US2870290A

US2870290A - Wiring device

Info

Publication number: US2870290A
Application number: US556953A
Authority: US
Inventors: Owen L Taylor; Clarence M Smith
Original assignee: Bryant Electric Co
Current assignee: Bryant Electric Co
Priority date: 1956-01-03
Filing date: 1956-01-03
Publication date: 1959-01-20
Anticipated expiration: 1976-01-20
Also published as: GB805410A

Description

Jan. 20, 1959 o. L. TAYLOR ETAL & 9

WIRING DEVICE Filed Jan. 3, 1956 2 Sheats-Sheet Insulufion ,a

izi/17 7 Jan. 20, 1959 'o. L. TAYLOR ETAVL 3 3 WIRING DEVICE Filed Jan. 3, 1956 2 Sheets-Sheet 2 United States Patent O WIRING DEVICE Owen L. Taylor, Easton, and 'Clarence M. Smith, Trumbull, Conn., assignors to The Bryant Electric Company, Bridgeport, Conn., a corporation of Connectcut Application January 3, 1956, Serial No. 556,953

19 Claims. (Cl. 200-113) Our invention relates to a wiring device and, more particularly, to an innitely variable position electrical switch for controlling the energzation of an electrical heating element.

As is Well known, it is desirable that the electrical switches used for controlling the heat dissipation of an electrical heating element in house-hold appliances, such as ranges, be of an infinite range in order to obtain an infinite range of heat dissipation from the heating element. Prior devices for such purposes have not been entirely satisfactory as they have employed relatively expensive Components which have, in many instances, re-

` 'quired careful handling and assembly in order to prevent their being damaged and in order to insure their proper functioning. As can be appreciated, such procedures have increased the cost of the switch.

Accordingly, one object of our nvention is to provide a new and improved electrical switch of simplified construction having an infinite number of control positions between given limits.

Another object of our invention s to provide a new and improved electrical switch of simplified Construction with an infinite number of control positions between given limits, and having a pair of opposed bimetal means connected together at one of their ends, which in conjunction with moveable means, can be utilized to vary the length of time a heating element is energized.

Another object of our invention is to provide a new and improved electrical switch of simplified Construction with 'an infinite number of control positions between given limits having a pair of opposed elongated bimetal means connected together at one of their ends, and movable means for causing one of the bimetals to be stressed through a variable range of stresses.

Another object of our invention is to provide a new and improved electrical switch of simplified Construction with an infinite number of control positions between given limits having a single rotatable handle to provide a positive oil position at which all circuits controlled by the switch are deenergized.

Still another object of our invention is to provide a new and improved electrical switch of simplified construction with an infinite number of control positions between given limits having movable bimetal elements one of which supports one contact of engageable Contacts, and which has a readily accessible adjustment screw for calibration means.

A more specific object of our invention is to provide a new and improved electrical switch of simplified construction having an infinite number of control positions between given limits, and having a pair of opposed bimetal elements connected at one of their ends, with the other end of one bim-etal element being fixed, and with the other end of the other bimetal element being pivotably movable.

Another more specific object of our invention is to provide a new and improved electrical switch of simplified Construction having an infinite number of control positions between given limits and having a U-shaped member, the arms of which are formed by bimetal elements, and a rotatable handle located between the bimetal elements and which is rotatable to stress the U- shaped member through an infinite range of stresses.

Still another object of our invention is to provide a new and improved electrical switch of simplified construction having an nfinite number of control positions between given limits which is formed from simple components arranged in a compact manner.

These and other objects of our invention will become more apparent upon the following detailed description of preferred embodiments of our invention when taken in conjunction with the attached drawings, in which:

Figure 1 is a top plan View of a switch constructed in :ccordance with the principles of our invention with the cover and Operating means therefor removed;

Pig. 2 is a sectional view of the switch shown in Fig. 1 inverted about a longitudinal axis and with the Operating means located therein and which has been taken substantially along the line II-II of Fig. 3;

Fig. 3 is a central cross-sectional view of the switch shown in Fig. 2 taken along the line III--III of Fig. 2;

ig. 4 is an enlarged top plan view of another switch constructed in accordance with the principles of our invention with the cover and Operating handle therefor rcmoved;

Fig. 5 is a cross-sectional view of the switch shown in Fig. 4 taken along the line V-V thereof with a portion of the Operating cam being broken away;

Fig. 6 is a circuit diagram of a heating element and a control means therefor as shown in Figs. l to 3;

Fig. 7 is a circuit diagram of a heating element and a control means therefor as shown in Figs. 4 and 5;

Fig. 8 is an enlarged top plan view of the composite bimetal element utilized in the switch as shown in Figs. l-3, and

Fig. 9 is an enlarged exploded perspective view of the cross link and portions of the bimetals extending therefrom as used in the switches of our Construction.

Referring to Figs. 1 to 3, the embodiment of our invention therein illustrated comprises a rectangular, onepiece, cup-shaped housing 2 having longitudinally extending laterally spaced

side walls

8 and 9 which are connected at their ends by means of laterally extending end walls 12. Housing 2 nay be formed from any suitable insulating material, and is preferably formed from a molded plastic material, which may readily be formed as hereinafter described. As shown, a pair of laterally spaced terminals 4 and 6 are located inwardly adjacent one end wall 12 of housing 2, and a similar terminal 10 is located inwardly adjacent the opposite end wall 12.

Terminals

4, 6 and 10 may be made from any suitable electrical conducting material, such as an alloy of copper, and are each provided with integral connector engaging portions which extend through a cooperable slot (not shown) in the base 13 of the housing 2 and outwardly from the outer side of base 13 of housing 2 so that wiring connections may readily be made thereto externally of the housing 2. Such outwardly extending Connector engaging portions are shown in Fig.3 only for the terminals 4 and 6; however, terminal 10 is similar thereto. The portions of

terminals

4, 6 and 10 which eXtend inwardly of housing 2 are larger than the Slots through which the Connector engaging portions extend so that

terminals

4, 6 and 10 may readly be located in place by merely inserting the Connector engagng portions through the slots in the base 13, and thereafter wedging a portion of the Connector engaging portion into firm engagement with the outer surface of base 13. It will also be noted that the inwardly extending portion of terminal 10 is located on approximately the longitudinal center line of housing 2 and extends longitudinally between the end walls 12. Terminals 4 and 6 extend longitudinally between end walls 12; however, they are spaced laterally on opposite sides of the longitudinal center line of housing 2, with terminal 4 bein'g'oifset towards one side wall 3 of housing 2, and terminal '6 being offset toward the other side wall 9.

Terminals 4 and 6 can each be electrically connected to terminal 10 by means of generally longitudinally extending

brushes

14 and 16, respectively. One end of each of the

brushes

14 and 16 is formed to extend adjacent the inwardly located portion of terminal w, so that brushes 14- and 16 may be electrically and mechanically Secured thereto in any suitable manner, such as by means of rivets 13.

Brushes

14 and 16 are formed from any suitable electrical conducting material, such as an alloy of copper which has sufficient resilency to normally bias the opposite free ends of

brushes

14 and 16 into firm engagement With terminals 4 and 6, respectively. The free end of brush 16 is provided with a laterally extending arcuate surface 15 for engaging the surface of terminal 6 facing side wall 9. Brush 16 is utilized to control a pilot light, and accordingly, it does not carry any substantial amount of current so that such contact engagement is satisfactory. Brush 14 is, however, a line current-carrying member, and in order to minimize arcing damage when brush 14 engages and disengages the surface of terminal 4 facing side wall 9, the opposed portions of terminal e and brush 14 are provided with arc

resistant contacts

17 and 19, respectively, which may be formed from any suitable arc resistant material, such as silver or an alloy thereof.

Contacts

19 and 17 may be Secured to the brush 14 and terminal 4, respectively, in any suitable mannensuch as by being riveted thereto.

It will be noted that brush 16 is formed so that the portion inwardly adjacent terminal lt) extends at an angle toward side wall 9, and thereafter is formed to provide a straight portion whichextends toward the 'inner portion of terminal 6. The straight portion of brush 16 is provided approximately centrally thereon with an integral inwardly extending integral projection 22. The portion of brush 14 intermediate its fixed and free ends is generally U-shaped with its arms extending outwardly away from each other, and with its bight portion 24 being located approximately parallel to and adjacent to the straight portion of brush 16. Bight portion 24 is also oifset from the longitudinal center line of housing 2 toward side wall 9 of housing 2.

Brushes

14 and 16 are operated by means of a formed cam 26 which is rotatably supported within the housing t 2, and is formed of any suitable insulating material, such as a molded plastic material which may readily be provided with the necessary structure as hereinafter described. As shown, the cam 26 is provided with a central axially extending circular opening 28 through which an elongated Operating shaft 30 extends. Shaft 30 may be formed from any suitable material having sufiicient structural strength, such as steel. In order to rotatably support the inner end of shaft 30 within the housing 2, the inner surface of the base 13 is provided with a circular recess 32 in which the circular inner end of shaft 3@ is rotatably received. If desired, a boss 34 may be provided which extends inwardly from base 13 of housing 2 for engaging the inner end of cam 26 to support the cam 26 above the inner surface of base 13. In such event recess 32 is formed in the boss 34.

The entire open side of housing is enclosed by means of a cover 36, which may be formed of any suitable material, such as steel, and whichis Secured to the open side of housing 2 in any suitable manner, such as by means of projections at' the sides thereof, not shown, which are deformable to engage cam surfaces on the sides of the housing 2. Cover 36 is provided with an approximately central opening 21 which is in alignment with the recess32 into which the inner end ot shaft 36 d extends and is rotatably supported thereby. If desired, the outer end of shaft 30 may be provided with suitable means, such as a slot 38, to facilitate mounting a handle (not shown), thereon, whereby the shaft 30 may readily he rotated in order to accomplish the purposes hereinafter described.

Although cam 26 may be Secured to shaft 30 in numerous satisfact y ways toobtain rotation of the cam plate 25, with the snaft as shown, the opening 28 through the cam is enlarged at its outer end, and shaft 3@ is also enlarged so that the inner end of the enlarged portion of shait 38 is closely received therein. The enlarged portion of shaft Sl is of a non-circular cross section in order that catch 42 having a similarly shaped opening may be ed thereon and be non-rotatably supported by the t 33 so that rotation of shaft 3@ causes a corresponding rotation ot' catch 42. As shown, catch 12 is provided with a pair of inwardly extending lugs 43 which are closeiy received in inwardly extending recesses 54?, which extend inwardly from the outer surface of cam 26. Thus, rotation of shaft 3@ eauses lugs 48 of catch 42 to engage the sides of recesses E@ to cause a corresponding rotatio-n of cam 26. in order to locate catch 42 axially along shaft 3%, a suitable stop member may be secured to shaft 3@ for cngaging the inner surface of catch 42. Further, a spring Washer 46 may be located on shaft 35 between the cover and the catch 42 for biasing the catch :2 into engagement with the stop member 44 when the cover is assembled to the casing.

As best shown in Fig. 2, the inner end of the cam 26 is circular in form except for a narrow projection 52 extending radially outwardly therefrom. The inner end of cam 26 is of a size so that it may be freely 'otated without engaging the brush te adjacent thereto except that a projection 52 is of a size that upon such rotation it will engage the bight portion 24 of brush M to force brush towards side wall and separate the Contacts l!? and 19. Such movement of brush ?14 also causes the bight portion 24 to engage the projection 2.2 and force the brush 16 out of engagement with the terminal 6, Brush le is moved upon movement of the brush and is preferably formed from a resilient material which is of a smaller cross section than brush 14 as less current is carried by brush 16. The base l3 of housing 2 is preferably provided with an upwardly extending integral barrer Si which extends longitudinally between the inner por tions of terminals 4 and 6 to limit separating movement of the free end of brush 14- and prevent it from engaging the terminal 6.

As shown, an elongated, resilient, genorally longitudinally extending bimetal element 54 is located inwardly adjacent side Wall 3 with the end laterally spaced from terminal Ed, being Secured to a. terminal which is similar in Construction to terminal 1 3. Te'minal 56 is Secured to base 3.3 in a similar manner to terminal 10 so that the inner portion extends slightly angular from the adjacent end wall i?, toward side wall 8 so that bimetal 5 3 which, if freely supported would extend angularly toward side Wall 8. Eimetal element ay he formed in the well known manner from any suitable pair of dissimilar materials having difierent coefiicients of thermal expansion as are generally available eonmerciailyn One end of bi. ietal element 54 is ficedly Secured to the inner portion oi' terminal ss in any suitable manner, such as by rivets 57. A contact 58 similar to the

Contacts

37 and 19, previously described. is Secured to the opposite movable end of bimetal in any suitable manncr, such as by being riveted thereto. T he bimetal element 54 is arranged so that upon a rise in temperature the free end thereot will move toward side wall 3.

An eiongated longitudinally extending bimetal element se is located inwardly adjacent side wall 9 so that it extends generally longitudinally of side wall 9. Bmetal elemente@ is fabricated so as to have the same thermal and mechanical characteristics as bimetal element 54, 'and ecordingly, is preferably formed from the same material as the brnetalelement 54, however it is mounted to deflect in a-direction opposite to the deflection of bimetal element 54. As shown, the end of bimetal 60 is laterally spaced from the terminal 56 and is pivotally mounted to the housing 2, as hereinafter described, and the opposite movable end of bimetal element 60 is laterally spaced from the movable end of bimetal element 54. An elongated flexible cross link 62 of any suitable material, such as spring steel, extends laterally between the movable ends of

bimetal elements

54 and 60, and is located near the adjacent end wall 12 between the inner surface of this end wall 12 and the adjacent terminals 4 and 6.

As more clearly shown in Fig. 9, each end of cross link 62 is provided with an integral generally T-shaped por tion 63 with the stern portion thereof extending longi tudinally outward on substantially the lougitudinal center line of cross link 62. The stern portion of each end portion 63 is provided with a laterally enlarged portion 65 adjacent the cross bar portion. As also best shown in Fig. 9, the free end of each of the

bimetal elements

54 and 60 is provided with a T-shaped slot 23, with the stern portion thereof extending longitudinally inwardly from the free ends of the

bimetal elements

54 and 60. As can be appreciated each T-shaped slot 23 is of a size so that the stern portion thereof may be slipped over the stern portion of one of the T-shaped end portions 63, and the bimetal elements then moved toward the cross bar portion of the end portions 63. Enlarged portions 65 are of a size so as to be closely, yet freely, received within the cross bar portions of slots 23 whereby the

bimetal elements

54 and 60 are located laterally with respect to cross link 62. When

bimetal elements

54 and 60 are assembled with the cross link 62, the inner edges of the cross bar portion adjacent the enlarged portion 65 of each end portion 63 engage the portion of the

bimetal elements

54 and 60 cooperable therewith on their outer surface between the ends of the cross bar portion of slot 23 and the sides of the bimetal cooperable therewith. By such construction and by using a very thin steel strip for cross link 62, a knife edge bear-ing is obtained between each of the

bimetal elements

54 and 60 and the cross link 62. As will become more apparent hereinafter such knife edge bearings are normally loaded so as to oppose defiection of the

bimetals

54 and 60, due to mechanical thermal movement away from each other.

Due to the clearances required for the cooperation of slots 23 and end portions 63 as described, movement of

bimetal elements

54 and 60 in the same direction could result in the '

bimetal elements

54 and 60 being separated s from the cross link 62. In order to prevent such separation, of the cross bar portions of ends 63, a pair of laterally spaced tabs 67 are provided on each end of cross link 62 so as 'to be located at opposite ends of the enlarged portions 65 of end portions 63 and spaced laterally therefrom. As initially formed tabs 67 extend laterally outwardly from cross link 62, as shown in the lower portion end of Fg. 9, 'so that sufcient clearance is provided to permit ready assemblyof

bimetal elements

54 and 60 to cross piece 62. After assenbly, tabs 67 are bent down to approximately the same plane as the main body portionof cross piece 62, as shown in the upper portion of Fig. 9. When so bent tabs 67 prevent longitudinal movement of the cross bar portion of slot 23 of the

bimetal elements

54 and 60 inwardly away from the enlarged portions 65 of end portions 63. Tabs 67 are of a length so that when bent the ends of

bimetal elements

54 and 60 are freely received 'between the ends of tabs 67 and the inner edge of `the cross bar portion of ends 63.

aas 0,290

extends inwardly from bimetal element 54 andis Secured to the inwardly extending portion of terminal 64 in any suitable manner, such as by rivets 53. The bimetal element 66, as more clearly shown in Fig. 8, comprises a light resilient bimetal section 68 which is Secured to the terminal 64, and a heavier resilient bimetal section 70 which is Secured to the bimetal section 68 in any suitable manner, such as by being spot welded thereto. Bimetal section 70 is similar to the '

bimetal elements

54 and 60 previously described, and while the bimetal section 68 is also formed of two dissimilar materials, it is of substantially less thickness than

bimetal elements

54, 60 and 70. Bimetal section 68 is forrned from any suitable pair of dissimilar materials having different coefficents of thermal expansion as are generally available commercially. A contact 72 similar to the

contacts

17 and 19, previously described, is Secured to the free end of bimetal section 70 in any suitable manner such as by riveting, so as to be cooperable with the contact 58 on bimetal ele ment 54. It will also be noted that a portion of bimetal section 68 between terminal 64 and bimetal section 70 has been reduced in width to obtain a more rapid movement of contact 72 into and out of engagement with contact 58 on bimetal element 54, as hereinafter described.

Housing 2 is provided with an integral projection 73 which extends inwardly at the intersection of side wall 9 with the end wall 12 at the left (Figs. 1 and 2). Projection 73 is provided with a surface facing terminal 10 in which a generally V-shaped notch 74 is provided so that projection 73 may function as a pivot support. An elongated rigid cam follower 76, which may be formed from any suitable material having suflicient structural strength, such as steel, is provided, which extends generally longitudinally within housing 2 adjacent the side wall 9. As shown, one end of cam follower 76 is formed to provide a pair of spaced laterally outwardly extending projection& 78, the free ends of which are freely received within the V-shaped notch 74 in projection 73, so that cam follower 76 is pivotally supported therein. In order that projections 78 are retained within the notch 74, biasing means comprising generally omega-shaped leaf spring 80 is provided, which may be formed from any suitable thin spring material, such as spring steel. As shown, a projection 82 is provided on cam follower 76 which extends laterally therefrorn toward the side wall 8 and which is located between the projections 78. I

The housing 2 is also provided with an integral support 84 between the pivotally supported end of cam follower 76 and terminal 10 which extends inwardly from the base 13 and adjacent end wall 12 and which has a square cornered notch 85 therein facng the pivotally supported end of cam follower 76. With such Construction, the opposed ends of spring 80 may be inserted within the notch 85 and the intersection of the projection 82 with the cam follower 76, so that the arms of spring 80 are forced toward each other and the free end of cam follower 76 is initially biased toward sidewall 8.

One arm of spring 80 engages the projection 82 at a point otfset from the pivot axis formed by projections 78 and notch 74, so that the spring 80 biases the cam follower 76 clockwise and into engagement with the cam portion 94 of cam 26 through screw 95 with reference to Fig. 2, at all times. In addition it will be noted that the engagement of one arm of spring 80 with the corner of notch 85 and the other arm with the intersection of the projection 82 and the cam follower 76 are each knife edge bearings. Similarly the free ends of projections 78 are poiuted so as to engage the bottom of the U-shaped notch 74 on a knife edge hearing. Inasmuch as

bimetal elements

54 and 60 engage cross link 62 on knife edge bearings as previously described, the entire linkage system is relatively frictiou free. Also by locating projection 82 between projections 78, spring 80 will not exert any torsional forces upon the cam follower 76. It of course will be appreciated that in order to provide an initial bias t' on cam 'follower 76 and the knife edge bearings, the armsof spring 80 are initially stressed toward each other when inserted in position as described. Movement of cam follower 76 toward side wall 9 causes the central portion of spring 80 to be further compressed to further bias the cam follower 76 toward side wall 8.

t will particularly be noted that the opposed

bimetal elements

54 and 66 are located adjacent the inner surface of base 13 and thatthe cam follower 76 is spaccd outwardly from the inner surface of base 13 so as to be movable transversely across the outer edge or" bimctal element 60. In view of such location of cam follower 76, it is provided with an integral portion (not shown), adjacent its pivotally supported end (Fig. 2) which extends towards the base 132 so that the end ot bimctal element 60 spaced from the crosspiece 62 may be secured thereto in any suitable manner, such as by rivets 89. Thus, movement of cam follower 76 through a portion of its travel until

contacts

53 and 72 engage each other will cause a corresponding movement of the bin etal element 6% which, in turn, as previously stated, will cause a like movement of bimctal element 54-.

It will be noted that crosslink 62 is provided with an upwardly extending projection 9@ approximately centrally thereof, one side of which is engageable with the free end of cam follower '76. As will be more fully described hereinaiter, such engagement of cam follower '76 and projection 90 provides a positive ofl position t'or the switch. As shown, the central portion %7. of cam ollower '76 extends along side wall 9 with its free end eing ent to extend sharply toward the upper side wall The central portion 92 of Cam foliower '76 extends adjacent the irregularly formed cam portion 9 3 which is an integral portion of the cam 26. Engagement between cam portion 94 and cam follower '76 is obtained by means of the screw 95 threadedly engaging an opening in the central portion 92 of cani follower 76. lt will be noted that the end of screw 95 facing sidewall 9 is provided with a slot whereby the relative position between cam follower 76 and cam portion 94 may be varied. In order to facilitate such adjustment an opening 96 is provided in the sidewall 9 in alignment with the screw 95.

Referring to Fig. 6, it will be noted that a switch constructed in accordance with the principles of our invention is adapted to be used in the control of an electrical range heating element H of well-known construction. As shown, the opposite ends of heater H are connected by means of suitable electrical conductors tl and 121 to the terminals te and 64, respectively. minals l, 6 and 56 are connected to a suitable supply of electrical energy such as conductors LZ, N, LE, respectively, as are commonly employed in household range .circuits. As is common practice, conductors Lit, N and LZ are connected to the commonly available 236 volt altcrnating-current household circuit, with conductor N being connected to the ground or neutral conductor of the supply circuit.

Referring to Fig. 2, the switch heretofore described is shown in the oti position. in this position, prejection 52 engages the brusl .4 to force the brush 14 toward side wall E so that the Contacts i"? and ,t are separated. Such movement of brush l also moves brush 16 toward side wall 9 and disengagcs the terminal 6.

Cam portion 94 is located with respect to the proection 52 so that the maximum inward travel of bimctal element 6 3 is obtained when projection 52 engages brush ?ut which, due to the bias of spring %ti and cross linit 62, causes the maximum travel of bimeta 54 toward side wall 8. When so positioned, the contact 'on 'oimetal Ed and contact 72 on bimctal section ?E of bimetal 66 are separatedthe maximum amount, As cor taet' 58 is mountcd on bimctal element 754%, it ispossible that due to extreme cold bimctal element 54 may move Terinwardly toward the contact 72 by deflecting bimctal element 6@ ovcrconing the bias of spring 8@ to a degree, as its high expansion side faces bimctal 66. Therefore, in order to provide a positive offi the free end of cam follower 76 engages the side of projcetion 9 on cross link 62 facing side wall 9 which, due to the direct application of the bias of spring holds the bimctal element 54 away from bimctal element 66. Thiis, with such Construction, the projection 52 and the cam followcr 76 insure that all the contacts of the switch will bc separated and cannot be closed as long as the cam 26 is at its ot position.

Rotation of cam plate 26 in either direction will cause the projcctien 52 to disengage the 'night portion 24 of rus-h fa t so that, due to the resilicncy of

brushes

14 and 6,

contacts

17 and 19 will engage each other and the frcc end ot' brush i& will engage the adjacent surface of terminal 6. The preferred rotation of cam plate 26 for progressively increasing energization of the heating elcment H has been established as counterclocltwise with reference to Fig. Z or clockwise for the handlc on shalt 3& externally of the housing 7.. Such rotation of the shaft 3% is standard in the control of range heatcrs and, accordingly, the form of cam portion 94 has been dctermined for the particular characteristies dcsircd for such rotation and Will be discussed accordingly. lt is, oi course, obvious that if desircd the characteristies of the cam portion 'M could be determined for cloclse rotation with relation to Fig. 2.

Upon such counterclockwise rotation of cam 26:', the screw 95 is forced outwardly toward side wall 9 by cngagement with cani portion 94 which, in turn, causes the cant follower 76 to move toward side wall As bimetal element 60 is Secured to cam follower '76, it too is moved toward side wall i? and a similar movement of bimctal element 54 will also occur due to the cross lini; 62. It will be noted that, as shown in Fig. l, the engagcment of contact 58 with contact 72 cannot occur until the free end of cam follower 76 moves sutficicntly to ward side wall 9 to permit the protection 93 on cr link 62, in engagement therewith, to move the requLcd distance. Thus, cam portion 5 4 is designed to accelerate movement of cam follower '76 toward the side wall 9 upon countercloclwise rotation of cam 26 so that the contact SS on bimctal element 54 rapidly engages the contact '72 whereby arcing between the Contacts is minimized. Upon closure of the Contacts and 72, line current will flow from the conductor LE through terminal 56, bimctal element 5 3, contact 53-, contact '72, binetal sections es and 7@ of bimctal element 66, terminal 6 3, conductor 121, heating element H, conductor 12 terminal 3.8, brush l l, Contacts 19 and 75'?, and terminal S to the line conductor LZ. At the same time current will flow from terminal lt? through brush te, terminal 6, to conductor N. in order that some means may be provided for indicating that the switch is on, a pilot light P has been connected in the conductor N.

As has been indicated, bimctal element 66 is forned with two

bimctal sections

68 and 70. Although not shown, bimctal section 68 is assembled so that its low expansion side is located adjacent bimctal element 54 and bimctal section 76 is assembled so that its high ex pansion side is located adjacent bimctal element 54. With such Construction the two

bimctal sections

68 and 70 will tend to cause the opposite ends of bimctal element 66 to move in opposite directions due to changes in temperature. Such opposite movement of the opposite ends of bimctal element 66 will prevent the position of contact 72 from shifting to any substantial degree due to ambient temperaturcs between the

side walls

8 and 9. Inasmuch as bimctal section 63 has a small-:r section than bimctal section 7%, a given length of bimctal section 63 will deflect more than the same length of bimetal .section 70 fotthe same temperature ditterence because of its greater fiexibility. As bimetal section 68 9 is rigidly secured to terminal 64 at one end, the end connected to bimetal section 70 will deflect to move the bimetal section 70 bodily in one direction upon movement of the free end of bimetal section 68. Accordingly, in order to compensate for this movement, bimetal section 70 must be of a considerably greater length than bimetal section 68 so that the free end of bimetal section 70 will remain substantially at the same position regardless of variations in ambient temperature. Thus, the switch can be calibrated with reference to contact 72.

Upon counterclockwise rotation of cam 26, as indicated, the inner end of screw 95 will follow the outer contour of cam portion 94. In order to obtain movement of contact 58 toward contact 72, cam portion 94 is provided with an increased radius so that screw 95, and accordingly cam follower 76, is forced toward side wall 9. Such movement of cam follower 76 is provided initially by cam portion 94 until

contacts

72 and 58 just engage each other. Upon such initial engagement of

contacts

72 and 58, the switch may then be calibrated so as to determine the precise location of screw 95 with relation to cam portion 94 and cam follower 76. in view of the fact that such calibration is related to the operation of the switch, the method of calibrating the switch will be discussed hereinafter.

The passage of current through bimetal section 68 causes it to become heated and in order to obtain rapid heating bimetal section 68 is formed from a bimetallic material having a higher electrical resistance than the other bimetal elements. The reduced cross section of bimetal section 68 also causes it to become heated at a faster rate. Such rapid heating of bimetal section 68 causes it to defiect substantially immediately which defiection increases the contact pressure between contacts '58 and 72 substantially immediately. The increased contact pressure is further increased due to the length of bimetal section 70 which comprses a relatively long lever arm. Due to the relatively low resistivity of the bimetallic material forming bimetal section 70, bimetal section 70 is substantially unafiected by current flow therethrough. When

contacts

58 and 72 are broken

bimetal sections

68 and 70 have an action which is the reverse of that just described.

As current passes through the bimetal element 54, it becomes heated and in order to accomplish the purpose of our invention, it is arranged so that upon heating the bimetal element 54 moves toward the side wall 8 and

contacts

58 and 72 separate and the line current passing therethrough is interrupted providing suflicient thermal stress is developed in bimetal 54 to overcome the mechancal resistance of bimetal 60. Such interruption of the line current will permit both bimetal element 64 and

bimetal sections

68 and 70 to cool, ho-wever, as bimetal section 68 is of such reduced cross section and was ata relatively high temperature it will cool at a more rapid rate and move rapidly away from bimetal element 54 so as to return to its initial normal position as indicated above. As the free end of cam follower 76 thus no longer engages projection 90 it no longer exerts any positive force causing bimetal element 54 to remain in the open circuit position so that the cooling of bimetal element 54 will cause its return to the circuit establishing position. As bimetal element 54 is of a heavier section than bimetal 68, upon cooling it will defiect at a slower rate so that the circuit therethrough will not be established for an increment of time due to the differences in the defleetion rates of the bimetal section 68 and bimetal element 54, and to the absolute cooling rate of bimetal element 54. In order to increase this time increment, a heat control insulation 104 may be Secured to bimetal element 54 in any suitable manner, such as by being wrapped therearound and Secured so as to extend between the contact 58 and terminal 56 whereby the heat dissipation of bimetal element 54 will be retarded and consequently retard its deflection upon cooling. Insulation 104 may-be formed from any suitable heat insulating material depending upon the heat characteristics desired and for such purposes a spun or woven glass insulating material has been found to be Satisfactory. It has also been found to be desirable to form insulation 104 with a series of spaced holes 39 (Figs. 1 and 2) over each side edge of bimetal 54 so as to provide stress relief in insulation 104. Such holes do not aifect to any substantial degree the rate of heat dissipation from bimetal element 54 as the exposed area of bimetal element 54 is kept to a minimum. By providing holes 39, as indicated, the fiexing of insulation 104 does not induce any substantial stresses therein which would restrict movement of bimetal element 54. Upon reestablishing of the circuit the above-described heating efect will occur again whereby the circuit cycle is repeated. Thus, it will be noted that the passage of current is continuously interrupted by the movement of bimetal element 54 which, when connected to a range heating element, such as shown in Fig. 5, will alternately connect and disconnect cyclically the load H from the supply conductors Ll and L2.

It will be particularly noted that the passage of current for each increment of

time contacts

56 and 72 are engaged will be determined by the time necessary for the bimetal element 54 to produce a thermal force, resulting from its heating, which is sufficient to overcome the mechanically applied

force holding contacts

58 and 72 together.

Although the thermal characteristics of the

bimetal elements

66 and 54, as described above, control the electrical energization of heater H, such thermal characteristics alone are not suficient to obtain the desired operating characteristics of our switch. Of equal importance in the operation of our switch are the mechanical stresses and cancellation of stresses which are developed in the various members. Also of great importance in our switch is the-fact that mechanical stress and thermal deflecton of a bimetal member are mutually related. Thus, as indicated, movement of cam portion 94 counterclockwise as viewed in Pig. 2 causes the bimetal element 60 to be moved toward side wall 9 which, due to the fact that bimetal element 60 is connected at opposite ends to cam follower 76 and cross link 62, respectively, causes contact closing movement ot' bimetal element 54 and consequently stress to be developed in bimetal element 54. With our system, the mechanical stress developed in bimetal 54 in moving from an unstressed position to the position where

contacts

58 and 72 engage is equal to the mechanical stress developed in the bimetal elenent 60 due to the movement of cam follower 76 through screw 95, caused by cam portion 94. Inasmuch as such initial mechanical stresses in the opposed

bimetal elements

60 and 54 are equal, movement of

bimetal element

60 and 54 sufricient to just engage

contacts

58 and 72 Wlll provide an initial stable reference position so that the switch may be accurately calibrated. Further as

bimetal elements

60 and 54 have the same thermal characteristics and are disposed so as to oppose each other, such initial stable position is obtained without regard to the ambient temperature.

In order to provide an initial heating cycle for the heater H, the screw 95 is then turned so as to force the cam follower 76 further toward side wall 9 so that a further mechanical stress is developed in bimetal element 60 which in turn causes a further mechancal stress, to be developed in bimetal element 54 to force the contact 58 into firmer engagement with contact 72. The amount of such increased contact pressure will determine the amount of thermal force which must be created in bimetal element 54 to cause the

contacts

58 and 72 to separate and thus establish the desired calibration of the switch. It will also be noted that the bimetal section 70 is located adjacent to a stop 37 formed integral 'aerdaeo 11 with housing 2 so that bimetal element 66 can be forced only a small distance toward side wall 9. By this Construction bimetal section 68 is prevented from being overstressed by the engagement of Contacts and '72. 'hus it will be noted that the initial setting of the switch has been obtained by the simple mechanical expedient of turning screw 95.

The initial setting of the switch having been determined, it is to be noted that further counterclockwise rotation of the cam portion 94- is designed to force the cam follower 76 further toward side wall 9. Thus, as has prcviously been described, an increase in thermal force must be created in bimetal element 54 to cause the

contacts

58 and 72 to separate. The aforesaid rotation causes the bimetal element se to exert a force upon binetal element 54- and its contact 58 through cross link 62. As the bimetal element 60 is resilient, the force exerted on bimetal element is proportional to the amount of stress created in 'rimetal element se by the cam setting. Initial stressing of bimetal element ea causes the

Contacts

53 and 72 to close and since such stressing of bimetal element 6@ may 'ne infinitely varied over a fairly wide range, the range of pressures between Contacts 5 and 72 may be substantially infinitely varied within the physical limitations or" the switch. Accordingly, cam portion 9-5 of cam 26 is designed to gradually increase the displacement of cam follower 76 and bimetal element dt) toward side wall 9 by the aforesaid countercloclvise movement of cam 26. Such deflection of cam follower '76 will also increase the deilection of its free end away from the projection 9@ on the cross link 62, so that the Cycling movement oi' cross link 62 will not he interrupted by engagement with the` free end of cam follower '76.

In operation, the current flowing through the heater will be limited to the time the Contacts 58 and are engaged. Thus, the dellection of cam *follower which is just sntiicient to cause Contacts 5% and to close after calibration will require the minimum force to be produced in the bimetal element 54 to cause the Contacts 53 and 7?. to disengage. Accordingly, himetal element 54 need only be heated by the current passing therethrough for a period of time which is considerably shorter than the period of time which would be required if a greater holding force were exerted upon the

Contacts

53 and 72. Under these circumstances, the temperature of bimetal element 54 will only be elevated a minimum amount above its ambient temperature before separation of

Contacts

53 and 72 occurs. in View of such a low temperature gradient between the bimetal element 54 and the ambient temperature of the switch, a t'airly long cooling period will be required to reduce the temperature of himetal element to its ambient temperature, as Compared to its heattirne. Thus, the

Contacts

53 and 72 will be open for a longer period of time than they Will be closed. As himetal element 61? is deflected further toward the side wall by the cam 26, the force necessary to open Contacts 58 and '72, will become progressively greater and the temperature necessary for operation of bimetal element will increase. As the required Operating temperature of the bimetal element 54 increases, its cooling rate also increases due to the larger dierential between the temperature the bimetal element 54 attans and the ambient temperature so that the ratio of cooling to heating time decreases.

'translated int terms of heat dissipation, the electrical heating unit H heats when current is fiowing and cools when the current oti, in an identical manner to the hirnctal element as it is connected in series with himetal 5 5. Thus, for low temperatures of heating element corresponding to small displacement of the bimetal element by the cam the heating time 'of heating element H is relatively short and the cooling time is relatively long so that the wattage dissipation readily be made thereto externally of the housing 2'.

per unit of time bytheheating element H is thus relatively low. When the shaft 3@ is positioned at a high heat position, the energi ed time of the heating unit H is relatively long and the cooling time relatively short so that the wattage dissipation by the heating unit H per unit of time is thus relatively high. lnasmuch as the cam may be freely rotated to a variety of positions between oil and a desired highest wattage dissipation, the hoat output of the heating unit may be innitely varied between such limits. If desired in order to obtain denite steps within the range of the switch, the upper portion of cam portion 94 may be provided with a number of spaced radally outwardly extending slots 186 for receivng the free end of a spring 103 Secured to cover 36 in any suitable manner. By this Construction the spring 108 will, when it enters one of the slots 1%, create a definite feel" as to the position of the cam 26.

Another embodment of our invention is shown in Figs. 4 and 5 which conprises a rectangular one-piece cup-shaped housing 2' having longitudinally extendirg laterally spaced side walls 8' and 'J' which are connected at their ends by means of laterally extending end walls 12', and has a base 13'. l-Iousing 2' may be formed from any suitable insulating material, and is preferably formed from a molded plastic material which may readily be formed as hereinafter described. As shown, a pair of laterally spaced terminals 4' and 6' are located inwardly adjacent one end wall 12' of housing 2' and a terminal 10' is located inwardly adjacent the opposite end wall 12. Terminals i', 6' and lil' may be made 'from any suitable electrical conducting material, such as an alloy of Copper, and are each provided with integral Connector engaging portions which extend through a slot through base 13' (not shown) and outwardly from the outer side of base 13' so that wiring connections may It will .be noted that the inwardly extending portion of terminal it) extends laterally between side walls 8' and 9' and that terminals i' and 6' are spaced laterally on opposite sides of` the longitudinal center line of housing 2' with terminal 4' being oflset toward side wall 9' of housing 2' and terminal e' being ofiset toward sidc wall 8'.

Terminals 4' and 6' are each electrically connected to terminal lil' by means of brushes 14' nd 3.6', respectively, which extend longitudina ly above the inner surface of base 13'. One end of each brush M' and 16' is provided with a suitable opening (not shown) therein 'for receiving the inwardly extending end portions of terminals 4' and e', respectivel so that brushes 14' and 16' may be electrically and mechanically Secured thereto in any suitable manner such as by ..sans of deforming integral `tabs on terminals i' and e' into engagement with the upper surfaces of brushes and 15'. Brushes M' and 16' are sufliciently resilient to normally bias the opposite free ends of brushes and 16' out of engagement with terminal l The free end of brush 1.6' is provided with an integral laterally extending contact 15 which extends toward terminal 'ti' for engaging the upper surface of terminal 1%'. Referring to Fig. 7, it will be noted that brush 16' is utilized to control a pilot light P, and accordingly, it does not Carry any substantial amount of current so that. such direct engagement with terminal 3.4) is satisfactory. Brush 3.4' is, hov/ever, a line current-carrying member, and in order to mnimize arcing damage when brush -i' engagcs the upper surface of terminal 10', the opposed surfaces of terminal lil' and brush 34' are provided with arc rcsistant contacts 17' and 13 respectively, which may be formcd from any suitable arc resistant material, such as silver or an alloy ther-cof. Contacts 19' and 17' may be Secured .to the brush 14' and terminal to', respectively, in any suitablemanncr such as by being riveted .thereto. Terminals 4', 6' and 10' may be Secured to base 13' in (not shown) on the outwardly extending portions into engagement with the outer surface of base 13'.

Brushes 14' and 16' are operated by means of a formed cam 26' which is rotatably supported within the housing 2' and is forrned of any suitable insulating material, such as a moided plastic material which may readily be provided with the necessary structure as hereinafter described. As shown, cam 26' is provided with a central axially extending circular opening 28' to which one end of an elongated Operating shaft 30' is suitably secured.

The entire open side of housing 2' is enclosed by means of a cover 36', which may be formed of any suitable material, such as steel, and which is secured to the open side of housing 2' in any suitable manner such as by means of projections at the sdes thereof (not shown) which are deformable to engage cam surfaces 125 on the ends 12' of the housing 2'. Cover 36' is provided with an approximately central opening through which the Operating shaft 30' extends so that the switch may be operated externally of housing 2'.

The inner surface of cam 26' facing the base 13' is provided with a pair of laterally spaced recesses 214 for receiving the projecting portions 212 of brushes 14' and 16'` therein When cam plate 26' is at the o position. Recesses 214 are formed so that rotation of cam 26' in each direction causes projections 212 to ride out of the recesses 214 and engage the innermost surface of cam .26' so that brushes 4' and 6' are forced into engagement with terminal As shown, an elongated generally longitudinally extending bimetal element 54' is located inwardly adjacent side wall 8' with one end being secured to a terminal 56'. Terminal 56' is secured to base 13' in a similar manner to terminal 10' so that the inner portion extends upwardly from base 13'. Binetal element 54' may be formed from any suitable pair of dissimilar materials having different coefficients of thermal expansion, such as are generally available. One end of bimetal element 54' 'is fixedly secured to the inner portion of terminal 56' in any suitable manner such as by being spot welded thereto. A contact 58' similar to the contacts 17' and 19', previously described, is secured to the opposite movable end of bimetal 54' in any suitable manner, such as by being riveted thereto.

An elongated longitudinally extending bimetal element 60', which is substantially identical to the bimetal element 54', is located inwardly adjacent side wall 9' so that it extends generally longitudinally of sidewall 9'. As shown, the end of bimetal element 60' adjacent terminal 56' is pivotally secured to the housing 2', and the opposite movable end of bimetal element 60' is laterally spaced from the movable end of bimetal element 54'. A cross link 62' of any suitable 'materiaL such as thin spring steel, extends laterally between the movable ends of bimetal elements 54' and 60' and is located between the terminals 4' and 6' and the adjacent end wall 12'. Cross link 62' is permanently secured to both bimetal 54' and 60' in any suitable manner, such as previously indicated herein with reference to Figs. 1-3. Thus, movement of either bimetal element 54' or 60' in either direction causes a correspondng movement in the' opposite bimetal element 54' or 60' due to the cross connection of cross link 62'. Cross link 62' is provided intermediate its ends with an inwardly bent portion 216 which is opposed to V-shaped notch 218 in the inner surface of end wall 12' adjacent thereto. `A thin toggle link 222 of any suitable material, such as steel, extends between notches 216 and 128 to in effect form' an overcenter toggle so as to cause a rapid movement-of cross link 62' once link 62' has been initially i 14 previously described. Terininal 64' is located between the terminal 56' and the adjacent end wall 12' adjacent side wall 8'. As shown, an electrical heating element 224 extends longitudinally adjacent bimetal element 54' and one of its ends is secured to the inwardly extending portion of terminal 64' in any suitable manner, such as by being welded thereto. Heater element 224 may be formed of any suitable electrical resistance material, such as a steel alloy wire formed in an elongated helical coil. As shown, a generally U-shaped terminal 226 is secured to base 13' by any suitable means, not shown, engaging its bight portion, so that its arms extend upwardly from base 13' on opposite sides'of the movable end of bimetal 54'. The arm of terminal 226 adjacent side wall 8' extends adjacent the other end of the heater 224 so that the heater 224 may be electrically and mechanically secured thereto 'in any suitable manner, such as by being welded thereto. The other arm of terminal 226 is provided with a suitable contact 72', similar to the

contacts

19 and 17 previously described, which is located so as to be cooperable with contact 58' on bimetal 54'. Thus, it will be noted that this Construction is similar to the Construction previously described in that a pair of opposed bmetals 54' and 60' are provided which have laterally spaced ends connected by means of a cross link 62'. As before, bimetal elements 54' and 60' are disposed in opposite rela tionship to each other and arranged to deflect in opposite directions in response to any given temperature change so that the ambient temperature effect thereupon will be nullified as previously described. In this modification of our invention the bimetals 54' and 60' engage the cross link 62' so as to 'force the ends of cross link 62' toward end wall 12' adjacent thereto to produce a stress on the toggle link 222. By so providing a Stress on toggle link 222, the cross link 62' produces a rapid movement of the contacts between the o and on positions, thus minimizing arcing between Contacts 58' and 72'. It will also be noted that

notches

216 and 218 are V-shaped so as to provide knife edge bearings at the ends of toggle link 222 whereby friction between the parts is minimized' The pivot support for bimetal element 60' may be of any suitable Construction and, as shown, comprises a generally U-shaped support 228 having one of its arms pivotally secured to base 13' inany suitable manner, not shown. The end :of bimetal element 60' adjacent support 228 is bent inwardly of housing 2' into engagement with the bight portion of support 228 so that it may be secured thereto in any suitable manner, not shown, such as by being welded thereto. Support 228 is also provided with an integral arm 230 which extends outwardly from the side of the bight portion of support 228 opposte that from which the bimetal element 60' extends. As shown, a set screw 232 is threaded 'in arm 230 adjacent the bight portion of support 228'so as to extend therethrough with one of its ends engaging the inner surface of bimetal element 60' adjacent the bight portion of support 228. Arn 230 extends generally longitudinally inwardly of housing 2' adjacent bimetal element 60' with its free end being located in engagement with the outer side surface 234 of cam 26'. In order that arm 230 of support 228 may be activated by cam 26', as hereinafter'described, support 228 is fo'med from any suitable resilient material having suicient structural strength, such as an alloy of steel or Copper. If desired, however, arm 230 may be formed as a separate piece and secured to support 228 in any suitable manner. V

In order to provide an innite control switch, the side surface 234 of cam 26' is formed with a smooth curvature of increasing radus which forces arm 230 further toward the side wall 9' upon clockwise rotation of cam plate 26' with reference to Fg. 4. The switch, as shown in Fig. 4 is in the bit position with the free end of arm 230 being located in a notch 236 which extends inwardly from the side surface 234 of cam 26'. When arm 230 is located in notch 236, it is in its maximum inward travel 15 position, and the bimetal elementtl'is alsomoved toward the side wall 8' by cross link 62', due to the initial bias of bimetal element 54' toward the side wall 8. Such movement of bimetalelementS-' towards side wall 8' causes Contacts 72' and 58' to be separated. In order, however, that the movement of bimetal element 54' towards side wall 8' may be limited, an integral inwardly extending projection 233 is provided on the side wall 3' which engages the free end of cross link 62' adjacent bimetal element 54'. As before, a positive off position is provided by providing the cam 26' with an outwardly extending projection 241 which engages the inner surface of bimetal element 54' so as to prevent any movement of contact 58' into engagement with contact 72'. When cam 26' is in the oil position, projections 212 on brushes l i and 16' are located in recesses 214- so that brushes 14' and 16' are electrically separated from terminal 10'.

-Rotation of cam 26' in eitherdirection causes the brushes 14' and 16' to be forced into engagement with terminal At the same time, projection 241 moves away from the inner surface of bimetal element 54' so that bimetal element 54' is free to cycle in the same manncr as previously described for bimetal element 54. When cam 26' is so moved clockwise, arm 230 is forced outwardly of notch 236, which movement causes the pivot support 228 to rotate c ounterclockwise (Fig. 4) and, in turn, causes the bimetal element 60' to move toward the side wall 9'. As projection 241 no longer engages bimetal element 54', such movement of bimetal se' causes the toggle link 222 to move overcenter toward side wall 9' so that bimetal element 54' is moved rapidiy toward side wall S and the contact 58' rapidly engages the contact 72'. By connecting terminals 56', 6' and 4' to the conductors Ll, N andLZ, respectively, and terminals 64' and 1 to

conductors

121 and 12%, respectively, as previousiy described, the closing of contacts 58' and 72' will cause an electrical current to flow froni the cenductor Li through the terminal 56', bimetal element 54', engaged Contacts 58' and 72', terminal 226, heater 224, terminal 64', conductor 121, heating element H, conductor 129 to terminal 10', at which time the current is thereafter divided through two circuits, one of which comprises the engaged contacts 17' and 19', brush 14', terminal d' to conductor L2, and the other of which comprises brush 16', terminal 6', pilot light P to conductor N. Inasmuch as the circuit includes the series connected bimetal element 54' and adjacent heater 224, the bimetal element 54' will become heatcd so as to cause movement there-of. By forming bimetal element 54' so that when heated it moves tow rds the side wall 8', such heating will cause the Contacts 53' and 72' to be separated. Such sepa'ation of Contacts 53' and 72' will disconnect the heater 22@ from the supply line so that bimetal element 5 3' Will cool. Upon cooling, bimetal element 54' will move towards the side Wall 9' to repeat this cycle. It is believed obvious that the operation of this embodiment will be substantially identical to that previously described, in that the thermal defiection of bimetal 54' overcomes the Stress mechancally produced in the bimetal 60', and, accordingly, need not be repeated.

lt will be noted, however, that in order to prevent projections 212 from entering recesses 214 when cam 26' has been rotated 180 that projeetions 212 are offset from the center of cam plate 26' different radial distances. in a similar manner, it. will be noted that operation of the switch to open contacts 53' and 72' does not occur until the Stress created by the temperature rise of the actuating bimetal element 54' becomes equal to the stress in the bimetal element 69' plus an amount sufiicient to move the toggle link 222 overcenter.

It will be noted that the Operating principle of a device constructed in accordance with the principle of our invention is unique in that a mechanical force is opposed by a thermal for-ce and that the thermal force must .be suificient to cyclically overcome the mechanical force. By

16 va'ying the mechanical force the overcoming thermal force is also varied. Of particular note is the fact that the mechanical and thermal forces in opposed members are balanced at room temperature so that the switch may be easily calibrated at room temperature. Further, it will be noted that the friction forces in our device arc at a minimum due to a unique loading of all the operating members of the device. ln particular, the opposing force is achieved by a bimetal element which is mechanically stressed so as to determine the therrnal force required for movement by an identical actuating bimetal element. Due to the inverted position of the two bimetal elements, ambient temperature compensation is automatically achieved without adjustment, and the only adjustment required is the initiar setting of one point on the Operating curve through the adjustment of the original opposing force of the compensating bimetal element by means of the adjusting screw. This feature of balaneing forces rather than defiections decreases the required space of the mechanism, increases the accuracy of calibration, and simplifies the contact problem in that in etfect a stationary, rather than a movable mating contact forthe actuating bimetal, is provided.

i Having described preferred embodiments of our invention in accordance with the patent statutes, it is desired to point out that they are merely illustrative of the invention and cannot be properly considered as lmiting the invention to the specific details thereot. it is obvious that various changes may be made without departing from the true spirit and scope of our invention. Accordingly, it is desired that the invention "oe interpreted as broadly as possible and that it be limited only as required by the prior art.

We claim as our invention:

l. A Wiring device comprising, an insulating support, an elongated thermal bimetal element having one of its ends rigidly secured to said support so that its other end is movable with respect thereto, a contact mounted on said support and located adjacent the other end of said bimetal element, an elongated resilient member having one end mechanically connected to said bimetal element at a point spaced from said one end to be movable therewith, said resilient member located in a plane approximately parallel to said bimetal element, said resilient member having its other end supported by said support to permit pivotable movement thereor" generally laterally of said bimetal element, mechanieal means movably mounted on said support for actuating said resilient portion to move said other end of said bimetal element into engagement with sai-d contact, and movable a further amount to Stress said resilient portion selected amounts to bias said bimetal element into engagement With said contact with various contaeting pressures, said bimetal element and said contact being located in an electrical cireuit which is adapted to be connected to a source of electrical energy so that a current flows therethrough in response to which said bimetal element becomes heated, and said bimetal element being constructed to move away from said contact when heated an amount sufficient to overcome the bias of said resilient portion so that said eircuit is interrupted and said bimetal element cools.

2. A wiring device comprising, an insulating support,

an elongated thermal bimetal element having one of itsends rigidly Secured to said support so that its other end is movable With respect thereto, a contact mounted on said support and located adjacent said bimetal element in spaced relationship with the fixed end thereof, a movable element connected to said bimetal element to extend generally laterally therefrom, another thermal elongated bimetal element extending in a plane approximately parallel to said first-mentioned bimetal element having one of its ends Secured to said movable element and its other end supported by said support to permit pivotable movement thereof generally laterally of said bimetal element, mechanical means movably mounted on said support engageable withsaid lastmentioned bimetal element to .move said other end of sidfirst-mentoned bimetal element into engagement with said contact, said firstmentioned bimetal element and said contact being located in an electrical circuit which is adapted to be con nected to a source of electrical energy so that a current flows therethrough in response to which said first-mentioned bimetal element becomes heated, and said firstmentiored bimetal element being constructed to move away from said contact when heated so that said circuit is interrupted and said bimetal element eools, each of said bimetal elements being substantially of the same size and material and located so that their thermal delections are opposed from each other 3. A wiring device comprising, an insulating support, an elongated resilient thermal bimetal element having one of its ends rigidly Secured to said support so that its other end is movable with respect thereto, a contact mounted on said support and located adjacent said bimetal element in spaced relationship with the fixed end thereof, a movable element connected to said bimetal ele- .ment and having a resilient portion, mechanical movably mounted on said support and having a portion thereof for actuating said resilient portion and which is formed to selectively apply various pressures on said resilient portion in a direction to cause said bimetal ele .ment to engage said contact with correspondingly various contact pressures, said bimetal element and said contact being located in an electrical circuit which is adapted to be connected to a source of electrical energy so that a current flows therethrough in response to which said himetal element becomes heated, and said bimetal element being constructed to move away from said contact when heated so that said circuit is interrupted and said bimetal element cools.

4. A wiring device comprising, an insulating support. an elongated thermal bimetal element having one of its ends rigidly secured to said support so that its other end is movable with respect thereto, a contact mounted on said support and located adjacent said bimetal element in spaced relationship with the fixed end thereof, a mova- 'ble element connected to said bimetal element to extend generally laterally therefrom, said movable element having a resilent portion eXtendng therefrom in a plane approximately parallel to said bimetal element, mechanical .means movably mounted on said support for actuating said resilient portion to move said other end of said bimetal element into engagement with said contact, said bimetal element and said contact being located in an electrical circuit which is adapted to be connected to a source of electrical energy so that a current fiows therethrough in response to which said bimetal element becomes heated, said` bimetal element being constructed to .move away from said contact when heated so that said circuit is interrupted and` said bimetal element cools, and stop means on said movable element located to bo engaged by means movable in response to movement of said mechanical means for positively holding said blmetal element out of engagement with said contact when said mechanical means is in one given position.

5. A wiring device comprising, an insulating support, an elongatecl resiiient thermal bimetal element having one of its ends rigidly Secured to said support so that its other end is movable with respect thereto, a contact mounted on` said Support and located adjacent said blmctal'elenent in spaced relationship with the fixed end thereof, a mechanical linkage movably mounted on said support and connected to said bimetal element including a resilient member, means for normally biasing said linkage 'and 'said bimetal element out of engagement with said contachmanuall operabl'e means movably mounted on said support and engageable with said linlrage for movingit and saidbimetal element into engagement With said, contact with any one of an innite number of contaci; pressures, said bimetal element said' contact nema-oo being located in an electrical circuit which is adapted to be connected to a source of electrical energy so that a current ows therethrough response to which said bimetal element becomes heatecl, and said bimetal element being constructed to move away from said contact when heated so that said circuit is interrupted and said bimetal element cools.

6. A Wiring device comprising, an insulating support, an elongated thermal bimetal element having one of its ends rigdly secured to said support so that its other end is r" ?able with respect thereto, a contact mounted on said support and located adjacent said bimetal element in spaced relationship with the fixed end thereof, a movable element connected to said bimetal element to extend generally laterally therefrom, said movable element having a resilient portion extending therefrom in a plane approximately parallel to said bimetal element, resilient means mounted on said support and engaging said movable element to normally bias said bimetal 'element away from said contact, manually. operable means movably mounted on said support and engageable with said resilient portion for moving it and said bimetal elelent into engagement with said contact with any one of an innite number of contact pressures, said bimetal element and said contact being located in an electrical circuit which is adapted to be connected to a source of electrical energy so that a current fiows therethrough in response to which said bimetal element becomes heated, and said bimetal element being constructed to move away from said contact when heated so that said circuit is interrupted and said bimetal element cools.

7. A wiring device comprising, an insulating support, an elongated bimetal element having one of its ends rigidly Secured to said support, an elongated resilient mechanical link having one of its ends pivotally se: rcd to said support, said bimetal element and said mechanical lini; having their free ends spaced from each other, a cross link Secured to said bimetal element and said mechanical link so as to extend transversely therebetwee at a point spaced from each of the Secured ends thcrcof, a movable'contact secured to said bimetal element so as to be movable therewith,.a contact mounted on said support so as to be cooperable with said novable contact, mechanical means engageable with said mechanical link to cause movement of thefree ends of said bimetal element and said mechancal link in one lateral direction, and movable a further amount to stress said reslient portion selected amounts to bias said bimetal element into engagement with said contact with various contacting pressures, said movable and fixed contacts being located so as to engage each other upon such movement in one direction, and said bimetal element being conructed to move when heated an amount sufficient to overcome the bias of said resilient portion in a direction opposite said one direction so that said Contacts are s i arated.

8. A Wiring device comprising, an insulating support. a first resilent elongated bimetal element having one of its ends rigidly Secured to said support, a second resilient elongated bimetal element having one of its ends pivotally sec red to said support, said first and second bimetal elements having their free ends spaced from each other, a cross link Secured to said bimetal elements so as to extend transversely therebetween at a point spaced from the Secured ends of said bimetals, a movable contact Secured to said first bimetal element so as to be movablc therewith, another contact mounted on said support so as to be cooperable with said movable contact, mechanical means movable to cause movement of the free end of said second bimetal element away from the free end of said first bimetal element, said cross link being secured to said bimetal elements so that such movement of said second bimetal element causes said first bimetal element to move in the same general direction as said second bimetal element to cause said movable contact to engage said other contact, said first bimetal element being constructed to move when heated in a direction opposite to the above described movement whereby said contacts are separated, and said bimetal elements being constructed so as to move in opposite directions in response to temperature changes.

9. A Wiring device comprising, an insulating support, an elongated bimetal element having one of its ends rigidly secured to said support, an elongated mechanical link having one of its ends pivotally secured to said support, said bimetal element and said mechanical lini; having their free ends spaced from each other, a cross link secured to said bimetal element and said mechanical link so as to extend transversely therebetween at a point spaced from the secured ends thereof, a toggle link pivotally supported at its ends by said support and said cross link, respectively, to cause said cross link to move rapidly in either longitudinal direction after initial movement thereof in either direction, a movable contact secured to said bimetal element so as to be movable therewith, a fixed contact mounted on said support so as to be cooperable With said mot able contact, mechanical means engageable with said mechanical link to cause movement of the free ends of said bimetal element and said mechanical link in one lateral direction, said movable and fixed contacts being located so as to engage each other upon such movement in one direction, and heater means connected to be energized upon closing of said contacts to cause said bimetal element to move in a direction opposite said one direction so that said contacts are separated.

10. A wiring device comprising, an insulating support, an elongated bimetal element having one of its ends rigidly secured to said support, an elongated mechanical link having one of its ends pivotally secured to said support, said bimetal element and said mechanical link having their free ends spaced from each other, a cross link secured to said bimetal element and said mechanical link so as to extend transversely therebetween at a point spaced from each of the secured ends thereof, a movable contact secured to said bimetal element so as to be movable therewith, a fixed contact mounted on said support so as to be cooperable with said movable contact, mechanical means movably mounted on said support and having a cam surface thereon engageable with said mechanical link to cause movement of the free ends of said bimetal element and said mechanical link in one lateral direction, said cam surface being formed to obtain a plurality of different lateral movements, said movable and fixed contacts being located so as to engage each other upon such movement in one direction, and heater means connected to be energized upon closing of said contacts to cause said bimetal element to move in a direction opposite said one direction so that said contacts are separatcd.

11. An electric switch comprising, separable load contacts at least one of which is movable to open and close a circuit, thermal means responsive to current fiow through said contacts for separatng said contacts and for automatically reclosing them thereafter, manually operable means selectively movable to any position between predetermined limits, resilient thermal means interposed between said manually operable means and said thermal means to exert a varying force on said thermal means in a contact closing direction to vary the response of said current responsive means dependent upon the position of said manually operable means, whereby said contacts may be selectively cycled to remain open and closed for different times, and said resilient thermal means being responsive to temperature changes to move said contacts in an opposite sense to the rst-mentioned thermal means and being independent of current flow through the contacts.

12. An electric switch comprising, separable contacts one of which is normally movable to open and close a circuit, the other of said contacts being mounted on thermal current sensitive means operable in response to current flow through said contacts to bias said contacts e, U a

26 into engagement and being responsive to cessation of current flow through said contacts to increase separation of said contacts, and additional thermal means relatively insensitive to current flow to compensate for ambient temperature effects on said thermal current sensitive means.

13. A wiring device comprising, an insulating support, an elongated thermal bimetal element having one of its ends rigidly secured to said support so that its other is mo /able with respect thereto, a contact mounted on said snpport and located adjacent the other end of said bimetal element, means mechanically engaging said bimetal element at a point spaced from said one end, said means having a resilient portion, means biasing said first mcntioned means in a direction to separate the other end of said bimetal element from said contact, mechanical means movably mounted on said support for actuating said resilcnt portion in a direction to move said other end of said bimetal element into engagement with said contact, said bimetal element and said contact being adaptcd to be located in an electrical circuit which is adapted to be connected to a source of electrical energy so that a current fiows theretlrough when said bimetal engages said contact in response to which said bimetal element becomes heated, and said bimetal element being constructed to nove away from said contact when heated so that said circuit is interrupted Whereupon said bimetal element cools.

14. A wiring device comprising, an insulating support, an elongated thermal bimetal element having one of its ends rigidly secured to said support so that its other end is movable with respect thereto, a contact mounted on said support and located adjacent the other end of said bimetal element, means mechanically engaging said bimetal element at a point spaced from said one end, said means having a resilient portion and a rigid operating portion, means acting on said rigid portion for biasing said first mentiored means in a direction to separate the other end of said bimetal element from said contact, mechanical means movably mounted on said support for actuating said resilient portion in a direction to move said other end of said bimetal element into engagement with said contact, said bimetal element and said contact being adapted to be located in an electrical circuit which is adapted to be connected to a source of electrical energy so that a current fiows therethrough When said bimetal engages said contact in response to which said bimetal element becomes heated, said bimetal element being constructed to move away from said contact when heated so that said circuit is interrupted whereupon said bimetal element cools, and said rigid Operating portion having a part mechanically bypassing said resilient portion and located to directly engage a part mov able with said bimetal element to move the latter away from said contact when said mechanical means is not adjusted to cause engagement of said bimetal element and contact.

15. An electric switch comprising, separable load contacts at least one of which is movable to open and close the circuit, thermal means responsive to current fiow through said contacts for separating said contacts and for automatically reclosing them thereafter, manually operable means selectively mor 'able to any position between predetermined limits, resilient means interposed between said manually operable means and said thermal means to exert a varyng force on said thermal means in a contact closing direction to vary the response of said current responeive means depeudent upon the position of said manually operable means, Whereby said contacts may be selectively cycled to remain open and closed for different times, and spring means biasing said resilient means in a contact opening direction.

16. An electric switch comprising, separable load contacts at least one of which is movable to open and close the circuit, thermal means responsive to current flow 21 through said contacts for separating said contacts and for automatically reclosing them thereafter, manually operable means selectively movable to any position between predetermined limits, a movably mounted rigid Operating member actuated by said manually operable member, resilient means inteposed between said operating member and said thermal means to eXert a varying force on said thermal means in a contact closing direction to vary the response of said current responsive means dependent upon the position of said manually operable means, whereby said Contacts may be selectively cycled to remain open and closed for difierent times, and resilient means biasing said Operating member in a contact opening direction.

17. An electric switch comprising, separable load contacts at least one of which is movable to open and close the circuit, thermal means responsive to current flow through said contacts for separating said contacts and for automatically reclosing them thereafter, manually operable means selectively movable to any position between predetermined limits, a movably mounted rigid Operating member actuated by said manually operable member, resilient means interposed between said operating member and said thermal means to exert a varying forc-e on said thermal means in a contact closing direction to vary the response of said current responsive means dependent upon the position of said manually operable means, whereby said contacts may be selectively cycled to remain open and closed for different times, means hiasing said Operating member in a contact opening direction, and said Operating member having a part mechanically bypassing said resilient means so that said biasing means can directly maintain said contacts separated When said manually operable means is adjusted to a position where it does not exert any substantal contact-closing force.

18. An electric switch comprising, separable contacts one of which is normally movable to open and close the circuit, thermal current responsive means for moving said one contact to open the crcuit in response to currents 22 above a predetermined value and to close the circuit in response to cessation of current flow, the other of said contacts also being movable to open and close the circuit, thermal current responsive means which is more sensitive than the first-mentioned current responsive means and operable in response to current flow through said contacts to bias said Contacts into engagement and being responsive to cessation of current flow through said contacts to increase separation of said Contacts, and additional thermal means relatively insensitive to current flow to compensate for ambient temperature effects on said thermal current sensitive means.

19. An electric switch comprisng, separable contacts mounted on individual bimetal elements which are heated in response to current flow through the contacts, one of said bmetal elements comprising serially connected bimetailic parts arranged to deflect in opposite directions when heated to compensate so that no net deflection normally occurs in response to temperature changes, the bimetallic part which deflects in a direction to close said Contacts upon a rise in temperature being faster actng than both the other bimetallic part and the other bimetal element so as to efect rapid application of contact pressure during closing of said Contacts and to enhance separation of said Contacts during opening thereof.

References Cited in the file of this patent UNITED STATES PATENTS l,7l6,04l Goergl June 4, 1929 1,749,7 18 Randolph Mar. 4, 1930 l,9l6,671 Hanser July 4, 1933 2,l31,640 Sachs Sept. 27, 1938 2,338,474 Wilson Jan. 4, 1944 2,427,94S Clark et al. Sept. 23, 1947 2,498,127 Kuhn Feb. 21, 1950 2,520,874 Bean Aug. 29, 1950 2,5S5,068 Wood Feb. 12, 1952 2,593,268 Clark Apr. 15, 1952 2,623,l37 Vogelsberg Dec. 23, 1952 2,685,636 Vogelsberg Aug. 3, 1954