Abstract:
A female terminal fitting ( 10 ) has a tubular main portion ( 11 ) with first and second opposed resilient pieces ( 21, 24 ) formed therein. The second resilient piece ( 24 ) has an extending piece ( 25 ), a support ( 26 ) and a pressing piece ( 27 ). The support ( 26 ) contacts the inner surface of the main portion ( 11 ) and the pressing piece ( 27 ) extends from the support ( 26 ) to hold the first resilient piece ( 21 ) in a pre-loaded state. A tab ( 60 ) is inserted between the extending piece ( 25 ) and the first resilient piece ( 21 ) to incline the pressing piece ( 27 ) about the support ( 26 ) and to release the pre-loaded state. The extending piece ( 25 ) resiliently deforms about the support ( 26 ) and toward the tab ( 60 ) as the pressing piece ( 27 ) is inclined. Thus, the tab ( 60 ) is held resiliently between the extending piece ( 25 ) and the first resilient piece ( 21 ). With this arrangement, the tab ( 60 ) may be inserted at low frictional force but at complete insertion is held tightly be increased frictional force.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a female terminal fitting. 
     2. Description of the Related Art 
     U.S. Pat. No. 7,513,806 discloses a female terminal fitting that has a tubular main portion for receiving a tab of a male terminal fitting. A barrel is behind the main portion and is configured to be connected with an end of a wire. A resilient contact piece is formed in the main portion, and a wall of the main portion is hammered to project at a position facing the resilient contact piece to define a pedestal-like receiving portion. The resilient contact piece deforms resiliently when the tab is inserted into the main portion and tightly holds the tab against the receiving portion for electrically connecting the two terminal fittings. 
     The above-described female terminal fitting strongly presses the tab against the receiving portion in the process of inserting the tab into the main portion due to a spring force from the resilient contact piece. Thus, large frictional resistance is produced between the receiving portion and the tab as the spring force of the resilient contact piece increases, thereby causing a problem of deteriorating operability. In contrast, operability is improved if the spring force of the resilient contact piece decreases, but a sufficient contact pressure to the tab cannot be ensured. 
     The invention was developed in view of the above situation and an object thereof is to ensure a sufficient contact pressure to a tab while improving operability while inserting the tab. 
     SUMMARY OF THE INVENTION 
     The invention relates to a female terminal fitting with a main portion for receiving a tab of a mating side. First and second resiliently deformable pieces are formed in the main portion and face one another in directions so that the first and second resiliently deformable pieces can deform toward and away from one another. The second resilient piece includes an extending piece, a support and a pressing piece. The extending piece extends substantially in an inserting direction of the tab from an opening end of a wall of the main portion. The support is held in contact with the inner surface of the wall at an extending end of the extending piece. The pressing piece extends from the support toward the first resilient piece and an extending end portion of the pressing piece holds the first resilient piece in a pre-loaded state. 
     The tab can be inserted between the extending piece and the first resilient piece. Thus, a leading end of the tab pushes and inclines the pressing piece and releases the pre-loaded state of the first resilient piece. Additionally, the extending piece deforms resiliently about the support and toward the first resilient piece as the pressing piece is pushed and inclined. Thus, the tab is held resiliently between the extending piece and the first resilient piece. 
     The first resilient piece remains in the pre-loaded state during the insertion of the tab until the pressing piece is pushed and inclined. Thus, the first resilient piece does not exert a large spring force on the tab and frictional resistance between the first resilient piece and the extending piece is low. Therefore, the tab can be inserted easily. 
     The leading end of the tab pushes and inclines the pressing piece to release the pre-loaded state of the first resilient piece. The extending piece deforms resiliently about the support and toward the first resilient piece as the pressing piece inclines. Thus, the tab is held resiliently and tightly between the extending piece and the first resilient piece. Accordingly, a high contact pressure is ensured between the first resilient piece, the extending piece and the tab. 
     The first resilient piece preferably extends substantially in the inserting direction of the tab from an opening end of wall of the main portion that faces the wall from which the second resilient piece extends. 
     The pressing piece preferably presses an extending end portion of the first resilient piece. 
     The first resilient piece preferably extends in the inserting direction of the tab from an opening end of first wall of the main portion and the second resilient piece preferably extends from a second wall, which faces the first wall. The pressing piece presses an extending end portion of the first resilient piece. Thus, the pressing piece need not exert a particularly large force and the first resilient piece released from the pre-loaded state can return smoothly to its original shape. 
     The extending end portion of the first resilient piece preferably is held tightly between the pressing piece and the inner surface of the first wall in the pre-loaded state. Thus, loose movements of the first resilient piece are restricted in the pre-loaded state. 
     The tab may be thicker than an opening dimension of an insertion path for the tab between the extending piece and the first resilient piece when the first resilient piece is in the pre-loaded state. Thus, the tab slides in contact with the first resilient piece and the extending piece during insertion of the tab into the insertion path. This sliding contact removes a layer, such as an oxide layer, formed on the surface of the first resilient piece, the extending piece or the tab. 
     Alternatively, the tab may be thinner than an opening dimension of an insertion path for the tab formed between the extending piece and the first resilient piece when the first resilient piece is in the pre-loaded state is set to be larger than the thickness of the tab. Thus, substantially no frictional resistance will be produced between the first resilient piece, the extending piece and the tab, and a work load during insertion of the tab into the insertion path is mitigated. 
     These and other objects, features and advantages of the invention will become more apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of an essential part of a female terminal fitting according to one embodiment of the invention. 
         FIG. 2  is a sectional view of an essential part showing a state where a tab is inserted in a main portion. 
         FIG. 3  is a sectional view along A-A of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A female terminal fitting  10  according to the invention is identified by the numeral  10  in  FIGS. 1 to 3 . The female terminal fitting  10  is formed integrally or unitarily by applying bending, folding and/or embossing and other processings to an electrically conductive metal plate and includes a main portion  11 , an unillustrated wire connection portion behind the main portion  11  and a coupling  12  between the wire connection portion and the main portion  11 . 
     The wire connection portion is crimped or otherwise connected to an end of an unillustrated wire. A base plate  13  extends substantially in forward and backward directions FBD along the main portion  11 , the coupling  12  and the wire connecting portion. The coupling  12  includes the base plate  13  and two coupling side plates  14  projecting up from opposite lateral sides of the base plate  13 . The base plate  13  of the coupling  12  is hammered from below to project in and up to form a raised portion  15 . The raised portion  15  is substantially a pedestal with a substantially horizontal flat upper surface  16 . 
     The main portion  11  is a substantially rectangular tube and has the base plate  13 , two side plates  17  projecting up from opposite lateral sides of the base plate  13  and a facing plate  18  bent at the upper end of one side plate  17  to extend toward the upper end of the other side plate  17 , as shown in  FIG. 3 . The facing plate  18  is substantially parallel to the base plate  13 . A tab insertion opening  19  is formed at the front of the main portion  11  and can receive a tab  60  of a mating side inserted in an inserting direction ID from the front. Lower portions of the rear ends of the side plates  17  are connected unitarily to the coupling side plates  14 . 
     A substantially strip-shaped first resilient piece  21  is formed in the main portion  11  and is cantilevered rearward from the front end of the base plate  13  to extend substantially in forward and backward directions FBD. The first resilient piece  21  is resiliently deformable up and down in a direction intersecting the inserting direction ID with the front opening end of the base plate  13  as a support. The first resilient piece  21  is formed from a tongue that initially extends forward from the front end of the base plate  13 . The tongue then is bent back in such a manner to define a substantially mountain shape for the first resilient piece  21 . A contact  22  is defined at the peak of the mountain-shaped first resilient piece  21  and can be brought into contact with the tab  60 . Slits  23  are formed between opposite sides of a front end of the base plate  13  and the side plates  17 . Thus, the base end of the first resilient piece  21  is retracted slightly back from the front end of the main portion  11 . A rear extending end of the first resilient piece  21  is supported on and in contact with the flat surface  16  of the raised portion  15  from above. 
     A substantially strip-shaped second resilient piece  24  is cantilevered rearward in the main portion  11  and extends in substantially forward and backward directions FBD at a position substantially facing the first resilient piece  21 . 
     The second resilient piece  24  includes an extending piece  25 , a support  26  and a pressing piece  27 . The extending piece  25  extends back from the front end of the facing plate  18 . The support  26  is at the rear end of the extending piece  25  and is held in contact with the inner surface of the facing plate  18 . The pressing piece  27  extends obliquely down to the back from the support  26  toward the first resilient piece  21 . The extending piece  25  and the support  26  are wide strips similar to the first resilient piece  21 . On the other hand, the pressing piece  27  is a narrow strip extending from a widthwise intermediate part of the rear end of the extending piece  25  (see  FIG. 3 ). 
     A front end of the extending piece  25  closely contacts the inner surface of the facing plate  18 . A part of the extending piece  25  rearward of the front end is spaced from the inner surface of the facing plate  18  and includes a straight portion  28  that is substantially parallel with the inner surface of the facing plate  18 . The straight portion  28  of the extending piece  25  faces the contact portion  22  of the first resilient piece  21  and extends forward and backward substantially parallel to the inserting direction ID. 
     The extending piece  25  extends obliquely up and back from the rear end of the straight portion  28  and the support  26  is formed at the upper and rearward end of this oblique rear part of the extending piece  25 . The front part of the pressing piece  27  extends obliquely down back from the support  26 . Thus, the support  26  is defined at a mountain-shaped peak where the oblique rear part of the extending piece  25  meets the oblique front part of the pressing piece  27 . The support  26  is constantly in contact with the inner surface of the facing plate  18 . 
     The rear end of the pressing piece  27  is bent obliquely up and back to define a bent-up portion  31 . The convex lower surface defined by the bent-up portion  31  of the pressing piece  27  is biased into contact with the rear end portion of the first resilient piece  21  from above. Thus, the rear end portion of the first resilient piece  21  is held resiliently and tightly in a pressing position PP between the convex lower surface at the bent-up portion  31  and the raised portion  15  of the base plate  13 , as shown in  FIG. 1 . The first resilient piece  21  pressed by the pressing piece  27  is deformed resiliently with the front end of the base plate  13  as a support and is held in this pre-loaded resiliently deformed state. An insertion path  35  for the tab  60  is formed between the extending piece  25  and the first resilient piece  21 . A distance between the straight portion  28  of the extending piece  25  and the contact portion  22  of the first resilient piece  21  in a height direction defines an opening dimension of the insertion path  35  and is slightly smaller than the thickness of the tab  60  when the pressing piece  27  is at the pressing position PP. 
     The pressing piece  27  includes a touching portion  34  aligned with the insertion path  35 . A leading end of the tab  60  will contact the touching portion  34  after sufficient insertion of the tab  60  into the main portion  11  along the insertion path  35 . Thus, the tab  60  pushes the pressing piece  27  and pivots the pressing piece  27  back and up about the support  26 . As a result, the convex lower surface of the pressing piece  27  will no longer bias the first resilient piece  21  against the raised portion  15  of the base plate  13 . Accordingly, the pressing piece  27  is displaced from the pressing position PP of  FIG. 1  to a retracted position RP (see  FIG. 2 ) where the state of pressing the first resilient piece  21  is released. 
     The tab  60  is inserted into the main portion  11  of the female terminal fitting  10  along the inserting direction ID and from the front as an unillustrated connector that accommodates the female terminal fitting  10  is connected. More particularly, the tab  60  is inserted along forward and backward directions FBD through the tab insertion opening  19 . A depth of insertion increases while the tab  60  slides in contact with the extending piece  25  and the first resilient piece  21 . The pressing piece  27  is at the pressing position PP and the first resilient piece  21  is kept in the pre-loaded state as the leading end of the tab  60  moves along the insertion path  35 . Thus, the tab  60  is not subjected to a large spring force from the first resilient piece  21  and there is low frictional resistance between the tab  60  and both the first resilient piece  21  and the extending piece  25 . 
     The leading end of the tab  60  contacts with the touching portion  34  immediately before the tab  60  is inserted completely and hence the tab  60  inclines the pressing piece  27  back to the retracted position RP. This movement of the pressing piece  27  releases the first resilient piece  21  from the pre-loaded state. As a result, the first resilient piece  21  returns resiliently up toward the extending piece  25  in a pivoting movement about the front end of the base plate  13 . Therefore, the first resilient piece  21  gives a spring force to the tab  60  from below. 
     The extending piece  25  is displaced down toward the first resilient piece  21  in a pivoting movement about the support  26  as the pressing piece  27  moves to the retracted position RP. Therefore, the straight portion  28  of the extending piece  25  is held in contact with the upper surface of the tab  60 . A lever action is generated by an applied force at the touching portion  34 , a fulcrum at the support  26  and a resulting force at the straight portion  28  to press the tab  60  down. 
     The tab  60  that has been inserted into the main portion  11  is held in close resilient contact with the extending piece  25  and in close resilient contact with the first resilient piece  21  at its lower side. As a result, the tab  60  is held with an appropriate contact pressure from opposite sides between the extending piece  25  and the first resilient piece  21 . 
     As described above, the first resilient piece  21  is kept in the pre-loaded state while the tab  60  is being inserted. Thus, the tab  60  is not subjected to a large spring force from the first resilient piece  21  and no large frictional resistance is produced between the first resilient piece  21  and the extending piece  25 . Therefore, the tab  60  is inserted easily. 
     The pre-loaded state of the first resilient piece  21  is released as the leading end of the tab  60  pushes and inclines the pressing piece  27 . The extending piece  25  is deformed resiliently toward the first resilient piece  21  about the support  26  as the pressing piece  27  is inclined. Thus, the tab  60  is held resiliently and tightly between the extending piece  25  and the first resilient piece  21  with a sufficient contact pressure. 
     The pressing piece  27  presses the first resilient piece  21  at a rear end distant from the front support of the first resilient piece  21 . Thus, the pressing piece  27  need not exert a particularly large force and the first resilient piece  21  released from the pre-loaded state returns smoothly towards its original shape. 
     Furthermore, the rear end portion of the first resilient piece  21  is held tightly between the pressing piece  27  and the flat surface  16  of the raised portion  15  of the base plate  13  in the pre-loaded state. Thus, loose movements of the first resilient piece  21  in the pre-loaded state are restricted. In this case, the spring force of the first resilient piece  21  and the length of the pressing piece  27  are set at appropriate values by adjusting the height of the raised portion  15 . 
     The tab  60  slides in contact with the first resilient piece  21  and the extending piece  25  during the insertion of the tab  60  along the insertion path  35 . Thus, a layer, such as an oxide layer, formed on the surface of the first resilient piece  21 , the extending piece  25  or the tab  60  can be removed by wiping or scratching. 
     The invention is not limited to the above described and illustrated embodiment. For example, the following embodiments are also included in the technical scope of the present invention. 
     Contrary to the above embodiment, the opening dimension of the insertion path between the extending piece and the first resilient piece may exceed the thickness of the tab when the pressing piece is at the pressing position and the first resilient piece is in the pre-loaded state. Thus, substantially no frictional resistance is produced between the first resilient piece, the extending piece and the tab, and a work load to insert the tab into the insertion path can be mitigated more. 
     The first resilient piece may extend forward from the rear end of the main portion and may be resiliently deformable with the rear end as a support. 
     The raised portion may be formed in the main portion or may be formed to extend from the main portion to the coupling. 
     The pressing piece may partly have the same width as the extending piece.