Abstract:
A discharge lamp including an arc tube having an elongated body enclosing a discharge chamber. The discharge chamber receiving first and second electrodes therein for forming an arc discharge in the discharge chamber. The lamp also including an outer envelope having an envelope cavity therein. A support member is received in the envelope cavity for supporting the arc tube. A containment member extends from the support member and is received around at least a portion of the elongated body of the arc tube. Additionally, a method of manufacturing a discharge lamp is disclosed.

Description:
[0001]     The present invention relates to the art of discharge lamps and, more particularly, to an improved device for containing arc tube ruptures in such lamps.  
       BACKGROUND OF THE INVENTION  
       [0002]     Arc tubes in high-intensity discharge (HID) lamps operate at a high temperature (on the order of approximately 1000° C. and greater) and high pressure (on the order of approximately 5 atmospheres and greater). On occasion, the arc tube ruptures. Containment devices for absorbing the kinetic energy of fragments from ruptured arc tubes are well known and commonly take various forms and/or configurations. However, these containment devices suffer from a number of shortcomings and disadvantages that can limit the effectiveness of the same. Additionally, these shortcomings and disadvantages ultimately increase the costs associated with the manufacture and production of the resulting lamp. For example, quartz shrouds are commonly used as containment devices. A quartz shroud commonly takes the form of a hollow cylinder and is positioned along the exterior of the arc discharge tube. The shroud can typically be supported around the arc tube in any suitable manner. It is well known that arc discharge tubes made from quartz generally fracture into relatively small particles having minimal kinetic energy due, at least in part, to the relatively small mass of these fragments. As such, containment devices, such as quartz shrouds, are suitable for absorbing the kinetic energy of these particles. However, arc discharge tubes formed from ceramic materials commonly fracture into a few relatively large pieces. Certain known containment devices, such as quartz shrouds, are less well suited for absorbing the kinetic energy of these objects, as the same can cause the rupture of the shroud.  
         [0003]     In an effort to overcome this issue, containment wires have been wrapped or otherwise extended around the exterior of the quartz shroud. Generally, the containment wire sufficiently absorbs the kinetic energy of the relatively large ceramic pieces. However, the wire acts on these pieces only after the same have exceeded the envelope of the quartz shroud. As such, the formation of quartz fragments remains an issue. The use of quartz shrouds for containment has the additional disadvantage of adding considerable cost and weight to the lamp.  
         [0004]     In other arrangements, the containment wire is supported directly on the ceramic arc discharge tube, thus entirely eliminating the quartz shroud the lamp. Typically, arc discharge tubes have legs that are of a smaller diameter than the elongated body of the arc tube. As such, the containment wire in known arrangements is wrapped around one of the legs, along the elongated body of the arc tube, and then around the other leg. However, because the legs are a smaller diameter than the body of the arc tube and the wires are wrapped around both the body and each of the legs, the wire cannot typically be prefabricated and simply assembled onto the arc tube. Rather, the containment wire is usually physically wrapped, wound or otherwise formed around the body and legs of the arc discharge tube. One disadvantage is that such arrangements are difficult and expensive to manufacture. This is due, at least in part, to the handling requirements that are commonly associated with arc discharge tubes. As such, significant care is commonly exercised during the wrapping or forming operation. Such processes are inherently less efficient than an arrangement in which the containment wire is prefabricated and later associated with the arc tube during the assembly process.  
       SUMMARY OF THE INVENTION  
       [0005]     A high-intensity discharge lamp is provided that includes an arc tube, an outer envelope having an envelope cavity therein, a support member received in the envelope cavity for supporting the arc tube, and a containment member extending from the support member. The arc tube has an elongated body enclosing a discharge chamber. The discharge chamber receives first and second electrodes therein for forming an arc discharge in the discharge chamber. The containment member is received around at least a portion of the elongated body of the arc tube.  
         [0006]     A method of manufacturing a high-intensity discharge lamp is also provided. The method includes the steps of supplying an arc tube having an elongated body enclosing a discharge chamber, a support member for supporting the arc tube, a containment member for containing the arc tube in the event of a rupture, and an outer envelope having an envelope cavity. The elongated body of the arc tube has an exterior wall. Other steps include forming the containment member into an arrangement suitable for containing the arc tube and positioning the containment member along the exterior wall of the elongated body of the arc tube. Further steps include supporting the arc tube on the support member, attaching the containment member to the support member, and enclosing the support member, the arc tube and the containment member within the envelope chamber of the outer envelope. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a side elevation view of a lamp having a containment member of the present invention.  
         [0008]      FIG. 2  is a side elevation view of the arc discharge tube and containment member arrangement shown in  FIG. 1 .  
         [0009]      FIG. 3  is a side elevation view of another embodiment of an arc discharge tube and containment member arrangement.  
         [0010]      FIG. 4  is a side elevation view of still another embodiment of an arc discharge tube and containment member arrangement.  
         [0011]      FIG. 5  is a side elevation view of yet another embodiment of an arc discharge tube and containment member arrangement.  
         [0012]      FIG. 6  is a side elevation view of a further embodiment of an arc discharge tube and containment member arrangement.  
         [0013]      FIG. 7  is a side elevation view of still a further embodiment of an arc discharge tube and containment member arrangement.  
         [0014]      FIG. 8  is a side elevation view of yet a further embodiment of an arc discharge tube and containment member arrangement.  
         [0015]      FIG. 9  is a side elevation view of another embodiment of an arc discharge tube and containment member arrangement.  
         [0016]      FIG. 10  is a side elevation view of still another embodiment of an arc discharge tube and containment member arrangement.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]      FIG. 1  illustrates a high-intensity discharged lamp  100  having a base  102  and an outer envelope  104  supported on the base. Base  102  includes a body  106  having a plurality of threads  108  formed thereon. However, it will be appreciated that any suitable arrangement for interengaging the base with a corresponding lamp socket can be used. An electrical contact  110  is provided on base  102  and is electrically insulated from body  106  by insulating material  112 .  
         [0018]     Outer envelope  104  forms an envelope cavity  114  in which an arc discharge tube  116  is supported on support members  118  and  120 . Arc discharge tube  116  includes an elongated body  122  having opposing end walls  124  and  126  and at least partially defining an arc discharge chamber (not shown). Legs  128  and  130  extend from end walls  124  and  126 , respectively, in this double-ended arc tube arrangement. Lead  132  extends from leg  128  and is supported on support member  118 . Lead  134  similarly extends from leg  130  and is supported on support member  120 . A pair of spaced apart electrodes (not shown) extends into the arc discharge chamber (not shown) for forming an arc discharge therein in a manner well known in the art. Each of the electrodes is in electrical communication with a different one of leads  132  and  134 . A containment member or wire  136  extends from support member  118  and is received around elongated body  122  of discharge tube  116 .  
         [0019]     It will be appreciated that base  102 , outer envelope  104 , discharge tube  116  and support members  118  and  120  of lamp  100  are all of typical construction and respectively formed from materials well known to those of skill in the art. As such, further details of these materials and other structural features are not provided herein.  
         [0020]      FIGS. 2-10  illustrate various embodiments of containment member and arc discharge tube arrangements. Each of these figures includes an arc discharge tube  116  having opposing end walls  124  and  126  with legs  128  and  130  respectively extending therefrom. Support member  118  is also shown in  FIGS. 2-10  and supports arc discharge tube  116  as shown in and described with regard to  FIG. 1  in conjunction with support member  120  ( FIG. 1 ).  
         [0021]     As shown in  FIG. 2 , containment member  136  extends from support member  118  and is wrapped helically around elongated body  122  of discharge tube  116 . The helical configuration is used to minimize the shadows created by the containment member. The containment member includes two linearly extending end portions  138  and  140  respectively supported on support member  118  in spaced relation to one another at attachment points  142  and  144 . It will be appreciated that securing the containment member to the support member can improve the robustness of the lamp by helping to support the arc discharge tube.  
         [0022]     The embodiment shown in  FIG. 3  is similar to that shown in and described with regard to  FIG. 2 . As shown in  FIG. 3 , containment member  136  helically extends around elongated body  122  of arc discharge tube  116  in a manner similar to that shown in and described with regard to  FIG. 2 . However, the containment member in  FIG. 3  has end portions  146  and  148  that extend in a curvilinear manner and form at least a portion of a loop between support member  118  and elongated body  122 . End portions  146  and  148  are respectively supported on support member  118  in spaced relation to one another at attachment points  150  and  152 . The curvilinear end portions  146 ,  148  provide some limited capacity for expansion, thus absorbing kinetic energy if a non-passive failure or rupture occurs.  
         [0023]      FIG. 4  illustrates an arc tube and containment member arrangement similar to that shown in and described with regard to  FIG. 3  in which containment member  136  extends helically along elongated body  122  of arc discharge tube  116 . However, the containment member in  FIG. 4  has end portions extending along curvilinear paths each substantially forming loops  154  and  156  between support member  118  and elongated body  122 . It will be appreciated from  FIG. 4  that the end portions of containment member  136  are supported on support member  118  in spaced relation at attachment points  158  and  160 .  
         [0024]     Another embodiment of an arc discharge tube and containment member arrangement in accordance with the present invention is shown in  FIG. 5 , containment member  136  extends around elongated body  122  of arc discharge tube  166  forming a single loop therearound. The containment member has linearly extending end portions  162  and  164  extending between support member  118  and elongated body  122  and is supported on the support member at attachment point  166 .  
         [0025]     The arc tube and containment member arrangement shown in  FIG. 6  is substantially similar to that shown in and described with regard to  FIG. 5 . However, the arrangement in  FIG. 6  includes a second containment member  168  extending around elongated body  122  in spaced relation to containment member  136 . Containment member  136  has linearly extending end portions  162  and  164  extending between support member  118  and elongated body  122 . End portions  162  and  164  are supported on support member  118  at attachment point  166 . Similarly, containment member  168  has two linearly extending end portions  170  and  172  extending between support member  118  and elongated body  122 . End portions  170  and  172  are supported on support member  118  at attachment point  174 .  
         [0026]     Turning now to  FIG. 7 , the arrangement includes an arc discharge tube  116  and containment members  136  and  168  similar to those described with regard to  FIG. 6 . However, the arrangement in  FIG. 7  differs from that in  FIG. 6  in that containment member  136  includes curvilinear end portions  176  and  178  and containment member  168  includes curvilinear end portions  180  and  182  rather than the linearly extending portions shown in  FIG. 6 . End portions  176  and  178  of containment member  136  each form at least a portion of a loop and are each supported on support member  118  at attachment point  184 . Similarly, end portions  180  and  182  of containment member  168  each also form at least a portion of a loop and are supported on support member  118  at attachment point  186 .  
         [0027]      FIG. 8  illustrates yet another embodiment of an arc discharge tube and containment member arrangement. Containment member  136  includes a plurality of coils  188  and extends around at least a portion of elongated body  122  of arc discharge tube  116 . Containment member  136  includes end portions  192  and  194  that extend in a curvilinear manner and are supported on support member  118  at attachment point  190 .  FIG. 9  illustrates an arc discharge tube  116  having a containment member  136  that extends helically around elongated body  122 . Containment member  136  includes a plurality of coils  188  extending therealong between curvilinear end portions  192  and  194 . End portions  192  and  194  in  FIG. 9  are respectively supported on support member  118  at attachment points  196  and  198 . The plurality of coils shown in  FIGS. 8 and 9  extend substantially along the entire length of containment member  136  including curvilinear end portions  192  and  194 . However, it will be appreciated that any suitable number of coils can be used and that substantially linear portions can be used and/or form a part of containment member  136 .  
         [0028]     Another embodiment of an arc discharge tube and containment member arrangement is shown in  FIG. 10 . The arrangement includes an arc discharge tube  116  and containment members  136  and  168  extending helically along elongated body  122  thereof. Containment member  136  includes substantially linearly extending end portions  200  and  202  extending from and supported on support member  118 . Similarly, containment member  168  includes substantially linearly extending end portions  204  and  206  extending from and supported on support member  118 . As is apparent from  FIG. 10 , containment members  136  and  168  extend along elongated body  122  in a substantially double helix-type arrangement. The end portions of each containment member are supported on support member  118  in spaced relation to one another. As such, end portions  200  and  204  are supported on support member  118  at attachment point  208 , and end portions  202  and  206  are supported on support member  118  at attachment point  210 .  
         [0029]     As shown in  FIGS. 2-10 , the end portions of the containment members are supported on or secured to support wire  118  at the associated attachment points. The end portions are secured to the support member at the respective attachment points in any suitable manner and by using any suitable process or materials. In one embodiment, the end portions are welded to the support member. Additionally, it will be appreciated that while the end portions are shown and described herein as being attached to the support member in various positions relative to one another, any suitable positions, configurations or other arrangements can be used. For example, end portions  138  and  140  shown in  FIG. 2  are respectively attached to support member  118  at attachment points  142  and  144 . However, the attachment points could be positioned closer to one another or at a single point positioned substantially centrally along the support member relative to elongated body  122 .  
         [0030]     Furthermore, it will be appreciated that the containment members can be made from any suitable material and can be straight, curvilinear or coiled or any combination thereof. In one embodiment, the containment member is formed from cylindrical wire; however, it will be appreciated that any suitable shape or configuration of material can be used. Additionally, where the containment member is coiled, the pitch of the coils can be varied and optimized to provide the best containment, the least light loss, and the least expensive implementation. Additionally, where the containment member is wrapped in a helical arrangement along the body of the arc discharge tube, the number of wraps, the pitch of the wraps, the pattern of the wraps, such as helix, double helix, cross-double helix and/or simple loops, for example, can also be varied and optimized. In the preferred embodiment illustrated and described above, the containment member does not extend beyond end walls  124  and  126  or along legs  128  and  130  for ease of manufacture and assembly. Additionally, the present invention is not intended to be limited to arrangements in which the containment member extends 360 degrees or more around the elongated body of the arc discharge tube. Rather, any suitable arrangement can be used. For example, in one preferred embodiment shown in  FIG. 8 , the containment member extends at least about 180 degrees around the body of the arc discharge tube.  
         [0031]     The embodiment shown in  FIG. 1  has the advantage of minimizing the shadows created by the containment member in many lamp arrangements. However, containment can be improved if the containment member has some limited capacity for expansion, thus absorbing the energy of the rupture. As such, various configurations, including, but not limited to, those shown in  FIGS. 3, 4  and  7 - 9 , can optionally include at least a portion of one or more loops or coils or alternative configuration that functions to provide excess material for expansion. In other arrangements, such as those shown in  FIGS. 5, 6  and  7 , one or more extra welds can optionally be provided near the arc tube, such as welds  177  and  181  shown in  FIG. 7 , for example, to hold the looped portion of the containment member tightly closed.  
         [0032]     While considerable emphasis has been placed on the preferred embodiments of the invention illustrated and described here, it will be appreciated that other embodiments can be made and that many modifications can be made in the embodiments shown and described without departing from the principles of the present invention. Obviously, such modifications and alterations will occur to others upon reading and understanding the preceding detailed description, and it is intended that the subject invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.