Patent Grant
7695300
1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to conductor connection assemblies for electrical switching apparatus such as, for example, circuit breakers. The invention also relates to methods for providing electrically insulated conductor connection 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 level voltage conditions and other fault conditions. Typically, circuit breakers include an operating mechanism having a switching device structured to open electrical contact assemblies in order to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions.
For example, circuit breakers, such as power circuit breakers for systems operating above about 1,000 volts, typically employ vacuum interrupters as the switching devices. Vacuum interrupters include separable electrical contacts disposed within an insulating housing. Generally, one of the contacts is fixed relative to both the housing and to an external electrical conductor, which is electrically interconnected with a power circuit associated with the circuit breaker. In the case of a vacuum circuit interrupter, the other contact is typically part of a movable contact assembly. The movable contact assembly usually comprises a stem of circular cross-section having, at one end, the contact enclosed within a vacuum chamber and, at the other end, a driving mechanism which is external to the vacuum chamber. Power circuit breakers and vacuum interrupters therefor, are discussed in further detail, for example, in U.S. Pat. No. 6,373,358, which is incorporated herein by reference.
Electrically energized or “live” components of electrical switching apparatus must be sufficiently electrically insulated from nearby components that are electrically conductive, in order to resist undesirable electrical shorts. For example, this is particularly true in view of the market trend to design power circuit breakers to be as small and compact as possible. Specifically, the joints where electrical connections are made between components of the circuit breaker, such as between each terminal (e.g., line terminal; load terminal) and the corresponding electrical conductor (e.g., line conductor; load conductor) of the circuit breaker are one area where it is particularly difficult to achieve the requisite level of electrical insulation.
One prior proposal for providing the desired electrical insulation has been to fully encapsulate the joint in an epoxy insulation. Specifically, the joint, including the fastener(s) (e.g., without limitation, screw; bolt) that secures the joint together, have traditionally been completely covered with the epoxy insulation coating, which is molded to the joint under relatively high temperature and/or pressure, or via insulating sleeves. As the epoxy cools, it hardens, thereby forming a tight, electrically insulative bond. However, such an encapsulating approach disadvantageously makes it difficult, if not impossible, to unfasten (e.g., separate or disconnect) the individual components of the joint once it has been assembled and encapsulated. It is desirable, therefore, to provide electrically insulated conductor connection assemblies that can be relatively easily unfastened (e.g., disassembled).
There is, therefore, room for improvement in conductor connection assemblies for electrical switching apparatus, such as circuit breakers, and in methods of providing electrically insulated conductor connection assemblies.
These needs and others are met by embodiments of the invention, which are directed to conductor connection assemblies for electrical switching apparatus, such as circuit breakers, which are electrically insulated, yet are capable of being relatively easily unfastened.
As one aspect of the invention, a conductor connection assembly comprises: a first electrical conductor comprising a body portion and an end portion; a second electrical conductor comprising a body portion and an end portion; a fastening mechanism structured to electrically and mechanically connect the end portion of the first electrical conductor to the end portion of the second electrical conductor; and an insulator structured to overlay and electrically insulate the fastening mechanism. The end portion of the first electrical conductor, the end portion of the second electrical conductor, and the fastening mechanism form a joint, wherein the joint is structured to be fastenable and unfastenable, and wherein, when the joint is fastened and the insulator is overlaying the fastening mechanism, the joint is electrically insulated.
When the joint is fastened, the end portion of the first electrical conductor overlaps the end portion of the second electrical conductor. The end portion of the first electrical conductor may include a receptacle, wherein the receptacle is structured to receive the end portion of the second electrical conductor. The first electrical conductor may comprise an insulated tubular covering and a first round conductor including a plurality of resilient fingers. The end portion of the second electrical conductor may comprise a second round conductor. The resilient fingers may be structured to receive and retain the second round conductor of the second electrical conductor. When the joint is fastened, the second round conductor may be disposed within the resilient fingers of the first electrical conductor and the second insulated tubular covering of the second electrical conductor may overlap the resilient fingers of the first electrical conductor.
The end portion of the first electrical conductor may be a first protrusion extending outwardly from the body portion of the first electrical conductor, and the end portion of the second electrical conductor may be a second protrusion extending outwardly from the body portion of the second electrical conductor. Each of the first protrusion and the second protrusion may comprise an inner surface, an outer surface disposed opposite and distal from the inner surface, and an aperture. The fastening mechanism may comprise a fastener, wherein the fastener is structured to be inserted through the aperture of the first protrusion, into the aperture of the second protrusion, and fastened, in order to electrically connect the inner surface of the first protrusion to the inner surface of the second protrusion, thereby electrically connecting the first electrical conductor to the second electrical conductor. The fastener may include a first end having an enlarged head and a second end disposed opposite and distal from the enlarged head, and the second end of the fastener may be threaded. The aperture of the first protrusion of the first electrical conductor may further comprise a counter-bore extending from the outer surface of the first protrusion toward the inner surface of the first protrusion, wherein the enlarged head of the fastener is receivable within the counter-bore, and wherein the aperture of the second protrusion of the second electrical conductor is a threaded aperture structured to align with the aperture of the first electrical conductor and to receive the second end of the fastener. The insulator may be disposed in the counter-bore of the first protrusion of the first electrical conductor over the enlarged head of the fastener.
The body portion of the first electrical conductor may comprise an electrically conductive interior and an electrically insulative exterior overlaying the electrically conductive interior of the first electrical conductor, and the body portion of the second electrical conductor may comprise an electrically conductive interior and an electrically insulative exterior overlaying the electrically conductive interior of the second electrical conductor. When the joint is fastened, the electrically conductive interior of the first electrical conductor may abut the electrically conductive interior of the second electrical conductor, in order to electrically connect the first electrical conductor to the second electrical conductor, and the electrically insulative exterior of the first electrical conductor may abut the electrically insulative exterior of the second electrical conductor, in order to electrically insulate the joint. When the joint is fastened, the end portion of the first electrical conductor may abut the end portion of the second electrical conductor at an intersection, and the threaded fastener may be disposed within the through hole and threadingly engage the threaded aperture perpendicularly with respect to the intersection.
The conductor connection assembly may be a conductor connection assembly of a circuit breaker, wherein the circuit breaker includes a line terminal, a load terminal, a line conductor and a load conductor. The first electrical conductor may comprise one of the line terminal and the load terminal, and the second electrical conductor may comprise a corresponding one of the line conductor and the load conductor.
As another aspect of the invention, a method for providing an electrically insulated conductor connection assembly comprises: electrically connecting an end portion of a first electrical conductor to an end portion of a second electrical conductor; fastening the end portion of the first electrical conductor to the end portion of the second electrical conductor using a fastening mechanism, thereby forming a joint; and applying an insulator over the fastening mechanism, in order to electrically insulate the joint. The joint is unfastenable after applying the insulator.
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 power circuit breakers, although it will be appreciated that they could also be applied to electrically insulate the conductor connection assemblies of any known or suitable 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 power circuit breakers.
Directional phrases used herein, such as, for example, left, right, front, back, top, bottom 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 terms “fastener” and “fastening mechanism” refer to any suitable connecting or tightening material or device and expressly includes, but is not limited to, resilient members (e.g., without limitation, resilient fingers) structured to bias against, and thereby secure another component, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts.
As employed herein, the term “electrical conductor” refers to any known or suitable component expressly intended to conduct electrical current and expressly includes, but is not limited to, electrical terminals (e.g., without limitation, line terminals; load terminals) and electrically conductive components (e.g., without limitation, electrical wires; electrical cables; line conductors; load conductors; bus bars; load bus; line bus) structured to be electrically connected to such electrical terminals.
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).
Among other improvements, the conductor connection assemblies disclosed herein have been designed to provide joints between electrical conductors which are sufficiently electrically insulated from surrounding electrically conductive components (e.g., without limitation, metallic components of a circuit breaker or circuit breaker mounting apparatus), while the components of the joints are relatively easy to unfasten in comparison with, for example, known conductor connection assemblies in which the entire joint is encapsulated with an electrical insulator (e.g., without limitation, an electrically insulative epoxy coating). As a result, the components of the joint of the disclosed electrically insulated conductor connection assemblies can be unfastened (e.g., disassembled) in order to, for example, replace a component that has failed, without requiring the entire conductor connection assembly, or electrical components electrically connected thereto, to be replaced. The following examples disclose several ways of accomplishing these results.
In each example shown and described herein, like components are numbered similarly. For example, the various components of the conductor connection assembly embodiment shown and described with respect to
More specifically, when the joint 20 is fastened, portion 8 of the first electrical conductor 4, which in the example of
Accordingly, the disclosed method for providing the electrically insulated conductor connection assembly 2 involves the steps of overlapping the first protrusion 9 of the first electrical conductor 4 with the second protrusion 15 of the second electrical conductor 10, aligning the first aperture 40 with the second aperture 42, and inserting the fastener 16 through the first aperture 40 into the second aperture 42 and fastening it to secure the joint 20. The electrically insulative plug 18 is then applied to overlay the fastener 16, in order to electrically insulate the joint 20. In the example of
It will be appreciated that the line conductor connection assembly 2′ and the method of electrically insulating the same are substantially similar to those previously discussed in connection with the load conductor connection assembly 2. For economy of disclosure, the components of the line conductor connection assembly 2′ include the same reference numbers as load conductor connection assembly 2, but are distinguished by the addition of a prime symbol to each reference number (e.g., without limitation, line terminal 4′ and line conductor 10′).
Accordingly, the conductor connection assemblies 2,2′ in the example of
More specifically, each of the first and second protrusions 109,115 of the first and second electrical conductors 104,110, respectively include an inner surface 132 and 134, and an outer surface 136 and 138 disposed opposite and distal from the inner surface 132 and 134 (see also, inner surfaces 32 and 34 and outer surfaces 36 and 38 of first and second protrusions 109 and 115, respectively, and inner surfaces 32′ and 34′ and outer surfaces 36′ and 38′ of the first and second protrusions 9′ and 15′, respectively, of
The example fastener 116 (
The body portion 106 of first electrical conductor 104 comprises an electrically conductive interior 150 (e.g., without limitation, copper; metal) and an electrically insulative exterior 152 (e.g., without limitation, an electrically insulative epoxy coating; electrically insulative plastic; electrically insulative rubber). Similarly, the body portion 112 of second electrical conductor 110 comprises an electrically conductive interior 154 and an electrically insulative exterior 156 overlaying the interior 154. When the joint 120 is fastened, as shown in
The second electrical conductor 210 also includes an insulated tubular covering 228, which as best shown in
In order to electrically insulate the joint 320, an electrically insulating plug 318 is disposed within an aperture 319 of the circuit breaker 50′ at a location opposite and distal from the threaded fastener 316. It will, however, be appreciated that the joint 320 could alternatively be insulated using any known or suitable insulator (e.g., without limitation, electrically insulative epoxy; electrically insulative covering) other than the electrically insulative plug 318, without departing from the scope of the invention.
It will be appreciated that the disclosed electrically insulated conductor connection assemblies 2,2′,102,202,302 and components (e.g., without limitation, first electrical conductor 4,4′,104,204,304; second electrical conductor 10,10′, 110,210,310; fastening mechanisms 16,116,216,316; insulator 18,118,218,318) thereof could be employed individually or in any suitable combination. It will also be appreciated that such conductor connection assemblies 2,2′,102,202,302 could be employed in any suitable number and configuration as part of a wide variety of electrical switching apparatus such as, for example and without limitation, the power circuit breakers 50,50′, previously discussed in connection with
Accordingly, the disclosed conductor connection assemblies 2,2′, 102,202,302 provide joints 20,20′, 120,220,320 in which electrically conductive components (e.g., without limitation, first electrical conductor 4,4′,104,204,304; second electrical conductor 10,10′, 110,210,310; fastening mechanisms 16,116,216,316; and insulators 18,118,218,318) are effectively electrically connected and electrically insulated from surrounding electrically conductive components, yet the joints 20,20′,120,220,320 are also capable of being relatively easily unfastened and refastened, without requiring complete replacement of the electrical conductor assembly 2,2′,102,202,302, and/or electrical components (e.g., without limitation, power circuit breakers 50,50′) to which they are electrically connected, to be replaced.
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.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5120268 | Gerrans | Jun 1992 | A |
| 5221214 | Martin | Jun 1993 | A |
| 5704799 | Wood | Jan 1998 | A |
| 5801465 | Yamada | Sep 1998 | A |
| 6373358 | Davies et al. | Apr 2002 | B1 |
| 7053327 | Benke et al. | May 2006 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20080230359 A1 | Sep 2008 | US |
