Patent Publication Number: US-6666734-B2

Title: Method for producing a male terminal fitting with a tab free of sharp edges

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method for producing a male terminal fitting that has a tab. 
     2. Description of the Related Art 
     A known tab for a male terminal fitting is shown in Japanese Patent Publication No. 3-291872 and is identified by the numeral  1  in FIG. 8 herein. The tab  1  has a planar base  2  and a tapered tip  3  at the leading end of the base  2  to facilitate insertion into a cavity of a connector, a mating female terminal fitting or the like. 
     The tab  1  is formed from a metallic plate that is stamped by a press into an elongated blank or development, as shown in FIG.  9 . The development is divided into three sections along the widthwise direction to define a center section  1 A and left and right sections  1 B. The leading ends of the sections  1 A,  1 B define trapezoidal cut surfaces  4 A,  4 B that taper toward their ends. 
     The tab  1  is formed by folding the left and right sections  1 B along longitudinal fold lines and onto the upper surface of the center section  1 A. Hence the tab  1  has a thickness that is twice the thickness of the metallic plate. At this time, the cut surfaces  4 A,  4 B of the center section  1 A and the left and right sections  1 B are aligned to form the tapered trapezoidal tip  3 . 
     The tip  3  is pressed from above and below to form slanted surfaces  5  on its upper and lower surfaces and to become tapered also in side view. 
     The tip  3  of the tab  1  is stamped out of the metallic plate by the press, as described above. Thus, sharp edges  6  are formed around the cut surfaces  4 A,  4 B. As a result, the edges  6  may damage the wall surfaces of a cavity of a connector during insertion of the male terminal fitting into the cavity. The edges  6  may damage a waterproof rubber plug as the tip  3  is introduced through a hole of the rubber plug. 
     The invention was developed in view of the above problem and an object thereof is to provide a method for producing a male terminal fitting and a male terminal fitting having an improved operability. 
     SUMMARY OF THE INVENTION 
     The invention relates to a method for forming a tab of a terminal fitting so that edges at the tip of the tab are rounded or smoothed. Thus, the edges will not damage wall surfaces of a cavity in a connector during insertion of the terminal fitting into the cavity. Similarly, the edges will not damage a rubber plug as the male terminal fitting is introduced into a through hole of the plug. 
     The terminal fitting is a male terminal fitting that has a tab with a long narrow base and a tapered tip at the leading end of the base. The method comprises longitudinally folding substantially flat sections continuously provided along a widthwise direction of a metallic plate. The method then comprises providing a mold with a pressing recess that has a closed back end. The method further includes bringing the mold closer to the tab from the front of the tab and inserting the leading end of the tab into the pressing recess and striking the tip with back wall at the closed back of the pressing recess. Thus, edges of the tip are smashed or deformed and rounded. 
     Accordingly, the edges will not are damage wall surfaces of a cavity of a connector during insertion of the male terminal fitting into the cavity. Similarly, the edges will not damage a rubber plug as the male terminal fitting is introduced into a through hole of the plug. 
     Leading ends of the substantially flat sections preferably are cut to be arcuate and narrowed in plan view The method then may comprise substantially aligning the cut surfaces at the leading ends of the substantially flat sections. Accordingly, the edges are reduced and rounded better as compared to the trapezoidal tip of the prior art. 
     Preferably, the tip and at least part of the base of the tab are inserted closely into the pressing recess when the mold is struck against the tab. In particular, the mold is brought closer to the tab along the longitudinal direction of the tab. Thus, the inner circumferential walls of the pressing recess support the leading end of the tab. Accordingly, the pressing forces of the mold will not cause the tab to undergo a bending deformation. 
     Most preferably, the flat sections are formed to have slanted surfaces that are slanted in thickness direction of the metal plate. 
     The invention also is directed to a male terminal fitting that has a tab with a long narrow base and a tapered tip at the leading end of the base. The tab is formed by longitudinally folding substantially flat sections of a metallic plate continuously along a widthwise direction. The tip is arcuate in plan view, and hence narrows toward the leading end. Accordingly, the edges are reduced and rounded better as compared to the prior art trapezoidal tip. 
     The tip preferably is formed by pressing. Additionally, the arcuate cut surfaces at the leading ends of the respective flat sections preferably are substantially aligned. 
     Most preferably, the flat sections have slanted surfaces that are slanted in thickness direction of the metal plate. 
     These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description and accompanying drawings. Even though embodiments are described separately, single features thereof may be combined to additional embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a male terminal fitting according to the invention. 
     FIG. 2 is a fragmentary enlarged perspective view of a tab. 
     FIG. 3 is a plan view showing a development of the tab. 
     FIG. 4 is a perspective view showing the tab and a mold. 
     FIGS.  5 (A),  5 (B) and  5 (C) are side views in section showing a state before the mold is struck against the tab, a state where the mold is struck against the tab, and a state where the tab is withdrawn from the mold. 
     FIG. 6 is a fragmentary enlarged perspective view of an alternate tab. 
     FIG. 7 is a plan view showing a development of the tab of FIG.  6 . 
     FIG. 8 is a fragmentary enlarged perspective view of a prior art tab. 
     FIG. 9 is a plan view showing a development of the prior art tab. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A male terminal fitting according to the invention is identified by the numeral  10  in FIG.  1 . The male terminal fitting  10  is formed by stamping or cutting a single electrically conductive metallic plate into a blank or development and then successively bending and/or embossing the plate by a press. The male terminal fitting  10  is long and narrow along forward and backward directions, and has a box  11  at a central longitudinal position. A tab  12  is at a front end of the terminal fitting  10  and is connectable with an unillustrated female terminal fitting. Front and rear pairs of barrels  13 ,  14  are at the rear end of the terminal fitting  10  and the barrels  13 ,  14  in each pair extend respectively from left and right walls of the terminal fitting  10 . The front barrels  13  are configured to be crimped, bent or folded into connection with a core of a wire and the rear barrels  14  are configured to be crimped, bent or folded into connection with an insulated portion of the wire. 
     The tab  12  has a substantially flat base  15  that extends along forward and backward directions and defines a substantially constant width along its length. A tapered or rounded tip  16  is provided at the leading end of the base  15 , as shown most clearly in FIG.  2 . 
     The terminal fitting  10  is formed from a metallic plate  18  that is stamped or cut by a press. A part of the plate  18  that becomes the tab  12  has a center section  18 A and left and a right sections  18 B that are continuous with one another along the widthwise direction, as shown in FIG.  3 . The left and right sections  18 B preferably are about half as wide as the center portion  18 A. Boundaries between the center section  18 A and the left and right sections  18 B define fold lines  19  that extend longitudinally. An arcuate or converging cut surface  21 A is formed at the leading end of the center portion  18 A and is narrowed or tapered toward its end when viewed from above. Arcuate or converging cut surfaces  21 B are formed at the leading ends of the left and right sections  18 B and also are narrowed or tapered toward their ends. The cut surfaces  21 B are substantially symmetrical with respect to the fold lines  19 . 
     The left and right sections  18 B are folded along the fold lines  19  and are placed on the upper surface of the center section  18 A. Thus, the tab  12  is substantially twice as thick as the metallic plate. The bending of the left and right sections  18 B along the fold lines  19  forms rounded side surfaces  15 A along the base  15 . The cut surface  21 A of the center section  18 A and the cut surfaces  21 B of the left and right sections  18 B substantially align at the tip  16 . Consequently, the tip  16  has an arcuate or converging shape in plan view and is narrowed or tapered toward its end. 
     The tip  16  is pressed from above and below to form slanted surfaces  22  on its upper and lower surfaces and to become tapered in side view or in a sectional view along a direction normal to the plan view or along thickness direction. At this point in the forming process, sharp upper and lower edges  23  are defined around the slanted surfaces  22 . 
     The edges  23  of the tip  16  are rounded using a mold  30  shown in FIG.  4 . The mold  30  has a pressing recess  31  with an open front and a closed back wall  32 . The tip  16  of the tab  12  and parts of the base  15  adjacent the tip  16  are inserted closely into the pressing recess  31 . The back wall  32  of the pressing recess  31  has rounded recessed surfaces  32 A at portions corresponding to the edges  23  of the tip  16 , as shown in FIG.  5 (A). 
     The pressing recess  31  of the mold  30  is positioned opposed to and aligned with the front of the tab  12 , and is brought closer to the tab  12  substantially along its longitudinal direction. The tip  16  and adjacent parts of the base  15  of the tab  12  are inserted into the pressing recess  31  so that the tip  16  strikes against the base wall  32  (see FIG.  5 (B)). Thus, the edges  23  of the tip  16  are smashed or deformed by the recessed surfaces  32 A of the back wall  32 , and are deformed into rounded shapes substantially along the recessed surfaces  32 A. At this time, a pressing force from the mold  30  acts on the male terminal fitting  10 . However, the pressing force acts along the longitudinal direction of the male terminal fitting  10 , and therefore is unlikely to bend the male terminal fitting  10 . Further, the tip  16  and adjacent parts of the base  15  are accommodated closely in the pressing recess  31 . Consequently, the leading end of the tab  12  is supported by the inner surfaces of the pressing recess  31 , and pressing forces from the mold  30  will not bend the tab  12 . 
     Finally, the mold  30  is moved back to withdraw the tab  12  from the pressing recess  31 . As a result, the edges  23  of the tip  16  of the male terminal fitting  10  are smashed or deformed and rounded, as shown in FIG.  5 (C). 
     As described above, the edges  23  are rounded by inserting the tab  12  into the pressing recess  31  and striking the tip  16  against the back wall  32 . Thus, the edges  23  will not damage surfaces of a cavity of a connector as the male terminal fitting  10  is inserted into the cavity or from damaging a rubber plug as the male terminal fitting  10  is inserted in a through hole of the plug. 
     The tip  16  and adjacent parts of the base  15  are inserted closely into the pressing recess  31  when the mold  30  is struck against the tab  12  and the inner circumferential walls of the pressing recess  31  support the leading end of the tab  12 . Thus, the tab  12  is prevented from undergoing a bending deformation caused by the pressing force from the mold  30 . 
     The tip  16 , in plan view, has an arcuate shape that is narrowed toward its end. Thus, the edges are reduced and are rounded better as compared to the trapezoidal tip of the prior art. 
     FIG. 6 shows an alternate tab  40  that includes a base  41  in the form of a flat plate and a tapered tip  42 . The tab  40  is formed from a metallic plate  43  that is stamped by a press into a blank or development as shown in FIG.  7 . This plate  43  has left and right sections  45  at the opposite sides of a fold line  44  located in the widthwise center. Arcuate cut surfaces  46 , which are narrowed to their ends in plan view, are formed at the leading ends of the left and right sections  45 . The left and right sections  45  are folded along the fold line  44  and are placed one over the other so that the cut surfaces  46  align to form the arcuate tip  42 . Upper and lower slanted surfaces  47  are formed by pressing the tip  42  from above and below. Thereafter, in the same manner as the foregoing embodiment, a mold (not shown) is brought closer to the tab  40  from the front of the tab  40 . Thus, the leading end of the tab  40  is inserted into the pressing recess in the mold and the tip  42  strikes the closed back wall to smash and round edges  48  on the tip  42 . The invention is not limited to the above described and illustrated embodiment. For example, the following embodiment is also embraced by the technical scope of the present invention as defined by the claims. Beside the following embodiment, various changes can be made without departing from the scope and spirit of the present invention as defined by the claims.