Patent Publication Number: US-6986683-B2

Title: Electrical couplings and components

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation application of application Ser. No. 09/645,099, filed Aug. 23, 2000 now U.S. Pat. No. 6,514,104, which is a continuation-in-part of application Ser. No. 08/986,378, filed Dec. 8, 1997, now U.S. Pat. No. 5,989,065 which was a continuation-in-part of application Ser. No. 08/687,082, filed Jul. 23, 1996, now abandoned which was a continuation-in-part of application Ser. No. 08/521,776, filed Aug. 31, 1995 now abandoned which was a continuation-in-part of application Ser. No. 08/435,122 filed May 5, 1995 now abandoned. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to electrical couplings and components of couplings. The invention is more particularly concerned with couplings having grounding fingers that establish electrical connection between parts. 
   Electrical couplings, such as those between electrical cable clamps to electrical connectors or the like, often have an outer metal shell in several parts that are retained with one another by means of a coupling ring. The coupling ring is rotatably mounted on one part of the coupling and is internally threaded, so that it can be screwed onto the cooperating other part of the coupling to draw parts into mating engagement. The metal shell of the coupling usually provides a part of a ground path for an assembly in which the coupling is connected. While there is electrical connection between the parts of the coupling via the interfacing accessory teeth on the electrical connector and cable clamp, this in many assemblies, provide only a poor electrical connection or high resistance conductivity because of sloppy engagement between interfacing accessory teeth and also compounded by the presence of contaminants such as dirt or grimes or rust or poor assembly. 
   The present invention provides an improved, reliable and consistent electrical continuity between an electrical connector and its cable clamp or “backshell” by use of spring contact grounding fingers secured on one part of the coupling (such as by welding or solder), the fingers being arranged to make a sliding electrical contact with the other part of the coupling when the two are coupled together. The grounding fingers ensure a solid electrical continuity and maintain this continuity even if the two parts of the coupling are not fully mated. 
   It can be understood that the present invention also provide an improved, reliable and consistent electrical continuity between an electrical connector and its coupling part such as a bracket or panel or structure in the aircraft. The grounding fingers ensures a solid electrical continuity and maintain this continuity even if the connector mounting screws were insufficient in having the two parts of the coupling fully mated. This present invention grounding fingers is an improvement to the straight wave springs described in application Ser. No. 08/986,378. 
   BRIEF SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a spring contact grounding fingers which solves the problems of the prior art. 
   It is another object of the present invention to provide an electrical coupling comprising: a first metal member of circular section; a second rotatable member mounted on a part of the first member, an annular recess formed around on inner surface of the second member or an outer surface of the first member; and an electrical contact member located in the annular recess, the contact member having a plurality of spring contact fingers extending axially of the coupling, the contact member being arranged to engage the outer surface of the first member and the inner surface of the second member such that the contact member makes electrical contact with at least the first member. 
   The contact fingers are preferably bent inwardly of the contact member. The contact member may include an annular band encircling the first member and integral with the fingers, the fingers projecting from the opposite edges of the band. The spring contact grounding may be of beryllium copper. The first member may be a first shell and the second member a coupling ring, the annular recess being formed around the inner surface of the coupling ring. The annular band of the contact member is axially installed on the first shell thus the other end of the contact member is arranged for contact with an outer surface of a second shell. The contact member may be entirely enclosed within the coupling ring. 
   It is a further object of the present invention to provide an electrical coupling comprising: a first metal shell of circular section; a coupling ring mounted on a part of the first shell, the coupling ring being arranged to engage a surface of a part of a second shell; an annular recess formed around an inner surface of the coupling ring; and the contact member having a plurality of spring contact fingers extending axially of the coupling and (for this description but not limited to) bent inwardly into first and second resilient U-shape portions at opposite ends, the contact member being arranged to engage the outer surface of the first shell and an outer surface of the second shell such that the contact member makes a low impedance connection between the two shells. 
   Yet another object of the present invention to provide an electrical coupling comprising: a first member of circular section; a second rotatable member mounted on a part of the first member; an annular recess formed around an outer surface of the first member; and an electrical contact member located in the annular recess, the contact member having a plurality of contact fingers extending axially of the coupling and bent inwardly into first and second resilient U-shaped portions at opposite ends of each finger, the fingers at both ends of the contact member engaging the recess in the first member and an outer surface of the contact member engaging the inner surface of the second member such that the contact member makes electrical and low impedance connection between the first and second members. 
   A still further object of the present invention to provide a contact member for making electrical and low impedance connection between different parts of a coupling assembly, the contact member comprising: a circular band of resilient metal having fingers along opposite edges of the band, the fingers being bent inwardly to form resilient U-shape portions such that the contact member can be retained in an annular recess in the coupling with the fingers along opposite edges establishing low impedance connection between different parts. 
   It is also an object of the present invention to provide a contact member for making electrical and low impedance connection between different parts of a coupling, the contact member comprising: a circular band of resilient metal, a plurality of contact fingers along opposite edges of the band, the fingers being bent inwardly to form resilient U-shape portions such that the contact member can be retained in an annular recess in one of the parts of the coupling with the fingers making electrical contact with the one part and with an outer surface of the contact member contacting an inner surface of the other part such that the contact member establishes a solid and consistent electrical connection between the two parts. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is an exploded, partly cut-away elevation view of the coupling; 
       FIG. 2  is a sectional elevation view of a part of the coupling to a larger scale; 
       FIG. 3  is an elevation view of an inner surface of the contact member; 
       FIG. 4  is a sectional view of the contact member along the line A—A of  FIG. 3 ; and 
       FIG. 5  is a sectional elevation of a modified assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The electrical coupling comprises a forward part in the form of an electrical connector  1  and a rear part in the form of a cable clamp or backshell  2  that is, in use, secured to the rear of the electrical connector  1 . 
   The electrical connector  1  shown for this description is a Plug that has a first outer metal shell  10  supporting a coupling ring  11  at its forward end by means of which the coupling is secured via a retaining ring (not shown). Inside the shell  10  an electrically insulated grommet  12  supports plurality of electrical contacts  13 , which may be either sockets or pins, the contacts being connected to respective wires  14  extending rearwardly. The grommet  12  projects a short distance beyond the rear end of the shell  10 . On its outer surface, the shell  10  has a screw thread  15  spaced from the rear end by a smooth, annular contact region  16 . A series of triangular teeth  17  (designated as MS3155 accessory teeth) extends around the rear end of the shell  10 . 
   The cable clamp or backshell  2  has a second outer metal shell  20  shown in  FIG. 2  with a slightly smaller external diameter than that of the first shell  10  in the electrical connector  1 . The shell  20  is similarly provided with MS3155 accessory teeth  27  at its forward end shaped to lock into the teeth  17  on the shell of connector  1 . The shell  20  is hollow with a bore  21  extending along its length through which extend the wires  14 . At its forward end, the bore has a tapered portion  22  adapted to envelope the projecting rear end of the grommet  12  when the two parts are secured together. A backshell coupling ring  23  is rotatably mounted on the shell  20  and project from its forward end. On its surface at its forward end, the ring  23  has a thread  25  shaped to engage the external thread  15  on the shell  10  of the connector  1 . Just rearwardly of the thread  25 , the ring  23  has an internal annular recess  26  of rectangular section. The recess  26  extends rearwardly approximately with the base of the teeth  27  so that the forward end of the teeth  27  project about half way along the length of the recess. 
   The backshell  2  also includes an electrical grounding contact member  30  clipped within the coupling ring  23 . The contact member  30  is a strip or band of conductive, spring metal, such as beryllium copper, about 0.005 in thick, and is cut with a series of slots  31  and  32  along opposite edges to divide the strip into two series of spring fingers  33  and  33 ′. The contact member  30  is bent into a circular shape and opposite ends joined together. The spring fingers  33  and  33 ′ extend axially of the assembly and are bent at their free ends into two substantially U-shape resilient portions  34  and  34 ′. The fingers,  33  and  33 ′ are separated from one another by a straight intermediate portion  36  provided by the central part of the contact strip. The resilient portions  34  and  34 ′ each have a straight inclined ramp  37  and  37 ′ directed centrally of the contact strip and bent upwardly at its free end into a contact region  38  and  38 ′ of curved profile. The left hand ramp  37  forms a flared opening to the contact member  30 . The contact member  30  is located within the recess  26  around the coupling ring  23 , with the straight intermediate portion located on the floor of the recess. In this position, the free end of the right hand resilient portion  34 ′ contacts an annular contact region  28  around the outer surface of the shell  20  at its left hand end, in the region of the teeth  27 , and is compressed slightly radially outwardly, so that a solid electrical contact is established between the shell  20  and contact member  30 . 
   The backshell  2  is brought up to the rear of the connector  1  and the thread  25  on the backshell coupling ring  23  is engaged with the thread  15  on the shell  10  of the connector  1 . The coupling ring  23  is rotated about the backshell  2  to draw the two parts of the coupling further into engagement. As the rear of the connector  1  enters the flared, rear end of the grounding contact member  30 , the contact region  38  makes sliding electrical contact with the contact region  16  at the rear end of the shell  10 , the external diameter of the shell  10  being slightly greater than the internal diameter of the contact member  30  in its contact region  38 . Rotation of the coupling ring  23  does not cause rotation of the grounding contact member  30  because this is not attached to the coupling ring  23  by welding or otherwise. When the coupling ring is rotated to its full extent the teeth  17  are in engagement with teeth  27  and the spring fingers  33  and  33 ′ establish an effective electrical interconnection between the two shells  10  and  20 , independently of the coupling ring  23 . 
   The grounding contact member  30  has the advantage that it can be preformed into a circular shape before assembly into the coupling, which enables a close control to be maintained on the finished dimensions. The contact member  30  is easily clipped into the recess  26  in the coupling ring  23  and the ring  23  subsequently pushed rearwardly onto the shell  20  of the backshell  2 . As this happens, the rear resilient portion  34 ′ is deformed and is urged into electrical contact with the outside shell  20 . Because the contact member  30  is assembled before the coupling ring  23  it enables quality and electrical testing of the assembled contact member  30  to be carried out more readily. The simple shape of the spring fingers  33  and  33 ′ makes them easy to manufacture. The resilience of the contact member  30  also helps reduce the effects of vibration on the coupling by damping out the vibration, even if the coupling ring should become loose. The contact member  30  also helps to maintain electrical continuity between the two shells  10  and  20  even if the coupling ring  23  should become loose. It can be seen, therefore, that the electrical continuity through the coupling has a very high integrity. This is very important in that it ensures that the electrical screening of any system including the coupling is maintained. This gives the system a high immunity to electrical magnetic interference (EMI) and lightning strikes. 
   It will be appreciated that the grounding contact member  30  could be use to ensure a good electrical path between other parts of a coupling or between parts of two mating couplings For example, as shown in  FIG. 5 , the contact member  30  is used to make electrical connection between an inner member  50  and an outer rotatable member  51 . In the arrangement illustrated, the contact member  30  is located in a recess  26  around the outer surface of the inner member  50  with its intermediate portion  36  facing outwardly to engage the inner surface of the outer member  51 . Alternatively, the contact member  30  could be located in a recess around the inner surface of the outer member  51 .