Patent Publication Number: US-6217387-B1

Title: Terminal fitting for a wedge-base bulb and a bulb socket comprising such a terminal fitting

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a terminal fitting for a wedge-base bulb (base-free bulb) and to a bulb socket comprising such a terminal fitting. 
     2. Description of the Prior Art 
     A known terminal fitting for a wedge-base bulb is disclosed in Japanese Unexamined Utility Model Publication No. 2(HEI)-150688. This terminal fitting  1  is, as shown in FIG. 15, provided with a pair of holding pieces  2  formed by bending opposite sides of a metal sheet at right angles, and a tab  3  formed by bending a bottom end of one holding piece  2 R to have a steplike shape. A stepped portion  3 A of the tab  3  is formed with a tab side portion  4  extending toward the other holding piece  2 L. The tab side portion  4  is placed on the upper surface of a receiving portion  5  formed by bending a bottom end of the other holding piece  2 L toward the tab  3 . Further, the leading end of the tab side portion  4  is locked in a lock groove  6  provided at the bottom end of the other holding piece  2 L. As shown in FIG. 16, the tab  3  is assembled into a bulb socket  7  by being pressed into a tab mount hole  8  formed in the bulb socket  7 . 
     The tab  3  is subjected to a large insertion resistance while being pressed into the tab mount hole  8 . Since the tab side portion  4  is placed on the upper surface of the receiving portion S in the terminal fitting  1 , the insertion resistance is received only by the lock groove  6  in a position distanced from the tab  3  without being received by the receiving portion  5 . Thus, a large moment acts on the tab side portion  4 , with the result that it may be bent as shown in FIG.  17 . 
     In view of the above problem, an object of the present invention is to provide a high strength terminal fitting for a wedge-base bulb which is not likely to be deformed while being assembled into a bulb socket and a bulb socket comprising such a terminal fitting. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a terminal fitting for a wedge-base bulb in which a pair of holding pieces for substantially holding a base section of a wedge-based bulb are formed by bending opposite sides of a metal plate at an angle different from 0° or 180°, preferably at substantially right angles. A lower end portion of one holding piece is bent to have a substantially steplike shape, thereby forming a tab adjacent the bottom of the one holding piece. A tab side portion is formed at a stepped portion of the tab by bending the lower end portion of the one holding piece toward the other holding piece. A lower end portion of the other holding piece is bent toward the tab to form a receiving portion, which is placed or is placeable on or at the upper surface of the tab side surface or portion, in particular in the folded state. 
     Accordingly, since the receiving portion is placed or placeable on or at the upper surface of the tab side portion, the upward displacement of the tab side portion can be restricted, even upon being subjected to an insertion resistance which acts during the insertion of the tab into the tab mount hole. Further, the receiving portion extends toward the tab to receive the insertion resistance near the tab. This prevents, unlike the prior art terminal fitting, a large moment from acting on the tab side portion, thereby preventing the tab side portion from being bendingly deformed. Since the support portion for the tab has a high strength in this terminal fitting, the tab is not deformed during the assembling, and operation efficiency is improved. 
     According to a further preferred embodiment, there is provided a terminal fitting for a wedge-base bulb in which a pair of holding pieces for holding a base section of a wedge-based bulb are formed by bending opposite sides of a metal plate at right angles. A lower end portion of one holding piece is bent to have a steplike shape, thereby forming a tab. The tab is insertable into a tab mount hole provided in a bulb socket at the bottom of the one holding piece. A tab side portion is formed at a stepped portion of the tab by bending the lower end portion of the one holding piece toward the other holding piece. A lower end portion of the other holding piece is bent toward the tab to form a receiving portion, which is placed on the upper surface of the tab side portion. 
     Preferably, the receiving portion is elongated and is bent or bendable to hold the tab side portion from substantially below and above, in particular in the folded state. 
     Accordingly, since the tab side portion is held surroundingly by the receiving portion, it is allowed to have more stability and strength. 
     A notch may be formed at an end of the receiving portion and a part of the receiving portion is placed or placeable substantially below the tab side portion, in particular in the folded state. Accordingly, since the tab side portion is also pushed from below by the part of the receiving portion, the tab side portion is allowed to have more stability. 
     The tab mount hole of the bulb socket preferably has a length to accommodate up to a base end of the tab when the insertion of the tab is completed, and/or the tab is formed such that the base end thereof is wider than the other portion thereof. Accordingly, since the diameter of the tab mount hole can be widened according to the width of the wide base end of the tab, a portion of the tab toward the leading end which is narrower than the base end can be inserted into the tab mount hole while leaving a margin. As a result, the terminal fitting can be inserted more easily and operational efficiency can be improved. Further, strength can be enhanced by widening the base end of the tab, thereby preventing a deformation. 
     The holding pieces preferably are formed by bending a metal plate along bending lines by an angle different from 0° or 180°, preferably substantially at right angles, such that the holding pieces are connected via a base plate. The tab side portion that is formed on the tab by bending the one holding piece is supported by the receiving portion that is formed on the other holding piece. 
     According to the invention, there is further provided a bulb socket for a wedge-base bulb comprising at least one terminal fitting as described above. The bulb socket further comprises a housing having a bulb receptacle for at least partially housing a base section of a wedge-based bulb and a connector receptacle for at least partially housing a mating connector. The terminal fitting is at least partially arranged in the bulb receptacle for its connection to the bulb and the tab is insertable into a tab mount hole provided in the housing so that a portion of the tab projects into the connector receptacle for its connection with the mating connector. According to a preferred embodiment of the invention, the tab mount hole has a length to accommodate only up to a base end of the tab when the insertion of the tab is completed. 
     Preferably, a base end of the tab is widened to the degree that it is still insertable into the tab mount hole and a portion of the tab toward its leading end is narrower than the base end such that it is insertable into the tab mount hole while leaving a margin. Accordingly, the insertion of the tab is easier and the operation efficiency is improved. 
     These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side section of a bulb socket. 
     FIG. 2 is a plan view of the bulb socket. 
     FIG. 3 is a perspective view of a terminal fitting according to one embodiment of the invention. 
     FIG. 4 is a front view of the terminal fitting. 
     FIG. 5 is a side view of the terminal fitting when viewed in a direction of arrow A of FIG.  4 . 
     FIG. 6 is a side view of the terminal fitting when viewed in a direction of arrow B of FIG.  4 . 
     FIG. 7 is a bottom view of the terminal fitting when viewed in a direction of arrow C of FIG.  4 . 
     FIG. 8 is a development of the terminal fitting according to the first embodiment of the invention. 
     FIG. 9 is a perspective view in section of a terminal fitting according to a second embodiment of the invention. 
     FIG. 10 is a front view of the terminal fitting. 
     FIG. 11 is a side view of the terminal fitting when viewed in a direction of arrow D of FIG.  10 . 
     FIG. 12 is a side view of the terminal fitting when viewed in a direction of arrow E of FIG.  10 . 
     FIG. 13 is a bottom view of the terminal fitting when viewed in a direction of arrow F of FIG.  10 . 
     FIG. 14 is a development of the terminal fitting according to the second embodiment of the invention. 
     FIG. 15 is a perspective view of a prior art terminal fitting for a bulb socket. 
     FIG. 16 is a section of prior art bulb socket and terminal fitting. 
     FIG. 17 is a front view of the prior art terminal fitting in its deformed state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the invention is described with reference to FIGS. 1 to  8 . More particularly, a wedge-base bulb  10  (hereinafter, “bulb  10 ”) is partly shown in FIG. 1, and is shaped such that a flat base section  12  is provided substantially continuously at the bottom end of a hollow light emitting portion  11  preferably substantially in the form of a cylinder (the bottom side is the side substantially opposed to the side where the bulb  10  is inserted into the bulb socket  20  or between holding pieces  35  to be described later). Lead wires (not shown) from filaments (not shown) accommodated in the light emitting portion  11  are drawn from the bottom surface of the base section  12  and folded back at the opposite surfaces of the base section  12  to form a contact or contact portions. 
     A bulb socket  20 , as shown in FIG. 1, is provided with a bulb receptacle  22  which is open toward a first side, and preferably toward the upper side, of a housing  21  that preferably is made of a synthetic resin. The base section  12  of the bulb  10  is insertable into the bulb socket  20 . A connector receptacle  23  is open toward a second side of the housing  21 , and is arranged at an angle different from 0° with respect to the first side. The connector receptacle  23  is preferably at about 180° (i.e. substantially opposed) to the bulb socket  20 , and most preferably is substantially on the lower side of the housing  21 . An unillustrated mating connector is insertable into the connector receptacle  23 . The bulb receptacle  22  and the connector receptacle  23  are substantially continuously or unitarily or integrally formed and are partitioned by a partition wall  24  provided in the housing  21 . A tab mount hole  25  is formed to extend through the partition wall  24 , and a tab  31 , provided on a terminal fitting  30  to be described later, is pressed or inserted into the tab mount hole  25 . The leading end of the tab  31  at least partially projects into the connector receptacle  23 , preferably through its back surface so as to be electrically connectable with a mating terminal fitting of the mating connector. 
     A pair of terminal fittings  30  are accommodated substantially opposite to each other (see FIG. 2) in the bulb receptacle  22 . The terminal fitting  30  is entirely shown in FIG.  3  and is provided with a long substantially flat base plate  32 . The base plate  32  is or can be accommodated in an accommodation groove  26  (see FIG. 2) formed in the inner circumferential surface of the bulb receptacle  22 . A pair of bulging or projecting portions  33  preferably are provided at the substantially opposite sides of an upper or distal end of the base plate  32 , and are or can be lockingly engaged with concealing walls  27  (see FIG. 2) that project inwardly from the opposite sides of the accommodation groove  26  so as to substantially retain or position the terminal fitting  30  in the bulb receptacle  22 . As shown in FIG. 5, a locking portion  34  extends substantially obliquely upwardly or at an angle different from 0° or 180° with respect to the base plate  32  and is formed in the rear surface of the base plate  32  by cutting and bending a portion of the base plate  32 . This locking portion  34  is locked or lockable with an engaging portion (not shown) formed in the inner surface of the bulb receptacle  22 , thereby holding or positioning the terminal fitting  30  so as not to come out. 
     Preferably at the bottom end of the base plate  32 , a pair of holding pieces  35  are provided substantially opposite to each other. The holding pieces  35  are, as shown in FIG. 3, such that base portions  35 A thereof are bent at an angle different from 0° or 180°, preferably at substantially right angles to the opposite sides of the base plate  32  and free ends  35 B thereof extend upwardly from the base portions  35 A. The leading ends of the free ends  35 B are bent toward each other so as to elastically hold the base section  12  of the bulb  10 . The holding pieces  35  may be provided laterally projecting from the base plate  32 . 
     A lower part of the right holding piece  35 R in FIG. 4 is bent toward the left holding piece  35 L and then downwardly to have a steplike shape. This downwardly extending portion serves as a flat tab  31 . A stepped portion  36  and the holding piece  35 R are partially coupled by an obliquely extending and rib-shaped embossed portion  37  (see FIG. 4) to enhance a strength. The tab  31  is suspended from a side of the stepped portion  36  away from the base plate  32  as shown in FIG.  7  and preferably is formed by putting two metal plates together as shown in FIG.  4 . The left one of the metal plates is bent to project substantially symmetrically with the stepped portion  36 , thereby forming a tab side portion or connection portion  38 . The tab side portion  38  has its intermediate portion bent moderately upward as shown in FIG.  4  and its leading end fitted in a lock groove  40  (see FIG. 3) formed at the bottom end of the left holding piece  35 L. 
     On the other hand, a lower portion of the left holding piece  35 L in FIG. 4 is bent at an angle different from 0° or 180°, preferably at a substantially right angle to the right holding piece  35 R to form a receiving portion  39 . The receiving portion  39  is formed with a slit  41  which is open at a side substantially opposite from the base plate  32  or at a side of the tab  31  and extends to a substantially middle position with respect to its widthwise direction as shown in FIG. 7, and first and second small projections  39 A,  39 B are formed at the opposite sides of the slit  41 . As shown in FIG. 4, the first small projection  39 A at the right side of the slit  41  is placed on the base side of the tab side portion  38 , and the second small projection  39 B at the left side of the slit  41  is placed below the leading end of the tab side portion  38  or the first and second small projections  39 A,  39 B project in substantially opposed directions. 
     A blank of metal, or development of the terminal fitting, according to the invention is shown in FIG.  8 . Corresponding portions of the development are identified by the same reference numerals. The terminal fitting according to this embodiment is completed by bending the respective portions along broken lines  33 L,  34 L,  36 L,  39 L (shown in FIG. 8) by bending angles different from 0° or 180°, wherein the bending angles along the lines  33 L and  34 L are preferably comprised between 20° and 60°, whereas the bending angles along the lines  36 L and  39 L are preferably about 90°. 
     To assemble the terminal fitting  30  into the bulb socket  20 , the tab  31  is pushed into the tab mount hole  25  formed in the housing  21  by gripping the base plate  32  of the terminal fitting  30 . Then, a force acts on the tab  31  in such a manner as to push the tab  31  into a clearance between the holding pieces  35  due to an insertion resistance (or due to a deflection resistance caused by the elastic bending strength of the holding pieces  35 ), and the tab side portion  38  substantially continuous with the tab  31  tries to undergo an upward displacement. However, since the first small projection  39 A of the receiving portion  39  is placed on the upper surface of the tab side portion  38  in the terminal fitting  30  of this embodiment, the upward displacement of the tab side portion  38  is restricted, thereby substantially preventing a deformation thereof. Further, the first small projection  39 A pushes a portion of the tab side portion  38  near the tab  31  from above. This prevents a large moment from acting on the tab side portion  38  and, accordingly, prevents the tab side portion  38  from being bendingly deformed. Furthermore, since the tab side portion  38  is pushed from below by the second small projection  39 B of the receiving portion  39 , the tab side portion  38  is allowed to have more stability and strength. 
     As described above, since the support portion of the tab  31  has a high strength in the terminal fitting  30  of this embodiment, the tab  31  is not deformed while the terminal fitting  30  is assembled into the bulb socket  20 , which leads to a better operation efficiency. 
     A second embodiment of the invention is described with reference to FIGS. 9 to  14 . The terminal fitting  30  according to this embodiment is constructed such that the tab side portion  38  is held substantially surroundingly by a receiving portion  45  from above and below. The receiving portion  45  is strip-shaped in its developed state as shown in FIG.  14 . The receiving portion  45  at least partially covers the lower surface of the tab side portion  38  by its base end side, is folded up at the edge of the tab side portion  38  to at least partially cover the upper surface of the tab side portion  38 , and preferably has its leading end bent between the tab side portion  38  and the base plate  32 . In this way, the tab side portion  38  is fixed by being held surroundingly by the receiving portion  45 . 
     As can be seen by the comparison of FIGS. 8 and 14, the tab side portion  38  of this embodiment is substantially wider than the of the first embodiment. This is because the width of the side tab portion  38  of the first embodiment is restricted by the slit  41  unlike that of the second embodiment since it is surrounded by the receiving portion  45 . 
     In the terminal fitting  30  of this embodiment, a base end  46  of the tab  31  is stepped so as to be wider than the other portion as shown in FIG.  9 . The base end  46  has the same width as the tab side portion  38  as shown in FIG.  14  and is continuous with the tab side portion  38  and the stepped portion  36 . When the tab  31  is inserted to the bottom of the tab mount hole  25  (see FIG. 1) formed in the bulb socket  20 , the base end  46  of the tab  31  is accommodated in the tab mount hole  25 . 
     Since the other construction is similar to the foregoing embodiment, no description is given thereon by identifying the same elements by the same reference numerals. 
     Since the tab side portion  38  is at least partially surrounded by the receiving portion  45  in the terminal fitting  30  of this embodiment, the receiving portion  45  and the tab side portion  38  can firmly be fixed. Accordingly, a force transmitted from the tab  31  to the tab side portion  38  when the terminal fitting  30  is assembled into the bulb socket  20  can be received by the receiving portion  45 . As a result, the terminal fitting  30  is allowed to have more stability and strength. 
     Further, since the base end  46  of the tab  31  is widened and made substantially continuous with the stepped portion  36  and the tab side portion  38 , the tab  31  can be supported with a larger strength. Particularly in the second embodiment, the width of the tab side portion  38  is not subject to restriction by surrounding the tab side portion  38  by the receiving portion  45 . Thus, the tab side portion  38  and the base end  46  of the tab  31  can be made substantially continuous while having the same width, and a strength between the tab side portion  38  and the tab  31  can be enhanced. 
     Furthermore, since only the base end  46  of the tab  31  is widened and this base end  46  is made still insertable into the tab mount hole  25  of the bulb socket  20 , a portion of the tab  31  toward its leading end which is narrower than the base end  46  is insertable into the tab mount hole  25  while leaving a margin. This makes the insertion of the tab  31  easier and leads to an improvement in operation efficiency. 
     Further, operability is good since the tab side portion  38  and the receiving portion  45  are fixed by only surrounding the tab side portion  38  by the receiving portion  45  in a process of assembling the terminal fitting  30 . 
     The present invention is not limited to the described and illustrated embodiment, but the following embodiment also is embraced by the technical scope of the present invention as defined in the claims. Besides the following embodiment, a variety of other changes can be made without departing from the scope and spirit of the invention as defined in the claims. 
     Although the tab side portion  38  is supported also from below by the second small projection  39 B in the foregoing embodiment, it may be supported only from above by the receiving portion. 
     Although the receiving portion  45  of the second embodiment surrounds the tab side portion  38  from below, it may do so from above.