Patent Publication Number: US-2003223230-A1

Title: Compact fluorescent lamp

Description:
BACKGROUND OF THE INVENTION  
       [0001] Many residential lighting products and light fixtures are configured around incandescent bulbs. Homeowners enjoy the warm light, low initial cost, and compact size of incandescent bulbs.  
       [0002] A different type of lighting product, known as a fluorescent lamp, is also available. A fluorescent lamp comprises a ballast and a glass tube with two electrodes, one at each end. The ballast is used to regulate electric current into the lamp. When switched on, electric current passes through the ballast. Electric current then passes in an arc between the electrodes through an inert gas in the glass tube. Heat from the arc vaporizes tiny drops of mercury in the glass tube, making them produce ultraviolet light, which in turn causes a phosphor coating on the inside surface of the glass tube to glow brightly and radiate in all directions. The most common configuration of a fluorescent lamp glass tube is a straight line. When compared with incandescent bulbs, fluorescent lamps use less electricity and typically last longer. These and other qualities make fluorescent lamps desirable substitutes for incandescent bulbs.  
       [0003] The general term “compact fluorescent lamp” (CFL) applies to smaller-sized fluorescent lamps, most of which have built-in ballasts and a threaded base that may be installed in a standard incandescent bulb socket. Although the underlying physics is the same, a CFL represents quite a departure from a standard fluorescent lamp. First, the color of light produced by a CFL is nearly identical to that of an incandescent bulb. Also, the threaded bases enable them to fit most standard incandescent bulb sockets. A spiral shaped CFL with a cylindrical profile, such as shown in FIGS. 1A and 1B, is currently the most popular CFL. The drawbacks associated with fluorescent lighting products, e.g., cold-looking light, blinking, awkward sizes and high-pitched noise, have largely disappeared in modern CFLs.  
       SUMMARY OF THE INVENTION  
       [0004] In accordance with an embodiment of the present invention, a compact fluorescent lamp comprises a spiral compact fluorescent tube comprising a plurality of loops, at least one of the plurality of loops having a different cross-sectional width than a cross-sectional width of at least another one of the plurality of loops.  
       [0005] In accordance with another embodiment of the present invention, a compact fluorescent lamp comprises a spiral compact fluorescent tube comprising of a plurality of loops of non-uniform cross-sectional width.  
       [0006] Other aspects and features of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007] For a more complete understanding of the present invention, the objects and advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:  
     [0008]FIG. 1A is a front elevational view of a conventional compact fluorescent lamp and FIG. 1B is a plan view showing a distal end of the compact fluorescent lamp of FIG. 1A;  
     [0009]FIG. 2A is a front elevational view of a conventional lamp reflector and FIG. 2B is a plan view showing a distal end of the lamp reflector of FIG. 2A;  
     [0010]FIG. 3 is a front elevational view of a compact fluorescent lamp in accordance with an embodiment of the present invention;  
     [0011]FIG. 4 illustrates light radiation pattern when the compact fluorescent lamp of FIG. 1A is combined with the lamp reflector of FIG. 2A shown in phantom;  
     [0012]FIG. 5A illustrates light radiation pattern of the compact fluorescent lamp of FIG. 3 when combined with a lamp reflector in accordance with an embodiment of the present invention;  
     [0013]FIG. 5B is a plan view showing a distal end of the compact fluorescent lamp reflector of FIG. 5A; and  
     [0014]FIG. 6 is a front elevational view of a compact fluorescent lamp in accordance with an alternative embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
     [0015] The preferred embodiment of the present invention and its advantages are best understood by referring to FIGS. 1 through 6 of the drawings.  
     [0016]FIG. 1A is a front elevational view of a conventional compact fluorescent lamp  10  and FIG. 1B is a plan view showing a distal end of compact fluorescent lamp  10 . Compact fluorescent lamp  10  comprises a compact fluorescent tube  11  and a ballast  12 . FIG. 2A is a front elevational view of a conventional lamp reflector  20  and FIG. 2B is a plan view showing a distal end of lamp reflector  20 . Lamp reflector  20  comprises a housing  22  and a cover  24 .  
     [0017]FIG. 3 is a front elevational view of a compact fluorescent lamp  30  in accordance with an embodiment of the present invention. Lamp  30  comprises a compact fluorescent tube  32  coupled to a ballast  34 . Ballast  34  may be any ballast now known or later developed. Preferably, ballast  34  comprises a base  36 . Preferably, base  36  is adapted for coupling with a conventional electrical light socket (not shown), for example an electrical socket used for incandescent bulbs. In the illustrated embodiment, base  36  has a plurality of threads  38  on the outer surface thereof for coupling lamp  30  with a conventional electrical socket for incandescent bulbs.  
     [0018] Tube  32  comprises a proximal portion  39  and a distal portion  40 . Preferably, proximal portion  39  couples with ballast  34 . Distal portion  40  of tube  32  preferably has a circular spiral configuration and comprises a plurality of“loops”. Depending on the desired shape or profile, tube  32  may have a more angular spiral configuration, for example triangular, square, rectangular, and/or the like. In the illustrated embodiment, distal portion  40  comprises loops  40   1 ,  40   2  and  40   3 . Preferably, the plurality of loops of tube  32  are of non-uniform cross-sectional width or diameter. The cross-sectional width of loop  40   1 , is X 1 , the cross-sectional width of loop  40   2  is X 2  and the cross-sectional width of loop  40   3  is X 3 . As can be seen from FIG. 3, the cross-sectional width of loops  40   1 ,  40   2  and  40   3  is such that X 1 &gt;X 2 &gt;X 3 . In other words, the loop closest to ballast  34  has the largest cross-sectional width and the cross-sectional width of the loops gradually decrease such that the loop farthest from ballast  34  has the smallest cross-sectional width. If desired, in an alternative embodiment, the cross-sectional width of the loops of tube  32  may be such that the loop closest to ballast  34  has the smallest cross-sectional width and the cross-sectional width of the loops gradually increase such that the loop farthest from ballast  34  has the largest cross-sectional width.  
     [0019] As illustrated in FIGS. 1A and 1B, each loop of conventional lamp  10  is of the same cross-sectional width. As such, as shown in part by broken lines  13  in FIG. 1A, a profile of tube  11  of fluorescent lamp  10  along its longitudinal axis is substantially cylindrical. On the other hand, as illustrated by broken lines  37  in FIG. 3, a profile of tube  32  of lamp  30  along its longitudinal axis is substantially conical. Even if the length of tube  11  of lamp  10  and the length of tube  32  of lamp  30  are the same, the loops of lamp  30  are designed such that the width of the widest loop in lamp  30  is greater than the width of the loops in conventional lamp  10 . As such, light from lamp  30  is spread out over a greater area than the light from lamp  10 .  
     [0020] If desired, lamp  30  may comprise a lamp reflector  42  (FIG. 5A). Lamp reflector  42  is preferably coupled to ballast  34  or base  36 . Lamp reflector  42  has an inner reflective surface adapted to reflect light from tube  32  to augment light output. When light from tube  32  falls on the inner surface of lamp reflector  42 , the light is reflected and directed outwardly away from lamp  30 . As illustrated in FIG. 5A, lamp reflector  42  is preferably “funnel-shaped”. The shape of an outer surface of lamp reflector  42  is generally concave with respect to a longitudinal axis of lamp  40  with the cross-sectional width of lamp reflector  42  increasing linearly or non-linearly from an end proximal to ballast  34  towards an end distal from ballast  34 . Preferably, lamp reflector  42  is narrowest at the proximal end and widest at the distal end. The illustrated shape of lamp reflector  42  enables a higher light output from lamp  30  than a conventional compact fluorescent lamp with a compact fluorescent tube of substantially identical length.  
     [0021] In the illustrated embodiment of FIG. 5A, lamp reflector  42  does not comprise a cover. A substantially transparent or translucent cover  49  may be coupled to lamp reflector  42  (FIG. 6) to either hide the lamp from view or to reduce the effect of glare from the lamp, if desired. The omission of cover  49  may result in a reduction in the cost of the lamp.  
     [0022]FIG. 4 illustrates light radiation pattern when the compact fluorescent lamp of FIGURE IA is combined with a lamp reflector. In FIG. 4, lamp reflector  20  is shown in phantom. As illustrated in FIG. 4, because the loops of tube  11  are of the same cross-sectional width, a lower surface  50  of a loop  52  obstructs light emitting from an upper surface  54  of a loop  56  immediately below it, and vice versa. This is generally known in the industry as“self-shading”.  
     [0023] On the other hand, in lamp  30 , because of the staggering of the cross-sectional widths of the loops, light emitting from each loop does not become blocked or obstructed by a neighboring loop. Therefore, components of lamp  30  do not“self-shade” light emitting from the lamp. FIG. 5A illustrates light radiation pattern of compact fluorescent lamp  30  of FIG. 3 when lamp  30  comprises lamp reflector  42 . Because the loops of lamp  30  are of different cross-sectional width, light from an upper surface  60  of loop  40   2  is not obstructed by a lower surface  62  of loop  40   1  and vice versa. Instead, light from upper surface  60  is reflected off the inner surface of lamp reflector  42 . Thus, in an exemplary embodiment of the present invention, partly because of the shape of tube  32 , self-shading is reduced thereby increasing the light output.  
     [0024] Recesses of various sizes may be provided in ceilings and walls so that the lamps (whether conventional or in accordance with the present invention) may fit into the recesses and be at least partially hidden from view. The widths of these recesses are usually specified as R30 or R40, wherein a recess whose width is specified by R30 is of smaller width than a recess whose width is specified by R40.  
     [0025] It has been empirically determined that the maximum wattage of a conventional compact fluorescent lamp, such as lamp  10 , that may fit into a fixture whose width is specified by R30 is 15W, whereas the maximum wattage of a conventional compact fluorescent lamp, such as lamp  10 , that may fit into a fixture whose width is specified by R40 is 26W. On the other hand, the maximum wattage of a compact fluorescent lamp of an exemplary embodiment of the present invention, such as lamp  30 , that may fit into a fixture whose width is specified by R30 is 20W, whereas the maximum wattage of a compact fluorescent lamp of an exemplary embodiment of the present invention, such as lamp  30 , that may fit into a fixture whose width is specified by R40 is 30W.  
     [0026] It has been empirically determined that the light output of a conventional compact fluorescent lamp, such as lamp  10 , is 62 lumens/watt, whereas the light output of a compact fluorescent lamp of an exemplary embodiment of the present invention, such as lamp  30 , is 67 lumens/watt. A wattage and total light output comparison of a conventional compact fluorescent lamp and a compact fluorescent lamp in accordance with an exemplary embodiment of the present invention is given in Table I.  
                           TABLE I                                      Wattage   Total Light Output           (watt)   (lumen)                                     R30   R40   R30   R40                                             Conventional Compact   15   26   15*62 = 930    26*62 = 1612       Fluorescent Lamp       Exemplary Compact   20   30   20*67 = 1340   30*67 = 2010       Fluorescent Lamp                  
 
     [0027] The maximum overall length of a lamp includes the length of the ballast and the tube. The maximum overall length of lamp  30  is generally less than the maximum overall length of a conventional compact fluorescent lamp, such as lamp  10 .  
     [0028] Table II provides a comparison of the maximum overall length for lamps of different wattage.  
                       TABLE II                           Conventional Compact   Exemplary Compact       Wattage   Fluorescent Lamp   Fluorescent Lamp       (watt)   (mm)   (mm)                  15   140   126       18   143   131       20   146   138       23   158   142       26   162   145                  
 
     [0029] As illustrated in Table II, the maximum overall length of exemplary compact fluorescent lamp  30  is less than the maximum overall length of conventional compact fluorescent lamp  10  of comparable wattage. Because the maximum overall length of exemplary compact fluorescent lamp  30  is less than the maximum overall length of conventional compact fluorescent lamp  10 , lamp  30  does not protrude out of standard recesses whose width is denoted by R30 or R40. This results in a more pleasing configuration especially desirable and suitable for high-end interior lighting needs.  
     [0030] If desired, the maximum overall length of compact fluorescent lamp  30  may be during design by adjusting the gap between successive loops and/or by adjusting the cross-sectional widths of the loops. For example, if desired, the maximum overall length may be reduced by reducing the gap between successive loops and/or by increasing the cross-sectional widths of the loops.  
     [0031] While the invention has been particularly shown and described by the foregoing detailed description, it will be understood by those skilled in the art that various other changes in form and detail may be made without departing from the spirit and scope of the invention.