Abstract:
An electrical contact terminal made from electrically conductive material includes a surface having a contact tab. The contact tab has a linear contact region for mechanically contacting a contact surface. An embodiment of the contact terminal may have a contact tab that includes a sector of a cylinder and provides a substantially linear contact region when abutted to a contact surface. The contact terminal may include a locking tab for attaching the electrical contact terminal to a base.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a contact terminal of a lamp assembly. A contact terminal provides electrical continuity between a lamp assembly and a solder track on a printed circuit board or other fixture into which the lamp assembly is installed. Contact terminals having hemispherical shapes are known. 
     SUMMARY OF THE INVENTION 
     The invention provides a contact terminal that is cylindrical in shape and has a linear contact region that perpendicularly intersects a solder track on a printed circuit board. Relative to hemispherical terminals, which have a single point of contact, the linear contact region of the cylindrical terminal greatly improves the likelihood that the contact terminal will form a stable electrical connection with the solder track. This, in turn, reduces the accuracy with which the lamp assembly installation hole and solder tracks must be positioned. 
     In one aspect, generally, the invention features an electrical contact terminal made from electrically conductive material. The terminal includes a surface having a contact tab. The contact tab has a linear contact region for mechanically contacting a contact surface. 
     Embodiments of the invention may include one or more of the following features. The contact tab may be in the shape of a plane that is bent in a single dimension. For example, the contact tab may be a sector of a cylinder. 
     The electrical contact terminal may include a body having a first surface and a perpendicular second surface, and may be made from a single piece of electrically conductive material. The contact tab may include a first end connected to the first surface and an unattached, free end that permits displacement of the contact tab when the contact tab is abutted to a contact surface. The contact tab may extend beyond the first surface. The second surface of the contact terminal may include a locking tab. 
     The contact terminal may be employed in a lamp assembly that also includes a base and a light bulb installed in the base. The contact terminal may be electrically connected to the light bulb. The contact terminal may be secured in the base by the locking tab. 
     Other features and advantages of the invention will be apparent from the following detailed description, including the drawings, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of a lamp assembly with a cylindrical contact terminal. 
     FIG. 2 is a perspective view of the cylindrical contact terminal of FIG. 1. 
     FIG. 3 is a side view of the lamp assembly and cylindrical contact terminal of FIG. 1. 
     FIG. 4 is a perspective view of a printed circuit board. 
     FIGS. 5 and 6 are top views of a printed circuit board and a lamp assembly. 
     FIGS. 7 and 8 are side views of a lamp assembly (without a bulb) and a printed circuit board. 
     FIG. 9 is a plan view illustrating contact regions between cylindrical contact terminals and solder tracks on a printed circuit board. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, a lamp assembly 5 may include a metal contact terminal 10 secured to a plastic lamp base 15. A bulb 20 is attached to the lamp base. Referring also to FIG. 2, the contact terminal 10 may be fabricated from a single piece of conductive metal. The top 22 of the contact terminal has a contact tab 25 in the shape of a sector of a cylinder. The contact tab includes a fixed end 30 and a free end 35. The fixed end 30 is continuous with the single piece of conductive metal from which the contact terminal is formed. A gap exists between the free end 35 of the contact tab 25 and the top 22 of the contact terminal 10. As discussed below, this gap permits displacement of the contact tab 25 when the contact tab is abutted to a contact surface. 
     The back 40 of the contact terminal 10 is perpendicular to the top thereof. The back 40 acts as an insertion tab to ease insertion of the contact terminal 10 into the base 15 of the lamp assembly 5. The back 40 of the contact terminal has a locking tab 45 to hold the contact terminal in the base 15. 
     Referring again to FIG. 1, a contact terminal is inserted into a position on the side of the base 15. A second contact terminal (not shown) is positioned in the same manner on the opposite side of the base 15. The back 40 of the contact terminal 10 and the locking tab 45 are visible from the side of the base 15. The lamp leads 12, which provide an electrical connection to the bulb 20, are connected to the contact terminal, generally by resistance welding. 
     The base 15 has a mounting ledge 50 around its substantially round circumference. The top surface of the ledge 50 abuts the contact surface (not shown) when the lamp assembly is installed in a printed circuit board, as described below. Two tabs 55 folded from the top surface 22 of the contact terminal 10 hold the contact terminal in position with the top surface 22 just below the top surface of the mounting ledge 50. With this positioning, the contact tab 25 on the contact terminal 10 extends slightly above the top surface of the mounting ledge 50. The base 15 also has two locking tabs 60, shown in the side view of the lamp assembly of FIG. 3. These tabs hold the lamp assembly in position in the printed circuit board. 
     FIG. 4 shows a portion of a printed circuit board 70 into which the lamp assembly may be installed. To install the lamp assembly, the assembly is inserted, bulb end first, through the hole 75 in the printed circuit board 70. The locking tabs 60 on the lamp base pass through the slots 80 on opposite sides of the hole 75. The lamp assembly is inserted until the top surface of the mounting ledge 50 of the base 15 is flush with the contact surface 85. The lamp assembly is then rotated so that the tabs 60 move over edges of the slots 80 to hold the lamp assembly in place. 
     The contact tab 25 of the contact terminal 10 abuts the contact surface 85 when the lamp assembly is installed. More specifically, the contact tab 25 is coincident with a solder track 90 on the contact surface 85. The abutment of the contact tab 25 to the solder track 90 provides a path through which electrical current may flow. 
     The abutment of the contact tab 25 to the contact surface 85 can be represented geometrically as the intersection of a cylinder and a plane. The intersection of these geometric shapes is a line. 
     FIG. 5 shows a top view of the lamp assembly inserted into the printed circuit board 70. The locking tabs 60 are coincident with the slots 80 in the printed circuit board. The lamp assembly is then rotated in the clockwise direction so that the locking tabs 60 of the base 15 grip the printed circuit board 70, holding the lamp assembly firmly in place, as shown in FIG. 6. 
     FIG. 7 shows the contact terminal 10 in the lamp base 15 prior to insertion through the hole 75 in the printed circuit board 70. The insertion and rotation of the lamp assembly will result in the contact tab 25 being displaced, as it extends slightly above the top surface of the mounting ledge 50. FIG. 8 shows the contact terminal 10 after it has been inserted into the printed circuit board 70 and rotated to lock it in place. The bending of the contact tab 25 results in a constant force which holds the contact tab 25 firmly against the contact surface 85. 
     Referring also to FIG. 9, the surface area of physical contact between the contact tab 25 and the contact surface 85 is a linear contact region 115 of narrow width. The width of the linear contact region 115 depends primarily upon the radius of curvature of the cylindrical contact tab 25 and the extent of deformation of the contact tab 25 as it is abutted to the contact surface 85. The linear contact region 115 extends radially from the center of the hole 75 through which the lamp assembly is inserted. This linear contact region 115 is oriented so as to perpendicularly intersect the solder tracks 90 on the contact surface 85, as shown in FIG. 9. 
     Other embodiments are within the scope of the following claims.