Abstract:
A backplate assembly for a vehicle tail lamp is disclosed. The backplate assembly includes a back housing, a front housing secured to the back housing, a one-piece circuit disposed between the front housing and the back housing, a plurality of bulb clips disposed at least partially between the front housing and the back housing, and at least one fastening screw that passes through the front housing and the back housing to fasten the backplate assembly to the vehicle tail lamp.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to vehicle lamp assemblies. Specifically, this invention relates to a backplate assembly for a tail lamp of a motor vehicle.  
         [0002]     Backplate assemblies are designed to accommodate multiple bulbs using a single assembly and are commonly used in connection with tail lamps of vehicles. The backplate assemblies typically include a single connector that connects the bulbs to the wiring harness of a vehicle. The use of a single backplate assembly for multiple bulbs allows the tail lamps or other lamp assemblies to be easily pre-assembled prior to installation into the vehicle. The lamp assemblies can then be installed in the vehicle as a single unit, and connected to the vehicle&#39;s wiring harness using the single connector.  
         [0003]     There are several types of backplate assemblies currently in use for vehicle lamps. One type of backplate assembly is disclosed in U.S. Pat. No. 6,139,334 to Forish et al. The backplate disclosed therein includes front and back panels. The panels include apertures that align with one another when assembled. A number of conductors are disposed between the front and back panels. The conductors engage contact pads within a lamp socket assembly that extends into the apertures. The backplate assembly, including the lamp socket assemblies, may be attached to a lamp assembly, such as a tail lamp, of a motor vehicle.  
         [0004]     One problem associated with existing backplate assemblies is the use of multiple conductors for the multiple socket assemblies. The use of multiple conductors adds cost and creates intermediate connections that need to be controlled during assembly of the backplate and maintained during the life cycle of the lamp assembly.  
         [0005]     Also, since backplate assemblies are generally elongated structures, controlling bulb position concentric within each reflector and maintaining an air tight seal to the tail lamp becomes problematic. In practice, the elongated shape of the backplate has required as many as six attachment points in order to counteract warping and deflection from the force required to compress the gaskets that surround each bulb against the tail lamp reflector housing. Alignment of the bulbs concentric to the reflector, alignment of the multiple fastening points, and controlling gasket compression for an air tight seal becomes a difficult task due to the number of features to control and each of their related tolerances. Further, the use of snap fits requires more complex and higher maintenance tooling for the reflector and has been found to be less reliable in providing a detachable yet secure attachment.  
         [0006]     Finally, the terminal pins that protrude from the backplate and engage the wire harness connector need to be securely held in alignment to prevent interference or bending of the terminal pins when the connector is attached to the backplate. This terminal pin alignment has been typically achieved by inserting the terminal pins through closely fitted holes in the panel of the backplate. However, since the terminal pins are part of a large stamped conductor, simultaneously threading the plurality of terminal pins through the closely fitted holes in the panel becomes difficult. The assembly process is slowed and the possibility of bending of the terminals during assembly is increased.  
         [0007]     Accordingly, a need exists for an improved backplate assembly that solves these and other deficiencies in the prior art. Of course, the present invention may be used in a multitude of situations where similar performance capabilities are required.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a backplate assembly for a tail lamp. The backplate assembly includes a front housing, a back housing secured to the front housing, a circuit disposed between the front housing and the back housing, a plurality of bulb clips disposed partially between the front housing and the back housing and functionally engaging the circuit, and at least one fastening screw. The circuit is a one-piece circuit formed from a single progressive die stamping process that initially starts as a flat shape and is then progressively formed and bent into the final assembly shape. The circuit includes separation points to allow the creation of independent circuits from the one-piece stamping but eliminates the need for additional conductors since it provides a direct electrical connection from the wire harness connector to the bulb. The at least one fastening screw passes through the front housing and the back housing to engage the tail lamp assembly in an orientation parallel to, in-between and generally within the longitudinal plane of the bulb clips to control bulb position within the tail lamp and reduce the number of fastening points to attach the backplate. The front housing and back housing form a ridged “T” shaped structure to minimize deflection and warping when fastened to the tail lamp. The front housing has slotted rectangular holes that when combined with blades on the back housing secure the position of the terminal pins.  
         [0009]     The present invention also contemplates a tail lamp assembly for a vehicle. The tail lamp assembly includes a tail lamp housing, a plurality of reflectors disposed at least partially within a housing that can have a lens or a plurality of lenses, and a backplate assembly including a front housing, a back housing secured to the front housing, a one-piece circuit disposed between the front housing and the back housing, a plurality of bulb clips disposed partially between the front housing and the back housing and functionally engaging the circuit, and at least one fastening screw. The tail lamp assembly further includes at least one screw hole to receive the at least one fastening screw, a plurality of bulbs mounted in the bulb clips, and at least one gasket mounted on the exterior of the back housing of the backplate assembly. The at least one fastening screw passes through the front housing and the back housing of the backplate assembly to engage the at least one screw hole.  
         [0010]     The backplate assembly and tail lamp assembly of the present invention have several advantages over existing assemblies. In particular, the use of a one-piece circuit manufactured from a single stamping reduces the number of intermediate connections that need to be made during the assembly process and also reduces the number of connection points in the circuit that are susceptible to failure during the life of the tail lamp.  
         [0011]     As well, the use of at least one fastening screw that passes through both the front housing and the back housing in an orientation parallel to, in-between and generally within the longitudinal plane of the bulb clips reduces the number of attachment points required to hold the backplate assembly in place and provides a better seal between the backplate assembly and the tail lamp assembly. The at least one fastening screw can help to locate the position of the bulbs concentric to the reflector by serving as the primary “six way” position locator between the backplate and tail lamp housing. The placement of the at least one screw in-between the bulb clips reduces the cantilevered forces from the gasket compression on either side and combined with the rigid “T” shaped cross-section of the backplate minimizes warpage and deflection. Only one screw is needed for a two bulb backplate and only one additional screw is needed for either a three or four bulb backplate. If a second screw is used, it is preferably positioned parallel and generally within the longitudinal plane of the bulb clips and serves as a secondary “four way” locator.  
         [0012]     Finally, the large slotted rectangular holes in the front housing with lead-in chamfers provide quick and easy insertion of the plurality of terminal pins on the stamped circuit. The blades on the back housing are dimensioned to snugly fit between each pair of terminal pins so that, when assembled to the front housing, the stamped circuit terminal pins are spread apart by the blades and securely held in position.  
         [0013]     While one possible application of the present invention is in connection with a vehicle tail lamp, many other applications are possible and references to use in connection with a vehicle lamp should not be deemed to limit the uses of the present invention. The terms used herein should not be interpreted as being limited to specific forms, shapes, or compositions. Rather, the parts may have a wide variety of shapes and forms and may be composed of a wide variety of materials. These and other objects and advantages of the present invention will become apparent from the detailed description, claims, and accompanying drawings. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective view of a tail lamp assembly incorporating one embodiment of a backplate assembly of the present invention;  
         [0015]      FIG. 2  is a perspective view of the backplate assembly of  FIG. 1 ;  
         [0016]      FIG. 3  is a partially exploded perspective view of the backplate assembly of  FIG. 2 , showing the front housing removed from the backplate assembly;  
         [0017]      FIG. 4A  is a rear perspective view of the front housing for the backplate assembly;  
         [0018]      FIG. 4B  is a detail view of a portion of the front housing of  FIG. 4 , shown with the circuit  16  installed thereto;  
         [0019]      FIG. 4C  is a detail view of a portion of the front housing of  FIG. 4 ;  
         [0020]      FIG. 4D  is a detail view of another portion of the front housing of  FIG. 4 ;  
         [0021]      FIG. 5A  is an exploded perspective view of the backplate assembly of  FIG. 2 ;  
         [0022]      FIG. 5B  is a detail view of a bulb clip shown in  FIG. 5 ;  
         [0023]      FIG. 5C  is a detail view of the blades on the back housing shown in  FIG. 5 ;  
         [0024]      FIG. 6  is a perspective view of one embodiment of a circuit used in connection with the backplate assembly of the present invention, showing the circuit as-stamped from a single sheet of conductive material;  
         [0025]      FIG. 7  is a perspective view of the circuit of  FIG. 6 , showing the circuit bent into a shape appropriate for insertion into the backplate assembly;  
         [0026]      FIG. 8  is a cross-sectional view of the backplate assembly of  FIG. 2  taken along plane  8 - 8  in  FIG. 2 ;  
         [0027]      FIG. 9  is a cross-sectional view of the backplate assembly of  FIG. 1  taken along plane  9 - 9  in  FIG. 1 ;  
         [0028]      FIG. 10  is a cross-sectional view of the backplate assembly of  FIG. 1  taken along plane  10 - 10  in  FIG. 1 ;  
         [0029]      FIG. 11  is a cross-sectional view of the backplate assembly of  FIG. 1  taken along plane  11 - 11  in  FIG. 1 ;  
         [0030]      FIG. 12  is a cross-sectional view of the backplate assembly of  FIG. 2  taken along plane  12 - 12  in  FIG. 2 ;  
         [0031]      FIG. 13  is a cross-sectional view of the backplate assembly of  FIG. 2  taken along plane  13 - 13  in  FIG. 2 ;  
         [0032]      FIG. 14  is a perspective view of another embodiment of a backplate assembly according to the present invention;  
         [0033]      FIG. 15  is a partially exploded perspective view of the backplate assembly of  FIG. 14 , showing the front housing removed from the backplate assembly; and  
         [0034]      FIG. 16  is an exploded perspective view of the backplate assembly of  FIG. 14 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]     Referring now to the drawings, the backplate assembly  10  of the present invention includes a front housing  12 , a back housing  14 , a circuit  16 , a plurality of bulb clips  18 , and a plurality of gaskets  20 .  FIG. 1  shows one embodiment of a backplate assembly  10  installed as part of a tail lamp assembly  22 . The tail lamp assembly  22  includes a housing  23  that may have a lens or a plurality of lenses (not shown), and a plurality of reflectors  24  onto which the backplate assembly  10  attaches. Bulbs  62  (not shown in  FIG. 1 ) are disposed between the housing  23  and reflectors  24  and are mounted in connection with the backplate assembly  10  as shown in  FIG. 2 .  
         [0036]      FIGS. 2-13  show the backplate assembly  10  of  FIG. 1  in more detail. The back housing  14  is a long, flat, substantially oval shape and includes three apertures  26  to accommodate bulb clips  18 , a first mounting locator  32  and a second mounting locator  34 . In alternative embodiments, different numbers of apertures  26  and bulb clips  18  could be used. Apertures  26  each include an annular channel  35  formed around the outside thereof to accommodate gaskets  20 . The first mounting locator  32  is preferably a round shape and the second mounting locator  34  is preferably an oval or oblong shape to facilitate assembly and alignment of the backplate assembly  10  as described in more detail below. The back housing could be of other shapes, and could include any number of apertures and mounting locators in a variety of different shapes and configurations. The back housing is preferably formed from a thermoplastic material using an injection molding process, though other materials and manufacturing processes could also be used.  
         [0037]     The circuit  16  is formed as a single piece in a single progressive die stamping process, and can be of a number of different metal or other conductive materials. It has been found beneficial to use a plated steel material for the stamped circuit  16 . The one-piece circuit  16  starts as a flat shape in the progressive die stamping process such as the flat shape shown in  FIG. 6 . The flat shape may include bridges  37 , terminal pins  42 , bulb contacts  44 , center holes  38 , attachment holes  40 , and separation points  46 . The flat stamping is then progressively formed and bent into a shape appropriate for assembly, for example, the shape shown in  FIG. 7 . In this embodiment, because of the unique opposing design of the circuit  16  wherein pairs of terminal pins  42  and bulb contacts  44  are positioned across from each other, bridges  37  may be easily bent and shaped so as to complete the finished shape of the circuit  16  ready for assembly. In the bent shape, the terminal pins  42  are perpendicular to the flat stamping and the bulb contacts  44  are bent into substantially a “v” shape. The rest of the circuit  16  is bent as necessary to ensure that the terminal pins  42  and bulb contacts  44  will assume the proper orientations when assembled. Center holes  38  are preferably a round shape, and attachment holes are preferably an oblong or “double D” shape to facilitate assembly and alignment of the circuit  16  in the back housing  14  as described in more detail below and to allow for any thermal expansion difference between the metal circuit  16  and plastic parts. Other shapes and configurations could also be used, particularly if more or less than three bulbs are used in the assembly.  
         [0038]     The front housing  12  is shaped to enclose the circuit  16  and facilitate connection to the wiring harness (not shown) for the vehicle (not shown). The front housing  12  includes bulb pockets  48  to receive the bulb clips  18 , a plug receptacle  50  for the vehicle wiring harness (not shown), a plurality of integrally formed posts  30   a ,  30   b , and openings  52   a ,  52   b  for fastening screws  54 . Referring to FIGS.  4 A-D, the wiring harness plug receptacle  50  includes slotted rectangular holes  77  for keeping the terminal pins  42  separated when the backplate assembly  10  is assembled. As well, opening  52   a  has an oval shape on the interior side of the front housing  12  and opening  52   b  has a round shape. The shape of the openings  52   a ,  52   b  can facilitate assembly and alignment of the backplate assembly  10 , as described in more detail below, however, other shapes can also be used. Posts  30   a ,  30   b  can be of varying sizes and shapes to facilitate assembly and positioning of the circuit  16 . For example, center posts  30   a  can have a square cross-section, and attachment posts  30   b  can have a round cross-section to facilitate assembly and proper alignment of the circuit  16  as described in more detail below. Like the back housing, a number of different materials and manufacturing process could be used to create the front housing, but it has been found beneficial to use a thermoplastic material in an injection molding process.  
         [0039]     As shown in detail in  FIG. 5B , bulb clips  18  include a bulb receptacle  58 , a mounting rod  60 , wings  85  and fin  83 . The mounting rod  60  is formed in the shape of a cruciform and guides and orients the bulb clip  18  as it is inserted into bulb pocket  48  of front housing  12 . The fin  83  is formed to separate bulb contacts  44  and bulb receptacles  58  are formed to receive bulbs  62 . During insertion, the fin  83  separates the bulb contacts  44  to the proper gap distance within the bulb clips  18  to create the correct contact surface for bulbs  62  within bulb receptacles  58 . The bulb clips  18  are preferably molded from a thermoplastic material, but could be formed from a number of different materials using a number of different manufacturing processes. The gaskets  20  can be molded from a cellular foam rubber material, such as that commonly known as EPDM (Ethylene Propylene Diene Monomer), but other materials and manufacturing processes could also be used. Other gasket configurations could also be used, including but not limited to the use of a single gasket on the exterior surface of the back housing  14 .  
         [0040]     To assemble the backplate assembly  10 , the circuit  16  is inserted into the front housing  12 . To do so, the center holes  38  on the circuit  16  are aligned with center posts  30   a  in the front housing  12  and the attachment holes  40  are aligned with attachment posts  30   b . The circuit  16  is then pushed on to the front housing  12  such that center posts  30   a  extend through center holes  38  and attachment posts  30   b  extend through attachment holes  40 . As previously described, the center holes  38  are round in cross-section, and the center posts  30   a  are square in cross-section. The difference in cross-section between the center holes  38  and the center posts  30   a  create interference therebetween and thus the circuit  16  is maintained in the appropriate position when the center posts  30   a  are inserted through the center holes  38 . This interference acts like a retaining clip and completely secures the circuit  16  to the front housing  12  eliminating the need for heat staking the attachment posts over the circuit. Heat staking is a typical operation used in the prior art and eliminating this operation reduces assembly expense. The center holes  38  and center posts  30   a  are thus used to properly align and position the circuit  16  on the front housing  12 . The attachment holes  40 , however, are oblong, oval or “double D” shaped in cross-section while the attachment posts  30   b  are round in cross-section. The oblong shape of the attachment holes  40  versus the round shape of the attachment posts  30   b  allow room for expansion and tolerance variances between the circuit  16  and the front housing  12 . Although the shapes described above with respect to the center posts  30   a , center holes  38 , attachment posts  30   b  and attachment holes  40  have been found beneficial and are therefore preferred, other shapes and sizes could also be used in connection with the backplate assembly  10  of the present invention. For instance, the holes  38 ,  40  and posts  30   a ,  30   b  could all be round or could all be square in cross-section.  
         [0041]     After the circuit  16  is inserted into the front housing  12  as described above, the separation points  46  must be trimmed or separated from the circuit body to create independent circuits for each bulb  62 . The separation points  46  can be trimmed in a number of ways, but it has been found effective to first hold down circuit  16  with a stripper plate and then simultaneously trim the separation points with die punches that pass through the stripper plate.  
         [0042]     Once the separation points  46  are trimmed, the mounting rod  60  of the bulb clips  18  are inserted into bulb pockets  48  of the front housing  12  and press-fit and seated into place. During insertion, the cruciform shaped mounting rod  60  is aligned and guided by the bulb pockets  48  having the same cruciform shape and is dimensioned to have a controlled interference between the two. Also, as the bulb clips  18  are inserted, the bulb contacts  44  are pushed apart to the correct gap distance by fin  83 . After all of the bulb clips are seated into place, the back housing  14  can then be installed. The back housing  14  is formed to accommodate the shape of the circuit  16 , and can thus be aligned with the circuit  16  and fastened in place. As the back housing  14  is being installed, the wings  85  on the bulb clips  18  are compressed, clamping it against the circuit  16  and front housing  12 . Also during installation, blades  75  on the back housing  14  are inserted inside the slotted rectangular holes  77  in the front housing  12  and between pairs of the terminal pins  42  on the circuit  16 . After installation, the blades  75  secure and align the terminal pins  42  inside the slotted rectangular holes  77 , as best shown in  FIG. 13 . Many methods for fastening the front housing  12  in place could be used. Ultrasonic welding the perimeter edge  64  of the front housing  12  to the perimeter edge  65  of the back housing  14  is one such method that works well for this application. Once the back housing  14  is installed, the bulb clips  18  cannot move and the bulb clips  18  help hold the circuit  16  and terminal pins  42  securely in place. The gaskets  20  and screws  54  can then be installed. The gaskets  20  are pressed into the annular channels  35  and stay in place because of an interference fit between the gasket  20  and the annular channel  35 . The screws  54  are installed into their respective openings  52   a  and  52   b  in the front housing  12 . Openings  52   a  and  52   b  also include screw retaining fingers  81  that lightly grip the screw threads during installation and captivate the screws  54  inside their respective openings  52   a  and  52   b . Once the gaskets  20  and screws  54  are installed, the backplate assembly  10  is complete.  
         [0043]     The assembled backplate assembly  10  can be installed as part of a tail lamp assembly  22  as shown best in  FIG. 1 . First, the bulbs  62  are inserted into the bulb receptacles  58 , where they contact the bulb contacts  44 . Next, the backplate assembly  10  including the bulbs  62  is aligned with the tail lamp assembly  22  such that bulbs  62  are disposed between the reflectors  24  and the housing  23  of the tail lamp assembly  22 . The tail lamp assembly  22  includes two screw bosses  66  shown best in  FIG. 10  that align with the mounting locators  32 ,  34  of the back housing  14 . The captivated screws  54  are then driven into screw bosses  66  in the tail lamp assembly  22 . The shape of the mounting locators  32 ,  34  help facilitate the installation and alignment of the backplate assembly  10  to the tail lamp assembly  22 . The round shape of mounting locator  32  in combination with a screw boss  66  serves as the primary “6-way” locator to allow the backplate assembly  10  to be properly aligned with respect to the tail lamp assembly  22 . The primary locator fixes the position of the back plate in both directions of all three principle axes (X, Y and Z) and is hence called a “6-way” locator. The oval or oblong shape of mounting locator  34  in combination with a screw boss  66  allows for just longitudinal tolerance variances between the screw boss  66  and mounting locator  34  and is hence called a “4-way” locator. Other shapes could also be used, however. The heights of both screw bosses  66  are in the same plane and determine the compression of gaskets  20  for a controlled air tight seal. Once installed, the longitudinal axis of the fastening screw  54  passes through the front housing  12  and the back housing  14  in an orientation parallel to and generally within the longitudinal plane of the bulb clips  18 . This configuration provides a more controlled seal and better bulb alignment between the backplate assembly  10  and the tail lamp assembly  22 , and requires less assembly steps than other methods of installing backplate assemblies.  
         [0044]     Another embodiment of the backplate assembly  10  of the present invention is shown in  FIGS. 14-16 . The embodiment shown in  FIGS. 14-16  includes only a first fastening screw  54   a  that passes through both the front housing  12  and back housing  14 . A second fastening screw  54   b  passes through the front housing  12  but not the back housing  14 . To accommodate the second fastening screw  54   b , the front housing  12  also includes an extension  68  through which the second fastening screw  54   b  passes. Like the first fastening screw  54   a , the second fastening screw  54   b  aligns with and threads into a screw boss in the tail lamp assembly, but does not pass through the back housing  14 . The remaining features of the embodiment shown in  FIGS. 14-16  are analogous to those described above for the embodiment shown in  FIGS. 1-13 .  
         [0045]     Although the invention has been herein shown and described in what is perceived to be the most practical and preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. Rather, it is recognized that modifications may be made by one of skill in the art of the invention without departing from the spirit or intent of the invention and, therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims.