Patent Publication Number: US-7210970-B1

Title: Circuit breaker with improved connector socket

Description:
FIELD OF THE INVENTION 
     This invention relates generally to electrical circuit breakers and particularly to miniature circuit breakers having arc fault features and various auxiliary circuit functions. 
     BACKGROUND OF THE INVENTION 
     Subminiature thermal circuit breakers are widely used in applications in which spatial limitations are of particular importance, such as in aircraft. Such devices employ, for example, a thermostatic current carrying member that upon a selected overload condition causes a latching mechanism to unlatch and open a circuit path connected to the breaker by the movement of at least one movable electrical contact from a mating stationary electrical contact. 
     In recent years there has been a trend to add other functions to such circuit breakers, for example, providing various auxiliary circuits including arc fault protection. Among the challenges that must be dealt with in providing such enhancements is a space limitation for such circuit breakers. For many applications the space available for an individual circuit breaker cannot be significantly increased, even though new functions are added, due to the existing layout of the control panel in which such circuit breakers are mounted. 
     Typically, subminiature circuit breakers presently in use have first and second line terminals mounted in the circuit breaker housing that extend through respective openings in a selected wall, such as a bottom wall, for secure attachment to a circuit path, as by threaded interconnection therewith as shown, for example, in U.S. Pat. No. 3,361,882, assigned to the assignee of the present invention, the subject matter of which is incorporated herein by this reference. When auxiliary circuits are provided, it is known to provide a socket having a metal member for electrical connection and another metal member formed with spring fingers for engaging a shouldered connector pin, such as military specification connector (M39029), to retain the connector pin in a socket. Such use involves a compromise between using a spring member having desired low force to reduce stress for optimum long life and the need for making the fingers relatively rigid to resist buckling of the fingers when extraction of the connector pin is attempted with the result that retentive capability of the socket is sacrificed. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a socket for a circuit breaker housing or the like for receiving a shouldered connector pin with optimum retentive capability yet with minimal or no spatial interference in the circuit breaker receiving cavity of the circuit breaker housing; 
     Another object of the invention is the provision of a socket for receiving a shouldered connector pin, such as a military specification connector pin M39029/1-101, with enhanced retentive capability as well as enhanced reliability of electrical connectivity; 
     Another object of the present invention is the provision of a socket for receiving a shouldered pin that is of lower cost and easier to assemble than prior art sockets. 
     Yet another object of the invention is to overcome the limitations of the prior art mentioned above. 
     Briefly, in accordance with a preferred embodiment of the invention, a selected wall of the circuit breaker housing is formed with an open, connector pin receiving channel in a face surface thereof. The channel extends, in accordance with the preferred embodiment, along a selected axis with first, second and third continuous axial lengths having respective first, second and third radii to form a generally semi-circular channel surface, as seen in a cross section taken perpendicular to the selected axis at each axial length. The pin receiving entrance is located at an outer end of the first axial length. The radius of the second axial length forms a stop surface or shoulder at the inner end of the first axial length and extends from a first depth of the channel surface of the first axial length to a second, greater depth of the channel surface of the second axial length. The radius of the third axial length is selected to be less than the first and second radii. 
     In accordance with preferred embodiments, an electrically conductive spring member is received over the channel with a set of two spring legs extending from the spring member toward the first axial length portion of the channel. Preferably, a second set of two spring legs also extends from the spring member toward the third axial length portion of the channel and can serve as redundant electrical contacts. Preferably, the spring member is attached to the selected wall of the circuit breaker housing and is provided with a circuit connection surface area. 
     A retainer plate of suitable material, such as the same material that the selected wall of the circuit breaker housing is composed of, is received over the spring member and fastened to the selected wall and provides support to the spring member. 
     Use of the shoulder formed between the first and second axial lengths of the pin receiving channel in the housing wall as a retaining member, abetted by the supportive retainer plate or housing wall, allows one to select the spring member on the basis of optimization of electrical connectivity with the connector pin due to the enhancement of the overall retention capability of the pin within the socket. 
     Other objects, features and advantages of the circuit housing and socket of the invention will appear from the following detailed description of preferred embodiments taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a subminiature circuit breaker having a supplemental pin receiving socket made in accordance with a preferred embodiment of the invention; 
         FIG. 2  is a perspective view of a housing half of the  FIG. 1  circuit breaker showing details of the socket; 
         FIG. 3  is a perspective view of the top side of the retainer plate also shown in  FIGS. 1 and 2  and  FIG. 3(   a ) is a perspective view of bottom side of the retainer plate; 
         FIG. 4  is a perspective view of a spring member used in the  FIGS. 1 and 2  structure; 
         FIG. 5  is a view similar to  FIG. 2  but shown without the  FIG. 3  retainer plate or  FIG. 4  spring member and  FIG. 5(   a ) is an enlarged partial front view of the channel shown in  FIG. 5  showing the semicircular channel surface of the several axial lengths; 
         FIG. 6  is an exploded perspective view showing the  FIG. 5  housing half, the  FIG. 4  spring member, the  FIG. 3  retainer plate and a typical shouldered connector pin  20  for receipt in the socket; 
         FIGS. 7(   a )– 7 ( d ) show typical circuit breaker features and auxiliary circuits that can be mounted in the housing and with which the socket of the invention can be advantageously used; 
         FIG. 8  is a perspective view, similar to  FIG. 1 , of a circuit breaker made in accordance with a second preferred embodiment; 
         FIG. 9  is a perspective view of one of the housing halves of the  FIG. 8  circuit breaker showing a connector pin receiving channel formed in the face surface of a wall of the housing half; 
         FIG. 10  is a perspective view, similar to  FIG. 9  but of a smaller scale and shown with the socket structure made in accordance with the second embodiment 
         FIG. 11  is an exploded perspective view of the  FIG. 10  structure; and 
         FIG. 12  is an exploded view of  FIG. 8  showing the circuit breaker  100  along with a two part housing shell that receives the circuit breaker and forms part of the housing thereof. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1 and 2 , a circuit breaker  10 , made in accordance with a preferred embodiment of the invention, is shown comprising a housing  12  having first and second interfitting housing portions  12   a ,  12   b , respectively. Housing portion  12   a  includes, with respect to the orientations shown in the drawings, a bottom wall  12   c , two opposed side walls  12   d , a pushbutton actuator receiving end wall  12   e  and opposed line terminals receiving end wall portions  12   f  forming part of the end wall, leaving an open cavity  12   g  for receipt of circuit breaker structure and accompanying circuitry, to be discussed. Cavity  12   g  is enclosed by housing portion  12   b  suitably fastened to side walls  12   d , end wall  12   e  and wall portions  12   f . First and second line terminals L 1 , L 2  are mounted within cavity  12   c  and extend through openings  12   h  for suitable electrical attachment to a selected circuit path to be monitored. 
     In a first preferred embodiment shown and described, a portion  12   k  of wall member  12   c , made of dielectric material extends beyond cavity  12   c  to a length generally coextensive with line terminals L 1 , L 2  and is used as a terminal barrier for preventing arcs and shorts external to the circuit breaker. With particular reference to  FIGS. 5 ,  5 ( a ), a pin receiving socket  14  is provided by forming an open pin receiving channel  14   a  in a face surface of wall portion  12   k . Channel  14   a  extends along a selected axis  14   b  generally parallel to the face surface of the wall and comprises respective first, second and third continuous axial lengths  14   c ,  14   d  and  14   e . Channel  14   a  has a channel surface that is generally semicircular with respect to a cross section taken perpendicular to axis  14   b  through each of the axial lengths with a first radius  14   f  for first axial length  14   c  selected to slidingly receive the shoulder of a selected shouldered pin, a second radius  14   g  for the second axial length  14   d , larger than radius  14   f  and a third radius  14   h  for third axial length  14   e  smaller than radii  14   f  and  14   g . The center of radius  14   f  is selected so that the shoulder  20   b  of a pin  20  (see  FIG. 6 ) can slide along radius  14   f  while being inserted and then snap into concentricity with radius  14   g  while pin portion  20   a  comes to rest against radius  14   f . Thus an accommodating shouldered connector pin can be slidingly inserted into the first axial length  14   c  of channel  14   a  from an outer end  14   k  along the first axial length until the flange of the connector pin forming the shoulder is aligned with second axial length  14   d  so that the flange can move from a position in engagement with the channel surface of first axial length  14   c  defined by radius  14   f  to a greater depth defined by radius  14   g  in the channel when it reaches second axial length  14   d . This step between the first and second radii serves as a stop surface or shoulder, to be discussed further. 
     With reference to  FIGS. 4 and 6 , an electrically conductive spring member  16  is provided for placement over channel  14   a . Spring member  16  has first and second generally flat plate portions  16   a  integrally joined to respective wall portions  16   b  that are inclined toward each other and integrally joined at a central portion  16   c . A first set of at least one spring contact finger  16   d , preferably two spring contact fingers  16   d , one struck from each respective side wall as shown in the drawings, and extending downwardly, as seen in  FIG. 4 , is adapted to engage a connector pin disposed in the first axial length  14   c . The distal free end portions of fingers  16   d  serve to urge a connector pin received in the channel against the channel surface as well as to make electrical contact therewith. Although the spring member can be provided with only a single set of contact fingers, it can also be formed with a second set of at least one spring contact finger  16   e , preferably two spring contact fingers  16   e , adapted to engage a connector pin received in the third axial length  14   e . Contact fingers  16   e  serve as redundant contacts to provide enhanced reliability. Contact resistance can be minimized by placement of high electrical conductivity material at the distal fee end of either or both sets of contact fingers. Suitable attachment structure for the spring member is provided, such as attachment holes  16   f  in side portions  16   b  as well as guide holes  16   g  for attachment to the housing wall. An electrically conductive tab portion  16   k  extends longitudinally from each spring attachment plate portion  16   a  and is aligned with access holes  14   p  to provide a circuit connection tab for circuitry within the housing, to be discussed. 
     A retainer plate  18  is placed over the spring member to retain and provide support for the spring member. Retainer plate  18  has a recessed central portion  18   a  to accommodate spring member  16  and is provided with attachment holes  18   b  for alignment with holes  16   f  and holes  14   m  of wall portion  12   k  and blind guide holes  18   c  for receipt of guide pins  14   n  also received through spring member guide holes  16   g . Retainer plate  18  is also provided with an upstanding wall portion  18   d  that is received between terminals L 1 ,L 2  completing the end wall of the housing along with portions  12   f    
     As seen in  FIG. 6 , a shouldered connector pin  20  has a radially extending flange  20   b , or shoulder, that can be accommodated in first and second axial lengths  14   c ,  14   d . The shoulder is disposed intermediate to a wire lead connecting portion  20   a  and a cylindrical head portion  20   c . The third axial length  14   e  is formed with radius  14   h  selected to accommodate head portion  20   c.    
       FIGS. 7(   a )– 7 ( d ) show several examples of circuitry and circuit breaker features that can be mounted in housing  12  with which the socket of the invention can be advantageously used without encroaching upon space used for the circuit breaker features and associated circuitry. Socket  14 , having improved retentive capability as well as optimized electrical connectivity can be used as a ground or power connection for a logic and/or sense circuit or the like in a device having such circuits in addition to a circuit breaker function. 
     For example,  FIG. 7(   a ) relates to a mechanical circuit breaker, such as the breaker shown in U.S. Pat. No. 3,361,882 mentioned supra, with which socket  14  is used for auxiliary circuit connections and includes a housing  12  in which is disposed a logic circuit  1 , sense mechanism  2  and an actuation mechanism  3  including suitable circuit breaker contacts and using one socket  14  to interconnect logic circuit with ground and another to interconnect logic with a power source  4 . Sense mechanism  2  is connected to terminal L 1  in a conventional manner while actuation mechanism  3  is connected to terminal L 2   
       FIG. 7(   b ) relates to an arc fault device in which socket  14  is used for providing a circuit ground. Power source  4  is connected to terminal L 1  which in turn is connected to logic  1  and sense mechanism  2 . Actuation mechanism  3  is connected to logic  1  and, through circuit breaker contacts, to terminal L 2 . Socket  14 , connected to logic circuit  1 , provides a ground connection. 
       FIGS. 7(   c ) relates to an arc fault circuit breaker having mechanical auxiliary circuit function and with sockets  14  providing a circuit ground as well as auxiliary circuit connections including conditioning circuit  5   
       FIG. 7(   d ) relates to an arc fault device with mechanical auxiliary circuit function in which sockets  14  provide a circuit ground as well as auxiliary circuit connections. It will be realized that the above arrangements are to be considered as exemplary in utilizing socket  14  made in accordance with the invention and not in a limiting sense. 
     A second preferred embodiment is shown in  FIGS. 8 through 12 . With particular reference to  FIG. 12 , housing  120  of circuit breaker  100  comprises first and second housing halves  120   a ,  120   b , respectively, adapted to receive therebetween circuit breaker  12 ′. Circuit breaker  12 ′ is essentially the same as the circuit breaker of the first embodiment but without a terminal barrier  12   k  and shown with insulation tape  12   m . The circuit breaker includes a conventional push button and latching assembly  30  along with circuit breaker contacts adapted to close and open a circuit path. These assemblies are conventional and will not be described in detail however for further information for similar structure reference can be had to U.S. Pat. No. 3,361,882, noted above. 
     Pin connector socket  14  is formed in housing half  120   a , best seen in  FIGS. 9–11 . As seen in  FIG. 9 , the open pin receiving channel  14   a  is formed in a face surface of wall  120   c  in housing half  120   a  of circuit breaker  100  and includes three axial length,  14   c ,  14   d  and  14   e , as in the first embodiment, and having like radii for receipt of a conventional connector pin  20 . 
     As seen in  FIGS. 10 and 11 , retainer plate  18 ′ has side portions  18   f  for receipt on attachment plate portions  16   a  of spring member  16 ′, as in the first embodiment, however, it also is formed with a cut-out central portion  18   g  to accommodate the central portion of spring member in which contact fingers  16   d  and optional fingers  16   e  are formed. Another variation is that wall portion  120   d , seen in  FIGS. 8 and 12 , is attached to housing half  120   b  whereas in the first embodiment the comparable wall portion  18   d  is attached to retainer plate  18 . Guide holes  16   g  are provided for receiving guide pins  14   n  which are also received in blind holes in the bottom surface of retainer plate  18 ′ (not shown), as in the first embodiment. Attachment holes  16   f ′ are formed in attachment plate portions  16   a  set slightly further apart than in the spring member of the first embodiment, for alignment with attachment holes in bosses  18   h  of the retainer plate. 
     Although retainer plate is formed with a cut-out portion  18   e , if further support is needed for the central portion of spring member  16 ′, the side wall of housing  12 ′ is disposed closely adjacent thereto and will serve that purpose. For other details of socket  14  not specifically discussed in relation to the second embodiment, reference may be had above to the first embodiment. 
     Thus in accordance with the invention, a socket having improved reliability and fewer parts compared to prior art sockets discussed above is provided, a socket having a single metal member that provides both electrical connectivity as well as retention of a shouldered pin. 
     It should be understood that although particular embodiments of the invention have been described by way of illustrating the invention, other embodiments and variations are possible. It is intended that the invention include all modifications and equivalents of the disclosed embodiments that fall within the scope of the claims.