar to a portion of the construction shown in FIGURE 1 illustrating a means of controlling or retarding heat transfer from a heated appliance to the bimetal element in order to vary the heat transferred from the appliance to the bimetal element. As shown in FIGURE 12, the appliance includes a base plate 11' to which is attached the stacked switch mechanism by means of a member 22 extending through the support sleeve 18 of the switch support stack. The switch includes a first switch arm 40' and a second switch arm 44 having cooperating contacts 42' and 46 and a thermoresponsive means or bimetal element 66' arranged to influence the position of the switch arm 40 through an insulating strut 76.

These components are mounted in a stack in the same manner as shown in FIGURE 1, the stack including a supplemental heater unit 6! or one of the heater constructions shown in FIGURE 10 or FIGURE 11.

Disposed between the flange 62 of the metal sleeve 18' and the bimetal element 66' is an insulating member 176 which may be mica, lava, ceramic or other suitable heat resistant insulation material. The insulating member 176 retards heat transfer from the appliance member 11' to the bimetal element 66' enabling a degree of control of the cycling of the switch even though the bimetal element 66' is also responsive to heat from the appliance 11'.

FIGURES l3 and 14 illustrate a removable unit control for a cooking appliance, such as a skillet or fry pan 180 equipped with an electrically energizable heating unit 182 provided with male terminals 184 for connection with a removable heater control unit 186 for the skillet or other appliance. The skillet or cooking appliance 181 is equipped with a cylindrically-shaped heat transfer projection or heat conducting portion 188 preferably disposed midway between the male terminals 184 as shown in FIGURE 13, the projection 188 being adapted to conduct heat from the skillet or appliance 180 to the control unit 186.

The terminals 184 are insulated from the metal utensil by insulating members 193. The circuit controlling unit 186 is arranged to be readily connectable with and removable from the appliance 180.

The switch mechanism is of the stacked switch type including a circular stack heater construction of the in vention and is enclosed within a suitable housing 192 fashioned of rigid molded insulating material such as Bakelite having a base portion 194 and a cover portion 195. The base portion and cover portion mate at a juncture line 196 and are held together by screws 197.

The base and cover sections of the housing are shaped to provide recesses 198 accommodating female-type connector clips 2% which engage the terminals 184 when the control unit 186 is in operative connection with the appliance Enclosed within the housing 192 is a stacked switch mechanism of the character illustrated generally in FIGURE 1 and includes a support plate 160, a first switch arm 400, a second switch arm 440, a bimetal element or thermoresponsive means 116a and a supplemental heater 86c which are assembled on a member 18c which, in the arrangement shown in FIGURE 14, may be either of solid cross section or of the tubular shape.

appliance 180. threaded openings accommodating a threaded The switch members are respectively provided with contacts 42c and the for controlling a circuit through the The support plate lbc is provided with shaft 2&2 equipped with a manipulating knob 2%. A rigid strut "i i-c is disposed between the threaded shaft 202 and the switch member 440 for manually adjusting the relative position of the switch member 440 for the temperature range desired for the appliance.

The support stack arrangement of the switch construction includes a heat conducting or heat transfer member or bar 268 having a fiat portion 2163 which is assembled in the stack support construction and is preferably in direct contact with the bimetal element 660 for transferring heat to the bimetal element. Also assembled in the stack switch construction is a plate or contact member 2110 which is intercalated in the circuit and is engaged by lower terminal portion of .the supplemental heater 860, the upper terminal portion of the heater directly engaging the switch arm Me in the same manner as illustrated in FIGURE 1.

As shown in FIGURE 14, the current conducting member 210 is connccted in the switch circuit and is engaged by a lower terminal of the supplemental heater construction 86c. Annular insulating members mounted on the member 180 insulate the switch members and the member 210 from the member 180. A supplemental heater 860 is in circuit with the switch arm his in the same manner as illustrated in FIGURE 1 and is energized when the contacts 420 and dds are engaged to establish current flow through the supplemental heater 36c and through the appliance when the clips Ztlii are engaged with the terminals 184.

The heat transfer member or bar 2&8 is fashioned with I a comparatively shallow recess 212 which receives the heat transferprojection 188 when the connectors or terminals Ztltl and 184 are in fully engaged relation.

The heat from the appliance heating unit 132 is transferred by the projection 18% and the bar 2% to the bimetal element 66:: for influencing the relative position thereof to automatically control the appliance within the heat range for which the manually actuable switch arm 440 has beenadjusted.

The supplemental heater ssc supplies additional heat conducted through the support stack to the bimetal element 65c in the manner hereinbefore described in reference to the switch mechanism shown in FIGURE 1 for preventing initial over-run of the temperature of the appliance and to obtain repetitive cycling action through making and breaking the circuit through the contacts 420 and 460 to obtain a temperature control of the appliance of the character illustrated schematically in FIGURE 9.

The control unit receives current through conductors L1 and L2 connected with a conventional current supply. The control unit 186 is provided with a transparent Window 214 anda pilot light (not shown) disposed beneath the window 214 for indicating to a user when an energizing circuit is completed through a switch mechanism to the appliance, the light being intercalated in the circuit in a conventional manner so that it is de-energized when the circuit is interrupted by separation of the contacts 420 and 460.

Thus, the supplemental heater 860 provides heat for accelerating the action or movement of the bimetal element are to control the temperature of the appliance. It is to be understood that the heater constructions shown in FIGURES l and 11 may be embodied in the switch construction shown in FIGURES l3 and 14 in lieu of the supplemental heater construction 86c. The arrangement in FIGURES 13 and 14, embodying the circular supplemental heater construction, provides for transfer of heat through the support stack of the switch arrangement to the bimetal element by conduction and thereby effecting a more accurate control of the heating of the 7 l2 appliance as exemplified in the graphic representation of FIGURE 9.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

We claim:

ll. Switch mechanism, in combination, switch. means including a relatively movable switch arm, a pair of cooperating switch contacts, one of said contacts being carried by the switch arm, a bimetal member, support means for said switch arm and bimetal member including insulating means retaining said arm and bimetal member in spaced relation, said bimetal member being disposed to inliuence the relative. position of the other of said contacts, an electrically-energizable heating element mounted by said insulating means having an annularlyshaped heating portion and terminal portions for connection in circuit with said contacts, disc means of insulating material embracing both sides of the heating portion of said heating element intermediate the terminal portions, said heating element and disc means being mounted by the insulating means whereby heat generated by current flow through the heater is conducted to the bimetal member through the insulating means.

2. Switch mechanism, in combination, switch means including a relatively movable switch arm, a pair of cooperating switch contacts, one of said contacts being carried by the switch arm, a bimetal member, insulating means retaining said arm and bimetal member in spaced relation providing a support stack, said bimetal member being disposed to influence the relative position of the other of said contacts, an electrically-energizable resistance heating element mounted by said insulating means having an annularly-shaped heating portion and terminal portions for connection in circuit with said contacts, disc means of insulating material embracing both sides of the heating portion of said heating element intermediate the terminal portions, said heating element and disc means being mounted in the support stack whereby heat generated by current flow through the heater is conducted through the stack to the bimetal member.

3. Switch mechanism, in combination, switch means including relatively movable current conducting switch arms, a'bimetal thcrmoresponsive member, an end region of each of said switch arms and bimetal member being supported by circular members of insulating material providing a support stack, an electrically energizable heating means including a circularlyehaped resistance element having an annularly-shaped heatin portion and terminal regions in circuit with said switch means, a pair of discs of insulating material respectively embracing both sides of the heating portion of said circularly-shaped heating element, said heating element and the discs of insulating material being disposed in the support stack whereby heat from the resistance element is conducted to the bimetal member through the stack to control the relative position of one of said switch arms, and manually actuable means for controlling the relative position of the other of the switch arms.

4. Switch mechanism including, in combination, a support member, insulating means including annular members of insulating material disposed in stacked relation on the support member, switch arms mounted in spaced relation by the insulating means, said switch arms having cooperating contacts, a bimetal element mounted on said support means, strut means between said bimetal element and one of said switch arms adapted to engage and influence the relative position thereof upon fiexure of said bimetal element, a resistance heating element mounted by the insulating means having an annularly-shaped heating portion and terminal regions for connection in circuit with said contacts, disc means of insulating material em- 13 bracing both sides of the heating portion of said heating element intermediate the terminal portions, said annularly-shaped heating portion being disposed within the peripheral confines of the disc means whereby heat generated by current flow through the heating element is conducted through the support means to the bimetal element.

5. Switch mechanism including, in combination, support means, a pair of flexible switch arms insulatingly mounted by the support means and having cooperating contacts, a bimetal element mounted by the support means and having insulating means arranged to engage one of said switch arms for influencing the relative position thereof, a resistance heating element insulatingly mounted by said support means, said heating element having an annularly-shaped heating portion and terminal portions connected in circuit with one of said switch arms whereby current flow through the heating element is controlled by engagement and disengagement of the contacts, annularly shaped insulating discs embracing both sides of the heating portion intermediate the terminal portions, the annul'arly-shaped heating portion of the heating element being disposed within the peripheral confines of said insulating discs whereby heat generated by current flow through the heating element is transmitted by conduction through the support means to the bimetal element.

6. Switch mechanism, in combination, switch means including a flexible switch arm, a pair of cooperating switch contacts, one of said contacts being carried by the switch arm, a bimetal element, support means for said switch arms and bimetal element including circular members of insulating material arranged in a stack, said bimetal element being disposed to influence the relative position of the other of said contacts, an electrically energizable heating element having an annularly-shaped resistance heating portion and curved terminal leg portions integrally connected with the resistance heating portion, the terminal leg portions being in annulated relationship with the heating portion, a pair of annular discs of insulating material, each disc having a radial slot, said discs being disposed respectively at opposite sides of the annularly-shaped resistance heating portion with the slots accommodating the terminal leg portions for insulating the annularly-shaped resistance heating portion from the terminal leg portions.

7. Switch mechanism, in combination, switch means including a flexible switch arm, a pair of cooperating switch contacts, one of said contacts being carried by the switch arm, a bimetal element, support means for said switch arms and bimetal element including circular members of insulating material arranged in a stack, said bimetal element being disposed to influence the relative position of the other of said contacts, electrically energizable heating means including a circularly-shaped heating element having an annularly-shaped resistance heating portion and annularly-shaped terminal leg portions integrally connected with the resistance heating portion and in annulated relation therewith, a pair of annular discs of insulating material, said circularly shaped heating element and said discs being mounted on and surrounding the support means, each disc having a radial slot accommodating a terminal leg portion, one of said discs being disposed between one major surface of the annularlyshaped heating portion and one terminal leg portion and the other of said discs being disposed between the other major surface of the heating portion and the other terminal leg portion for spacing the annularly-shaped heating portion from the terminal leg portions.

-8. Switch mechanism, in combination, switch means including a flexible switch arm, a pair of cooperating switch contacts, one of said contacts being carried by the switch arm, a bimetal element, support means for said switch arm and bimetal element including circular members of insulating material arranged in a stack, said himetal element being disposed to influence the relative position of the other of said contacts, electrically energizable heating means including an annularly-shaped heating portion and curved terminal portions disposed in said stack, a pair of insulating discs disposed respectively at opposite sides of said heating portion for spacing the heating portion from the terminal portions, said heating portion and terminal portions being within the confines of said insulating discs and in circuit with said contacts whereby current flow through said heating element when said contacts are in closed position establishes heat conducted through the stack to said bimetal element for actuating the bimetal element.

9. Switch mechanism, in combination, switch means including a flexible switch arm, a pair of cooperating switch contacts, one of said contacts being carried by the switch arm, a bimetal element, support means for said switch arm and bimetal element including circular members of insulating material arranged in a stack, said bimetal element being disposed to influence the relative position of the other of said contacts, electrically energizable heating means including a circularly-shaped element in said stack, said heating element having a circular slot and a radial slot forming an annular resistance heating portion and two terminal portions, said terminal portions being in annulated relation with the annular heating portion and integrally joined with the annular heating portion by connecting bridge portions defined by the radial slot whereby current flows from one terminal portion through the annular portion to the other terminal portion, a pair of insulating discs adjacent said heating element, one of said discs being disposed between one major surface of the annular heating portion and a terminal portion and the other of said discs being disposed between the other major surface of the heating portion and the other terminal portion for spacing the annular heating portion from the terminal portions, said heating element being within the confines of said insulating discs and in circuit with said contacts whereby current flow through said heating element when said contacts are in closed position establishes heat conducted through the stack to said bimetal element for actuating the bimetal element.

10. An accelerating heater for a stacked switch construction embodying a thermoresponsive means influenced by the heater comprising a circularly-shaped heating element having an annular resistance heating portion and annularly-shaped terminal leg portions integrally connected with the resitsance heating portion and in annulated relation therewith, a pair of annular discs of insulating material, each disc having a radial slot accommodating a terminal portion, one of said discs being disposed between one major surface of the annular heating portion and a terminal portion and the other of said discs being disposed between the other major surface of the heating portion and the other terminal portion for spacing the annular resistance heating portion from the terminal leg portions whereby current flows through the resistance heating portion in a circular path from one terminal leg to the other.

11. An accelerating heater for a stacked switch construction embodying a thermoresponsive means influenced by the heater comprising a circularly-shaped heating element having an annularly-shaped resistance heating portion and curved terminal leg portions integrally connected with the resistance heating portion and interiorly annulated within the heating portion, a pair of annular discs of insulating material, each disc having a radial slot accommodating a terminal leg portion, one of said discs being disposed between one major surface of the heating portion and a terminal portion and the other of said discs being disposed between the other major surface of the heating portion and the other terminal portion for spacing the annularly-shaped resistance heating portion from the terminal leg portions whereby current flows in a circular path through the resistance heating portion.

12. An accelerating heater for a stacked switch construction embodying a thermoresponsive means influenced by theheater comprising an electricallyenergizable circularly-shaped heating element having a circular slot and a radial slot forming an annular resistance heating portion and annularly-shaped terminal portion in annulated relation with the heating portion, said terminal portions being integrally joined with the annular portion by connecting bridge portions defined by the radial slot whereby current flows from one terminal portion through the annular portion to the other terminal portion, a pair of insulating discs adjacent said heating element, one of said discs being disposed between one major surface of the annular heating portion and aiterminal portion and the other of said discs being disposed between the other major 16 surface of the heating portion and the other terminal portion for spacing the annular portion from the terminal portions, said heating element being within the confines of said insulating discs.

References Cited UNITED STATES PATENTS 8/1958 Huffman 200-122 X 6/1965 Levinn 200-122

Claims

1. SWITCH MECHANISM, IN COMBINATION, SWITCH MEANS INCLUDING A RELATIVELY MOVABLE SWITCH ARM, A PAIR OF COOPERATING SWITCH CONTACTS, ONE OF SAID CONTACTS BEING CARRIED BY THE SWITCH ARM, A BIMETAL MEMBER, SUPPORT MEANS FOR SAID SWITCH ARM AND BIMETAL MEMBER INCLUDING INSULATING MEANS RETAINING SAID ARM AND BIMETAL MEMBER IN SPACED RELATION, SAID BIMETAL MEMBER BEING DISPOSED TO INFLUENCE THE RELATIVE POSITION OF THE OTHER OF SAID CONTACTS, AN ELECTRICALLY-ENERGIZABLE HEATING ELEMENT MOUNTED BY SAID INSULATING MEANS HAVING AN ANNULARLY SHAPED HEATING PORTION AND TERMINAL PORTIONS FOR CONNECTION IN CIRCUIT WITH SAID CONTACTS, DISC MEANS OF INSULATING MATERIAL EMBRACING BOTH SIDES OF THE HEATING PORTION OF SAID HEATING ELEMENT INTERMEDIATE THE TERMINAL PORTIONS, SAID HEATING ELEMENT AND DISC MEANS BEING MOUNTED BY THE INSULATING MEANS, WHEREBY HEAT GENERATED BY CURRENT FLOW THROUGH THE HEATER IS CONDUCTED TO THE BIMETAL MEMBER THROUGH THE INSULATING MEANS.