CONTACT DEPRESSION STABILIZER FOR 4 POLE MOLDED CASE CIRCUIT BREAKER

Abstract: A stabilizer clamp (39) for locking together the rods (34) that connect an operating mechanism (4) in a four pole molded case circuit breaker (4) to a rotary contact arm of the outer circuit breaker cassette, and eliminating the relative motion between the rods (34) thereby better transmitting the torque from the operating mechanism (4) and stabilizing the outer pole's operation.

Description: CONTACT DEPRESSION STABILIZER FOR 4 POLE MOLDED CASE CIRCUIT BREAKER BACKGROUND OF INVENTION The present invention is directed to a clamping apparatus for locking together rods connecting rotary contact arms in a multi-pole molded case circuit breaker. It is generally well known in the art of multi-pole circuit breakers that rotary contact arms in each circuit breaker cassette are connected together with at least one rod (usually a drive rod and a support rod) to ensure their operation in unison. During quiescent operation, (i.e. when the circuit breaker contacts are closed to allow the flow of electrical current) the operating handle of an operating mechanism is in the "ON" position. To stop the current flow manually, the handle may be shifted to the "OFF" position thereby opening the electrical contacts. Upon attainment of a pre-determined condition (trip event), such as ground fault or overload, the operating mechanism of the circuit breaker will release the forces of the mechanism operating springs and release the operating handle to a tripped position between the "ON" position and the "OFF" position. Before the circuit breaker may be turned "ON", the operating mechanism must be manually reset. This is accomplished by the operating handle placed beyond the "OFF" position against the bias of the operating mechanism springs, thereby locking the operating mechanism in position. The circuit breaker cassettes in a multi-pole molded case circuit breaker are preferably connected together with two rods interfacing a rotary contact arm in each circuit breaker cassette. In a typical three pole molded case circuit breaker, the operating mechanism is positioned upon a cassette located symmetrically between two of the circuit breaker cassettes. Stated alternatively, if the three cassettes of a three cassette circuit breaker are counted from left to right the operating mechanism is located on the second cassette. It is known to be desirable for circuit W breakers having multiple cassettes therein that all of the cassettes trip as closely in time to one another as possible. For this purpose it has been known to provide at least one and usually two rods that extend through all of the cassettes in a particular circuit breaker. The rods transmit the rotational movement within one of the cassettes, due to a trip, into an impetus for the other cassettes to also trip. Because of the mechanical nature of the connection through the rods, the first and third cassettes will change position almost immediately upon change of position of the second cassette. It is also the case that any two of the cassettes will react rapidly to any one of the cassettes experiencing a trip event. This is because the rods are actuated by the operating mechanism and since each cassette of the three pole circuit breaker is immediately adjacent or in contact with the operating mechanism no torque is lost. Since the first and third cassettes are immediately adjacent the second cassette, which is mechanically connected to the operating mechanism, there is little relative movement between the rods and they function well as intended. Four pole circuit breakers present additional difficulties with respect to simultaneous operation of the four individual cassettes housed therein because conventionally the fourth circuit breaker cassette is added at one end of what would be the arrangement of a three cassette circuit breaker. This is exclusive of any change in the operating mechanism. More particularly, the operating mechanism is still located on the second circuit breaker cassette. One of ordinary skill in the art thus appreciates that in a four pole circuit breaker a single cassette is located on one side of the cassette to which the operating mechanism is attached while two cassettes are located on the opposite side of the cassette to which the operating mechanism is attached. The rods that connect all of the cassettes in the breaker then extend further to reach the outer cassette on one side than they do on the other side. Because of relative movement between the rods and the length of the rods as it affects effective flexibility, the outer cassette may not react to movement of the operating mechanism as rapidly as would a cassette located closer to the operating mechanism. Since movement of the outer cassette as rapidly as possible is desirable, the art has sought means to speed the movement of the outer cassette. Four pole circuit breaker solutions have been attempted including the provision of additional assist mechanisms added to the outer cassette, or a wide operating mechanism which is symmetrically positioned about the rotary contact assemblies. While these alternatives do speed movement of the outer cassette they also increase manufacturing cost. Therefore, the art continues to seek a reliable and inexpensive arrangement to eliminate relative movement between the rods and speed the movement ofan outer cassette in an asymmetrically positioned four pole molded case circuit breaker. SUMMARY OF THE INVENTION In an exemplary embodiment of the invention, movement of contacts within individual cassettes of a multipole circuit breaker occasioned by a trip event or operation of the operating mechanism thereof is reliably and inexpensively effected by the addition of a clamp upon the drive rod and support rod of the breaker for example between the third and fourth cassettes of the breaker. The clamp preferably includes surface features conducive to receiving and arresting the drive rod and the support rod relative to each other. By preventing relative movement of the drive rod and support rod the outer cassette is provided with as much impetus to move due to actuation of the operating mechanism or a trip event as are the first or third cassettes, being immediately adjacent the second cassette upon which the operating mechanism is mounted. The clamp may be of a single piece of material such as metal or plastic with material removed therefrom to receive the rods or may be of more than one piece wherein the separate pieces are attachable by various means with the desired result being that relative movement between the rods is minimized. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a top perspective view of a molded case circuit breaker; Figure 2 is a perspective exploded view of a molded case circuit breaker; Figure 3 is a perspective exploded view of the stabilizer clamp and the drive rod and the support rod; Figure 4 is a perspective view of stabilizer clamp assembled on the drive rod and the support rod; Figure 5 is a perspective exploded view ofan alternate embodiment of the clamp of the invention; and Figure 6 is a perspective view of the alternate clamp assembled on the drive rod and the support rod. DESCRIPTION OF THE PREFERRED EMBODIMENT A top perspective view of a multiple circuit interrupting mechanism such as a molded case circuit breaker 2 is provided at Figure 1. Molded case circuit breaker 2 is generally interconnected within a protected circuit between multiple phases of a power source (not shown) at line end 6 and a load to be protected (not shown) at load end 8. Molded case circuit breaker 2 includes a base 10, a mid cover 12, and an accessory cover 14 having an operating handle 16 interconnected with the circuit breaker operating mechanism 4 passing through an escutcheon 18. Referring to Figure 2, an exploded view of the molded case circuit breaker 2 is provided. An accessory 20, such as an electronic trip actuator, a shunt trip actuator, an under voltage actuator, bell alarm or other type of accessory unit, is generally positioned within mid cover 12 and interfaces with operating mechanism 4. Enclosed within the base 10 and mid cover 12 are four circuit breaker cassettes, namely, a first circuit breaker cassette 22, a second circuit breaker cassette 24, a third circuit breaker cassette 26, and a fourth circuit breaker cassette 28. Each circuit breaker cassette is generally well known and may be, for example, of the rotary type. The circuit breaker illustrated (four pole) is configured to allow delivery of four phase current to the load (not shown) wherein each phase passes through one of the circuit breaker cassettes. Each circuit breaker cassette includes a rotary contact arm therein for passage of current when the rotary contact arm is closed and for preventing passage of current when the contact arm is opened. It is contemplated that the number of phases, or specific type of cassette utilized, can vary according to factors including, but not limited to, the type of load circuit being protected and the type of line input being provided to the circuit breaker. Circuit breaker cassettes are assembled within the base 10 with the first circuit breaker cassette 22 positioned at one end of the base 10 (left in Figure 2), and the fourth circuit breaker cassette 28 at the other end of the base 10 (right in Figure 2), with the second circuit breaker cassette 24 and the third circuit breaker cassette 26 positioned in between. The second circuit breaker cassette 24 is straddled by the operating mechanism 4. The operating mechanism 4 is actuated by the operating handle 16 to control the "ON" and "OFF" positions of a rotary contact arm (not shown) within the second circuit breaker cassette 24. The operating mechanism 4 is depicted as generally including, among other things, the operating handle 16, a latch 32 and additional linkages to allow interaction between the operating mechanism 4 and the second circuit breaker cassette 24. Various linkages and mechanism springs (not necessarily shown but known to the art) move the rotary contact arms in the circuit breaker cassette. Movement of the rotary contact arm in cassette 24 is transmitted to rotary contact arms in cassettes 22, 26 and 28 by a drive rod 34. The movement may be non-current related by manually or mechanically urging operating handle 16, or the accessory 20 may trigger the movement due to a current related anomaly in the circuit. The rotary contact arm within the first circuit breaker cassette 22, on one side of the operating mechanism 4, and the rotary contact arm within the third and fourth circuit breaker cassettes 26, 28, on the opposite side of the operating mechanism 4, are connected together with the drive rod 34 and the support rod 36 and move in unison based upon either a current-caused trip condition or a manually- caused condition providing a complete multi-pole circuit interruption. In the case of an imbalance system, i.e., an asymmetrical setup of circuit breaker cassettes with respect to the operating mechanism 4, the farther the drive rod 34 and support rod 36 extend from the operating mechanism 4, the more relative movement will occur between the two rods. In a four pole molded case circuit breaker, the relative movement between the drive rod 34 and the support rod 36 connecting to the forth circuit breaker cassette causes a torque loss from the operating mechanism 4 to the rotary contact arm in the fourth circuit breaker cassette 28. A stabilizer clamp 38 reduces the relative movement between the drive rod 34 and the support rod 36 and thereby allows the rods to deliver maximum torque to the rotary contact arm of cassette 28. The stabilizer clamp 38 is preferably positioned on a portion of the drive rod 34 and support rod 36 extending between the third circuit breaker cassette 26 and the fourth circuit breaker cassette 28. Referring to Figure 3, a drive rod 34, support rod 36 and clamp 38 are illustrated apart from other components of the circuit breaker and in an exploded condition. One embodiment of the stabilizer clamp 38 (as illustrated) is preferably constructed from a single piece of material (body 39). The material may be of any type capable of providing stability to the two rods. Preferred materials include but are not limited to metal and plastic. In this embodiment, openings 40 are formed in the clamp, which openings 40 are dimensioned to conform to the shape of the drive rod 34 and the support rod 36. The drive rod 34 is positioned, when the clamp is in position in a circuit breaker, through one opening 40 and the support rod 36 is positioned through the other opening 40. It is preferable that the rods are affixed in the desired position to the clamp which can be effected in several ways although a prefened anangement is to provide stabilizer clamp 38 with a slot 44 extending from one opening 40 to the other opening 40. The slot 44 and openings 40 tend to bifurcate a top portion 48 and a bottom portion 50 of clamp 38 which allows for some resilient movement between the top portion 48 and the bottom portion 50. By urging top portion 48 toward bottom portion 50 openings 40 are affected. The affect is to reduce the dimension measured from top portion 48 to bottom portion 50. Reducing this dimension in each of openings 40 causes the rods to be pinched by the clamp within each opening. The pinching action, when orchestrated to a sufficient degree will reliably return the rods and reduce relative movement therebetween. With respect to urging top portion 48 and bottom portion 50 toward one another, one prefened tightening means is a screw 46. In an embodiment where a screw is used, the screw is passed through the top portion 48 via a clearance opening 49 and threaded into the bottom portion 50 via threaded opening 51. Tightening screw 46 urges the top portion 48 and bottom portion 50 together and allows the openings 40 to embrace the rods tightly as stated above thereby locking them together. Referring to Figure 4, the stabilizer clamp 38 is illustrated as mounted on the drive rod 34 and the support rod 36 locking the rods together to prevent relative movement therebetween and reduce the torque loss that would otherwise be caused by relative movement between the rods. Figures 5 and 6 illustrate an exploded and assembled view, respectively, of an alternate clamp of the invention with respect to the drive and support rods. Figures 5 and 6 conespond in other respects to Figures 3 and 4. In Figures 5 and 6 numerals employed in the discussion of Figures 3 and 4 have been repeated for identical elements and annotated with the letter "a" for portions thereof that are similar to the foregoing embodiment but are not identical thereto. One of ordinary skill in the art will clearly understand this embodiment from a review of the drawings and reference to the foregoing discussion. While the invention has been described with reference to a prefened embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims: WHAT IS CLAIMED IS: 1. A multipole circuit breaker stabilizer clamp (38) comprising: a body (39); a plurality of openings (40) formed in said body (39) and dimensioned to accept a separate drive rod (34) and support rod (36) for a circuit breaker (2); and a body tightening device (46) capable of constricting said body (39) to reduce said openings (40) in dimension whereby a drive rod (34) and support rod (36) extending through said openings (40) are securable therein. 2. A stabilizer clamp (38) as claimed in claim 1 wherein said body (39) is constructed of metal. 3. A stabilizer clamp (38) as claimed in claim 1 wherein said body (39) is constructed of plastic. 2. A stabilizer clamp (38) as claimed in claim 1 wherein said openings (40) possess geometrical shapes complementary to a drive rod (34) and a support rod (36) to be extended therethrough. 3. A stabilizer clamp (38) as claimed in claim 1 wherein said body (39) tightening device is a screw (46). 6. A stabilizer clamp (38) as claimed in claim 1 wherein said body (39) further includes a slot (44) extending to each of said plurality of openings (40). 7. A stabilizer clamp (38) as claimed in claim 1 wherein said plurality of openings (40) is two openings. 8. A stabilizer clamp (38) as claimed in claim 1 wherein said body (39) is a single piece of material. 9. A stabilizer clamp (38) as claimed in claim 1 wherein said body (39) is two pieces of material securable to one another around a drive rod (34) and support rod (36) by a screw (46). 10. A multipole molded case circuit breaker (2) comprising: a case (10); a mid cover (12) mounted to said case (10) and defining with said case (10) an interior space; a plurality of circuit breaker cassettes (22) mounted in said interior space; an operating mechanism (4) for opening and closing said circuit breaker cassettes (22) in operable communication with said cassettes; a plurality of rods (34) operably connecting said circuit breaker cassettes (22) to one another; and a stabilizer clamp (38) mated with said rods (34) to reduce relative movement therebetween. 11. A multipole molded case circuit breaker (2) as claimed in claim 10 wherein said clamp further comprises: a body (39); a plurality of openings (40) formed in said body (39) and dimensioned to accept a separate drive rod (34) and support rod (36) for a circuit breaker (2); and a body tightening device (46) capable of constricting said body to reduce said openings (40) in dimension whereby a drive rod (34) and support rod (36) extending through said openings (40) are securable therein. 12. A multipole molded case circuit breaker (2) as claimed in claim 1 1 wherein said body (39) is constructed of metal. 13. A multipole molded case circuit breaker (2) as claimed in claim 11 wherein said body (39) is constructed of plastic. 14. A multipole molded case circuit breaker (2) as claimed in claim 1 1 wherein said openings (40) possess geometrical shapes complementary to a drive rod (34) and a support rod (36) to be extended therethrough. 15. A multipole molded case circuit breaker (2) as claimed in claim 1 1 wherein said body tightening device is a screw (46). 16. A multipole molded case circuit breaker (2) as claimed in claim 11 wherein said body (39) further includes a slot (44) extending to each of said plurality of openings (40). 17. A multipole molded case circuit breaker (2) as claimed in claim 1 1 wherein said plurality of openings (40) is two openings. 18. A multipole molded case circuit breaker (2) as claimed in claim 1 1 wherein said body (39) is a single piece of material. 19. A multipole molded case circuit breaker (2) as claimed in claim 11 wherein said body (39) is two pieces of material securable to one another around a drive rod (34) and support rod (36) by a screw (46).

Inventors: CASTONGUAY ROGER NEIL, LARRANAGA JAVIER, CASTONGUAY, ROGER, NEIL, LARRANAGA, JAVIER
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 2001
Main classification: H01H
IPC codes: H01H71, H01H73