Patent Application
20140253264
1. Field of the Invention
The disclosed and claimed concept relates to circuit breakers and, more specifically, to a slot motor for a circuit breaker wherein the slot motor includes a multi-piece cover assembly.
2. Background Information
Circuit breakers, including molded case circuit breakers, have at least one pair of separable contacts. A first contact is fixed within the molded case housing and the other contact, the “movable contact,” is coupled to an operating mechanism. Both contacts are disposed on “arms” that are in electrical communication with either the line or load coupled to the circuit breaker. The operating mechanism is structured to more the movable contact between a first, open position wherein the movable contact is spaced from the fixed contact, and a second, closed position wherein the fixed and movable contacts are in contact and electrical communication. The operating mechanism may be operated manually or by the circuit breaker's trip mechanism. To enhance the speed of separation of the contacts, the contacts may be disposed within a slot motor.
A slot motor is a ring, i.e. loop-shaped device, or partial ring, made of magnetically permeable material which is disposed about, or partially about, the contacts and contact arms of a circuit breaker. When the circuit is live, an electrical arc may be drawn between the electrical contacts during separation. The electrical current interacts electromagnetically with the slot motor to induce a magnetic field in the magnetic material of the slot motor which in turns interacts with the separating contact arms to accelerate the contact opening process.
In one embodiment, slot motors generally have two assemblies, an upper assembly and a lower assembly. Both upper and lower assemblies include a housing assembly and a plurality of plates, or laminations, composed of the magnetically permeable material. The lower assembly is disposed below the fixed contact. As shown in
In a full loop embodiment, the upper slot motor, i.e. the inverted U-shaped assembly included a U-shaped housing assembly. The upper slot motor housing assembly included an inner U-shaped member with forward and aft outwardly extending, depending sidewalls. Further, the tips of the tines included an outwardly extending depending sidewall that extended between the forward and aft sidewalls. Thus, the U-shaped magnetically permeable members could be moved longitudinally (in a direction parallel to the axis of the tines) into the upper slot motor housing assembly.
A disadvantage of such a U-shaped housing assembly was that, in view of the desired thinness of the U-shaped housing assembly walls, there were difficulties in molding the U-shaped housing assembly. For example, the tines of the U-shaped housing assembly tended to collapse toward each other. One solution to this problem was to create a two-piece housing, assembly having mirror image elements. These elements were coupled to each other with abutting surfaces. That is, the ends of the separate elements abutted each other at the interface. In such embodiments, the ends of the separate elements minimally overlapped, but, as used herein, surfaces with such a minimal amount of overlap shall be identified as “abutting surfaces.” Such abutting surfaces could be subject to electrical arcing therebetween, i.e. the arc could penetrate the interface. It is further noted that the distal ends of the upper slot motor were maintained in a spaced relationship by the stationary contact.
In another embodiment, the slot motor is a partial loop. That is, the slot motor extends under the fixed contact and upwardly on either side of the path of travel of the movable contact. Thus, the partial loop does not include an upper cross member and is shaped like an upright “U.” A slot motor that is a partial loop is, essentially, as effective as a full loop slot motor in that the accelerating forces are primarily generated near the point that the arc is generated, i.e. near the stationary contact. Thus, as a partial loop slot motor, i.e. a slot motor having an upright U-shape, does not have an upper cross-member, a partial loop slot motor can fit within a smaller circuit breaker housing assembly and takes up less space within such a circuit breaker housing assembly.
The housing assembly for a partial loop slot motor included a forward U-shaped wall with an axially depending sidewall. In this configuration, the housing assembly defined a pocket into which U-shaped magnetically permeable members could be placed. That is, the U-shaped magnetically permeable members were moved axially into the partial loop slot motor housing assembly. In this configuration, the partial loop slot motor housing assembly did not cover the of side of the magnetically permeable members, i.e. the side opposite the housing assembly forward wall. Tape, or a similar material, was used to protect the of side of the magnetically permeable members, it is noted that a two-piece upright U-shape housing assembly, wherein the tips of the U-shape housing assembly were not separated by the stationary contact would be subject to collapse. That is, one problem with a two-piece upright U-shape housing assembly would be that the pieces could pivot relative to each other.
There is, therefore, a need for a slot motor housing assembly for a partial loop slot motor, i.e. a slot motor having an upright U-shape, wherein the slot motor housing assembly is easy to manufacture. There is a further need for a partial loop slot motor housing assembly that resists arcing between a multiple piece housing assembly. There is a further need for a partial loop slot motor housing assembly that resists the collapse of the partial loop slot motor housing assembly. There is a further need for the improved slot motor to be compatible with existing circuit breaker housings.
These needs, and others, are met by at least one embodiment of the disclosed concept which provides a two-piece slot motor housing assembly having an overlapping interface. As noted above, single piece housing assemblies have molding issues. Thus, the two-piece construction provides for a housing assembly that is easy to manufacture. The overlapping interface resists arcing between the multiple piece housing assembly. Further, each piece of the housing assembly is structured to be coupled to the arc chute housing. The support provided by the arc chute housing maintains the slot motor housing assembly elements in a spaced relationship. That is, the two pieces of the slot motor housing assembly do not collapse toward each other. It is noted that the stated problems are solved by the configuration, i.e. shape, of the two-piece slot motor housing assembly.
A full understanding of the disclosed and claimed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
The following directional terms apply to the slot motor assembly: the “longitudinal direction” extends in the direction of the longitudinal axis of the slot motor legs or tines, as described below. That is, the “longitudinal direction” is generally the vertical direction as shown in the Figures, The “lateral direction” extends in a direction generally perpendicular to the “longitudinal direction” and generally horizontally across both the motor legs or tines, as described below. The “axial direction” is generally perpendicular to both the “longitudinal direction” and the “lateral direction.” That is, the “axial direction” extends generally horizontally between the slot motor legs or tines, as described below. Further, with respect to the slot motor assembly, as used herein the “inner” side is the side adjacent the stationary contact, as described below, i.e. generally the inner side of the U-shaped assembly. Conversely, the “outer” side is the side disposed away from the stationary contact, as described below, i.e. generally the outer side of the U-shaped assembly.
As used herein, “coupled” means a link between two or more elements, whether direct or indirect, so long as a link occurs. An object resting on another object held in place only by gravity is not “coupled” to the lower object unless the upper object is otherwise maintained substantially in place. That is, for example, a book on a table is not coupled thereto, but a book glued to a table is coupled thereto.
As used herein, “directly coupled” means that two elements are directly in contact with each other.
As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. Similarly, two or more elements disposed in a “fixed relationship” means that two components maintain a substantially constant orientation relative to each other. As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body.
As used herein, “associated” means that the identified components are related to each other, contact each other, and/or interact with each other. For example, an automobile has four tires and four hubs, each hub is “associated” with a specific tire.
As used herein, “engage,” when used in reference to gears or other components having teeth, means that the teeth of the gears interface with each other and the rotation of one gear causes the other gear or other component to rotate/move as well. As used herein, “engage,” when used in reference to components not having teeth means that the components are biased against each other.
Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, 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 used herein, “correspond” indicates that two structural components are similar in size, shape or function. With reference to one component being inserted into another component or into an opening in the other component, “corresponding ” means components are sized to engage or contact each other with a minimum amount of friction. Thus, an opening which corresponds to a member is sized slightly larger than the member so that the member can pass through the opening with a minimum amount of friction. This definition is modified if the two components are said to fit “snugly” together. In that situation, the difference between the size of the components is even smaller whereby the amount of friction increases. If one or more components are resilient, a “snugly corresponding” shape may include one component, e.g. the component defining the opening being smaller than the component inserted therein. Further, as used herein, “loosely correspond” means that a slot or opening is sized to be larger than an element disposed therein. This means that the increased size of the slot or opening is intentional and is more than a manufacturing tolerance.
As used herein, “more than minimally overlap” means that elements overlap by more than 0.02 inch.
As used herein, “effectively overlap” means that elements overlap by more than 0.05 inch.
As used herein, “efficiently overlap” means that elements overlap by more than 0.1 inch.
As used herein, “at” means on or near.
As shown in
Each conductor assembly 13, shown in
The stationary conductor 40 and stationary contact 42 are also part of a stationary contact assembly 60, shown in
The arc chute 70 includes a first lateral side planar member 72, a second lateral side planar member 74 and a number of conductive plates 76. The conductive plates 76 are disposed in a spaced relation to each other and disposed between the arc chute first lateral side planar member 72 and the arc chute second lateral side planar member 74. The arc cute 70 is disposed over the stationary conductor body medial portion 66 adjacent the stationary conductor body first end 64. Arc chute 70 is structured to absorb and dissipate an arc created by separation of the contacts 14. Arc chute 70 is sized to correspond to, i.e. fit within, a contact chamber 34. That is, the spacing between the arc chute first lateral side planar member 72 and the arc chute second lateral side planar member 74 generally corresponds to the width of a contact chamber 34. In one embodiment, the width of the arc chute 70 loosely corresponds to the width of the contact chamber 34. Each arc chute lateral side planar member 72, 74 further includes an extension 78 that extends toward the stationary conductor body first end 64. The slot motor assembly 80 is a U-shaped assembly. As used herein, a “U-shaped” element includes a bight (or cross member) and two tines (or legs). Further, as used herein, the tines of a U-shaped body extend generally perpendicular to, and in the same direction from, the bight. The transition between the bight and the tines may be curved, as shown in
As shown in
Similarly, the second J-shaped body 94, shown in
The second J-shaped body inner sidewall 116 is generally L-shaped and consists of two generally planar members 119. The second J-shaped body depending, sidewalls 117, 118 (
The first J-shaped body 92 and the second, J-shaped body 94 may be coupled to form a U-shaped assembly 120 (
The first J-shaped body first end 100 overlaps the second J-shaped body first end 110 in an axial direction, and, the first J-shaped body first end 100 further overlaps the second J-shaped body first end 110 in a longitudinal direction. That is, the first J-shaped body inner sidewall 106 overlaps the second J-shaped body inner sidewall 116, and, the first J-shaped body depending sidewalls 107, 108 overlap the second J-shaped body depending sidewalls 117, 118. More than minimally overlapping elements resist arc penetration. That is, it is the shape of the bodies, and the interface, that solves the problem of arcing between a multiple piece housing assembly. In one exemplary embodiment, the first J-shaped body first end 100 more than minimally overlaps the second J-shaped body first end 110. Resistance to arc penetration is improved if the overlap is more substantial. Accordingly, in another exemplary embodiment, the first J-shaped body first end 100 effectively overlaps the second J-shaped body first end 110. Further, in another exemplary embodiment, the first J-shaped body first end 100 efficiently overlaps the second J-shaped body first end 110.
Each of the first and second J-shaped body second ends 104, 114 include a tab 130, 132 (respectively, and as shown in
When the stationary contact assembly 60 is assembled, the slot motor assembly 80 is disposed with the bight of the slot motor assembly 80 disposed in the gap between the stationary conductor body first end 64 and the stationary conductor body medial portion 66. The tines of the slot motor assembly 80 extend upwardly. Thus, as the movable contact 46 moves between the first and second positions, the movable contact 46 moves between the tines of the slot motor assembly 80. An arc than forms during separation of the contacts 14 is not likely to penetrate the slot motor assembly housing assembly 90 because the first and second J-shaped bodies 92, 94 more than minimally overlap at their interface.
While specific embodiments of the disclosed and claimed 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 disclosed and claimed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
