Patent Publication Number: US-2007121322-A1

Title: Lamp string

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority of Chinese Application No. 200520133151.0, filed on Nov. 28, 2005.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to a lamp string, more particularly to a decorative lamp string including flash bulbs and non-flash bulbs and a fuse arranged electrically in series with each other.  
      2. Description of the Related Art  
      In a festival or an occasion for presenting a cheerful atmosphere, such as Christmastime, a lamp string, especially one with many color bulbs, is wound on an object to be decorated, such as a Christmas tree, for providing illumination during the night. To enhance the illumination effect, flash bulbs and non-flash bulbs are often included in the lamp string, wherein, due to the fact that the use of the flash bulbs can cause a relatively large fluctuation in electrical current, safety specification of U.S. Underwriters Laboratories Inc. mandates that the flash bulb devices and non-flash bulb devices cannot be interchanged, i.e., flash bulbs cannot be used on non-flash bulb devices, in order to prevent fire accidents caused by electrical current overload due to use of the flash bulbs in the non-flash bulb devices. As a consequence, different specifications and different manufacturing processes in manufacturing flash bulb devices and non-flash bulb devices are required, which results in an increase in manufacturing costs.  
     SUMMARY OF THE INVENTION  
      Therefore, the object of the present invention is to provide a lamp string capable of overcoming the aforesaid drawback associated with the prior art.  
      Accordingly, a lamp string of the present invention comprises: a plug; a first electric wire connected electrically to the plug; a second electric wire; a fuse unit including a first connector having a first housing and a first conductive contact mounted in the first housing and connected electrically to the first electric wire, a second connector having a second housing and a second conductive contact mounted in the second housing and connected electrically to the second electric wire, the second housing being detachably connected to the first housing to define an enclosed space therebetween, the first and second conductive contacts being exposed within the enclosed space, and a fuse mounted in the enclosed space and connected electrically to the first and second conductive contacts; a plurality of bulb mounting units arranged together with the fuse electrically in series with each other and connected electrically to the second wire and the plug; and a plurality of flash bulbs and non-flash bulbs mounted selectively and respectively on the bulb mounting units. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:  
       FIG. 1  is a schematic view of the first preferred embodiment of a lamp string according to the present invention;  
       FIG. 2  is a schematic view of the second preferred embodiment of the lamp string according to the present invention; and  
       FIG. 3  is an exploded partly sectional view of a fuse unit of the first preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Before the present invention is described in greater detail with reference to the accompanying preferred embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the disclosure.  
      Referring to  FIGS. 1 and 3 , the first preferred embodiment of a lamp string  1  according to the present invention is shown to be adapted for use as a Christmas lighting set, and includes: a plug  4 ; a first electric wire  71  connected electrically to the plug  4 ; a second electric wire  72 ; a fuse unit  6  including a first connector  60  having a first housing  61  and a first conductive contact  611  mounted in the first housing  61  and connected electrically to the first electric wire  71 , a second connector  65  having a second housing  64  and a second conductive contact  621  mounted in the second housing  64  and connected electrically to the second electric wire  72 , the second housing  64  being detachably connected to the first housing  61  to define an enclosed space  66  therebetween, the first and second conductive contacts  611 ,  621  being exposed within the enclosed space  66 , and a fuse  63  mounted in the enclosed space  66  and connected electrically to the first and second conductive contacts  611 ,  621 ; a plurality of bulb mounting units  8  arranged together with the fuse  63  electrically in series with each other and connected electrically to the second wire  72  and the plug  4 ; and a plurality of flashbulbs  2  and non-flash bulbs  3  mounted selectively and respectively on the bulb mounting units  8 .  
      Referring again to  FIG. 3 , the first housing  61  has an outer threaded end  612 , and the second housing  64  has an inner threaded end  642  that engages threadedly the outer threaded end  612 . The second connector  65  further includes a contact-mounting seat  62  that is mounted movably in the second housing  64  and that defines a recess which forms a portion of the enclosed space  66 . The second conductive contact  621  is mounted in the recess, and the fuse  63  has one contact end extending into the recess to contact the second conductive contact  621 , and the other contact end contacting the first conductive contact  611 .  
      Referring back to  FIG. 1 , each of the bulb mounting units  8  includes a bulb seat  81  and a bulb base  82  mounted to the bulb seat  81  and adapted for mounting of a selected one of the flash bulbs  2  and the non-flash bulbs  3 .  
      Each non-flash bulb  3  includes a filament  31  that is not designed to deform with variations in operating temperature, whereas each flash bulb  2  includes a filament  21  that is designed to deform with variations in operating temperature, thereby resulting in electrical connection and disconnection so as to generate a flashing effect. The lamp string  1  of this invention allows the non-flash bulbs  3  and the flash bulbs  2  to be interchanged on the same bulb mounting unit  8 , thereby eliminating the aforesaid drawback associated with the conventional lamp string.  
      Referring to  FIG. 2 , the second preferred embodiment of the lamp string  1  according to this invention differs from the previous embodiment in that a third electric wire  73  is electrically connected to the first contact  611  (see  FIG. 3 ), and that a socket  5  is electrically connected to the third electric wire  73  and one of the bulb mounting units  8  that is remote from the plug  4  for coupling electrically to another lamp string (not shown).  
      The fuse  6  will break when electrical current flowing in the lamp string  1  exceeds a rated value so as to prevent fire accidents from taking place.  
      While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangement included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.