US2267546A - Thermostatic switch - Google Patents

Description

Dec. 23, 1941. y C, J WERNER 2,267,546

THERMOSTATIG SWITCH Filed Aug. 28, 1940 2 sheets-Sheet 1 C) 44 36 y, a4 1 T f' 2 z Il' (46a`\ 3 54 4o 'l 2 43 sa 44 33 ATTORN EYS yDec. 23, 1941. Q J, WERNER 2,267,546

THERMOSTATIC SWITCH Filed Aug. 28, 1940 2 Sheets-Sheet 2 20 25 v 7/ //VETHL 2, 7 W www ATTORNEYS Patented Dec. 23, 1941 THERMOSTATIC SWITCH Calvin J. Werner, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 28, 1940, Serial No. 354,601

(Cl. 20D-113) 11 Claims.

This invention relates to improvements in a control device for an electric circuit.

It is among the objects of the present invention to provide an electric circuit control device adapted automatically to open and close in accordance with predetermined conditions in the flow of current through said device.

In a control device of this type the normally closed contacts are opened with a s-nap action when overloads or other certain conditions in the circuit occur, said contacts remaining open for a predetermined interval and then returning automatically to circuit closing position.

Another object of the present invention is to provide an electric control device, capable of automatically opening and closing the circuit in response to predetermined conditions, with means for rendering the automatic return of the device to its circuit closing position ineffective, this object including also the provision of means for manually actuating the device to its circuit closing position.

A still further object of the present invention is to simplify and reduce the number of parts of a device of this type by providing a single means selectively operable, in one direction to render the device entirely automatic in its operation to control the circuit, and operable in a second direction to render the automatic return of the device to circuit closing position ineffective and thus to require manual actuation of the device to close the circuit and operable in a third direction to actuate the device to such circuit closing-position.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a plan view of the thermostatic switch or control device with the cover for the casing removed.

Fig. 2 is a part-sectional view taken along the line 2 2 of Fig. 1, certain parts, however, being shown in elevation for the sake of clearness. In this view the contacts are shown in engagement.

Fig. 3 is a view similar to Fig. 2, however, here the contacts are shown disengaged and the device set for manual re-engagement of the contacts.

Fig. 4 is a view similar to Fig. 2, however, in this instance the switch parts are shown in a position capable of automatic re-engagement of the contacts.

Fig. 5 is a fragmentary, detail sectional view taken along the line 5-5 of Fig. 1, and showing the manual operative member and its retaining element in automatic reset position.

Fig. 6 is a view similar to Fig. 5, the parts, however, being shown in the manual reset positions.

Fig. 7 is a fragmentary, detail View of the over-center mechanism of the thermal element and contact.

Referring to the drawings, the numeral 20 designates the casing of the device, said cas-ing being made of any suitable insulating material. At one end of the casing there is provided a lug 2| forming a platform which supports one end of the stationary contact arm 22. This contact arm is secured to the platform by a terminal stud 23, the threaded end of said stud extending beyond the one side of the casing and having a lock nut 24. A contact 25 has a s-tem portion extending through an opening in the arm 22, this stern portion being rigidly secured to the free end of a spring blade 26, the opposite end thereof being anchored to the arm 22 under the head of the terminal stud 23.

A terminal bolt 3|) extends through a wall of the casing 20 and secures the U-shaped supporting element 3| within ,said casing. This U-shaped supporting element 3| has two spaced, upstanding arms 32 and 33 between which the pivot pin 34 is supported. An arm 35 provided with spaced parallel ears 36 and 3l is hingedly supported by the pivot pin 34.

One end of a bimetallic arm 40 is secured to the arm 35 adjacent its pivotal support on pin 34. A pigtail connection 4| has its one end riveted to the arm 35 and its other end clamped between the head of terminal stud 30 and the supporting member 3|. It provides a flexible electrical connection between said terminal and thermal strip 40. A contact element 43 is secured to the free end of the bimetallic strip 40 so as to cooperate and be engageable with the stationary contact 25. The opposite edges of the bimetallic strip 40, adjacent its free end, have turned down ear portions 44 and 44a, each provided with a'V-shaped notch 45. As shown in Fig. 7, a U-shaped flipper element 4l has two parallel arms 48 and 48a, the arm 48 pivotally engaging the V-shaped notch of ear 44 on the bimetallic strip 40; the arm 48a of said iiipper pivotally engaging the V-shaped notch of the ear 44a. One end of what may be termed an over-center spring 50 is secured to the central portion of the iiipper 41. The other end of said spring 50 is anchored to an insulating block 5| secured to the bimetallic strip 40 adjacent its anchorage to the arm 35. It will be noted that in the position, as shown in Fig. 2, where the contact 43 engages the contact 25 the downward movement of flipper 41 is stopped by its engagement with the outer edges of the hole 52 in the bottom wall of the casing 20. When in the contact disengaging position, as shown in Fig. 3, the ears 44 and 44a engage the bottom of a recess 53, and the ilipper engages the ledge 54 thereby preventing further movement of this over center device in this direction.

The casing 20 has a tubular extension 60 from its one wall, this tubular extension providing a sliding support for the manually operable member Si of the device. 'I'his member has a head portion 62 of greater transverse dimensions than the inner bore of the tubular member 60 so that in one position the head will engage the outer annular edge of the tubular extension 60, as shown in Fig. 5. The body portion of the member 6I smaller in diameter than the head portion 62 slidably ts within the tubular extension 60. In the outer surface of this body portion of the member 6I there is provided a semi-spherical notch 54 and diametrically opposite the semispherical notch 64 an elongated groove 55 is also provided. The casing 20 of the switch has a lug portion 66 at one side of the tubular extension 50 this lug portion being provided with a channel 5l for receiving a ball member 68 which is yieldably urged into engagement with the body portion 63 of the member 6l by a U-shaped spring member 59 positioned in a channel crossing the recess 51 and being substantially parallel with the axis of the manually operable member 6l. lin one instance Fig. 5, this ball check 58 seats into the semi-spherical recess Sli in the operating member Si thereby retaining or locking said operating member in one position in the tubular extension 5@ as shown in Fig. 5. However, the manually operable member 5i may be rotated 180 as shown in Fig. 6, so that the ball check 58 no longer seats within the semi-spherical recess 5d but in the rounded, elongated slot 55 under which circumstances movement of the member 5i longitudinally of its axis may be eiected. As shown in the drawings, a screw stud l@ is threaded into a central passage in the body portion of the operating member Si. This screw stud l has a head ll. The body portion o the stud 'ill passes through an opening in the pivoted lever 35. A spring 'l2 is interposed between the lever 35 and the adjacent end of the manually operable member i, said spring yieldablv urging the end of the arm 35 into contact with the lower surface of the head 'Il of the stud l0. Thus a lost motion connection is provided between said manually operable member El and pivoted arm 35.

As has been stated in the preamble of the specification one object of the present invention is to provide an electric circuit control device which is adapted automatically to open and close in accordance with predetermined conditions in the flow of current through said device, such predetermined conditions comprising in certain instances overloads in the circuit. 1f for instance an excessive current flows from the terminal 30 through the pigtail connection di and bimetallic arm across contacts 43 and 25 through the arm assembly including' members 22 and 25 to the terminal 23. said bimetallic strip would heat up causing it to fiex. Normally the thermal strip 40 is -bowed upwardly, as regards the drawings, due to the tension of spring which exerts. a pull in' one direction upon the block 5I secured to the strip 40 adjacent its one end and a pull in the direction upon the iiipper 41 engaging the ears 44 and a of said strip adjacent its other end. This upward bow of the bimetallic strip 40 under. normal unheated conditions will be gradually increased by'the heating up of said strip due to an excessive current iiow therethrough. More specifically heating of the strip will increase its normal bow in the same direction. As the strip 40 tends to flex or bow in response to being heated up its ends will tend to bend downwardly, however, only the free, contact carrying end may so move inasmuch as the other end thereof is pivotally anchored. The spring 50 will resist such downward movement of the arm 40 slowly to separate its contact 43 from the stationary contact 25. Such resistance to the slow movement of the arm 40 away from contact 25 is maintained until suicient energy is built up in the bimetallic strip 40, due to its exing, to overcome the opposing effort of the over-center spring 50. As soon as thiscondition is reached the spring 50 will give way to the greater builtup energy in the bimetallic strip 40 thereby resulting in the movement of the contact carrying arm i0 away from contact 25 with a snap action into the position as shown in either Fig. 3 or Fig. 4.

When a manual reset of the switch is desired, the operating button or member 6I is rotated so that its elongated slot receives the ball check 58. Now the member 6I is free to move longitudinally.

It has been stated that iiexing of the thermal strip ill due to heat will cause its ends to move downwardly while its center portion buckles upwardly. The one end, anchored to the pivoted arm 35 cannot move downwardly like the opposite end of the strip, however, in its effort to move downwardly, the anchored end of the strip will exert a force upon the pivoted arm 35 urging its free end upwardly so that it will urge the stud 'i5 with its head upwardly and thus hold the operating member 5l in the position as shown in Fig. 2 as long as the heated strip is flexing its ends downwardly. Downward iiexing of the contact carrying end of strip fi will bring the contact point of iiipper il and strip ears Ml and lila below the center line of the over-center spring 56 thus the contact end of strip il'i is held in its over-center, contact breaking position as shown in Fig. 3. lThe circuit through the thermal strip i0 having been broken, said strip will begin to cool gradually and due to such cooling, return to normal shape. Its end now tends to move slowly upwardly. The contact carrying end is held down by the nvdr-center spring 50 while the upward effort of the opposite, anchored end will result in a counter-clockwise turning of its arm 35 about the pivot pin 36. As the outer end of arm 35 moves downwardly during gradual cooling of the thermal strip 40, it exerts a push on spring 72, moving the operating arm downwardly into the position shown in Figs. 3 and 6 at which time the thermal strip has assumed its normal shape.

To again close contacts 25 and d3, it will be necessary to push the operating member 6l-62 from the position shown in Figs. 3 and 6 into the position shown in Figs. l, 4 and 5 in which the head 62 engages the end of the tubular extension 60 of the switch case. Pushing the head 62 inwardly causes the spring 12 to move arm 35 upwardly or clockwise from its position as shown in Fig. 3. The thermal strip 40 being in normal condition will be tensioned or flexed by the clockwise rotation of the arm 35 to which one endof it is anchored so that the downward, over-center effort of spring 50 is overcome, causing a quick return of the strip to contact making position when the point of contact between the flipper and ears is moved above the center line of the said spring.

Thus when the manually operable member 6I is rotated so that the ball 68 extends into the elongated slot 65 of said member, movement of the bimetal arm 40 from contact engaging position into contact disengaging position will longitudinally move the manually operable member` so that return of the contact 43 into engagement with contact 25 is effected only by the manual operation of the element 6I from the position shown in Figs. 3 and 6 to the position shown in Figs. 2 and 5.

To attain the first-mentioned object of the present invention in accordance with which the circuit control device automatically returns to circuit-closing position after having been automatically' moved out of circuit engaging position it is necessary to rotate the manually operable member GI so that ball 68 will enter the semi-spherical recess 64. With the ball in this recess the manually operable member 6I will be retained in the position as shown in Figs, 2, 4 and 5 and longitudinally axial movement thereof will be opposed and substantially prevented.l

As has been previously stated, heating up of the bimetal strip 40 due to an excessive current ilow therethrough will cause said strip to ilex. The number 6I, being immovable and connected with the strip 40 by the spring 12, stud 10 and arm 35, will consequently hold the end of the strip attached to arm 35 likewise immovable and connected with the strip 40 by the spring 12, stud 10 and arm 35, will consequently hold the end of the strip attached to arm likewise immovable so that only the free, contact carrying end thereof may move when the strip flexes.

As shown in Fig. 4, when the point of contact between the flipper 41 and ears 44 and 44a of the strip passes below the center line of spring 59, said spring will quickly move the end of the strip against the`bottom Wall of the casing as shown in the Fig. 4, holding it there for a predetermined time. Now as the strip 40 cools, its free end will flex upwardly gradually, due to the tension built up in the strip during its flexure downwardly in response to heat and due to the fact that its one end is held immovable. When the point of contact between the flipper 41 and ears 44 and 44a passes the center line of spring on its return movement upwardly, said spring will quickly snap the strip into contact making position.

While the operating member is locked against longitudinal movement as shown in Fig. 5, the

device will be set for automatic operation, that is, the thermal strip 40, flexed into the contact open position by heat, will be returned to contact making position automatically upon cooling, On the other hand, if the operating member is adjusted to the position as shown in Fig. 6, when cooling of thethermal or bimetal strip 40 may move the said member longitudinally, then cooling of said strip merely moves the member from the position shown in Fig. 2 to the position shown in Fig. 3 under which condition manual actuation of member 60 is required to again return the contact carrying strip 40 to its contact making position.

Spring 12 has another function which is of a protective nature particularly where the device is subjected to excessively low temperatures ambient thereto. Such low temperatures may be encountered when mechanisms equipped with the device are placed in transport such as in unheated freight cars, trucks and the like and particularly in the winter season. The thermal strip 40 when subjected to excessively low ambient temperatures will flex, its center portion bowing downwardly toward the base of the casing 20, the ends tending to move in the opposite direction so that contact 43 would exert an undue pressure upon contact 25. If the supporting end of the thermal strip would be rigidly mounted such ilexing of the strip might put a permanent set in 'the strip, thereby entirely destroying its original shape and adjustment which would result in improper operation of the device under normal circumstances. However, in the present invention the thermal strip 40 is hingedly supported, the hinged armto which said strip is secured engaging the spring 'I2 so that any tendency of the strip end to move upwardly as aforedescribed will rotate the hinge arm 35 counterclockwise thereby compressing the spring T2 and thus relieving the strain on the strip. Spring 12 is designed and constructed that it will offer the proper resistance to movement of the arm 35 to assure predetermined functioning of the strip under the desired normal circumstances. However if abnormal ambient temperatures as aforedescribed are met, then the spring l2 will be compressed by movements of the arm 35 resulting from strip flexing due to such abnormal temperatures.

It is also to be understood that the operating member E2 may not only be actuated by pushing thereon to effect engagement of the contacts, but it may also be pulled out to separate the contacts, such pullingr out of the said member moving the arm 35 counterclockwise, exerting a biasing force through the strip 4U to overcome the overcenter spring 50 and its cooperating elements, moving them from the contact closing to the contact opening position.

From the aforegoing it may be seen that applicant has provided a switch of simple structure and design employing a minimum number of parts to attain the desired objects which include provision of an electric circuit control device adapted when adjusted to one position, automatically to open and close a circuit in accordance with predetermined conditions in the ilow of current through said device and when adjusted to another position provides for automatic opening of the circuit closing device, but requires manual operation to again establish contact engagement.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A thermostatic switch comprising in combination, cooperating contacts; a bimetal arm earrying one of said contacts; a hinged member supporting said arm; biasing means adapted to urge said arm and its hinged member from one position to another with a snap action under certain conditions; and means adapted to be actuated for locking the hinged member against movement to effect automatic return of said arm to said one position.

2. A thermostatic switch comprising in combination, a contact movable between two extreme positions to open and close a circuit; a bimetal arm supporting said contact; a hinged member supporting the arm; biasing means adapted to move said arm and hinged member into one or the other of their extreme positions with a snap action, into said one position in response to ilexing of the-bimetal arm due to heat and into the other due to manual shifting of the hinged member; and means adapted to be actuated for lockv-ing said hinged member to effect automatic return of said arm instead of by the manual means.

3. A thermostatic switch comprising in combination, a contact movable between two eX- treme positions to open and close a circuit; a bi-metal arm carrying said contact; a hinged member supporting the arm; biasing means adapted to move said arm and hinged member into one of their extreme positions with a snap action in response to -flexing of said arm due to heat and adapted to move said arm into' the other extreme position in response to actuation of the hinged member; manual means for actuating the hinged member; andmeans for locking the manual means and hinged member in one position whereby the bimetal -arm will move automatically from said one extreme position into the other extreme position.

4. A thermostatic switch comprising in combination, a contact movable into circuit open and closed positions; a bimetal arm carrying said contact; a hinged support for said arm; biasing means adapted to move'the hinged member and said arm into the circuit open position with a snap motion in response to exing of the arm due to heat, andadapted to move said arm into circuit closing position -in response to manual actuation of the hinged support; means for actuating said hinged support; and means for retaining said actuating'means and' the hinged supportl in one position whereby the bimetal arm will return automatically to circuit closing position after a predetermined coolingof the arm.

5. A thermostatic switch comprising 'in combination, cooperating contacts; a bimetal arm carrying one of said contacts; a hinged member supporting the arm; biasing means adapted to move the hinged member and said arm into contact engaging or contact separating positions with a snap action upon occurrence of certain conditions; manually' operable means operatively connected to the hinged member for operating it to move the bimetal arm toward contact engaging position, and means adapted to be actuated to retain the manual operable means in one position to lock the hinged member against movement whereby said bimetal arm will automatically return to contact engaging position.

6. A thermostatic circuit controller comprising in combination, contact means movable between two positions to open and close the circuit; a bimetal arm carrying one of said contacts; a hinged member supporting said arm; means including an over-center spring for actuating the hinged member and said arm into the circuit open position after heating of the bimetal arm and its resultant exing has built up suiilcient energy in the arm to overcome the actuating it to ex the bimetal arm sufliciently to overcome the effect of the over-center spring to maintain the arm in circuit open position, and means adapted to be actuated to retain said manual means in one position for locking the hinged member so that the bimetal arm will automatically return to circuit closing position when sufficiently cooled.

'7. A thermostatic switch comprising in combination, cooperating contacts, one of which is movable between two extreme positions to open and close a circuit; a bimetal arm carrying said one contact; a pivoted member supporting said arm; biasing means adapted to move said arm into either one of its extreme positions with a snap action; an actuator movable with said pivoted member as the bimetal arm moves from its circuit closing to circuit opening position, said actuator being manually operable to effect the return of the said arm to its circuit closing position; and a detent adapted to engage the actuator and retain it in its normal position, whereby the pivoted member is locked against movement and the bimetalarm will, under certain conditions,` automatically return to its circuit closing position.

8. A thermostatic switch comprising in combination, cooperating contacts, one of which is movable between two extreme positions to open and close a circuit; a bimetal arm carrying said one Contact; a pivoted member supporting said arm; biasing means adapted to move said arm into either one of its extreme positions with a Snap action; an actuator operatively connected to the pivoted member said actuator being moved longitudinally by the said member following the movement of the bi-metal arm into circuit breaking positionl manual operation of said actuator longitudinally in the opposite direction eiecting return of the arm to itscircuit closing position; and a detent rendered effective by the rotation i of the actuator, to lock the actuator and its connected pivoted member in normal position whereby the bimetal arm will return .to its circuit closing position automatically upon proper cooling of said arm.

effect of said spring to hold it and the hinged member in circuit closing position; manual means connected with the hinged member for 9. A thermostatic switch comprising in combinatiomcooperating contacts, one of which is movable into and out of engagement with the other; a bi-metal strip carrying said one contact at its one end; a pivoted lever having the other end of the bi-metal strip attached thereto; means including an over-center spring for moving said strip into or out of contact engagement with a snap action, an actuator operatively engaging said pivoted lever and movable longitudinally by said lever when the bimetal strip moves into the contact disengaging position, said actuator being manually returnable to its normal position to effect movement of said strip to its contact engaging position; and a ball-check retainer, rendered eective by rotation of the actuator to lock said actuator and pivoted lever against movement in response to movement of the strip to contact disengaging position; whereby automatic return of said strip to contact engaging position is effected.

10. In a thermostatic circuit interrupter, thermal means movable when heated to open the circuit and movable when properly cooled to close the circuit, a pivoted bracket supporting said means, means. including an over-center spring for shifting the thermal means into its circuit open or closed positions with a snap action; manually operable means connected to the bracket and moved thereby when the thermal means is moved into its circuit open position said manually operable means being adapted to be actuated to rotate the bracket for returning the thermal means to circuit closing position, and means for locking the manually operable means against movement by the bracket, whereby pivotal movement of the bracket is prevented and automatic return of the thermal means to circuit closing position eiected.

11. A circuit control device comprising in combination, cooperating contacts one of which is movable into and out of engagement with the other, a bimetal strip pivotally mounted at one end and carrying said one contact at the other, said strip iiexing in response to heat, to urge its contact toward contact disengaging position and when cooled suciently again returning to contact engaging position, biasing means including an over-center spring adapted to urge the bimetal strip to one or the other of its positions with a snap action, a bracket pivotally supporting the bimetal strip, and means operatively engaging said bracket and being manually operable in three directions, one to lock the pivotal bracket against movement to eiect automatic return of the bimetal strip from its contact disengaging into its contact engaging position. the second to free and permit movement of the pivotal bracket and thereby prevent such automatic return of the strip to its contact engaging position and third to actually move said pivotal bracket to effect return of said strip to contact engaging position.

CALVIN J. WERNER.

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