Abstract:
A reduced weight and size shielded receptacle connector includes an internal insulative connector housing having top and bottom walls, without any sidewalls interconnecting the top and bottom walls together. A plurality of conductive terminals are supported within the connector. A receptacle portion of the connector is formed in cooperation with the top and bottom walls of the connector housing and with a pair of metal sidewalls formed by bending a shield member around parts of the connector housing. A metal retaining shield is provided that also overlies a portion of the connector housing and which is partially retained on the connector housing by the metal shell. The shield not only provides shielding, but also serves to retain the opposing connector in mating engagement with receptacle connector by way of three retention members that extend in and engaged the opposing connector in three different directions.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to shielded connectors, and more particularly to small-sized connectors having improved opposing connector retention characteristics. 
   It is known that metal shields may be disposed on the exterior circumferential surface of box-shaped insulative housings of connectors for the purposes of preventing interference, such as electrical noise. One example of such a connector is disclosed in Japanese Utility Model Application Laid-Open No. Hei 5-34679, Japanese Patent Application Laid-Open No. Hei 10-83866, and others. The connector disclosed in these publications is one that is mounted to a substrate such as a printed circuit board and is formed so that a pair of substantially U-shaped shield members made of metal plates are overlapped on four or three surfaces of the exterior of a substantially box-shaped insulative connector housing. 
     FIGS. 15 and 16  of this application show such a conventional shielded connector.  FIG. 15  illustrates a receptacle style connector R, while  FIG. 16  illustrates a plug style connector P. The receptacle connector R is typically smaller in size than the plug connector P, so it should be understood that the drawings are not to scale and that the representative size of the receptacle connector R has been enlarged for clarity. 
   As for the receptacle connector R of  FIG. 15 , the shield of the connector is composed of a metal shell  320  that is disposed on the outer surface of the connector housing. It is shaped in a substantially U-shape as viewed from the top and the connector shield also includes a metal shield plate  330  that is U-shaped in cross-section that is disposed between the metal shell  320  and the connector insulative housing. The metal shell  320  is formed so as to cover three surfaces, i.e., the front surface and both side surfaces of the insulative housing, while the shield metal plate  330  is disposed to cover three surfaces, i.e., the top surface and both side surfaces of the insulating housing. Thus four surfaces of the connector housing are actually covered with the shield, i.e., the front surface, the top surface and both side surfaces. An engagement piece  303  is provided on the metal shield plate  320  that is engaged with an engagement recess portion  311  of a terminal portion  310  that serves as a metal shield for opposing the plug connector P. 
   The metal shell  320  has a front surface shield portion  323  and side surface shield portions  324  on both sides of the connector. An engagement sleeve portion  307  has an opening  321  into which the terminal portion  310  of the plug connector P is inserted, and is provided in the front surface  323  of the shield portion. As illustrated, the engagement sleeve portion  307  is formed substantially into a rectangular sleeve shape so that it projects outwardly on the front surface of the connector. This metal shell  320  is typically formed by drawing that specific portion of the engagement sleeve portion  307 , after the entire metal shield plate has been stamped out from a blank. A convex portion  308  may be formed as a polarizing portion that is engaged with a recess  312 . Conductive terminals  313 , having contact portions are arranged within the plug connector P. 
   Connectors such as those shown in  FIGS. 15 &amp; 16  tend to be small in size, as well as the circuit boards upon which they are mounted. However, it is desirable to reduce the manufacturing cost of such connectors without losing the dimensional stability of the connector. Thus, it is a goal of this invention to keep the connector small in size while maintaining the dimensional stability of the shield and retaining its electrical properties. 
   However, in the prior art connectors described above and shown in  FIGS. 15 &amp; 16 , there is a problem. The manufacturing cost of these connectors is high because the engagement sleeve portion  307  is formed by drawing. The outer profile of these connectors is also increased because of this drawn structure, resulting in difficulty in achieving the goal of miniaturization. The engagement sleeve portion  307  is formed by drawing so that there is a problem that the sleeve portion  307  does not have satisfactory dimensional stability. Furthermore, a large force, such as a twisting force, may be applied to the engagement sleeve portion  307  when engaged with the plug connector P. The forces generated by repeated removal and insertion may weaken the drawn portions of the connector. 
   Also, in these type of connectors, it has been found that there is room for improvement by reducing the connector size and the overall weight of the connector, while still maintaining the electrical performance of the shield. The conventional connector housing used with such connectors is formed substantially into a box-like shape with six surfaces. In view of the inherent function of the insulative housing, it is sufficient to have the housing to support the shield member in its extent around the housing and its internal contacts, as well as supporting the contacts. In the aforementioned conventional connectors, although the housing has structure supports the metal shield and has a desired mechanical strength, it has an unnecessarily large thickness for its structural stability. This creates a problem that inhibits the goal of attaining further miniaturization and weight reduction. 
   Additionally, in this type of connector where repeated removal and insertion of the plug connector P to the receptacle connector R occurs, frictional wear or deformation can occur with the drawn engagement portions, so that there is a fear that the contact stability between the shield members of the plug and receptacle connectors is gradually reduced over time, and frictional wear may result in a displacement between in the two respectively engaged shields, reducing the mechanical stability of the two connectors. For this reason, depending on the frequency and condition of the insertion/removal of the two connectors, there is another fear that either the grounding stability of the overall connector system will be degraded (i.e., the ability of electrical noise to be led by the shields to a ground on the circuit board) as well as the stability of the engagement between the two connectors. 
   In particular, with respect to the grounding stability problem, due to the displacement between the two shields, there is a fear that the electrical connection between the plug connector and the receptacle connector is unstable and it will be difficult to lead the electrically transmitted noise components to the ground on the circuit board. 
   It is also possible to form the shields of the connectors by way of die-casting, instead of the drawn members shown. However, the ductility of such die-cast parts is poor as compared to sheet metal and in these size and style connectors, a high precision for engagement desired. In the reduced size, excessive stresses may develop during insertion and removal of the connectors, so that a fear of deforming the drawn or die-cast shield engagement members is real. 
   The present invention is directed to an improved connector that overcomes the aforementioned disadvantages. 
   SUMMARY OF THE INVENTION 
   It is therefore a general object of the present invention is to provide a shielded connector that is reduced in size and in weight, particularly on the receptacle side of the connector, and which is further durable suitable for repeated use in insertion and removal cycles, thereby giving a reliable connection to an opposing plug connector, yet being stable during engagement of the two connectors and being effective in shielding the contacts of the connector from electrical noise when connected to an opposing plug connector. 
   Another object of the present invention is to provide a reduced size receptacle connector of the USB type for mounting on a circuit board, the connector having a connector body having top and bottom walls extending horizontally therefrom, but without having any sidewalls, the top and bottom walls cooperating with side pieces of a metal shell overlying the connector housing to define an internal cavity of the connector that engages with an opposing plug connector. 
   Yet another object of the present invention is to provide a reduced size and weight USB style connector in which the connector includes a housing formed from electrically insulative material, the connector housing having a body portion that supports a plurality of conductive terminals thereon, the connector housing further including top and bottom walls extending forwardly from the housing body portion in a cantilevered fashion, and the connector housing not having any vertical sidewalls for joining the top and bottom walls together, the connector further including a conductive metal shell encircling most of the exterior surface of the connector body, the shell including a top plate, a front plate and two side plates that are formed around the top and bottom plates and the connector body, the metal shell side plates defining the sidewalls of the receptacle of the connector and the metal shell retaining a separate metal shield member in place upon the connector housing. 
   Yet still another object of the present invention is to provide a reduced size connector for mounting to a circuit board, the connector having a reduced size by virtue of its structure which includes an insulative inner housing portion that includes top and bottom walls cantilevered from a body portion, the top and bottom walls defining the top and bottom extends of a plug-receiving receptacle, the connector housing includes a shield component mounted thereon that includes side pieces that extend between the top and bottom walls of the connector housing and which, with the top and bottom walls, cooperatively define a receptacle of the connector. 
   The present invention accomplishes these and other objects by way of its novel and unique structure, utilizing the following means to solve the aforementioned problems. A first means of the present invention is characterized by way of a shielded connector having an insulative housing supporting at least one conductive terminal, and a shield member that overlies a surface of the connector housing, the shield member having a metal shell with a frame portion for surrounding an opening of the housing in which at least one conductive terminal is disposed, and a metal shield disposed between the metal shell and the connector housing, wherein the connector housing is formed without sidewalls, but retains a top wall, a bottom wall and an intermediate contact support that project longitudinally through the connector housing, the open sidewall portions of the connector housing being covered by portions of the shield member. 
   With this particular means, the sidewalls of the connector housing may be eliminated, and thus it is possible to attain both of the goals of miniaturization of the connector and weight reduction of the connector insofar as the eliminated sidewalls are concerned. Also, because both of the opened sidewalls of the connector housing are covered by the shield member, it is possible to maintain both sufficient shield performance of the entire connector, and also maintain the desired mechanical strength of the connector. 
   A second means of the present invention is characterized by the metal shield which has a top surface shield portion for covering the top surface of the connector housing, two side surface shield portions for covering both open sides of the connector housing, and spring portions for holding the receptacle connector together in engagement with a plug connector, the spring portions having left and right side surfaces facing inwardly of the connector and in opposition to sides of the opposing plug connector. 
   With this second means, the spring portions are provided on the side surface shield portions and because the connector housing has no sidewalls, the spring portions may be brought into contact with the opposing left and right side surfaces of the plug connector to thereby will hold the plug connector effectively in a stable condition, without any rattling or displacement. Thus, the electrical connection effected by the connector is stable in a manner in which any transmitted electrical noise is passed directly to the ground located on the circuit board to which the receptacle connector is mounted. The spring portions are brought into contact with the side surfaces of the opposing plug connector, so that resistance due to friction between the spring portions and the side surfaces of the plug connector is sufficient to maintain the two connectors engaged together. The stability that occurs during insertion and removal of the two connectors is enhanced due to this frictional resistance caused by the spring pieces. 
   A third means of the present invention is characterized in that another engagement piece is provided on the top of the receptacle connector that engages with a recessed portion of the surface of the opposing plug connector. This third engagement piece is guided into the insulating housing of the connector through an opening that is formed in the top plate portion of the connector housing. According to this means, the engagement piece is provided on the top surface shield portion of the metal shield so that it will engage the recessed portion of the surface of the plug connector to hold the plug connector in place within the receptacle connector. In addition to the positioning of the opposing connector caused by the left and right side spring pieces, this engagement piece provides a further positioning along the top face of the plug connector to hold the plug connector in place within the receptacle connector. The three engagement pieces exert a force on the plug connector in three directions, so that the stability of the connector during repeated insertion and removal is enhanced, as well as the electrical connection between the plug and receptacle connectors. The top plate portion of the connector housing is formed with an opening for receiving the engagement piece within the confines of the connector housing, so that this opening further contributes to the weight reduction obtained with the present invention. 
   A fourth means of the present invention is characterized in that the engagement piece of the connector is received within a recess formed in the shield of the insertion end of the opposing connector when the opposing connector is inserted into the opening of the connectors of the present invention. According to this fourth means, it is possible to prevent accidental disengagement of the two connectors. Additionally the stability of the engagement between the two pieces is enhanced. 
   These and other objects, features and advantages of the present invention will be clearly understood through consideration of the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a receptacle connector for mounting on a circuit board which is constructed in accordance with the principles of the present invention; 
       FIG. 2  is a front end view of the connector of  FIG. 1 ; 
       FIG. 3  is a sectional view of the connector of  FIG. 2 , taken along lines  3 — 3  thereof; 
       FIG. 4  is a sectional view of the connector of  FIG. 2 , taken along lines  4 — 4  thereof; 
       FIG. 5  is a side view of the connector of  FIG. 1 ; 
       FIG. 6  is a top plan view of the connector of  FIG. 1 ; 
       FIG. 7  is a bottom plan view of the connector of  FIG. 1 ; 
       FIG. 8  is a sectional view of the connector of  FIG. 6 , taken along lines  8 — 8  thereof; 
       FIG. 9  is a sectional view of the connector of  FIG. 6 , taken along lines  9 — 9  thereof; 
       FIG. 10  is a plan view of a metal blank that is formed into the metal shell utilized on the connector of  FIG. 1 ; 
       FIG. 11  is a front end view of the metal shield of  FIG. 10  that is placed onto the connector housing of the connector of  FIG. 1 ; 
       FIG. 12  is a sectional view of the metal shield of  FIG. 1 , taken along lines  12 — 12  thereof; 
       FIG. 13  is a top plan view of the metal shield of  FIG. 11 ; 
       FIG. 14  is a side view, taken from the right, of the metal shield of  FIG. 11 ; 
       FIG. 15  is a perspective view of a prior art shielded receptacle connector: and, 
       FIG. 16  is a perspective view of a prior art shielded plug connector. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An improved shielded connector R constructed in accordance with the principles of the present invention is illustrated in  FIGS. 1–14  and in the embodiment shown, a “DIP” (Dual-In-line Process) type electrical connector of USB (Universal Serial Bus) style is illustrated as an example of a connector to which the principles of the present invention may be applied. The connector shown is one that is intended to be mounted on a substrate, such as a circuit board (not shown). As illustrated in  FIGS. 1–3 , the shielded connector R is provided with an inner insulated housing for supporting one or more conductive terminals or contacts  1 , and a metal shell  20  for overlying the outer surface of the connector housing to thereby shield the terminal  1 . The metal shell  20  includes a front frame panel portion  22  that defines an opening  21  in the shell  20  and the connector R. This opening  21  receives a portion of an opposing plug connector P, such as the one shown in  FIG. 16 . The front frame portion  22  can be seen to entirely surround the opening  21 . 
   The front frame portion  22  is formed as a single, seamless piece and it surrounds the entire extent, or circumference, of the opening  21  of the connector R. The front frame portion  22  may include, if desired, a convex portion  22   a  that has a profile greater than that of the frame, i.e., is larger than it, so as to form a polarizing feature at the opening  21  that mates with a corresponding recessed portion of the opposing plug connector P. The opposing plug connector P will be substantially the same in size and detail as that shown in  FIG. 16 , so that it is not necessary to reproduce it here. 
   The insulative housing  10  of the connector has a box-like shape with a plurality of openings. The housing  10  is preferably formed by molding from a resin or plastic that possesses a high mechanical strength. As can be seen from  FIGS. 3 ,  4   8  and  9 , the connector housing  10  has a top plate, or wall portion,  10   a  that forms a part of its top surface, a bottom plate, or wall portion,  10   b  that forms a part of the bottom surface of the connector housing, a front surface, or wall portion,  10   c  with an insertion opening  21  formed therein for receiving a leading portion of the opposing plug connector P, and a rear body portion  10   d  having an extended opening  11   a  through which the conductive terminals  1  extend for connection to a circuit board (not shown). The top and bottom wall portions  10   a ,  10   b  are cantilevered out from the rear body portion  10   d . These terminals  1  may include solder tails that may be surface mounted to the circuit board, or as illustrated, they may include the through-hole tails illustrated. Importantly, and as explained in greater detail below and as illustrated in  FIGS. 8 &amp; 9 , the housing  10  is formed with out any sidewalls, or side plate portions. Rather, it has a general U-shape in cross-section, as shown in  FIG. 4  with a terminal support wall portion  11  disposed between the top and bottom wall portions  10   a ,  10   b . The terminal support wall portion  11  is also cantilevered from housing rear body portion  10   d.    
   Turning now to  FIG. 3 , the housing  10  includes an opening  10   e  in its top surface that receives the engagement portion  32  of a metal shield  30  that is applied to the top plate portion  10   a  of the housing  10 . This top plate portion  10   a  includes a front portion  10   c  ( FIG. 3 ) that has a thin recessed portion  10   f  formed therein which approximately matches the thickness of the metal shell  20 . This is because the metal shell  20  extends partially over the metal shield  30  and accordingly, the thickness of the top plate portion  10   a  is reduced so that the exterior surface of the metal shell  20  will be flush with the surface of the metal shield  30 . 
   As mentioned above, no sidewalls are formed in the housing  10 , and therefore as illustrated in  FIG. 4  the top plate portion  10   a  and the bottom plate portion  10   b  of the housing  10  extend out from the rear body portion  10   d  of the housing  10  in a cantilevered fashion. For stability purposes, the housing rear body portion  10   d  preferably has a large thickness as compared to the plate portions for the purpose of enhancing the mechanical strength of the connector housing  10 . 
   The connector housing  10  has a substantial box-like shape and is provided in its interior portion with an inner or central terminal support portion  11  that supports one or more conductive terminals  1  in the connector housing  10 . The terminals are shown best in  FIG. 3  and each terminal includes an extended, curved contact portion  3  formed along the body thereof and a tail portion  4  that extends out of the connector housing  10 . The housing terminal support portion  11  has an opening that receives the terminal and includes a ledge or end portion  13  against which a free end  2  of the terminal  1  bears. The contact portion  3  of the terminal protrudes through the bottom of the terminal support portion  11  and extends into part  12  of the connector insertion opening. The curved contact portion  3  is formed near the free end  2  of the terminal  1 , so that the spring effect that ensures good contact between the terminal  1  and a facing terminal of an opposing connector P is enhanced. 
   The tail portions  4  of the terminals  1  exit the housing  10  by way of a rear passage or port  11   a , and may be bent downwardly to extend straight and project through the lower part of the connector housing  10 . The tails  4  may extend straight as illustrated for insertion into a through hole formed in the circuit board to which the connector is mounted or they may be bent into a horizontal plane for soldering to contact pads on the circuit board. The receptacle connector R illustrated is shown as a four-pin connector having four terminals  1  arranged within the connector housing  10 . In order to avoid bunching of the terminal tails  4 , the tails are staggered as shown in  FIG. 3 . Other terminal arrangements and types are contemplated. 
   The metal shell  20  is formed after it is stamped out of a suitable metal blank by bending it. The metal blank  20 A is illustrated in plan view in  FIG. 10 . It can be seen to include a plurality of panels that are integrally attached to each other, such as a front surface shield panel, or portion  23  indicated at  101 , two side surface shield panels, or portions  24  on both sides of the front surface but spaced apart therefrom as indicated at  102 , a top surface shield panel, or portion  25  as indicated by  103 , a bottom surface shield portion  26  as indicated by  104 , two engagement pieces  27  as indicated by  105 , and fixing pieces  28  as indicated by  106 . All these panels, portions and pieces form the part of the metal shell that overlies the outer surfaces of the connector housing  10 . These overlying portions indicated by  101  to  106  are formed by bending them along the broken lines in  FIG. 10 . Thus, it will be understood that the metal shell  20  has what may be considered an overlapped structure where at least one portion overlies each of five of the six surfaces of the connector housing  10 . Therefore the metal shell  20  has at least one portion that overlies each of these five surfaces of the connector housing that are all formed by way of bending or forming so that the metal shell  20  may be fixed readily and firmly to the connector housing  10 . 
   Joint portions ( FIG. 1 ) of the shell  20  are formed during the bending of the metal shell  20  along the broken lines of  FIG. 10 . These joint portions include the engagement pieces  27  that are located on both sides of the connector housing  10  and which are received within corresponding complementary shaped cutaway openings  29  so that both the engagement pieces  27  and the sidewalls  24  of the metal shell  20  are flush with each other. As a result, these joints do not project outwardly on the exterior surface of the connector, as they would if they were drawn as in the prior art connectors discussed above. The cutaway openings  29  of the shell sidewalls  29  are preferably sized so as to accommodate the engagement pieces  27  as members of the same thickness. The metal shell  20  may also include tabs  24   a  that project from the metal shell  20  and which are received within slots formed on the circuit board, which will typically have contacts that lead directly to an earth or ground of the device in which the connector R is used. 
     FIG. 1  illustrates the metal retainer shell  20  applied to the connector R after bending and with the metal shield  30 , also applied to the connector housing  10 . The metal shield  30  is also preferably stamped from a single metal blank and is bent into its desired shape in place on the connector R. The metal shield  30  is disposed between the insulative housing  10  and the metal shell  20  and is restricted in its place upon the housing  10  by the metal shell  20 .  FIG. 11  is a frontal elevational view of the metal shield, with a cross-sectional view of the shield being illustrated in  FIG. 13  and a right side elevational view is shown in  FIG. 14 . 
   The metal shield  30  is formed into a U-shape as viewed from the front end thereof and it includes a top surface shield portion  31  that covers a part of the top surface of the connector housing  10 . It also includes two side surface shield portions  33  that cover both of the open sides of the connector housing  10 , and each of the side shield portions  33  include spring pieces  34  formed therewith. The metal shield further includes an engagement piece  32  that, as best illustrated in  FIG. 3 , projects to the interior of the metal shield  30  and the connector housing  10 . This engagement piece is designed to interferingly contact an opposing recess  311  of a plug connector P as shown in  FIG. 16 . 
   Each of the spring pieces  34  functions to hold the opposing plug connector P in place with the receptacle connector opening  21 , when the plug connector P is inserted into the receptacle connector R. These spring pieces  34  lie in opposition to the sides of the plug connector side walls  310 . Each spring piece  34  takes the form of a plate with body portions  34   a  ( FIG. 12 ) that are formed as part of the side surface shield portions  33  and with free end portions  34   b  that extend from the body portions  34   a . The free end portions  34   b  extend on the sides of the rear surface of the connector housing along the side surface shield portions in opposition to the connector housing body portion. ( FIG. 4 .) Slots, or cutaways,  35  are preferably formed in both of the side surface shield portions  33  to engage outer projections formed on the connector housing to both hold the shield  30  in place on the connector housing, and also so that the spring pieces  34  may move freely from their associated side surface shield portions  33  to thereby act as a pair of spring engagement arms. In this regard, each of the spring pieces  34  projects slightly inwardly into the receptacle formed by the connector housing top and bottom wall portions and the sidewalls of the outer metal shell  20  along the order of a thickness of the metal blank from which the shield  30  is stamped. This inward projection is illustrated in  FIG. 11 . This projection is attained by bending the spring pieces  34  in the area of their body portions  34   a . Each of the spring pieces  34  will lie along the inner wall of the metal shield and in the connector receptacle opening  21 , into which the plug connector P is inserted. These two spring pieces  34  serve to exert a retaining pressure on the opposing plug connector P in the horizontal direction from both the left and right sides of the connector opening  21 . 
   The metal shield  30  also has an engagement piece  32  that is formed therewith and which is bent inwardly at a front end  32   a  thereof so that a free end portion  32   b  of the engagement piece  32  extends through an opening of the connector housing  10 . The engagement piece free end  32   b  also extends in opposition to the connector housing body portion  10 . ( FIG. 3 .) The engagement piece  32  extends into the interior receptacle  21  of the connector housing through an opening, or window formed in the connector housing top wall member  10   a . The free end  32  has a bent, and preferably convex portion  32   c  formed thereon having a profile that will engage with recessed, or open portions,  311  that is provided on the outer shell  310  of the plug connector P. See  FIG. 16 . This engagement piece  32  exerts a retaining force on the plug connector P in the vertical direction and along the top surface of the plug connector. As set out below, a rib portion 10 g having a profile similar to that of the portion  32   c  may be formed as part of the bottom wall member  10   b  of the connector housing  10 . ( FIG. 9 .) 
   In this embodiment, the sidewalls of the connector housing  10  are omitted (i.e., open) so that the connector housing  10  itself may be reduced both in size and in weight. The window in the top wall member also assists in reducing weight of the connector R. This permits the connector to achieve the goal of significant reduction size and in weight to the point where connectors of the present invention may be made at one-third the size of comparable conventional connectors shown in  FIG. 15 . The overall mechanical strength of the connectors of the invention is not affected because the open sides of the connector housing  10  are covered by the side surface shield portions  24  of the metal shell  20  as well as the side surfaces  33  of the metal retainer shield  30 , so that the electrical and mechanical performance of the connector is maintained. 
   The side surface portions  33  of the metal shield  30  and their associated spring pieces  34  are aligned with the open spaces between the top and bottom wall members of the connector housing so that these two spring pieces  34  extend into the receptacle opening  21  formed in the connector R so as to contact the side surfaces of the plug connector shell  310  of the opposing plug connector insertion end. Consequently, the shell  310  and the plug connector P are held in place within the receptacle connector R in a stable manner from the left and right sides thereof, without any displacement. Therefore, the electrical connection between the plug connector P and the receptacle connector R is maintained in a stable condition which makes it possible to effectively convey any transmitted electrical noise to the ground located in the circuit board by way of the receptacle shield  30  that is in contact with the metal shell  20  and its attachment legs  24 . 
   The spring pieces  34  themselves contact the outer surface of the plug connector shell  310  and serve to stabilize the frictional resistance that occurs during insertion and removal of the plug connector P. These spring pieces  34  are disposed on the right and left sides of the connector housing  10  and clamp and hold the plug shell  310  on both right and left sides thereof, and as shown in  FIG. 9 , this clamping occurs at a level at or above the level of support for the contact portions  3  of the terminals  1 . These two spring pieces enhance both the grounding aspect of the two connectors and the stability of the connector R during insertion and removal of the plug connector P therefrom. 
   Each spring piece  34  may take the form of a plate having a free end portion  34   a  extending toward the rear of the connector housing  10  and along the side surface shield portion  33 . This both simplifies the manufacturing of the connector R but also reduces its manufacturing cost in that only simple machine work, such as bending, need be performed on the spring pieces  34  in a direction close to each other (i.e., inwardly, with respect to the connector receptacle  21 ) and thus it is possible to bring the pieces  34  into reliable contact with the outer surfaces of the plug connector shell  310 . Because the spring pieces  34  are in the form of plates, it is possible to bring it into uniform contact with the outer surface of the plug connector outer shell  310 . The free end portions  34   b  of each spring piece  34  extend rearwardly along the connector housing  10  in the insertion direction of the plug connector P, and thus do not interfere with the insertion of the plug connector P. Additionally, the spring pieces  34  and the engagement piece  32  exert a retention force on the insertion plug of the plug connector P, on three of the low sides of the insertion plug, which increases the mechanical and retention stability of the connector. 
   In the embodiment described, the forming of the metal shell  20  by stamping, does not weaken the exterior frame  22  or the receptacle opening  21  that receives the plug end of the plug connector P, so that the stability of the opening  21  is enhanced. Also, because the metal shell is stamped and formed rather than drawn and formed, the manufacturing cost is reduced. Furthermore, the elimination of the connector housing sidewalls and the use of the opening for the engagement piece cooperate to reduce the overall size of the connector. The frame portion  22  is stamped as a continuous extent of metal that surrounds the opening  21  and is formed without drawn or joint portions, so it will exhibit superior mechanical strength. 
   It will be understood that according to the present invention, it is possible to provide a shielded receptacle connector that is reduced in size and is reduced in weight that is durable for repeated use in insertion and removal cycles and which effectively performs its function of transmitting electrical noise to a ground on a circuit board. 
   While the preferred embodiment of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.