Abstract:
A light for use in light strings has a deeper socket, a longer base and longer Dumet wires than a standard socket, base, and Dumet wires so that the standard bases and bulbs will not operate in the non-standard socket. Furthermore, the base and sockets are keyed so that they are restricted to at most two orientations with respect to each other and cannot be twisted with respect to each other.

Description:
CROSS REFERENCE TO RELATED PATENTS 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     The present invention relates to strings of lights and, in particular, to special application lights used in strings of lights, such as fuse lights and flicker lights. In the present specification, the word light will be used to denote the combination of a bulb, bulb base (or simply “base”), and socket. 
     Light strings such as the type used to decorate Christmas trees may include sets of 50 or 100 miniature lights arranged electrically in series. In addition to standard lights used in these sets, which meet industry standards set by Underwriters Laboratories (UL Standard 588, in particular), manufacturers have created lights that serve special functions, such as flicker or twinkle lights and fuse lights. While in some cases these special application bulbs may be used in any socket in the light string and in any number, in other cases, the manufacturer may want to limit the number of these special application lights in the string, use them only in special sockets, and even to confine them to specific locations. Under these types of circumstances, the manufacturer may have to anticipate that consumers might inadvertently or through ignorance attempt to place bulbs in the wrong sockets of the light string, and, accordingly, incorporate features into their light string designs to prevent these actions. 
     One way for manufacturers to achieve this goal of limiting the number and the location of these special application lights in a light string is to make them non-removable from their sockets. However, a determined user, with sufficient effort, can sometimes remove so-called non-removable bulbs. However, this determined consumer may then be confronted by a pair of bare, live wires. 
     Another way to limit the location and type of special application lights in a light string is to make special application sockets only receive the special application bulb or make special application sockets so that, although they will receive standard bulbs, only special application bulbs will be operable. In addition, manufacturers in some cases will also design special application bulbs so that they will not work in standard sockets. 
     Another, different, problem facing manufacturers and users of conventional light strings, is that the bulbs can be twisted within their sockets, that is, rotated about their long axis with respect to the sockets. In a conventional set, when a conventional bulb is twisted enough, it will fail. When one light in a conventional series circuit fails, a shunt in the light will enable the socket to pass the electrical current through to the next light so the balance of the light string continues to function. However, the current being carried by remaining lights in the string will be incrementally higher, and the light incrementally brighter, than before. Pranksters have been known to twist one bulb after another in a light string, with the remaining lights getting progressively brighter, until the whole light string fails. This form of amusement creates a dangerous fire hazard. 
     There remains a need for better lights and better special application lights in particular. 
     SUMMARY OF THE INVENTION 
     According to its major aspects and briefly recited, the present invention is a light for special applications. The special application light has a bulb, a base and a socket that are not interchangeable with a standard bulb, base and socket. The present bulb and base will not fit into a standard socket and the present socket will not receive a standard bulb and base. If a standard bulb and base are somehow forced into the present socket, the standard bulb will not operate. If the present bulb and base are somehow forced into a standard socket, it will be clear that they are not intended to be used together because the base will not fit and will be too long for the socket. Furthermore, the present base and socket are designed so that the base cannot be twisted with respect to the socket when the base is seated in the socket. 
     The present special application socket is longer than a standard socket and keyed to fit a longer light base. The Dumet wires of the present light are longer in order to be able to make electrical contact with the electrical wire contacts in the deeper special application base and socket of the present design. Standard length Dumet wires are too short to make contact with the electrical wire contacts in the present special application socket. 
     An important advantage of the present invention is that the bulb base is easily removable from the socket. Prior art bulb bases that are made to be not removable, and can invite the use of excessive force by users who try to remove them, which may result in a possible safety hazard. In the case of the present special application sockets, the lamp socket and base are not tapered but are straight, so that the base can be removed from the socket. 
     An important feature of the present invention is the use of a longer socket. In addition to being important to preventing a standard bulb from being operable in the present special application socket, a longer socket looks different than a standard socket and can thus be visually identified quickly. 
     Still another important feature of the present invention is the keying of the light base and socket to prevent twisting of one with respect to the other. Keying means that complementary patterns of slots and grooves are formed on the socket and base to make it impossible for one to be rotated with respect to the other when the base is fully seated in the socket. Second, the keying prevents the interchanging of standard bulbs and sockets with the present special application bulbs and sockets. Third, the keying helps maintain the alignment of Dumet wires with electrical contacts within the socket and prevents their misalignment when bases are inserted into sockets. 
     These and other features and their advantages will be apparent to those skilled in the art of light string design from a careful reading of the Detailed Description of Preferred Embodiments accompanied by the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  is a perspective, exploded view of a prior art, standard miniature light for use in a light string; 
         FIG. 2  is a perspective, exploded view of the present special application light for use in a light string, according to a preferred embodiment of the present invention; 
         FIG. 3A  is a perspective view of the light socket showing the keying, according to a preferred embodiment of the present invention; 
         FIG. 3B  is a side view of the light base according to a preferred embodiment of the present invention; 
         FIGS. 4A and 4B  are side, partially cutaway views of the present bulb, base and socket ( FIG. 4A ), according to a preferred embodiment of the present invention, and a standard bulb and base forced into the present socket; and 
         FIG. 5  is a partial view of a string of lights having plural standard lights and at least one special application light, according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is a special application light. The present light has a bulb, a base and a socket. The base and bulb will only be operable in the present socket. Although the bulb and base are easily removable from the socket without undue effort, the present bulb and base cannot be twisted with respect to the present socket once seated. Furthermore, if a standard bulb and base were somehow forced into the present socket, a feat that requires considerable effort, the standard bulb and base would not function. Finally, the present socket, being longer than a standard socket, is easily visually distinguished from the standard socket. 
     Referring now to  FIGS. 1 and 2 , there is shown an exploded perspective view of a prior art light  10  in  FIG. 1  and of the present light  30  in  FIG. 2 , according to a preferred embodiment of the present invention. These exploded perspective views highlight the differences between the prior art light and the present light. 
     In  FIG. 1 , light  10  has a bulb  12 , typically made of glass or plastic, with a first Dumet wire  14  and a spaced-apart second Dumet wire  16  extending out of bulb  12 . Inside bulb  12 , Dumet wires  14 ,  16 , are connected in series across a filament, in accordance with prior art bulb design. The portions of first and second Dumet wires  14 ,  16 , extending outside of bulb  12  are inserted through a base  18  and, once in place, are bent back toward the outside of base  18  on opposing sides of a divider  20 . When bulb  12  and base  18  are inserted into a socket  22 , first and second Dumet wires  14 ,  16 , come into electrical contact with electrical terminals located on the walls inside socket  22 . 
     Significantly, the outside of base  18  and the inside of socket  22  in prior art light  10  are tapered by a few degrees so that they can be forced together tightly enough to keep out rainwater. In addition, this prior art design has two consequences. First, it allows use of old, worn, out of tolerance molds, and, second, it sometimes results in base  18  that is so tightly stuck into socket  22  that they require more pull force than it takes to separate socket  22  from the live electrical wires leading into it. As a consequence, the user, in attempting to separate base  18  from socket  22 , may be exposed to an electrical hazard of the wires instead. 
     In  FIG. 2 , a bulb  32  with longer first and spaced-apart second Dumet wires  34 ,  36 , extending therefrom are inserted through base  38 , and, once fully inserted, are bent toward the outside of base  28  on opposing sides of a divider  40 , as in the prior art light  10 . However, first and second Dumet wires  34 ,  36 , are longer, preferably 5 mm longer, and base  38  is also longer, again by preferably 5 mm. Socket  42  is also longer to receive the longer base  38  and the inside of socket  42  and outside of base  38  are straight and untapered so that they separate with less force than socket  42  separates from the wires leading into socket  42 . 
     Additionally, while both base  18  and base  38  are friction fitted to their respective sockets  22 ,  42 , base  18  has a smooth collar  50  and socket  22  has a smooth bore  52 . In contrast, base  38  is keyed to allow socket  42  to be inserted easily only in fixed orientations so that it cannot be twisted. In particular, base  38  and socket  42  are keyed so that the possible orientations of one with respect to the other are not infinite, as in the prior art light of  FIG. 1 , but finite, preferably limited to two orientations 180° apart. This limitation of orientations is achieved by using a combination of ribs  54  and grooves  56  on base  38  and grooves  58  and ribs  60  on socket  42 . See also  FIGS. 3A and 3B . 
       FIG. 4A  illustrates, in a partially cut away side view of the present special application light  30  ,the fit of bulb  32  and base  38  into socket  42 . First and second Dumet wires  34 ,  36  extend downward through holes  68 ,  70 , respectively, in base  38  and emerge from the bottom of base  38  where they are folded outwardly against the outsides of base  38 . Inside socket  42  are two terminals  72 ,  74  that are connected to wires  76 ,  78 , of the light string. When base  38  is inserted into socket  42 , first and second Dumet wires  34 ,  36  come into electrical contact with terminals  72 ,  74 , respectively, and electrical current can flow from wire  76  to terminal  72 , to first Dumet wire  34 , and across a filament  80  inside bulb  32  to second Dumet wire  36  to second terminal  74  and on to second wire  78 . 
     As illustrated in  FIG. 4B , if somehow through the use of considerably force, a standard base  18  with a smooth collar  50  were inserted into socket  42  notwithstanding the interference of ribs  60  with base  18 , base  18  would be too short and first and second Dumet wires  14 ,  16 , would be too short, as shown, to reach terminals  72 ,  74  to allow electrical current to flow from wire  76  to wire  78  via first and second Dumet wires  14 ,  16 , and a filament  80 ′ in bulb  12 . 
     Thus, ribs  54  and grooves  56  of base  38  and the correspondingly keyed grooves  58  and ribs  60  of socket  42  prevent base  38  from being twisted with respect to socket  42 . Moreover, they assist in making sure that first and second Dumet wires  34 ,  36 , are in physical and, hence, electrical contact with first and second terminals  72 ,  74 . Also, by making first and second Dumet wires slightly longer, making base  38  also slightly longer, and making socket  42  slightly deeper, all about 5 mm longer, only the combination of the present bulb, base and socket is a working combination. Standard light bulb  12  and base  18  will not operate even if forced into socket  42  as shown because first and second Dumet wires  14 ,  16 , will not reach first and second terminals  72 ,  74 . 
       FIG. 5  illustrates a portion of a string of lights  30  with the present special application light  32  plural standard lights  12 . It will be clear that the special application lights  32  are slightly larger, and longer in particular by preferably about 5 mm. 
     It is intended that the scope of the present invention include all modifications that incorporate its principal design features, and that the scope and limitations of the present invention are to be determined by the scope of the appended claims and their equivalents. It also should be understood, therefore, that the inventive concepts herein described are interchangeable and/or they can be used together in still other permutations of the present invention, and that other modifications and substitutions will be apparent to those skilled in the art from the foregoing description of the preferred embodiments without departing from the spirit or scope of the present invention.