Patent Application
20080191819
1. Field of the Invention
The invention relates to electrical switching apparatus, such as, for example, circuit interrupters and, more particularly, to circuit interrupters employing a slot motor. The invention further relates to slot motors. The invention also relates to slot motor housings.
2. Background Information
Circuit interrupters, such as circuit breakers, are employed in diverse capacities in power distribution systems. A circuit breaker may include, for example, a line conductor, a load conductor, a fixed contact and a movable contact, with the movable contact being movable into and out of electrically conductive engagement with the fixed contact. This switches the circuit breaker between an on or closed position and an off or open position, or between the on or closed position and a tripped or tripped off position. The fixed contact is electrically conductively engaged with one of the line and load conductors, and the movable contact is electrically conductively engaged with the other of the line and load conductors. The circuit breaker may also include an operating mechanism having a movable contact arm upon which the movable contact is disposed.
In order to enhance the speed of separation of the separable contacts, the contacts may be disposed within a slot motor, which increases interruption performance. Ring-shaped or loop-shaped slot motors typically have two assemblies, an upper assembly and a lower assembly. Both of the upper and lower assemblies include a corresponding insulative housing and a plurality of plates composed of magnetically permeable material (e.g., steel), which surrounds the separable contacts and the movable contact arm of the circuit breaker. The lower assembly is disposed below the fixed contact. When the power circuit is live, an electrical arc may be drawn between the separable 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 contacts and the movable contact arm to accelerate the contact opening process. Examples of slot motors are disclosed in U.S. Pat. Nos. 4,375,021; 4,546,336; 4,546,337; 4,549,153; 4,970,482; 5,694,098, and 6,281,459.
As shown in
The one-piece housing assembly 1 is molded from a suitable plastic that may cause warping of this molded component. For example, a relatively large one-piece housing may come out of the mold (not shown) with the legs 4,5 being bent inward or outward, thereby making it difficult to insert the steel lamination plates 2 within the housing assembly 1 and, also, difficult to insert the inverted U-shaped assembly in the base of the circuit breaker (not shown).
Accordingly, there is room for improvement in electrical switching apparatus, such as circuit interrupters, employing a slot motor.
There is further room for improvement in slot motors.
There is also room for improvement in slot motor housings.
These needs and others are met by embodiments of the invention, which provide two insulative housing portions that are structured to interlock with one another to form a generally U-shaped insulative slot motor housing, and to cooperatively receive a plurality of generally U-shaped slot motor laminations.
In accordance with one aspect of the invention, a slot motor housing comprises: a first insulative housing portion; and a second insulative housing portion, wherein the first and second insulative housing portions are structured to interlock with one another to form a generally U-shaped insulative slot motor housing, and wherein the first and second insulative housing portions are further structured to cooperatively receive a plurality of generally U-shaped slot motor laminations.
Each of the first and second insulative housing portions may include a first flange outer portion having a first end with a plurality of first steps, a second flange outer portion having a second end with a plurality of second steps, and a third inner portion intermediate the first and second flange outer portions. The first end and the first steps of the first flange outer portion of the first insulative housing portion may be structured to interlock with the second end and the second steps of the second flange outer portion of the second insulative housing portion, and the first end and the first steps of the first flange outer portion of the second insulative housing portion may be structured to interlock with the second end and the second steps of the second flange outer portion of the first insulative housing portion.
Each of the first and second insulative housing portions may include a first flange outer portion, a second flange outer portion, and a third inner portion intermediate the first and second flange outer portions, the third inner portion having an end with a plurality of steps. The end and the steps of the third inner portion of the first insulative housing portion may be structured to interlock with the end and the steps of the third inner portion of the second insulative housing portion.
A first one of the steps of the third inner portion of the first insulative housing portion may be structured to overlap a second one of the steps of the third inner portion of the second insulative housing portion, and a first one of the steps of the third inner portion of the second insulative housing portion may be structured to overlap a second one of the steps of the third inner portion of the first insulative housing portion.
As another aspect of the invention, a slot motor portion comprises: a plurality of generally U-shaped slot motor laminations; a first insulative housing portion; and a second insulative housing portion; the first and second insulative housing portions interlock with one another to form a generally U-shaped insulative slot motor housing, and the first and second insulative housing portions cooperatively receive the generally U-shaped slot motor laminations.
As another aspect of the invention, a circuit interrupter comprises: a housing; separable contacts; an operating mechanism structured to open and close the separable contacts; a power conductor comprising a first conductor and a second reverse loop conductor, the second reverse loop conductor carrying one of the separable contacts; and a slot motor comprising: a first slot motor portion, and a second slot motor portion comprising: a plurality of generally U-shaped slot motor laminations, a first insulative housing portion, and a second insulative housing portion, the first and second insulative housing portions interlock with one another to form a generally U-shaped insulative slot motor housing, and the first and second insulative housing portions cooperatively receive the generally U-shaped slot motor laminations.
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:
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
As employed herein, the statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly.
As employed herein, the terms “generally U-shaped” or “generally U-shape” or “general U-shape” shall mean that the shape of a corresponding structure has the general shape of the letter “U” in which the bottom of such letter or structure is rounded, generally round, square, generally square, or partially round and partially square, or has the general shape of a base member with two leg (or arm) members extending normal or generally normal from the ends of the base member.
As employed herein, the terms “generally L-shaped” or “generally L-shape” or “general L-shape” shall mean that the shape of a corresponding structure has the general shape of the letter “L” in which the bottom of such letter or structure is rounded, generally round, square, generally square, or partially round and partially square, or has the general shape of a base member with one leg (or arm) member extending normal or generally normal from the end of the base member.
The invention is described in association with a circuit breaker having a single pole, although the invention is applicable to a wide range of circuit interrupters having any suitable number of poles (e.g., one; two; three or more).
The operating mechanism 10 controls the spring-biased movable contact arm 18 to pivot the movable contact 8 into and out of electrical contact with the corresponding stationary contact 9. A contact arm spring 28 biases the second end 20 of the movable contact arm 18, proximate the operating mechanism crossbar 22, in order to maintain the closed position (shown in phantom line drawing) of the pair of movable and stationary contacts 8,9.
Referring to
As shown in
Referring to
The first insulative housing portion 32 is preferably symmetrical or identical to the second insulative housing portion 34.
The housing portions 32,34 are preferably made of molded plastic, such as, for example and without limitation, cellulose-filled melamine formaldehyde. Preferably, the housing portions 32,34 are structured to outgas responsive to an arc (not shown) when the operating mechanism 10 opens the energized separable contacts 8,9 of
Each of the first and second insulative housing portions 32,34 includes the first flange outer portion 42 having a first end 50 with a plurality of first steps 52, the second flange outer portion 44 having a second end 54 with a plurality of second steps 56, and the third inner portion 46 intermediate the first and second flange outer portions 42,44. For the pair of the housing portions 32,34, the first end 50 and the first steps 52 of the first flange outer portion 42 of the housing portion 32 are structured to interlock with the second end 54 and the second steps 56 of the second flange outer portion 44 of the housing portion 34, and the first end 50 and the first steps 52 of the first flange outer portion 42 of the housing portion 34 are structured to interlock with the second end 54 and the second steps 56 of the second flange outer portion 44 of the housing portion 32. The first and second steps 52,56, when interlocked as shown in
The third inner portion 46 of each of the first and second insulative housing portions 32,34 has an end 58 with a plurality of steps 60. The end 58 and the steps 60 of the third inner portion 46 of the first insulative housing portion 32 are structured to interlock with the end 58 and the steps 60 of the third inner portion 46 of the second insulative housing portion 34.
Referring to
As shown in
As compared to the relatively larger one-piece molded slot motor housing 1 of
The disclosed two-piece slot motor housing 30 solves the problem of “difficult” plastics causing warping. The molding of the relatively smaller first and second insulative housing portions 32,34 yields relatively straighter parts. A relatively large one-piece housing would come out of the mold (not shown) with the legs of the U-shape being bent inward or outward, thus, making it difficult to insert lamination steel, such as 38, within. Also, the resulting assembly could be difficult to insert in the base of the circuit breaker 6 (
Molding the example first and second insulative housing portions 32,34 of the two-piece slot motor housing 30 enables the use of plastics, such as, for example and without limitation, cellulose-filled melamine formaldehyde that gives off relatively high amounts of gasses during molding. These types of materials are desired for their performance enhancing qualities on short circuit testing of the example circuit breaker 6. These gasses need to be vented from the mold (not shown) to prevent “no fill” conditions. The disclosed configuration allows proper venting to be incorporated. It is believed that such a housing geometry molded as one-piece would be virtually impossible in mass production because of the venting required and the lack of areas to place it.
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.
