1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The disclosed concept also relates to trip latch assemblies for electrical switching apparatus.
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 pole shaft, a trip actuator assembly, a closing assembly and an opening assembly. The trip actuator assembly responds to the trip unit and actuates the operating mechanism. The closing assembly and the opening assembly may have some common elements, which are structured to move the movable electrical contacts between a first, open position, wherein the movable and stationary electrical contacts are separated, and a second, closed position, wherein the movable and stationary electrical contacts are electrically connected. Specifically, the movable electrical contacts are coupled to the pole shaft. Elements of both the closing assembly and the opening assembly, which are also pivotably coupled to the pole shaft, pivot the pole shaft in order to effectuate the closing and opening of the electrical contacts.
For example, typically when the circuit breaker is open, a trip latch spring applies torque to a trip latch to reset the circuit breaker and prepare it for closing. If, however, the circuit breaker does not reset, for example because of relatively weak spring force, the circuit breaker will attempt to close but be unable to because the trip latch is not reset. This can result in damage to circuit breaker components. Furthermore, the problem is exacerbated by the desire to use as few springs as possible with the smallest spring force possible for resetting in an attempt to avoid an undesirable balance of springs, wherein some springs (e.g., without limitation, opening springs) are trying to open the breaker and some springs (e.g., without limitation, closing springs) are trying to close the breaker.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in trip latch assemblies therefor.
These needs and others are met by embodiments of the disclosed concept, which are directed to a trip latch assembly for electrical switching apparatus such as, for example and without limitation, circuit breakers. Among other benefits, the trip latch assembly functions to substantially remove spring torque when the circuit breaker is closed.
As one aspect of the disclosed concept, a trip latch 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 for opening and closing the separable contacts. The operating mechanism includes a pole shaft. The trip latch assembly comprises: a trip latch structured to be pivotably coupled to the housing, the trip latch being movable between a latched position and an unlatched position; a trip latch reset spring structured to bias the trip latch toward the latched position; a spring housing at least partially overlaying the trip latch reset spring; and a trip latch spring link including a first end structured to be movably coupled to the pole shaft and a second end structured to cooperate with the spring housing. When the electrical switching apparatus needs to be reset, the trip latch spring link is structured to engage the spring housing, in order apply torque to the trip latch reset spring. When the electrical switching apparatus is closed, the bias of the trip latch reset spring on the trip latch is removed.
The spring housing may comprise a first portion, a second portion disposed opposite and distal from the first portion, and a body portion extending between the first portion and the second portion. The first portion may cooperate with the trip latch reset spring, and the second portion may cooperate with the trip latch spring link The first portion of the spring housing may comprise a flange and a number of protrusions, wherein the flange extends radially outwardly from the body portion of the spring housing, and wherein the protrusions extend outwardly from the flange toward the trip latch. The number of protrusions may be a first protrusion and a second protrusion. The first protrusion may cooperate with the trip latch and the trip latch reset spring, and the second protrusion may at least partially overlay and retain the trip latch reset spring.
The trip latch reset spring may be a torsion spring. The torsion spring may include a first end, a second end, and a number of coils. The first end of the torsion spring may engage the trip latch. The second end of the torsion spring may engage the second protrusion. The first protrusion and the second protrusion may at least partially overlay the coils. The torsion spring may be disposed on the shaft between the flange of the spring housing and the trip latch.
The second portion of the spring housing may comprise a paddle extending outwardly from the body portion. The second end of the trip latch spring link may be structured to cooperate with the paddle in order to translate movement of the pole shaft into movement of the spring housing. The second end of the trip latch spring link may include a recess and an edge, wherein the paddle extends into the recess and cooperates with the edge. The first end of the trip latch spring link may include an elongated slot, and the pole shaft may include a pin member. The pin member may be structured to move within the elongated slot in order that movement of the pole shaft is translated into movement of the spring housing only when it is desired to apply torque to the trip latch reset spring to bias the trip latch toward the latched position and reset the electrical switching apparatus.
In accordance with another aspect of the disclosed concept, an electrical switching apparatus employing the aforementioned trip latch assembly, is provided.
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, left, right, clockwise, counterclockwise 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 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).
As shown in
In other words, torque is removed from the trip latch 102 when the circuit breaker 2 is closed. Among other benefits, this results in all variability from the trip latch reset spring 104 being removed. The assembly is also adjustable to ensure the proper time when the spring force is removed from the trip latch 102, and the requirement for maintaining precise tolerances is relaxed. That is, the prior art problem of having a balance of springs wherein some springs are trying to open the circuit breaker 2 and other springs are trying to reset the circuit breaker 2, is removed. Thus, the force tolerance of the reset spring 104 is advantageously not a contributor to holding the circuit breaker 2 from tripping. Accordingly, only the moment arms of the toggle linkages and tripping system contribute to tolerance variation of the force applied to the trip D-shaft. Therefore, the force of the accessories needed in order to trip the circuit breaker 2 can also be less. Additionally, because the trip latch rest spring 104 is only used when the circuit breaker 2 needs to be reset, the spring 104 can be large enough to provide a margin of reliability associated with resetting the circuit breaker 2. Moreover, as will be further discussed herein, the spring 104 is also at least partially contained within the spring housing 106 such that it can be preloaded, as desired.
As best shown in
As best shown in
In the example shown and described herein, the trip latch reset spring is a torsion spring 104. As best shown in
In other words, the first protrusion 122 acts as a radial stop for the trip latch 102 (see, for example,
Continuing to refer to
In order to provide the aforementioned engaging and disengaging feature of the trip latch spring link 108 and, in particular, the spring housing 106 and trip latch reset spring 104, the first end 110 of the example trip latch spring link 108 preferably includes an elongated slot 160. The pole shaft 10 includes a pin member 14, which is movably disposed within the elongated slot 160. Accordingly, the rotational movement of the pole shaft 10 only functions to result in translational movement of the trip latch spring link 108 when the pin member 114 is fully engaged to move the trip latch spring link (e.g., without limitation, to the left in the direction of arrow 300 from the perspective of
Accordingly, the disclosed concept provides a unique trip latch assembly 100, which is structured to efficiently and effectively provide sufficient spring force to reset the circuit breaker 2, but wherein spring tension is removed when circuit breaker 2 is closed.
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.