US2300530A - Circuit breaker - Google Patents

Description

Nov. 3, 1942. R. H. SWINGLE 2 Sheets-Sheet 2 Filed Feb 26, 1941 INVENTOR Pap/7 /7. 5140')? /e.

ATTORNEY WITNESSES:

Patented Nov. 3, 1942 CIRCUIT BREAKER Ralph n. swin ie, Pittsburgh, Pa., assignor to Westinghouse Electric 3; Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 26, 1941, Serial No. 380,637

13 Claims.

. determined conditions and which cannot reclose until the manually operable handle is manually operated to reset the breaker.

Another object of the invention is the provision of an improved circuit breaker embodying a snapacting thermally responsive element or thermostat which is operable to automatically open the contacts irrespective of the position the manually operable handle.

Another object of the invention is the provision of a circuit breaker having relatively movable contacts which are automatically opened by a snap-acting thermostat and which cannot reclose until the breaker is reset by a manually operable handle, the construction being such that the thermostat is not moved by the handle at any time.

' Another object of the invention is the provision of a circuit breaker having cooperating contacts, one carried by a snap-acting thermostat and the other being biased to an open position and movable by a manual operating handle to a position to be engaged by the contact on the thermostat, the thermostat being operable when heated a predetermined amount to cause movement of both of the contacts away from each other toopen the circuit.

Another object of the invention is the provision of an improved circuit breaker which is simple, compact, sale and reliable in operation, and inexpensive to manufacture.

In accordance with the illustrated embodiments of the invention, the circuit breaker has a pair of cooperating contacts one of which is biased for movement away from the other and restrained by a latch and the other is carried by a snap-acting bimetal element which when heated a predetermined amount operates to move its contact to open position and also release the latch which restrains the first mentioned contact. A manually operable handle is provided for moving the first mentioned contact to latched position to reset the breaker. The operating handle may be arranged to manually open and close the breaker, in addition to resetting the breaker.

after it has been automatically opened by the thermostat.

The novel features that are considered characteristic of the invention are set forth in the appended claims. The invention itseli', however, both as to construction and operation, together with additional objects and advantages thereof will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure l is a sectional view of a circuit breaker constructed in accordance with the invention, the breaker being shown in closed-circuit position;

Fig. 2 is a view similar to Fig. 1, but showing the breaker in the tripped open-circuit position;

Fig. 3 is a sectional view of a circuit breaker constructed in accordance with a modification of the invention, the breaker being shown in the closed-circuit position;

Fig. 4 is a view similar to Fig. 3 illustrating the position 0! the parts when the circuit breaker is manually opened;

Fig. 5 is a view similar to Fig. 3, butshowing the circuit breaker in the tripped open-circuit position;

Fig. 6 is a sectional view of another modification of the invention showing th circuit breaker in closed-circuit position; and

Fig. '7 is a view similar to Fig. 6, but showing the breaker in the tripped open-circuit position.

Referring to Figures 1 and 2 of the drawings, a circuit breaker constructed in accordance with the invention is shown mounted in a casing 9 of molded insulating material which has a cover It oi. the same material removably mounted on the open side. The casing 9 has an insulating support I! therein upon which a stud i5 is centrally mounted. The stud it extends through the center of the support l3 and is retained in mounted position by lock nuts I] which engage a threaded portion of the stud on opposite sides of the insulating support iii.

A snap-acting bimetal disc I9 is non-rotatably secured at its center to the inner end of the stud ii. The bimetal disc has a pair of contacts 2| secured thereto, adjacent the edge, on opposite sides 0! the center of the disc ior engaging the inner ends of a pair of cylindrically shaped movable contacts 23 which movably extend through openings provided therefor in the insulating sup- When the circuit breaker is in closed-circuit position, the current flows through the contacts 2| and 23 and through the bimetal disc is so that the disc is adapted to be heated in response to the current of the circuit.

The snap-acting bimetal disc I! is composed 01' two united discs of sheet metal pressed ,into concave form, the composite piece being capable of being sprung with a snap action from either one of the other of two opposite or reversely flexed positions without having any intermediate position of stability. The metals of the united discs comprising the composite disc II are selected to have diflerent coeiiiclents of thermal expansion and the two parts are proportioned and constructed so that the disc I! will snap from its normal flexed or concave position shown in Fig. 1 to an opposite flexed or concave position shown in Fig. 2 when the disc is heated a predetermined amount by overload current. After the disc has cooled to its normal temperature, it will automatically snap back to its normal flexed or concave position as shown ram. 1.

The insulating bar 25 and the movable contacts 23 are biased outwardly to an open-circuit position away irom the cooperating contacts 2| by means oi a compression spring 3| which encircles the stud I5 and is disposed between the insulating support I3 and the movable insulating bar 25. The insulating bar and its contacts 23 are movable inwardly to a second or normal position, as shown in Fig. l, in which the contacts 23 are adapted to be engaged by the cooperating contacts 2| oi the bimetal disc I! when the bimetal disc is in its normal flexed or concave position, and the insulating bar 25 and the movable contacts 23 carried thereby are adapted to be releasably held in this second or normal position by means of a. pivoted latch 33.

The latch 33 is in the shape of a bell crank lever and is disposed in an opening 35 provided therefor in the insulating support i3. The latch 33 is pivotally mounted on a pivot pin 31 supported by the insulating support I! and the latch is biased to a latched position by a spring 39. One arm of the bell crank latch 33 has a latch nose which is adapted to engage a projection 4| secured to the movable insulating bar 25 whereby the latch normally restrains the insulating bar and moving contacts 23 in the normal position shown in Fig. 1. The other arm ll of the bell crank latch 33 has a link 33 pivotally connected thereto by a pivot pin 32, and the link extends through an opening in an outer portion of the bimetal disc it. A washer or collar 45 is secured to the lower end of the connecting link 43 in a position to be engaged and moved by the snap-acting bimetal disc I! when the disc snaps from its normal flexed position, shown in Fig. 1, to the opposite flexed positionv shown in Fig. 2. The link 43 thus provides a connection between the bimetal disc i3 and the pivoted latch 33 whereby operation of the bimetal disbtin response to predetermined overload conditions effects movement of the latch 33 to released position to release the movable contacts 23 and permit movement thereof to Lipenoircuit position by the spring 3|.

The construction o the circuit breaker is such' that when the contacts are automatically opened by the operation t-the, bimetal disc iii, the movable contacts 23will remain in open-circuit position, as shownj r in Fig. 2, even after the bimetal disc l9 has cfiiled to nrmal temperature, until the circuit breaker is manually reset. A manual operating handle 49 of molded insulating material ls provided for manually resetting the circuit breaker after a tripping operation. The operating handle 49 is slidably mounted on the outer end of the stud l5 by having a central opening 5| which slidably engages the stud. Inward and outward movement of the operating handle 43 is limited by a crosspin 53 on the outer end oi the stud i5 which extends into elongated slots 55 provided in the opposite sides of the operating handle 43. The operating handle 49 extends through an opening provided therefor in the cover ii of the circuit breaker casing and the inner end of the handle is adapted to engage and move the insulating bar 25 and the contacts 23 to the normal or latched position upon inward movement of the operating handle 49.

The operation oi the circuit breaker is briefly as follows. With the circuit breaker in the closed-circuit position shown in Fig. 1, ii an overload occurs on the circuit and persists for a sumcient length of time to heat the bimetal disc a predetermined amount, the bimetal disc operates to snap from its normal flexed position shown in Fig. 1 to the opposite flexed position shown in Fig. 2. This operation of the bimetal disc moves the contacts 2| carried thereby to a position away from the contacts 23 and also moves the pivoted latch 33 to released position to release the spring biased insulating bar 25. When the insulating bar 25 is thus released, the spring 3| moves the bar and its contacts 23 outwardly to open-circuit position, as shown in Fig. 2. It will thus be seen that the operation of the bimetal disc I! causes movement of both sets of contacts 2| and 23 away from each other to open-circuit position. The movement of the insulating bar 25 and movable contacts 23 to open-circuit position eflfects movement of the operating handle 49 outwardly to its open position, thus indicating that the circuit breaker has been tripped. The circuit breaker is trip-free since holding the operating handle in closed position cannot prevent the bimetal disc from acting to move its contacts 2| to an open position away from the contacts 23 on the insulating bar 25.

After the bimetal disc I! has cooled to normal temperature, it automatically snaps back to its normal flexed position. This does not reclose the circuit breaker, however, since the contacts 23 carried by the insulating bar 25 are still in their open-circuit position. To reset and reclose the circuit breaker, the operating handle 49 must be manually moved inwardly to closed position. This movement of the operating handle 49 moves the insulating bar 25 and the contacts 23 to their normal or latched position wherein they are releasably held by the pivoted latch 33. The circuit breaker cannot be reset or reclosed, however, until the bimetal disc i9 has cooled and returned to its normal flexed position, since when the b metal disc is in its inverted position, the latch 33 is held in released position and the contacts 2| in an open-circuit position. If the bimetal disc I! has cooled and returned to its normal flexed position, manual movement of the operating handle 49 inwardly returns the movable contacts 23 to their normal position in engagement with the cooperating contacts 2|, and the movable contacts 23 are releasably held in closed position by the latch 33.

Although the bimetal disc l9 has been de-' scribed as being heated in response to the current flow in'the circuit and operable in response to predetermined overload conditions, the bimetal disc may be arranged to be heated in response to the temperature of the device which it controls, instead of by the current flow through the disc. Also, the contacts 2| carried by the bimetal disc l9 may be insulated from the disc and have a heating coil connected therebetween to heat the bimetal element.

A modification oi the invention is shown in Figs. 3, 4 and 5. In this modification, the construction of the circuit breaker is identical to that of the original embodiment described above except that a manual operating handle is provided which is operable to manually open and close the contacts in addition to resetting the breaker after a tripping operation. The parts of the circuit breaker which are identical to the corresponding parts of the circuit breaker shown in Figs. 1 and 2 have been indicated by the same reference characters. Referring to Figs. 3, 4 and 5, the circuit breaker is provided with an operating handle 58 o! molded insulating material which is pivotally mounted on the outer end of the stud |5 by a pivot pin 60. The operating' handle, in addition to having a handle portion by which it is'manually operated, has an arm 62 extending on one side of the pivot 60 for engaging and moving the insulating bar 25 inwardly to its normal position to manually close or reset the circuit breaker when the operating handle is moved in a clockwise direction to its closed or on position. The operating handle 58 is also provided with a second arm 84 extending on the opposite side of the pivot 88, and this arm is adapted to engage and depress a rod 85 connected to the pivoted latch 33 to effect release of the insulating bar 25 and contacts 23 when the operating handle is moved in a counterclockwise direction to its open or ofi" position, thus causing movement of the movable contacts 23 to open-circuit position. The rod 86 extends through an opening provided therefor in the insulating bar 25 and the lower end of the rod is pivotally connected to the arm 48 of the latch 33 by the same pivot pin 42 which connects the link 43 to the latch. i

The operation of this modification of the invention is briefly as follows. Assuming the circuit breaker to be in the open-circuit position shown in Fig. 4, to manually close or reset the breaker, the operating handle 58 is moved in a clockwise direction to closed position. This movement of the handle moves the insulating bar 25 and movable contacts 23 inwardly to the normal or latched position shown in Fig. 3, wherein the contacts 23 engage the cooperating contacts 2| on. the bimetal disc iii. The insulating bar 25 and movable contacts 23 are releasably held in closed position by thepivoted latch 33 against the force of the circuit opening spring 3|.

To manually open the circuit, the operating handle 58 is moved in a counterclockwise direction to its open or off" position. During this movement of the operating handle the arm 84 thereof engages and depresses the rod 68 connected to the latch 33 and thus moves the latch to released position to release the insulating bar 25. As soon as the insulating bar 25 is released, the spring 3| moves the insulating bar and its contacts 23 outwardly to open circuit position, thus opening the contacts of the breaker.

The automatic operation of the circuit breaker in response to predetermined overload conditions is substantially the same as in the original embodiment previously described. When the bimetal disc I! has been heated a predetermined amount by overload current, it operates to snap from its normally flexed position, shown in Fig. 3, to the oppositely flexed or inverted position shown in Fig. 5. This operation 0! the disc moves the contacts 2| to open position away from the cooperating contacts 23 and also moves the pivoted latch 33 to the released position to release the movable insulating bar 25. When the insulating bar 25 is thus released, the spring 3| moves the bar 25 and its contacts 23 outwardly to open-circuit position, as shown in Fig. 5. After the bimetal disc I8 is cooled to normal temperature, it automatically returns to its normal flexed posi tion. This does not reclose the circuit breaker, however, since the contacts 23 carried by the insulating bar 25 are still in their open-circuit position, so that the breaker cannot be reclosed until it has been manually reset by the operating handle.

To reset or reclose the breaker, the operating handle 58 is moved in a clockwise direction to its closed or on position. This movement of the operating handle causes the arm 82 oi the handle to engage and move the insulating bar 23 and movable contacts 23 inwardly to their normal or latched position, as shown in Fig. 3, thus reclosing the contacts of the breaker. The circuit breaker is trip-tree since holding the operating handle 58 in closedfp'osition cannot prevent the bimetal disc l8 from moving its contacts 2| to open position away from the contacts 23 when the disc is heated a predetermined amount and snaps to its inverted position.

I! desired, the operating'handle 58 may be biased in a clockwise direction toward its closed position by a light spring 68 so as to maintain the arm 82 oi the operating handle-in engagement with the movable insulatingfi'bar 25. The light spring 68 resiliently maintains the operating handle 58 in closed position when the circuit breaker is in closed position. However, if the contacts are manually opened by operation of the handle 88 or automatically opened by operation of the bimetal disc i8, the outward movement of the insulating bar 25 causes the operating handle 58 to assume an intermediate indicating position to indicate that the circuit breaker is open, thus the operating handle serves to indicate the position or the breaker.

A further modification or the invention is shown in Figs. 6 and '7. In this modification, the circuit breaker is mounted in a casing 88 of molded insulating material which has a cooperating cover 1| ot the same material removably secured to the open side thereof. A snap-acting disc 13 of bimetallic material is mounted within the casing 63 with its edge bearing against a circular shoulder 15 formed in the casing. A plurality of cap screws 11 threaded into the shoulder 15 serve to retain the bimetal disc in mounted position. The cap screws 11 extend through openings or slots I8 provided therefor in the edge of the bimetal disc 13, the arrangement being such as to provide a limited amount of movement of the edge of the disc relative to the cap screws 11 so as to permit the bimetal disc to snap freely from either one to the other of two oppositely flexed positions without any binding action by the screws 11. The bimetal disc 13 is composed of two united discs of sheet metal pressed into concave form, the composite piece being capable of being sprung with a snap action from one to the other of two opposite or reversely flexed positions. The metals oi the united discs comprising the composite disc II are selected to have diflerent coefllcients of thermal expansion and the two parts are constructed so that the disc I! will snap from its normal flexed position shown in Fig. 6 to an opposite flexed or inverted position shown in Fig. '7 when the disc is heated a predetermined amount. After the disc has cooled to its normal temperature. it will automatically snap back to its normal flexed position. The bimetal disc I! has a contact 8! mounted thereon at the center the disc for engaging a cooperating contact 08 which is mounted on a spring arm ll oi conducting material. One end of the spring arm I is secured to the casing 69 and the end which carries the movable contact I is normally held down by a pivoted latch 81. The latch .II is pivotally mounted on a pivot pin 89 supported by the casing I and is biased to latching position by a relativew light spring 9|. One arm oi the latch I! has a latch nose which is adapted to engage the iree end oi the spring arm II and the other arm of the latch has a link Bl pivotally connected thereto which extends through an opening provided thereior in the bimetal disc II. A washer or collar 95 is secured to the lower end oi the link 98, beneath the bimetal disc ll so that when the bimetal disc snaps from its normal position to its opposite or inverted position, it will cause movement of the latch 81 to released positions to effect release of the spring arm ll and movable contact 8!.

An operating handle or push button 91 or molded insulating material is slidably mounted in an opening provided therefor in the cover Ii 0! the casing for resetting or reclosing the'circuit breaker after it has been automatically tripped open by the bimetal disc 13. The lower end 01' the push button or handle I1 i adapted to engage and move the spring arm 85 and the movable contact ll back to the normal latched position, as shown in Fig. 8, when the handle 91 is manually depressed.

The snap-acting bimetal disc 13 is adapted to be heated in response to the current or the circult by a separate electrical heating resistance II which is disposed within the casing 68 directly below the bimetal disc 13. One end of the electrical heating resistance 99 is electrically connected to a terminal ill mounted at one end of the circuit breaker casing and the other end of the heating resistance is connected by a flexible shunt conductor II! to the movable contact I! which is insulatively mounted on the center portion of the bimetal disc. One end of the spring contact supporting arm 85 extends outside of the casing N to form the other terminal of the circuit breaker.

The operation of the circuit breaker is briefly as follows. When the circuit breaker is in the closedcircuit position, as shown in Fig. 6, and an overload occurs which persists for a suflicient length oi time to heat the bimetal disc 13 a predetermined amount, the disc 13 snaps i'rom its normal flexed position to an opposite flexed or inverted position as shown in Fig. 7. This operation oi the bimetal disc 11 moves the contact 8i carried thereby to an open position away from the cooperating contact 83 and at the same time operates to move the latch 81 to released position to eflect release oi the spring arm 85. When the spring arm 85 is thus released, it moves outwardLv to the position shown in Fig. 6 causing movement of the contact 83 to an open-circuit position.

also moves the push-button operating handle I! outwardly to open position to indicate that the circuit breaker has been automatically opened.

After the bimetal disc 13 has cooled to its normal temperature, it snaps back to its normal flexed position. This does not reclose the circuit breaker, however, since the cooperative contact 83 carried by the spring arm 85 is still in its open- This movement of the spring arm ll circuit position and the circuit remains open. To reset the'circuit breaker, the push-button handle 91 ismanualiy moved inwardly and this movement of the handle returns the spring arm and contact 83 back to their normal latched position in which the arm 88 is re-engaged and held by the latch 81 and the contact 83 engages the cooperating contact I I.

The circuit breaker is trip-free since holding the push-button handle down cannot prevent the bimetal disc 13 from moving its contact ll to open position away from the contact 83 when the disc is heated a predetermined amount and snaps to its inverted position.

It will be noted that in each of the embodiments of the invention, the bimetal element or disc is not moved by the operating handle. This is an important advantage over prior art constructions where the bimetal disc is manually moved by the operating member. Manual movement oi the bimetal element or disc is undesirable as it may strain the element and change its opcrating characteristic, particularly when the bimetal element is still hot and is forced overcenter.

While theinvention has been disclosed in accordance with the provisions oi. the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from some of the essential ieatures oi the invention. It is desired, therefore, that the invention be limited only by the reasonable construction oi the language of the appended claims.

I claim as my invention:

1. A circuit breaker comprising a pair oi separable contacts, operating means therefor comprising manual means for moving at least one 0! said contacts to close the breaker. and means including a snap acting thermally responsive element operable in response to predetermined conditions to cause movement of both oi said contacts away from each other to automatically open the circuit.

2. A circuit breaker comprising a pair 01 separable contacts, opcrating means thereior comprising an operating member i'or moving at least one of said contacts to close the breaker, and means including a snap acting thermally responsive element operable in response to predetermined conditions to cause movement of both of said contacts away from each other to automatically open the circuit, said thermally responsive element wl'icn operated causing opening of said contacts irrespective of the position oi. said thermally resprioisive element cools to its normal temperature.

4. A circuit breaker comprising a first movable contact, operating means including an operating member for moving said contact, a snap acting thermally responsive element, a second contact carried by said element for engaging said first contact, said thermally responsive element when heated a predetermined amount operating to cause movement of both of said contacts away from each other to automatically open the circuit.

5. A circuit breaker comprising a pair of separable contacts, one of said contacts being biased to an open position away from the other, a latch for releasably restraining said one contact in a position to be engaged by the other contact, an operating member for moving said one contact to latched position, and a snap acting thermally responsive element operable in response to predetermined conditions to move said other contact away from said one contact and to cause said latch to release said one contact.

6. A circuit breaker comprising a pair of separable contacts, means biasing one of said contacts to an open position away from the other contact, a latch for releasably restraining said one contact in a position to be engaged by the other contact, a snap acting bimetal element heated in response to the current of the circuit for controlling said contacts, said bimetal element when heated a predetermined amount operating to move said other contact away from said one contact and causing said latch to release said one contact.

7. A circuit breaker comprising a pair of separable contacts, one of said contacts being movable to an open position away from the other contact and to a second position to be engaged by the other contact, a snap acting bimetal element carrying the other contact, said bimetal element being operable in response to predetermined conditions to 'cause movement of both of said contacts away from each other to automatically open said contacts, said one contact remaining in open position until manually operated to its second position.

8. A circuit breaker comprising a pair of separable contacts, one of said contacts being biased to open position away from the other and movable to a second position to be engaged by the other contact, means for releasably restraining said one contact in its second position, a snap acting bimetal element carrying the other contact, said bimetal element being heated in response to the current of the circuit and operable when heateda predetermined amount to cause movement of both contacts away from each other to automatically open the contacts, and an operating member operable to move said one contact to its second position.

9. A circuit breaker comprising a pair of spaced contacts carried by a movable insulating member, a snap acting bimetal disc supported at its center on a fixed support and having a normal flexed position, a. pair of contacts carried by said bimetal disc adjacent the edge thereof for engaging the contacts on said insulating member, spring means biasing said insulating member to an open position in which the contacts thereof are away from the contacts on said bimetal disc means for releasably restraining said insulatingmember in a second position in which the cbntacts thereon are engaged by the contacts on said bimetal disc in the normal flexed position of the disc, said bimetal disc being heated in response to the current of the circuit and operable when heated a predetermined amount to snap from its normal flexed position to an opposite flexed position to move its contacts away from the contacts of said insulating member and to effect release of said insulating member, and handle means for moving said insulating member to its second position.

10. A circuit breaker comprising a pair of separable contacts, one of said contacts being mounted on a spring arm and biased thereby to an open position away from the other contact, a latch for'releasbly restraining said one contact in a second position to be engaged by the other contact, an operating handle for moving said one contact to its second position, a snap acting bimetal element carrying the other contact, said bimetal element when heated a predetermined amount operating to move the contact carried thereby away from said one contact and causing said latch to release said one contact.

11. A circuit breaker comprising a pair of separable contacts, operating means including an operating member manually operable to move one of said contacts to an open position away from the other contact and to a second position to engage the other contact, a thermally responsive snap acting element for moving the other contact, said thermally responsive element being operable in response to predetermined conditions to cause movement of both of said contacts away from each other to automatically open the circuit.

12. A circuit breaker comprising a pair of separable contacts, one of said contacts being biased to an open position away from the other contact, means for releasably restraining said one contact in a second position to be engaged by the other contact, a snap acting bimetal element carrying the other contact, said bimetal element being operable in response to predetermined conditions to cause movement of both or said contacts away from each other to automatically open the circuit, and an operating member manually operable to cause movement of said one contact to said open position or to said second pos tion to manually open and close the circuit.

13. A circuit breaker cmprising a pair of separable contacts, one of said contacts being biased to an open position away from the other contact, a latch for releasably restraining said one contact in a second position to be engaged by the other contact, a snap acting bimetal element carrying the other contact, said bimetal element being heated in response to the current of the circuit and operating when heated a, predetermined amount t move the contact carried thereby away from said one contact and to cause said latch to release said one contact, and a movable operating handle operable to cause said latch to release said one contact to cause movement thereof to open position and operable to move said one contact to its second position to manually close the circuit.

RALPH H. SWINGLE.

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