Claims
- 1. A molded case circuit breaker, comprising:
- a housing having a base portion and a cover portion, said cover portion having an aperture;
- a pair of separable main contacts disposed in said base portion;
- an operating mechanism, operatively coupled to said separable main contacts;
- a handle, operatively coupled to said operating mechanism for manual operation of said circuit breaker between an "on " position and an "off" position; said handle having a handle base portion and a handle portion extending outwardly through said aperture in said cover, said handle base portion closing off only a portion of said aperture when said circuit breaker is in one of said "on" position or a said "off" position; and
- barrier means movable with said handle portion for a portion of the travel of said handle portion for providing a barrier for closing off the remainder of said aperture in said cover portion.
- 2. A molded case circuit breaker as recited in claim 1, further including first stop means for stopping movement of said barrier means in a first direction.
- 3. A molded case circuit breaker as recited in claim 2, further including second stop means for stopping movement of said barrier in a second direction.
- 4. A molded case circuit breaker as recited in claim 1, further including means for preventing removal of said cover portion when said circuit breaker is in the "on" position.
- 5. A molded case circuit breaker as recited in claim 4, wherein said preventing means is integrally formed with said carrying means.
- 6. A molded case circuit breaker as recited in claim 1, wherein said cover portion is formed with sidewalls adjacent said aperture, said sidewalls formed with a recess for receiving said carrying means.
- 7. A molded case circuit breaker as recited in claim 6, wherein said carrying means is fastened to said recess in said sidewall with an adhesive.
- 8. A molded case circuit breaker as recited in claim 4, wherein said preventing means includes one or more blocks disposed adjacent said carrying means.
- 9. A molded case circuit breaker as recited in claim 8, wherein said blocks are generally rectangular in shape.
- 10. A molded case circuit breaker as recited in claim 9, wherein said blocks are disposed such that their longitudinal axes are generally parallel to the longitudinal axis of said circuit breaker.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No. 256,878, filed on Oct. 12, 1988.
The invention disclosed herein relates to molded case circuit breakers The following seven patent applications all relate to molded case circuit breakers and were filed on Aug. 1, 1988: Ser. No. 226,500, entitled RUBBER STOPS IN OUTSIDE POLES, William E. Beatty, Jr., Lawrence J Kapples, Lance Gula and Joseph F. Changle; Ser. No. 226,648, entitled CT QUICK CHANGE ASSEMBLY, by Jere L McKee, William E. Beatty, Jr. and Glenn R. Thomas; Ser. No. 226,503, entitled CROSS-BAR ASSEMBLY, by Jere L. McKee, Lance Gula, and Glenn R. Thomas; Ser. No. 226,649, entitled LAMINATED COPPER ASSEMBLY, by Charles R. Paton; Ser. No. 226,650, entitled CAM ROLL PIN ASSEMBLY, by Lance Gula and Jere L. McKee; Ser. No 226,655, entitled COMBINATION BARRIER AND AUXILIARY CT BOARD by Gregg Nissly, Allen B. Shimp and Lance Gula; Ser. No 226,654, entitled MODULAR OPTION DECK ASSEMBLY by Andrew J. Male.
The following four commonly assigned U.S. Patent Applications were filed on Oct. 12, 1988 and all relate to molded case circuit breakers: Ser. No. 256,881 entitled SCREW ADJUSTABLE CLINCH JOINT WITH BOSSES, by James N. Altenhof, Ronald W. Crookston, Walter V. Bratkowski, and J. Warren Barkell; Ser. No. 56,879 entitled TAPERED STATIONARY CONTACT LINE COPPER, by Ronald W. Crookston; Ser. No. 256,880, entitled SIDE PLATE TAPERED TWIST-TAB FASTENING DEVICE FOR FASTENING SIDE PLATES TO THE BASE, by K. Livesey and Albert E. Maier; Ser. No. 56,878, entitled TWO-PIECE CRADLE LATCH FOR CIRCUIT BREAKER, by Albert E. Meier and William G. Eberts.
The following commonly assigned U.S. Patent Applications also relate to molded case circuit breakers: Ser. No 260,848, filed on Oct. 21, 1988 entitled UNRIVETED UPPER LINK SECUREMENT, by Joseph Changle and Lance Gula; Ser. No 331,769, filed on Apr. 3, 1989 entitled ARC RUNNER, CONTAINMENT SUPPORT ASSEMBLY by Charles Paton, Kurt Grunert and Glen Sisson; Ser. No. 331,920, filed on Mar. 31, 1989 entitled "EXTENDER SPRING FOR INCREASED MAGNETIC TRIP SETTINGS", by Kurt Grunert.
Lastly, the following patent application is being filed on even date herewith: Ser. No. 343,037, entitled TWO PIECE CRADLE LATCH, KEY BLOCKS AND SLOT MOTOR FOR CIRCUIT BREAKER, by Alfred E. Maier, William G. Eberts and Richard E White.
1. Field of the Invention
This invention relates to molded case circuit breakers and more particularly to a two piece cradle latch having a non-heat-treated portion and a heat treated portion defining latch and reset surfaces, securely fastened to the non-heat-treated cradle portion and to means for holding the handle barrier in place to prevent arc products from escaping around the handle through the cover and a cover interlock which prevents removal of the cover when the circuit breaker is in the "on" position.
2. Description of the Prior Art
Molded case circuit breakers are generally old and well known in the art. Examples of such circuit breakers are disclosed in U.S. Pat. Nos. 4,489,295; 4,638,277; 4,656,444 and 4,679,018. Such circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload and relatively high level short circuit condition. An overload condition is normally about 200-300 percent of the nominal current rating of the circuit breaker. A high level short circuit condition can be 1000 percent or more of the nominal current rating of the circuit breaker.
Molded case circuit breakers include at least one pair of separable contacts which may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an overcurrent condition. In the automatic mode of operation, the contacts may be opened by an operating mechanism, controlled by an electronic trip unit, or by magnetic repulsion forces generated between the stationary and movable contacts during relatively high levels of overcurrent.
In one automatic mode of operation, the contact assemblies for all poles are tripped together by an electronic trip unit and a mechanical operating mechanism. More particularly, the electronic trip unit is provided with current sensors to sense an overcurrent condition. When an overcurrent condition is sensed, the current transformers provide a signal to the electronic circuitry within the electronic trip unit to actuate the operating mechanism to cause the main contacts to be separated.
In the other automatic mode of operation, the contact arm assemblies are disengaged from the mechanical operating mechanism and are blown open by magnetic repulsion forces. More particularly, magnetic repulsion members or shunts are used to allow the contact arm, which carries the movable main contact, to pivot. Each magnetic repulsion member is generally V-shaped defining two legs. During relatively high level overcurrent conditions, magnetic repulsion forces are generated between the legs of the magnetic repulsion member as a result of current flowing through the legs in opposite directions. At a relatively high level overcurrent condition, these magnetic repulsion forces cause the contact arm carrying the movable main contact to be blown open.
During a blow open condition, each contact arm is operated independently of the mechanical operating mechanism. For example, for a three phase circuit breaker having a high level overcurrent on the A phase; only the A phase contact arm will be blown open by its respective repulsion member. The contact arms for the B and C phases would remain closed and thus are unaffected by the operation of the A phase. The contact arms for the B and C phases are tripped by the electronic trip unit and the operating mechanism. This is done to prevent a condition known as single phasing, which can occur for circuit breakers connected to rotational loads, such as motors. In such a situation, unless all phases are tripped, the motor may act as a generator and contribute to the overcurrent condition.
The circuit breaker includes a cradle having latch and reset surfaces for latching and resetting the operating mechanism. Due to the wear on the latch and reset surfaces, these surfaces are often heat-treated. However, due to the complicated shape of the cradle having bends in many different directions, heat-treating can cause the cradle to become brittle and distort.
The molded case circuit breaker also includes a molded base and a coextensive cover. A centrally located aperture is provided in the cover for receiving an operating handle to allow the circuit breaker to be operated manually. The handle is comprised of an arcuate shaped base portion with a radially extending handle portion. The arcuate shaped base portion is coupled to the operating mechanism. Due to space limitations within the circuit breaker, the arcuate shaped base portion is insufficient to close the centrally located aperture provided in the cover for all handle positions. Thus, in order to prevent arc products from escaping through the circuit breaker cover, a handle barrier is disposed on the inside surface of the cover. The handle barrier acts as a sliding closure device to close the space between the centrally located aperture in the cover and the arcuate shaped base portion of the handle for all positions of the handle. The handle barrier slides freely within the cover.
In known circuit breakers, the handle barrier is freely disposed on top of the arcuate shaped base portion of the handle. However, with such an arrangement, it is possible that a gap can be formed between the arcuate shaped base portion of the handle and the handle barrier, thus potentially allowing arc products to escape through the cover. Moreover, once the cover is removed from the circuit breaker, the handle barrier, since it is not attached to the cover, will remain on the arcuate shaped base portion of the handle, and thus will have to be realigned before the cover is refastened to the base. This can be quite cumbersome.
It is an object of the present invention to provide a cradle with heat-treated latch and reset surfaces which overcomes the problems associated with the prior art.
It is a further object of the present invention to provide a cradle with heat-treated latch and reset surfaces that is not brittle or distorted.
It is another object of the present invention to provide means for carrying a handle barrier for a molded case circuit breaker which overcomes the problems associated with the prior art.
It is a further object of the present invention to provide a handle barrier which prevents the escape of arc products through the cover.
It is yet a further object of the present invention to provide stops for a handle barrier to prevent misalignment with the operating handle.
It is yet another object of the present invention to provide a means for holding a handle barrier with respect to the cover.
Briefly, the present invention relates to a two piece cradle assembly having a cradle portion and a heat-treated portion. The heat-treated portion forms the latch and reset surfaces. The cradle portion is integrally formed from a pair of spaced apart cradle-shaped arms joined together by a connecting portion. The heat treated portion is securely fastened to the connecting portion to form the two piece cradle assembly. A hold down slidably carries the handle barrier with respect to the cover, thus closing the centrally located aperture in the cover for all handle positions. The present invention is thus able to prevent arc products resulting from a separation of the main contacts from escaping through the centrally located aperture in the cover. Stops may be provided in one or both directions to prevent misalignment of the handle barrier with respect to the operating handle. In an alternate embodiment of the invention, a cover interlock is provided to prevent the cover from being removed when the circuit breaker is in an "on" position. The cover interlock can either be molded separately or integrally molded with the handle barrier hold down.
US Referenced Citations (9)
Continuation in Parts (1)
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Number |
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256878 |
Oct 1988 |
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Patent Grant
4973927
