Patent Application
20150287554
1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus such as for example, circuit breakers. The disclosed concept also relates to dampening assemblies for circuit breakers.
2. Background Information
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 contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are separable from the stationary electrical contacts.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a closing assembly and an opening assembly that are structured to close (e.g., contacts electrically connected) and open (e.g., contacts separated), respectively, the separable contacts. Specifically, the operating mechanism includes a pole shaft, a number of stored energy devices such as, for example, an opening spring and a closing spring, and a latch assembly that cooperates directly or indirectly with the pole shaft to facilitate desired movement of the separable contacts.
The basic components of the latch assembly typically include a D-shaft and a latch (e.g., plate member) that cooperates with the D-shaft, but is disposed on a separate shaft. That is, the latch rotates with the separate shaft about the longitudinal axis of the separate shaft. The D-shaft includes a slot such that it blocks movement of the latch when the D-shaft is disposed in a corresponding range of axial positions, but permits movement of the latch, through the slot, when the D-shaft is disposed in a particular predetermined axial position. Sometimes, however, the D-latch does not come to an ideal resting position during operation, which can have an adverse impact on circuit breaker function. By way of example, if the D-latch is sufficiently out of position, the latch (e.g., trip latch) will not close. Such problems are primarily caused by shock and/or vibration in the system, which can cause components, including the D-shaft, to bounce and/or flutter and ultimately come to rest in an undesirable position.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in dampening assemblies therefor.
These needs and others are met by embodiments of the disclosed concept, which are directed to a dampening assembly for electrical switching apparatus.
As one aspect of the disclosed concept, a dampening assembly is provided for an electrical switching apparatus. The electrical switching apparatus includes a housing, separable contacts enclosed by the housing, and an operating mechanism structured to open and close the separable contacts. The dampening assembly comprises: a D-shaft structured to be pivotably coupled to the housing; and an anti-bounce assembly comprising a first element structured to be coupled to the housing, and a second element adapted to cooperate with the D-shaft to resist undesired movement of the D-shaft.
The D-shaft may comprise a first end, a second end disposed opposite and distal from the first end, and a recess disposed between the first end and the second end. A portion of the second element may be disposed in the recess. The D-shaft may comprise a longitudinal axis and the recess may comprise a groove having a transverse axis, wherein the transverse axis of the groove is substantially perpendicular to the longitudinal axis of the D-shaft. The second element may be an elongated resilient pin member, wherein the elongated resilient pin member extends outwardly from the first element of the anti-bounce assembly. The D-shaft may include a closed position corresponding to the separable contacts being closed. When the D-shaft is disposed in the closed position, the elongated resilient pin member may be disposed in the groove and the transverse axis of the groove may be substantially parallel to the elongated resilient pin member. When the D-shaft is not in the closed position, the elongated resilient pin member may bias the D-shaft toward the closed position.
As another aspect of the disclosed concept, an electrical switching apparatus comprises: a housing; separable contacts enclosed by the housing; an operating mechanism for opening and closing the separable contacts; and a dampening assembly comprising: a D-shaft pivotably coupled to the housing, and an anti-bounce assembly comprising a first element coupled to the housing, and a second element adapted to cooperate with the D-shaft to resist undesired movement of the D-shaft.
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:
For purposes of illustration, embodiments of the invention will be described as applied to medium and low voltage circuit breakers, although it will become apparent that they could also be applied to the charging assemblies of any known or suitable electrical switching apparatus (e.g., without limitation, circuit switching devices and circuit interrupters such as circuit breakers other than medium and low voltage circuit breakers, network protectors, contractors, motor starters, motor controllers and other load controllers).
Directional or positional phrases used herein, such as, for example, vertical, parallel, perpendicular 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.
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.
As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
The dampening assembly 100 includes a D-shaft 102, which is structured to be pivotably coupled to the circuit breaker housing 4, and an anti-bounce assembly 200. The anti-bounce assembly 200 includes a first element 202, also structured to be coupled to the housing 4, and a second element 204 adapted to cooperate with the D-shaft 102 to resist undesired movement of the D-shaft 102. More specifically, as will be described in greater detail hereinbelow, the second element 204 cooperates with (e.g., without limitation, engages and biases) the D-shaft 102 to resist or avoid flutter or vibration of the D-shaft 102, and to insure the D-shaft 102 consistently comes to the desired rest position. In this manner, the disclosed dampening assembly 100 serves to address and overcome disadvantages associated with conventional latch assemblies and D-shafts therefor (not shown).
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Accordingly, the disclosed dampening assembly 100 provides a relatively simple and low-cost yet effective mechanism for dampening flutter or vibration, and ensuring proper operational positioning of the D-shaft 102. Among other benefits, the dampening assembly 100 helps eliminate an undesirable trip free condition of the circuit breaker 2. More specifically, the unique anti-bounce assembly 200, in cooperation with the D-shaft 102 incorporating a novel groove 108 disposed therein, serves to bias the D-shaft 102 so as to effectively reduce or eliminate undesirable vibration or flutter of D-shaft 102, as well as to ensure the D-shaft and remainder of the corresponding assembly (e.g., without limitation, latch assembly) comes to the desired rest position for optimal operation.
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.
