Patent Application
20190139717
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electric switching apparatus, such as for example, circuit breakers. The disclosed concept also relates to crossbar assemblies for circuit breakers. The disclosed concept further relates to spring caps for crossbar assemblies.
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit.
The electrical contacts generally comprise one or more movable contacts and one or more corresponding stationery contacts. Each pair of separable contacts is electrically connected, in series, between corresponding line and load terminals which are typically positioned at opposite ends of the circuit breaker. More specifically, each movable contact is disposed at or about a first end of a corresponding moving arm, which is part of a movable contact assembly. The moving arm is pivotably coupled, at or about its second end, to a crossbar of the operating mechanism. A suitable shunt (e.g., without limitation, flexible conductor) electrically connects the movable contact assembly to a load conductor. The operating mechanism controls the moving arm to pivot the movable contact(s) into and out of electrical contact with the corresponding stationary contact(s). The crossbar carries the moving arms for all of the poles of the circuit breaker, and allows for simultaneous opening and closing in all of the poles.
Contact pressure between the stationery and movable contacts is typically achieved using contact springs (e.g., compression springs), which are held in desired positions with respect to corresponding moving arms via spring clips coupled to the crossbar assembly. The spring clips can deform as a result of forces, for example, forces associated with blow-off operation. Such deformation can adversely affect breaker performance, for example, by resulting in inconsistent breaker contact force.
There is room for improvement in electrical switching apparatus, and in crossbar assemblies and spring caps therefor.
These needs and others are met by embodiments of the invention, which are directed to a spring cap for a crossbar assembly of an electrical switching apparatus.
As one aspect of the disclosed concept, a spring cap is provided for an electrical switching apparatus. The electrical switching apparatus comprises a housing, a stationary contact, a movable contact disposed on a moving arm, and a crossbar assembly. The crossbar assembly comprises a crossbar, a first contact spring, a second contact spring, and a spring clip. The moving arm is coupled to the crossbar. The spring cap comprises: a first segment structured to be disposed between the spring clip and the first contact spring; a second segment structured to be disposed between the spring clip and the second contact spring; and a connecting portion connecting the first segment to the second segment. The spring clip is disposed between the moving arm and the contact springs. The spring cap is structured to support the spring clip and evenly distribute bias forces of the first contact spring and the second contact spring.
The spring cap may be a unitary member consisting of one single piece of material, wherein the connecting portion is a molded web of material interconnecting the first segment and the second segment. The crossbar may include a molded recess, wherein the spring cap is structured to engage the first contact spring and the second contact spring within the molded recess, wherein the molded web of material functions as a rejection feature, and wherein the rejection feature is structured to only permit the spring cap to be disposed within the molded recess in one single predetermined orientation.
As another aspect of the disclosed concept, a crossbar assembly is provided for an electrical switching apparatus. The electrical switching apparatus comprises a housing, a number of a stationary contacts, a number of movable contacts, and a number of moving arms. Each of the movable contacts is disposed on a corresponding one of the moving arms. The crossbar assembly comprises: a crossbar structured to pivot the number of moving arms thereby moving the movable contacts into and out of electrical communication with the stationary contacts, the crossbar having a number of molded recesses; a pair of contact springs disposed in each of the molded recesses; a spring clip enclosing the pair of contact springs within the molded recess, the spring clip being disposed between a corresponding one of the moving arms and the pair of contact springs; and a spring cap cooperating with the pair of contact springs within the molded recess, each spring cap comprising: a first segment disposed between the spring clip and a first contact spring of the pair of contact springs, a second segment disposed between the spring clip and a second contact spring of the pair of contact springs, and a connecting portion connecting the first segment to the second segment. The spring cap supports the spring clip and evenly distributes bias forces of the first contact spring and the second contact spring.
As a further aspect of the disclosed concept, an electrical switching apparatus comprises: a housing; a number of a stationary contacts; a number of movable contacts; a number of moving arms, each of the movable contacts being disposed on a corresponding one of the moving arms; and a crossbar assembly comprising: a crossbar for pivoting the moving arms thereby moving the movable contacts into and out of electrical communication with the stationary contacts, the crossbar having a number of molded recesses, a pair of contact springs disposed in each of the molded recesses, a spring clip enclosing the pair of contact springs within the molded recess, the spring clip being disposed between a corresponding one of the moving arms and the pair of contact springs, and a spring cap cooperating with the pair of contact springs within the molded recess, each spring cap comprising: a first segment disposed between the spring clip and a first contact spring of the pair of contact springs, a second segment disposed between the spring clip and a second contact spring of the pair of contact springs, and a connecting portion connecting the first segment to the second segment. The spring cap supports the spring clip and evenly distributes bias forces of the first contact spring and the second contact spring.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
Directional phrases used herein, such as, for example, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. It is to be understood that the specific elements illustrated in the drawings and described in the following specification are simply exemplary embodiments of the disclosed concept. Therefore, specific orientations and other physical characteristics related to the embodiments disclosed herein are not to be considered limiting with respect to the scope of the disclosed concept.
As employed herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Still further, as used herein, the term “number” shall mean one or an integer greater than one (e.g., a plurality).
As employed herein, the term “coupled” shall mean that two or more parts are joined together directly or joined through one or more intermediate parts. Furthermore, as employed herein, the phrase “directly connected” shall mean that two or more parts are joined together directly, without any intermediate parts being disposed therebetween at the point or location of the connection.
As employed herein, the term “fastener” refers to any suitable connecting or tightening mechanism expressly including, but not limited to, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts.
Continuing to refer to
As shown in
The spring cap 200 cooperates with the contact springs 104,106. Continuing to refer to
Preferably, the spring cap 200 is a unitary member consisting of one single piece of material (e.g., without limitation, molded plastic). Thus, the connecting portion 206 comprises a molded web of material interconnecting the aforementioned first and second segments 202,204. It will be appreciated that the molded web of material that comprises the connecting portion 206 is structured to function as a “rejection feature.” That is, the rejection feature molded web of material 206 is configured so as to only permit the spring cap 200 to be installed within the molded recess 120 in one single predetermined configuration. In this manner, the spring cap 200 is designed to avoid incorrect installation of the spring cap 200, thereby avoiding improper assembly of the crossbar assembly 100 and problems that would result from such incorrect assembly.
Referring again to
The spring clip 110 preferably has a predetermined geometry, and the first and second segments 202,204 together form a contact surface 220 having a predetermined profile. It will be appreciated that, in accordance with the disclosed concept, the predetermined profile of the spring cap contact surface 220 is structured to cooperate with the predetermined geometry of the spring clip 110, in order to suitably support the spring clip 110 as well as evenly distribute contact spring biasing forces on the spring clip 110 and, in turn, on the corresponding moving arm 10. In the example shown and described herein, the spring clip 110 includes a plurality of bends 130,132, which together create the aforementioned predetermined geometry, and the predetermined profile of the spring cap contact surface 220 comprises a plurality of angled surfaces 222,224 (best shown in
Accordingly, the disclosed crossbar assembly 100 and spring cap 200 therefor function to suitably support the spring clip 110, while also cooperating with the contact springs 104,106 and spring clip 110 to evenly distribute biasing forces on the spring clip 110 and bias the corresponding moving arm 10 as desired. Thus, the disclosed spring cap 200 advantageously avoids known prior art problems such as, for example and without limitation, spring clip deformation and inconsistent contact forces and breaker performance.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
