GB2221346A

GB2221346A - Circuit breaker trip bar bearing

Info

Publication number: GB2221346A
Application number: GB8917009A
Authority: GB
Inventors: Jr James Norman Altenhof; Melvin Allan Carrodus; Alfred Eugene Maier; Andrew James Male
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1988-07-25
Filing date: 1989-07-25
Publication date: 1990-01-31
Also published as: GB8917009D0; BR8903655A

Abstract

A trip bar 51 of a circuit breaker is mounted for rotation about its longitudinal axis by a support member 57, one of the trip bar 51 and the support member 57 having tapered edges 65, 67 and the other of the trip bar 51 and the support member 57 having a notch 61, 63 receiving the tapered edges 65, 67. <IMAGE>

Description

CIRCUIT BREAKER TRIP BAR BEARING This invention relates to a multiphase circuit breaker and, more particularly, it pertains to a bearing structure for a trip bar.

In the circuit-interrupting art, compact circuit breakers have evolved that comprise overcurrent protective devices, or trip units, that function in response to such abnormal currents as overcurrents, ground fault circuits, and short circuits that occur in an electrical distribution system. Such a trip unit is disclosed in U.S.

Patent No. 4,691,182. This circuit breaker includes trip bars having round bearing surfaces and are mounted in round holes formed by two parts including the base and cover of the circuit breaker housing when assembled together. A problem with such bearings has been friction due to variation in part dimensions, warpage, and accumulation of debris, as well as variation in location of the center of rotation of the trip bar due to clearances required because of manufacturing tolerances on part dimensions.

STATEMENT OF THE INVENTION In accordance with this invention, it has been found that a multiphase circuit breaker may be provided which comprises a pair of separable contacts operable between open and closed positions, an operating mechanism for operating the contacts and comprising a pivotally supported releasable member, latching means for latching the releasable member and including a latch lever, trip means including a trip bar for releasably mounting the latch lever in the latched position, means for pivotally mounting the trip bar for rotation about its longitudinal axis and including pivot support members within the housing, one of the trip bar and members having tapered pivot edges and the other of the trip bar and members having tapered pivot edge-receiving V-shaped notches, the notches being on the side of the trip bar opposite the latch lever, and means for tripping the trip bar in response to predetermined overcurrent conditions.

The advantage of the device of this invention is that it reduces friction that otherwise occurs between the trip bar and the mounting means for its rotation and it provides a more precise location for the pivot point of the trip bar.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more readily apparent from the following description of a preferred embodiment thereof shown, by way of example only, in the accompanying drawings, wherein: Figure 1 is a vertical sectional view through a multipole circuit breaker; Figure 2 is an isometric, exploded view of the trip bar of this invention; and Figure 3 is a fragmentary sectional view showing another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In Fig. 1, a circuit breaker is generally indicated at 7 and it comprises a molded case or housing having an insulating base 9 and an insulating cover 11 which are separable at a parting line 13. An operating mechanism, generally indicated at 15, was disposed within the housing and includes a latch 17 and a trip unit 19.

Generally, the circuit breaker 7 operates similar to the types described in U.S. Patents Nos. 4,691,182 and 4,698,606. The circuit breaker 7 is a three-pole circuit breaker comprising three compartments disposed in side-byside relationship in a manner well known in the art. The center pole compartment (Fig 1) is separated from two outer pole compartments by insulating barrier walls formed with the housing base and the cover. The operating mechanism 15 is disposed in the center pole compartment and is a single mechanism for operating the contacts of all three pole units.

Each pole unit comprises a stationary contact 21 that is fixedly secured to a rigid main conductor 23 that in turn is secured to the base 9 by screws (not shown).

In each pole unit a movable contact 25 is secured, such as by welding or brazing, to a contact arm 27 that is mounted on a pivot pin 29. The arm 27, for all three of the pole units are supported at one end thereof and rigidly connected to a common insulating tie bar 31 by which the arms of all three pole units move in unison. Each of the contact arms is biased about the associated pivot pin 29.

The operating mechanism 15 actuates the contact arms 27 between open and closed positions, and it comprises a pivoted, formed operating lever 33 and a pivoted releasable cradle or arm 35 which is controlled by the latch 17. An insulating shield 37, for closing an opening 39 in the cover 11, is mounted on the outer end of the operating lever 33 and has an integral handle 41 extending through the opening to enable manual operation of the breaker. The operating mechanism 15 also includes an toggle mechanism of conventional construction (not shown).

The trip unit 19 serves to effect automatic release of the releasable cradle or arm 35 and opening of the breaker contacts for all of the pole units, in response to predetermined overload conditions in the circuit breaker through any or all pole units of the circuit breaker. A circuit through the circuit breaker 7 extends from a line terminal (not shown) at the left end of Fig. 1 through the conductor 23, the contacts 21, 25, the contact arm 27, a shunt 43, a conductor 45 to a terminal (not shown) on the right side of the circuit breaker. For a more complete understanding of the terminals at the left and rights sides of the circuit breaker 7 (Fig. 1), reference is made to the abovementioned U.S. Patents 4,691,182 and 4,698,606.

As shown in Fig. 1, the trip unit 19 comprises a molded insulating housing base 49 and a molded insulating housing cover 47 secured to the base to enclose a molded insulating trip bar 51 that is common to all three of the pole units.

In accordance with this invention, the trip bar (Fig. 2) is an elongated member having spaced notches 53, 55 by which the notches are pivotally mounted on spaced support members 57, 59 which extend from and are preferably integral with the molded insulating housing cover 47.

Each notch 53, 55 comprises a pair of tapered pivot edges 61, 63 for receiving similar tapered pivot surfaces 65, 67 of the support members 57, 59, respectively. The angle encompassed by the tapered or wedge-forming surfaces 65, 67 (Fig. 1) is smaller than the angle between the tapered surfaces 61, 63, so that the trip bar 51 is rotatable in place on the apexes of the tapered surfaces 65, 67. The edges 61, 63 are disposed on the axis of rotation of the elongated trip bar 51. It is noted that inasmuch as there is space between the tapered edges 61, 67 and 63, 65, on opposite sides of the support members 57, 59, the trip bar 51 is free to rotate through limited arcs on opposite sides of the support members.

When the circuit breaker is in the closed condition (Fig. 1) with the contacts 21, 25 in engagement, the trip bar 51 is in the position shown in Fig. 1 with a latch lever 69 in engagement with a surface 71 of a latch leg 73, whereby the latch lever is retained against clockwise rotation about a pivot pin 75. Thus, the releasable arm 35 is retained in its latch position.

The conductor 45 includes a U-shaped portion 77 on one leg of which is mounted a bimetal 79 by suitable screws 81. The upper end of the bimetal is provided with a set screw 83 for engagement with an arm 85 when the bimetal deflects clockwise in response to any heating thereof by overcurrents passing through the conductor U shaped portion 77.

In addition, the U-shaped portion 77 constitutes a single loop of a stationary magnet which comprises a magnetic core 87 and an armature 89. The upper end of the armature 105 is pivotally mounted in a holding bracket 91 and is biased in a counterclockwise direction by a coil spring 93. The armature has a projection 95 and is movable clockwise to rotate an extension 97 of the trip bar 57 clockwise. When an overload current above a value such, for example, as five times normal rated current or a short circuit current occurs, the stationary magnetic structure is energized and the armature 89 is attracted toward the core 87, causing release of the arm 35 and opening of the contacts 21, 25.A calibration screw 99 is provided in the housing cover 49 for adjusting the spacing between the armature 89 and the core 87, whereby upon maximum spacing of the armature from the core a greater current overload is required to attract the armature toward the core.

Another embodiment of the invention is shown in Fig. 3 in which similar numerals refer to similar parts.

In this embodiment, a support member 101 includes a Vshaped groove 103 which is provided by inclined surfaces 105, 107 to form an apex 109. A trip bar 111 comprises a tapered member having inclined surfaces 113, 115 which converts to form a pivot point disposed in the apex 109.

The apex 109 is disposed in the longitudinal rotatable axis of the trip bar 111. Accordingly, portions 117, 119 of the trip bar 111 are spaced from the opposite sides of the support member 101 to enable rotation of the trip bar 111 under overcurrent conditions set forth hereinabove.

Accordingly, the support member 109 provides a tapered pivot edge receiving notch for the tapered pivot edges of the trip bar 111.

In conclusion, the trip bar bearing of a circuit breaker provides for a limited rotation of a trip bar which is not susceptible to warpage or variations in dimensions of the several parts involved. Finally, the trip bar does not require lubrication to enhance its operation.

Claims

CLAIMS:

1. A circuit breaker comprising: a pair of separable contacts operable between open and closed positions; an operating mechanism for operating the contacts and comprising a pivotally supported releasable member; a latching member for latching the releasable member and including a latch lever; a trip member including a trip bar for releasably mounting the latch lever to the latched position; characterized by a pivoting member for pivotally mounting the trip bar for rotation about its longitudinal axis and including pivot support members within the housing, a first trip bar end members having tapered pivot edges and another trip bar end member having tapered pivot edge receiving notches; and an operating member for tripping the trip bar in response to predetermined overcurrent conditions.

2. The circuit breaker of claim 1 in which the notches are V-shaped.

3. The circuit breaker of claim 2 in which the trip bar comprises the tapered pivot edge receiving notches.

4. The circuit breaker of claim 2 in which the trip bar comprises the tapered pivot edge.

5. The circuit breaker of claim 1 in which the notches are on the side of the trip bar opposite the latch lever.