Patent Publication Number: US-7722413-B2

Title: Electrical connector with reduced press-in resistance for terminals

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a connector. 
     2. Description of the Related Art 
     Japanese Unexamined Patent Publication No. 2006-19228 discloses a connector with a housing made of synthetic resin. The housing has a retaining wall and press-in holes penetrate the retaining wall. The connector also includes tab-shaped terminals that are pressed into the press-in holes. Each tab-shaped terminal has opposite front and rear ends. A long narrow tab-shaped contact is formed at the front end and a press-in portion that is wider than the press-in hole is continuous with the rear end of the tab-shaped contact. The terminal is pressed into the press-in hole with the tab-shaped contact in the lead. The press-in portion then deforms and widens the inner wall of the press-in hole in a press-in process. 
     The deformation of the inner wall of the press-in hole creates a reaction force and produces a press-in resistance. The press-in hole has a constant width along its length in the above-described conventional connector. As a result, a constant press-in resistance continues to act from the start to the end of the press-in process. The press-in resistance could be decreased by decreasing a difference in width between the press-in hole and the press-in portion. However, such a redesign also would provide an unacceptable reduction in the force for retaining the tab-shaped terminal in the press-in hole. Therefore, it has been conventionally impossible to avoid the large press-in resistance from the start to the end of the press-in process. 
     The invention was developed in view of the above situation and an object thereof is to reduce press-in resistance without reducing a force for retaining a terminal. 
     SUMMARY OF THE INVENTION 
     The invention relates to a connector with a housing made of synthetic resin and formed with at least one press-in hole extending substantially in forward and backward directions. The connector also includes at least one terminal with opposite front and rear ends. A contact is formed at the front end of the terminal and a press-in portion is continuous with the rear end of the contact. The press-in portion is wider than the press-in hole. The terminal is retained in the housing by pressing the press-in portion into the press-in hole in a press-in direction. The press-in hole is formed to be gradually wider from the front end toward the rear end thereof. Thus, a large dimensional difference between the width of the press-in hole and the width of the press-in portion is ensured at a front end portion of the press-in hole for reliably retaining the terminal in the housing. On the other hand, the dimensional difference between the width of the press-in hole and the width of the press-in portion is small at a rear end portion of the press-in hole for reducing the press-in resistance at an initial stage of a press-in process. 
     A positioning hole preferably is formed in the housing at the front end of the press-in hole. The positioning hole receives to the contact and positions the contact at a proper position in a width direction. 
     A front part of the press-in portion preferably has a trapezoidal shape oriented to be wider toward the back. 
     A maximum width of the rear end of the press-in hole preferably is less than the width of the trapezoidal front end. 
     The inclined side edges of the trapezoidal part contact the opening edge of the press-in hole at the start of the press-in process. Thus, press-in resistance is reduced by the inclination of these inclined side edges. 
     A biting portion preferably is defined at the front end of the press-in portion. Lateral edges of the biting portion are inclined to narrow the spacing therebetween towards the front and with respect to the press-in direction. 
     A receiving portion preferably is defined at the front end of the press-in hole. Opposite lateral surfaces of the receiving are inclined to narrow the spacing therebetween with respect to the press-in direction. 
     An angle formed by the opposite lateral edges of the biting portion preferably is smaller than an angle formed by the opposite lateral inner surfaces of the receiving portion. As a result, the biting portion bites in the receiving portion in the state where the press-in process is completed and the tab-shaped terminal is retained reliably by this biting action. 
     Triangular or pointed projections preferably are formed on lateral edges of the press-in portion at positions spaced apart in a press-in direction. The projections of the pressed-in terminal bite in the inner side surfaces of the press-in hole to retain the terminal reliably. 
     The projections preferably are formed so that lines that connect the projecting ends of the projections along the lateral edges of the press-in portion are inclined to narrow the spacing therebetween toward the front. 
     The press-in portion, including the projections, preferably is tapered towards the front. Thus, press-in resistance is reduced at the initial stage of the press-in process. 
     An angle defined by the lines that connect the projecting ends of the projections preferably is larger than an angle defined by the opposite lateral inner surfaces of the press-in hole. 
     An angle of inclination of the slanted edges of first projections with respect to the press-in direction preferably is smaller than angles of inclination of the slanted edges of the other projections and preferably is in the range of about 5° to about 20°, more preferably about 10°. 
     Opposite lateral inner surfaces in a press-in area of the press-in hole behind the receiving portion preferably are inclined to widen the spacing gradually from the front end towards the rear end. An angle defined by the opposite lateral inner surfaces in this press-in area is smaller than the angle formed by the inner side surfaces of the receiving portion, and preferably is in the range of about 1° to about 5°, more preferably about 2°. 
     Front ends of the opposite inner side surfaces of the press-in area preferably are substantially continuous with and at an obtuse angle to the rear ends of the inner side surfaces of the receiving portion. Rear ends of the opposite inner side surfaces of the press-in area preferably are substantially continuous with and at an obtuse angle in the range of about 70° to about 90°, more preferably about 80°, to the front surface of a rear recess of the housing arranged behind the press-in hole. 
     The housing preferably comprises at least one rear recess arranged behind the press-in hole. A front surface of the rear recess preferably is a substantially flat surface arranged at an angle to the press-in direction. A maximum width in the press-in hole preferably is smaller than the minimum width of the rear recess. 
     The terminal preferably includes a front-stop that contacts a portion of the housing when the terminal reaches a proper press-in position to stop the press-in operation of the terminal is prevented. 
     These and other features of the invention will become more apparent upon reading the following detailed description of preferred embodiments and accompanying drawings. Even though embodiments are described separately, features may be combined with additional embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a horizontal section of a housing according to one embodiment. 
         FIG. 2  is a front view of the housing. 
         FIG. 3  is a rear view of the housing. 
         FIG. 4  is a plan view of a tab-shaped terminal. 
         FIG. 5  is a horizontal section showing a state where a press-in process of the tab-shaped terminal is started. 
         FIG. 6  is a horizontal section showing an intermediate state of the press-in process of the tab-shaped terminal. 
         FIG. 7  is a horizontal section showing a state where the tab-shaped terminal is being pressed in. 
         FIG. 8  is a vertical section showing a state where the tab-shaped terminal is being pressed in. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A connector in accordance with the invention is described with reference to  FIGS. 1 to 8 . The connector includes a housing identified generally by the numeral  10  and tab-shaped terminals  20 . The housing  10  is made e.g. of synthetic resin and includes a retaining wall  11  with opposite front and rear surfaces  11 F and  11 R. Retaining holes  12  penetrate the retaining wall from the front surface  11 F to the rear surface  11 R in forward and backward directions FBD and substantially parallel to a connecting direction CD with a mating connector. Each retaining hole  12  has a front recess  13  that opens in the front surface  11 F of the retaining wall  11 , a rear recess  14  that opens in the rear surface  11 R of the retaining wall  11 , a positioning hole  15  that extends back from the back end surface of the front recess  13 , and a press-in hole  16  that extends in forward and backward directions FBD from the back end surface of the positioning hole  15  to the front end surface of the rear recess  14 . The retaining hole  12  is substantially laterally and vertically symmetrical with respect to a line parallel to forward and backward directions FBD. 
     A cross-sectional shape of the front recess  13  at a right angle to a press-in direction ID of the tab-shaped terminal  20  into the retaining hole  12  is substantially square. The positioning hole  15  has a mating substantially square cross-sectional shape substantially concentric with the front recess  13 , but smaller than the front recess  13 . The rear recess  14  has a wide substantially rectangular cross-sectional shape and the inner surfaces of the rear recess are slanted to widen the rear recess  14  towards the back. A minimum vertical dimension of the rear recess  14  is at the front end of the rear recess  14  and is substantially the same as the vertical dimension of the positioning hole  15 . A minimum lateral dimension of the rear recess  14  also is at the front end of the rear recess  14  and is larger than the minimum lateral dimension of the positioning hole  15 . 
     The press-in hole  16  has a wide substantially rectangular cross-section with a vertical dimension that is substantially equal to the vertical dimension of the positioning hole  15 . Upper and lower surfaces of the press-in hole  16  are substantially continuous and flush with upper and lower surfaces of the positioning hole  15 . A receiving portion  17  is formed at the front end of the press-in hole  16  and has opposite left and right inner surfaces that are inclined to gradually narrow the spacing towards the front. An angle θa formed by the opposite left and right inner surfaces of the receiving portion  17  is close to 90° (e.g. in the range of about 70° to 90°, preferably about 80°). The front ends of the opposite left and right inner surfaces of the receiving portion  17  are substantially continuous with and at an obtuse angle to the rear ends of the inner side surfaces of the positioning hole  15 . 
     A press-in area  18  is defined in the press-in hole  16  behind the receiving portion  17 . Opposite left and right inner surfaces of the press-in area  18  are inclined to gradually widen the spacing from the front end towards the rear end. An angle θb formed by the opposite left and right inner surfaces in the press-in area  18  is smaller than the angle θa formed by the inner side surfaces of the receiving portion  17  and is in the range of about 1° to about 5°, more preferably about 2°. The front ends of the opposite inner side surfaces of the press-in area  18  are substantially continuous with and at an obtuse angle to the rear ends of the inner side surfaces of the receiving portion  17 . The rear ends of the opposite inner side surfaces of the press-in area  18  are substantially continuous with and at an obtuse angle close to 90° (e.g. in the range of about 70° to 90°, preferably about 80°) to the front surface of the rear recess  14 . The front surface of the rear recess  14  defines a stopper  19  that is substantially flat and substantially normal to the press-in direction ID (forward and backward directions FBD) of the tab-shaped terminal  20  into the retaining hole  12 . A width Wa at the rear end of the press-in area  18  (i.e. maximum width in the press-in hole  16 ) is smaller than the minimum width of the rear recess  14 . 
     Each tab-shaped terminal  20  is obtained by punching, stamping or pressing a conductive (preferably metal) plate material into a specified shape and includes a press-in portion  21 . A tab-shaped contact  22  extends forward from the front end of the press-in portion  21 , a front-stop  23  extends back from the rear end of the press-in portion  21  and a board connecting portion  24  extends back from the rear end of the front-stop  23 . The tab-shaped terminal  20  is laterally symmetrical with respect to a line extending in forward and backward directions FBD substantially parallel to the press-in direction ID into the retaining hole  12 . Additionally, the tab-shaped terminal  20  is vertically symmetrical in a state where the board connecting portion  24  is not bent. The press-in portion  21 , the tab-shaped contact  22  and the front-stop  23  have upper and lower surfaces substantially continuous and flush with each other and have the same thickness. 
     A cross-sectional shape of the tab-shaped contact  22  at a right angle to the press-in direction is square and the vertical and lateral dimensions of the tab-shaped contact  22  are equal to or slightly smaller than the vertical and lateral dimensions of the positioning hole  15 . The front-stop  23  is rectangular and the front end edge of the front stop is normal to the press-in direction. Although not shown, the board connecting portion  24  has a known shape and can be bent in an L-shape and connected with a circuit board or other electric/electronic device (not shown) while being inserted through a through hole of the circuit board. 
     The vertical dimension of the press-in portion  21  is substantially equal to the vertical dimension of the tab-shaped contact  22 . The lateral dimension of the press-in portion  21  is larger than the lateral dimension of the tab-shaped contact  22  and smaller than the lateral dimension of the front-stop  23 . First to third substantially triangular projections  25 A,  25 B and  25 C are formed on each of the opposite left and right edges of the press-in portion  21  and are spaced apart in the press-in direction ID. The projections  25 A,  25 B and  25 C have slanted edges  26 A,  26 B and  26 C inclined to the press-in direction ID and locking edges  27 A,  27 B and  27 C that face substantially rearward. 
     As shown in  FIG. 4 , an angle of inclination θc of the slanted edges  26 A of the first projections  25 A with respect to the press-in direction ID is smaller than angles of inclination θd, θe of the slanted edges  26 B,  26 C of the second and/or third projections  25 B,  25 C with respect to the press-in direction ID and preferably is in the range of about 5° to about 20°, more preferably about 10°. Further, the angle of inclination θd of the slanted edges  26 B of the second projections  25 B is substantially equal to the angle of inclination θe of the slanted edges  26 C of the third projections  25 C. 
     Angles of the locking edges  27 A,  27 B and  27 C of the respective projections  25 A,  25 B and  25 C with respect to the press-in direction ID are different from each other. The locking edges  27 A of the first or front projections  25 A are at an angle of about 90° to the slanted edges  26 A. An angle between the locking edges  27 B and the slanted edges  26 B of the second or middle projections  25 B is smaller than the corresponding angle of the first projections  25 A. An angle between the locking edges  27 C and the slanted edges  26 C of the third or rearmost projections  25 C is smallest. Thus, the angular orientations of the slanted edges with respect to the insertion direction ID gradually decrease from the front slanted edge towards the back slanted edge. The locking edges  27 C of the third projections  25 C are closest to a right angle to the press-in direction. In other words, the angular orientations of the locking edges with respect to the insertion direction ID gradually increase from the front towards the rear as seen with respect to the insertion direction ID. 
     As shown in  FIG. 5 , lines connecting projecting ends of the three pairs of projections  25 A,  25 B and  25 C along the opposite left and right edges of the press-in portion  21  are inclined with respect to the inserting direction so as to approach a longitudinal middle line LML of the press-in portion  21  and so as to narrow the spacing between the opposite lines towards the front. An angle θf defined by two lines connecting the projecting ends of the projections  25 A,  25 B and  25 C exceeds the angle θb formed by the opposite left and right inner surfaces in the press-in area  18  of the press-in hole  16 . 
     A trapezoidal biting portion  28  is formed by the pair of first projections  25 A at the front end of the press-in portion  21 , and a maximum width Wb of the biting portion  28  between the projecting ends of the first projections  25 A exceeds the maximum width Wa at the rear end of the press-in hole  16 . An angle 2×θc formed by the slanted edges  26 A of the biting portion  28  is smaller than the angle θa formed by the opposite left and right surfaces of the receiving portion  17 . The front ends of the slanted edges  26 A of the biting portion  28  are substantially continuous with and at an obtuse angle to the lateral edges of the rear end of the tab-shaped contact  22 . 
     The tab-shaped terminal  20  is inserted into the retaining hole  12  from behind and with the tab-shaped contact  22  in the lead. The tab-shaped contact  22  is through the press-in hole  16  and into fit into the positioning hole  15 . Thus, the tab-shaped contact  22  cannot make relative movements in the vertical and/or lateral directions. The press-in  21  is behind the retaining hole  12  when the tab-shaped contact  22  starts being fit into the positioning hole  15 . 
     If the insertion of the tab-shaped terminal  20  is continued in this state, the slanted edges  26 A of the opposite left and right first projections  25 A of the trapezoidal biting portion  28  of the press-in portion  21  contact the opening edge at the rear end of the press-in area  18  with the tab-shaped contact  22  fit in the positioning hole  15 , as shown in  FIG. 5 . This contact of the first projections  25 A corrects the posture of the tab-shaped terminal  20  in the lateral direction to substantially face in the correct press-in direction ID. A pressing force then is applied to the tab-shaped terminal  20  to press the press-in portion  21  into the press-in hole  16 . In the press-in process, as shown in  FIG. 6 , the first projections  25 A move forward in the press-in hole  16  while deforming the opposite left and right inner walls of the press-in area  18  to widen the press-in area  18 . Subsequently, the second projections  25 B enter the press-in hole  16  and move farther forward while deforming the inner side surfaces of the press-in area  18  to widen the press-in area  18 . The third projections  25 C similarly are pressed in while deforming the inner side surfaces of the press-in area  18  to widen the press-in area  18 . 
     When the tab-shaped terminal  20  reaches a proper press-in position, the front-stop  23  contact the stopper  19  at the back end surface of the rear recess  14 , as shown in  FIG. 7  to prevent any further press-in of the tab-shaped terminal  20  and the projections  25 A,  25 B and  25 C bite in the inner walls of the press-in hole  16  to prevent a returning movement of the tab-shaped terminal  20 . Further, the front end of the biting portion  28  bites in the inner side surfaces of the front end portion of the receiving portion  17  and the opening edge at the rear end of the positioning hole  15 . 
     As described above, the press-in hole  16  is tapered to be gradually wider from the front end towards the rear end. Thus, a large dimensional difference between the width of the press-in hole  16  and that of the press-in portion  21  is ensured at the front end portion of the press-in hole  16 , so that that the tab-shaped terminal  20  is retained reliably in the housing  10 . On the other hand, the dimensional difference between the widths of the press-in hole  16  and the press-in portion  21  is small at the rear end of the press-in hole  16  and press-in resistance at an initial stage of the press-in process can be reduced. 
     The tab-shaped contact portion  22  is positioned in the width direction by the positioning hole  15 . Thus, the tab-shaped terminal  20  is mounted at a correct position in the housing  10 . 
     Further, the biting portion  28  at the front of the press-in portion  21  has a diverging shape that widens towards the back. The maximum width Wa at the rear of the press-in hole  16  is smaller than the width Wb of the diverging biting portion  28 . Thus, the slanted edges  26 A of the biting portion  28  contact the opening edge of the press-in hole  16  at the start of the press-in process, and press-in resistance is reduced by the inclination of the slanted edges  26 A. 
     The biting portion  28  at the front end of the press-in portion  21  has opposite left and right edges inclined to narrow the spacing toward the front. The receiving portion  17  at the front end of the press-in hole  16  has left and right inner surfaces inclined with respect to the inserting direction ID to narrow the spacing towards the front. The angle formed by the opposite left and right slanted edges  26 A of the biting portion  28  is smaller than the angle formed by the opposite left and right inner surfaces of the receiving portion  17 . Accordingly, the biting portion  28  bites in and engages the receiving portion  17  after the press-in process is completed. Therefore the tab-shaped terminal  20  is retained more reliably by this biting action. 
     The three pairs of substantially triangular projections  25 A,  25 B and  25 C are formed on opposite left and right edges of the press-in portion  21 . The projections  25 A,  25 B and  25 C are spaced apart in the press-in direction ID and bite the inner side surfaces of the press-in hole  16  for reliably retaining the pressed-in tab-shaped terminal  20 . 
     The lines connecting the projecting ends of the projections  25 A,  25 B and  25 C of the three pairs of projections  25 A,  25 B and  25 C along the opposite left and right edges of the press-in portion  21  are inclined with respect to the inserting direction ID to preferably narrow the spacing therebetween towards the front. Additionally, the press-in portion  21  including the projections  25 A,  25 B and  25 C is tapered towards the front end. Therefore, press-in resistance at the initial stage of the press-in process is reduced. 
     The invention is not limited to the above described embodiment, and the following embodiments also are embraced by the invention. 
     The housing need not have the positioning holes, and the front ends of the press-in holes may be located in the front surface of the housing. 
     The front end of the press-in portion may be a rectangle whose front end edge is normal to the press-in direction instead of being trapezoidal. 
     The maximum width of the rear end of the press-in hole may be larger than the width of the trapezoidal part. 
     The angle formed by left and right edges of the biting portion may exceed the angle formed by left and right inner surfaces of the receiving portion. 
     The opposite left and right edges of the press-in portion may be straight instead of having the projections. 
     The press-in hole and the positioning hole may be connected by a step without the tapered receiving portion at the front end of the press-in hole. 
     More or fewer than three pairs of projections may be provided.