Abstract:
The shielding arrangement of the present invention is equipped with a conductive inner shell ( 10 ) that has opening ( 11 ) for receiving a mating connector ( 40 ), and an outer shell ( 20 ) that encloses parts of inner shell ( 10 ). The outer shell serves to resist outward force applied by the inserted mating connector to the inner shell during mating by having bent sections ( 22 ) extending inward near an edge to engage the conductive inner shell ( 10 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to electrical connectors and more particularly to a shielding arrangement for such connectors. 
     BACKGROUND 
     Shielded connectors having a shield member surrounding the housing and protecting signals from ambient electromagnetic noise are known. During mating of such connectors, the shield members generally contact each other to establish a common potential between them. 
     Known examples in the prior art include shielded connectors that have a plurality of contacts in a housing surrounded by a single shield member. The single shield member typically has an opening at an end into which the shield member of a mating shielded connector is inserted. Another known shielding arrangement places projections on the inner circumference of an opening in shield members for engaging the mating shielded connector is inserted to achieve point contact at a plurality of locations on the shield member of the mating shielded connector (see Utility Model HEI 1-38866). These projections serve to fasten the engaged shield members which is thought to increase the reliability of the electrical contact between them. 
     With the ongoing development of computer technology comes a need for greater signal density through such connectors as well as the need for increasing signal transfer rates. As the size of these multi-contact connectors increases the openings that receive the complementary shield member increase accordingly. After repeated mating cycles these large openings tend to stretch because of the outward force applied by the projections described above. The result is that movement occurs between the mated connectors causing intermittent electrical contact at the signal and/or shielding connections. 
     The intermittent contact along the shield member may only occur at certain locations along the opening. This causes current to pass over the shield at the contacting sections and to be blocked at those sections with poor or no contact thus reducing the electromagnetic interference protection. In applications where the shield is grounded, the ground path will become long due to detours of the conduction path caused by the poor or non contacting sections, which may affect the fall of pulse signals and impede high-speed signal transmission. 
     SUMMARY 
     The object of this invention is to provide a shielded connector arrangement having improved electrical contact between the shield members of mated connectors. 
     This and other objects are achieved by providing a shielded connector that has a plurality of signal contacts and a shielding shell that engages a mating connector. The shielding shell being equipped with a conductive inner shell which receives the mating connector is inserted and an outer shell that supports the inner shell. The outer shell serves to prevent the inner shell from expanding due to the insertion of the mating connector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described by way of example with reference to the accompanying figures of which: 
     FIG.  1 (A) is a front view of the shielded connector. 
     FIG.  1 (B) shows a B—B cross-section diagram of the shielded connector of FIG.  1 (A). 
     FIG. 2 is a plan view that shows the shielded connector of FIG. 1 mated with a complementary mating connector. 
     FIG. 3 is a perspective view of the shell member utilized in the connector of FIGS.  1  and  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention will first be described generally with reference to FIG.  1 . Shielded connector  100  has an inner shell  10  and an outer shell  20 . Contacts  30  are disposed inside the inner shell  10 . In the preferred embodiment, the contacts  30  are male, and  50  of them are installed along the top and bottom in insulating housing  31 . Furthermore, contacts  30  are equipped with terminals  32  which are connected to the conductors (not shown) of shield wires  60  (see FIG.  2 ). 
     As the two dotted lines in FIG.  1 (B) show, mating connector  40  includes contacts  43  on housing  42 . The outer circumference of the mating connector  40  is formed by shield member  41 , and the contacts  43  are matable with contacts  30  of shielded connector  100 . Mating connector  40  has tines  44  (see FIG. 2) with which contacts  43  connect on a circuit board (not shown). 
     Shielded connector  100  is preferably covered by a pair of insulating members that extend over the outer shell  20 . The pair of insulating members serve to prevent shocks to the user and serve as mounts for jack screws. The shielded connector  100  is shown in FIG. 2 as being covered by insulating member  50  only on its bottom side for purposes of explanation, and jack screws  51  are located opposite ends. 
     The rear end of shielded connector  100  shown in FIG. 2 is designed to secure a shielding braided wire (not shown) of shield wire  60  with a conductive holding member  70  which makes electrical contact with outer shell  20 . 
     Inner shell  10  is formed in a tube-shape from a single piece and has an opening  11  as shown in FIG.  1 (A). A plurality of projections  12  extend along the circumference of inner shell  10  for engaging the outer circumference surface of shield member  41  of mating connector  40 . The projections  12  are disposed in two columns along the length in a zigzag pattern (see FIG.  2 ). 
     Outer shell  20  is disposed on the outer side of inner shell  10 , and formed of a pair of shell members  21  which are preferably of the same shape and size. As shown in FIG.  1 (A) they are fastened to each other such that their sides overlap from above and below. As shown in FIG.  1 (B), integral bent sections  22  extend along the outer shell  20  toward the inside facing the outer circumference surface of inner shell  10 . These bent sections  22  engage the inner shell  10  near the projection to prevent expansion due to the insertion of mating connector  40 . 
     The force exerted on the inside of inner shell  10  by insertion of mating connector  40  is distributed across projections  12  over a large area. Furthermore, since shielded connector  100  is relatively wide there is a danger that the electrical contact with shield member  41  of mating connector  40  will be broken near the center parts of the inner shell  10 . Moreover, while inner shell  10  could be formed with a plate thickness that has sufficient strength to endure the outward force from the inner side that it receives due to insertion of mating connector  40 , the shape of the inner shell is often restricted by standards. Also, the bends required to form the inner shell become problematic as the material thickness is increased. 
     Optionally, in addition to the bent sections  22  formed as a single piece with outer shell  20 , the thickness of the outer shell  20  itself may be increased to withstand the force exerted by the inner shell  10 . As another option, a separate piece may be used to reinforce the outer shell  20 . These bent sections  22  serve to realize the shortest ground path in shielded connector  100  which extends through projections  12  and the outer circumference surface of shield member  41  of mating connector. 
     Outer shell  20  has projections  23  located on the inner side of bent sections  22  that project toward inner shell  10  as shown in FIG.  1 (A) and FIG.  2 . The inner shell  10  and outer shell  20  are properly positioned using these projections  23 . Joining projections  24  located in the four corners of the outer shell  20  extend toward a groove in the insulation member  50  for positioning it with insulation member  50  (see FIG.  2 ). 
     Referring now to FIG. 3, shell member  21  includes a horizontal plate “a” having the bent section  22 , projection  23 , joining projection  24 , and side wall “b”. Side wall “b” is upright so that it connects with one end of the periphery of horizontal plate “a”. The other end of side wall “b” is left free. 
     This shell member  21  is formed from a single sheet metal plate and is equipped with cuts from the end left free to horizontal plate “a” in the parts of side wall “b” that correspond to transition points for bending. 
     The outer shell  20  that engages shell members  21  is also formed of a single sheet of metal in and may have a plate thickness which is thicker than inner shell  10 . Accordingly the bent sections,  22  formed as a single unit with outer shell  20  are stronger than inner shell  10  and can better withstand the force that the inner shell  10  bears due to the engagement with the mating connector  40 . 
     As a reference for the center in the direction of length of horizontal plate a, rear left side wall “b 3 ” and rear right side wall “b 4 ” are offset front to back relative to one another. In other words, in FIG. 3, rear right side wall “b 4 ” is erected in front of rear left side wall “b 3 ” and is connected to horizontal plate “a”. Furthermore, rear left side wall “b 3 ”, which is positioned off from the center has a raised section  27  formed out of it by cutting and raising. Stops  26  for positioning housing  31  are formed on left side wall “b  1 ” and right side wall “b 2 ” projecting into their respective interiors (also see FIG.  1 ). 
     Outer shell  20  is assembled by facing the edges of free side walls “b” toward each other and engaging the two shell members shown in FIG.  3 . In the engagement of these shell members  21  with each other, raised section  27  is joined to the mating shell member on it&#39;s rear right side wall “b 4 ” (also see FIG.  2 ). This raised section  27  engagement with the rear right side wall “b 4 ” is intended both to make the engagement of shell members  21  with each other more secure and to create electrical contact between shell members  21 . Accordingly, it reliably maintains the same electric potential over the entire outer shell  20 . Once the outer shell is assembled, the bent sections  22  are positioned over the projections  12 ″ at the end of the line. 
     Furthermore, in the engagement of shell members  21  with each other, outer shell  20  can be maintained at a predetermined thickness by having it touch and connect with stop  26 , which is installed on the shell member that engages stop  26  (see FIG. 1 (A)). 
     In the shell member  21 , braid receiving section  28 , which covers half the circumference of the shielding wire braid (not shown) of shield wire  60 , is installed between rear left side wall “b 3 ” and rear right side wall “b 4 ”. The entire circumference of the wire braid (not shown) is therefore covered by the braid receiving sections  28  upon assembly of shell members  21  with each other. 
     Advantageously, the shielded connector  100  is equipped with a plurality of projections  12  that project to the interior of inner shell  10 , and supports the exterior surface of inner shell  10  with the tip of outer shell  20 , which has a plate thickness that is preferably thicker than inner shell  10 . Accordingly, the force that inner shell  10  is subjected to from the inner side by the insertion of mating connector  40  is borne by outer shell  20 , and the expansion of the central part of inner shell  10  is prevented. As a result, the shielded connector  100  can increase the reliability of electrical contact between inner shell  10  and shield member  41  of mating connector  40 , and can also increase the reliability of electrical contact between inner shell  10  and outer shell  20 . Moreover, since outer shell  20  of the present working configuration is formed by engaging shell member  21  of the same shape, only one dye is needed, enabling manufacturing costs to be kept down and facilitating part management. Since shell members  21  are joined to each other by raised portions  27 , the reliability of electrical contact between shell members  21  is increased. 
     While the invention has been described utilizing in view of preferred embodiments, variations that are within the spirit of the invention will, be apparent to those skilled in the art. For example, projections  12  installed on the inner circumference of inner shell  10  may also be installed on the outer circumference surface of the mating connector to be engaged, or may be installed on both, and their shape may be dimple-like bumps rather than projections as shown in the drawings. The invention is therefore intended to be limited only by the appended claims.