US2579252A - Circuit breaker - Google Patents

Description

vDee. 18, 1951 L E FISHER 2,579,252

CIRCUIT BREAKER Filed Feb. 5, 1945 2 SHEETS-SHEET l Dec. 18, 1951 E. FISHER 2,579,252

CIRCUIT BREAKER Filed Feb. 5. 1945 2 SHEETS-SHEET 2 mzlllnlzq.

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ww @M Patented Dec. 18, 1951 CIRCUIT BREAKE Lawrence E. Fisher, Detroit, Mich., assigner to BullDog Electric Products Company, Detroit, Mich., a corporation of West Virginia Application February 5, 1945, Serial No. 578,171 3 claim.. (ci. zon-11s) This application relates to overload release circuit breakers, generally, and `more specifically concerns an improved overload release mechanism that is particularly adaptable to the type circuit breaker disclosed in U. S. Patent No. 2,385,727 issued on September 25, 1945, to Elwood T. Platz.

In the type of circuit breaker described in the aforementioned patent, the release mechanism includes a releasable latch consisting of a bimetal latching element having a portion thereof arranged in overlapping relation with an abutment. On the occurrence of a temperature rise such as would be occasioned by an overload in the circuit, the overlapping portion of the bimetal tends to work away from the abutment and, being spring loaded, frees itself from the abutment to thereby release a contactor. In such devices the latching element tends to work away from the abutment on any temperature rise, regardless of whether that temperature rise is caused by ambient temperature, by heating due to prolonged moderate overload, or by a momentary excessive overload in the controlled circuit. As release characteristics are dependent. among other things, upon 25 the amount of overlap between the bimetal and the abutment, it is desirable to prevent the overlap from changing except on temperature rise occasioned by overload. Since the amount of overlap also affects thespeed of opening of the circuit breaker and as it is desirable to have the circuit opened rapidly on the occurrence of an excessive overload of large magnitude, it is also `desirable to have as small an amount of overlap as possible. v

In order to obtain faster opening than is possible in circuit breakers having bimetal latching elements alone, an over-controlling magnetic release has been supplied in circuit breakers which release is adjusted to cause faster release in the desired range of overload. See for example, copending application Serial No. 724,430, filed on January 25, 1947, in the names of William H. Frank, Elwood T. Platz, and Russell S. Davis, and assigned to the assignee of the present application. However, such combinations require more space and materials and are more expensive to produce than the type using only bimetallic elements. Moreover, the effects of ambient temperature on the bimetal elements of the known combinations, acts to alter the speed of release in the range of overloads when release is eifected by working of the bimetal elements in the release direction.

Therefore, a primary feature of the present invention is the provision of a novel latching arrangement for circuit breaker. that permits a wide range of choice of release characteristics. A further feature of the present invention is the provision of a bimetal latching arrangement for a circuit breaker that maintains a predetermined release characteristic irrespective of variations of the ambient temperature at the circuit breaker. A further feature is in the provision of an improved bimetal latching arrangement for circuit breakers that provides a very quick trip when the circuit breaker is closed on an existing overload. A still further feature of the present invention resides in the provision of a bimetal latching arrangement wherein two bimetals are provided and they are arranged to provide slow release on moderate overloads and quick release on excessive overloads. These and other features of the present invention will become apparent from the description of the drawings wherein:

Fig. 1 is a fragmentary view of the circuit breaker in a closed position and including a preferred embodiment of the present invention.

Fig. 2 is a view along the lines A-A of Fig. 1. Fig. 3 is a view along the lines of B-B of Fig. 1. Fig. 4 is a fragmentary view of the circuit breaker of Fig. l in a'tripped, or opened circuit position.

Fig. 5 is aview along the lines C-C of Fig. 4. Fig. 6 is a view along the lines D-D of Fig. 4. Fig. 7 is a perspective of the circuit breaker of F18. 1.- Referring now to Fig. 1 of the drawings, the circuit breaker mechanism is illustrated as being enclosed in a case Il, and as having a construction and mechanism. the major parts of which, are much similar to the mechanism of the aforementioned Patent No. 2,385,727. This construction and ymechanism includes the line terminal I4 secured to the case I0, and arranged to support the stationary contact 44. A movable contactor 50, carrying the contact 48, is pivoted by the rivet 5| to permit the contact 48 to make butt contact with the stationary contact Il. The movable contacter 50 has an L-shaped portion having a lug 58 for holding compression spring 5i, which in turn is seated in the spring seat 30 of casing Il. The spring 56 not only acts to coerce the movable contacter 50 in a counterclockwise direction, but also serves to coerce the lug I8 and the movable contacter 50 toward the insulation holding plate il. Also as in the aforementioned patent, rigidly secured to the movable contact 5I. by means of the rivet Si, is a bimetallic lachlnl element l2, which, in the mamada s latched position illustrated in Figs. 1', 2, and .3, has a hook 60, formed of an edge thereof, abut ting against the abutment edge 5| formed of the insulation holding plate 53. As'the spring 56 tends to coerce the movable contacter 55 towards the insulating holding plate 53, it also tends to force the bimetal 52 towards the plate 53. In order that the bimetal 52 may be sensitive to the amount ci current through the circuit breaker, the current is transmitted through it, by means of the exible loop 55, and thusly, when an overload occurs. heating takes-place in the bimetallic strip 52 and it tends to warp away trom the plate 53. However, the spring 55 also tends to force the hook 55 to the right, as viewed in Fig. 3. Hence the amount of overlap o the hook 55 on the abutment edge 5| of plate 53 is determined by the adjusting screw 25|, which is carried by member 200 rigidly secured to moveable contact 50 by rivet 5|. The hook 50 o! bimetal 52 must warp the amount of the overlap in order to be treed of the abutment edge 5|. In other words, the current passing through the bimetal element 52, must be of a value (on overload) to heat the element 52 to cause it to warp an amount suillcient tolmove the hook 50 (to the lett as viewed in Fig. 3) free of the abutment edge 6|, whereupon the spring 55 moves the movable contact and its lassociated elements 52 and 205 to the tripped or open circuit position illustrated in Figs. 4, 5. and 6.

From the above description, it can be seen that the position of the adjusting screw 20| determines the distance that the hook 55 must travel away from the plate 53, before the circuit breaker will trip to the open circuit position. As the spring 5 5 coerces the bimetal 52 and the hook 60 toward the plate 55, the screw 20|, in resting on the plate 53, limits the amount which the hook,

this construction, as the bimetallic strip 52 tends v to warp and alter its release characteristics through altering the amount of overlap between the hook and the abutment edge 5|, as the second bimetal element 200 also tends to warp,

in response to ambient temperature, in the same temperature compensating strip 255 does not e have time to operate. Hence the strip E2 may be considered a quick or rapid actingbimetal, while the strip 200 a slow acting bimetal.

In addition to maintaining the proper release characteristics notwithstanding ambient temperature variations, a further advantage is derived from the construction set forth. It an attempt is made to close, or latch the breaker on an existing overload, the strip 52 will be caused to heat and warp. but this condition will not be transmitted to the strip 200. as the time element is too short to permit heat transfer and subsequent warping of bimetal strip 200. Thus, the strip 200 not only derives one advantage from being positioned close to the bimetal strip 52, whereby the ambient temperature of the strip 52 will be accurately reected in the strip 200, but

also this proximity does not become a disadvantage. upon the occurrence of an excessive overload.

Iclaim:

1. In an overload release circuit breaker, a xed contact, a movable contact, a member carrying said movable contact and mounted to move the latter into and out of engagement with said iixed contact, means urging said member in a dlrection to separate said contacts, a bimetallic latching element secured to said member, an abutment arranged normally to block contactopening movement of said latching element and said member, said latching element being in circuit'with said contacts to be ywarped free of said abutment upon passage of an overload current, means urging said latching element in the direction of increased overlap with respect to said abutment, and a bimetallic ambient-temperature compensating element arranged adjacent said latching element and disposed to contact the same so as to maintain constant the amount of overlap between said latching element and said abutment irrespective of changes in ambient temperature.

2. The device in accordance with claim 1, in which a single spring constitutes the means for urging said member in contact-opening direction and the means for urging said latching element in the direction of increased overlap.

3. The device in accordance with claim 1, lin which said'compensating element is disposed in heat-receiving relation to said latching element whereby it will operate to slow down the unlatching movement of said latching element for moderate overloads without affecting the speed of Aunlatching movement for excessive overloads.

LAWRENCE E. FISHER.

REFERENCES CITED I .The following references are of record in the ille -of this patent:

s UNITED STATES PATENTS Number Getchell Dec.`7, 1948

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