Circuit breaker, fastening assembly thereof and associated assembly method

Abstract

The present invention is entitled "Circuit breaker, its fastening assembly and associated assembly method". The present invention discloses a fastening assembly for a circuit breaker. The circuit breaker has a base and a bimetal. The fastening assembly includes a heater element, which is configured to be coupled to the bimetal and the base; and a plurality of fastening members, which include a nut and a coupling member coupled to the nut. The nut is configured to be arranged between the heater element and the bimetal. The coupling member extends through the heater element and enters the nut so as to minimize the movement of the heater element relative to the base.

Description

Background Art Technical Field

[0002] 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 fastening assemblies and assembly methods for circuit breakers. Background Art

[0004] Electrical switching devices (such as molded case circuit breakers) typically include at least one pair of separable contacts that are manually operated by a handle disposed on the outside of the circuit breaker housing, or automatically operated by a trip unit in response to a trip condition (e.g., but not limited to, an overcurrent condition, a relatively high level short circuit or fault condition, a ground fault, or an arc fault condition).

[0005] Figure 1 An example of a molded case circuit breaker 2 having a molded case housing 4 and employing a thermal trip assembly 6 is shown. The thermal trip assembly 6 includes a bimetal 8 and a heater element 10 (e.g., a load conductor). Even a small movement of the heater element 10 can result in a significantly amplified movement of the bimetal, resulting in inaccurate calibration. To resist the undesired movement and thereby improve calibration, an epoxy resin 12 has been used (for illustration purposes only). Figure 1 ) to secure the heater element 10 to the circuit breaker housing 4. Figure 1 In the example of FIG. 4 , a gasket 14 is included between the housing 4 and the heater element 10. Among other problems, the epoxy 12 occasionally fails to hold, for example due to grease or other contamination on the surface of one or more of the circuit breaker components. In addition, testing has shown that even if the epoxy 12 is in place, holding the heater element 10 to the housing 4, a relatively large amount of undesirable movement can still occur (e.g., Figure 1 in the direction of arrow 16).

[0006] There is room for improvement in circuit breakers, fastening assemblies thereof, and associated assembly methods. Summary of the invention

[0007] These needs and others are met by embodiments of the present invention, which are directed to circuit breakers, fastening assemblies thereof, and associated assembly methods.

[0008] As one aspect of the disclosed concept, a fastening assembly for a circuit breaker is provided. The circuit breaker has a base and a bimetal. The fastening assembly includes a heater element configured to be coupled to the bimetal and the base; and a plurality of fastening members including a nut and a coupling member coupled to the nut. The nut is configured to be located between the heater element and the bimetal. The coupling member extends through the heater element and into the nut to minimize movement of the heater element relative to the base.

[0009] As another aspect of the disclosed concept, a circuit breaker is provided, the circuit breaker including a base bimetal and the aforementioned fastening assembly.

[0010] As another aspect of the disclosed concept, a method of assembling a circuit breaker is provided. The method includes the steps of providing a circuit breaker having a base, a bimetal, and a fastening assembly having a heater element coupled to the bimetal and the base, and a plurality of fastening members including nuts and coupling members; placing the nut between the heater element and the bimetal; and extending the coupling member through the heater element and into the nut so as to minimize movement of the heater element relative to the base. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A complete understanding of the disclosed concepts can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings, in which:

[0012] Figure 1 is an isometric view of a portion of a known circuit breaker and heater assembly;

[0013] Figure 2 is a partially cut-away isometric view of a portion of a circuit breaker and a fastening assembly thereof according to a non-limiting embodiment of the disclosed concept; and

[0014] Figure 3 yes Figure 2 A partially cut-away side elevation view of a circuit breaker and its fastening assembly;

[0015] Figure 3A yes Figure 3 an enlarged view of a portion of a circuit breaker and its fastening assembly; and

[0016] Figure 4 and Figure 5 yes Figure 2 Different partially cut-away isometric views of portions of a circuit breaker and its fastening assembly, shown without the plate member. DETAILED DESCRIPTION

[0017] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Still further, as used herein, the term "number" shall mean one or an integer greater than one (eg, a plurality).

[0018] As used herein, the term "coupled" shall mean that two or more parts are directly connected together or connected together through one or more intermediate parts. In addition, as used herein, the phrase "directly connected" shall mean that two or more parts are directly connected together without any intermediate parts disposed between them at the point or location of connection.

[0019] As used herein, the term "connecting member" refers to any suitable connection or tightening mechanism, specifically including but not limited to screws, bolts, and combinations of bolts and nuts (such as but not limited to lock nuts) and bolts, washers and nuts.

[0020] Figure 2-Figure 5 An electrical switching apparatus according to one non-limiting embodiment of the disclosed concepts is shown, such as, for example, but not limited to, a circuit breaker 102. The circuit breaker 102 includes a molded base 103, a bimetal 106, and a novel fastening assembly 110. The fastening assembly 110 includes a heater element 122 (e.g., a load conductor) and a plurality of fastening members (e.g., but not limited to, a nut 132, a coupling member (e.g., but not limited to a screw 152), and a plate member 162). As will be discussed in more detail below, the fastening assembly 110 provides a novel mechanism to substantially minimize and / or eliminate movement of the heater element 122 relative to the base 103.

[0021] As shown, the nut 132 is preferably located between the heater element 122 and the bimetal 106. Figure 2 , the screw 152 has a head portion 154 and a threaded portion 156 extending from the head portion 154. The heater element 122 is located between the head portion 154 and the nut 132. The threaded portion 156 extends through the heater element 122 and into the nut 132 to minimize and / or eliminate movement of the heater element 122 relative to the base 103. See, for example, portion 105 of the base 103. The nut 132 has a stabilizing portion 134 and a post portion 136 extending outwardly from the stabilizing portion 134 and away from the bimetal 106. The stabilizing portion 134 is positioned substantially perpendicular to the post portion 136.

[0022] See also Figure 3 , the base 103 has a surface 104 facing the bimetal 106 and positioned parallel to the bimetal. In addition, the stabilizing portion 134 of the nut 132 is substantially located between the surface 104 and the bimetal 106 and is positioned parallel to the bimetal 106. By fitting the recess between the surface 104 and the bimetal 106, the stabilizing portion 134 advantageously allows the screw 152 to be tightened into the nut 132, and thus allows the heater element 122 to be retained on the base 103. In addition, as Figure 3AAs shown, in one example embodiment, the nut 132 is spaced apart from the bimetal 106. Therefore, the nut 132 does not decouple from calibration and / or interfere with the trip time. Specifically, the current path passes from the beginning of the heater element 122 through the entire length of the bimetal 106, and then through the remainder of the circuit breaker 102. If the nut 132 were to contact the bimetal 106, some of the current would not pass through half of the heater element 122 and half of the bimetal 106. Therefore, the disclosed configuration in which the nut 132 is spaced apart from the bimetal 106 is particularly advantageous.

[0023] See also Figure 4 , the stabilizing portion 134 includes a first edge portion 138 and a second edge portion 140 positioned opposite and substantially parallel to the first edge portion 138. When the circuit breaker 102 is assembled, the first and second edge portions 138, 140 are configured to engage the base 103 so as to allow the screw 152 to be coupled to the nut 132. Therefore, it should be understood that the stabilizing portion 134 is configured to engage the base 103 so as to prevent the nut 132 from rotating relative to the base 103. While the disclosed concepts have been described thus far in association with the stabilizing portion 134 and the associated first and second edge portions 138, 140 for performing the desired function of preventing the nut 132 from rotating during tightening of the screw 152, it should be understood that suitable alternative approaches and / or component geometries may be employed without departing from the scope of the disclosed concepts. For example, but not limited to, within the scope of the present disclosure, an alternative nut (not shown) is provided in conjunction with a molded base having protrusions and / or stop members (not shown) that inhibit rotation of the nut during tightening of the screw.

[0024] Continue to see Figure 4 , as shown, the post portion 136 extends a distance D from the stabilizing portion 134, and the stabilizing portion 134 has a thickness T. In an exemplary embodiment, the distance D is at least 2.5 times the thickness T. It should therefore be appreciated that the nut 132 provides sufficient surface area over which the threaded portion 156 of the screw 152 may threadably engage the nut 132. However, it should be appreciated that this ratio is not limiting to the scope of the disclosed concepts, and suitable alternative ratios (e.g., less than 2.5) are contemplated herein.

[0025] See again Figure 3, depicting an example plate member 162. In an example embodiment, the plate member 162 is positioned substantially parallel to the bimetal 106 and the stabilizing portion 134 of the nut 132, and is positioned perpendicular to the column portion 136 of the nut 132. As shown, the plate member 162 has a first surface 164 and a second surface 166 opposite and parallel to the first surface 164. The first surface 164 engages the heater element 122 and is substantially flush therewith. The second surface 166 engages the head portion 154 of the screw 152. Therefore, it should be understood that the plate member 162 advantageously provides such a mechanism: the mechanism is used to distribute the load from the head portion 154 of the screw 152 over a relatively large surface area of ​​the heater element 122, rather than a localized area. Therefore, the plate member 162 can improve the ability of the screw 152 to secure the heater element 122 to the base 103. However, it should be understood that the fastening assembly according to the disclosed concept can be employed without a plate member. That is, a suitable alternative fastening assembly (not shown) may alternatively engage the head portion of a screw or other alternative coupling member directly with the heater element rather than the plate member without departing from the scope of the disclosed concept.

[0026] As discussed above, the novel fastening assembly 110 substantially minimizes and / or eliminates movement of the heater element 122 relative to the base 103. Figure 5 , the heater element 122 is located between the head portion 154 of the screw 152 and the nut 132. In addition, although Figure 5 Although only partially shown in the drawings, portion 105 of base 103 is located on the side of heater element 122 opposite head portion 154 of screw 152. It should be understood, therefore, that when screw 152 is tightened into nut 132, heater element 122 is pulled into portion 105 of base 103. This secure and novel connection advantageously allows heater element 122 to remain substantially in a predetermined position. In other words, due to the novel fastening assembly 110, the likelihood that heater element 122 will move during the life of circuit breaker 102 is significantly reduced. It follows that bimetal 106 coupled to heater element 122 will also remain substantially in place during the life of circuit breaker 102. Thus, calibration of circuit breaker 102 is improved as compared to prior art circuit breakers 2, such as those of FIG. Figure 1 In one exemplary embodiment, the circuit breaker 102 according to the disclosed concept is completely free of epoxy that engages and holds the heater element 122, unlike prior art circuit breakers (e.g., Figure 1The circuit breaker 2 in the prior art is different, which usually requires epoxy resin to hold and maintain the heater element to the base. In addition, within the scope of the disclosed concept, a glue-like material is also provided between the nut 132 and the screw 152 to prevent the screw 152 from loosening over time.

[0027] It should be understood that the method of assembling the circuit breaker 102 includes the following steps: providing the circuit breaker 102 having the base 103, the bimetal 106, and the fastening assembly 110, the fastening assembly 110 having the heater element 122 coupled to the bimetal 106 and the base 103, and a plurality of fastening members including a nut 132 and a coupling member (e.g., a screw 152); disposing the nut 132 between the heater element 122 and the bimetal 106; and extending the screw 152 through the heater element 122 and into the nut 132 so as to minimize movement of the heater element 122 relative to the base 103. The method may also include the following steps: screwing the screw 152 into the nut 132, the nut 132 engaging the base 103 during the screwing-in step so as to prevent rotation of the nut 132.

[0028] It should be understood, therefore, that the disclosed concepts provide improved (e.g., but not limited to, better secured heater element 122 and bimetal 106, more accurately calibrated circuit breaker 102) circuit breakers 102, fastening assemblies 110 thereof, and associated assembly methods wherein a coupling member 152 extends through the heater element 122 and into the nut 132 so as to minimize movement of the heater element 122 relative to the base 103.

[0029] Although specific embodiments of the disclosed concepts have been described in detail, it will be appreciated by those skilled in the art that various modifications and substitutions of those details may be developed based on the overall teachings of the present disclosure. Therefore, the specific arrangements disclosed are intended to be illustrative only and not to limit the scope of the disclosed concepts, which is given by the full scope of the appended claims and any and all equivalents thereof.

Claims

1. A fastening assembly for a circuit breaker, the circuit breaker comprising a base and a bimetal, the fastening assembly comprising: a heater element configured to be coupled to the bimetal and the susceptor; as well as A plurality of fastening members including a nut and a coupling member coupled to the nut, the nut being configured to be disposed between the heater element and the bimetal, the coupling member extending through the heater element and into the nut so as to minimize movement of the heater element relative to the base.

2. The fastening assembly of claim 1, wherein the nut includes a stabilizing portion and a post portion configured to extend outwardly from the stabilizing portion and away from the bimetal.

3. The fastening assembly of claim 2, wherein the stabilizing portion is disposed substantially perpendicular to the post portion.

4. The fastening assembly of claim 2, wherein the stabilizing portion comprises a first edge portion and a second edge portion opposite to the first edge portion and disposed substantially parallel to the first edge portion; and wherein each of the first edge portion and the second edge portion is configured to engage the base so as to allow the coupling member to be coupled to the nut.

5. The fastening assembly of claim 2, wherein the stabilizing portion is configured to be disposed substantially parallel to the bimetal.

6. The fastening assembly of claim 2, wherein the post portion extends a distance from the stabilizing portion, wherein the stabilizing portion has a thickness, and wherein the distance is at least 2.5 times the thickness.

7. The fastener assembly of claim 1, wherein the coupling member is a screw; wherein the screw includes a head portion and a threaded portion extending from the head portion; and wherein the heater element is disposed between the head portion and the nut.

8. The fastening assembly of claim 7, wherein the plurality of fastening members further comprises a plate member having a first surface and a second surface opposite and parallel to the first surface; wherein the first surface engages the heater element; and wherein the second surface engages the head portion of the screw.

9. The fastening assembly of claim 8, wherein the plate member is configured to be disposed parallel to the bimetal.

10. A fastening assembly according to claim 9, wherein the nut includes a stabilizing portion and a column portion configured to extend outward from the stabilizing portion and away from the bimetal; wherein the stabilizing portion is disposed substantially parallel to the plate member; and wherein the column portion is disposed substantially perpendicular to the plate member.

11. The fastener assembly of claim 1 , wherein the fastener assembly is free of epoxy that engages the heater element.

12. A circuit breaker comprising: Pedestal; Bimetallic; as well as A fastening assembly, the fastening assembly comprising: a heater element coupled to the bimetal and the susceptor; as well as A plurality of fastening members including a nut and a coupling member coupled to the nut, the nut being disposed between the heater element and the bimetal, the coupling member extending through the heater element and into the nut so as to minimize movement of the heater element relative to the base.

13. The circuit breaker of claim 12, wherein the nut includes a stabilizing portion and a post portion extending outwardly from the stabilizing portion and away from the bimetal; and wherein the stabilizing portion is configured to engage the base to prevent the nut from rotating relative to the base.

14. The circuit breaker according to claim 13, wherein the base has a surface facing the bimetal and disposed parallel to it; and wherein the stabilizing portion is disposed between the surface and the bimetal.

15. The circuit breaker of claim 13, wherein the stabilizing portion is disposed substantially perpendicular to the column portion.

16. The circuit breaker of claim 13, wherein the stabilizing portion comprises a first edge portion and a second edge portion opposite to the first edge portion and disposed substantially parallel to the first edge portion; and wherein each of the first edge portion and the second edge portion is configured to engage the base so as to allow the coupling member to be coupled to the nut.

17. The circuit breaker of claim 13, wherein the post portion extends a distance from the stabilizing portion, wherein the stabilizing portion has a thickness, and wherein the distance is at least 2.5 times the thickness.

18. The circuit breaker of claim 12, wherein the coupling member is a screw; wherein the screw includes a head portion and a threaded portion extending from the head portion; wherein the heater element is disposed between the head portion and the nut; wherein the plurality of fastening members further include a plate member having a first surface and a second surface opposite to and parallel to the first surface; wherein the first surface engages the heater element; and wherein the second surface engages the head portion of the screw.

19. A method for assembling a circuit breaker, comprising the steps of: providing the circuit breaker having a base, a bimetal, and a fastening assembly, the fastening assembly including a heater element coupled to the bimetal and the base, and a plurality of fastening members including nuts and coupling members; disposing the nut between the heater element and the bimetal; as well as The coupling member extends through the heater element and into the nut to minimize movement of the heater element relative to the base.

20. The method of claim 19, wherein the coupling member is a screw; and wherein the method further comprises the steps of: The screw is screwed into the nut, the nut engaging the base during the screwing-in step so as to prevent rotation of the nut.

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