US3042776A

US3042776A - Electrical switches

Info

Publication number: US3042776A
Application number: US840327A
Authority: US
Inventors: Ralph G Arey; David E Clarke
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1959-09-16
Filing date: 1959-09-16
Publication date: 1962-07-03
Anticipated expiration: 1979-07-03
Also published as: GB966298A

Description

July 3, 1962 R. G. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 1 In ya u tars,

RALPH G. AREY DAVID E. CLARKE July 3, 1962 R. G. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 2 NIH] Inven to r5,

RALPH G. AREY DAVID E. CLARKE Atty.

y 1962 R. e. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 3 //0 l, #2; \Jii. I /06 z l0? HES [721/672 tors,

RALPH e. AREY DAVID E. CLARKE July 3, 1962 R. G. AREY ETAL I 3,042,776

ELECTRICAL SWITCHES 6 Sheets-Sheet 4 Filed Sept. 16, 1959 RALPH G. AREY DAVID E. CLARKE July 3, 1962 R. G. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 e Sheets-Sheet 5 In 7/672 to rs,

RALPH G. AREY DAVID E. CLARKE MQ WJ July 3, 1962 R. G. AREY Em 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 6 Inventors, RALPH s. A Y

DAVID E. CL E Att y.

in phantom lines;

3,042,77 6 ELEQTREAL SWITCHES Ralph G. Arey, Brockton, and David E. Clarke, Norton,

Mass, assignors to Texas Instruments Incorporated,

Dallas, Tex., a corporation of Delaware Filed Sept. 16, 1959, Ser. No. 840,327

' 17 Claims. (Cl. 200-116) The instant invention relates to electrical switch structures, and more particularly, to thermally responsive switch structures.

An object of this invention is to provide an improved switch structure incorporating a new and improved combination of interrelated parts.

A further object is to provide such a switch structure which accommodates the use of compressive resilient biasing means for biasing operating parts thereof.

Another object is to provide such a switch structure utilizing a thermal type latch means and a new and improved mechanical latch means, which mechanical latch means functions Withoutupsetting the calibration of the thermally responsive latch means thereof.

A further object is to provide a thermally responsive switch which is also mechanically actuable repeatedly as an on-olf switch without upsetting the calibration of the thermally responsive means thereof.

Another object of the invention is to provide such a switch structure which exhibits improved electrical contact pressure characteristics.

Another object of the instant invention is to provide such a switch structure which affords snap-opening and snap-closing of the electn'cal contacts.

Among the further objects of the instant invention are the provisions of a switch which is' durable, accurate, reliable in operation, compact, easily calibratable, has vibration stability, which embodies a minimum number of parts, and which is simple in construction and economical to manufacture. I

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 v 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: v

FIG. 1 is a vertical section, with some'parts broken away and others in elevation, in a thermally responsive switch embodying the instant invention, showing the 3,042,776 Patented July 3, 1962 ice FIG. 9 is a top plan view of a part of the resetting means of the switch of the instant invention;

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

FIG. 11 is an elevational view, partly in elevation and partly in section, of a part of the mechanical latching means of the switch of the instant invention.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

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

The instant invention relates to electrical switches of the class such as that described and claimed in the earlierfiled copending applications, Serial No. 732,550, filed May 2, 1958, now matured into PatentNo. 2,912,546, issued: November 10, 1959, and Serial No. 837,754, filed September 2, 1959, now matured into Patent number 3,022,402, issued February 20, 1962.

Referring to'FlG. 1, an electrical switch embodying the instant invention is shown taking the form of a circuit breaker indicated generally by the reference numeral 20. The switch includes a base or casing 22 which carries a bushing 24 having an annularly extending flange 26, which mates with a correspondingly-shaped recess 28, provided by a cover member 84 for casing 22 which maybe sea sleeve 38 disposed in another aperture of smaller di ameter'in button assembly 32, as best seen in FIG. 1. Stem 36 is secured in fixed relation to button 32 by means of a beveled portion 40 on stem 36, which abuts the lower portion of flanged sleeve 38 (as best seen in FIG. 1), and a nut 42 which is threaded onto the upper end of stem 36, in a suitable recess provided by button assembly 32. \After nut 42 is tightened to secure stem 36 to button assembly 32, asealing compound 44 is introduced and a cover member 46 is applied to close the opening in buttonassembly 32, all of which is 'clearly'illustrated in FIG. 1.

Bushing 24 provides an abutment or. projection 48, which is received in a vertically extending slot 49 pro vided by button 32. Abutment or projection 48, which interfits with slot 49, prevents rotation of the push button relative to the switch casing and also provides one parts thereof in full lines in the retracted, contacts-open position and the parts in dashed lines in the reset, contacts-closed position;

FIG. 2 is a vertical sectiontaken on line 2-2 'of'FlG. l, with some parts shown in full lines and others in section; 1 1

PEG. 3 is a top plan view on an enlarged scale of'the thermally responsive member of the switch;

FIG. 4 is a front elcvational view of the thermally responsive member shown in FIG. 3;

FIG. 5 is an end view of the thermally responsive member shown iii-FIGS. 3 and 4;

FIG. 6 is a view similar to FIG. 1, showing the parts thereof in full lines in the reset, contacts-closed position, and showing the parts thereof in dashed lines in the retracted, contacts-open position; i I

FIG. 7 is a sectional view taken on line-7-7 of FIG. 6, with certain of the parts shown in full lines-and others means for limiting downward movement of the push button 32, as viewed in FIG. 1. Anannulus or band of a color contrasting with that of-the push button member 32 and the bushing 24 may be provided, if desired, to indicate the relative switch positions, in a well-known manner. Bushing 24 is externally threaded, as at 50, for the reception of a nut or nuts (not shown) for mounting the switch on a support.

Stem 36 is provided with a portion 52 of enlarged diameter, having a beveled portion 54 adjacent the smaller diameter portion 36a of stem 36.

and resiliently biases member 58 against beveled portion 54 and away from button 32 in a contacts-closing direc- Manually operable resetting means 34 further includes an abutment member tion. The upper end of spring 60, which is disposed about reduced diameter portion 36a of stem 36, abuts a nut 62, which is in threaded engagement with the portion of the stem 36a adjacent sleeve 38. Aperture 39 has a cross sectional configuration which is complementary to that of nut 62 and thereby serves to prevent relative rotation between nut 62 and button assembly 32. Adjustment of the compressive biasing force of spring 60 may be effected by rotation of stem 36 relative to nut 62 before nut 42 is tightened and the sealing compound 44 and cover 46 are applied. As will be explained in greater detail below, spring 60 serves as a means for providing desired contact pressure.

As best seen in FIGS. 1, 9 and 10, aperture 59 provided by abutment member 58 has a substantially larger diameter than the outside diameter of smaller diameter portion 36a of stem 36, whereby member 58 has a loose, unconfined fit with this portion of the stem when the resetting means is in the reset contacts-closed position, as shown in FIG. 6. Aperture 59 also includes a countersink or beveled portion 55 engageable with interfitting beveled portion 54- provided by enlarged diameter portion 52 of stem 36 under the bias of spring 60 when the resetting means is in the retracted contacts-open position shown in FIG. 1.

Manually operable resetting means 34 includes an annular abutment 61 on member 58, and is movable from the positions shown in full lines in FIG. 1 to the positions shown respectively in full lines in FIG. 6, into en-' gagement with a thermally responsive unit indicated generally as at 100 to move the latter from a contacts-open to a contacts-closed position, as will be more fully described below.

Referring now particularly to FIGS. 3-5, the exemplary thermally responsive unit illustrated therein comprises a thermally responsive element formed of a section of composite material. The high-expansion component of the composite material, as shown in the embodiment of the drawing, is indicated at 1112 (HES) and the low-expansion component is indicated at 104 (LES). Thermally responsive unit 100 provides a longitudinally extending slot 106 through which enlarged diameter portion 52 of stem 36 extends whereby thermally responsive unit 100 is slidably mounted on stem 36. Thermally responsive unit 100 provides a longitudinally extending bridging portion 108, which carries

movable contacts

110 and 112 which are electrically connected to the lowexpansion side 102 thereof. Thermal unit 100 thus serves as a movably mounted means for carrying

movable contacts

110 and 112. Thermally responsive unit 100 is further provided with and carries a pair of opposed spaced slotted

arms

114 and 116, as best seen in FIGS. 2 and 5.

Accordingly, thermally responsive unit 100 provides an electrically conductive path leading from contact 110 through the bridging portion 108, through

arms

114 and 116, to contact 112. Due to the heating of the thermally responsive element 100 upon the flow of electrical current therethrough, the thermally responsive element flexes or warps to the dotted-line condition shown in FIGS. 2, 4, and 7, whereby

arms

114 and 116 are deflected away from each other. The distal

ends'of arms

114 and 116 are engageable with abutment 61 provided by member 58, and the surface presented by this abutment is tangential to the are traced by the distal ends of

arms

114 and 116 as the latter move away from each other under said warping of the thermally responsive element.

Referring again to FIGS. 1 and 2, thermally responsive member or unit 100 is resiliently biased from the contacts'cl'osed position (shown in full lines in FIG. .6 and in dashed lines in FIG. 1) to the contacts'open position, as shown in full lines in FIG. 1, by means ofa compression spring 64 which is disposed about stem 36. The upper end of compression spring 64 abuts a layer of electrical and heat insulating material 68 provided on the lower surface. of thermal member as clearly seen in FIGS. 1 and 2. Insulating member 68 serves as an insulator spring seat and prevents short circuiting of the thermal element by spring 64' and stem 36 and localizes the heat at the thermal element. The other end of compression spring 64 abuts a latching ring member 160, as will be described in greater detail below.

Casing or housing 22 provides a pair of abutments 99 for limiting the extent of upward movement of thermally responsive member 100 from a contacts-closed to a contaets-open position by engagement thereof with the upper surface of bridging portion 108, as clearly shown in FIGS. 1 and 6. Housing member 22 provides recesses 70 for the reception of

terminals

72 and 74, respectively.

Terminals

72 and 74 are so configured as to interfit with casing 22 for rigid mounting. A sealing compound 80 is disposed about

terminals

72 and 74 when in final assembled condition.

Terminals

72 and 74 respectively carry fixed

contacts

76 and 78 for co-operative engagement respectively with movable contacts and 112, as shown. As is clear from the drawing, thermally responsive member 100 provides a bridging member electrically connecting

contacts

76 and 78 when the thermally responsive member is in a contacts-closed position, as shown in FIG. 6.

It will be noted that thermally responsive member 100 is prevented from rotation about its axis and with respect to the casing by the engagement of respective surfaces thereof with adjacent portions of the casing. Referring to FIGS. 1 and 2, it will be apparent that the marginal edges presented by the thermally responsive unit 100 engage adjacent surfaces of the casing to prevent undue lateral shifting thereof as well as to prevent rotation thereof. Further, the slidable mounting of the thermally responsive member 100 on portion 52 of stem 36 also serves to prevent undesired lateral shifting of the thermal element with respect to the casing.

Stem 36 is compressively biased in a contacts-opening direction by means of a compression spring 120, housed in spring cup 122, which may be formed of a metallic or phenolic material. One end of spring abuts'a rivet 124 which serves to mount spring cup 122 in housing 22, and the other end of spring 120 is received in an axially extending recess 126 provided by the lower end portion 146 of stem 36, as clearly seen in FIG. 1.

Housing 22 provides a recess formed by

walls

132 and 136 for housing the spring cup and mechanical latching means which will be described in greater detail below. Spring cup 122 is disposed in and is entirely enclosed in the recess provided by housing 22, as clearly seen in FIGS. 1, 2 and 6. Compression spring 120 thus urges stem 36 and abutment member 58 (through engagement of beveled portion 54 of the stem and beveled portion 55 on the abutment member 58) and button 32 in a contacts-opening direction.

Switch 20 includes mechanical latching means for latching the stem in a reset, contact-closed position when the thermal element 100 isthermally latched to the stem for movement therewith as a unit in the contacts-closing direction. The mechanical latching means operates independently of the thermal latching and is mechanically actuable repeatedly-without upsetting the calibration of the thermally responsive means.

Stem 36 is provided intermediate its lower portion 146 and portion 52, with a portion 140 of enlarged diameter. The diameter of portion 140 is considerably greater than the diameter of portion 52 of stem 36. Portion 140 includes a circumferentially or peripherally extending groove which providesa detent surface 142, as clearly seen in FIG. 1. Adjacent the lower portion of portion 140 is a beveled portion 144, which intersects with the lowermost portion 1460f stem 36, which portion 146 is of slightly smaller diameter than that of portion140, for a purpose to be described below. 1 t

Detent surface or circumferentially extending groove 142 is adapted to receive and mate with a plurality of balls 150 for latching engagement therewith. Referringnow to FIG. 8, ball means b is shown as exemplarily comprising three balls, circumferentially spaced about stem 36 and mounted for movement in a direction normal to the longitudinal axis of stem 36, toward and away from, or into and out of engagement with, detent surface or groove 142, by means of suitable openings 152 provided by spring cup member 122 (as clearly shown in FIGS. 1 and 8). It should be understood that in the practice of the instant invention a greater or different number of balls could be provided, if desired. It has been found,however, that the employment of three balls, as illustrated, provides a stable mechanical latching arrangement.

Balls 150 are urged for movement into latching engagement'with detent surface or groove 14-22 by movable detent means comprising a latching ring 160, which may,- for example, be formed of a hardened stainless steel.

Latching ring 16! is slidably mounted on spring cup 122 and is guided for reciprocal vertical movement between the housing walls 132 provided by casing 22 and the outside circumferential surface of spring cup 122, and is thus confined to reciprocal sliding movement in a vertical direction, as seen in FIG. 1, Latching ring 160 includes an angularly disposed wedging surface 162 which is engageable with balls 15% to urge the latter into engagement with detent surface 142 upon downward movement of latching ring 160, as viewed in FIG. 1'. The outer circumferential portion of latching ring 160 is so shaped as to provide a spring seat for the lower end of spring 64 to abut, whereby spring 64 also compressively biases latching ring or detent ring 166 for movement downwardly to'urge balls 150 into latching engagement with detent surface 142 when thermal element ltltl'is moved into the contacts-closed position.

Latching ring 16% includes a lower beveled portion 164 which is disposed at an angle to wedge surface 162 and which permits balls 159 to move outwardly in opening 152, relative to detent surface 142 and spring cup 122 so as to permit disengagement of stem 36 frornthe balls 150 to thereby permit stem 36 tomove outwardly to the retracted, contacts-open position under the bias of compression spring 120.

The angle of beveled surface 162 on the latching ring 16%) which engages the balls 15b is such as to render the eiiective downward thrust of the latching ring 160 and the spring 64 greater than the upward thrust of the stem spring 12%) when the thermal element is in the contactsclosed position. I

The detent latching ring 169, as shown in elevationin FIG. ll, further includes an upper beveled portion 166 which is adapted to mate with an annularly or circumferentially extending projection 168 provided by spring cup 122 so as to limit upward movement of the detent ring 160.

It should be understood that spring cup 122 and latching ring 169, although shown as circular in cross section, could be of other geometric configurations, if desired.

The operation of circuit breaker 20 will now be described. With parts in the respective positions shown in full lines in FIG. 1, thermally responsive element 1% is in the retracted, contacts-open position, member 58 is in the retracted position and biased by spring 60 against beveled portion 54 provided by enlarged diameter portion 52 of stem 36, and button assembly 32, which is fixed to stem 36, along with stem 36 and member 58, is biased to the retracted position under the bias of compression spring 12%, whereby a band formed of a' color contrasting with that of the push button 32, if provided, would be visible exteriorly of the casing. It should be noted that in this condition, ball means 150 are disposed outwardly and are loosely in engagement with the circumferential outer surface of the portion146. of stem 36 (which, as shown, is of lesser diameter than 6 portion 140). Thermal element 100, when in the contacts-open position, is maintained against stop 99 by spring 64, which is in a relatively unstressed condition a when in the contacts-open position. Spring 64, when in the relatively unstressed condition in the contacts-open position, exerts little, if any, biasing force on latching ring 166).

When push button 32 is depressed to the advanced or reset contacts-closed position, the parts will take the respective positions shown in full lines in FIG. 6. As movement of push button 32 from the position shown in FIG. 1 to that shown in FIG. 6 ensues, the abutment 61 provided by member 58 moves intothermal latching engagement with the distal ends of each of

arms

114 and 116 provided by the thermally responsive element 166i, whereby the thermal element .100 and thestem 36 are thermally latched together as a unit for movement in the contacts-closing direction. Continued movement of push button 32 results in the compression of spring 60, (which by proper pressure setting, will provide desired contact pressure) compression of spring 64, which is effective to urge latching ring 160 downwardly, as viewed in FIG. 1, and move wedge surfaces 162thereof into engagement with balls 150 to urge the latter to tion, and that of biasing latch ring 160 into wedging er1- gagement with ball means 150 to urge the latter into latching engagement with stem 36.

With further movement of push button 32 and stem 36 to the reset position shown in FIG. 6, ball means 150 will traverse the axial or longitudinal extent of portion 146 of stem 36 and engage beveled portion 144 adjacent larger diameter portion 14%, whereby the resistance to beveled portion 144 and engages the vertical portion 145 movement of stem 36 to the reset or contacts-closed position will be sharply increased, requiring a greater force .to be applied against push button 32. With the application of increased force to push button 32 to overcome the resistance to movement of'stem 36 presented by the beveled portion, when ball means 150 traverses the "balls 150, which resistance diminishes suddenly as the balls liititraverse the beveled portion 144 and engage the vertical portion 145. At the point Where the balls 154D leave wedge surface 144 and engage surface 145,

the applied resetting force would be at a maximum and since at this point there is little or no resistance to movement of the stem 36 to the contacts-closing direction, the contacts will be closed with a snap action. This snap closing, which is advantageously afforded by the instant invention, is particularly desirable in eliminating or at least reducing contact erosion, which is generally characteristic ofdevices which do not afi'ord' a quick snap closing of contacts. 7

When push button 32 has been moved downwardly as seen in FIGS. 1 and 6, to the contacts-closed position sufficiently so that engagement of movable contacts and 112, respectively,

with'fixed contacts

76 and 78 has taken aoaawe mechanically latched in the contacts-closed position by the ball means 150 and detent surface 142 and latch ring 166, under the bias of spring 64. The movable abutment 58, which abuts the thermal element 100 at the distal ends of

arms

114 and 116 to provide the thermal latching, by being movable relative to the stem and being spring biased in a contacts-closing direction, provides contact pressure and a gap override to assure desired contact pressure.

With the parts in the contacts-closed, reset position shown in FIG. 6, an electrically conductive path is established leading from terminal 72 through contact 76, contact 110, thermally responsive bridging portion 166, through each of

arms

114 and 116, contact 112, to contact 78 and through terminal 74. Upon the flow of current of sufiiciently high values along the electrically conductive path just described, thermally responsive element 100 is heated by the current passing therethrough and expands thereby moving

arms

114 and 116 outwardly and away from each other to a dashed-line position as shown in FIGS. 2, and 7.

When'the thermally responsive element 100 warps or flexes sufliciently to move the distal ends of

arms

114 and 116 out of engagement with abutment 61 provided by member 58 to the broken-line position shown in FIGS. 2 and 7, member 58 moves to the broken-line position shown in -FIG. -7 under the bias of spring 60 and thermally responsive unit 100 is no longer restrained in the contacts closed position and immediately begins to move upwardly to the contacts-open, retracted position, as shown in full lines in FIG. 1, under the resilient bias exerted by compression spring 64.

Referring now to FIG. 6, as thermally responsive element 100 moves to the contacts-open position shown in dashed lines in this figure under the bias of spring 64, said spring 64 expands and sharply decreases the biasing force exerted against latch ring 160 which is urging balls 150 into latching engagement with detent surface 142. As the thermal element in the unlatched condition continues to move upwardly to the contacts-open position shown in dashed lines in FIG. 6, the spring 64 Will continue to expand to further decrease the downward thrust against latch ring 160, to a point at which the effective downward thrust of the latch ring 160 and spring 64 will become less than the upward thrust of spring 120. At this point, stem 36 will begin to move upwardly and the lower peripherally extending portions of groove 142 will earn balls 150 outwardly against ring 160. Since latching or detent ring 160 is confined to vertical movement, ring 160 in this condition, will move upwardly against the now relatively unstressed spring 64 until the beveled surfaces 164 are adjacent balls 150, which will thereby permit balls 150 to move outwardly out of engagement with latching detent surface 142, whereby stem 36 will then quickly move to the retracted, contacts-open position under the bias of spring 120. Outward movement of stem 36 under 'the bias of spring 120 is limited by engagement of member 58 with the casing when bevel 54 of stem 36 is engaged with countersink or beveled portion 55 of member 58, as clearly shown in FIG. 1.

It should also be noted that after balls 150 are in engagement with the outer surface of portion 146, when stem 36 has moved to a retracted position as shown in FIG. 1, ring 160 may move downwardly to the position shown in this figure under the force of gravity and the,

in FIG. 1, thermally responsive member 100 will still be heated and due to the thermal expansion thereof,

arms

114 and 116 may be disposed in the outwardly displaced position shown in dashed lines in FIGS. 2 and'7. Accordingly, upon depression of push button 32 from the retracted position (shown in dashed lines in FIGS. 6 and 7 and in full lines in FIG. 1), while the thermally responsive element 1% is still in the heated condition with

arms

114 and 116 still deflected outwardly (as shown in the dashed line portions of the figures mentioned above),

downward movement of push button 32 and stem 36 fails to bring abutment 61 into engagement with the distal ends of arms 1 14 and '116, whereby the thermally responsive member remains in the retracted, contacts-open position. This feature is advantageous in that the movable contacts and 112. cannot be closed against

the'fixed contacts

76 and 78, respectively, on the faults which cause tripping of the circuit breaker, until the thermally responsive element 1% has cooled for a sufficient time interval so as to bring arms 1'14 and 116 into position or alignment for engagement by abutment 61.

Further, upon depression of the push button from the retracted to the advanced or reset position, while the thermal element is still in the expanded condition with

arms

114 and 116 in a condition which does not permit engagement by abutment 61, the stem 36'will not be latched by the mechanical latching means since spring 64 will not be from the dashed-line position shown in FIGS. 2, 5 and 7- to the full-line position shown in these figures, the parts are again in the conditions and positions as shown in FIG. 1 and are ready for resetting of the circuit breaker, as just described.

Circuit breaker 20 is further capable of being manually actuated for use as an on-off electrical switch. In this regard, with the parts in the advanced, reset, contactsclosed positions, as shown in dashed lines in FIG. 1 and in full lines in FIG. 6, push button member 32 may be grasped and forcibly pulled outwardly toward retracted position, whereby the manual force applied in conjunction with the upward thrust of spring 120 will be suificiently greater than the effective downward thrust of spring 64 and the wedging action of latching ring against balls 120; thermal element 100 will move upwardly out of engagement with fixed

contacts

76 and 78 under the bias of compression spring 64; the distal ends of

arms

114 and 116, however, will still be in engagement with abutment 61 of member 58, which will also move to the retracted position with movement of the thermally responsive member 100. It should be noted that the upper surface of portion 140 serves to engage the insulating washer 68 to prevent the thermal element from moving downwardly in relation to member 58 whereby to prevent

rarms

114 and 116 from moving to the underside of this member and out of alignment therewith. Surface or ledge 170 also may serve to engage the insulating washer 68 and thereby elevate the thermal element upon manual opening of the switch, as described above.

As noted above, the latching forces exerted to retain member 32, stem 36 and the parts fixed with respect thereto in the reset position, are independent of the forces exerted on thermally responsive member ltiil. This is advantageous in that repeated latching and unlatching due to manual on-oflt' switching of the circuit breaker will not upset the calibration of the thermally responsive member.

/ Circuit breaker 20 is trip-free in that the thermally responsive member 100 cannot be retained in a contactsclosed position by forcibly retaining push button 32 in the advanced or reset position upon the occurrence of a current overload through thermally responsive element 100. If button 32 and stem 36 are restrained in the advanced, reset position by forcibly holding push button 32 in the depressed, advanced position when the thermally responsive element has warped or deformed sufficiently to disengage the distal ends of

arms

114 and 116 from abutment 61, the thermally responsive member will move to the contacts-open position under the bias of compression spring 64 (button 32 and stem 36 will, of course, remain in the advanced position) and member 58 will move away from push button 32 from the fullline position to the broken-line position as shown in FIG. 7, under the bias of spring 60.

It will thus be noted that

members

32 and 58 will mov to retracted position under the bias of spring 120 upon release of the external application of the resetting force to the push button. This is because no mechanical latching of the stem 36 can take place unless the thermal element is moved to a contacts-closed position by virtue of the above-described cooperation of spring 64 with the thermal element and the latching ring 160.

It will be noted (seeFIG. 4) that when thermally responsive element 100 warps upon heating thereof,

movable contacts

110 and 112 are urged respectively against fixed

contacts

76 and 78, thereby causing an increase in contact pressure. Thus the instant switch affords an increase in contact pressure with an increase in temperature of the thermal element before tripping at an over-.

from abutment 61 for the release of the thermally responsive member to contacts-open position.

As

arms

114 and 116 move away from each other" upon warping of the thermally responsive element 1% due to heating of the latter when the parts are in the full-line, contacts-closed position shown in FIG. 6, it is likely, or possible at least, that one of these arms will move out of engagement with abutment 61 slightly before the other. The result will be that member 58 will tilt about the point of engagement of said other arm and abutment 61 will move laterally relative to portion 36a of stem 36 under the force couple effected by the bias of

springs

60 and 64. This tilting and/or lateral movement of member 58 is permitted by'virtue of the clearance as described above between the surface of member 58 defining aperture 59 and the outer surface of the stem portion 36a of stem 36. This tilting and/ or lateralmovement of member 58 permits disengagement of said other arm from abutment 61 and movement of the thermally responsive element 1610 to the retracted, contacts-open position, as shown in fulllines in FIG. 1',

promptly upondisengagement of said one arm from the abutment 61. Lateral and pivotal realignment of memlb is elfected when countersunk or beveled portion 35 moves into engagement with beveled surface 54 of the enlarged diameter portion 52 of stem 36, under the bias of spring 60, thus forcing member 53 back to laterally and pivot ally aligned relation with the remaining parts of the switch. Accordingly, abutment 61 which is provided by member 58, will be realigned for engagement by the distal ends of

arms

114 and 116 upon the cooling of the thermally responsive element 100 from the dashed-line position of FIGS. 2 and 5 to the full-line position of these FIGURES.

The switch of the instant invention'provides a number of unique and unobvious advantages. One of the advantages of the switch of the instantinvention is that the structural arrangement of the operating parts lends itself to the use of compressive resilient biasing means which provides substantial advantages over tension-type springs and the like. For example, the compression spring 64, which is employed between the thermal latch element and detent means or latching ring 160 provides a number of advantages over that which would be afforded by a tension spring type arrangement which might involve a number of tension springs and linkages.

By-use. of the compression spring, compactness and miniaturization of the switch structure is permitted and only a single spring element is required. The compression spring 64 affords a simple and quick assembly of parts. All that is necessary to assemble the spring in proper relation is to merely dispose it about the latching ring 160, before the thermal element 100 is mounted on the stem 36. i

Further, the compression spring arrangement of the switch of the instant invention provides a switch with greater vibration stability than that which might be afforded by a tension spring arrangement. The slidably mounted latching ring 160 with its wedge and beveled surfaces, is a simple one-piece construction which permits quick and easy assembly without the necessity of close tolerances. The ring is assembled in position merely by insertion over spring cup 122 before the latter is fixed to the housing by rivet 124. The fact that the mechanical latching mechanism is enclosed in the well or recess provided by the casing, rather than being an exposed part of the circuit breaker, provides the unique and advantageous result of preventing contact splatter and other deleterious debris (such as breakdown of housing material which is generallyassociated with high rupture capacity devices) from interfering with the operation of the mechanical latching mechanism. 7

Further the latching ring 160 provides a positive wedging action through a direct application of compressive force from spring 64, which provides a highly efi icient arrangement. The direct application of compressive force and compression spring and slidable latch ring arrangement co-operate to provide latching which is more I afford a force balance and to increase vibration stability.

Further, the mechanical latching arrangement with its compressive biasing force-permits the use of a one-piece thermal element construction, and eliminates any necessity for pivoted parts, pigtail arrangements, or other more complex constructions.

It can be seen from the above that the circuit breaker or switch 21) provides a device which is reliable, compact and which is simple in construction and economical to manufacture. I

In view of the above, it will be seen that the several objects of the instant invention are achieved and other unique and unobvious advantageous results attained.

As many changes could be made in the above constructions 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 I 11 cover all such equivalent variations as come within the true spirit and scope of the invention.

We claim:

1. An electrical switch comprising a base; contact means on said base; movably mounted means carrying movable contact means for engagement with said firstnamed contact means; manually operable means mounted in said switch for movement relative to said movably mounted means; thermally responsive means for latching said manually operable means and said movably mounted means together as a unit for movement in a contactsclosing direction; mechanical latching means for latching said manually operable means in a contacts-closed position when the latter is latched to said movably mounted means by said thermally responsive means; compressive biasing means compressively urging said mechanical latching means into latching engagement with said manually operable means when the latter is in the contacts-closed position; and said switch also including means providing for snap closing of said first-named and movable contact means.

2. The switch as set forth in claim 1 and wherein said mechanicallatching means is disposed in a recess provided by said base.

3.- An electrical switch comprising contact means; movably rnounted means carrying movable contact means for engagement with said first-named contact means; manually operable means mounted in said switch for movement relative to said movably mounted means; thermally responsive means forlatching said manually operable means and said movably mounted means together as a unit for movement in a contacts-closing direction; mechanical latching means for latching said manually operable means in a contacts-closed position when the latter is latched to said movably mounted means by said thermally responsive means; compressive spring biasing means urging said mechanical latching means into engagement with said manually operable means in the contactselosed position thereof, said biasing means also urging said movably mounted means to a contacts-open position.

4. An electrical switch comprising a base; contact means on said base; movably mounted means carrying movable contact means for engagement with said firstnamed contact means; manually operable means mounted in said switch for movement relative to said movably mounted means; thermally responsive means engageable with abutment means on said manually operable means for latching said manually operable means and said movably mounted means together as a unit for movement in a contacts-closing direction; compressive biasing means urging said movably mounted means in a contacts-opening direction; mechanical latching means for latching said manually operable means in a contacts-closed position when the latter is latched to said movably mounted means by said thermally responsive means, said mechanical latching means comprising detent surfaces on said manually operable means; detent means supported on said base for movement into and out of engagement with said detent surfaces; a latch member movably mounted with respect to said manually operable means and engageable with said detent means for moving the latter into latching engagement with said detent surfaces, said biasing means also urging said latch member into, and maintaining the same in, engagement with said detent means in the contacts-closed position thereof.

5. An electrical switch comprising a base; contact means on said base; movably mounted means carrying movable contact means for engagement with said firstnamed contact means; manually operable means mounted on said switch for reciprocal movement relative to said movably mounted means; thermally responsive means engageable with abutment means on said manually operable means for latching said manually operable means and said movably mounted means together as a unit for movement in a contacts-closing direction; said abutment aosavve engageable with and for latching said manually operable means in a contacts-closed position when the latter is latched to said movably mounted means by said thermally responsive means; and biasing means compressively urging said mechanical latching means into engagement with said manually operable means .in the contacts-closed position thereof.

6. In combination; a pair of electrical contacts; resetting means comprising two members; resilient means compressively biasing said two members apart; thermally responsive means operatively connected for movement to open and close said contacts; resilient means compressively biasing said thermally responsive means for movement from contacts-closed to contacts-open position; one of said two members being movable from retracted position to reset position for moving the other of said two members against a portion of the thermally responsive means thereby moving the latter to contacts-closed position and compressing said second-named resilient biasing means; mechanical latch means engageablewith said one member for retaining said one member'in reset position, said second-named biasing means also compressively biasing said mechanical latch means into engagement with said one member when the latter is moved to the reset position, said thermally responsive means being responsive to temperature change for moving said portion thereof out of engagement with said other of said two mem bers thereby permitting movement of the thermally responsive means to contacts-open position under the bias of said second-named biasing means.

7. In combination; a housing; a pair of electrical contacts in said housing; manually operable resetting means; thermally responsive means operatively connected for movement to open and close said contacts; compressive resilient means biasing said thermally responsive means for movement from a contacts-closed to a contacts-open position, said manually operable resetting means being movable from a retracted position to a reset position into engagement with said thermally responsive means to move the latter to a contacts-closed position and compress said resilient biasing means; mechanical latch means for retaining said manually operable resetting means in reset position, said latch means comprising a detent surcfiace on said manually operable resetting means engageable with ball means mounted for movement into and out of engagement with said detent surface; latch means mounted :for movement relative to said ball means and manually operable resetting means, said resilient means also biasing said latch means into engagement with said ball means to move the latter into and maintain the same in engagement with said detent surface whereby to retain said manually operable reset means in the reset position.

8. The combination as set forth in claim 7 and wherein said mechanical latch means is disposed in a recess provided by said housing.

9. In combination;-a housing; a pair of electrical contacts in said housing; manually operable resetting means; a thermally responsive member operatively connected for movement to open and close said contacts; compressive resilient means biasing said thermally responsive means for movement from a contacts-closed to a contacts-open position, said manually operable resetting means being movable from a retracted position to a reset position into engagement with said thermally responsive means to move the latter to a contacts-closed position and compress said resilient biasing means; mechanical latch means for retaining said manually operable resetting means in reset position, said latch means comprising a detent surface on said manually operable resetting means; ball means mounted for movement into and out of engagement with said detent surface; latch means mounted for movement relative to said ball means and manually operable reset tingmeans, said resilient means also biasing said latch means into engagement with said ball means to move the latter into and maintain the same in engagement with said detent surface whereby to retain said manually operable reset means in the reset position; second resilient means biasing saidmanually operable reset means for movement from reset position to retracted position, said thermally responsive means being responsive to temperature change for moving out of engagement with said manually operable resetting means to thereby permit movement of said thermally responsive means to a contacts-open position under the bias of said first-named biasing means.

10. An electrical switch comprising a base; contact means on said base; thermally responsive means operatively connected for movement to open and close said contact means; a first means compressively biasing said thermally responsive means for movement from a contacts-closed to a contacts-open position; manually operable resetting means comprising two members; resilient means compressively biasing said two members apart, one of said two members being movable from retracted to reset position for moving the other of said two members into engagement with said thermally responsive means to move the latter to a contacts-closed position and compress said first-named biasing means; further resilient means compressively biasing said one member from a reset position to a retracted position; mechanical latch means for'reball means to urge the latter into latching engagement with said latching surface, said first-named resilient means compressively biasing said latch member into engagement with said ball means when said thermally responsive means is moved to the contacts-closed position.

11. An electrical switch comprising a base; contact means on said base; movably mounted means carrying movable contact means for engagement with said firstnamed contact means; manually operable means mounted in said switch for movement relative to said movably mounted means; thermally responsive means engageable with abutment means on said manually operable means for latching said manually operable means and said movably mounted means together as a unit for movement in a contacts-closing direction; compressive biasing means urging said movably mounted means in a contacts-open ing direction; mechanical latching means for latching said manually operable means in a contacts-closed position when the latter is latched to said movably mounted means by said thermally responsive means, said mechanical latching means comprising detent surfaces on said manually operable means; detent means supported on said base for movement into and out of engagement with said detent surfaces; a latch member movablymounted with respect to said manually operable means and engageable with said detent means for moving the latter into latching engagement with said detent surfaces, said biasing means also urging said latch member into, and maintaining the same in, engagement with said detent means in the contacts-closed position thereof, said detent means comprising a plurality of balls and said movably mounted latch member being slidably mounted and comprising a latch ring having a wedge surface engageable with said balls. I

12. In combination; a housing; a pair of electrical contacts in said housing; manually operable resetting means; thermallyresponsive means operatively connected for ball means mounted for movement into and out of engagement with said detent surface; latch means mounted for movement relative to said ball means and manually operable resetting means, said resilient means also compressively biasing said latch means into engagement with said ball means to move the latter into and maintain the same in engagement with said detent surface whereby to retain said manually operable reset means in the reset position;

said detent surface comprising a peripherally extending groove on said resetting means; latch means comprising a latching ring slidably mounted with respect to said ball means and to said manually operable resetting means, said latch ring having a wedge surface engageable with said ball means for moving the latter into engagement with said peripherally extending groove under the bias of said resilient biasing means to latch said manually operable resetting means in the reset position.

13 In combination; a housing; a pair of electrical contacts in said housing; manually operable resetting means; a thermally responsive member operatively connected formovement to open and close said contacts; resilient means compressively biasing said thermally responsive means for movement from a contacts-closed to a contactsopen position, said manually operable resetting means being movable from a retracted position to a reset position into engagement with said thermally responsive means to move the latter to a contacts-closed position and compress said resilient biasing means; mechanical latch means for retaining said manually operable resetting means in a reset position, said latch means comprising a detent surface on said manually operable resetting means; ball means mounted for movement in and out of engagement with said detent surface; latch means mounted for movement relative to said ball means and manually operable resetting means, said resilient means also compressively biasing said latch means into engagement with said ball 7 means to move the latter into and maintain the same in engagement with said detent surface whereby to retain saidmanually operable reset means in the reset position; second resilient means compressively biasing said manually operable reset means for movement from reset position to retracted position, said thermally responsive means being responsive to temperature change for moving out of engagement with said manually operable resetting means to thereby permit movement of said thermally responsive means to a contacts-open position under the bias of said first-named biasing means; said detent surface comprising a peripherally extending groove on said resetting means; latch means comprising a latching ringslidably mounted with respect to said ball means and to said manually operable resetting means, said latch ring having a wedge surface engageable with said ball means for moving the latter into engagement with said peripherally extending groove under the bias of said first-named resilient biasing means to latch said manually operable resetting means in the reset position.

14. An electrical switch comprising a base; contactaoaavve of said two members being movable from retracted to reset position for moving the other of said two members into engagement with said thermally responsive means to move the latter to a contacts-closed position and compress said first-named biasing means; further resilient means compressively biasing said one member from a reset position to a retracted position; mechanical latch means for retaining said one member in reset position when said other member is in engagement with said thermally responsive means and the latter is in the contacts-closed position, said latch means comprising a peripherally extendinglatohing surface on said one member; ball means mounted on said base for movement into and out of engagement with said latching surface; a latch member movably mounted on said base with respect to said ball means, said latch member having a wedge surface engageable with said ball means to urge the latter into latching engagement with said latching surface, said first-named resilient means compressively biasing said latch member into engagement with said ball means when said thermally responsive means is moved to the contactsclosed position; and said movably mounted latch member comprising a slidably mounted latching ring.

15. An electrical switch comprising a base; contact means on said base; movably mounted means carrying movable contact means for engagement with said firstnamed contact means; manually operable means mounted on said switch for reciprocal movement relative to said movably mounted means; thermally responsive means engageable with abutment means on said manually operable means for latching said manually operable means and said movably mounted means together as a unit for movement in a contacts-closing direction; said abutment means being slidably mounted on said manually operable means; spring means urging said abutment means for movement relative to said manually operable means in a contacts-closed direction; mechanical latching means engageable with and for latching said manually operable means in a contacts-closed position when the iatter is latched to said movably mounted means by said thermally responsive means; biasing means intermediate said thermally-responsive means and mechanical latching means compressively urging said mechanical latching means into engagement with said manually operable means in the contacts-closed position thereof, and also compressively iii-3 urging said thermally responsive means for movement in a contacts-opening direction.

16. The electrical switch as set forth in claim 10 and wherein said latch member is mounted for slidable movement with respect to said one member and said ball means.

17. In combination: a housing; a pair of electrical contacts in said housing; manually operable resetting means; thermally responsive means operatively connected for movement to open and close said contacts; resilient means compressivel'y biasing said thermally responsive means for movement from a contacts-closed to a contacts-open position, said manually operable resetting means being movable from a retracted position to a reset position into engagement with said thermally responsive means to move the latter to a contacts-closed position and compress said resilient biasing means; mechanical latch means for retaining said manually operable resetting means in reset position, said latch means comprising a detent surface on said manually operable resetting means engageable with ball means mounted for movement into and out of engagement with said detent surface; latch means mounted for movement relative to said ball means and manually operable resetting means, said resilient means also compressively biasing said latch means into engagement with said ball means to move the latter into and maintain the same in engagement with said detent surface whereby to retain said manually operable reset means in the reset position; and said latch means being slidably mounted in said casing for movement relative to said ball means and manually operable resetting means.

References Cited in the file of this patent I UNITED STATES PATENTS 2,156,761 Jackson May 2, 1939 2,187,606 Jackson et al Jan. 16, 1940 2,633,515 Locher Mar. 31, 1953 2,668,886 Ingwersen 'Feb. 9, 1954 2,798,920 Ingwersen July9, 1957 2,816,192 Ingwersen Dec. 10, 1957 2,828,385 Malone Mar. 25, 1958 2,831,086 *Ing'wersen et a1 Apr. 15, 1958 2,833,888 Bessiere May 6, 1958 2,838,635 Ingwersen June 10, 1958. 2,839,638 Epstein June 17, 1958