Molded case circuit breaker and molded pole assembly

Abstract: A molded case circuit breaker base (11) is configured to receive pole modules (25) that include the circuit breaker components (19) for multipole operation. The base (11) is configured to receive the bottom edges of the module enclosures (25) in press-fit relation. A complementary molded case circuit breaker cover (12) attaches to the top of the modules (25) to complete the multipole circuit breaker enclosure.

Description: The advent of US circuit breaker manufacturers into the world market requires a larger number of poles when such circuit breakers are used in industrial applications. Typical US electrical distribution systems provide 3 pole service compared to 4 pole service in some European and Asian countries where there is a need to switch the neutral conductor. Since the additional poles often require expensive molding operations to provide increased space, the provision of 4 or more pole industrial rated circuit breakers over a wide range of circuit breaker ampere ratings could increase the cost of such breakers to manufacture and sell. An early approach to providing increased circuit breaker poles to existing 3 pole circuit breakers is found in US patent 4,644,308 entitled "Variable Composition Switching Device Realizable by the Assembly of Modular Elements". Another way to provide increased circuit breaker poles to existing 3 pole circuit breaker designs is found in US patent 5,298,894 entitled "Range of Molded Case Low 20 Voltage Circuit Breakers". A further approach is described within US patent 5,479,143 entitled "Multipole Circuit Breaker with Modular Assembly" wherein the individual circuit breaker pole components are in a modular configuration. A state-of-the-art circuit breaker employing modular pole units for low voltage circuit breakers is found in US patent 5,607,047 entitled "Circuit Breaker Housing". It would be economically advantageous to have a single circuit breaker modular design for high ampere-rated circuit breakers without requiring separated molded plastic enclosures for each multipole circuit breakers over a wide range of ampere ratings. The modular approach makes the best use of a base unit supporting individual modules for low equipment cost to produce providing a diversity of products in 3, 4 or more pole combinations with a few number of unique components. One purpose of the invention is to provided a wide range of multipole circuit breakers over a wide range of ampere ratings based on a common platform that accepts any number of modular pole units to accommodate up to 4 or more pole circuit breaker applications. According to the invention, there is provided a multipole circuit breaker comprising:a base member of electrically insulative plastic material having a plurality of grooves formed on a top surface thereof, a cover member of electrically insulative plastic material having an aperture therethrough for passage of a circuit breaker operating handle for manual control of the ON/OFF condition of circuit breaker fixed and movable contracts; and a plurality of U-shaped cases of insulative plastic material intermediate said cover and said base, said cases containing a movable contact arm with one of said movable contacts arranged at one end thereof for moving in and out of contact with one of said fixed contacts arranged on said base. In one embodiment of the invention, a molded case circuit breaker base is configured to receive a plurality of pole modules that include the circuit breaker components for multipole operation. The top surface of the base includes rails configured to receive tracks formed on the bottom edges of the module enclosures in press-fit relation. A complimentary molded case circuit breaker cover attaches to the top of the modules to complete the multipole circuit breaker enclosure. Document EP 0 788 128 discloses a device according to the preamble of claim 1. The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:- Figure 1 is a top perspective view of an industrial-rated 3-pole circuit breaker according to the Prior Art; Figure 2 is a top perspective view of an industrial-rated multipole circuit breaker according to the invention, with the pole components depicted in isometric projection with the circuit breaker base; and Figure 3 is a top perspective view of the industrial-rated multipole circuit breaker of Figure 2 in complete assembly. A three pole industrial-rated molded case circuit breaker 10 is shown in Figure 1 to consist of a plastic base 11 to which a plastic cover 12 is attached. The cover includes a handle aperture 13 through which an operating handle 14 extends. The operating handle interacts with the circuit breaker operating mechanism that controls the ON/OFF status of the circuit breaker contacts (not shown) in the manner described within US patent 5,361,052 entitled "Industrial-Rated Circuit Breaker Having Universal Application". The circuit breaker includes three separate poles connecting with an exterior electric distribution circuit having three phase A-C means of the load straps 9A-9C. Corresponding line straps (not shown) that connect with associated electrical equipment are located at the opposite end of the circuit breaker case. When more than 3 poles are required, it is common to mold larger circuit breakers having 4 or more poles integrally-formed therein. It has been determined that multipole circuit breakers can be assembled in the modular arrangement depicted in Figure 2. In this arrangement, the base 11 and cover 12 for the multipole circuit breaker 10 are configured to fit any number of modular units defined within the U-shaped cases 25. The cases 25 include a top wall 26 and a pair of opposing sidewalls 27, 28 with a front opening 35 at one end for receiving the load straps (not shown) connecting with load strap recess 32 and a rear opening 36 at the opposite end for receiving the line straps (not shown) connecting with the line strap recess 31. The rear opening also receives the arc chute 17 that includes a plurality of arc plates 18. The arc chute is described in greater detail within US patent 4,970,482 entitled "Current Limiting Circuit Breaker Compact Arc Chute Configuration". Each case 25 includes a movable contact assembly 19 with a moveable contact arm 20 that includes the movable contact 21 at one and is connected with a rotor 24 at the opposite end thereof. The movable contact arm connects with the fixed contact (not shown) by attachment to the end 23 of a braid conductor 22. Similar to the manner described in US patent 5,319,166 entitled "Molded Case Circuit Breaker Modular Contact Arm Arrangement", the operating handle 14 extends through the aperture 13 in the cover 12 and engages the operating mechanism 15 disposed within one of the U-shaped cases 25. The operating handle 14 engages the operating mechanism 15 through an opening 29 of the case 25. A crossbar 16 passes through the opposing sidewalls 27, 28 of the cases 25 to interconnect the operating mechanism 15 with each of the movable contact arm assemblies 19 to insure that the movable contact arms 20 operate in unison when the operating mechanism is articulated. Attachment between the individual cases 25 and the base 11 is made by means of the press-fit relation between the rails formed on the bottom of the sidewalls 27, 28 and the inner and outer tracks or slots 33, 34 formed within the top surface of the base 11. To provide the press-fit relation, the thickness t 1 of the individual sidewalls 27, is configured relative to the width w 1 of the outer slots 34 and the thickness t 2 of pairs of sidewalls 27, 28 is configured relative to the width W2 of the inner slots 33, accordingly. The cover 12 is attached to the cases 25 and the base 11 by means of the apertures 8, 37 and 38 formed in the cover, cases and base respectfully. The assembled 4 pole circuit breaker 10 is shown in Figure 3 with the cover 12 attached to the top of the individual pole units contained within individual cases 25A-D, which are attached to the base 11, at the bottom thereof. The individual load straps 9A-9D are arranged for connection with the individual A-C phases of the associated electrical distribution circuit. The operating handle 14 is arranged for manually turning all the phases ON and OFF simultaneously. Although 4 individual poles are shown in Figures 2 and 3, as many poles as required can be used within the teachings of the invention by configuring the cover and base to accept the required individual phases.

Claims: A multipole circuit breaker comprising: a base member (11) of electrically insulative plastic material having a plurality of grooves (33, 34) formed on a top surface thereof, a cover member (12) of electrically insulative plastic material having an aperture (13) therethrough for passage of a circuit breaker operating handle (14) for manual control of the ON/OFF condition of circuit breaker fixed and movable contracts; characterised by a plurality of U-shaped cases (25) of insulative plastic material intermediate said cover and said base, said cases containing a movable contact arm with one of said movable contacts arranged at one end thereof for moving in and out of contact with one of said fixed contacts arranged on said base. The multipole circuit breaker of claim 1 wherein each of said cases comprises a top wall and a pair of sidewalls depending from said top wall, said sidewalls defining a wall thickness less than a width defined by said grooves, whereby an end of said sidewalls is received within one of said grooves. The multipole circuit breaker of claim 1 or 2 wherein each of said cases further include an arc chute proximate each of said movable contacts. The multipole circuit breaker of claim 2 wherein said end of said sidewalls is received within said groove in press-fit relation. The multipole circuit breaker of any preceding claim wherein said base member defines a load strap recess formed therein at one end and a line strap recess formed on a opposite end thereof. The multipole circuit breaker of any preceding claim further including an operating mechanism connecting between said movable contact arms within said cases for causing said movable contact arms to rotate in unison. The multipole circuit breaker of any preceding claim wherein said plurality of cases comprises three cases. The multipole circuit breaker of any one of claims 1 to 6 wherein said plurality of cases comprises four cases. The multipole circuit breaker of any preceding claim wherein said cover, base and cases each include openings for passage of a fastener for holding said cover, base, and cases.

Inventors: CALDER WILLIAM HOWARD, PAPALLO THOMAS FREDERICK JR, CALDER, WILLIAM HOWARD, PAPALLO, THOMAS FREDERICK, JR.
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1999
Main classification: H01H71
IPC codes: H01H71