US2747053A - Circuit breaker - Google Patents

Description

May 22, 1956 R. E. LocHER 2,747,053

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a y HIS A Woe/ways United States Patent CIRCUIT BREAKER Ross E. Locher, San Marino, Calif., assignor to Zinsco Electrical Products, Los Angeles, Calif., a corporation of California Application April 2, 1953, Serial No. 346,359 18 Claims. (Cl. 200-116) This invention relates to an electric switch and more particularly to an electric switch of the automatic circuitbreaker type which may be deiined as a device through which an electric current is passed and which opens the circuit automatically to interrupt the circuit whenever predetermined conditions occur in the circuit. The invention also relates to an automatic circuit breaker which is capable of manual operation to interrupt the circuit.

The invention further relates to a device by which the circuit is interrupted whenever the current in the circuit increases to a predetermined or overload value so that it becomes desirable to open the circuit; and further relates to a device that is adjustable so as to interrupt the circuit at preselected current values.

The invention also relates to an overload circuit breaker or interrupter which includes a thermostatic element and a latch therefor, the thermostatic element forming a part of the breaker which when heated above a predetermined temperature is instrumental in interrupting the circuit.

The circuit breaker of the present invention, while structurally adaptable in size and electrical rating to suit practically any installation, is particularly adaptable for installations requiring a compact unitary unit that is exceptionally light in weight, as, for example, installations required in aircraft where size and weight are mandatory considerations as well as functionality of the unit. It is an object of the present invention, therefore, to provide a circuit breaker having the above-mentioned characteristics.

it is another object of this invention to provide an improved electrical switch of the class described in which manual means are provided for closing the switch and opening the switch, the manual means being inoperative to maintain the switch closed when the thermostatic element is heated to a predetermined overload state.

It is another object to provide an improved overload circuit breaker providing overload protection in the form of a thermostatic element, the arrangement of components in association with the thermostatic element providing a breaker that is capable of opening with exceptional rapidity.

A further object of the invention is to provide an improved electrical switch having a latch mechanism that is actuable both thermally and manually.

A further object of the invention is to provide a circuit breaker having components that assume a first predeteriined position when the circuit is completed and a second predetermined position when the circuit is interrupted thereby obviating the necessity of manually resetting the breaker subsequent to a thermally actuated interruption and prior to a manual closing thereof.

A still further object of the invention is to provide an improved circuit breaker with means to permit the mov ing components to become relatively free during a circuit interruption cycle to permit the components to move rapidly under the influence of yieldable means to further increase the rapidity of circuit interruption.

An additional object of the invention is to provide 2 means in a circuit breaker to permit the moving circuit interrupting elements to gain considerable momentum prior to circuit interruption to further increase the rapidity of circuit interruption.

An additional object is to provide a relatively simple electric switch of the class described with a manual means to interrupt the circuit by moving the actuator in one direction, movement in the opposite direction being inoperative to interrupt the circuit.

Another object of the invention is to provide a circuit breaker having unitary yieldable means to bias the switch member in a circuit closed position and to serve as a biasing element to urge the components toward a circuit open position upon interruption of the circuit.

The invention also has for its objects to provide means in an electric switch of the class described that are positive in operation, convenient in use, easily installed in working position and easily disconnected therefrom, economical of manufacture, relatively simple, and of general superiority and serviceability.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. However, the drawings merely show and the following description merely describes a preferred embodiment and certain modifications of the present invention, which are given by way of illustration or example only.

In the drawings, like reference characters designate similar parts in the several views, in which:

Fig. l is a front elevational view, partially in section and in phantom, of the circuit interrupter of the present invention with the housing partially removed and taken along the line 1-1 of Fig. 5, showing the internal Working parts thereof in a circuit open position;

Fig. 2 is a rear elevational view of the circuit interrupter of Fig. l taken along the line 2-2 of Fig. 5 and illustrating the parts in a circuit open position;

Fig. 3 is a front elevational view, partially in section, taken along the same line 1 1 as Fig. 1 but illustrating the internal working parts in an intermediate position;

Fig. 4 is a rear elevational view taken along the same line 22 as Fig. 2, and illustrating the working parts in an intermediate position;

Fig. 5 is a side elevational view of the circuit interrupter, slightly reduced in scale, showing the housing and external components thereof;

Fig. 6 is a front elevational view similar to Fig. 3 showing the working parts in the circuit closed position;

Fig. 7 is a rear elevational View of the circuit interrupter of Fig. 6 showing the working parts in the circuit closed position, and illustrating in phantom one of the positions that may be assumed by the elements of the actuator;

Fig. 8 is a sectional view through the top of the circuit interrupter taken along the line 8 3 of Fig. 6;

Fig. 9 is a sectional view through the bottom of the circuit interrupter taken along the line 9-9 of Fig. 6;

Fig. l0 is a vertical sectional view taken along the line 10*10 of Fig. 6;

Fig. ll is a partial sectional view, slightly enlarged, taken along the line 11-11 of Fig. 6, and illustrating a means for Calibrating the device;

Fig. l2 is a partial view of Fig. l0 taken along the line 1212 thereof;

i Fig. 13 is a partial rear elevational View of the circuit interrupter, slightly enlarged and partially in section, il-` lustrating a modification of the actuator and cooperating elements;

Fig. 14 is a view similar to Fig. 13 but illustrating the actuator components in an intermediate position; and

ancianas Fig. is a view taken along the line 15--15 of Fig. 13.

In the embodiment of the invention shown in the drawings the circuit interupter is provided with a case or housing 20, the housing comprising a frame 21 and a cover 22 preferably formed of a material having good dielectric characteristics, and a closing top plate 23 having a pair of legs 24 depending therefrom and adapted to be received between the frame and the cover. The three housing elements above mentioned are integrated by screws or rivets 25 or other suitable means, the rivets adjacent the upper portion of thehousing passing through apertures 27 provided in the legs 24j of the top plate 23 so as to rigidly secureithel three housing elements together. A first terminal member 29 and a second terminal member 3@ that constitute load or line terminals, as the case may be, for the device aremolded or inserted in and project from a bottom wall 31 of the housing. Screws 32,' 33 are provided on theV projecting extremities ofthe terminals for connection of wires from an external circuit. Continuity of the external circuit will be maintained through the circuit breaker as long as it is in the closed position, and will be interrupted when the circuit breaker is moved to the circuit open position, whether manually moved or whether automatically moved due to an overload in the circuit.

Disposed within the housing is a slide member which is mounted for reciprocal translation therein between an upper position, a lower position, and an extreme lower position as will hereinafter be understood. The slide is preferably formed of a material having good dielectric characteristics and in the embodiment shown is irregularly shaped but reasonably planar so as to be definable as lying in and being translatable in a vertical plane. The housing is provided with suitable guides for accommodating vertical translation of the slide. For example: the frame 21 is provided with a grooved rail 37, as best seen in Figs. 6, 8 and 9, extending' substantially the height of the frame and adapted to receive a tongue 33 or a spaced plurality thereof, extending from the slide along a vertical edgeY thereof; the frame is provided-with a raised boss 39, as best seen in Figs. 6, 7 and 8, extending downwardly ofthe top of the housing` for slidable engagement with a surface of the slide generally indicated by a numeral 40; the framev is provided with a raised elongate boss 41, as best seen in Figs. 6 and 9, extending upwardly of the bottom of the housing for slidable engagement with a laterally projecting leg 42 of the slide. Effectively, therefore, the frame 21 provides three generally parallel surfaces constituting a vertical line guide support and two remotely disposed surfaces providing a three-point buttress for the slide in any vertical position. The opposite side of the slide 35 is guided by a raised elongate boss 43 extending inwardly from the cover 22, as best seen in Fig. 8, and which slidably engages a surface of the slide generally indicated by the numeral 44, the surface 44 being parallel to the guide surfaces of the frame above described. The boss 43 extends downwardly of the top of the housing so as to be in abutment with the surface 44 at all positions of translation of the slide but terminates at a point slightly below the area of abutment when the slide is in the extreme lower position. There is no guide for the slide provided by the cover 22, other than above mentioned, excepting, however, that a spring means is provided intermediate the cover and the slide to urge the last-mentioned member into abutment with the three-point buttress of the frame 2l as will hereinafter be explained.

Pivotally mounted to the slide member 35 is .a switch arm 47 which in the illustration shown is generally Y- shaped comprising a pair of segments, 48, 49 and a portion 50, the portion having secured to its extremity a contact 51. The arm is provided with a shaft 54 (as best seen `in Figs. l0 and 12) having a slightly enlarged diarneter'indicate'd by the numeral S5 which is receivable within a passage 56 in the slide 35. The slide is provided with a shoulder 58, adjacent to the passage, providing a concave surface 57 extending substantially parallcl to the passage. The surface 57 is illustrated as a half cylinder of revolution which constitutes an extension of the lower half of the pesage 56. The shoulder 58 provides, therefore, a concave buttress to receive a part of the shaft 54 extending outwardly and to the right of the passage as viewed in Fig. 10. It is to be noted that the diameter of the enlarged diameter portion of the shaft is slightly less than'the diameter of the passage 56. For a circuit breaker having a scale size corresponding to Figs. l and l0 an examplary clearance value between the passage and the shaft would be on the order of 0.006 inch. This clearance provides a means'whereby the shaft may wobble or rock with respect to the slide as well as rotate with respect thereto. While the shoulder 58 is illustrated as forming a half cylindrical surface, it is contemplated that it may partake of any suitable form so long as it provides a buttress-to relatively minimize rocking or wobbling of the shaft in a clockwise direction as viewed in Fig. Al0.

The switch arm 47 is preferably formed of rigid metallic and conductivef material, the portion 50 thereof forminga part Vof the current-conducting components of the breaker. Secured to the switch arm and in conductive relation with the portion 5,0 is a thermostatic element 62 extending substantially radially of the shaft 54 and substantially parallel to a plane common to the switch arm segments 48, 49. The thermostatic element is illustrated as forming a part of the switchV arm for integral movement therewith and having an aperture Ytherethrough at onewend thereof to receive the shaft 5 4. The element may be firmly abutted against and secured as by welding or brazing to the switch arm. The thermostatic element sol secured extends in a cantilever manner outwardly of the axis of the shaft 54 terminating at the unsecured end which constitutes an engaging portion 65, the function of which will be hereinafter explained.

Slidably receivable on the shaft 54 is a bushing 67 which is adapted to abut against the thermostatic element. The bushing is provided withl a counterbore 68 partially l therethrough and concentric with the bushing aperture so as to receive a resilient means 69 illustrated in the form of a compression spring. The spring surrounds the end of the shaft 54 and is compressed intermediate the bushing andk the cover 22 of the breaker housing 2t) and serves to yieldably urge the switch arm 47 into abutment with the slide 35. As hereinbefore referred to, a spring means is provided intermediate the cover 22 and the slide 35 to urge the slide into abutment with the three-point buttress of the frame 21.V The spring 69 accomplishes this function. As the spring is positioned between the cover and bushing, vertical translation of the slide 35 whichnecessarily initiates vertical translation therewith of the thermostatic element, the switch arm and the shaft therefor causes the spring 69 to slidably engage with the cover 22, the surface of the cover being. substantially parallel to the plane-of translation of the. slide so as to maintain the lateral force exerted by the spring at a constant value.

As kthe switch arm 47 is urged into abutment with and pivotally mounted to the slide, the slide is provided with a bearingsurface 72, as best seen in Fig. 3, for abutment and slidable engagement with the segments 43, 49 of theswitch arm. Forming a part of the surface 72 is an end portion 73 of a screw 74 (see Figs. 6, 9 and ll) which is threaded through the-slide 35'. Adjustment ofthe screwfin either direction provides a means whereby the contour of the surface .72' at the point of projectionV of the screw through the slidemay be raised ory lowered. Thisconstitutes `an adjustable or calibrating means for positioning the thermostatic, element 62 when the breaker is in the circuit closed position whereby automatic tripping of the breaker may be set to occur at a predetermined overload current. The provision of the surface above mentioned in combination with the switch arm segments provides one of the novel characteristics of the circuit breaker as will hereinafter I.be understood. As calibration is rather critical, it is necessary that the screw 74 be restrained from rotation. Accordingly, the screw is provided with a resilient wire clip 75 (see Figs. 4 and ll) having a portion snugly engaging its neck, the extended part of the clip being disposed intermediate a pair of closely spaced upstanding studs 76 provided by a slide.

It will now be understood that the switch arm 47 is adapted to pivot with respect to the slide. The arc of movement of the ann may be defined as between a released position and a latched position, the released position being illustrated in Fig. l and the latched position being illustrated in Fig. 3 or 4. The arm is biased at Iall times toward the released position byva resilient means or tension spring 78 which is connected at one end to a notched post 79 carried by the frame 21 and at the other end to a notched ear 81 projecting from the switch arm 47.

Referring to Figs. l and 3, clockwise rotary movement of the arm 47 is limited by contact of the segment 49 thereof with an angularly disposed curb 82 provided by and forming a part of the slide 35. When the slide is translated downwardly the switch arm portion 50 moves downwardly and into engagement with a raised boss 84 which is molded integral with the frame 21 causing the arm to rotate in counterclockwise direction until it assumes the latched position as illustrated in Fig. 3. During swinging movement of the arm the end or engaging portion 65 of the thermostatic element 62 traverses an arc with respect tothe slide, passing over and being progressively lifted by a rst raised wedge member 85 (see Figs. 3 and 8) formed integrally with the slide, and by a second wedge member 86 preferably made of machine steel and rigidly secured to the slide, until the portion 65 of the thermostatic element completely passes the wedge member 86 whereupon the portion 65 may drop behind the wedge and assume a latched position as illustrated in Fig. 3. The wedge member 86 may be appropriately dened as a latching portion t'or the thermostatic element.

It is to be recognized that the slide member is capable of a slightly additional downward movement from the position shown in Fig.` 3 and accordingly the switch arm 47 is capable of further counterclockwise motion. This is provided as a suiicient tolerance to assure traversal of the thermostatic elementV throughout a sufficient arc to cause the arm to reach the latched position. The position of the slide as illustrated in Fig. 3 or the position of the slide slightly below the position as illustrated in Fig. 3, as hereinabove referred to, may be appropriately delined as the extreme lower position of the slide member.

Referring to Figs. l and 3, the multiple function of the spring 78 may be readily understood. irrespective of the position of the slide 35 or the switch arm 47, the spring 73 at all times serves to bias the switch arm toward the released position and to bias the slide toward the upper position, both such positions being illustrated in Fig. l. An additional function of the spring 78 is to effect a force substantially normal to the axis of the shaft 54 when `the switch arm is in the latched position. The latched position of the switch arm being illustrated in Figs. 3 and 6, the spring 73 is seen to circumferentially embrace a portion of the outer periphery of the bushing 67. A force is applied to the bushing which is transmitted to the end of the shaft 54 for rockably urging the arm and the thermostatic element with respect to the slide. plication of the force to the shaft as shown in the drawings are such as to tend to urge the thermostatic element out of engagement with the latching portion 86, it is Although the direction and eifective point of ap-l amines contemplated that the force may be applied inY any direction to rockably urge the shaft and components integral therewith so as to effectively tighten the switch arm and thermostatic element with respect to the yslide and the latching portion thereof. lt is desirous to have the tightening action effective when the switch arm is in the latched position which provides a means for accommodating a closer calibration for the device. In combination with the effect of the spring 69, the spring 78 is instrumental in precisely positioning the engaging portion 65 of the thermostatic element in position with respect to the latching portion 86 of the slide member.

The tightening action above mentioned is desired when the switch arm is in the latched position, the relation of the components being so arranged that when the circuit breaker moves from a circuit closed condition (see Fig. 6) to a circuit open conditions (see Fig. l) the force applied by the spring 78 to the shaft 54 is relieved thereby .permitting the slide and switch arm 47 to more freely move to the upper and released positions, respectively. It may now be understood that the relieving of the tightening action permits the parts to move more rapidly under the biasing iniluence of the spring 78 to cause the breaker to translate to a circuit open condition with relatively great rapidity. Effectively, therefore, there is provided a means to tighten the moving parts above mentioned when the breaker is in the circuit closed condition to satisfy close calibration requirements as well as a provision to release the tension to aid the breaker in performing a rapid transposition to a circuit open position.

When the breaker is in the circuit closed position as illustrated in Fig. 6, the thermostatic element 62 and the switch arm portion 50 constitute two of the currentconducting components completing the circuit to the terminals 29 and 30. Intermediate the terminal 29 and.

the thermostatic element 62 is a conductive member 90 illustrated in the form of a flexible cable having its ends suitably attached as by brazing or soldering to the terminal 29 as indicated by the numeral 91, and to thethermostatic element 62 as indicated by the numeral 92. As the end 65 of the thermostatic element moves with respect to the breaker housing, the cable 90 is caused to Hex but is maintained suiciently clear of the moving parts due to its passage around the side of the slide and above the projecting leg 42 thereof, the leg extending laterally of the slide and sufficiently close to the side of the frame 21 so as to preclude the cable from passing therebetween. Although the conductive member 90 is illustrated as exible in form, it is contemplated that it may partake of any suitable form so long as a continuous current-conducting circuit is maintained between the terminal 29 and the thermostatic element 62.

Completing the circuit to the other terminal 30 is a Contact 94 which is suitably positioned in the housing so as to engage with the contact 51 when the switch arm is displaced toward the latched position. The contacts 51 and 94 constitute the interrupting contacts of the breaker. Accordingly a permanent magnet 95 of generally U-shaped configuration is mounted horizontally by the housing and disposed about the point of engagement of the contacts and functions in the usual manner as a magnetic blowout means to aid in extinguishing of a current arc between the contacts. The contact 94 is rigidly secured to a bracket 96 which, as illustrated in the drawings, constitutes an extension of the terminal 30, the bracket including a substantially vertical leg 97 and an offset portion 98. The last-mentioned portion provides a means to mount and position the contact 94 in a stationary position with relation to the housing being so located as to intercept the switch arm portion mounting the contact 51 when the switch arm 47 is displaced toward the latched position or moves upwardly as determined by upward movement of the slide 35.

of the bracket 96 restrains upward movement of the As the portion 98 7 switch arm 47 and the slide 35 when the device is in the circuit closed position, a rib 99 is provided by the frame'21 to reinforceV as well as positively position the portion 98.

AReferring to Figs. 6 and 9 the magnet j95 may be mounted in any suitable manner in the position illustrated. As shown, however, it may be retained by an adhesive 101 intermediate the side of one of the legs of the magnet and the frame 21, the end of the leg abutting a portion 102 of the frame. To electrically insulate the magnet from the bracket 96 a sheet of insulating paper 104 may be disposed therebetween.

In order that the slide member may be manually translated an actuator means is provided which is normally engageable with the slide to provide a rigid connection to translate the slide downwardly. A characteristic of the actuator means is that it is releasably engageable with the slide member through the medium of a linkage means so as to interrupt the rigid connection when the slide has moved downwardly a predetermined distance. Constituting the actuator means in the embodiment illustrated, and as best seen in Figs. 2 and 10, is a plunger member -and a toggle connected thereto comprising a pair of pivotally connected links 111 and 112. The lactuator means is carried by the slide member 35, the plunger portion extending upwardly and outwardly of the housing into position for manipulation by an operator. The uppermost extremity of the plunger mounts a tubular button or cap 113 which is threaded onto the uppermost I end of a vertical stem 114 of a generally L-shaped arm 115. A washer 116 (see Fig. 1) may also be provided about the threads intermediate the button and a shoulder 117 provided by the stem 114 to assure relative rigidity ofthe button 113 and the arm 115.

The stern `114 extends downwardly and through a cylindrical bushing 129 provided by the slide 35. The stem has a Vfree sliding t with respect to the bushing and is reciprocable therein. As the stem may move with respect to the slide the button 113 is counterbored on the under side to provide a chamber 121 to receive the upper portion of the bushing.

The lower end of the arm is provided with a laterally offset shank 122, as best seen in Fig. 10, to the end of which is pivotally secured the upper portion of the link 111. The lower extremity of the link 111 is pivotally secured to an intermediate extremity of the link 112 as by a rivet 124 or other suitable means passing through apertures in the links. The ends of the rivet may be appropriately rolled over to provide flanged ends 125 to retain the links in joined relationship. tremity of the link 112 is pivotally secured to the end of the enlarged diameter portion 55 of the shaft 54.

Referring to Figs. 2, 4 and 10 the toggle is shown as providing a rigid connection intermediate the button 113 and the enlarged diameter portion 55 of the shaft 54. Urging the links 111 and 112 into rigid relationship is a coil spring 128. One end of the spring is secured to an offset nose 129 projecting from the link 112, the other end being suitably secured to the slide 35 as indicated by the numeral 13G. Accordingly, the spring urges the toggle Ainsuch Va manner as to move the rivet 124 to the left as viewed in Figs. 2 and 4. Further movement Vof the toggle in the direction above mentioned is restrained by engagement of an offset lip 132 provided at the end of an extension 133 of the link 112, the lip engaging a portion of the link 111 intermediate its ends. in a preferable construction the engagement or locking of the links is designed to occur when the toggle is siightiy over center, that is, when the longitudinal axis of the rivet 124 is slightly to the left of a line intersecting and normal to the axes of the shaft 54 and the shank 122.

Forming a part of 'the link 112 is an angularly disposed arm 134 providing a means to secure one end of a compression 'spring 135. The opposite end of the spring is Ysuitably groundV off and formed to provide a surface The lower exfor abutment witha boss,13,6 formed integrally with the housing. The spring is `retained in position `by astop stud 137 extending centrally of the coils of Vthe spring. The stud is comprised of a threaded portion 139 and a reduced diameter portion 14,0, the threaded portion being received in a tapped hole 141 in the bottom wall of the frame21 and extending through the boss 136. A slot 142 is provided in the head of the threaded portion to receive a screw driver whereby the stud may be adjusted vertically with respect to the housing. Accordingly the stud may be appropriately positioned with respect to the housing to provide an adjustable tripping means to cause release of the actuator and the slide member as will hereinafter be understood. The uppermost end of the reduced diameter portion of the stud 137 is adapted to engage with the arm 134, and, as best seen in Fig. 4, when the link 112 moves downwardly so as to cause the arm 134 to engage the stud a moment is provided so as to urge the link 112 to move in a clockwise direction thereby causing the toggle to pass over center to collapse or break the rigid connection of the links 111and 112.

Referring to Fig. 3, the top plate 23 is provided with an opening defined by an annular ring 144 formed integrally with the plate. The upper extremity of the ring terminates in a circumferential surface 145 which is adapted to engage with 'a shoulder 146 forming a part of the button 113. in a depressed position of the button 113 as is shown in Fig. 3 the lower extremity thereof may be seen as contacting a sheet of material 148 disposed intermediate the under side of the top plate 23 and the frame 21 and cover 22. The sheet is preferably flexible, for example, made of rubber, and of a nature to provide a gasket between the adjacent parts. A hole is provided in the sheet to pernn't the bushing 121) of the slide to extend therethrough, the hole being of such a diameter as to eiiect a seal about the bushing to prevent entrance of foreign materials inside the housing. The sheet has an area substantially conforming with the area of the under side of the top plate. As seen in Fig. l, wherein the slide is illustrated in its upper position, two abutment surfaces 150 of the slide contact the sheet 148. Thus there is provided a means to cushion the upward movement of the slide when it reaches the upper position.

Figs. 13, 14 and l5 illustrate a modification of the actuator and the toggle. Figs. 13 and 15 are illustrative of the circuit open position with the slide 35 in the upper position and Fig. 14 is illustrative of the circuit closed position with the slide 35 in the lower position. All elements that are similar to the structure previously described are similarly numbered. It is to be noted, however, that the spring 13S is not included in the modiiication.

Referring `to Figs. 13-15, a latching arm 155, preferably made of an elongate length of metallic strip material, is secured at one end to the frame 21 as by a securing means illustrated in the form of a rivet 156. The arm is mounted as a cantilever and extends downwardly in the housing terminating at a point adjacent the lower extremity of the slide 35 when the siide is in the upper position. The arm is provided with a deformation across its width and intermediate its ends comprising an angularly offset cam 158 which is joined at each end to an upper portion 159 and a lower portion 160, respectively, of the arm. The portions 159 and 169 occupy planes which are substantially parallel to each other.

The link 111 is the same as heretofore described but includes in the modification a projection 162 extending substantially laterally of the axis of the rivet 124. The end of the projection is provided with an offset nose 163 which is adapted for engagement with thc latching arm 155. The nose 163, as best seen in Fig. l5, while being adapted to engage with the under side of the arm is also adapted to engage with Vthe side edge of the cam as indicated by the numeral 164 (see Fig. 14). To accommodate the two phases of engagement the nose 163 is 9 fabricated at' one end to have an inclined engaging surface 166 disposed for surface abutment with the cam 158, and at the other end to have a surface 167 extending substantially upright of the plane of the projection 162 of the link 111 and terminating at a tip indicated by the numeral 168.

The coil spring 128 urges the links 111 and 112 into the rigid relationship as hereinbefore described. When the elements are in the position illustrated in Figs. 13 and 15, the nose 163 is disposed opposite the upper portion 159 of the ann 155 and preferably out of engagement therewith as shown. However, when the elements are in the position as illustrated in Fig. 14 the toggle cornprising the links 111 and 112 which are being urged toward an overcenter position under the influence of the spring 128 are restrained by engagement of the surface 167 of the nose 163 with the side edge 164 of the cam 158. The position of the cooperating elements is predetermined so that when the toggle assumes a position as in Fig. 14, the disposition of the tip 168 with respect to the plane of the cam 158 is relatively closed. As the arm 155 is relatively resilient and cantilever-mounted, under the inuence of an external force it will bend about its cantilever mount. An external force applied to the arm 155 is a component of the force applied by the spring 128 through the links which urges the nose 163 into engagement with the side edge 164 of the cam 158. The design tension of the spring 128 is insufficient, however, t0 cause the surface 167 to forcibly displace the ann 155 upwardly, as viewed in Fig. 14, to permit the tip 168 to pass underneath the arm 155. Manual operation, however, is suiicient to cause such movement which will be hereinafter described.

peraton Figs. 1 and 2 of the drawings illustrate the circuit breaker in a circuit open position wherein the slide member 35 is in its upper position and the switch arm 47 is in the released position. To complete an external circuit that may be connected to the terminals 29, 30 the operator need only depress the button 113. A downward force is transmitted through the arm 115 to the links 111 and 112 which are in overcenter and rigid relationship, and to the end of the enlarged diameter portion 55 of the shaft 54. Under the influence of the force the shaft 54 will rock to a relatively slight degree to a limit as determined by the shoulder 58 in its particular relation to the passage 56. The force is therefore transmitted to the slide 35 for translating it downwardly toward an extreme lower position as is illustrated in Fig. 3. During progressive movement of the slide from its position in Fig. l to that of Fig. 3, the portion 50 of the switch arm 47 engages the housing boss 84 so as to displace the switch arm toward its latched position as is illustrated in Fig. 3. Further, during this movement the spring 78 is being increasingly tensioned to ultimately embrace the bushing 67 about a portion of its periphery to effect a substantially radial force upon the shaft 54 which, as heretofore explained, tightens the switch arm in relation to the slide.

The thermostatic element 62 extends in a plane substantially parallel to the plane at the segments 48, 49 of the switch arm 47 and also in a plane substantially parallel to the plane of the surface 72 of the slide. When the thermostatic element is cold the end or engaging portion 65 thereof lies relatively close to the surface 72 so as to be in a position to latch-engage behind the latching portion 86 of the slide. When the thermostatic element isv heated, however, the end 65 eXes away from the surface 72. Prior to closing of the breaker the thermostatic element is normally cold and as the end 65 progresses along the arc from the position of Fig. 1 to that of Fig. 3 the wedge 85 and the latching portion 86 lift the end 65 away from the surface 72 (see Fig. 11) until the end 65 passes the latching portion 86 whereupon the end may drop behind the latching por'- tion. The thermostatic element is urged into the position behind` the latching portion due to the force of the spring 69 as applied to it and the switch arm 47.

As a thermostatic element is usually comprised of a pair of metallic strips of dissimilar coefficients of expansion and the thickness of the strips may vary depending upon the thermal characteristics desired, the thermostatic elment may be relatively flexible or rigid. If .lt it is exible, it may bend about its cantilever joinder to the switch arm as it progresses from the position of Fig. l to that of Fig. 3, the segments 48, 49 of the arm remaining in Contact and slidable with respect to the surface 72. lf, however, the design requires a relatively rigid thermostatic element, the traversal of the element is accomplished as above described, but the segments 48, 49 may also raise slightly from the surface 72. This condition may be observed in Fig. ll wherein the full lines represent the thermostatic element 62 and the segment 49 when the switch arm is in the latched position, the phantom lines illustrating the position of these components when the end of the thermostatic element is in the uppermost position on the latching portion S6. lt is recognized that the segments may be so raised due to the slight amount of wobble or rocking movement of the shaft 54 with respect to the passage 56. Further, the shaft 54- is so constructed and arranged with respect to the slide that it may partake of a slight lateral movement with respect to the slide. Accordingly, depending upon the rigidity of the thermostatic element, the shaft 54 may move laterally, for example, as to the left as viewed in Fig. 10 and against compressive reactive force of the spring 69. It is to be understood, therefore, that the circuit breaker is adaptable to include thermostatic elements of a variety of thermal characteristics having various degrees of rigidity or exibility without necessitating a change in the basic structure of the device. Further, it is to be understood in this connection that one or both of the segments 4S, 49 may be continuously or intermittently in abutment and slidable engagement with the surface 72 depending upon the characteristics of the thermostatic element.

Referring to Fig. ll, the Calibrating screw 74 is so positioned as to extend through the slide 35, the end portion 73 of the screw forming a part of the surface 72. When the switch arm is in the latched position the segment 49 rests upon the end of the screw resulting in the precise positioning of the free end 65 of the cantilever-mounted thermostatic element with respect to the latching portion S6. It may now be seen that the depth of engagement of the end 65 with the portion 86 may be determined by a preliminary setting of the screw 74. As the end 65 of the thermostatic element is adapted to move away from the surface 72 upon being heated. disengagement of the end 65 and portion 86 may be determined as a function of the current passing through the thermostatic element.

Referring now to Figs. 3 and 4, after the actuator has translated the slide member to the vicinity of the extreme lower position, the lower edge of the arm 134 engages the end 146 of the stud 137, further downward movement of the components resulting in a clockwise moment upon the link 112 about its.pivot. on the shaft 54. The toggle comprising the links 111 and 112 is thereby caused to collapse or break to effect a release of the actuator with respect to the slide. Referring to Fig. 7, the button 113 may move to a lowermost position, illustrated in phantom, engaging and being restrained by the shoulder of the ring 144. The links 111 and i12 move toward a position as illustrated in phantom as determined by the upward movement of the slide 35 under the inuence of the spring 78. Theslide as shown in Figs. 6 and 7 is in the lower position, further upward movement being prevented by engagement of the contacts 51 and 94 and cooperative engagement of the end 65 of the thermostaticV element with the latching portion 86 of the slide. It may now be understood that the sequence of movements above described from the time of tripping of the toggle occurs very rapidly whereby the slide may accelerate rapidly from the extreme lower position to the lower position resulting in a relatively quick closing of the contacts 51 and 94.

The lower position assumed by the slide as illustrated in Figs. 6 and 7 is sufficiently clear of any interference with the lower extremity of the button 113 in the lowermost position as shown in phantom. The arrangement, therefore, is Vsuch that the operator may depress the 'outton to the fullest extent without precluding a closing of the circuit.

Referring to the particular structure shown in Fig. 7, when the operator releases the button 113 it will move to the position illustrated by the full lines and the toggle or the links 111 and 112 will move from the position illustrated in phantom to the full line position. The spring 128 normally urges the toggle to a slightly overcenter and rigid condition, but the tension of the spring 128 is insuflicient to render the toggle rigid due to the clockwise moment applied to the link 112 by the compression of the spring 135. Therefore, when the breaker is in the circuit closed position the circuit may not be manually interrupted by depressing the button for such movement will merely translate lthe toggle to the position illustrated in phantom. The particular arrangement does provide, however, a means whereby the operator, by touch, may determine whether the breaker is in a circuit closed position. A depressing of the button when the breaker is closed (see Fig. 7) is only opposed by the combined effect of the springs 128 and 135. The small flaccid or spongy reactive force is indicative that the circuit is completed through the breaker as opposed to a relatively great reactive force presented by the spring 78 when the breaker is in the circuit open position.

The circuit closed position of the breaker is illustrated in Figs. 6 and 7 and is illustrated in condition for a thermal or manual interruption. The current path through the device is via terminal 30, bracket 96, contacts 94 and 51, switch arm portion S0, thermostatic element 62, cable 90 and terminal 29. The thermostatic element is associated with the cable 98 in such a manner as to permit current to flow through the thermostatic element whenever the breaker is in the circuit closed positione When the external circuit is subjected to an overload current of such a value that it is desirable to cause an automatic interruption of the circuit, the thermostatic element progressively exes so as to cause the thermostatic element portion 65 to move away from the surface 72 of the slide and out of engagement with the latching portion 86. It is particularly noted that the thermostatic element movement with respect to the latching portion 86 is precise as a function of the current flowing through the element. The accuracy is accomplished through the cooperation of the switch arm segments 48, 49 and their surface abutment with the surface 72 of the slide. In the absence of the segments the exure of the thermostatic element rather than resulting in a positive movement thereof with respect to the latching portion would result in a rocking or wobbling of the shaft 54 with respect to the slide rendering it practically impossible to determine with any accuracy the current at which the breaker would open or the time required for opening. However, as the hermostatic velement and the switch arm are rigidly integrated in the vicinity of the shaft 54, and as the segments 48, 49 abut the surface 72 of the slide, it may be readily recognized that the thermostatic element is balanced and positively cantilever-mounted with respect to the slide so that any exure of the thermostatic element appears only at the end 65 thereof. It is also to be noted that the spring 78 in effecting a tightening action as heretofore described further assures a positive positioning of the thermostatic element.

As the thermostaticelement is released from the latch-` In 'the particular embodiment of the breaker shown in the drawings the components may be so designed as to permit the moving elements to gain considerable momentum prior to opening of the contacts 51 and 94. For exampleupon a releaseof the end 65 of the thermostatic element the tension of the spring 78 is effective to swing the switch arm and raise the slide. As the segments 48, 49 have a coeflicient of friction with respect to the surface 72 of the slide, the contacts 51 and 94 will remain in` engagement during the initial increments of movement of the slide and the switch arm. As the components approach their circuit open positions, considerable momentum has been gathered as well as a relative loosening of the parts due to progressive decrease of the effect of the spring 78 on the shaft 54. Accordingly, the contacts 51 and 94 may be separated more rapidly than would otherwise be possible in the absence of the effect of momentum.

As the elements of the breaker move from the position in Figs. 6 and 7 to the position in Figs. l and 2, the toggle is affected by a change in the combined effect of the springs 128 and 135. As the link 112 moves upwardly with the slide, the moment of the arm 134 due to the compression on the spring 135 is reduced permitting the spring 128 to pull the links 111 and 112 into the overcenter and rigid condition as illustrated in Fig. 2. Accordingly, the breaker is automatically and immediately pre-set for a subsequent manual closing thereof without the necessity of manually vresetting subsequent to a thermal interruption.

Manual interruption of the external circuit may be accomplished by a lifting force applied to the button 113 which ultimately results in a disengagement of the thermostatic element 62 from the latching portion 86. Referring to Figs. 7 and 10 as the button 113 is manually raised the Aarm is similarly raised, the shank 122 of the arm lifting the upper extremity of the link 111 so as to draw the toggle comprising the links 111 and 112 into a taut and rigid condition whereby the end of the enlarged diameter portion 5S of the shaft 54 is urged upwardly. Due to the clearance between the shaft 54 and the passage 56, the shaft partakes of a counterclockwise movement as viewed in Fig. l0 so as to cause a rockable displacement of the switch arm 47 and the thermostatic element 62 with respect to the slide 35. As the thermostatic element and the segments 48, 49 extend substantially radially of the shaft 54 as illustrated in Fig. 6, the displacement of the lthermostatic element 62 partakes of a twisting and lifting movement to cause the thermostatic element portion 65 to disengage from the slide member latching portion 86. In the absence of the segment 48 the displacement of the thermostatic element would be primarily a twisting movement. It may be understood, therefore, that the segment 48 cooperates in providing an effective pivot for rockable displacement of the switch arm and the thermostatic element, the pivot being about an axis extending through a point ot" abutment of the segment 48 with the surface 72 of the slide member.

The portion of the structure of the modilication illustrated in Figs. 1345, inclusive, is substantially the same as described for the embodiment of Figs. l-lZ, inclusive. In the modification, however, when the breaker is in the circuit closed position the links 111 and 112 do not assume the angularly disposed position as shown in Fig. 14 due to a balancing Vof forces applied by a tension spring and a compression 'spring (viz., springs 128 and 135 as heretofore described) but assume such a position under a balancing of forces due to the engagement of the side edge 164 of the cam 158 of the latching arm 155 with the nose 163 of the link 111. In this instance it is to be recognized that the latching arm 155 is an effective spring providing a reactive force opposing the force of the spring 128. However, the action is more in the nature of a latching action intermediate the link 111 and the arm 155.

The action may be described more clearly by examining a complete cycle of manual operation. Referring to Fig. 15 wherein the breaker is shown in the circuit open position, the nose 163 and arm 155 are out of engagement. However, upon manually depressing the actuator the links 111 and 112 move progressively downwardly in unison in their overcenter relationship and during such progressive movement the surface 166 of the nose 163 engages the cam 158 of the arm 155. Further movement causes the arm to flex about its mount until the arm 134 of the link 112 engages the stud 137 for tripping of the toggle. As the links 111 and 112 collapse, the nose 163 in moving with the link 111 is rapidly withdrawn from engagement with the latching arm 155 permitting the arm to return to the freely extended position. When the actuator is released by the operator the links will return to a position as shown in Fig. 14, further movement being restrained by engagement of the nose 163 with the side edge 164 of the cam 153.

To manually open the breaker it is only necessary for the operator to exert an upward force upon the button 113 which urges the links toward an in-line relationship. The manual force is translated to the point of engagement of the nose 163 and the latching arm 155. As the force increases the surface 167 of the nose presses laterally and upwardly against the side edge 164 of the cam 158 displacing the lower portion of the latching arm 155 upwardly (as viewed in Fig. 14) permitting the tip 168 to pass under the cam 158 and under the upper portion 159 of the latching arm. The coil spring 128 in combination with the lifting movement applied to the upper extremity or" the link 111 draws the links into a rigid condition permitting the upward force to be applied to the shaft 54 for release of the switch arm as hereinbefore described.

While the embodiment of the present invention that has been illustrated and described is now regarded as the preferable embodiment, the construction and arrangement of parts are, of course, subject to modification without departing from the spirit and scope of the invention. It is therefore not desired to limit the invention to the particular form of construction illustrated and described but to cover all modifications that may fall within the scope of the appended claims.

I claim as my invention:

l. In a circuit breaker for interruption of an electrical circuit, the combination of: a housing; line and load terminals for said housing; a slide member supported by said housing and adapted to be reciprocally translated therein between upper and lower positions, said member providing a first bearing surface and a latching portion; a switch arm movable by said slide member and adapted upon downward movement of said member to movebetween a released position and a latched position, said arm including a second bearing surface for slidable abutment with said first bearing surface; a thermostatic element secured to said switch arm adapted to flex with respect to said second bearing surface and being in conductive relation with a portion of said arm, said element being adapted, when cold, to engage with said latching portion when said arm is in said latched position, said engagement being limited by the Vabutment of said first and second bearing surfaces; a conductive member between one of said terminals and said thermostatic element, association of said conductive member with said element being in such a position as to permit current to flow 14 through said element when said circuit is completed; a stationary contact connected to the other of said terminals and positioned with relation to said housing so as to be in electrical contact and abutment with said switch arm portion when said arm is in the latched position to complete said circuit; and spring means intermediate said housing and said slide member to bias said member toward said upper position so as to urge said switch arm portion into abutment with said stationary contact when said switch arm is in the latched position, whereby flexure of said thermostatic element, when heated, results in disengagement thereof from said latching portion to permit said switch arm to move to said released position.

2. In a circuit breaker for interruption of an electrical circuit, the combination of: a housing; line and load terminals for said housing; a slide member translatable'in said housing between upper and lower positions, said member providing a rst bearing surface and a latching portion; a switch arm pivotally mounted on said slide member and rotatable between a released position and a latched position, said arm including a second bearing surface for slidable abutment with said rst bearing surface; a thermostatic element secured to said switch arm for integral movement therewith and in conductive relation with a portion of said arm, said element being adapted to ex with respect to said slide member, said element also being adapted, when cold, to engage with said latching portion, said engagement being limited by the abutment of said first and second bearing surfaces; a conductive member intermediate one of said terminals and said thermostatic element, connection of said conductive member being such as to permit current to iiow through said element when said circuit is completed;la stationary contact connected to the other of said terminals and positioned with relation to said housing soas to engage with said switch arm portion upon rotation of said arm toward said latched position to complete said circuit; and spring means intermediate said housing and said switch arm to bias said arm toward said released position and to bias said slide member toward said upper position, upward movement of said slide member being restrained by contact of said switch arm portion with said stationary contact completing said circuit when said thermostatic element is in said latched position engaging said slide member latching portion.

3. In a circuit breaker for interruption of an electrical circuit, the combination of: a housing; line and load terminals for said housing; a slide member translatable in said housing between upper and lower positions, said member providing a latching portion and also providing a first bearing surface adjacent said latching portion; switch arm pivotally mounted on said slide member and rotatable between a released position and a latched position, said arm including a second bearing surface extending upwardly of the pivot and in slidable abutment with said rst bearing surface; a thermostatic element secured to said switch arm for integral movement therewith and in conductive relation with a portion of said arm, said element extending in substantially the same direction as said second bearing surface and being adapted to Hex 'with respect to said second bearing surface and, when cold, to i engage with said latching portion; yieldable means intermediate said housing and said switch arm to yieldably urge said first and second bearing surfaces into abutment; a conductive member between one of said terminals and said thermostatic element, association of said conductive member and said element being such as to permit current to flow through said element when said circuit is completed; a stationary contact connected to the otherl with relation to said U of'said terminals and positioned housing so as to engage with said switch arm portion upon rotation of said arm toward said latched position; and means biasing said switch arm toward said released position and said slide memberA toward said upper position,

upward movement of said slide member being restrained by contact of said switch arm portion with said stationary contact completing said circuit when said thermostatic element is in said latched position engaging said slide member latching portion.

4. in a circuit breaker for interruption of an electrical circuit, the combination of: a housing; line and load terminals for said housing; a slide member translatable in said housing between upper and lower positions, said member `providing a latching portion and also providing a bearing surface; a switch arm providing a segment for slidable abutment with said bearing surface, said arm being pivotally' mounted on said slide member and displaceable between a released position and a latched position; means biasing said slide member toward said upper posi` tion and said switch arm toward said released position; means carried by said housing for engagement with said switch arm for pivotally displacing said arm toward said latched position when said slide member is translated toward said lower position; a yieldable means intermediate said housing and said switch arm to urge said segment and said bearing surface into abutment; a thermostatic element secured to said switch aim for integral movement therewith and in conductive relation with a portion of said arm, said element extending substantially parallel to the plane of traversal of said segment, said element including a portion adapted, when said element is cold, to engage with said latching portion when said switch arm is in said latched position and, when said element is heated, to flex away from sai-d slide member bearing surface and said segment to disengage said thermostatic element portion from said latching portion to permit said switch arm to move toward said released position; a conductive member between one of said terminals and said thermostatic element, association of said conductive member with said element being such as to permit current to flow through said element when said circuit is completed; and a stationary contact connected to the other of said terminals and positioned with relation to said housing so as to intercept said switch arm portion to complete said circuit when said switch arm is in sai-d latched position and said slide member is in said lower position, upward movement of said slide member being restrained by engagement of said thermostatic elment portion with said latching portion and Contact of said switch arm portion with said stationary contact.

5. A circuit breaker according to claim 4 in which said switch arm is pivotally and rockably mounted on said slide member, said slide member being provided with adjustable means to vary the contour of said bearing surface at the point of abutment with said segment when said switch arm is in the latched position for rockable displacement of said switch arm, whereby said thermostatic element portion may be ad'iustably positioned toward and away from said slide member.

6. In a circuit breaker for interruption of an electrical circuit, the combination of: a housing; at least two terminals for said housing; a slide member translatable in said housing between upper and lower positions, said member providing a latching portion, a bearing surface, and an annuiar passage; a switch arm having a shaft receivable in said annular passage for pivotal movement of said arm between a released position and a latched position, said arm including a segment for slidable abutment with said bearing surface, said shaft being of a diameter to permit rockable displacement of said arm with respect to said slide member; yieldable means urging said segment into abutment with said bearing surface; a thermostatic element forming a part of said switch arm for integral movement therewith and in conductive relation with a portion of said arm, said element extending over said bearing surface and including a portion adapted, when said element is cold, to engage with said latching portion and, when said element is heated, to move away from said bearing surface to disengage said element from said latching portion; means carried by said housing for engagement with said switch arm for pivotally displacing said arm toward said latched position when said slide member is translated toward said lower position; a conductive member between one of said terminals and said thermostatic element, association of said conductive member with said element being such as to permit current to flow through said element when said circuit is completed; a stationary contact connected to the other of said terminals and positioned with relation to said housing so as to intercept said switch arm portion to complete said circuit when said switch arm is displaced toward said latched position, upward movement of said slide member being restrained in said lower position by engagement of said thermostatic element portion with said latching portion and contact of said switch arm portion with said stationary contact; and resilient means biasing said slide member and said switch arm toward said upper position and said released position, respectively.

7. A circuit breaker according to claim 6 in which said slide member is provided with a shoulder extending substantially parallel and adjacent to said annular passage forming a buttress for said shaft extending outwardly of said passage so as to limit said rockable displacement of said switch arm to a predetermined arc.

8. A circuit breaker according to claim 6 which includes spring means rockably urging said shaft and switch arm, when said switch arm is in the latched position, in

such a direction as to tend to urge said thermostatic element portion to disengage from said latching portion, the force of said spring means as applied to said shaft being insufficient to cause said disengagement in the absence of upward moving force of said actuator.

9. A circuit breaker according to claim 8 in which said resilient means and said spring means comprise an integral element connected intermediate said switch arm and said housing. Y

10. A circuit breaker according to claim 6 in which said annular passage extends normal to the plane of translation of said slide member and in which said thermostatic element, when said switch arm is in the latched position, extends substantially radially of and partially upwardly from said annular passage; a shoulder for said slide member extending substantially parallel and adjacent to said annular passage forming a concave buttress to receive said shaft extending outwardly of said passage, whereby said rockable displacement of said switch arm is limited to tilting movement about an axis extending substantially laterally of and substantially normal to said annular passage; and an actuator connected to said shaft adjacent said shoulder and movable by an operator for translation of said slide member, upward moving force on said actuator, when said slide member is restrained in said lower position, rockably displacing said switch arm so as to `tilt said thermostatic element portion out of engagement with said slide member latching portion.

ll. in a circuit breaker for interruption of an electrical circuit, the combination of: a housing; line and load terminals for said housing; a slide member translatable in said housing between upper and lower and extreme lower positions, said member providing a latching portion'and an annular passage; a switch arm having a shaft receivable in said annular passage for pivotal movement of said arm between a released position and a latched position, said shaft having a lesser diameter than said passage to permit rockable displacement of said arm with respect to said slide member; yieldable means urging said switch arm into abutment with said slide member; a thermostatic element forming a part of said switch arm for integral movement therewith and in conductive relation with a portion of said arm, ,said element lincluding a portion adapted, when said element is cold, to engage with said latching portion and, when `heated, to disengage from said latching portion; means carried by said housing for pivotally displacing said switch arm toward said latched position when said slide member is translated toward said lower position; a conductive member between one of said terminals and said thermostatic element, association of said conductive member with Said element being such as to permit current to flow through said element when said circuit is completed; a stationary contact connected to the other of said terminals and positioned with relation to said housing so as to intercept said switch arm portion to complete said circuit when said arm is pivotally moved toward said latched position, upward movement of said slide member being restrained in said lower position by engagement of said thermostatic element portion with said latching portion and contact of said switch arm portion with said stationary contact; an actuator carried by said slide member; collapsible linkage means intermediate said actuator and said shaft, said linkage means normally providing a rigid connection therebetween for substantial rigid integration of said actuator to said slide member; abutment means positioned with respect to said housing so as to engage with said linkage means to collapse the same when said slide member is translated toward said extreme lower position; and resilient means biasing said slide member `toward said upper position.

12. A circuit breaker according to claim ll in which said linkage means is connected to said shaft and in such a position as to cause rockable displacement of said arm with respect to said slide member when said actuator is moved so as to raise said slide member through the medium of said linkage means, said displacement of said arm disengaging said thermostatic element portion from said slide member latching portion.

13. A circuit breaker according to claim 1l in which said abutment means is so positioned as to collapse said linkage means when said slide member is translated toward and reaches said extreme lower position permitting said resilient means to urge said slide member into said lower position, upward movement of said slide member being restrained by contact of said switch arm portion with said stationary contact and engagement of said thermostatic element portion with said slide member latching portion.

14. A circuit breaker according to claim 1l in which said linkage means comprises an upstanding normally rigid overcenter toggle having at least two arms each pivotally connected to the other at one end thereof, the opposite ends thereof being pivotally connected respectively to said actuator and to said shaft, the collapse of said linkage means permitting said slide member to move independently of said actuator toward said lower position.

15. A circuit breaker according to claim ll which includes spring means normally urging said linkage means to provide said rigid connection.

16. A circuit breaker according to claim l5 which includes a second spring means intermediate said linkage means and said housing normally urging said linkage means, when said slide member is out of said upper position, in such a direction as to collapse the same, the combined force eilect of both said spring means being insuicient te cause said linkage means to assume said rigid connection when said slide member is in said lower position.

17. A circuit breaker according to claim l5 which includes a resilient latching means intermediate said linkage means and said housing normally restraining said linkage means, when said linkage means is collapsed, from assuming said rigid condition, the force effect of said spring means being insuicient to cause said linkage means to assume said rigid connection.

18. A circuit breaker according to claim 17 in which said latching means comprises a resilient member providing a cam, and an engaging nose mounted upon said linkage means, said nose being adapted for movement into and out of engagement with said cam during reciprocal movement of said linkage means, said resilient member providing a yieldable latch for engagement with said nose to restrain said linkage means in said collapsed position.

References Cited in the file of this patent UNITED STATES PATENTS 2,131,640 Sachs Sept. 27, 1938 2,343,264 Platz Mar. 7, 1944 2,343,612 Frank et al Mar. 7, 1944 2,385,727 Platz Sept. 25, 1945 2,516,670 Bourne July 25, 1950 2,548,825 Schwend et al Apr. 10, 1951 2,613,296 Wood Oct. 7, 1952

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