US2358357A - Circuit breaker and overload protective device - Google Patents

Description

Sept. 19, 1944. w. E. sTlLwELL, JR y 2,358,357

CIRCUIT BREAKER A'ND OVERLOAD PROTECTIVE DEVICE Filed May 1, 1942 2 Sheets-Sheet l www "mn o if, ,Jffmfummfffmwwm@ l IE 62a' i :O

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ga ORNY Sept 19, 1944 w. E. sTILwELL, JR 2,358,357

CIRCUIT BREAKER AND OVERLOAD PROTECTIVE DEVICE Filed May l', 1942 2 Sheets-Shea?. 2

2o v. INVENTOR Willi ESilweLJ-n LOAD Patented Sept. 19,1944

crncurr Bamm AND ovEnLoan raorEc'nvE nEvIcE William E. Stilwell, Jr., Cincinnati, Ohio, assignor to John B. Pierce Foundation, New York, N. Y., a corporation of New York Application May 1, 1942, Serial No. 441,383

(Cl. 20G-88) 14 Claims.

This invention relates to circuit breakers, and particularly to circuit breakers adapted for remote control, and embodying overload protection means.

Among the objectives of the invention are: K

To provide a circuit breaker, as aforesaid. which is exceedingly compact in form and lightl in weight, thereby rendering the same applicable to installations where size and weight are of importance, such as in aircraft;

To provide a circuit breaker which is reliable in operation, and inexpensive in construction;

To provide a circuit breaker of the overload .protection type, which will withstand extreme conditions of vibration and violent positional change without change in its operating characteristics;

To provide a circuit breaker which may be contained in a sealed, gas-proof and explosionproof housing; To provide a circuit breaker having "trip-free characteristics;

To provide a circuit breaker having overload protection, in which the overload cut-out point may be changed by simple substitution of elements without change in the circuit breaker mechanism, per se; and

To provide a circuit breaker having overload protection, in which, after the circuit has automatically been broken imder the influence ot overload, it is necessary for the circuit breaker to be thrown to oil position before the electric circuit can again be closed.

The circuit breaker is adapted for remote control; such remote control may be actuated mechanically, as by a Bowden wire or equivalent means for transmitting mechanical movement, but preferably, the remote control circuit embodies magnetic actuating means. It is desirable for operate the magnetic system on low voltage, to make possible the use of small size conductors, lightly insulated, for the remote control circuit. When employed with low voltage control circuits, a suitable transformer may be incorporated in the circuit breaker housing. r, if desired, a transformer may be connected into the remote control circuit at a location remote from the circuit breaker.

In aircraft, boats, or other installations where low voltage is available for lighting or otherservice, the remote control may be operated directly by said low voltage service; usually, such low voltage circuits are direct current.

A preferred form of circuit breaker embodying the present invention, therefore, includes a pair of magnetic coils, centrally arranged with respect to which is an armature system, movable toward one or the other of the coils, depending upon the energization thereof. The armature system includes a magnetically responsive member extending from each end of which, and secured thereto in the line of the axis thereof, is a shaft; to each shaft, at its end, is secured a suitable toggle spring.

0ne of said toggle springs, hereinafter referred to as the throw spring, operates under an initial impulse engendered by magnetic force, to move the armature toward or away from the electric contacts of the load circuit depending upon which of the coils is energized, and to carry such armature through the full extent of its permitted travel, even though the magnetic coil Spring.

The load-line contacts are carried by bimetallic members through which the load current passes. Under the influence of an overload condition,- the bimetallic elementsheat, warp, and exert a substantial pressure on 'the "contact spring. Upon the attainment of suitable pressure by the warping of the bimetallic members, the equilibrium of the "contact spring is overcome, and'it will reverse its position, thereby mapping the contacts carried thereby, out of engagement with the load-line contacts.

Desirably the "contact toggle spring is of a. double equilibrium type, that is, it will not automatically return to circuit closing position after the interruption of the load circuit has permitted the bimetallic elements to cool to their initial position and hence no longer exert pressure on said toggle spring.

It is a feature of the invention, also, that the "throw" spring is stronger than the contact spring, whereupon the pressure exerted upon the contact spring by the bimetallic elements, and the reaction of said spring under the influence thereof, will not cause the "throw spring to reverse its position.

To reclose the circuit after it has opened under the iniluenceof overload, it is necessary for the operator to energize the oiPniagnetic coil to move'the armature. The "contact spring is drawn thereby into forcible engagement with suitable abutments, and the pressure exerted against the contact spring by such abutments, causes the contact spring again to reverse its position to resume itsnormal circiut closing position. However, as the entire apparatus is then in E position, it is necessary to close the on circuit to again move Athe armature and bring the contact spring into circuit closing engagement with the load contacts.

A second form of invention which retains many of the favorable operating characteristics of the double-magnet type previously discussed, may include -a single electromagnet for moving the contacts into circuit closing position and retaining them in such position against the reactive eilort of a single equilibrium point toggle spring biased to return the movable contacts to open circuit position when the magnet coil is deenergized.

A feature of overload protective circuit breakers embodying thlnvention resides in mounting the birnetalllc overload elements on a removable cap or plate, whereby precisely the same actu- 'ating mechanism may be employed with overload elements of any desired degree of overload actuation, merely by using in connection with the standard mechanism a cap or plate having appropriate overload elements.

Other features and advantages will hereinafter appear. l

In the accompanying drawings: l

Fig. 1 is a perspective of a completely housed circuit breakerembodying the present invention;

Fig. 2 is an enlarged section taken through 2-2 of Fig. 1, illustrating 'the circuit breaker in A circuit closing position; I i Fig. 3 ls a partial section similar to Flg.2, illus trating the circuit breaker immediately after the ywarping of the bimetallic overload members has thrown the contact. toggle spring into circuit breaking position, the throw toggle spring and armature system of the circuit breaker remaining in circuit closing position;

Fig. 4 is a partial section similar to Fig. 3, but showing the circuit breaker in normal open circuit posltion;

Fig. 5 is a'partial plan view of the closure member of the circuit breaker housing, taken from the underside to show the disposition of the bimetallic overload elements and contacts thereof;

Fig. 6 is a. fragmentary plan view of the circuit breaker with the closure member removed;

Fig. 7 is a, plan view of a preferred form of contact toggle spring with contact structure thereon: Fig. 8 is a plan view of a preferred form of throw toggle spring; Y v

Fig. 9 shows a typical wiring diagram for; low voltage remote control of the circuit breaker of Fig. 2;

ing a magnetically operated switch mechanism and coordinated transformer, has the overall physical dimensions enabling it to be installed in a standard 1%"by 35/3" outlet box.

'Ihe housing comprises a body 2| and closure 22 therefor, completely encasing the operative parts of the apparatus, to render the same immune from dust, chemical fumes, gases, or thelike, and adapting it for use under conditions where explosive gases may be present, as in submarines, mines, or chemical manufacturing plants. A plurality of screws 'may be, employed a to maintain a tight interassembly of body and closure, and a suitable gasket (not shown) may be used to insure complete air tightness. Desirably, the body andA closure may be molded from suitable plastics, suchsas Bakelitek or equivalent.

The closure 22 is formed with a ange 23 deiining an annular recess 2li at an end of the closure. At the base of said recess there is a4 sheet 25 of asbestos or equivalent having suitable re-proof and heat insulation qualities.

Referring to Fig. 5, a plurality, illustratively two, of load-line contact members 2B, 26, are positioned upon the sheet 25, and normally, that is, under normal load conditions, lie dat against said sheet, as shown in Fig. 2. Each of thecontact members 23 is secured at its end to the closure .22, as by the studs 21, which pass through the closure 22 to form binding posts or the like for the attachment of the conductors 0f the load circuit.

At the free end of each of the contact members 26 there is a contact 28, desirably a. button or stud of silver or other material possessing high conductive qualities and resistance to pitting or corrosion under the inuence of an electric arc.

I'he contact members 26 are bimetallic', in that they are formed from laminations of metals having different coeicients of expansion, such as steel and copper, or-other suitable combinations known in the art. So that the contact members 2E will warp away from the sheet 25 under the inuence of heat, the metal having the higher coemcientfof expansion faces said sheet.

As previously stated, said bimetallic members 26 are conductor elements of the load circuit, and the contacts 28 thereof are engageable, under conditions of operation of the invention, by a contact structure which completes the circuit therebetween. A

Desirably, the said contact structure is brought into and out of circuit closing engagement with the contacts 28 of the contact members 26 by electromagnetic means, such method of operation lending itself to remote control whereby a simple push button or the like' may be employed to close the operating circuit.

The electromagnetic operator for closing and opening the electric load circuit comprises a pair of magnet coils 3G, Si, would upcn suitable spool construction embodying steel caps 32, 32a, with central wall structures 33, 33a acting as poles for Axially msitioned and secured to said core 3d vat each end thereof, and passing through an opening provided in the stop members 32, 33a

are rods Sii, Si?.

When magnetic coil t-'hereinafter called the on' coil-is energized, Athe armature system,v

comprising the core 3d andtherewith associated rods is drawn in the direction of the contacts 2l to close the load circuit, whereas when the "oiT coil 3l is energized, the amature system will move in reverse direction, to break the load circuit.

To carry the armature system through its full travel with but a momentary energization of the magnet coil, and with a snap motion, there is employed, in operative association with rod 3l, a toggle spring Il.

Improved operating characteristics result from' 10 42, the dished rim 4i having a permanent set,

whereas the legs 42 have no permanent set. In such construction, the legs I2 have a curvature tangential to the rim,.and are maintained in bowed elastic tension by the permanent set of rim 4i. An-important characteristic of such a toggle spring is that a force-induced movement of approximately twenty-live (25) Per cent of the total throw of the spring causes the spring to throw through its full travel.

By a suitableproportion of the thickness of the rim and the depth to which the rim is dished, the toggle spring may have either one or two positions of stable equilibrium; that is, the toggle spring may be such that when it is vdeflected to a reverse curvature, it will return to its original curvature when the defiecting pressure is released or, as a double equilibrium spring, the toggle spring will remain inthe curvature to which it has snapped.

In the instant embodiment of the invention, it is preferable to employ a double equilibrium toggle spring for the member 48.

As shown in Fig. 8, the legs 42 join at a circular portion at the geometric center of the spring; at the center of such hub, is a hole suitable to receive the rod 3l. The rod may be secured to the spring 40 by means including the washers 43, 44; and the rod 31 may either be riveted over said washer M, or the end of the rod may be threaded to receive lock nuts (not shown) to sey cure the rod 3l to the spring I0. Y

The spring 40 may be relatively loosely supported about its periphery in a suitable shoulder or kerf I6 formed in the housing 2l; the peripheral corner oi the coil spool 32a serves to secure the toggle spring M in position while permitting unrestrained flexing thereof.

Io compensate for possible inaccuracies resulting from the molding of the closure 22, and to permit said closure to maintain the coils 36, 3i, in correct, iixed, position, a metal ring 22o is interposed between ang'ex and coil cap 32. i

The contact toggle' spring, 66,' is mounted on the rod 36 so `as to provide a limited swivel acltion about theend of the rod. Said toggle spring 50 preferably also has a double equilibrium characterlstic, and may be otherwise similar to the toggle spring 46.

Mounted on spring 50, to close circuit across the load contact buttons 28, 28, is an inflexible ring deslrably a dished ring of silver, the outer edge of which is reversed upon itself to provide opposed rims between which the spring 5B may be loosely held about its rim. The loose mounting of ring 5I on spring 5II renders it free to rotate about spring 50, and the full periphery of the ring 5| is available as contact surface, 'la

thereby equalizing wear, and lengthing its operating life.

Referring now to Fig. 9, the circuit breaker is shown as wired in a volt power circuit with a transformer T used to reduce the voltage of said circuit suitably for the control circuit, preferably to 24 volts.- In the control circuit, dignated C, are any desired number of push-button switches S. The push-button switches S are of double throw type; the central pole of the switch is common toboth magnetic coils, and throw of the switch in one position energizes the on coil 30 whereas the other switch position energizes the oit coil 3i.

With the oi coil energized, the circuit breaker is in the 4 position; each of the toggle springs 4B and l is in a concave shape, as viewed in said figure. Upon energizing the on coil 3l, magnetic core 34 and associated shafts 36, 3l are drawn toward the closure 22, whereupon after a short movement of the armature system, the spring 46 snaps into the Fig. 2 position, and contact ring 5i is brought sharply into contact with the contacts 28 on the members 26. Spring 6l, however, retains its initial position oi' stable equilibrium. Desirably, the ring 5l engages the contacts 28 before the spring 4B has attained full throw, whereupon the unexpended energy of spring Il! maintains the contact ring Si resiliently in engagement with said contacts. Spring 5l should be of such stiffness that it will remain in its initial position of stable equilibrium under the impact force of the engagement of the ring 6I with the contacts, and under the residual or unexpended energy of spring 4D.

Under overload, bimetallic members 26 are subjected to the heating effect of the overload, and the unequal expansion of the laminations of said members, warps them away from base plate 25, to exert an angularly directed pressure upon the ring 6I, and-hence upon the toggle spring 50 associated therewith. If members 28 warp unequally, the self-adjustment of spring 50 permits its inclination toward that contact 28 having the f least movement, maintaining contact with each contact 28 until the throw point of spring 5U is reached. The angular pressure exerted by contacts 26 against ring 5| may enforce brief angular rotation thereof.

When the overload persists, pressure of members 26 against toggle spring 5U steadily increases, until toggle spring 50 is snapped from its concave position shown in Fig. 2, to its convex position shown in Fig. 3. In other words, the spring 6l will assume its second position oi stable equilibrium. The throw of the spring 5I! to its new position moves the ring 5I completely out oi.' engagement with the contact buttons 28, thereby immediately breaking the circuit. In the broken-circuit position oi vthe spring 60, it will be noted that the inner surface of the contact ring 6I bears against the coil cap 32.

The electric circuit having been broken, the contact members 26 will .cool and resume their normally nat position upon the base plate 25.

The relation of comparative strengths of the springs Il and 50 is such that the spring l0 will remain in its convex or closed circuit position under the iniluence of pressure of the contact members 26 against the spring 50.

Spring l0 and associated armature assembly remains in circuit closing position; but because the spring 5D is of a double equilibrium type, it will remain .in open circuit position, with the edges of the ring 5| in contact with the coil cap 32. The operator, to return the circuit breaker to v a status wherein the load circuit lmay again b'e closed must first venergize the oil coil Il, to draw the magnetic armature system into the "ofP position. I

The movement oi the armature system returns the spring 50 to its original position, for it isrecalled that said spring 50, or the rimof the ring 5I associated therewith, bears against the coil cap 32, and the reaction pressure against said rim snaps the spring 50 to its initially concave, i. e., circuit closing shape. l.

Upon energizing the on coil 3U, therefore, the amature system and therewith associated contact ring 5| resumes the closed circuit position.

Under certain load conditions, spring 50 may be utilized per se as a contact structure without thereon orriveted thereto, for cooperation with` the 'contacts 28 of the members 26. If such construction is employed, any suitable means may be 'taken to prevent rotation of the spring 50 with respect to the contacts 28 to insure a satisfactory contact upon closing the circuit.

sure upon the contact spring 10. When. said bimetallic members have warped suiiiciently, the contact spring is snapped into its reverse position of stable equilibrium, thereby breaking Fig. 10 illustrates, in vertical section, an embodiment of the invention wherein a single magnetic coil is employed to close the circuit and to 4maintain the closed circuit status. Pursuant to this form of the invention, the throw spring 60 has but a single point of stable equilibrium;

that is, as soon as the pressure exerted on said spring to effect its overthrow Ais released, the

'spring will immediately revert to its original position. The contact spring 'Hi is a 'double equilibrium spring such as the spring 50 previously described.

As shown in Fig. 10, the single,magnetic coil 80 is contained within a suitable housing. -An amature system includesa core 8i, to which are secured shafts 82, 83. Shaft B2 carries the double equilibrium contact spring 10, said spring having suitable contact means 1i, il thereon. At its end, shaft 83 is secured to the single equilibrium spring 60, the latter being normally biased to circuit opening position, as shown in full line in Fig. 10. Spring 60 is freely held about its periphery in a kerf in housing element Bi, as

dot-dash line, and the contacts 1i of the contactv spring l0 are brought into circuit closing position against the load contacts Sl, 90. So long as the.

control circuit is kept closed, the continuing circuit'inclosed position, against the urging of the single equilibrium spring I0 to return'the armature assembly and contact spring 18 to open circuit position.

In a circumstance of overload m the load-circuit. the bimetallic members 92, l2 warpin prothe load circuit. Because the spring 10 has two positions of stable equilibrium, said spring will not again reverse itself when the cooling of the bimetallic members 92, 92 has returned them to their original position against the base 93.

The position assumed by the contact spring 10 after it has been snapped open under overload is with its periphery. against, or closely adjacent, the housing cap |00, as shown bythe dotted line in Fig. 10. -In such position of spring 10, the contacts thereof cannot be 'brought into engagement with contacts 90. In order to restore the contact spring 10 to a position permitting subsequent reclosing of the load circuit, the operator must open the control circuit; that is, he must deenergize the magnet 80, whereupon the single equilibrium spring 60 reverts to its original, i. e., open circuit, position, moving the armature system in the direction of the housing cap |00. Such movement of the armature-system exerts a pressure upon said spring 10 sufilcient to reverse its position, wherein it is again in position to close the circuit across the contacts 90, 9D. However, the entire circuit breaker system is then in open circuit position, and the control circuit C must again be closed to energize the magnet 8l! to reclose the load circuit. I i

To minimize the current required for magnetically holding the load contacts in closed circuit position, it is advantageous to interpose a isdeenergized, the contacts 62 are in engagemagnetic force of the magnet 80 holds the load ment with contacts 63, and because of the high value of resistance R, with respect to the resistance of the spring 60, the resistance Ris shunted out of the control circuit. At the instant oi closing push button P, 'the path of current in said control circuit is through magnet coil 8B, and the spring system, including contacts 62, 63. The magnet 80 pulls the armature system, as aforesaid, and as the spring 60 imparts a snap action to the movement of the system, the armature system and spring 80 move practically in coordination. Just prior to the stage of throw ol' spring 60, the contacts 6l, 82, break with the contacts 83, 84. respectively, and the current path of the control circuit is through resistance R. The introduction of the'additional resistance into the control circuit, following Ohms law, reduces the amperage flowing through the control circuit, and the circuit breaker is magnetically held in, closed circuit position with substantially less expenditure of current'.

The operating'structure of the circuit breaker, i. e., the magnetic coil or coils. toggle springs and movable contact, may be used with bimetallic contact members 2l or 02 oivany overload characteristic. This materially simpliiies manufacturing and stocking; for when filling -an order l for a circuit breaker to operate under deilnite portion to the degree o! overload, exerting presloverload ratings, it is only'necessary to select a closure 2 2 with appropriate elements 2t therein, in the Fig. 2 embodiment or plate 93 and elements I2 of the Fig. 10 embodiment, whereupon said structure may be used with the standard housing and operang structure.

As shown in Fig. 2, transformer T may be tion-proof and fully trip-free operation.

The toggle spring throws the amature system with such speed that the armature system may be very light in Weight. The permissible weight reduction of the movable armature sysgization of one of said electromagnets may exert pressure on said second snap spring to throw it to position for circuit closing while simultaneously moving it away from said first-named contacts to maintain the open status of said load circuit.

2. A remote control circuit breaker and overload protective device comprising' a base, electric contacts supported on .said base, electric tem and stable equilibrium of the toggle spring make it a practical impossibility to throw the armature system and therewith associated contact spring by vibrating or shaking the circuit breaker, for the inertia of the armature system is so small in relation to the stability of the toggle spring that an amount of momentum suicient to throw said spring could not be generated by any vibration condition which could be experienced under operating conditions.

The circuit breaker is trip-free in operation because of the stable equilibrium of the contact spring and its property of remaining in open circuit position after the overload has caused its throw to such position The operator cannot restrain the circuit breaker from throwing to open circuit position; nor can he return the circuit breaker to closed circuit status without first throwing the circuit breaker to o position to move the contact toggle spring into its potentially closed circuit status.

Whereas I have described my invention' by reference to specificforms thereof, it will be understood that many changes and modiiicay tions may be made provided they do not depart from the scope of the claims.

I claim:

1. In a remote control circuit breaker and overload protective device, the combination with a base, a plurality of bimetallic strips mounted thereon for connection into an electric circuit, each of said bimetallic strips being secured at one end to said base and having contact means at their respective freel ends, of a pair of solenoid coils adapted to be individually energized in a remote control circuit. an armature system movable toward one or the other of said magnetic coils according to-the energization thereof, a snap spring secured to said armature system to maintain the same in either of its extremes of travel, a second snap spring secured to said armature system, electric contact means carried by said second snap spring and movable into or out of circuit closing association with said first-named contacts according to the movement'of said armature system; said second snap spring having two positions of stable equilibrium, in only one of which positions may the contacts carried thereby engage with said firstnamed contacts; said bimetallic strips, when subjected to a condition of electrical overload, exerting pressure on said second snap spring to throw the same into its other position of stable equilibrium upon the attainment of a predetermined .overload condition, thereby causing said snap spring to carry its said contacts out ci circuit closing association; and means whereby movement of said armature system by ener- -contacts movable into or out of circuit closing engagement with said rst-named contacts to complete the circuit thereacross, electromagnetic means for moving said movable contacts into or out of circuit closing position, said means including a pair of electromagnets, an armature system associated therewith and movable toward one or the other of said magnets according to the energization thereof, a snap spring associated with said armature system to hold, the same at either of its extremes of move-V not be brought into engagement with said contacts, and thermostatic means associated with said ilrst-named contacts and movable toward said second named snap spring under predetermined conditions of overload of the load circuit to snap vthe said spring into its open circuit position of stable equilibrium to thereby move its said contacts out of engagement with said first-named contacts. Y

3. A remote control circuit braker and overload protective device as set forth in claim l, wherein said rst named snap spring has two positions. of stable equilibrium, and wherein said snap spring will remain in a position of stable equilibrium against the pressure of said bimetallic strips and the reaction of said second named snap spring thereby.

4. A remote control circuit breaker and overload protective device, comprising a base, electric contacts positioned on said base, circuit closing contacts movable with respect to said contacts to make or break electrical connection thereacross, electromagnetic means for so moving said circuit closing contacts, a snap spring for resiliently holding said circuit closing contacts in either of their extremes of movement, a second snap spring carrying said circuit closing contacts, said second snap spring having two positions of stable equilibrium, in only one of which positions the circuit closing contacts may be moved into engagement with said rstnamed contacts for closing a circuit thereacross, means whereby said electromagnetic means may cause said second snap spring to assume its potentially circuit closing position, and thermostatic means operating upon said second snap spring when the contacts thereof are in closed circuit position to move said snap spring and therewith associated contacts'into open circuit position upon attainment of a predetermined temperature in said thermostatic means.

5. A remote control circuit breaker and overload protective device, comprising a base, contacts positioned on said base, circuit closing contacts movable with respect to v'said first-named contacts to make or break electrical connection thereacross, electromagnetic means for so moving said circuit closing contacts, a snap spring for resiiientiy holding said circuit closing contacts in either of their extremes of movement, a

second snap spring carrying said circuit closing contacts, said second snap spring having two positions of stable equilibrium, in only one ofv i which positions the circuit closing contacts may sociated contacts into open circuit position upon attainment of a predetermined temperature in said thermostatic means. I

6. A remote control circuit breaker and overload' protective device as set forth in claim 4, in

which said thermostatic means are bimetallic elements secured at one end to said base and said assess? contact between said rst-named contacts and said movable contacts under predetermined temrst-named contacts are carried by the free end of said bimetallic elements.

7. A remote control circuit breaker and overload protective device as set forth in claim 4 in which the circuit closing contacts comprise a ring of electrically conductive material.

8. A remote control circuit breaker and overload protective device as set forth in claim 4, in which the snap spring carrying said circuit closing contacts comprises a dished spring member supported only at its center.

9. A remote control circuit breaker and overload protective device as s et forth in claim 4, in which the snap spring carrying Said circuit closing contacts comprises a dished spring member supported only at its center and the contact carried thereby comprises a ring of electrically cons ductive material loosely secured to said snap spring about its periphery. Y

10. A remote control circuit breaker and overload protective device, comprising a base, con tacts positioned on said base. contacts movable perature conditions.

il. An electric circuit breaker as set forth in claim 14, wherein said snap spring and therewith associated contacts remain in open circuit position after the circuit 'has been broken.

Y 12. A circuit breaker, including contacts for connection into an electric circuit, a rod movable toward or away from said contacts, means for moving said rod, a toggle spring operatively assoi ciated with said rod and movable thereby, said toggle spring having two positions of repose, contact means carried by said toggle spring and arranged thereon in such manner 'that in one posi.. tion of repose of said toggle 'spring the contact means may be brought into or out of engagement with said contacts upon movement of said rod but in a second position of repose of said toggle spring movement of the rod is ineective to bring. the contact means intov engagement with the contacts, and means responsive to a conditionof overload in the electric circuit to move said toggle spring into its' said second position of repose.

13. A remote control circuit breaker and overload protective device as set forth in claim 4, in which the snap spring carrying said circuit closing contacts comprises a dished spring member swivelly supported at its center and the circuit closing contact comprises a ring of electrically conductive material free to rotate about the snap spring supporting means.

4o movable rod and a snap spring supported only by with respect to said first-named contacts to make movable contacts in either of their extremes of movement, a second snap spring assooiatedwith said movable contacts, and means responsive to the temperature of said mst-named contacts and operative upon said second snap spring to break said rod and secured thereto at its center, said snap spring carrying said movable contacts, and means associated with said nxed contacts for moving the said movable contactsv out of engage-- ment therewith in the circumstance of overload at said fixed contacts, said means including a plurality of thermally responsive members adapted to exert pressure against'the outer edges of said snap spring at substantially-diametrically opposite positions thereof as the temperature of said thermally responsive means increases, under overload, to a predetermined point.

` WILLIAM E. STILWELL, Je.

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