US2712044A - Circuit breaker - Google Patents

Description

June 28, 1955 j w, WELSH 2,712,044

CIRCUIT BREAKER Filed Aug. 18, 1953 the vane except at its attachment points thereto.

United States Patent 0 CIRCUIT BREAKER James W. Welsh, Summit, N. L, assiguor t0 Signal-Stat Corporation, Brooklyn, N. Y., a corporation of New York Application August 18, 1953, Serial No. 374,920

13 Claims. (Cl. 200-122) filed August 18, 1953, for Snap Action Device, I have shown and described a novel conductive metal snap action vane which may be incorporated in a snap action switch. This vane is provided with an initial bend about a right line extending across the vane by thinning or deforming the vane along this line in two or more spaced sections of the line, these sections being spaced at their inner ends from the center of the vane and also preferably spaced from the outer ends of the bent line. When such a vane is to be utilized in a snap action switch, such as a flasher, the vane is forcibly bent about another line, at an angle to the line of initial bending by applying force to the ends of such lines of initial bending. When such force is released, the vane snaps back to its initial bent position, the action closely resembling that of a toggle.

With a vane initially deformed in such a manner, the locked up stresses or forces having locii on elliptical lines or zones having radii centered on the center or midpoint of the vane located on the line of initial deformation midway between the inner ends of the spaced of discontinuous deformation. If the vane is held or fixed at a point on one of these locii, the remainder of the vane, during snapping thereof, pivots about such mounting point. The greatest effective force is-exerted at the center of the locii, but very substantial force is also exerted by portions of the vane located on the 'locii at the opposite side of the deformation line from the fixed mounting point.

Such a vane may be effectively used in a thermostatic snap action switch by restraining the vane in the stressdeformed position by attaching a high resistance wire or strip at each of its ends to the vane at the ends of the line of initial bending. This high resistance wire or strip thus forcibly holds the vane in a distorted position bent about a line angularly related to the line of initial bending. When the high resistance wire has electric current passing therethrough, it heats and expands. During the expansion of the wire, a point is reached at which the tension exerted by the wire is overbalanced by the kinetic energy of the vane stored therein by bending the latter from its initial bent condition. At this point, the vane snaps back to its initially bent condition.

When the wire is holding the vane in the stress-deformed position with the vane bent on a line at an angle to the line of initial bending, the wire is spaced from As the wire expands to the point where the vane snaps back to its original pre-set or restored position, the wire snaps into linear contact with the vane. The wire, intermediate its end or vane attachment points, thus moves inward and outward r the snapping action of the la tive to the mounting or pivoting point of the vane. Thereby, a make and break switch action can be prov1dcd by mounting one contact of the switch on the wire intermediate its ends, and mounting the cooperatrve contact in fixed relation to the vane mou pivot point, as by mounting tively rigid bracket or mounting member secured to the vane at a point laterally of the deformation line or on one of the stress contraction locii.

My co-pending application Seriai No. 374,918, filed August 18, 1953, illustrates such a snap action switch or flasher having parameters so that the two contacts are held in full pressure engagement, or even under increasmg pressure, during the time resistance wire is heating and expanding and right up to the instant that the vane shapes back to its preset condition. Thus there 18 no diminution or reduction of contact pressure during the 1nitial part of the switch opening movement or cycle, and full pressure is maintained between the contacts until they are snapped apart by the snap action of the vane in restoring itself to its preset deformation.

More specifically, the switch parameters are so selected that, when the contacts are engaged, and up to the time that the snap action takes place, the resistance element 18 depressed at its center toward the vane, so that the center of the element exerts a force component in the direction of the contact carried by the vane mounting means. By proper selection of the switch parameters, this contact pressure effecting force may be made to increase during the expansion of the resistance wire so that at least full contact pressure is maintained up to the instant the snap action of the vane occurs.

At such instant, the contacts are snapped apart, thus instantaneously moving the contacts from the full pressure engaged position to a widely separated circuit breaking position. Thereby, with such arrangement, a plot of the current flowing across the contacts versus time will essentially resemble a square wave portion of the curve to the current portion of the curve.

The switch shown and described in said application Ser. No. 374,918, is particularly designed as an on-off flasher for lamp circuits, such as the signal lamp circuits of automotive vehicles. Actually, however, such switch is also a very good circuit breaker under complete short circuit conditions, due to its excellent contact-pressuremaintaining, and snap action contact opening and closing characteristics. These characteristics allow the switch to operate satisfactorily even under sever short circuit or overload conditions. However, it has the disadvantage that, when used as a circuit breaker, it will ultimately fail due to burning through of its contacts as the result of its alternating on-ofl' action. While this is not serious from a safety standpoint, as the switch will fail safe in the open contact position, it is desirable, in a circuit breaker, that the contacts, when opened on overload or short circuit, remain open until the condition causing the overload or short circuit is removed.

In accordance with the present invention, a novel modification of the thermostatic switch of said application Ser. No. 374,918 is provided, whereby the latter forms an eflicient circuit breaker which does not require manual re-setting or replacement after a short circuit condition has been cleared. More particularly, the switch actuat ing element comprises a normally contracted, heat expansible element or strip which is indirectly heated by a high resistance wire connected in shunt with the switch contacts. The indirectly heated operating element normally is in a contracted condition constraining the snap action vane to the stress-deformed condition in which a contact mounted on the element is held under high preselative to the vane during tter, and particularly relanting or the vane contact on a relasure engagement with a contact fixed relative to the vane mounting point. Under normal load conditions, the current fiow drawn through the relatively low resistance operating element is insufiicient to heat and expand the same sufiiciently to permit the vane to snap to its pre-set or restored conditions.

However, under short circuit or heavy overload conditions, the substantially increased current flow through the operating element, or pull ribbon, will heat and expand the same to an extent suificient to allow the vane to snap to its restored condition, snapping open the contacts. The current then flows through the high resistance wire and, being relatively high in value, provides sufficient heat to the pull ribbon to maintain the same ex panded. When the short circuit or heavy overload condition is cleared, the reduced or interrupted current flow through the heating wire reduces the heating of the pull ribbon sufliciently to allow the latter to contract to an extent where it snaps the vane back to the stress-deformed condition to re-close the circuit breaker. Thus, no manual re-setting is required.

For an understanding of the invention principles, reference is made to the following descriptions of typical embodiments thereof as illustrated in the accompanying drawings.

In the drawings:

Fig. 1 is a perspective view of a snap action vane and its mounting member as used in the invention switch arrangement;

Fig. 2 is a transverse sectional view of the vane of Fig.

1 with the invention operator and its heating means secured thereto;

Fig. 3 is an elevation view of one form of indirectly heated vane operator embodying the invention view corresponding to Fig. 2;

Fig. 4 is a transverse sectional view on the line 4--4 of Fig. 3;

Fig. 5 is a longitudinal sectional view of another form of indirectly heated vane operator;

Fig. 6 is a transverse sectional view on the line 66 of Fig. 5;

Fig. 7 is an elevation view of still another form of operator embodying the invention;

Fig. 8 is a perspective view of a snap action circuit breaker embodying the invention; and

Fig. 9 is a sectional view on the line 99 of Fig. 8.

Referring to Fig. 1, which is substantially identical with Fig. 10 of my co-pending application Ser. No. 374,976, a snap action vane 10 is illustrated which is identical with that shown and described therein. Vane if; is preferably of relatively thin electrically conductive spring metal, with consideration being given to its spring factor, stillness, temperature coefiicient, and the like, in accordance with the desired rate of operation of the snap action.

To provide an initial set to vane 10 and to give the same some depth so that it will resemble a beam in its action, the vane ltl, which is shown as a substantially rectangular vane, is deformed or thinned along diagonal interconnecting corners 11 and 12. This vane deformation is preferably effected by linearly embossing the vane along the line 11--12 in two elongated spaced portions or bosses 15. It will be noted that the bosses 1.5 have their inner ends disposed substantially equal distances from the center of vane 14) so that the center area of the vane is left unmarred. This greatly prolongs the life of vane 16 by removing the stress concentration from the center to a pair of points on bosses 15. If the deformation line 1112 were continuous through the vane center area, the flattening of the vane at the center during repeated cycles would eventually cause fatigue of the vane at the center and reduce the amount of force required to snap the vane between the illustrated position and another deformed position.

Due to the bosses, 15, 15, the sections 13 and 14 of the cuit for the vane operator.

vane on either side of line 1112 bend upwardly so that the vane assumes the form of a shallow V having its apex on line 1112. When vane bending forces are applied to the end of line 1112, and the value of these forces equals or over-balances the inherent tendency of the vane to stay in its present condition, the vane snaps into a new bent or deformed position, forming another shallow V along the other diagonal 16-17. When the forces at points 11 and 12 are decreased to a point where they are overbalanced by the kinetic energy stored in vane'ltl due to such distorting force, the vane snaps back to a position bent along the line 1112.

Photographs, taken with polarized light, of a transparent vane formed in this manner show lines of force in the unmarred center area of the vane which comprise elliptieal bands having radii centered on the vane center, if the vane is secured or supported at a point on one of these elliptical stress locii, the stress points on the vane during application of bending force at corners 11 and 12 occur within the length of bosses 15. Thus the stresses are removed from the center area and distributed between two points spaced from the center. This greatly prolongs the period before fatigue takes place in the stressed section of the vane.

Advantage is taken of this fact by supporting the vane by electrically and mechanically securing the latter at a point on one of such elliptical lines of force, to a relatively rigid electrically conductive mounting, member or bracket 21?, the point of attachment of the mounting member to the vane acts as a pivot point for the vane during its snap action and is preferably spaced laterally of the initial bend line 11-12.

When the vane is used to form a snap action switch, the bending stresses may be conveniently applied to points 11 and 12 by means of a heat expansible element 40 secured to these corners of the vane. For this purpose, the points 11 and 12 are bent downwardly as illustrated in Fig. 1 and the ends of the element are secured thereto at 31 and 32, while the vane is bent along the line 16-17, so that the element in its cold or contracted position, holds the vane deformed into a V having its apex along lines 16 and 17. If the element is heated, it expands and, as the wire force is overbalanced by the restoring kinetic energy built up in vane 18, the vane snaps back to its initially bent condition along the line 11-12.

in accordance with the invention, an indirectly heated. heat expansible element 40 preferably of conductive metal, is secured, in contracted relation, to the corners 11 and 12 of vane 10, as at the points 31, 32. Such arrangement may be, for example, by soldering or spot welding the ends of element 40 to vane 10 at points 31, 32 and is effected while the vane is stress-deformed about the diagonal 1617. Thereby, when element 40 is heated and expanded a predetermined amount, the

kinetic energy in vane 10 will overbalance the tension of element 40 and snaps the vane to its restored position in which it is bent about the diagonal 11-12. I

The indirect heating is effected by operatively asscciating an insulated high resistance wire 3% with element 40. The length of the wire is independent of the length of element and the parameters of vane 10, and is conditioned solely by the amount of resistance it is necessary or desirable to include in the heating cir- In the embodiment of Figs. 2, 3, and 4, element 40 is a channel shaped strip having resistance wire 30 extending therethrough and with its end brought out of the channel at selected points in accordance with the desired switch contact and circuit arrangements.

Figs. 5 and 6 show an alternative arrangement in which the pull strip secured to vane corners 1 1 and 12 comprises a pair of mating strips or ribbons a, 4515 each having a central groove 46 therealong. An insulated high resistance wire 30 is enclosed'in grooves 1:; 46 and strips 45a, 4511 are then welded together to form a composite pull ribbon 45.

A third embodiment of the indirectly heated pull strip arrangement is shown in Fig. 7. In this instance, the pull strip is an expansible Wire 50 having a dielectric sleeve 51 thereon. High resistance wire 30 which, in this instance, may be bare, is wound helically on sleeve 51.

Figs. 8 and 9 show a snap action circuit breaker embodying the indirectly heated pull strip or ribbon 40 of Figs. 2, 3 and 4, although the pull strips 45 or 50 could equally well be used therein. Bracket 29 has one end secured to the surface of vane 10 having pull strip 40 extending thereover, and at a point laterally of diagonal 11-12 and preferably on one of the elliptical stress locii bands. Intermediate section 22 of the bracket has an insulating strip 23 wrapped therearound and embraced by a band 24 of conductive material. Band 24 carries contact 25 normally engaging a contact 35 on pull ribbon or strip 40. The parameters are so selected that, in the closed position of the circuit L breaker illustrated, strip 40 is bent inward in a shallow V. This increases the pressure of contacts 25, 35 and, as explained in said application Ser. No. 374,918, results in the contact pressure being maintained at full value, or even increased, during expansion of strip 40 and right up to the instant contacts 25, 35 are snapped apart by snapping of vane 10 to its restored position. A conductive strip 26 extends from band 24.

Insulated high resistance wire 30 has one end welded or soldered to vane 10 at point 33 and its other end welded or soldered to band 24 at point 34. Wire 30 is thus in shunt with contacts 25, 35. A grounded battery 56, or other source of potential is schematically illustrated as connected to the end 21 of bracket 20. and a grounded load 55 is schematically illustrated as connected to strip 26. This schematic illustration represents any typical load circuit incorporating the circuit breaker. For explanation purposes, load 55 may represent a short circuit point in the load circuit.

With switch 57 closed, current flows from battery 56 through switch 57, bracket 21, vane 10, strip 40 from both ends to contact 35, contact 25, band 24, strip 26, and load 55 to ground. Due to its high resistance and its shunting by contacts 25, 35, substantially no current flows through wire 30. Strip 40 has a low resistance, so that the heating due to current flow therethrough, under normal load conditions, is insufiicient to expand strip 46 to an extent sufiicient to allow vane 10 to snap to the restored condition.

Assume now that a short circuit or heavy overload condition occurs in load 55 (or at any other point in the circuit). The resultant greatly increased current flow through strip 40 heat the latter rapidly to a point Where it expands sufficiently to allow vane 10 to snap to the restored condition. This will snap contacts 25, open, at least full contact pressure being maintained until the instant of snapping.

With contacts, 25, 35 open, strip would normally contract to snap the vane back to contact closing condition. However, opening of contacts 25, 35 removes the shunt from wire 30, and the latter rapidly heats due to carrying the overload. The current flow, however, is very substantially reduced due to the choking effect of high resistance wire 30. Wire 30 thus heats strip 40 sufiiciently to maintain the strip expanded and preventing re-closing of the circuit breaker contacts.

When the short circuit is cleared, the reduced current flow in wire 30 allows strip 40 to cool and contract to snap vane 10 back to the contact closing position, shunting wire 30. Thus, the circuit breaker automatically re-sets, when the line fault is cleared, without manual attention.

While a specific embodiment of the invention has been shown and described to illustrate the application of the tion may be embodied otherwise without departing from such principles.

What is claimed:

1. A snap action circuit breaker comprising, in combination, a substantially flat vane of resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-dcforrned condition; a pair of normally closed circuit controlling contacts, one carried by the free portion of the vane and the other fixed relative to the vane mounting point; heating means for said element including a circuit controlled by said contacts, said heating means, during normal current flow through the circuit controlled by said contacts, heating said element insuificiently to appreciably expand the same and, during abnormally high current flow through the circuit controlled by said contacts as a result of a circuit fault, heating said element an amount suflicient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and means operable, responsive to opening of said contacts, to maintain the high heating of said element during continuance of the circuit fault.

2. A snap action circuit breaker comprising, in combination, a substantially flat vane of resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; a pair of normally closed circuit controlling contacts, one carried by the free portion of the vane and the other fixed relative to the vane mounting point; heating means for said element including a circuit controlled by said contacts, said heating means, during normal current flow through the circuit controlled by said contacts, heating said element insufficiently to appreciably expand the same and, during abnormally high current flow through the circuit controlled by said contacts as a result of a circuit fault, heating said element an amount sufficient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; a high resistance conductor connected across saidcontacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultinvention principles, it will be understood that the inven- 7'; ant abnormally high current flow through said conductor,

to maintain the high heating of said element during continuance of the circuit fault.

3. A snap action circuit breaker, comprising, in combination, a substantially fiat vane of resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bendingstress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible electrically conductive having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; a pair of normally closed con tacts controlling a circuit including said element, one carried by the free portion of the vane and the other fixed relative to the vane mounting point; said element, during normal current flow through the circuit including said contacts and said element, being heated insufficiently to appreciably expand the same and, during abnormally high current flow through the circuit including said contacts and said element as a result of a circuit fault, being heated an amount sufficient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and means operable, respon sive to opening of said contacts, to maintain the high heating of said element during continuance of the circuit fault.

4. A snap action circuit breaker, comprising, in combination, a substantially fiat vane of resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said'deformation, in directions parallel to said deformation, to effect snapping of the vane between a bendingstress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; a pair of normally closed contacts controlling a circuit including said element, one carried by the free portion of the vane and the other fixed relative to the vane mounting point; said element, during normal current flow through the circuit including said contacts and said element, being heated insufficiently to appreciably expand the same and, during abnormally high current fioW through the circuit including said contacts and said element as a result of a circuit fault, being an amount sufiicient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and a high resistance conductor connected across said contacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultant abnormally high current flow through said conductor, to maintain the high heating of said element during continuance of the circuit fault.

5. A snap action circuit breaker comprising, in combination, a substantially flat vane of resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; a member secured to and mounting said vane at a point spaced laterally from said deformawhereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a b. nding-stress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane Will pivot about such mounting point; a heat expansible electrically conducti- /e element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stress deformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, one carried by said element and the other mounted on said member; said element, during normal current flow through the circuit including said contacts and said element, being heated insutiiciently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts and said element, as a result of a circuit fault, being heated an amount sufiicient to expandthe same to an extent releasing the vane to snap to such initial preset position to open said contacts; and means operable, responsive to opening of said contacts, to maintain the high heating of said element during continuance of the circuit fault.

6. A snap action circuit breaker, comprising, in combination, a substantially fiat vane of resilient material having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; a member secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane Will pivot about such mounting point; a heat expansibie electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element in the stress-deformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, one carried by said element and the other mounted on said member; said element, during normal current flow through the circuit including said contacts and said element, being heated insufliciently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts and said element, as a result of a circuit fault, being heated an amount suificient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and a high resistance conductor connected across said contacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultant abnormally high current flow through said conductor, to maintain the high heating of said element during continuance of the circuit fault.

7. A snap action circuit breaker, comprising, in combination, a substantially fiat vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an electrically conductive member secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stressdeformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stressdeformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said member, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto; said element, during normal current flow through the circuit including said contacts, said element, said member, and said vane, being heated insufficiently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount suiiicient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and means operable, responsive to opening of said contacts, to maintain the high heating of said element during continuance of the circuit fault.

8. A snap action circuit breaker comprising, in com bination, a substantially flat vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an electrically conductive member secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stressdeforrned position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stressdeformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said iember, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto; said element, during normal current flow through the circuit including said contacts, said element, said member, and said vane, being heated insufficiently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount sufficent to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and a high resistance conductor connected across said contacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultant abnormally high current flow through said conductor, to maintain the high heating of said element during continuance of the circuit fault.

9. A snap action circuit breaker comprising, in combination, a substantially flat and rectangular vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross along a diagonal; said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an electrically conductive member secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stresscieformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially and a restored intial preset position, the free portion of the vane Will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stress deformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said member, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto; said element, during normal current flow through the circuit including said contacts, said element, said member, and said vane, being heated insufficiently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount suflicient to expand the same to an extent releasing the vane to snap to such initial pre-set postion to open said contacts; and means operable, responsive to opening of said contacts, to maintain the high heating of said element during continuance of the circuit fault.

10. A snap action circuit breaker comprising, in combination, a substantially flat and rectangular vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an electrically conductive member secured to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stress-deformed position, in which the vane is bent about a line bisecting the line ll of deformation at an angle of substantially 90, and a restored initial preset position, the f ee portion of the vane will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent tne outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stress-deformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said member, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto: said element, during normal current flow through the circuit including said contacts, said element, said member, and said i being heated insufiiciently to appreciably expand the and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount sufficient to expand the same to an extent releasing the vane to snap to such iniiial pre-set position to open said contacts; and a high r sistance conductor connected across said contacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultant abnormally high current flow through said conductor, to maintain the high heating of said element during continuance of the circuit fault.

11. A snap action circuit breaker comprising, in combination, a substantially flat and rectangular vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation and with curvilinear stress concentration locii concentric with the vane center; an electrically conductive member secured to and mounting said vane at a point on one of said locii spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bendiug-stress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the tree portion of the vane will pivot about such mounting points; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stress-deformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said member, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto; said element, during normal current flow through the circuit including said contacts, said element, said member, and said vane, being heated insufficiently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount sufiicient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and means operable, responsive to opening of said contacts, to maintain the iigh heating of said element during continuance of the circuit fault.

12. A snap action circuit breaker comprising, in cornall) bination, a substantially flat and rectangular vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation and with curvilinear stress concentration locii concentric with the vane center; an electrically conductive member secured to and mounting said vane at a point on one of said locii spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bendingstress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in stress-deformed condition; said element, in the stress-deformed condition of the vane, having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said member, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto; the intermediate portion of said element, in the closed position of said contacts, being bent by the latter toward the vane surface to maintain full contact pressure until snapping of the vane to the restored position; said element, during normal current flow through the circuit including said contacts, said element, said member, and said vane, being heated insufliciently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount sufficient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said contacts; and a high resistance conductor connected across said contacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultant abnormally high current flow through said conductor, to maintain the high heating of said element during continuance of the circuit fault.

13. A snap action circuit breaker comprising, in combination, a substantially flat and rectangular vane of electrically conductive spring metal having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of present deformation and with curvilinear stress concentration locii concentric with the vane center; an electrically conductive member secured to and mounting said vane at a point on one of said locii spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a bending-stress-deformed position, in which the vane is bent about a line bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of the vane will pivot about such mounting point; a heat expansible electrically conductive element having its opposite ends secured to said vane at points adjacent the outer ends of said deformation and, in its cool and contracted condition, holding said vane in such stress-deformed condition; said element, in the stress-deformed condition of the vane,

13 having at least its intermediate portion spaced from the surface of said vane and, in the restored position of the vane, lying along the surface of the latter; a pair of normally closed contacts controlling a circuit including said element, said member, and said vane, one carried by said element and the other mounted on said member in insulated relation thereto; the intermediate portion of said element, in the closed position of said contacts, being bent by the latter toward the vane surface to maintain full contact pressure until snapping of the vane to the restored position; said element, during normal current flow through the circuit including said contacts, said element, said member, and said vane, being heated insufiiciently to appreciably expand the same and during abnormally high current flow through the circuit including said contacts, said element, said member, and said vane as a result of a circuit fault, being heated an amount sufficient to expand the same to an extent releasing the vane to snap to such initial pre-set position to open said con tacts; and a high resistance conductor connected across said contacts, and normally shunted thereby, said conductor being in heat transfer relation with said element and operable, responsive to opening of said contacts and resultant abnormally high current flow through said conductor, to maintain the high heating of said element during continuance of the circuit fault; said conductor, upon clearing of such fault with resultant reduced current flow through said conductor, cooling to an extent sufficient for contraction of said element to snap the vane to the stress-deformed position to re-close said contacts.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,837 Lee July 22, 1941 2,286,053 Bletz June 9, 1942 2,616,996 Beeman Nov. 4, 1952

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