Abstract:
A combination ground and power source circuit tester device includes a cylindrical plug with a cone-shaped end that fits into a vehicle accessory receptacle. An attached body member engages the plug and retains first and second radially extending contacts that function to provide a connection with conductive studs that attach to leads to a circuit. A light bulb indicating that the circuitry is powered is retained in the body member and in a parallel circuit with the contacts.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part application of prior application Ser. No. 08/972,502 filed Nov. 18, 1997, now abandoned, for which priority is claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     In a principal aspect, the present invention relates to a combination ground and power source device for use in a cigarette lighter receptacle of a vehicle. The device provides both a ground connection as well as a 12-volt power connection depending upon the terminals of the device which are connected in a circuit. Further, there is an indicator light which identifies whether the system contacts are powered or activated. 
     Automotive mechanics often need an effective ground to check electrical circuits in a vehicle. Additionally, a power connection is often required to test a circuit or a device. The cigarette lighter receptacle (now often termed the accessory receptacle) in a vehicle has been used to provide power for various purposes, including mobile phones, radar detectors, radios, and circuit testers. Typically, a special plug is provided to fit into the receptacle with leads that connect to the phone, etc. U.S. Pat. No. 4,540,940 discloses an example of a device capable of deriving power from a receptacle in a vehicle. 
     The use of a device of this nature to provide a ground, as well as a power source, has also been suggested. Applicants&#39; assignee has, for example, as early as 1988, received suggestions of this general nature. There remains, however, the need for a practical, useful, efficient and rugged device of this type. In view of this background, the present device, having a positive and a negative or ground contact for circuit and device testing, was developed. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention comprises a combination ground and power source device for use in an accessory receptacle of a vehicle. The device includes a cylindrical plug which has a cone-shaped end and an axial passage through the plug. The plug is designed to fit within the accessory receptacle of a motor vehicle. The plug is also designed to cooperate with and receive a separate contact or terminal body at the outer end thereof. The terminal body retains a light bulb preferably by means of a bayonet connection and also cooperatively retains first and second, spaced, conductive studs. One of the studs is connected to a ground contact. That ground stud also connects simultaneously with a radial contact retained between the plug and the terminal body. The radial contact serves as a ground for the light bulb. A second radial contact is also retained between the plug and terminal body and makes electrical contact with the hot or powered stud as well as the light bulb retained within the body. The second radial contact further connects with a central spring-biased conductive plunger which projects axially from the device and connects to a power source. The device may thus be used as a ground source or alternatively as a power source when plugged into the vehicle accessory receptacle. The light bulb retained within the central body of the device is in a parallel electrical circuit with the contact studs and provides an indication that circuits are operable through the ground stud as well as the power stud. 
     Thus it is an object of the invention to provide an improved combination ground and power source device for use with a receptacle in a vehicle. 
     It is a further object of the invention to provide a combination ground and power source device which includes first and second conductive studs connected respectively to a ground and a power source wherein the same ground and power sources are also connected in parallel through a light bulb or indicator. 
     Yet a further object of the invention is to provide a ground and power source device which includes a cylindrical plug capable of being positioned within a vehicle accessory receptacle and which further includes a spring-biased contact or plunger within the plug for connecting to the voltage or positive power source in the accessory receptacle. 
     Another object of the invention is to provide an improved combination ground and power source device which is easy to manufacture, rugged, highly reliable, and reasonably economical. 
     These and other objects, advantages and features of the invention will be set forth in the detailed description which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the detailed description which follows, reference will be made to the drawing, comprised of the following figures: 
     FIG. 1 is an isometric view of the improved combination ground and power source device of the invention; 
     FIG. 1A is an exploded isometric view of the device; 
     FIG. 2 is a partially cut away elevation view of the device of FIG. 1; 
     FIG. 3 is an end plan view of the plug of the invention; 
     FIG. 4 is a cross-sectional view of the plug taken along the line  4 — 4  in FIG. 3; 
     FIG. 5 is a bottom plan view of the body of the device; 
     FIG. 6 is a cross-sectional view of the body taken substantially along the line  6 — 6  of FIG. 5; and 
     FIG. 7 is a plan view of the outside end of the body. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the figures, the ground and power source device of the present invention is depicted in FIG.  1  and FIG. 1A in isometric views available for insertion into a power and ground receptacle such as a vehicle cigarette lighter receptacle. The device thus includes a cylindrical plug  10  which is made from a non-conductive material, such as the polymeric with the trade name Acetal, by a molding process. The plug  10  cooperates with a separate body and stud assembly  12 . A body section  20  of stud assembly  12  is also made from an insulating, or nonconductive, molded material such as the polymeric, Acetal. The body and stud assembly  12  includes generally parallel, outwardly extending, spaced conductive studs  14  and  16  which are described in greater detail below. 
     The plug  10  is generally cylindrical and includes a forward cone shaped or frustoconical shaped, leading end  18 , a cylindrical body section  20  and, at the inside or opposite end, outwardly extending flanges or wings  22  and  24 . The plug  10  has a center line axis  29  and the wings  22 ,  24  extend transversely in opposite directions from the axis  29 . A through passage  30  extends axially entirely through the plug  10 . The through passage  30  includes a counterbore or counter passage section  32  defining an annular flange  34  connected with a smaller diameter exit passage  36  in the frustoconical shaped, leading end  18 . A recessed section or second counterbore  38  is defined in the opposite end of the plug  10  distal from the frustoconical shaped, leading end  18 . 
     As shown in FIG. 2, the plug  10  is adapted to receive a conductive, projecting plunger  40  which extends axially through the passage  36  and includes a connected, increased diameter, hollow cylindrical sliding sleeve or section  42  which rides within the passage  32  and is restricted in its axial movement toward the end  18  by the flange  34 . A conductive cylindrical slug or pin  44  fits within the internal diameter of the sleeve  42  and is axially biased by a spring  46 . That is, the spring  46  fits within the cylindrical cavity  43  of sleeve  42  and biases against the plunger  40  as well as the pin or slug  44 . 
     The body and stud assembly  12  is comprised of the molded body section  20  and includes the ground stud  14  and the higher voltage, positive or hot stud  16  molded therein as depicted in the figures. The body  20  further includes a through passage  52  which is adapted to receive a light bulb  54  having a base  68  with a center or hot contact  56  and an annular ground contact  58 . The base further includes, radial, bayonet projections  60  and  62 . The bayonet projections  60  and  62  fit into axial slots  64  and  66  defined respectively in the sides of the through passage  52  of section  20  so that the bulb  54  may be axially inserted into the through passage  52  and more particularly the base  68  may be fitted into the passage  52  and adapted to be rotated so that the lugs or projections  60  and  62  will engage or catch on a flange  69  of section  20 . The bulb  54  is biased axially, outwardly in the through passage  52  as will be explained in greater detail below. Passage  52 , studs  14 ,  16  and passage  30  are all parallel to axis  29 . 
     The studs  14  and  16  are made from a conductive material such as copper, brass, or some other conductive material. The studs  14  and  16  have threaded outer ends  70  and  72  with transverse lead passages  71 ,  73  respectively. The inner ends  75  and  77  are threaded and spaced so as to cooperate with and pass through openings of radial contacts  76  and  78 , respectively. Thus a contact  76  includes an opening  80  which receives the end  75  of stud  14  therethrough and which makes electrical contact therewith. The contact  76  extends radially from axis  29  and is positioned to engage with the annular ground contact  58  of the bulb  54 . Contact  76  thus includes parallel side extensions  90  at one end and is retained on stud  14  at the opposite end. 
     The stud  14 , and more particularly, threaded end  75 , also projects through one of the wings, such as wing  24  of plug  10 , and connects with a separate, conductive, low shaped, metal retainer contact  94 . The arcuate or flexible bow retainer contact  94  acts as a spring member along one lateral side edge of the plug  20 . Thus with respect to the ground connection, the stud  14  connects electrically to the contact  76  as well as to the retainer contact  94 . The retainer contact  94 , when inserted into an accessory receptacle in an automobile, provides the ground contact. The electrical circuit passes through the stud  14  and also through the contact  76  which connects with the ground side of the bulb  54 . The threaded end  75  of stud  14  receives a nut  81 , to hold the assembly parts together, including retainer contact  94 , wing  22  (plug  10 ), contact  76 , and body section  20 . Contacts  94  and  76  sandwich the wing  24 . 
     The other radial, metal contact  78  cooperates with and engages with the stud  16 . The stud  16  includes the threaded end  77  which fits through opening  82  in contact  78  and provides for electrical contact therewith. End  77  then fits through opening  85  in wing  22 . A hexagonal nut  83  is threaded on end  77  and holds the stud  16  in position engaged with the contact  78  and wing  24 . The contact  78  extends generally radially outwardly from the axis  29 . It extends from the center axis  29  of the plug  20  and is thus intersected by the axis  29  so that the pin or slug  44  can make electrical contact therewith. The slug  44  is thus biased by spring  46  into engagement with the contact  78 . The contact  78  thereby engages the hot side contact  56  of the bulb  54  and serves the dual function of biasing the bulb  54  into position and maintaining it in position in combination with the bayonet connection thereof. This results because of the action of the spring  46 . The contact  78  also extends radially outward and connects with the stud  16  as described. This provides the hot, or positive, side connection for the device. 
     The slug  44  may incorporate a fuse  95 . Also the plunger  40  may include a fuse  97 . Thus plunger  40  could be snap fitted or threaded at one end to sleeve  42 . 
     The plunger  40  connects with the hot side of the vehicle accessory receptacle. Plastic covered brass caps, such as caps  100  and  102 , may be provided to cover the studs  14  and  16  respectively and hold leads in position. The caps  100  and  102  may be removed so that an alligator clamp or other connector may be utilized in combination with one or the other of the studs  14  and  16 . The ground stud  14  may be utilized to provide a ground for testing circuits. Both the studs  14 ,  16  may be used to provide a completed power source for testing devices. The light or bulb  54  provides an indication that power is being provided to the various contacts and/or studs. The light bulb  54  is also positioned midway between the studs  14 ,  16  and has a diameter which is greater than the studs  14 ,  16 . Thus if a wire or rod contacts one stud (e.g. stud  14 ), it will not form a straight line connection to the other stud  16 . In this manner, the possibility of a short circuit is lessened. 
     It is to be noted, thus, that the contacts  76  and  78  extend generally radially from the axis  29  and provide a duality of function; namely, they provide a connection to the bulb  54  as well as to one of the studs  14  or  16  as the case may be. Also, they act to mechanically retain the bulb  54  in position. The bulb  54  is thus in parallel electrical connection with the studs  14  and  16 . The construction is compact, efficient and rugged. Variations of the construction may be effected. For example, the positioning of the studs about the axis  29  may be altered or amended. The particular configuration of the bulb  54  is variable and a bulb or a diode or some other indicator device may be used. Thus the invention is to be limited only by the following claims and equivalents thereof.