US3399366A - Thermoresponsive snap action switch - Google Patents

Description

Aug. 27, 1968 Filed May J. w. HUFFMAN A3,399,366

THERMORESPONSIVE SNAP ACTION SWITCH Aug. 27, 1968 J. w. HUFFMAN 3,399,366

THERMORESPONSIVE- SNAP ACTION SWITCH Filed May 9, 196e 2 sheets-sheet z ,4T Tom/5y l United Se@ Patent t 3,399,366 THERMORESPONSIVE SNAP ACTION SWITCH John W. Huffman, Mansfield, Ohio, assgnor, vby mesne assignments, to Emerson Electric Co., St. Louis, Mo.,

a corporation of Missouri Filed May 9, 1966, Ser. No. 548,476

- 8 Claims. (Cl. 337-365),

ABSTRACT 0F DISCLOSURE This invention relates to thermostat snap switches and more especially to a snapk action switch construction ernbodying a thermore'sponsive'me'ans arranged to provide a toggle action for effectively biasing a switch member to circuit making or circuit'breakingpositions.

Thermostat control: switches have been utilized wherein an actuating member anda'switch member are connected through themediuin of an arcuately shaped spring rnernber wherein the positionY of the actuating memberis varied or controlled by an independent thermoresponsive means or bimetal element acting through the actuating member to provide 'a toggle action responsive` to positions of the actuating member under the influence of the-independent therrnoresponsive means.V A thermostat snap action switch of this character isidisclosed inapplica'nts Patent 3,004,124 granted Oct. l0, 1961'.` 4 fThe'present inventiorrembraces"aswitch means ar'- ra'nged for snap action embodying a resilient thermorespons'ive means having direct 'connection with a relatively movable contact carrying switch lrnemberwhereby flexure of lthe resilient thermoresponsive means directly controls the position' of the movable4 switch member for engaging and disengaging contacts by snap action.

`An objectjof "the invention embraces a-thermoresponsive snap` action switch in which aresilient bimetal element has direct articulatevconnection with a relatively movable-contact-carrying switch member for cooperation with/a second contact whereby snapl action of the 'switch l member is attainedfthrough re'lativeimovementof' the bimetal element under temperature variations to provide a snap action switch whereby a-hi'g'h' degree of sensitivity of temperature control is attained. v

Another object fof the invention is the provision of a snap'action switchY wherein the frame or mounting means comprises similarly shaped support members maintained in spaced relation by insultating means, the arrangement embodyingva relatively movable switch arm having a contact cooperating with a'sec'ond'contact, and-a resilient bimetal elementarticulately connectedwith the movable switch member to obtain snap Yaction of the switch member wherein-the operative components of the switch ar'e disposed Vbetweenfthe'support membersproviding a compact, highly sensitive switch 'means which'is reliable in its operation. i i v f l Another objectief. the invention =is the Iprovision of a thermoresponsve snap switch embodying a bimetal element direct-ly engaging a movable switch member to obtain snap action wherein the sensitivity of operation of ice the snap action may be adjusted by means cooperating -With the bimetal element whereby the switch mechanism is effective to maintain ambient temperatures within extremely small temperature differentials.

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 to 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 a top plan View of the switch mechanism particularly illustrating a housing for the switch and mounting means; j

FIGURE 2 is is an end view of the arrangement shown in FIGURE 1; v

FIGURE 3 is a side elevational view of the arrangement shown in FIGURE 1;

FIGURE 4 is a side elevational view illustrating one form of thermostat snap switch of the invention;

FIGURE 5 is a top plan view of the switch construction illustrated in FIGURE 4;

FIGURE 6 is an isometric View illustrating the movable switch member of the switch construction shown in FIG- URE 4;

FIGURE 7 is an isometric view of a form of bimetal element for actuating the movable switch arm;

FIGURE 8 is a greatly enlarged fragmentary detail sectional view taken substantially on the line 8-8 of FIGURE 1;

FIGURE 9 is an end View of the bimetal element illustrated in FIGURE 7;

FIGURE 10 is an end view of the switch construction shown in FIGURES 4 and 5 with the housing removed;

FIGURE l1 is an isometric view of a component of the support means of the switch construction shown in FIG- URES 4 and 5;

FIGURE 12 is a side elevational view illustrating a modified form of snap switch of the invention;

FIGURE 13 is an end view of the switch construction shown in FIGURE 12;

FIGURE 14 is a side elevational view illustrating a further modification of snap switch construction of the invention, and

FIGURE 15 is an end View of the in FIGURE 14.

The switch mechanism of the invention is adapted for controlling the energization of an electrically energizable instrumentality under the inuence of variations in ambient temperatures, the switch construction having particular utility in controlling electrical circuits for electrically energizable heaters, air conditioning equipment, refrigeration units or for controlling any circuit where it is desirable to obtain a snap action to rapidly make or break an energizing circuit upon variations in temperature.

Referring to the drawings in detail, and initially to FIGUR-ES 1 through 5, the switch construction and housing arrangement are illustrated approximately double actual size. The switch mechanism 10 is inclusive of support means comprising spaced components or frame members 12 and 14 on which the elements of the switch construction are mounted as hereinafter described.

The frame component 12 is provided with a forwardly projecting tab or extension 16 and the frame component 14 provided with a forwardly extending tab or extension 18, the extensions projecting through openings in a mounting plate 20 fashioned of insulating material, such as Micarta, a phenolic resin-impregnated fibrous material. The projecting metal members 16 and 18 form terminals to which are connected conductors (not shown) to interconstruction shown calate the switch means in the circuitof the instrumentality to be controlled.

Each of the frame members 12 and 14 is fashioned with partially severed ear portions.`21, shown on member 14 in FIGURE 11, which in assembly with lthe mounting plate 20, arey swaged or bent to the position shown in FIGURES 1vand 5 to secure the switch construction to the plate-20. Theimounting plate may be provided with openings 22 to -accommodate bolts or other means for securing Lthe switch unit to a panel. As shown in FIG- URES.4 andS, the frame components 12 and 14 of the supportnmeans arey elongated and disposed `in parallel relation. l

A hollow housing 24 of rectangular cross section fashioned of molded resinous or plastic material. embraces or encloses theswitch construction as shown in FIGURES 1 and 3, the housing having an end wall 26 which, in assembly, is disposed. adjacent the distal ends of the frame members 12- and 14. The interior dimensions of the housing are such as `to enable the switch construction to be slidablytyet snugly received in the housing. The housing is maintained in assembled relation with the -switch construction in a manner lhereinafter described.

The frame component 12 fashioned of metal is provided with lengthwise extending reinforcing flanges 30 and the frame component 14 fashioned with lengthwise extending reinforcing flanges 32. vIn assembly, the flanges or reinforcing portions 30 and 32 extend in opposite directions as shown in FIGURES 8 and 10. The switch construction is inclusive of a relatively movable switch member or switch arm 36 of comparatively thin flexible metal. The switch member 36 is equipped with a contact 38 which cooperates with a contact 40 which, in the ernbodirnent illustrated, is carried by or mounted on the frame member 12.

The rear end region of the frame member 14 is fashioned with an upwardly extending portion 42 which provides a support or anchor for the movable switch member 36.

As particularly shown in FIGURE 6, the switch member 36 is fashioned adjacent one end with a transversely extending slot 41 which is adapted to receive ears or projections 43 on the portion 42, particularly shown in FIGUR-E 11, the' adj-acent surface of the switch member 36 abutting or engaging the upper ledge or surface 45 of the projection 42. In assembly after the switch member 36 is engaged with the surface 45, the ears or projections 43 are swaged or bent outwardly to the configuration shown in FIGURES and 10, providing a mounting for the switch member 36.

Also provided in the switch member 36 is a second transversely arranged slot 47, particularly sho/wn in FIG- URE 6. The slot 47 is of a length to provide connecting sections or bridge sections l49 connecting the anchored region 50 of the switch arm with the portion of the switch arm carrying the contact 38. The connecting or bridge sections 49 are of comparatively small cross section and provide hinge regions or pivot zones to facilitate movement or flexure of the portion of the switch member carrying the contact 38. y

-In order that exing or h-inging take place at the hinge or pivot regions 49, the switch member 36 is provided with laterally extending lengthwise arranged flanges 52 terminating adjacent the hinge regions 49 of reduced cross section. The hinge regions 49, in effect, provide a pivotal axis or zone for movement of the contact-carrying portion of the switch arm 36.

The switch construction embodies a thermoresponsive means or bimetal element or component 54 which is resilient and is arranged to provide a snap action movement of the switch arm 36 upon temperature variations in the region of the bimetal element 54. The bimetal element 54 comprises a uniplanar or rectilinear portion 56 and an arcuately shaped portion 58 as particularly shown in FIGURES 4 and 7. The planar portion 56 of the bibeing positioned between the ear portions. or projectionsv 4 metal member' or component-54 is anchored in the manner illustrated in FIGURES 4 and 8. As particular-ly shown in FIGURE 8, there is disposed between the frame members 12 and 14, blocks 60 and 62 of rigid insulating material. f'

IDisposed-between the adjacent `suritacesfof blocks 60 and 6,2 is theplanr portion 56 ofthe bimetal element54. As shown in FIGURES 4 and 5, theupper frame'mernber 12 is provided withintegral downwardly-extending ear portions 64 and thelower'frar'ne member 14 is provided with upwardly-extending integral'ear portions 66, the -insulating block 60 being positioned between theear portions or projections 64 and the insulatingblock 62 66. f The frame components 12 and 14, the blocks 60f. and 62 and they adjacent region of the planar portion-56 `of thev v bimetal element 54 4are fashioned with aligned openings to snuglyv receive a cylindrical sleeve 70 of rigid insulating material, the assembly 'being illustrated in FIGURE 8.` Extending through the insulating cylinder 70 isa tubu-l lar member 72. Disposed contiguous with the upper planar surface of the frame component 12 is a block` 74l of insulating material, and disposed below and contiguous with the planar surface-of frame component 14 is a sec.- ond block 76 of insulating material.

The blocks 74 and 76 are fashioned with counterbores 78 and with openings accommodating the cylindrical metal member 72. In assembly, the end 4regions of the tubular metal member 72 are swaged as at 80 into the counterbores 78 to secure the components in assembled relation. The blocks '60 and 62 with the portion 56 of the bimetal element disposed therebetween provide means for positioning the framev members 12 and 14 in proper spaced relation. The opening l81 in the bimetal element 54- shown in FIGURE 7 accommodates the insulating sleeve 70 as shown in FIGURE 8.

With particular reference to FIGURE 6, the central region of the switch member 36 is fashioned with an. opening 84 and with an integral projection or tab portion 86 extending into the opening. In assembly of the switch construction as shown in FIGURE 4, the curved or arcuate-shaped portion 5'8 of the bimetal component 54 is disposed in they opening 84 in the switch member 36. The distal region 88 yofk the arcuate portion 58 of the bimetal element 54` is fashioned with a transversely extending narrow slot or opening 90.

The. projection or tab 86 on the switch member 36 extends into the slot-90 in the arcuate portion 58. With the portion 86 extending into the slot 90, the edge regions 92 of the switch member 36 at the sides lof the projection "86 engage the arcuate portion 58 of the bimetal component 54 as shown in FIGURE 4.

In order to provide for increased flexibility of the arcuate portion 58 with respectto the remainder of the.

bimetal element 54 to attain a highly sensitive snap action for the switch member or arm 36, the region ofthe arcuate portion adjacent the integral juncture of -the arcuate portion 58 with the planar portion 56, is fashioned with a transversely extending slot 96, shown in FIG- URES 7 and 9, forming hinge regions98 provided by the bridging portions at the regions 98, which are of com paratively small cross sectional area to provide Hex-ing or hinge zones to facilitate flexing of the arcuate portion 58 with respect to the planar portion 56. f

As shownin FIGURE 4, the arrangement includes abutment means for limiting -thev downwardrelative movement of the switch member 36 effecting separation of thecontacts 38 and 40, 'the abutment means lbeing a. struck-up projection integral with -the frame com-v ponent 14 as shown in FIGURES 4 and 11.-'It 'is tofbef* understood that vother suitableabutment means mayli'be employed for limiting the movement 'of the switch-'arm 36 in `contact 'disengaging position. The planar portion 5:6*v of' the bimetal'element'54 is fashioned with an opening 102, shown in FIGURE 7, to accommodate the abutment or projection 100. ,y

Means is provided for adjustably regulating thevposition of a portion of the bimetal element 54 to regulate or control the sensistivity of snap action movement of the switch arm 36 under temperature differentials. As shown in FIGURE 4, a disc 106 isfused or bonded to the frame component 14 at its central region beneath the planar portion 56 of the bimetal element 54. The disc 106 and the adjacent portion of the frame member 14 are provided with aligned threaded openings to accommodate an adjusting screw 108, the upper end 110 of the screw providing an abutment engageable with theplanar portion 56 of the bimetal element at a zone spaced Va short distance from the distal end of the planar portion to partially -restrict llexure of the bimetal element in one direction.

Adjustment of the relative position of the abutment 110 controls the sensitivity of the snap action movement of the switch member 36. The thermoresponsive means or bimetal component 54 is fashioned of two metals having dissimilar coeicients of expansion whereby `variations in ambient temperature cause exing or vrelative movement of the thermoresponsive means. The metals comprising the bimetal component may be :reversed in fabrication where flexure in reverse directions is desired.

Where the switch construction is utilized for controlling the motor circuit of an air conditioning or air cooling unit or instrumentality, the bimetallic element54 is fabricated whereby decrease in ambient temperature effects ilexure and movement of the arcuate portion58 to move the switch member 36 downward, as viewed in FIGURE 4, to separate the contacts 38 and 40.

Upon increase in the ambient temperature, the arcuate portion 58 is flexed upwardly to effect snap action of the switch member 36 to reengage the contacts and energize the motor of the air cooling unit being controlled.

. Where the switch mechanism is utilized to control a heating unit and it is desired to disengage the contacts upon an increase in temperature ambient the bimetal component 54, the metals of different coeicients of ex- .pansion are fabricated vin reverse relationl so that an increase in ambient temperature causes Yilexure of the bimetal element 54 to eifect snap action .movement of the switch arm 36 downwardly to separate the contacts and deenergize the heating unit or instrumentality in circuit with the switch mechanism. By properX adjustment of the abutment 110, snap action movement of the switch arm may be :attained by an ambient temperature of one degree F.0rless.

After the completion of the assembly of the components of the switch mechanism, as shown` in. FIGURES 4 and 5, the thin-walled housing 24 of resinous material or other insulating material having anl open end is telescoped over the switch assembly to ,theposition shown in FIGURES 1 and 3. The wall region of the housing adjacent .the frame component 12 is fashioned with an opening 111 to accommodate a headed pin or drive screw 112, as shown in FIGURE 8, which isdriven or pressed into the tubular member or sleeve 72 to secure the hous ing in enveloping relation with the switch mechanism. It will therefore be apparent that the switch may be utilized to control the motive means yof an air cooling unit or refrigeration apparatus or the switch may be used to control the energizationof a heating instrumentality where the heat from the instrumentality varies the temperature in the region of the switch mechanism.

FIGURES 12 and 13 illustrate a modification of thel switch mechanism of the invention. In this form the frame components 12', 14', the panel 20', terminals 16', 18', the bimetal component 54' and the mounting means for the bimetal component are the same as in the form of the invention shown in FIGURES 4 through 11. This form of the invention includes la flexible switch member or arm 114 provided with or carrying a contact 116 which cooperates with a relatively stationary contact 118 mounted -by the metal frame component 12'. The switch arm or member 1'14,` in this form of the invention, is mounted in a manner differently from that disclosed in FIGURE 4.

The mounting means for the bimetal elements 54' and the switch arm 114 is inclusive of a block 62' of insulating material disposed between the planar portion 56' of the bimetal component 54' and the frame component 14'.

The distal end region of the switch arm 114 is disposed between two ' blocks 120 and 122 of insulating material. The blocks of insulating material, the switch .arm 114 and the planar portion 56 of the bimetal element are provided with registering openings to receive a sleeve 124 of insulating material which is similar to the sleeve 70 shown in FIGURE 8.

The blocks 62', 120 and 122, an end region of the switch arm 114 and an end region of the bimetal element 54' are held in lixed relation by a metal sleeve 126 similar to the sleeve 72 shown in FIGURE 8, the ends of the metal sleeve 126 being swaged as at 128 into engagement with insulating blocks 74 and 76' to provide -a stacked construction for mounting the bimetal element 54 and the switch arm 114. The switch arm 114 is provided with an open region 130 similar to the open region 84 in the switch arm 36 shown in FIGURE 6. The switch arm 114 is provided with a projection or tafb portion 132 similar to the tab portion 86 shown in FIGURE 6.

The bimetal component 54' is fashioned with an arcuate portion 58' terminating in an end region 88' provided with a slot to receive the projection 132 providing an articulate connection between the switch arm 114 and the arcuate portion 58 of the bimetal element 54. The arcuate portion 58', near the region of its juncture with the planar portion 56' is fashioned with a slot 96' providing connecting regions or bridging sections 98 which form hinge zones to facilitate llexure of the arcuate portion 58' to obtain snap action movement of the switch arm 114.

The switch arm 114 is fashioned with llanges 134 which terminate a short distance from the mounting means providing an unilanged region adjacent the mounting means, as show in FIGURE l2.

This region of the switch arm 114 is provided with a transversely extending slot, corresponding to the slot 47 shown in the switch arm 36 in FIGURE 6, to provide hinge regions 136 for the switch arm of reduced cross section to facilitate pivotal or exing movement of the switch arm 114 about the hinge regions 136.

An abutment means mounted 'by the frame component 14' is provided for limiting the extent of movement of the distal end of the switch arm 114 away from the contact 118 when the contacts are separated under the inuence of the bimetal element 54'. As shown in FIGURE 12, a disc or member 140 is secured or bonded to the frame component 14' and the disc 140 and adjacent portion of the frame component 14' have aligned threaded Openings to accommodate an adjusting screw 142. By adjusting the screw 142 the extent of opening movement of the switch arm may be controlled.

,Means is also provided to adjustably restrict flexure of la portion of the bimetal component 54' and thereby regulate or control the sensitivity of snap action of the switch arm 114. Disposed beneath the planar portion 56' of the bimetal element 54' at a region spaced a comparatively short distance from the distal end region of the planar portion of the bimetal element 54' is an adjustable abutment in the form of a threaded member or screw 146.

Soldered or otherwise bonded to the frame component 14' is a disc-like member 148, the disc-like member and the adjacent region of the frame component 14 having aligned threaded openings to laccommodate the adjustable abutment lor screw 146, the upper end 147 of the screw or member 146 being disposed for engagement with the planar portion 56' of the bimetal element.

The abutment positions. the bimetal element to restrict flexure in a downward direction to regulate the sensitivity of the snap action. Through this adjustable means, the snap action sensitivity may be adjusted to eect snap action under a desired differential in ambient temperature. It is found that through this adjustment, snap action movement of the switch arm may be attained by an ambient temperature change of one degree F. or less.

FIGURES 14 yand 15 illustrate a further modification of the snap action switch of the invention. In this form the frame components 12, 14, the insulating panel 20" and terminals 16", 18 are the same as in the form of construction shown in FIGURES 4 through 11. The switch mechanism includes a llexible switch member or arm 154 provided with a contact 156 which cooperates with a relatively stationary contact 158 mounted by the meal frame component 12". The switch arm or member 154 is mounted in the same manner as the switch arm shown in FIGURE 12.

The switch construction shown in FIGURES 14 and 15 includes a bimetal element or thermoresponsive means 160 having a planar portion 162 and a curved or arcuate portion 164 integral with the planar portion 162, the latter being mounted at one end in the same manner as illustrated in FIGURE 12. The mounting means for the bimetal element 160 and the switch arm 154 includes a block 62" of insulating material disposed between the portion 162 of the bimetal element and the frame component 14". The mounting end of the switch arm 154 is disposed between two blocks 120l and 122l of rigid insulating material.

The blocks 120, 122", the end region of the switch arm 154 and the end region of the planar portion 162 of the bimetal element are fashioned with registering openings to receive a sleeve 124" of insulating material. The insulating blocks and the adjacent regions of the switch arm 154 and the planar portion 162 of the bimetal element are held in fixed relation by a tubular metal member or sleeve 126 telescoped within the sleeve 124", the ends of the member 126" being swaged as at 128 into engagement with insulating blocks 74" and 76" providing a stacked construction for mounting the bimetal element 160 and the switch arm 154 and maintain the frame components 12" and 14" in spaced relation.

The contact 156 carried by the switch arm 154 is spaced from the distal end of the switch arm. The switch arm 154 is provided at its distal end with a tab or projection 166 engaging in a laterally extending slot in the end region 165 of the curved portion 164 of the bimetal element providing an articulate connection between the distal end of the switch arm and the arcuate portion 164 of the bimetal element.

The arcuate portion 164, near the region of its juncture with the planar portion 162, is fashioned with a laterally extending slot 168, shown in FIGURE 15, providing narrow connecting portions or bridges 170 which form hinge regions or zones to facilitate llexure of the arcuate portion 164 to obtain snap action movement of the switch arm 154. The switch arm 154 is fashioned with flanges 172 extending lengthwise of the switch arm at the edge regions, the flanges terminating short of the mounting means providing an unlianged region adjacent the mounting means as shown in FIGURE 14.

This unilanged region of the switch arm 154 is provided with a transversely extending slot corresponding to the slot 47, shown in the switch arm 36 in FIGURE 6, to provide hinge regions 174 for the switch arm which are of reduced cross section to facilitate pivotal or exing movement of the switch arm 154 about the hinge regions 136. An abutment means in the form of a struck-up projection 178 on the frame component 14" is adapted to be engaged by the switch arm 154 for limiting the extent of exure or movement of the switch arm away from the contact 158 when the contacts are separated under the influence of the bimetal element.

It is to be understood that an adjustable abutment screw, such as that illustrated at 146 in FIGURE 12, may be employed in lieu of the projection or abutment 178 in the switch shown in FIGURE 14 or the projection 100 shown in FIGURE 4. Joined to the frame component 14" is a disc 180, the disc and adjacent region of the frame component 14 having aligned threaded openings accommodating a screw 182 providing an adjustable abutment for restricting movement of the planar portion 162 of the bimetal element to control the sensitivity of snap action of the switch arm.

The upper end 184 of the screw 182 is adapted for engagement with the planar portion 162 of the bimetal element. By adjusting the screw 182, the sensitivity of the snap action may be controlled and thereby elect snap action under a desired differential in ambient temperature as in the other forms of the invention. The arcuate portion 164 of the bimetal element 160 extends beyond the distal end of the switch arm 154 rendering it unnecessary to provide any open areas in the switch arm between the hinge regions 174 and the zone of engagement of the switch arm with the curved portion 164 of the bimetal element.

The action or operation of the switch mechanism shown in FIGURES 14 and l5 is substantially the same as the action of the switch mechanisms hereinbefore described. Upon variations in ambient temperature, the bimetal element 160 is flexed and particularly through the ilexure of the curved portion 164 a snap action of the movable switch arm 154 is attained.

By adjustment of the abutment 182, the sensitivity of the snap action may be regulated to obtain action under various degrees of temperature or temperature diierentials. The switch arrangement is highly sensitive to minute temperature changes whereby snap action may be obtained with ambient temperature variations of one degree F. or less.

Through the arrangements of switch mechanism hereinbefore described, a highly sensitive snap action is attained with a minimum of moving components. The switch constructions are compact and are capable of carrying substantial currents in controlling circuits of heating devices, motors of air cooling units or other instrumentalities where accurate control is desired responsive to variations in ambient temperatures.

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

I claim:

1. Switch mechanism, in combination, a relatively movable current conducting member of planar shape provided with a contact, a second contact, means supporting the second contact, said current conducting member being movable to positions engaging and disengaging said contacts, a bimetal element formed with an arcuate portion and a planar portion, an end region of the arcuate portion having pivotal connection With the current conducting member, means mounting the planar portion of said bimetal element, the arcuate portion being provided with a region of reduced cross-section forming a hinge zone for said arcuate portion, said pivotal connection and the hinge zone being disposed with respect to the movable current conducting member whereby movement of the bimetal element under the influence of ambient temperature variations effects snap action movements of the current conducting member to engage or disengage the contacts.

2. The combination according to claim 1 including abutment means engageable with the bimetal element for impeding ilexure of the bimetal element in one direction.

3. The combination according to claim 1 including adjustable abutment means engageable with the bimetal element for reducing iiexure of the planar portion of the bimetal element in one direction.

4. The combination according to claim 1 including abutment means limiting the extent of movement of the current conducting member in contact disengaging position.

5. Switch mechanism, in combination, support means including substantially parallel spaced metal members and rigid insulating means disposed between the metal members, a relatively movable current conducting member of planar shape mounted by the support means and provided with a contact, a second contact mounted by the support means, said current conducting member being movable to positions engaging and disengaging said contacts, a bimetal element having a planar portion and an arcuate portion, said planar portion being mounted by the insulating means, the distal end region of the arcuate portion of the bimetal element having pivotal connection with the relatively movable current conducting member, said bimetal element having a weakened region interrnediate its ends providing a hinge zone for the arcuate portion whereby relative movement of the bimetal element under the influence of ambient temperature variations eifects snap action movements of the current conducting member to engage or disengage said contacts.

6. The combination according to claim 5 wherein the current conducting member is mounted on Ione of the metal members and the second contact mounted on the other metal member.

7. The combination according to claim S including an adjustable abutment engageable with the planar portion of the bimetal element for regulatingthe sensitivity of snap action of the current conducting member.

8. The combination according to claim 5 4wherein the rigid insulating means, the metal members and the planar portion of the bimetal element have aligned openings, a tubular member of insulating material extending through said openings, and means extending through said tubular member securing the rigid insulating means, metal members and the planar portion of the bimetal element in assembled relation.

References Cited UNITED STATES PATENTS 1,622,721 3/1927 Hook 200-138 X 2,634,350 4/1953 Mertler 200-137 3,004,124 10/1951 Huifman 200-138 3,322,921 5/1967 Bletz 200-113 FOREIGN PATENTS 575,605 5/1959 Canada.

5 BERNARD A. GILHEANY, Primary Examiner.

R. L. COHRS, Assistant Examiner.

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