Abstract:
A compact fluorescent lamp which includes a compact fluorescent light source and a ballast operatively connected to and controlling operation of the light source. An outer light transmissive envelope surrounds the light source and an elastic protective shield surrounds the ballast.

Description:
BACKGROUND OF THE DISCLOSURE 
       [0001]    The present disclosure relates to a lamp assembly, and more particularly to a compact fluorescent lamp (CFL) assembly of the type having an outer envelope or bulb and a ballast circuit within the outer envelope. Even more specifically, the present disclosure relates to CFLs that include an elastic protective shield surrounding the ballast circuit within the outer envelope. It is to be appreciated, though, that the present disclosure is also amenable to other like applications. 
         [0002]    Many commercially available low-pressure discharge lamps are so-called compact fluorescent lamps (CFL). These lamps are intended to replace incandescent lamps used in a wide field of industry and home applications. The main advantages of these lamps are low-power consumption and a long lifetime. Disadvantageous is the potential of electric shocks to the consumer when handling broken CFL lamps. 
         [0003]    Accordingly, there is a need for an electric lamp, in particular a compact fluorescent lamp, with an outer envelope and a ballast circuit within the outer envelope with a safe solution for the prevention of electric shocks when the compact fluorescent lamp enclosure (plastic or glass) is compromised. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    In one aspect, the present disclosure relates to a compact fluorescent lamp (CFL) that includes a compact fluorescent light source and a ballast operatively connected to and controlling operation of the light source. The lamp further includes an outer light transmissive envelope surrounding the light source and an elastic protective shield surrounding the ballast. 
         [0005]    In another aspect, the present disclosure relates to a method of forming a compact fluorescent lamp assembly which includes providing a compact fluorescent light source, a ballast for operating the light source, an outer envelope for enclosing the light source and at least a portion of the ballast. The method further includes providing an elastic shield surrounding the ballast. 
         [0006]    A primary benefit of the present disclosure is the prevention of electric shocks when accessing broken compact fluorescent lamps. 
         [0007]    Another benefit of the present disclosure is a decrease the thickness of the glass wall of the outer envelope or bulb without a corresponding decrease in lamp performance. 
         [0008]    Still another benefit of the present disclosure resides in the lower cost of manufacture as a result of the decrease in the glass envelope. 
         [0009]    Yet another benefit is associated with the elastic property of the protective shield which offers additional stability to the lamp against mechanical vibrations. 
         [0010]    Still further advantages will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an elevational view, partly in cross-section, of a lamp assembly that includes an outer envelope and a ballast circuit within the outer envelope illustrating a protective shield surrounding the ballast circuit according to an exemplary embodiment of the present disclosure. 
           [0012]      FIG. 2  is a perspective view of a protective shield according to an exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    Shown in  FIG. 1  is a lamp assembly  100  that includes an inner assembly  102  having a light source  104  and electronics member or printed circuit board, often referred to as a ballast circuit  106 . The ballast circuit  106  is oftentimes incorporated into a lamp housing or support member  108  that supports the ballast circuit, the light source, and provides mechanical and electrical connection of the various lamp components. Enclosing the inner assembly is an outer envelope or bulb  120  which is preferably a light transmissive material, such as glass, that encloses an inner cavity dimensioned to receive the inner assembly therein. More particularly, the outer envelope adopts the general conformation of an A-line lamp having an enlarged generally spherical first portion  122  surrounding the light source  104  at one end and transitioning into a reduced dimensioned neck  124  at the other end interconnected with the spherical portion  122  through a tapered region. The outer envelope typically has a generally constant wall thickness that terminates in an opening at a first end  128  disposed adjacent a conventional electrically conductive base  138 , shown here as a threaded Edison base or shell  140 . The threaded shell  140  is separated from an end contact  142  by an insulating material  144 . The base  138 , and particularly the contact  142  and threaded region  140  thereof, are received in an associated lamp socket (not shown) to establish electrical and mechanical connection of the lamp assembly. Of course, other lamp bases such as conventional plug-in type connections that establish mechanical and electrical connection between the lamp assembly and an associated electrical socket can be used without departing from the scope and intent of the present disclosure. 
         [0014]    The light source  104  is a compact fluorescent lamp (CFL) (shown here as a spiral CFL) that includes first and second ends or legs  152 ,  154  (not shown) that extend generally parallel to one another and in a longitudinal direction that is generally parallel to a central lamp axis of the lamp assembly  100 . These legs receive electrodes at opposite ends of an elongated discharge path that includes each leg and an intermediate discharge path which in this embodiment is the helical or spiral lamp arrangement. 
         [0015]    The light source  104  and the ballast circuit  106  are held within the outer envelope  120  and relative to each other by the support  108  and further by an elastic protective shield  200 . The elastic protective shield  200  prevents electric shocks and adds protection against mechanical vibrations. The elastic protective shield  200  is dimensioned to surround at least a portion of the light source  104  and preferably surrounds an interconnection of the ballast circuit  106  with the light source. As further illustrated in  FIG. 2 , the elastic protective shield  200  has a contour that substantially conforms to a contour of the outer envelope  120 . Particularly, the shield has an open first or lower end  252  having a diameter D 1  that accommodates a lower portion of the printed circuit board/support  108 . An outer surface of the first and is dimensioned for receipt in the Edison base, although as exemplified in  FIG. 2 , the shield need not extend along he full length of the base  138 . Rather, the shield first end  252  substantially covers the printed circuit board  108 . The opening  252  is dimensioned at D 1  to receive electrical leads (unnumbered) that extend from mechanical and electrical connection with the shell  140  and contact  142 , and also mechanically and electrically connect with the printed circuit board/ballast circuit. The elastic protective shield  200  extends in surrounding relation over at least terminal ends portions of the first and second legs  152 ,  154  (not shown). The base  138  is configured to receive a terminal end of the outer envelope  120  and the elastic protective shield  200  has a first portion  250  surrounding the ballast circuit  106  and is received within the base  138 . In an exemplary embodiment, the elastic protective shield  200  has a contour that substantially conforms to a contour of the envelope  120 . 
         [0016]    The elastic protective shield  200  has a transition portion  256  that expands radially outwardly in substantially the same contour as the envelope in this region of the lamp. The transition portion  256  of the shield interconnects the narrower first end with a sidewall  258 . The sidewall  258  in turn extends along the neck  124  and thus the shield continues to be interposed between the glass of the outer envelope (which can potentially break) and the ballast. The sidewall  258  also steadily increases in dimension as they sidewall terminates at an open upper end  254  that extends to or beyond a height of the ballast. Preferably, the upper end  254  has a radial lip that extends outwardly into abutting engagement with an inner surface of the outer envelope  120  along the interface between the generally spherical portion  122  and the neck  124 . The second end  254  has an open diameter D 2  that is substantially greater than the opening D 1  at the first end and is dimensioned to accommodate the ballast  106  and associated support  108  therein, as well as the legs  152  of the CFL. 
         [0017]    The elastic protective shield  200  is formed from an electrically insulating material. In an exemplary embodiment, the elastic protective shield  200  is a silicone or other electrically insulating material. Silicone is desired because of the elastic nature of the material and the thermal stability of the material over a wide range of temperatures that may be encountered with a lamp. Incorporation of the generally annular, elastic, electrically insulating, protective shield  200  that is radially interposed between (i) the CFL legs and the outer envelope (ii) the ballast and the outer envelope, and (iii) the electrical/mechanical connection of the leads, ballast, and CFL legs, and the outer envelope. In this manner, consumers obtain additional protection from possible electrical shock if the outer envelope is inadvertently broken. Likewise, the glass wall (outer envelope) thickness may be minimized since the protection shield adds further mechanical protection. 
         [0018]    The disclosure has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the disclosure be construed as including all such modifications and alterations.