Abstract:
A snap-in lamp for an electric light string includes a lamp base housing a light bulb and a lamp holder. The lamp base is removably and frictionally housed in the lamp holder. The light bulb has a filament that illuminates the light bulb when electrical current passes through the filament. The light bulb filament is connected to a bottom portion of the lamp base by a pair of opposed lead wires. The lamp holder is dimensioned to frictionally receive and removably house the lamp base. The lamp holder includes a metal conductor strap and a non-conductive strap holder that provide a path for the continued flow of current through the lamp even when the lamp base is removed from the lamp holder. The lamp is more useful than conventional lamps by virtue of the ability to preserve the closed circuit even when one or more lamp bases are removed from their respective lamp holders.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a lamp for an electric light string. More particularly, the present invention relates to a lamp that is capable of maintaining an electrical connection to the remainder of the light string even when an individual light bulb is removed from the string. 
         [0003]    2. Description of the Prior Art 
         [0004]    Lamps for electric light strings, such as holiday lights, are well known. They typically include a removable light bulb mounted in a lamp base and a lamp holder or light socket assembled into the light string which receives the light bulb base. The filament in the light bulb can fail over time, however, and the bulb must be replaced. In the conventional lighting, when the filament fails and the bulb remains in the string, or when the bulb is removed from its socket for replacement, the closed path for the flow of electrical current is interrupted and the remainder of the lamps in the string will no longer be illuminated. 
         [0005]    U.S. Pat. No. 6,257,740 addresses the above-described problem by disclosing a lamp designed to maintain a closed circuit even when a bulb is removed from the string. The &#39;740 patent discloses a lamp having a light bulb, a light bulb base, and a light socket with two biased spring terminals. When the light bulb base is seated in the socket, the spring terminals are forced apart by a projecting separator on the light bulb base so as to provide contact between each of the spring terminals and a corresponding lead wire on the bottom of the light bulb base. This connection between the spring terminals and the light bulb base lead wires provides the path for electrical current to light the light bulb. When the light bulb base is removed from the light socket, the spring terminals spring together so as to contact one another. This connection between the spring terminals then provides the closed path for electrical current to flow so that the remainder of the light string receives current even when the light bulb has been removed from its light pocket. 
         [0006]    A problem associated with the device disclosed by the &#39;740 patent, however, is that after the light bulb base has been housed in the socket for a period of time, the spring terminals do not always fully spring back together upon removal of the light bulb base from the socket. That is, the spring terminals may partially spring together, but not to the extent necessary to contact one another. As a result, the light string is short circuited, and none of the lamps in the string is illuminated. 
         [0007]    Another design that seeks to overcome the short-circuiting problem of conventional light strings is a prior art lamp having a light bulb, a light bulb base, and a light socket with two opposed terminals. In this design, the upper ends of the terminals extend across the width of the socket to approach, but not contact, one another. The socket also has a compressible metal coil spring aligned vertically on a post in the center of the socket. When the light bulb base is seated in the socket, the coil spring is compressed by a projection on the light bulb base, and each of the terminals contacts a corresponding lead wire on the bottom of the light bulb base. This connection between the terminals and the lead wires of the light bulb base provides the path for electrical current to light the bulb. When the light bulb base is removed from the light socket, the coil spring expands upward so as to contact each end of the opposed terminals. The uncompressed spring forms a bridge connection between the terminals and provides the closed path for electrical current to flow so that the remainder of the light string continues to receive current. 
         [0008]    A problem associated with the above prior art device, however, is similar to that associated with the device of the &#39;740 patent. That is, after the light bulb base has been housed in the socket over a period of time, the coil spring loses its resiliency and does not expand sufficiently to contact each end of the socket terminals. As a result, the light string is short circuited, and none of the lamps in the string is illuminated. In addition, since the coil spring is of iron construction, it will create a certain amount of heat while bridging the terminals. This generated heat can lead to overheating of the lamp, and ultimately, failure of the light string. 
       SUMMARY OF THE INVENTION 
       [0009]    In order to overcome the above-described draw-backs associated with prior art lamps, the present invention provides a snap-in lamp for a light string which includes generally a light bulb, a lamp base and a lamp holder. The light bulb is mounted in the lamp base which is removably and frictionally received in the lamp holder. The light bulb has a filament that illuminates the light bulb when electrical current passes through the filament. The light bulb filament is connected to a bottom portion of the lamp base by a pair of opposed lead wires. 
         [0010]    The lamp base has an upper section and a lower section that depends therefrom. A pair of tapered prongs extend downwardly from the bottom of the lower section. Each prong includes a corresponding dumet lead wire that terminates at and contacts, at an uppermost end or light bulb-end of each dumet lead wire, a corresponding end of the light bulb filament. 
         [0011]    The lamp holder includes a housing that defines a socket dimensioned to receive the lamp base. A pair of electrical terminal wires extend into opposite sides of the socket and terminate in a pair of opposed terminals. A pair of opposed socket lead wires extend upwardly from the corresponding terminals and terminate along opposed side walls of the socket. 
         [0012]    It is, therefore, an object of the present invention is to provide a snap-in lamp that maintains the light string in a closed circuit mode even when one or more light bulb bases are removed from their respective sockets. Therefore, according to a preferred embodiment of the present invention, the lamp holder includes a metal conductor strap that provides a path for the continued flow of current through the lamp even when the lamp base is removed. The metal conductor strap is mounted on a non-conductive strap holder and has an arch or inverted U-shape such that the strap can be seated in and supported by the strap holder. The strap has a pair of opposed contact legs capable of engaging the corresponding terminals when the light bulb is removed. The strap has elastic properties such that the contact legs are capable of spring-like flexing both toward and away from the strap holder. 
         [0013]    Another object of the present invention is to provide a lamp base that has two prongs which extend downwardly therefrom for insertion into corresponding slots or receptacles, so that each of the two prongs can contact and move a respective contact leg of the conductor strap. Therefore, according to the preferred embodiment of the present invention, the socket of the lamp holder is configured to slidably and frictionally engage and house the lamp base with each prong extending into a slot located between each terminal and the strap holder. Each of the prongs thus slidably engages the respective contact leg of the conductor strap and disengages the contact leg from contact with its respective terminal. 
         [0014]    Hence, when the lamp base is housed in the lamp holder, each prong of the lamp base is inserted in a slot or receptacle in the socket and each contact leg is accordingly compressed inwardly toward the strap holder and out of contact with the terminal. In this “lamp base-in” configuration, therefore, electrical current flows from the terminal to the socket lead wire, to the dumet lead wire, and to the filament. Current then flows from the opposed end of the filament to the opposed dumet lead wire, to the opposed socket lead wire, to the opposed terminal, and out of the lamp to the next lamp in the string. 
         [0015]    The contact legs are biased with sufficient force so as to spring apart from one another when not compressed by the prongs of the lamp base. Therefore, when the lamp base is removed from the lamp holder, the prongs are withdrawn from the socket slots and each contact leg accordingly springs outward away from the strap holder and into contact with its respective terminal. In this “lamp base-out” configuration, electrical current flows from the terminal to the contact leg, through the strap to the opposed contact leg, to the opposed terminal, and out of the lamp to the next lamp in the string. 
         [0016]    Because the metal conductor strap possesses the aforementioned spring-like elasticity, even after the lamp base has been housed in the lamp holder for an extended period of time with the contact legs compressed and out of contact with the terminals, upon removal of the lamp base from the lamp holder, the contact legs will spring outwardly from the strap holder so as to once again contact the terminals and complete the circuit. 
         [0017]    By virtue of the above-described configuration, the present light string lamp is more reliable than prior lamps because of the ability to maintain the closed circuit even when one or more lamp bases are removed from their respective lamp holders. 
         [0018]    Other objects of the present invention are to provide a lamp that can be easily fabricated from readily available materials, that is reliable and has a long service life, that is safe for its intended use, and that provides for easy replacement of one or more bulbs while the light string remains in operation. Each of these objects is attained with the present invention. 
         [0019]    These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like reference numbers refer to like parts throughout. The accompanying drawings are intended to illustrate the invention, but are not necessarily to scale. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a cut-away perspective view of a lamp according to a preferred embodiment of the present invention with the light bulb and lamp base removed from the lamp holder. 
           [0021]      FIG. 2  is a perspective view of the lamp shown in  FIG. 1  with the lamp base inserted in the lamp holder. 
           [0022]      FIG. 3  is a perspective view of the strap holder of the lamp holder shown in  FIG. 1 . 
           [0023]      FIG. 4  is a perspective view of the conductor strap of the lamp holder shown in  FIG. 1 . 
           [0024]      FIG. 5  is a perspective view of the lamp base shown in  FIG. 1 . 
           [0025]      FIG. 6  a perspective view of the housing of the lamp holder shown in  FIG. 1 . 
           [0026]      FIG. 7  is a cross-section view of the lamp shown in  FIG. 2  taken substantially along line  7 - 7  shown therein. 
           [0027]      FIG. 8  is a cross-section view of the lamp shown in  FIG. 2  taken substantially along line  8 - 8  shown therein. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Although only preferred embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. 
         [0029]    Also, in describing the preferred embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art, and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
         [0030]    Referring to  FIG. 1  of the drawings, a snap-in lamp according to a preferred embodiment of the present invention is generally designated by reference numeral  10 . The lamp  10  includes generally a lamp base  20  that is removable from a lamp holder, generally designated by reference numeral  30 . The lamp base  20  houses a light bulb  18 . The light bulb  18  has a filament  15  that illuminates the light bulb when electrical current passes through the filament. 
         [0031]    The lamp base  20  has an upper section  21  and a lower section  22  that depends therefrom. A pair of tapered prongs  23  extend downwardly from the lower section  22 , and each prong  23  includes a corresponding dumet lead wire  24 . Each dumet lead wire  24  has one end embedded in the base  20  which is in electrical contact with a corresponding end of the light bulb filament  15 . The other end  24 A of dumet lead wires  24  are exposed and extend upwardly on opposite sides of the lamp base lower section  22 . The outside surface of each prong  23  tapers from top to bottom so that the prong  23  is narrowest at its bottom end. The angular shape of the prongs  23  facilitates their slidable engagement into the lamp holder  30 , as will be described hereinafter. 
         [0032]    The lamp holder  30  includes a housing  31  which defines a socket generally designated by referenced numeral  36 , that is dimensioned to receive the lamp base  20 . A pair of electrical terminal wires  32 , preferably of conventional copper construction, extend into opposite sides of the socket  36  and terminate in a pair of opposed terminals  33 , also preferably of conventional copper construction. A pair of opposed socket lead wires  34  extend upwardly from the corresponding terminals  33  and terminate along opposed side walls of the socket  36 . When the lamp base  20  is inserted into the socket  36 , each socket lead wire  34  contacts the corresponding exposed end  24 A of dumet lead wire  24 . 
         [0033]    The terminal wires  32  and terminals  33  are separated by an insertable non-conductive strap holder  40 , which has mounted at the top thereof a metal conductor strap  50 . As described in greater detail below, when power is “on” between terminal wires  32  and the lamp base  20  is housed in the lamp holder  30 , electrical current flows from one terminal wire  32  through its terminal  33  to the socket lead wire  34 , to the dumet lead wire  24  and to the filament. The current follows the reverse path on the opposed side of the lamp. When lamp base  20  is removed from the socket  36 , the conductor strap  50  contacts and makes electrical connection with the opposed terminals  33 , thus completing the circuit so that current can flow from one terminal wire  32  to the opposed terminal wire  32 . 
         [0034]    As shown in  FIG. 1  and in detail in  FIG. 3 , the non-conductive strap holder  40  is dimensioned to house and support the metal conductor strap  50 . The strap holder  40 , preferably of constructed of a molded polymeric or other suitable material, includes a conductor strap recess  41  and a pair of opposed terminal wire recesses  42 . Once inserted in the lamp holder  30 , the strap holder  40  is held in place by contact among the opposed terminal wires  32 , the corresponding opposed terminal wire recesses  42  and the inside wall of the housing  31 , as described further below. 
         [0035]    As shown in  FIG. 4 , the metal conductor strap  50  has an arch or inverted U-shape such that the strap  50  can be seated in the recess  41  and supported by the strap holder  40 . The strap  50  has a seating face  51  that engages the recess  41 , and a pair of opposed contact legs  52  capable of engaging the corresponding terminals  33 . Preferably of copper construction to match that of the terminal wires  32  and the terminals  33 , the strap  50  has elastic properties such that the contact legs  52  are capable of spring-like flexing both toward and away from the strap holder  40 . 
         [0036]    The socket  36  of lamp holder  30  is configured to frictionally engage and house the lamp base  20  when the lamp base is slide into the lamp holder socket  36 . More specifically, the upper section  21  of lamp base  20  preferably has a generally oval shape in cross-section, which is matched by the open upper end  51  of the housing  31 . See  FIG. 7 . This oval shape facilitates alignment of the lamp base  20  for insertion into the lamp holder  30 . The lamp base lower section  22  has a generally rectangular shape in cross-section which is configured to frictionally fit within the top of lower section  54  of the housing  31 . See  FIG. 8 . The top of lamp base  20  also preferably has a protruding rim  56  at its upper edge which engages the upper edge  58  of housing  31  to ensure that the lamp base does not over-extend into the lamp holder. The lamp base upper section  21  also preferably has a plurality of raised ribs  60  extending axially around the outer surface. The ribs  60  facilitate sliding movement, with less friction of the lamp base upper section  21  within the lamp holder upper end  51 . 
         [0037]    The lower section  54  of the housing  31  of the lamp base  30  has flattened sides  35  which form a generally rectangular shape, with rounded sides  64 . Lower section  54  is thus configured to frictionally receive the lower section  22  of lamp base  20  in the upper end  66  of section  54 . The lamp base lower section  22  also has raised axial ribs  69  to reduce friction when section  22  is inserted into or extracted from end  66  of the housing lower end. The lower end  68  of housing section  54  frictionally receives the strap holder  40  with the opposed terminal wires  32  secured in recesses  42  of the strap holder  40  against the inside surfaces  70  of the rounded sides  64 . 
         [0038]    The flattened sides  35  in the lower section  54  of the lamp holder  30  serve as convenient gripping surfaces for a thumb and forefinger to hold the lamp holder when inserting or extracting the light bulb and lamp base from the socket  36  of the lamp holder. The lamp base  20 , the lamp holder housing  31  and the strap  40  can be made from any suitable injection molded polymeric material, such as PE (polyethylene), PP (polypropylene), PVC (polyvinyl chloride), PET (polyethylene terephthalate), ABS (acrylonitrile butadiene styrene), AS (acrylonitrile styrene), PS (polystyrene), PC (polycarbonate), etc., for ease of manufacture and desired rigidity with some elasticity to achieve the requisite frictional engagement of the component parts. Polypropylene is currently preferred. 
         [0039]    When the lamp base  20  is inserted into the lamp holder  30 , the lamp base lower section  22  is seated in the lower section  54  of the housing  31  such that each of the prongs  23  is inserted into a corresponding slot or receptacle  37  located between each terminal  33  and, the strap holder  40 . Each of the prongs  23  slidably engages the respective contact leg  52  of the conductor strap  50  and disengages the contact leg  52  from physical, and thus electrical, contact with its respective terminal  32 . That is, as shown in  FIG. 2 , when the lamp base  20  is housed in the lamp holder  30 , each prong  23  is inserted into a slot or receptacle  37  and each contact leg  52  is accordingly compressed inward toward the strap holder  40  and out of contact with the terminal  33 . In this “lamp base-in” configuration, therefore, electrical current flows from the terminal  33  to the socket lead wire  34 , to the dumet lead wire  24 , and to the filament. Current then flows from the opposed end of the filament to the opposed dumet lead wire  24  through the opposed socket lead wire  34  to the opposed terminal  33 , and out of the lamp  10  to the next lamp in the string. 
         [0040]    The contact legs  52  are biased outwardly with sufficient force so as to spring apart from one another when not compressed by the prongs  23 . Therefore, as shown in  FIG. 1 , when the lamp base  20  is removed from the lamp holder  30 , each prong  23  is withdrawn from its corresponding slot  37  and each contact leg  52  accordingly springs outward away from the strap holder  40  and into contact with the terminal  33 . In this “lamp base-out” configuration, electrical current flows from the terminal  33  to the contact leg  52 , through strap  50  to the opposed contact leg  52 , to the opposed terminal  33 , and out of the lamp  10  to the next lamp in the string. 
         [0041]    Therefore, the strap  50  necessarily possesses the aforementioned spring-like elasticity such that even after the lamp base  20  has been housed in the lamp holder for an extended period of time with the contact legs  32  compressed and out of contact with the terminals  33 , upon removal of the lamp base  20  from the lamp holder  30 , the contact legs  32  will spring outwardly from the strap holder  40  so as to once again contact the terminals  33  and complete the circuit. That is, the strap  50  must have an elastic limit such that even after the contact legs  32  have been compressed for an extended period of time, upon removal of the lamp base, the contact legs  32  are not permanently deformed but instead spring outward, returning strap  50  to the uncompressed shape shown in  FIG. 4 . 
         [0042]    According to another embodiment of the invention, a light string includes a plurality of the above-described lamps  10  and the associated interconnecting wiring and power supply plug. In an optional embodiment, the light string includes a power plug receptacle on the end of the string opposite the power supply plug. This feature enables individual light strings to be connected in series. 
         [0043]    The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes may readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation described and shown. Accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the invention as defined by the following claims.