Abstract:
A terminal formed by bending from a single metal piece for use in a bulb socket having a bulb insertion opening for accommodating a bulb, where the terminal is used for connecting with a base electrode formed in the outer perimeter of the bulb includes a contact element. The contact element is formed by stamping the metal piece to have a contact portion and a spring portion for resiliently hold the contact portion in contact with the base electrode. The spring portion is located on a position away from the base electrode when the bulb is inserted in the bulb insertion opening. Therefore, the spring porion of the contact element is kept from deterioration of spring characteristics caused by the heat from the bulb.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a terminal used in a bulb socket for use in automotive lights and, more particularly, to a terminal positioned inside the bulb socket and having a contacting element whose deterioration of the spring characteristics is prevented to improve the contact reliability to the negative terminal of the bulb base. 
     2. Description of the Prior Art 
     In FIGS. 9 and 10, a conventional socket-side negative terminal 1 for use in a bulb socket 2 formed by bending a single thin metal band is shown. The socket-side negative terminal 1 comprises a bulb-side connecting element 1a for electrically connecting with the bulb 3 formed flexibly stamped out at one end portion thereof, and a connector 1b for electrically connecting with the external connectors provided at the other end portion thereof. 
     As shown in FIG. 11, the terminal 1 is inserted to an insertion channel 2c with a T-shaped cross section formed in a perimeter wall 2b of a bulb insertion opening 2a of the socket 2. The tip of the connecting element 1a protruding to the inside from the insertion channel 2c contacts the negative terminal face of the bulb base 3a inserted to the bulb insertion opening 2a. 
     The connector 1b of the terminal 1 protrudes into the connector insertion opening 2g from the insertion hole formed in the bottom wall 2f of the bulb insertion opening 2a, and contacts the external connector (not shown). 
     A positive terminal 4 formed by bending a single metal piece is inserted to a positive terminal insertion channel 2d, which is formed diagonally to the negative terminal insertion channel 2c of the socket 2. A bulb-side connector 4a contacts the positive terminal of the bulb bottom 3d, and the other connector 4d protruding from the bottom wall 2f connects with the external connector. 
     A bulb 3 depicted by an imaginary line is secured in the socket 2 by inserting from the top a pair of pins 3b, which protrude at the outside circumference of the bulb base 3a, into J-shaped pin insertion channels 2h formed in the bulb insertion opening perimeter wall 2b, and then turning the bulb 3 after insertion to secure the bulb 3 in the socket 2. 
     As best shown in FIG. 9, the bulb-side connecting element 1a of this conventional negative terminal 1 is stamped out at the center near the end of the thin metal band lc to project at a specified angle θp and extends by a predetermined length Lc from the base 1d of the stamping and to flexibly contact the bulb base 3a with the contact 1e on the end of the projection. 
     When the negative terminal 1 shaped as described above is inserted to the socket 2 and contacts the bulb 3, the stamped base 1d of the connecting element 1a is positioned at the open end of the bulb insertion opening 2a approximately opposite the bulb base 3a, as best shown in FIG. 11. 
     When the bulb 3 is continuously turned on, the base 1d becomes hot because of the heat generated by the bulb 3. In particular, for example when a high output bulbs or double bulb are used for the bulb 3, the temperature at the base 1d sometimes reaches approximately 180° C. 
     When the base 1d of connecting element 1a gets hot, the spring characteristics thereof deteriorate so that the contact pressure of the contact 1e drops, and the contact resistance at the circumference of the bulb base 3a increases. This causes the already high temperature to rise further, resulting eventually in non-conductivity. 
     The deterioration of the spring characteristics of the base 1d will be described with reference to FIGS. 12A, 12B, and 12C. Since the connecting element 1a initially has sufficient spring, the connecting element 1a extrudes from the terminal 1 by a predetermined length To and positioned thereat, an original position inside the bulb insertion opening, as indicated by the imaginary line in FIG. 12A. When the bulb 3 is inserted in the bulb socket 2, the connecting element 1a is pressed by the bulb base 3 so that the connecting element 1a is moved from the original position to a contacting position at which the connecting 1a is resiliently contacted with the bulb base 3, as indicated by a solid line. 
     However, as the spring characteristics of the base 1d deteriorates, the connecting element 1a will eventually not return to the original position and stops at a deteriorated position below the terminal 1 by a length Td, as indicated by a imaginary line in FIG. 12B, even when the bulb 3 is removed from the socket 2. In this case, when other bulb 3 with a smaller base diameter is inserted into the socket 2, a gap Tg occurs between the outside circumference of the bulb base 3a and the contact 1e, as shown in FIG. 12C. Thus, the connecting element 1a can not contact with the bulb base 3a, resulting in the lack of conductivity between the terminal 1 and the bulb 3. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is therefore to provide a terminal which solves these problems. 
     The present invention has been developed with a view to substantially solving the above described disadvantages and has for its essential object to provide an improved terminal. 
     In order to achieve the aforementioned objective, a terminal formed by a single metal piece for use in a bulb socket having a bulb insertion opening for accommodating a bulb, wherein said terminal makes an electric connection with a base electrode formed on outer perimeter of said bulb upon insertion of said bulb, said terminal comprises a flat plate portion; and a contact portion raised from said flat plate portion for contacting said base electrode, said contact portion integrally connected to said flat plate portion through a base portion, said base portion being located remote from said base electrode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings throughout which like parts are designated by like reference numerals, and in which: 
     FIG. 1 is a cross-sectional view showing a bulb socket comprising a terminal according to a first embodiment of the present invention the invention, 
     FIG. 2 is an enlarged side view showing the terminal of FIG. 1, 
     FIG. 3 is a plan view showing the terminal, viewed from the bottom side thereof, of FIG. 2, 
     FIG. 4 is a fragmentary cross-sectional view showing a portion of the terminal taken along a line IV--IV in FIG. 3, 
     FIG. 5 is a cross-sectional view showing a terminal according to a second embodiment of the present invention, a side view of a negative terminal according to the second embodiment of the invention, 
     FIG. 6A is a plan view showing the terminal, viewed from the bottom side thereof, of FIG. 5, 
     FIG. 6B is a plan view showing the terminal at a partially developed state, of FIG. 6A, 
     FIG. 7 is a front view showing the terminal, viewed from the left side, of FIG. 5, 
     FIG. 8 is a fragmentary cross-sectional view showing a portion of the terminal taken along a line VIII--VIII in FIG. 6A, 
     FIG. 9 is a side view showing a conventional terminal for use in a bulb socket, 
     FIG. 10 is a plan view showing the terminal, viewed from the bottom side thereof, of FIG. 9, 
     FIG. 11 is a cross-sectional view showing a bulb socket comprising the conventional terminal of FIG. 9, and 
     FIGS. 12A, 12B, and 12C are fragmentary side views in assistance of explaining the deterioration state of the conventional terminal of FIG. 9. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 2, 3, and 4, a negative terminal used for the connection with a negative electrode of a bulb according to a first embodiment of the present invention is shown. The terminal 10 is formed in an elongated shape by bending a single metal piece. The terminal 10 includes a flat member 10b formed in an elongated thin band-shape extending in a direction, and a vertical support 10s formed at one end of the flat member 10b and extending perpendicularly therefrom. The terminal 10 further includes a connector member 10g formed at one end of the vertical support 10s opposed to the flat member 10b. The connector member 10g extends therefrom in such a direction that the connector member 10g is apart from the flat member 10a. Thus, the flat member 10b and connector member 10g are connected by the vertical support 10s. A stopper 10z is stamped out from the vertical support 10s to open to the direction opposed to the connector member 10g. 
     The flat member 10b has a contact element 10a cut in the middle portion thereof generally in a U-shaped configuration so that a base portion 10d by which the contact element 10a is integrally connected with the flat member 10b is formed on the side contiguous to the vertical support 10z. The contact element 10a is further stamped in generally a V-shaped configuration when viewed from the side, as best shown in FIG. 4, such that a stamped end 10e is positioned at the end portion of the flat member 10b. The contact member 10a projects at a specified angle 8 downward (toward the vertical support side) from the stamped base 10d and is bent upward (toward the flat member 10b) at a position distant from the base 10g by a predetermined length Ld. Thus, a contact portion 10c is formed at the valley portion of thus bent member 10a. Preferably, the tip of stamped end 10e is bent down to extend parallel to the flat member 10b. Since the contact element 10a is elastically stamped out, the base portion 10d provides spring effect to the contacting element 10a so that the contacting element 10 can swing elastically with respect to the base portion 10d against the external force. 
     Each of longitudinal sides of the flat member 10b is bent inside to provide a side rim 10h extending on both sides thereof. 
     Referring to FIG. 1, the terminal 10 used in a bulb socket 2 is shown. The terminal 10 is inserted to an insertion channel 2c with a T-shaped cross section formed in a perimeter wall 2b of a bulb insertion opening 2a of the socket 2. The tip 10c of the connecting element 10a protrudes to the inside from the insertion channel 2c and contacts the terminal face of a bulb base 3a. The base portion 10d is positioned at the bottom wall 2f side of the bulb insertion opening 2a, and the stamped end 10e is positioned at the open end side. And the stopper 10z is engaged with the socket 2 to prevent the terminal 10 from being removed. Then, the bulb 3 depicted by an imaginary line is inserted to the bulb insertion opening 2a from the bulb base 3a, the stamped base portion 10d is positioned at the open end of the bulb insertion opening 2a away from the bulb base 3a. 
     The connector member 10g of the terminal 10 protrudes into the connector insertion opening 2g from the insertion hole formed in the bottom wall 2f of the bulb insertion opening 2a, and contacts the external connectors (not shown) coming from the outside of the socket 2. 
     A positive terminal 4 used for the connection with a positive electrode of the bulb 3 is formed by bending a single metal piece, and is inserted to a positive terminal insertion channel 2d, which is formed diagonally to the negative terminal insertion channel 2c of the socket 2. A bulb-side connector 4a contacts the positive terminal of the bulb bottom 3d, and the other connector 4d protruding from the bottom wall 2f connects with the external connector. 
     The bulb 3 is secured in the socket 2 by inserting from the top a pair of pins 3b, which protrude at the outside circumference of the bulb base 3a, into J-shaped pin insertion channels 2h formed in the bulb insertion opening perimeter wall 2b, and then turning the bulb 3 after insertion to secure the bulb 3 in the socket 2. 
     In the first embodiment thus comprised, it is difficult for the base 10d to reach a high temperature, making it difficult for the spring characteristics to deteriorate, because the base 10d of the contact element 10a is separated away from the bulb base 3a of the heat-emitting bulb 3. Furthermore, the base 10d is positioned at a side contiguous to the connector member 10g through the vertical support member 10s. Since these members 10g and 10s are located in positions remote from the bulb base 3a, and are connected with heat/electrical conductive materials such as connectors and wires having lower temperature and greater heat capacity, the heat transmitted to the base 10d is scattered outside through these members. Thus, the base 10d can be kept within the temperature range in which the spring characteristics thereof will not deteriorates. Based on tests, the temperature at the base 10d is less than approximately 150° C., meaning that the improved cooling ability of more than 30° C. is obtained by the terminal 10 according to the present invention when compared with the conventional terminals. 
     Contact reliability of the negative terminal 10 is thus improved without inducing a drop in the contact pressure of the contact portion 10c because deterioration of the spring characteristics of the contact element 10a is difficult according to the present invention. 
     It is to be noted that the stamped end 10e of the contact element 10a is positioned at the insertion side of the bulb base 3a, but insertion of the bulb base 3a can be done smoothly because the stamped end 10e is folded back opposite to the stamped direction. 
     In the first embodiment, the length Ld between the base 10d and the contact 10c can be set longer than the conventional length Lc (see FIG. 9), and the lift angle θ of the base 10d can be less than the lift angle θp of the conventional terminal (FIG. 9) because the base 10d of the contact element 10a is provided on the side of the bottom wall 2f of the bulb insertion opening 2a in the socket 2. As a result, the stress acting on the base 10d is reduced, there is no concentration of excessive stress, and deterioration of the spring characteristics is inhibited. In the first embodiment, the contact reliability of the negative terminal 10 can also be improved because of this. 
     Referring to FIGS. 5, 6A, 6B, 7, and 8, a terminal according to a second embodiment of the present invention is shown. The terminal 10&#39; has the construction similar to that of the terminal 10 according to the first embodiment, as shown in FIGS. 5 and 6A. 
     In FIG. 6B, a developed state of a flat member 10b &#39; of the terminal 10&#39; before bending is shown. The negative terminal 10&#39; has a first side members 10j&#39; on the one of elongated sides, and a second side member 10k&#39; on the other elongated side. The first side member 10j&#39; is folded inside in the arrow direction D1 with respect to a first side line L1 indicated by a dot line to overlap with the center portion 10m&#39; of the flat member 10b&#39;. Also, the second side member 10k&#39; is folded inside in the arrow direction D2 with respect to a second side line L2 indicated by a dot line. Thus, the terminal 10&#39; can be completed, as shown in FIG. 6A. 
     In this terminal 10&#39;, the contact element 10a&#39; is formed at the outside edge of the first side members 10j&#39;. The contact element 10a&#39; is positioned at the midpoint of the center portion 10m&#39;, and an inside edge 10n&#39; of the first side member 10j&#39; is doubled along the first side line L1, forming a first side edge of the center portion 10m&#39;. 
     The second side member 10k&#39; is folded double along the second side line L2, forming a second side edge of the center portion 10m&#39;. As a result, both outside edge members of the center portion 10m&#39; are completely doubled. 
     At the center of the center portion 10m&#39; overlapping the contact element 10a&#39;, a small clearance hole 10i&#39; for passing the stamped end 10e&#39; when the contact element 10a &#39; is in contact with the bulb base 3 is formed at a position opposing to the stamped end 10e&#39;. The remainder other than the clearance hole 10i&#39; reinforces the other parts of the contact element 10a&#39;, specifically backing the base 10d&#39; of the contact 10c&#39;. 
     In this second embodiment, both sides of the flat member 10b&#39; on which the contact element 10a&#39; is provided are completely doubled, the center portion 10m&#39; is positioned behind the projecting part of the contact element 10a&#39;, and the open space from forming the contact element 10a&#39; is reduced, making it possible to improve the strength. 
     In addition, because it is sufficient to provide the clearance hole 10i&#39; formed in the center portion 10m&#39; to oppose to the stamped end 10e&#39;, the clearance hole 10&#39; can be made small. The overall area of the flat member 10b&#39; can thus be increased, increasing the heat dissipation area much, and improving the heat dissipation characteristics because the area of the center portion 10m&#39; can be increased and both side members 10j&#39; and 10k&#39; are folded back. 
     Furthermore, since the terminal 10&#39; has the contact element 10a&#39; which is additionally provided thereto, as shown in FIGS. 6A and 6B, the terminal 10&#39; has the heat capacity greater than that of the terminal 10 according to the first embodiment. Therefore, it is more difficult to elevate the temperature of the base 10d&#39; of the terminal 10&#39; when compared with the terminal 10. 
     As will be obvious from the above description, the bases 10d and 10d&#39; do not easily reach a high temperature because the base 10d and 10d&#39; are provided on the bottom wall side, remote from the bulb base 3a, of the insertion end of the bulb insertion opening of the bulb socket 2. Good spring characteristics can thus be maintained, and contact reliability can be improved, because the bases 10d and 10d&#39; are not exposed to high temperatures and deterioration of the spring characteristics can be prevented. 
     Furthermore, since the bases 10d and 10d&#39; are located on a side contiguous to the connector element 10g which will be connected with heat/electrical conductive materials such as connectors and wires having lower temperature and greater heat capacity, the bases 10d and 10d&#39; can be kept in a lower temperature range in which the deterioration of spring characteristics thereof can be prevented. 
     In addition, stress acting on the contact elements 10a and 10a&#39; are low, excessive stress is not concentrated on the bases 10d and 10d&#39;, deterioration of the spring characteristics is prevented, and contact reliability can also be improved accordingly because the length Ld between the base portion 10d (10d&#39;) and the contact 10c (10c&#39;) can be long, and the lift angle θ of the base can be low. 
     In addition, strength is improved, the heat dissipation area is increased, and heat dissipation characteristics can be improved because the flat member is reinforced by the folded side members and the hole for stamping is eliminated in the flat member when both sides of the flat member of the negative terminal are folded in two and the connector is provided at one of the folded sides. 
     Although the present invention has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.