Abstract:
A circuit breaker rotary contact arm is used within a plurality of single pole modules ganged together to form a single multi-pole circuit breaker. To provide for use in quiescent conditions having high ampere ratings, low ampere rated rotary contact arm assemblies are combined in parallel to form a higher rated single pole module, which are then ganged together to form a single multi-pole circuit breaker having a high quiescent ampere rating.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates in general to an electrical circuit breaker provided with a modular contact system. More particularly, the present invention relates to a modular contact system made up of a multiplicity of single pole breaking modules having many different sizes, through simple parallel connection of individual single pole modules. 
     2. Description of Related Art 
     Multi-pole circuit breakers comprising a modular array of single-pole circuit breakers connected together by means of fasteners are well known in residential applications. U.S. Pat. No. 5,172,087 entitled “Handle Connector for Multi-Pole Circuit Breaker” describes such a multi-pole circuit breaker that incorporates an improved operating handle to integrate the separate single pole-handles into one effective operating handle. The overall width of the multi-pole circuit breaker is the sum of the individual single pole circuit breaker widths. 
     U.S. Pat. No. 6,326,868 entitled “Rotary Contact Assembly for High Ampere-Rated Circuit Breakers,” herein incorporated by reference, describes single pole rotary contact arm assemblies ganged together to form a multi-pole circuit breaker. Interconnection of the contact arm assemblies with the operating mechanism is achieved by means of an elongated pin, thereby enabling a single mechanism to operate all single pole rotary contact arm assemblies. The rotary arrangement of the contact arms produces two arcs in series during a short circuit interruption, which rapidly and effectively extinguishes the short circuit current to disconnect the protected circuit. 
     For circuit breaker applications requiring high quiescent ampere ratings, the use of a larger circuit breaker with proportionately larger single pole components is well known and is described in U.S. Pat. No. 5,424,701 entitled “Operating Mechanism for High Ampere-Rated Circuit Breakers.” Another method of serving high quiescent ampere rated applications without increasing the size of the single pole components is by adjoining two standard sized circuit breakers and connecting adjacent poles in parallel. Such a twinned arrangement is described in U.S. Pat. No. 4,884,047 entitled “High Rating Multi-pole Circuit Breaker Formed by Two Adjoined Molded Cases.” The overall width of the twinned multi-pole circuit breaker is the sum of the individual multi-pole circuit breaker widths. 
     SUMMARY OF THE INVENTION 
     Multiple rotary contact arm assemblies having a low quiescent ampere rating are connected in parallel to form a single pole circuit breaker module having a high quiescent ampere rating, higher than the rating of its individual components. Ganging together these single pole circuit breaker modules, which comprise standard parts and modular assemblies, forms an economical and compact multi-pole circuit breaker having a high quiescent ampere rating. 
     The invention offers advantages of both a rotary contact arm assembly and a modular construction. The rotary contact arm configuration, which produces two arcs in series, provides an effective means for rapidly suppressing and extinguishing short circuit currents, and the single pole module, with parallel connected low ampere rated contact arms, provides an economical and compact means of achieving a high ampere rating. 
     According to the invention, a circuit breaker, comprising a circuit breaker housing and a first and second current path housing arranged within the circuit breaker housing. A first current path is arranged within the first current path housing and is connected to the protected circuit. A second current path is arranged within the second current path housing and is electrically connected in parallel to the first current path and is also connected to the protected circuit. An operating mechanism is arranged within the circuit breaker housing for disconnecting the protected circuit upon occurrence of an overcurrent condition in the protected circuit. A trip unit is arranged within the circuit breaker housing for articulating the operating mechanism upon occurrence of the overcurrent condition. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a high ampere rated multi-pole circuit breaker in accordance with the invention. 
     FIG. 2 is a perspective side view of a low ampere rated rotary contact arm single pole module with the cover removed to depict the circuit breaker components in the “On” condition. 
     FIG. 3 is a perspective side view of a high ampere rated rotary contact arm single pole module with the cover removed to depict the circuit breaker components in the “On” condition, in accordance with the invention. 
     FIG. 4 is a top view of a low ampere rated single pole module showing only one rotary contact arm assembly. 
     FIG. 5 is a top view of a high ampere rated single pole module showing two rotary contact arm assemblies arranged for parallel connection in accordance with the invention. 
     FIG. 6 is a top view of a low ampere rated single pole module similar to that of FIG. 4 except comprising two contact arms in parallel. 
     FIG. 7 is a top view of a high ampere rated single pole module similar to that of FIG. 5 except comprising two sets of two rotary contact arm assemblies arranged for parallel connection in accordance with the invention. 
     FIG. 8 is a top view of a high ampere rated single pole module similar to that of FIG. 5 except comprising two sets of three rotary contact arm assemblies arranged for parallel connection in accordance with the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     FIG. 1 depicts a multi-pole molded case circuit breaker  10  with operating handle  12  that interfaces with mechanism  14  contained within circuit breaker housing  16 . The mechanism  14 , actuated by trip unit  18  during an overcurrent condition, articulates contact arms  20  (shown in FIG. 3) within the single pole modules  22   a ,  22   b . The single pole modules  22   a ,  22   b  comprise outer current path housing  24   a ,  24   b  and inner current path housing  24   c  which house first and second current paths as best seen in FIG.  3  and FIG.  5 . 
     FIG. 2 depicts a single pole module  22   a ′ An outer current path housing  24   a  supports operating mechanism  14  to articulate the contact arm  20  between an open and closed position for isolation of a protected circuit. Movable contacts  26 ,  28  on contact arm  20  abut stationary contacts  30 ,  32  on line strap  34  and load strap  36 . Under quiescent operating conditions, the electrical current passes through the line strap  34 , stationary contact  30 , movable contact  26 , contact arm  20 , movable contact  28 , stationary contact  32 , and load strap  18 . The line strap  34  provides an electrical connection between the external power source and the circuit breaker internal components. A load terminal (not shown) provides means to electrically connect the protected circuit to the load strap  36 . 
     The contact arm  20  is articulated during a short circuit overcurrent condition. This action produces an electrical arc (not shown) that is directed towards arc chutes  38 ,  40 , with eventual extinguishing through exhaust ports  42 ,  44 . The contact arm  20  and contact springs (not shown) are captivated by rotor assembly  46 . 
     A higher rated single pole module  22   a  is shown in FIG. 3, wherein like reference numerals with respect to FIG.  1  and FIG. 2 designate corresponding parts. Two sets of internal components of the single pole molded case circuit breaker shown in FIG.  2 . Each of the sets comprising, a line strap  34 , a stationary contact  30 , a movable contact  26 , a rotary contact arm  20 , a movable contact  28 , a stationary contact  32 , a load strap  36 , arc chutes  38 ,  40 , and rotor assembly  46 . These sets are arranged adjacent each other and captivated by outer current path housing  24   a , ( 24   b  removed for clarity) and inner current path housing  24   c . This arrangement is best seen by now referring to FIGS. 4 and 5. 
     FIG. 4 depicts a single pole module  22   a ′, showing a single rotor assembly  46  captivated by outer current path housings  24   a ,  24   b  which is capable of carrying low quiescent electrical currents. 
     FIG. 5 depicts a higher rated single pole module  22   a , showing two rotor assemblies  46  captivated by outer current path housings  24   a ,  24   b  and inner current path housing  24   c  which is capable of carrying higher quiescent electrical currents than that of FIG.  4 . Outer current path housings  24   a ,  24   b  and inner current path housing  24   c  are restrained by fasteners (not shown). The parallel electrical connection to the aforementioned adjacent internal components are made at the external connection points  48 ,  50  of line strap  34  and load strap  36 . The combined width of inner and outer current path housings ( 24   a + 24   b + 24   c ) is arranged to be less than (2) times ( 24   a + 24   b ), thereby resulting in dimension “B” being less than (2) times dimension “A”. 
     FIG. 7 depicts an alternate embodiment of single-pole module  22   a  according to the invention, comprising three current path housings  24   a ,  24   b ,  24   c  contained within two double rotor assemblies  46 , each provided with two rotary contact arms  20 , connected in parallel to allow a quiescent current higher than that allowed by the prior art single pole module  22   a ′ shown in FIG.  6 . 
     FIG. 8 is a further alternate embodiment of a single pole module  22   a  according to the invention, comprising three current path housings  24   a ,  24   b ,  24   c  contained within two triple assemblies  46 , each provided with three rotary contact arms  20 , connected in parallel to allow a quiescent current higher than that allowed by the single pole module  22   a ′ shown in FIG.  6 . 
     In the single pole module  22   a  shown in FIG.  7  and FIG. 8, the combined width of internal and external current path housings ( 24   a + 24   b + 24   c ) results in dimension “B” being less than two times dimension “A”. 
     What has been described herein depicts just some of the embodiments of the invention, and is not to be considered as limiting its scope and all similar and equivalent approaches. For example, the number of line straps  34  and load straps  36  connected in parallel to the external connection points  48 ,  50  can more than two, if higher quiescent currents are desired, yet maintaining dimension “B” of the module less than that of the sum of dimensions “A” of an equivalent number of prior art modules connected in parallel. Therefore, in the case of three modules, B&lt;3A.