TRIP LATCH ASSEMBLY THEREFOR

BACKGROUND

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 eiectricai switching apparatus.

Background Information

Electrical switching apparatus, such as circuit breakers, provide proteciioo 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 eiectricai contact assemblies include stationary eiectricai contacts and corresponding movable electrical contacts that are separable from the stationary eiectricai 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 shall. Elements of both the closing assembly and the opening assembly, which are also pivotab!y coupled to the pole shaft, pivot the pole shaft in order to effectuate the closin and opening of the electrical contacts.

For example, typically when the circuit, breaker is open, a trip latch sprin 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 wi h 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. SUMMARY

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 tongue 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 sprin 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 t 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, whereto the flange extends radiailv 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.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanyin drawings in which;

Figure I is an elevation view of a portion of a circuit breaker and trip latch assembly therefor, in accordance with an embodiment of the disclosed concept, wherein the breaker is shown tripped and discharged; Figure 2 is the elevation view of Figure I , modified to show the circuit breaker closed;

Figure 3 is an exploded front isometric ^" view of the trip latch assembly of Figure 2;

Figure 4 is an assembled front isometric view of the trip latch assembly of Figure 3;

Figure 5 is an exploded back isometric view of the trip latch assembly of Figure 4; and

Figure 6 is an assembled back isometric view of the trip latch assembly of Figure 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

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).

Figure I shows a trip latch assembly 100 for an electrical switching apparatus such as, for example and without limitation, a circuit breaker 2 (partially shown in Fi ures .1 and 2), in accordance with the disclosed concept. The circuit breaker 2 includes a housing 4 (partially shown in Figures 1 and 2), separable contacts 6 (shown in simplified form in Figure 1 ), and an operating mechanism 8 (shown in simplified form in Figure 1) for opening and closing the separable contacts 6. The operating mechanism 8 includes a pole shaft 10. The trip latch assembly 1 0 includes a trip latch 1 2 (best shown in Figures 3-6), which is pivotably coupled to the circuit breaker housing 4 and is movable between a latched position (see, fo example.

Figure 2) and an unlatched position (see, for example. Figure 1 ), The trip latch assembly 100 further includes a tnp latch reset spring 104 (shown in hidden line drawing in Figures 1 and 2; best shown in the exploded isometric views of Figures 3 and 5). The trip latch reset spring 104 is structured to bias the trip latch 102 toward the latched position. A spring housing 106 at least partially overlays the trip latch reset spring 104, as shown in Figures 1 , 2, 4 and 6.

As shown, in Figures 1 and 2, a trip latch, spring link 1 8 includes first and second opposing ends 1 10,1 12. The first end. 10 is raovab!y coupled to the circuit breaker pole shaft 10, and the second end 1 12 is structured to cooperate with the spring housing 1.06. More specifically, when the circuit breaker 2 needs to be reset, for example and without limitation after the breaker has tripped and discharged, as shown in Figure 1 , the trip latch spring link 108 engages the spring housing 106, in order to apply torque to the trip latch reset spring 104 to bias the trip latch 102 toward the latched position, shown in Figure 1. Accordingly, it will be appreciated that in accordance with the disclosed concept, the trip latch reset spring 104 only biases the trip latch 102 when the circuit breaker 2 needs to be reset.

In other words, torque is removed from the trip latch 1 2 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 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 ot 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 1 6 such that it can be preloaded, as desired.

As best shown in Figures 3-6, the spring housing .106 of the non- limiting example trip latch assembly 1 0, shown and described herein, includes a first portion 1 14, a second portion 1 16 disposed opposite and distal from the first portion 11.4, and a body portion 1 .1 8 extending therebetween. The first portion 1 14 cooperates wi ih the trip latch reset spring 104, and the second portion 1 16 cooperates with the trip latch spring link 108 (Figures i and 2). The body portion i 1 of ihe spring housing 106 preferably comprises an elongated sleeve member., which is disposed on the pivotable shaft .12 to which the trip latch 102 is coupled. The first portion 1 14 of the example spring housing 1 6 includes a flange 122 extending radially outwardly 5 from the body -portion i 18. A number of protrusions 1.22,124 (two are shown) extend outwardly from the flange 120 toward the trip latch 102.

As best shown in Figure 5, the example spring housing 106 has a first protrusion 122 and a second protrusion 124. The first protrusion 122 extends outwardly form the aforementioned flange 120 and cooperates with the nip latch 102

10 and the trip latch reset spring 1 4 (best shown in Figure 6). The second protrusion 124 at least partially overlays and retains the trip latch reset spring 104, More specifically, as shown in Figure 5, the second protrusion 1.24 preferably comprises an arcuate molded portion thai conforms to the shape of the spring 104. Accordingly, it will be appreciated thai the trip latch reset spring .1 4 is preferably disposed o the

I S shaft 12, between the flange 120 of the spring housing 106 and the trip latch 102.

In the example shown and described herein, the trip latch reset spring is a torsion spring 104. As best shown in Figures 3 and 5, the torsion spring 104 includes first and second ends 130, 132 and a number of cods 134. The first end 130 of the torsion spring 104 engages the trip latch 102, as shown m Figure 6, and the

20 second end 132 engages the second protrusio ! 24. Both the first protrusion 122 and the second protrusion 124 preferabl at least partially overla the spring coils 134, as shown in Figures 4 and 6. In this manner, as previously discussed hereinabove, the spring housing 106 functions to control (e.g., without limitation, engage and

disengage) the amount of spring bias supplied to the trip latch 102, when the spring 5 housing 106 is manipulated by the trip latch spring link 108 (Figures 1 and 2).

Among other benefits, the new construction of the spring housing 10 also enables the spring 104 to be adjusted, as desired, for example and without limitation, to provide the spring 104 with a predetermined amount of preload.

In other words, the first protrusion 122 acts as a radial stop for the trip 0 latch .502 (see, for example, Figure 6). This stop functions to remove all radial torque of ihe trip latch reset spring 104 and contains it in the assembly of the spring housing 106, spring 104, and trip latch 102.

Continuing to refer to Figures 3-6, and also referring again to Figures 1 and 2, operation of the trip latch spring link 108 to manipulate the spring housing 106 will now be described in greater detail. Specifically, in the example shown and described herein, the second portion 1 16 of the s prin g housing 106 incl udes a paddle 1 0, which extends outwardly from the body portion 118 of the spring housing 106. The second end 1 12 of the trip latch spring link 1 8 (figures 1 and 2} is structured t cooperate with the paddle 140, in order to translate .movement of the poie shaft 10 into movement of the spring housing Ϊ 6. More specifically, the second end 1 12 of the trip latch spring link 108 preferably includes a recess 150 and an edge 152, wherein the paddle 140 extends into the recess 150, as shown in Figures 1 and 2, The paddle 140 cooperates with the edge 152 such that, when pole shaft 10 of the circuit breaker 2 pivots (e.g., without limitation, rotates counter clock ^' wise in the direction of arrow 200 from the perspective of Figure ϊ ) and the trip latch spring link 108 is accordingly moved (e.g., without limitation, to the left in the direction of arrow 300 from the perspective of Figure 1), the edge 152 of the second end 1 12 of the trip latch spring link 108 engages and pulls the paddle 140, thereby pivoting (e.g., without limitation, counterclockwise from the perspective of Figure 1) the spring housing 106.

Accordingly, it will be appreciated that the trip latch spring link 108 translates the movement of the pole shaft 1 into movement of the spring housing 1 6, when, and only when, it is desired to apply torque to the trip latch reset spring 104 to bias the trip latch 102 toward the latched position and reset the circuit breaker 2, it will be appreciated that at all other times, torsion or biasing force of the spring 104 is substantially removed from the trip latch .1 2,

In order to provide the aforementioned engaging and disengaging feature of the trip latch spring link 1 8 and, in particular, the spri ng housing 106 and trip latch reset spring 104, the first end 1. 10 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 movah!y disposed within the elongated slot 1 0. Accordingly, the rotational movement of the pole shaft 1.0 only functions to result in trans httionai. movement of the trip latch spring link 1 8 when the pin member 1 14 is folly 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 Figure I ), as shown m Figure 1 , For example and without limitation, Figure 1 shows the circuit breaker 2 and trip latch assembly 1 0 therefor in the positions associated with the circuit, breaker 2 being tripped and discharged. Thus, the pole shaft 10 is indeed moving the trip latch spring link 108 in order to keep tension on the tri latch spring 1 4 to bias the trip latch 1.02 toward the latched position to rese the circuit breaker 2. in other instances, such as for example and without limitation, hi Figure 2 which shows the circuit breaker 2 and trip iatch assembly therefor when the circuit breaker is closed, the trip iatch spring link 108 is disengaged from the pole shaft 10, because the aforementioned pin member 14 is free to slide within the elongated slot 1 0. As such, the edge i 52 on the first end 1 12 of the trip latch spring link 108 disengages the paddle 1 0 of the spring housing 106, and tension is released from the spring housing 106 and, therefore, from the trip latch reset spring 104.

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 de veloped in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative onl 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.

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