Abstract:
A molded insulator cover for a circuit breaker molded case includes a terminal connector attachable to the strap terminal. The terminal connector is disposed in the circuit breaker molded case and an insulator discrete from the molded case is disposed around the terminal connector. The insulator is trapped into the circuit breaker molded case by attachment of the terminal connector to the strap terminal. The insulator is configured to be used with a plurality of different field installable terminal connectors.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to molded case circuit breakers and particularly to lug terminals or other terminal connectors used thereon. Still more particularly, this invention relates to insulators covering the lugs or terminal connectors, trapped to the circuit breaker by attachment of the lug or terminal to the circuit breaker terminal. 
   Circuit breakers are commonly mounted within an electrical enclosure or draw out unit to provide overcurrent protection to a circuit. A line side of the circuit breaker is connected to an electrical power line supplying electricity and a load side of the circuit breaker is connected to the circuit to be protected. In all circuit breakers, the separation of the breaker contacts due to a short circuit causes an electrical arc to form between the separating contacts. The arc causes the formation of relatively high-pressure gases as well as ionization of air molecules within the circuit breaker including carbon deposits. These high-pressure gases can cause damage to the breaker casing and the carbon deposits on the lugs and lug screws can lead to dielectric breakdown. The gases, therefore, must be vented from the circuit breaker enclosure. In addition, a phase-to-phase fault can occur if the arc gases from different phases are allowed to mix, and a phase-to-ground fault can occur if the gases contact the grounded enclosure. To avoid a phase-to-phase or phase-to-ground fault, gases vented from different phases must be kept separate from each other and away from the grounded enclosure until the ionization has dissipated. These high temperature gases must exit the circuit breaker enclosure in order to prevent the circuit breaker enclosure from becoming over-stressed. Ventilated circuit breakers provide openings within the circuit breaker enclosure to allow the ionized gases to exit the circuit breaker in a controlled manner. 
   During installation of a circuit breaker, terminal straps extending from either a line side or a load side of a circuit breaker must be connected to its source or load (such as to bus lines or cable lines). Connection may be accomplished by inserting a screw, or other rod-shaped connector, through a hole in the terminal strap and through an opening in a connector for the source or load. A nut, or equivalent receiving or tightening device, may then be attached to the screw for securing the connection between the terminal strap and the source or load. 
   It is known to provide a wiring connector or lug on the load terminal of a molded case circuit breaker. These wiring lugs have at least one wire-receiving opening in an end face. The opening is individually intersected by a threaded opening which intersects the wire-receiving opening at a right angle. A set screw in the threaded opening projects into the wire-receiving opening to clamp a wire in a respective opening. This lug permits power through the circuit breaker to be distributed to a load device downstream or received from a source upstream of the circuit breaker. 
   It is further known to provide a molded insulating terminal cover which attaches to and becomes an extension of the circuit breaker molded case to provide an insulating covering for the lug terminals. Molded insulating lug covers require the circuit breaker molded case to be suitably configured with cooperative attachment features to receive the molded such attachment features molded into the members of the molded case and cannot readily receive a retrofit lug terminal or other terminal connector, such as for a bus bar connection. 
   A differently configured molded insulating terminal cover is utilized in a bus bar terminal connection which attaches to and becomes an extension of the circuit breaker molded case to provide an insulating covering for bus bar terminal connections. These molded insulating lug covers also require the circuit breaker molded case to be suitably configured with cooperative attachment features to receive the molded such attachment features molded into the members of the molded case and cannot readily receive a retrofit lug terminal or other terminal connector. 
   It would be economically advantageous, to provide bus covers and lug covers for molded case industrial-rated circuit breakers which require no additional fastening means for holding the lug and bus covers to the circuit breaker enclosure while providing improved isolation of the lugs or terminals and corresponding terminal screws. Accordingly, one purpose of the invention is to describe both lug and bus covers for industrial-rated circuit breakers which are economically feasible for both factory as well as field-installation. 
   BRIEF DESCRIPTION OF INVENTION 
   The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a circuit breaker molded case including a strap terminal extending therefrom and a terminal connector attached to the strap terminal disposed in the circuit breaker molded case. An insulator cover discrete from the molded case is disposed around the terminal connector and is trapped into the circuit breaker molded case by attachment thereof to the strap terminal. The insulator cover is configured to be used with a plurality of different field installable terminal connectors while providing electrical isolation of the terminal connector. 
   In an exemplary embodiment of the present invention, the insulator cover includes a substantially C-shaped member having a bottom wall disposed under the terminal connector and defined by a back wall for disposal against the molded case, and sidewalls connected with the bottom wall and back wall extending along opposite sides of the terminal connector. A snap-fit feature extends from each side wall and the bottom wall and each are configured for snap-fit engagement with the molded case having a complementary snap-fit feature for snap-fit engagement therebetween. The insulator cover preferably includes a discrete a gasket disposed over each respective strap terminal and intermediate the molded case and insulator cover. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
       FIG. 1  is a top perspective view of a three phase molded case circuit breaker and three different connection terminals for connection therewith illustrating two lug covers and corresponding gaskets installed and an exemplary embodiment of a lug, a lug cover, and gasket removed therefrom; 
       FIG. 2  is an exploded perspective view of a molded case circuit breaker; 
       FIG. 3  is an enlarged perspective view of the lug cover of  FIG. 1 ; 
       FIG. 4  is an enlarged perspective view of the gasket of  FIG. 1 ; and 
       FIG. 5  is a top perspective view of the three phase molded case circuit breaker of  FIG. 1  illustrating use of saddle clamps for use with the lug covers of FIG.  1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a top perspective view of a molded case circuit breaker  10  is generally shown. Molded case circuit breaker  10  is generally interconnected within a protected circuit between multiple phases of a power source (not shown) at line end  14  and a load to be protected (not shown) at load end  12 . Molded case circuit breaker  10  includes a base  18 , a mid cover  20  and a top cover  22  having a toggle handle  44  (operating handle) extending through an opening  24 . Toggle handle  44  is interconnected with a circuit breaker operating mechanism (not shown) and allows for external operation of individual cassettes disposed therebeneath. The circuit breaker in  FIG. 1  shows a typical three phase configuration, however, the present invention is not limited to this configuration but may be applied to other configurations, such as the typical one, two or four phase circuit breakers. 
   Referring now to  FIG. 2 , an exploded view of molded case circuit breaker  10  is provided. A series of circuit breaker cassettes  32 ,  34 ,  36  are generally well known and may be, for example, of the rotary type. Examples of rotary contact structures that may be operated by operating mechanism  38  are described in more detail in U.S. Pat. Nos. 6,114,641 and 6,396,369, both entitled “Rotary Contact Assembly For High-Ampere Rated Circuit Breakers”, and U.S. Pat. No. 6,175,288, entitled “Supplemental Trip Unit For Rotary Circuit Interrupters”. 
   Circuit breaker cassettes  32 ,  34 ,  36  are seated approximately upstanding within base  18 , and the cassette  34  includes operating mechanism  38  positioned thereon. The individual phases of current are divided into three phases, wherein each phase passes through one of the circuit breaker cassettes  32 ,  34 ,  36 . Each of cassettes  32 ,  34 ,  36  includes one or more contact pairs therein for passage of current when the contacts are closed and for preventing passage of current when the contact pairs are 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  10 . 
   Still referring to  FIG. 2 , each cassette  32 ,  34 ,  36  is commonly operated by a first cross bar (cross pin)  40  that interfaces with the internal mechanisms of cassettes  32 ,  34 ,  36  such that when one of cassettes  32 ,  34 ,  36  are opened or closed, the other cassettes  32 ,  34 ,  36  will operate cooperatively. It will be recognized by one skilled in the pertinent art that only one cross bar may be used to interface with the internal mechanisms of cassettes  32 ,  34 ,  36  such that when one of cassettes  32 ,  34 ,  36  are opened or closed, the other cassettes  32 ,  34 ,  36  will operate cooperatively. Positioning rods  33  and protrusions  35  in cassettes  32 ,  36  are also employed to position the cassettes  32 ,  34 ,  36  adjacent to each other. Positioning rods  31  are also used to position mechanism  38  to locate cross bar  40  to align with rotary contact assembly  56  within cassettes  32 ,  34 ,  36 . Operating mechanism  38  is positioned and configured atop cassette  34 , which is generally disposed intermediate to cassettes  32  and  36 . Operating mechanism  38  operates substantially as described herein and as described in U.S. Pat. No. 6,218,919, entitled “Circuit Breaker Latch Mechanism with Decreased Trip Time”. It should also be noted that employment of other operating mechanisms is contemplated, as well. The cassettes  32 ,  34 ,  36  are typically formed of high strength plastic material and each include opposing sidewalls. 
   To allow connection with the external electrical circuits to be protected, load lugs  54  are connected with a corresponding load strap  57  extending from the circuit breaker  10  with reference to  FIGS. 1 and 2 . A similar pair of line lug compartments are provided on the opposite side of the circuit breaker case  10  to contain the line lugs  54  identical to load lugs  54 . Line lugs  54  are connected with a corresponding line strap  58  extending from the circuit breaker  10  with reference to FIG.  1 . External electrical connection is made with the lugs  54  by means of terminal screws  61  attached to the top surface thereof. 
   To facilitate field-installation of the lugs  54 , a pair of rails  60  are formed integrally with the circuit breaker case  10  on the interior opposing surfaces of each load lug compartment  62 . As shown in  FIGS. 1 ,  3 , and  5  a corresponding pair of snap-fit features  64  are formed on opposite sides of a lug cover  66  configured to be in snap fit engagement with a corresponding rail  60  and a groove  63  defined by each rail  60 . Lug cover  66  in turn is received in a corresponding lug compartment  62  and retained therein using snap-fit features  64  in a corresponding rail  60 . Each snap-fit feature  64  extends from a corresponding flange  68  that is configured to rest on a respective rail  60 . Snap-fit features  64  and flanges  68  are integrally formed on the opposing sides of a bottom wall  69  defining cover  66 . By capturing the snap-fit features  64  within the grooves  61  and the flange  68  resting on the rail, the lugs  54  are restrained from moving in the vertical and horizontal directions as viewed in FIG.  1 . 
   Referring now to  FIGS. 1 ,  2  and  4 , a gasket  70  is configured with a slot  72  sized to receive a strap  57 ,  58  therethrough while the perimeter defining gasket  70  substantially corresponds to the dimensions of a wall  74  of cover  66  and a wall  77  of each lug compartment  62  having a strap  57 ,  58  extending therethrough. Gasket  70  is positioned against a corresponding wall  77  over a strap  57 ,  58  extending therethrough to provide insulation between circuit breaker base  18  and cover  66 . The gasket  70  is preferably fabricated from a temperature resistive insulative material, such as a resilient elastomer like sheet silicone rubber. In an exemplary embodiment the silicon rubber may include a one sided acrylic adhesive thereon. Each cover  66  includes a strap slot  76  configured in wall  74  to receive a strap  57 ,  58  therethrough. Strap slot  76  is aligned with a corresponding strap aperture  78  configured in lug  54  when lug  54  is received in cover  66  to receive a strap  57 ,  58  therethrough. Cover  66  is positioned in a corresponding lug compartment  62  over a strap  57 ,  58  and retained therein by means of a press-fit connection with snap-fit features  64  and rails  60 . The lug cover  66  can be fabricated from an insulative material, such as a resilient plastic. When a plastic lug cover  66  is employed, the lug cover not only provides added electrical insulation to the lugs but also serves to restrain the lugs from moving in the horizontal and vertical directions, as viewed in FIG.  1 . When the lugs are positioned within a corresponding cover  66 , the lugs  54  become entrapped under the confines provided by wall  74  and opposing L-shaped walls  80  extending from opposing ends of wall  74  such that the lugs cannot be readily removed from a cavity  82  defined by walls  69 ,  74 , and  80 . 
   As best seen in  FIG. 3 , bottom wall  69  is further defined with a cavity  84  configured therein to retain a threaded nut  86 . Threaded nut  86  is configured to be rotationally restrained in cavity  84  while threadably receiving terminal screw  61  (see FIG.  5 ). Bottom wall  69  and cavity  84  are further defined by a cylinder  89  extending therefrom. Cylinder  89  is integrally formed with cover  66  and is configured to insulate terminal screw  61  extending through nut  86  and external cover  66 . The cavity  84  provided within the bottom wall  69  preferably holds nut  86  between the perimeters defining each. 
   The circuit breaker  10  is shown in  FIG. 1  with two lugs  54  attached to their respective line straps  58  and within their respective line lug compartments  62 . The terminal screws  61  are readily accessible from the top of the breaker via apertures  88  to facilitate electrical connection between the lugs  54  and the external circuit.  FIG. 1  illustrates three different terminal connections that may be made in the field using cover  66  and gasket  70  (of  FIGS. 3 and 4 ) while  FIG. 5  illustrates a fourth discussed further herein. First, with respect to  FIG. 1 , lug  54  is configured to receive a wire conductor  90  through an opening  92  for connection with strap  58 . The terminal screw  61  is tightened to pinch wire  90  against strap  58  extending through strap aperture  78  configured in lug  54 . Second, cover  66  may be employed to couple a bus bar  94  to strap  58  by aligning apertures  96  configured in strap  58  and bus bar  94  for receiving terminal screw  61  therethrough for threadably tightening with nut  86  disposed within cavity  84  of cover  66 . Similarly, in a third terminal connection, a ring terminal  98  coupled to a wire conductor  100  (e.g., crimped) may be coupled to strap  58  by aligning apertures  96  configured in strap  58  and ring terminal  98  for receiving terminal screw  61  therethrough for threadably tightening with nut  86  disposed within cavity  84  of cover  66 . It will be recognized by one skilled in the art that a U-shaped terminal may be utilized instead of a ring terminal and employed in the same manner described above. Although not shown in  FIG. 1 , the lugs or other terminal connections are attached to the load straps  56  in a similar manner and shown with respect to  FIG. 5 , for example. 
   Referring now to  FIG. 5 , a fourth terminal connection that may be employed in the field using cover  66  and gasket  70  (of  FIGS. 3 and 4 ) is illustrated. A U-shaped clamp or saddle clamp  102 , well known in the art, may be employed instead of lug  54  with cover  66  and gasket  70  for electrically connecting wire conductor  90  of  FIG. 1  with a strap  57 . In this manner, the saddle clamp is disposed in cavity  82  of cover  66  over nut  86  and for electrically connecting smaller wire conductors  90  to strap  57  by threadably tightening terminal screw  61  extending through saddle clamp  102  into nut  86 . Examples of such saddle clamp structures that may be employed with cover  66  and gasket  70  are described in more detail in U.S. Pat. No. 3,824,555, entitled “Electrical Conductor Terminal Assembly”, which is incorporated herein by reference in its entirety. 
   The above described cover and gasket assembly facilitates field-installation of the lugs to the circuit breaker case, as well as allowing different terminal connections using the same cover configuration. The cover and gasket also protect the lugs and lug or terminal screws from carbon deposits and pole to pole dielectric breakdown by offering better isolation for the lugs or terminal connectors. 
   While the invention has been described with reference to an exemplary 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 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.