US3393389A - Adjustable bridging contact member type thermostatic switch - Google Patents

Description

July 16, 1968 R. e. MAWNEY ETAL 3,393,339

ADJUSTABLE BRIDGING CONTACT MEMBER TYPE THERMOSTATIC SWITCH Original Filed June 6. 1960 5 Sheets-Sheet 1 a F Inventors.- wa I": :1 Robert GZMawm y,

32 E} C 34 fi0berA.Renaud, f Low: 6'. flqyys, ,8 F10? E A ti'y.

July 16, 1968 R. G. MAWNEY ETAL 3,393,389

ADJUSTABLE BRIDGING CONTACT MEMBER TYPE THERMOSTATIC SWITCH Original Filed June 6. 1960 5 Sheets-Sheet z -|-7 [n mentors: RoZert 6T Mall/rag, RoZert A. Renaud, Louis 6'. 583170,

July 16, 1968 R. G. MAWNEY ETAL ADJUSTABLE BRIDGING CONTACT MEMBER TYPE THERMOSTATIC SWITCH 5 She ets-Sheet 4 Original Filed June 6, 1960 Inventors.- Bohr! G. Malone RoZert A. Renaud, Loans C. Be

if" v QZ July 16, 1968 ADJUSTABLE BRIDGING CONTACT MEMBER TYPE THERMOSTATIC SWITCH Original Filed June 6. 1960 5 Sheets-Sheet 5 I K /62 L 40 I L 0 A 0 -.Z

L1 A53 I54 Z I62 A C I T M6 68 2 In men tons Roer 6f Malone fiabert A. Renaud,

Louis (2 fiey s,

United States Patent 3,393,389 ADJUSTABLE BRIDGING CONTACT MEMBER TYPE THERMOSTATIC SWITCH Robert G. Mawney, Louis C. Beggs, and Robert A.

Renaud, Attleboro, Mass, assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Continuation of abandoned application Ser. No. 436,721, Jan. 25, 1965, which is a continuation of application Ser. No. 34,043, June 6, 1960. This application Aug. 25, 1966, Ser. No. 575,184

4 Claims. (Cl. 33757) ABSTRACT OF THE DISCLOSURE A snap acting thermostatic sensing type switch is disclosed in which the thermostatic element is included in a main circuit and when actuated in response to current or heat developed therein operates to interrupt a second circuit. The thermostatic member is interconnectd with a contact carrying bridge member which moves in response to movement of the thermostatic element.

This application is a continuation of application Ser. No. 436,721, filed Jan. 25, 1965 in the name of Mawney et al. for an Adjustable Bridging Contact Member Type Thermostatic Switch, now abandoned, which application was a continuation of US. application Ser. No. 34,- 043, filed June 6, 1960, in the name of Mawney et al., for Bridging Contact Member Type Thermostatic Switch, now abandoned.

This invention relates to thermostatic switches of the snap-acting type, and in particular, to improved contact arrangements and electrical connections for such switches.

It is one object of the instant invention to provide a thermostatic switch which includes a thermostatic snapacting element and a bridging contact member having a motion transmission member interconnected therebetween.

It is another object of the instant invention to provide such a thermostatic switch wherein creeping of thesnap-acting thermostatic element is obviated or at least minimized.

It is another object of the instant invention to provide a thermostatic switch of the class described which can be adjusted quickly and easily.

It is another object of the instant invention to provide a simple, low-cost thermostatic switch which does not require complicated lever, spring or other more expensive sophisticated arrangements, which are difficult to manufacture, calibrate and maintain in calibration.

Among the further objects of the invention are the provisions of such a switch structure which is compact, dependable in use, economical to manufacture, and the component parts of which can be rapidly and easily assembled and retained in operative condition.

Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which one of the various possible embodiments of the invention is illustrated:

FIG. 1 is a top plan view of an electrical switch embodying the present invention;

FIG. 2 is a bottom view thereof, with the cover mem ber removed for clarity of illustration;

3,393,389 Patented July 16, 1968 FIG. 3 is a bottom plan view of the casing only, on a reduced scale, with other component parts omitted for clarity of illustration;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 1;

FIG. 5 is a view similar to FIG. 4, showing relative movement between the parts, with certain portions thereof broken away and shown in phantom;

FIG. 6 is a sectional view taken on line 6-6 of FIG. 4;

FIG. 7 is a view similar to FIG. 6, taken on line 7-7 of FIG. 5;

FIG. 8 is an enlarged plan view of a thermostatic disc and bridging contact subassembly, according to the instant invention;

FIG. 9 is a sectional view taken on line 9-9 of FIG. 8;

FIG. 10 is a sectional view taken on line 1010 of FIG. 9; and

FIG. 11 illustrates a schematic circuit in which the invention may be used.

In the use of thermostatic elements of the snap-acting kind to actuate switch elements, it is generally desirable, and may even be necessary, to make some arrangement to prevent the switch contacts from creeping into or away from a closed position. This has been done in some prior art devices by providing lost motion connections between the snap-acting element and the contacts which it operates. Many times, in some types of structures, such lost motion connections are not desirable and other means must be provided. The prior art constructions have generally involved complex linkages, spring arrangements, and/or other complex, expensive arrangements. The instant invention solves the problems described above, and others to be more fully described below, in a simple and economical manner.

The invention is also concerned with the problem of making a simple sensing type unit in which the thermostat element does not itself interrupt the main current and whatever circuit it includes, but instead operates another set of contacts which in turn, when actuated, may interrupt a second circuit and actuate other switch elements in the circuit to interrupt the main circuit. An example of such prior art devices mentioned above and an exemplary circuit is described in the US. Patent No. 2,694,121 to Vander Pyl et al., issued on Nov. 9, 1954. In such a sensing unit, the main current is passed through the snap-acting thermostatic element, which thermostatic element, although free to move or snap in response to current and heat developed therein, nevertheless does not interrupt the current but merely serves as a means to pass the main current therethrough.

Referring now to the drawings, in FIG. 1 there is shown an electrical switch, generally referred to by numeral 10, which embodies the instant invention. Switch 10 includes a casing 12, which may be made of electrical insulating material, such as a moldable, phenolic resin. Base or casing 12 is open-ended and includes a projecting, hollow, portion 14 which is adapted to receive a portion of a thermostatic disc-bridging contact subassembly, generally referred to by numeral 20, tobe described below. Base 0r casing 12 is closed by a cover member 16 which interfits with a peripherally extending shoulder 18 providedby casing 12. Cover member 16 may be secured to casing 12 in any known, convenient manner such as by gluing, bolting, etc.

Referring now to FIGS. 4, 5 and 9, subassembly 20 includes an inherently snap-acting thermostatic element 22, of the type described in the Spencer United States Patent No. 1,448,240, or the Vander Pyl et al. United States Patent No. 2,694,121, mentioned above. Disc 22 is provided with a substantially centrally disposed aperture 24. Snap-acting element 22 is mounted on a post 26, between flanges 28 and 30, which are fixed to member 26, as shown. The flanges 28 and 30 provided by member 26 4 and 5). Thus, it can retain the snap-acting element 22 therebetween in nonbinding relation thereto. In this regard, snap-acting element 22 is substantially freely rotatable relative to post 26, but is prevented from substantial movement longitudinally or transversely of the post 26. Snap-acting element 22 is automatically snappable in response to temperature change (for example, due to heating thereof upon the flow of a current overload therethrough) from a first position of relative stability to a second position of relative stability, and upon cooling thereof, is snappable from said second position back to said first position. Such positions of relative stability and of opposite configuration are illustrated in FIGS. 4 and 5. Casing member 12 provides longitudinally extending shoulder portions 32 and 34, as best seen in FIGS. 2 and 3, which are respectively engageable with cars 36 and 38 provided by thermostatic snap-acting element 22, to inhibit or prevent rotation thereof about post 26. Flange 30 is preferably shaped as a hexagonal or octagonal nut for adjustment convenience, for a purpose to be described below (see FIGS. 2, be seen that upon snapping of disc 22 from one position of stability to another position of stability of oppositely bowed configuration, that post 26 will move positively therewith in each of two opposite directions.

Subassembly 20 includes a sleeve 42, formed of an electrically insulating material such as moldable, phenolic resin, having an open-ended cylindrical bore or caviety 44, a portion of which is threaded as at 46 and is adapted to receive a threaded portion 40 of post 26 in adjusted, threaded engagement. Cylindrical aperture 44 includes an unthreaded portion 48 thereof adjacent disc 22, which is of slightly larger diameter so as to facilitate entry of post 26. Sleeve 42 includes a headed shoulder portion 50 adjacent the free end thereof, as shown. An apertured, movable bridging contact member 52 is slidably mounted about shank portion 54 of sleeve 42. Bridging member 52 is preferably formed of a high electrical conductivity material and includes a pair of spaced electrical contacts 56 and 58, which are adapted to respectively mate with stationary contacts 60 and 62, as best seen in FIGS. 6 and 7. Stationary electrical contacts 60 and 62 are respectively provided by terminal members 64 and 66. Terminals 64 and 66 and contacts 60 and 62, respectively carried thereby, are conveniently mountable in casing 12, from the exterior thereof. Casing 12 provides apertures 68 and 70 and shoulder portions 72 and 74, which respectively receive and guide terminals 64 and 66 and the contacts carried thereby, into fixed assembled relation with respect, to the bridging contact member 52 and casing. Terminals 64 and 66 may be fixed to casing 12 by means of rivets 76 and 78, as clearly shown in FIG. 6. Each of terminals 64 and 66 includes an edge portion 80 which is engageable with an exterior surface of casing 12 to limit the extent of inward insertion of contact members 60 and 62, as clearly shown.

Referring now to FIGS. 7 and 9, sleeve 42 includes an annularly extending recessed shoulder portion 82, which is adapted to receive and seat one end of a spring 84. The other end of spring 84 engages the underside of the bridging member 52, and urges the latter upwardly, as best seen in FIG. 9, into engagement with stop means provided by the lower surface 86 of headed-over portion 50, which is formed integrally with sleeve 52. As best seen in FIG. 10, bridging contact member 52 is provided with a rectangular or square aperture 88, which is adapted to mate and interfit with a complementary shaped, projecting boss portion 90 provided by headed-over portion 50. Rectangular opening 88 and complementary shaped boss portion 90 are adapted to co-operate to prevent bridging contact member 52 from axially rotating relative to shank 54 of sleeve 42. Spring 84 urges briding contact 52 upwardly into engagement with underside 86, and urges the latter also for engagement between rectangular opening 88 and boss 90. As best seen in FIG. 9, the thickness of 4 i boss 90 does not exceed that of the bridging contact member 52. Consequently, when the bridging contact member 52 is moved downwardly with respect to headed-over portion against the action of'spring 84 so that portion 90 is no longer in engagement with the rectangular opening 88, bridging contact 52 is free to axially rotate about shank portion 54 of sleeve 42. It can thus be seen that sleeve 42, when in threaded engagement with portion 40 of stem 26, comprises therewith a positive motion-transmitting mechanism which is secured both to the thermostatic snap-acting element 22 and also to the bridging element 52, so that positive motion in both directions can take place in response to corresponding movement of the snap-acting thermostatic disc.

Bridging contact member 52 has been shown as being relatively movable with respect to sleeve 42, and it should be understood that the provision of the spring 84 and the relative movement permitted between the bridging contact 52 and the headed-over portion 50 in an axial direction at least, is for purposes of permitting greater manufacturing tolerances. It is to be understood that the bridging element 52 may be fixed to the shank 54, i.e., by a pin or collar engaging the underside of bridging element 52, so that relative axial motion therebetween does not take place. Thus it can be seen that the bridging element wil be positivey moved in each of two opposite directions corresponding to the direction of snapping of the snapacting element 22.

Referring now to FIGS. 6 and 7, the lower surface 86 of headed-over or shoulder portion 50 is curvilinear in one direction, which is shown as being longitudinally of the bridging element 52. Bridging element 52 thus makes line contact with the curvilinear, lower surface portion 92 of member 50, and is free to rotate or rock thereabout for adjusting the relative position between contacts 56, and 58, 62. If stationary contacts 60, 62 do not lie in a line or plane perpendicular to the motion-transmitting mechanism, bridging contact member 52, by being rotatable about arcuate shaped or curvilinear portion 92, will adjust itself by rotating thereabout so that the contacts of the bridging element will mate properly with both stationary contacts. It is to be understood that rectangular or square shaped aperture 88 is sutficiently larger than boss portion or projecting portion so as to permit the bridging element to rotate or rock about curvilinear portion 92. The arrange ment of curvilinear portion 92 and contact bridging element 52 advantageously permits greater manufacturing tolerances, thus resulting in lower cost.

Referring now to FIG. 7, curvilinear portion 92 has a radius r as shown therein, and has a definite relationship with r a radius of curvilinear portion of a stop member provided by casing 12 for a purpose to be described below.

As best seen in FIGS. 4, 5 and 9, bridging contact element 52 has a curvilinear portion 94 which is arcuate shaped in a direction transverse to the direction of curvature of portion 92 of headed-over portion 50. Thus bridg ing contact member 52, by virtue of its curvilinear surface portion 94, as described above, is also adapted to rock or pivot about the lower surface portion of headed-over portion 50 in each of two transverse directions so as to adjust itself for proper seating of contacts 56 and 58 with stationary contacts 60 and 62. The two-way adjustment, advantageously provided by the curvilinear portions of headedover or shoulder portion 50 and bridging contact 52, advantageously permits greater manufacturing tolerances and lower cost production.

Referring now to FIG. 9, headed-over portion 50 includes a beveled aperture portion 96, which in cooperation with aperture 98 provided by casing member 12 is adapted to receive an epoxy compound which will lock adjustment screw or post 26 in place with respect to sleeve 42 after the two have been set in final adjusted position.

Disc 22 has respectively electrically connected at each of cars 36 and 38, a pigtail electrical connection 100 and 102. Pigtails 100 and 102 are respectively electrically connected to terminals 104 and 106. Casing 12 provides apertures 108, 110 and shoulders 112 and 114, to receive and maintain terminals 104 and 106 in fixed assembled relation. Terminals 104 and 106 may be fixed and secured to casing 12 by any known convenient means, such as for example, by staking, or more conveniently, by means described and claimed in U.S. patent application, Ser. No. 40,337, filed July 1, 1960, to Robert G. Mawney and Walter R. Harper, In, which application is assigned to the assignee of the instant application.

Subassembly 20, which comprises the thermostatic snapacting disc 22; pigtails 100, 102; terminals 104, 106; adjusting screw or threaded post 26; sleeve 42; bridging contact 52 and headed-over portion 50; and spring 84, may be made up as a separate subassembly and quickly and easily mounted into the casing 12.

Headed-over or shoulder portion 50 of sleeve 42 is provided with a pair of projections 116 and 118, which are respectively received in and mate with longitudinally extending, complementary shaped, recessed grooves 120 and 122 provided by casing member 12 in aperture 14. Projections and grooves 116, 120 and 118, 122 interfit and cooperate respectively to guide button or headed-over shoulder portion 50 for reciprocal movement axially of adjustment screw 26 and sleeve 42 in response to snap-action of disc 22 within cylindrical cavity 14. Further, projections 116 and 118 co-operate with their respective recess to prevent relative rotation between the button or shoulder member 50 and the casing It should be noted that corresponding projecions (no shown) could be provided on boss or projection 90 and aperture 88 to prevent inadvertent misorientation between the button or shoulder portion 50 and the bridging contact element 52. Subassembly 20 can be quickly and easily mass produced and assembled as a separate subassembly in the following manner:

(1) Electrically connect pigtails 100 and 102, to ears 36 and 38 after the non-developable portion or dished portion of disc 22 has been formed.

(2) Insert stem or adjustment screw 26, with its integral flange 28, through the central aperture 24 in disc 22 and secure hexagonal shaped flange 30 to the post 26.

(3) Sleeve 42 is formed integrally with headed-over portion or button 50 and is quickly and easily assembled with bridging contact 52 merely by slidably inserting bridging contact 52 about shank portion 54 and inserting spring 84 thereabout until the reduced diameter end of the spring snaps into place in annularly shaped shoulder 82.

Subassembly 20 can be made up into two separate subassemblies, one of which is a subassembly of the disc 22, threaded adjusting post 26, pigtails 100 and 102, and terminals 104 and 106. The other part of subassembly 20 would comprise sleeve 42, spring 84, bridging contact member 52 and button 50.

Assembly of the switch thus far described can be done quickly and easily in the following manner:

(1) Dispose button 50 and sleeve 42, which carries with it bridging contact 52 and spring 34, within the opening 14 provided by casing 12 so that projections 116 and 118 are received in their respective longitudinally extending openings 120 and 122.

(2) Mount terminals 64 and 66 so that contacts 60 and 62 are in position for engagement by the bridging contacts 56 and 58.

The button assembly 50, sleeve 42 and bridging contact element 52 are thus retained within the casing 12 by stationary contacts 60 and 62, and are not free to be removed from casing 12.

The switch as thus far described is advantageously adapted to be provided as a subassembly and is susceptible to mass production and stockpiling of parts which are interchangeable. It can be seen that merely by substituting snap-acting discs 22 of different electrical ratings a variety of different electrically rated switches 10, having the same base and bridging contact subassembly, can be provided.

In order to complete the switch, it is then only neces sary to dispose the disc 22, threaded adjusting screw 26, pigtails and 102, and terminals 104 and 106 subassembly into the switch with the threaded stud 26 disposed within sleeve 42. Adjustment of the disc 22 and temperature setting thereof may be accomplished by rotating flange 30 to effect threaded adjustment between post 26 and sleeve 42 in the manner to be described below.

Casing 12 provides a pair of downwardly extending projections and 132, as best seen in FIGS. 4 and 5. Projections 130 and 132 are adapted to engage thermostatic disc 22 adjacent the periphery of the dished portion thereof. Projections or stops 130 and 132 serve the multiple function of providing a stop for the disc to bear against and snap from the bridging contacts-closed position shown in FIG. 5 to the position of oppositely bowed configuration (the bridging contacts-open position) shown in FIG. 4. The disc, in bearing against the stops 130 and 132, adjacent the outer periphery of the dished portion, advantageously co-operates therewith to prevent the snapacting disc 22 from creeping to move the contacts 56 and 58 to a contacts-open position prior to the occurrence of snap action. Thus, no creep action to a contacts-open position can take place, and snap action is assured.

Further, projections or stops 130 and 132, in bearing against the disc 22 adjacent the periphery of the dished portion thereof (which hearing may be inside the dished or dimpled area, or just directly outside this area), also serve as a stop for the disc to bear against when hexagonal flange 30 and adjusting screw 26 are rotated to adjust the disc during assembly thereof. When the screw 26 is rotated to adjust disc 22, the latter bears against stops 130 and 132, and since button or headed-over portion 50 is pulled in a downward direction, which downward movement is precluded by engagement of bridging contact '52 with stationary contacts 60 and 62, the disc is pulled upwardly into final adjusted temperature set position.

Adjusting screw 26, in co-operation with threaded sleeve 42, stops 130 and 132, and button 50, co-operate to produce at least two results upon rotational adjustment of screw 26. Upon rotation of screw 26, the disc is calibrated by changing the deformation of the dished portion, and also the contact pressure of the bridging contacts with the stationary contacts 60 and 62 is set or adjusted. The fact that there is a fixed bearing between the stationary and bridging contacts in conjunction with the co-operation of the stops 130 and 132 of the disc, contributes to making this multiple function possible. Thus, two calibration operations are performed simultaneously upon rotation of the adjusting screw 26. The advantages of this unique arrangement with respect to ease and facility of assembly and minimizing the cost thereof, are readily apparent.

Terminals 104 and 106 each respectively include a bent-over portion and 142, as best seen in FIG. 4. Bent-over portions 140' and 142 are respectively aligned with projecting stops 130 and 132 and are adapted to engage the underside of disc 22 adjacent the periphery of the dished portion of disc 22, as best seen in FIGS. 4 and 5. Bent-over portions 140' and 142 act as stops for the disc to bear against and snap from the position of concavity shown in FIG. 4 to that shown in FIG. 5. Stops 140 and 142 thus serve the same function as projecting stops 130 and 132 with regard to preventing the disc 22 from creeping to actuate the contacts prior to snap action. Stops 140 and 142 thus co-operate with the disc 22 to preclude the latter from creeping to a bridging contactsclosed position. The spacing between stops 130, 140 and 132, 142 is such as to loosely but controllably confine the disc to limit the latter to actuation of the contacts by snap motion. It is desirable that stops 130, 140 and 132, 142 be engageable with the disc 22 adjacent the periphery of the dished or dimpled portion, as described above, so as to preclude actuation of the bridging contacts by creep motion and to provide a maximum center throw of the disc on snapping. The center throw on the disc by snapping"'is'positively transmitted through the bridging contact element by the adjusting screw and sleeve arrangement described above. It will be apparent that the greater the center throw of the disc, the more motion will be transmitted to the bridging contact element and the greater will be the distance of contact separation between contacts '6, 60 and 58, 62. i

Referring now to FIG. 7, stops 130 and 132 include a curvilinear or arcuate shaped periphery 146 which has as its radius r It will be understood'that the spacing between stops 130, 140 and 132, 142 -will directly influence the amount of center throw of the disc and the contact-opening distance of the bridging contacts, (see FIG. 4). H

Curvilinear portion 146 serves to minimize or eliminate manufacturing tolerances with respect to the manufacture and formation of the thermostatic disc 22. During formation of the disc 22, the portion adjacent the periphcry of the dished portion may not be exactly fiat or coplanar and may have a slight transverse curvature. Curvilinear portion 146, with its radius r insures at least point or line contact with some part of the surface of the disc '22 adjacent the periphery of the dished portion. It is to be understood that portion 146 need not be curved but could have a point or a relatively small projection in order to accomplish the same function. In practice, radius r is generally less than that of any transverse curvature of the disc 22 which might be expected.

Curvilinear portions 92 and 146 (r and r cooperate to compensate for position variation of the disc 22, since the latter is restrained only to a given limited area; without affecting the operating characteristics of the device. Curvilinear portion 146 assures contact with the disc adjacent the periphery of the dimpled portion both when the disc is being calibrated upon rotation of screw 26 and also when disc 22 snaps from the position shown in FIG. 5 to that in FIG. 4.

It may many times be desirable that the radii r and r of the tolerance eliminating curvilinear surfaces 92 and 146 (see FIG. 7) be concentric so as to maintain the distance between the disc 22 and the curvilinear surface 92 substantially constant, even though there may be some slight transverse shifting of the disc. Maintaining this distance constant will desirably maintain the contactopening distances between bridging contacts 56, 60 and 58, 62 constant.

Switch 10, as described above, may be employed in a circuit wherein the snap-acting thermostatic disc acts as a sensing means to actuate a pair of contacts in a pilot circuit by means of the bridging contacts assembly.

In operation, terminals 104 and 106 would be electrically connected with one source of power, and disc 22, which is electrically connected to each of terminals 104 and 106 by pigtails 100 and 102, would have the main current running therethrough. The operation of switch 10 is as follows: Switch 10 can be normally open or normally closed. However, assuming it to be normally closed (which position is shown in FIG. 7), the motiontransmitting mechanism comprising threaded stud 26, sleeve 42, and button 50 would be held downwardly with the bridging contact member 52 held down against stationary contacts 60 and 62 in the contacts-closed position. Upon an increase in current through the disc 22, the thermal element 22 will heat until it reaches the snapping temperature, at which point it will snap to a position of opposite concavity from that shown in FIG. 7 to the position shown in FIG. 6. As disc 22 snaps from'the position shown in FIG. 7 to that of FIG. 6, the threaded adjustment screw 26 and sleeve 42, along with bridging contact member 52, move upwardly to open the contacts. As the disc begins to cool, upon reaching a predetermined temperature, it will snap back from the position shown in FIG. 6 to that shown in FIG. 7, and will move the motion-transmitting mechanism, along with the bridging contact, downwardly to again close the bridgingcontacts, as shown in FIG. 7. i i

Referring now to FIG. 11, there is illustrated schematically an exemplary circuit which embodies the device of the instant invention for control purposes. The main current flows .through one side of asource of power L to terminal 106, pigtail 102,;thermostatic disc 22, pigtail 1.00, terminal 104, electrical conductor 150, load L, conductor 152, contacts 153 and 154 of an auxiliary electromagnetic circuitbreaker generally indicated 'by numeral 156, and back by conductor 158 to L the other side of a power source. The control or pilot circuit connections are as follows: From one side of a power source L a current path is established by conductor or lead 160 through terminal 66, contact 62, contact 58, bridging Contactmember 52, contact 56, stationary contact 60, terminal 64, lead 162, through the coil of circuit breaker 156 and back to L the other side of a source of-power for the control circuit by conductor 166. In this circuit, it will be observed that circuit breaker 156 is controlled by bridging contact 52.

Thus, if excessive current flows in the main power circuit (L L thermostatic element 22 will heat to its snapping temperature and will snap and move bridging contact member 52 by a positive transmission of motion thereto, to open contacts 56, and 58, 62 to open the control circuit and alsoopen the main power circuit through actuation of circuit breaker 156.

From the above. it can be seen that the instant inventionprovides a number of unique features which serve multiple functions and produce a number of unique and unobvious advantages. 1

The positive motion-transmitting mechanism which comprises generally the adjustingscrew 26, sleeve 42 and headed-over portion 50, in co-operation with stops and 132, advantageously permits calibratingthe thermostatic snap-acting element 22 and alsosetting the contact pressures between the bridging element and stationary contactsupon rotation of adjusting screw 26. Thus, two functions are accomplished upon rotation of the adjusting screw.

Further, the unique motion transmission between the disc and the bridging contact element, in either of two opposite directions corresponding to snapping movement of the disc, advantageously eliminates the necessity for more complex and expensive motion-transmitting arrangements such as lost motion connections, linkages, spring arrangements, etc.

The curvilinear portions of the button 50, the bridging contact plate 52,. and stops 130 and 132 advantageously eliminate manufacturing tolerance build-up and co-operate to afford quick and inexpensive production, and eliminate possible undesirable creep conditions due to tolerance accumulation.

In view of the above, it will be seen that the several objects of the inventionare achieved and other advantageous 'results attained.

Dimensions of certain of the parts as shown in the drawings have been modified for the purposes of clarity of illustration.

As many changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense, and it is also intended that the appended claims shall cover all suchequivalent variations as come within the true spirit and scope of the invention.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or Carried out in various ways. Also, it is to be understood that the ,phraseology or terminology employed herein is for the purpose of description and not of limitation.

We claim:

1. An electrical switch comprising a casing; a first pair of electrical contacts; a; snap-acting thermostatic disc; a bridging contact member including a pair of bridging contacts adapted to move into and out of engagement with said first pair of contacts in response to movement of said snap-acting disc; means interconnected between said disc and bridging contact member for moving said bridging contact member in each of two opposite directions in accordance with corresponding movement of said snap-acting thermostatic disc; said means comprising an adjusting screw mounted on said disc intermediate the ends thereof and extending in a direction toward said bridging contact member; a sleeve member having a threaded aperture which receives at least a threaded portion of said screw member for adjustable threaded engagement therewith; said bridging contact member being mounted on and carried by said sleeve; said disc having a non-developable portion responsible for its snap action; said casing providing projecting stop members engageable each with a portion of said disc adjacent the periphery of said nondevelopable portion whereby to preclude said disc from actuating said bridging contacts in a first direction by creep action prior to the occurrence of snap action; said switch including a pair of spaced electrically conductive terminals; means electrically connecting said disc in series circuit relationship with said terminals; and said terminals providing stop portions spaced from said pro jecting stop members and engageable with portions of said disc adjacent the periphery of said nondevelopable portion whereby to prevent said disc from actuating said bridging contacts in a second direction by creep action prior to the occurrence of snap action.

2. An electrical switch comprising a first pair of electrical contacts; a snap-acting thermostatic disc; a bridging contact member including a pair of bridging contacts adapted to move into and out of engagement with said first pair of contacts in response to movement of said snap-acting disc; means interconnected between said disc and bridging contact member for moving said bridging contact member in each of two opposite directions in accordance with corresponding movement of said snap-acting thermostatic disc; said means comprising an adjusting screw mounted on said disc intermediate the ends thereof and extending in a direction toward said bridging contact member; a sleeve member having a threaded aperture which receives at least a threaded portion of said screw member for adjustment therebetween; said bridging contact member being mounted on and carried by said sleeve; said bridging contact member being slidably mounted on said sleeve for movement relative thereto in a direction toward and away from said thermostatic disc; said sleeve being provided with a projecting boss portion at a free end thereof which is adapted to engage said bridging contact member to limit relative movement between said bridging member and sleeve in a direction away from said thermostatic disc; and spring means urging said bridging contact member for movement in a direction away from said thermostatic disc, and for movement into engagement with said projecting boss portion; and said projecting boss portion including a pair of spaced laterally projecting ribs each engageable with a respective one of a pair of longitudinally extending guiding grooves provided by said cavity in said casing.

3. In combination: a housing; a snap-acting thermostatic member and a bridging contact member both disposed in said housing, said snap-acting member being electrically connected with a first pair of electrically conductive terminals mounted on said housing; a second pair of electrically conductive terminals mounted on said housing and each providing an electrical contact for engagement with a respective one of a pair of electrical contacts carried by said bridging contact member; means interconnected between said thermostatic member and bridging contact member for moving said bridging contact member in each of two opposite directions in accordance with corresponding movement of said snap-acting thermostatic member; said means comprising an adjusting screw mounted on said thermostatic member intermediate the ends thereof and extending in a direction toward said bridging contact member; a sleeve member having a threaded aperture which receives at least a threaded portion of said screw member for adjustment therebetween; said bridging contact member being carried by and slidably mounted on said sleeve for movement relative thereto in a direction toward and away from said thermostatic member; said sleeve including stop means engageable with said thermostatic member and spring means urging said bridging contact member for movement in a direction for engagement with said stop means.

4. In combination: a housing; a snap-acting thermostatic member and a bridging contact member both disposed in said housing, said snap-acting member being electrically connected with a first pair of electrically conductive terminals mounted on said housing; a second pair of electrically conductive terminals mounted on said housing and each providing an electrical contact for engagement with a respective one of a pair of electrical contacts carried by said bridging contact member; means interconnected between said thermostatic member and bridging contact member for moving said bridging contact member in each of two oppposite directions in accordance with corresponding movement of said snap-acting thermostatic member; said means comprising an adjusting screw mounted on said thermostatic member intermediate the ends thereof and extending in a direction toward said bridging contact member; a sleeve member having a threaded aperture which receives at least a threaded portion of said screw member for adjustable threaded engagement therewith; and said bridging contact member being mounted on and carried by said sleeve.

References Cited UNITED STATE S PATENTS 1,894,842 1/1933 Appelberg 200138 1,897,316 2/1933 Marshall 200-438 1,997,262 4/1935 McGoldrick 200-139 2,238,881 4/ 1941 Evans 200-138 2,471,924 5/1949 Bolesky 200122 2,501,155 3/1950 Bolesky 200113 2,694,121 11/1954 Vander Pyl 2001 14 2,720,416 10/1955 Raleigh 200--1 14 2,753,421 7/1956 Mertler 200-438 2,753,422 7/1956 Mertler 200-138 2,757,256 7/1956 Cataldo et a1. 200-438 2,860,208 11/1958 Epstein 200--113 2,901,574 8/1959 Raab 200-1 14 2,907,847 10/1959 Grenier et a1. 2001 16 2,912,546 11/1959 Arey 2001 16 3,104,296 9/1963 Moksu 200138 BERNARD A. GILHEANY, Primary Examiner. G. HARRIS, 111., Assistant Examiner.

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