Patent Grant
7646270
This application is related to co-pending, commonly assigned:
U.S. patent application Ser. No. 11/696,810, filed Apr. 5, 2007, and entitled “ELECTRICAL SWITCHING APPARATUS AND TRIP ACTUATOR ASSEMBLY THEREFOR”;
U.S. patent application Ser. No. 11/696,815, filed Apr. 5, 2007, and entitled “ELECTRICAL SWITCHING APPARATUS, AND TRIP ACTUATOR ASSEMBLY AND RESET ASSEMBLY THEREFOR”; and
U.S. patent application Ser. No. 11/696,812, filed Apr. 5, 2007, and entitled “ELECTRICAL SWITCHING APPARATUS AND TRIP ACTUATOR RESET ASSEMBLY THEREFOR”, which are hereby incorporated herein by reference.
1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to yoke assemblies for electrical switching apparatus, such as circuit breakers. The invention also relates to spring assemblies for circuit breaker yoke assemblies.
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.
Among other components, the operating mechanisms of some low-voltage circuit breakers, for example, typically include a pole shaft and a spring assembly. The pole shaft is pivotable among an open position, corresponding to the electrical contact assemblies being open (e.g., contacts separated), and a closed position, corresponding to the electrical contact assemblies being closed (e.g., contacts electrically connected). The spring assembly includes at least one spring that is typically coupled to the circuit breaker housing and, directly or indirectly, to the pole shaft. The spring or springs is/are structured to bias the pole shaft, for example, to facilitate opening of the electrical contact assemblies.
It is desirable to optimize the operation of the spring assembly, in order to improve circuit breaker performance, for example, by enabling the electrical contact assemblies to open rapidly. It is also desirable to minimize the space required for the spring assembly. These two objectives are somewhat contradictory, and are difficult to achieve because of the limited amount of space that is available within the circuit breaker. This is particularly true in view of the increasing trend to minimize the overall size of the circuit breaker. It is, therefore, difficult to effectively arrange the spring assembly and/or related structures within the circuit breaker housing in a manner that affords the desired leverage and spring energy. In this regard, known circuit breaker designs leave much to be desired.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in spring assemblies therefor.
These needs and others are met by embodiments of the invention, which are directed to a yoke assembly and spring assembly therefor for electrical switching apparatus, such as circuit breakers.
As one aspect of the invention, a spring assembly is provided for a yoke assembly of an electrical switching apparatus including a housing, separable contacts enclosed by the housing, and an operating mechanism structured to open and close the separable contacts. The operating mechanism includes a pole shaft. The yoke assembly is coupled to the pole shaft and is movable among a first position corresponding to the separable contacts being closed, and a second position corresponding to the separable contacts being open. The spring assembly comprises: a number of first springs having a first spring rate and being structured to be coupled to the yoke assembly; and a number of second springs having a second spring rate and being structured to be coupled to the yoke assembly. The second spring rate is different than the first spring rate. The number of first springs and the number of second springs are structured to bias the yoke assembly toward the second position.
The yoke assembly may comprise a first end coupled to the pole shaft, a second end, a first side, and a second side. The first side of the yoke assembly may extend from the pole shaft toward the second end of the yoke assembly, and the second side of the yoke assembly may be disposed opposite and distal from the first side. The number of first springs and the number of second springs may be structured to be disposed between the first side and the second side. The yoke assembly may further comprise a first cross member extending between the first side and the second side proximate the first end of the yoke assembly, a second cross member extending between the first side and the second side proximate the second end of the yoke assembly, and a plurality of elongated members having first ends and second ends. The first ends of the elongated members may be fixedly coupled to the second cross member, and the second ends of the elongated members may extend through the first cross member and may be movable with respect to the first cross member. The number of first springs and the number of second springs may be structured to be disposed between the first cross member and the second cross member, and may include a plurality of coils structured to receive a corresponding one of the elongated members therethrough.
The number of first springs may be two first springs, and the number of second springs may be a single second spring, wherein the single second spring is disposed on a corresponding one of the elongated members between the two first springs. The single second spring may include a first end and a second end wherein, when the yoke assembly is disposed in the first position, the first end of the single second spring is structured to be disposed at or about the first cross member and the second end of the single second spring is structured to be disposed at or about the second cross member and wherein, when the yoke assembly is disposed in the second position, the first end of the single second spring is structured to be spaced apart from the first cross member. The first spring rate may be lower than the second spring rate.
As another aspect of the invention, a yoke assembly is provided for an electrical switching apparatus including a housing, separable contacts enclosed by the housing, and an operating mechanism structured to open and close the separable contacts. The operating mechanism includes a pole shaft. The yoke assembly comprises: a first end structured to be coupled to the pole shaft; a second end; a first side extending from the first end toward the second end; a second side disposed opposite and distal from the first side; at least one cross member extending between the first side and the second side; and a spring assembly comprising: a number of first springs having a first spring rate and being coupled to the yoke assembly, and a number of second springs having a second spring rate and being coupled to the yoke assembly. The second spring rate is different than the first spring rate. The yoke assembly is structured to be movable among a first position corresponding to the separable contacts being closed, and a second position corresponding to the separable contacts being open. The number of first springs and the number of second springs bias the yoke assembly toward the second position.
The housing of the electrical switching apparatus may include a mounting surface, a first side plate extending outwardly from the mounting surface, a second side plate extending outwardly from the mounting surface opposite the first side plate, and a guide member extending between the first side plate and the second side plate. The yoke assembly may be disposed between the first side plate and the second side plate. When the yoke assembly moves from the first position toward the second position, at least one of the first side and the second side may be structured to engage the guide member and to slide with respect to the guide member. The housing may further include a pin member extending between the first side plate and the second side plate. Each of the number of first springs and the number of second springs may comprise a first portion and a second portion. The first portion may include a plurality of coils having a first end and a second end coupled to the yoke assembly at or about the second end thereof. The second portion may be substantially flat and may include a first end structured to be coupled to the pin member, and a second end coupled to the first portion at or about the first end of the first portion.
As another aspect of the invention, an electrical switching apparatus comprises: a housing; separable contacts enclosed by the housing; an operating mechanism structured to open and close the separable contacts, the operating mechanism including a pole shaft; and a yoke assembly coupled to the housing, the yoke assembly comprising: a first end coupled to the pole shaft, a second end, a first side extending from the first end toward the second end, a second side disposed opposite and distal from the first side, at least one cross member extending between the first side and the second side, and a spring assembly comprising: a number of first springs having a first spring rate and being coupled to the yoke assembly, and a number of second springs having a second spring rate and being coupled to the yoke assembly. The second spring rate is different than the first spring rate. The yoke assembly is movable among a first position corresponding to the separable contacts being closed, and a second position corresponding to the separable contacts being open. The number of first springs and the number of second springs bias the yoke assembly toward the second position.
The electrical switching apparatus may be a circuit breaker. The housing of the circuit breaker may include at least one of an indicator and an interlock. At least one of the first side of the yoke assembly and the second side of the yoke assembly may be coupled directly to a corresponding one of such indicator and such interlock. Movement of the yoke assembly may actuate the corresponding one of such indicator and such interlock.
As another aspect of the invention, an electrical switching apparatus comprises: a housing including a mounting surface, a first side plate extending outwardly from the mounting surface, and a second side plate extending outwardly from the mounting surface opposite the first side plate; a guide member extending between the first side plate and the second side plate; separable contacts enclosed by the housing; an operating mechanism structured to open and close the separable contacts, the operating mechanism including a pole shaft; and a yoke assembly disposed between the first side plate and the second side plate housing, the yoke assembly comprising: a first end coupled to the pole shaft, a second end, a first side extending from the first end toward the second end, a second side disposed opposite and distal from the first side, and at least one spring coupled to the yoke assembly. The yoke assembly is movable among a first position and a second position. When the yoke assembly moves between the first position and the second position, the at least one spring biases the yoke assembly toward engagement with the guide member, in order that the guide member guides the movement of the yoke assembly.
A full understanding of the invention 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 low-voltage circuit breakers, although it will become apparent that they could also be applied to a wide variety of electrical switching apparatus (e.g., without limitation, circuit switching devices and other circuit interrupters, such as contactors, motor starters, motor controllers and other load controllers) other than low-voltage circuit breakers and other than low-voltage electrical switching apparatus.
Directional phrases used herein, such as, for example, top, bottom, upper, lower, front, back, 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 term “spring rate” refers to the amount of weight needed to compress a spring a certain distance. For example and without limitation, for linear springs, a spring which has a “low” spring rate is relatively soft, or easier to compress, when compared to a spring having a “high” spring rate. The spring rate can be affected by such factors as, for example and without limitation, the length of the spring, the number of coils of the spring, and the type and dimension (e.g., without limitation, diameter; thickness) of the material (e.g., without limitation, wire) from which the spring is made. It will also be appreciated that springs may have more than one spring rate. For example, the spring may have a first spring rate when compression of the spring is initiated, and a second spring rate when the spring is almost fully compressed, or the spring may have a variable spring rate where, for example, the spring rate increases as the spring is compressed.
As employed herein, the term “indicator” refers to any known or suitable indicia of the status (e.g., without limitation, tripped; open; closed) of the electrical switching apparatus expressly including, but not limited to, a visual indicator such as a colored indicator, a light emitting diode (LED), a trip flag, a suitable word (e.g., “TRIPPED”) or a suitable letter (e.g., “T”) or other suitable term or indicia, and audible indicators such as a beep or a predetermined tone or a suitable sound. Indicia such as, for example, the words “ON” and “OFF” or positive (+) and negative (−) signs, which indicate non-tripped status of the electrical switching apparatus, are also contemplated by the invention.
As employed herein, the term “interlock” refers to any known or suitable locking mechanism or assembly for locking one component with respect to another and expressly includes, but is not limited to, locking assemblies for resisting the undesired movement of a draw-out circuit breaker from a cassette, and locking assemblies for resisting the undesired movement of a circuit breaker actuator (e.g., without limitation, operating handle).
As employed herein, the term “linking element” refers to any known or suitable mechanism for connecting one component to another and expressly includes, but is not limited to, rigid links (e.g., without limitation, arms; pins; rods), flexible links (e.g., without limitation, wires; chains; ropes), and resilient links (e.g., without limitation, springs).
As employed herein, the terms “yoke” and “yoke assembly” refer to any known or suitable component or assembly, respectively, that is structured to facilitate movement of the pole shaft of an electrical switching apparatus, for example, in order to open, close, or trip open the separable electrical contacts of the electrical switching apparatus, as desired. It will be appreciated that the component or components of yoke assembly, as defined herein, is/are sometimes referred to in the related art as the “cradle assembly,” in which case the terms “yoke assembly” and “cradle assembly” are synonymous and may be used interchangeably.
As employed herein, the term “fastener” shall mean a separate element or elements which is/are employed to connect or tighten two or more components together, and expressly includes, without limitation, rivets, pins, 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 yoke assembly 100 is coupled to the pole shaft 12, as best shown in
As shown in
Continuing to refer to
Specifically, the disclosed spring assembly 200 provides superior circuit breaker performance by enabling a relatively high initial opening velocity through the use of the single second spring 206, which has a higher spring rate and shorter length (best shown in
More specifically, the example yoke assembly 100 includes two cross members, a first cross member 110 extending between the first and second sides 106,108 of the yoke assembly 100 proximate the first end 102 of the yoke assembly 100 and a second cross member 112 extending between the first and second sides 106,108 of the yoke assembly 100 proximate the second end 104 thereof, as shown in
As previously discussed, the example single second spring 206 is shorter than the example two first springs 202,204, which are preferably the same length, as best shown in
For example,
Referring again to
Accordingly, it will be appreciated that the disclosed yoke assemblies 100,100′ and spring assemblies 200,200′ therefor are preferably structured to optimize circuit breaker performance while occupying a minimal amount of space. This, in turn, enables the overall size of the circuit breaker 2 (
While specific embodiments of the invention 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 invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
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| Number | Date | Country | |
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| 20080271981 A1 | Nov 2008 | US |
