Abstract:
The invention is a retainer assembly that, upon being attached to a panel and placed in a slot in a housing, provides a smooth and continuous surface that allows the panel to slide freely in and out of the housing. The panel can be firmly retained within the housing slot by expanding the width of the retainer assembly. The retainer assembly provides a more uniform heat transfer surface when abutted against the housing slot. The retainer assembly is self-contained to prevent the individual components from becoming dispersed if the assembly is damaged or disassembled. Additionally, retainer assembly provides a mechanism to prevent it from accidentally disassembling.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to retainer assemblies, and more specifically to circuit board retainer assemblies. 
     BACKGROUND OF THE INVENTION 
     Retainer assemblies have been developed for a broad range of applications, such as for reversibly clamping panels and circuit boards attached to the panels within a housing. 
     With some applications, it is important that the circuit board retainer insulate and dampen the circuit board from shock and vibration. For other applications, an important feature of the circuit board retainer is to effectively transfer heat generated by the circuit board through the panel and to the housing to which the panel is mounted. In these applications, the retainer assembly and the panel are made from heat conductive materials. The heat transfer is effective only between surfaces of the retainer assembly and the housing that are in direct contact, and the amount of heat transfer is directly proportional to the amount of shared surface area. Additionally, the heat transfer is more effective when a greater amount of force is applied between the housing and the retainer assembly. 
     A problem with prior art retainer assemblies is that they have a discontinuous surface that abuts against the housing slot. The surface is discontinuous because these prior art retainer assemblies have a plurality of wedge components that expand within the housing slot upon engaging an actuator screw that causes the wedge components to slide together. The wedge components form a rough and discontinuous surface that tends to catch against the housing slot as the panel slides into and out of the slot. This makes installation and servicing of the panels within the housing difficult because the panels do not smoothly slide in and out of the housing slots. 
     Another problem with prior art retainer assemblies is that they distribute heat unevenly because the wedge components form a discontinuous surface having only partial segments in direct contact with the housing assembly. This can cause the panel to have a discontinuous heat distribution pattern which can adversely effect electronic circuitry attached to the panel. 
     Still another drawback with prior art retainer assemblies is that they are not self contained when attached to a panel. Prior art retainer assemblies have a plurality of individual components that are interconnected but which are not encased by a housing or analogous structure. Accordingly, if a prior art retainer assembly is damaged and its individual components become disengaged, the components will be free to move about within the housing. Additionally, prior art retainer assemblies can become disengaged if the actuator screw is unscrewed too much. Again, the components will be free to move about within the housing. In either of the above scenarios, the disengaged retainer assembly components may disrupt the operation of the circuit boards within the housing. 
     There is therefore a need for a retainer assembly that, when attached to a panel and placed in a slot in a housing, provides a smooth and continuous surface that allows the panel to slide freely in and out of the housing. There is also a need for a retainer assembly that provides a more uniform heat transfer surface when abutted against the housing slot. There is also a need for a retainer assembly that is self-contained such that, if damaged, the components are not free to move out of the assembly. Finally, there is a need for a retainer assembly that has a mechanism to prevent it from accidentally disassembling. 
     SUMMARY 
     The invention satisfies this need. The invention is a retainer assembly adapted to attach to a panel that reversibly mounts within a housing slot. The retainer assembly has an elongated guide rail having a slot abutment wall. The slot abutment wall has a continuous external surface and an opposed internal surface. The retainer assembly includes an expansion assembly having a forward wail and a rearward wall. The forward wall is spaced apart from the rearward wall of the expansion assembly by a width. The forward wall of the expansion assembly is disposed proximate to the internal surface of the guide rail. The rearward wall of the expansion assembly includes means for attaching the rear wall to a panel that is adapted to having a circuit board attached thereto. The retainer assembly further comprises an expansion actuator for alternatively expanding and contracting the width between the forward wall and the rearward wall of the expansion assembly. 
     In a preferred embodiment, two retainer assemblies are attached to a panel with the rearward wall of the expansion assembly disposed in abutment with the panel. The panel is slid into a housing slot with the external surface of the guide rail disposed proximate to the housing slot. The panel can be firmly retained within the housing slot by expanding the width between the forward wall and the rearward wall of the expansion assembly until the external surface of the slot abutment wall of the guide rail is pressed tightly against the housing slot. 
    
    
     DRAWINGS 
     These features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying figures where: 
     FIG. 1 is an isometric view of a retainer assembly having features of the invention; 
     FIG. 2 is a side view of the retainer assembly of FIG. 1 shown attached to a panel; 
     FIG. 3 is a side view of the retainer assembly of FIG. 1 shown attached to a panel disposed within a housing slot, with the expansion assembly of the retainer assembly being in a contracted position; 
     FIG. 4 is a side view of the retainer assembly of FIG. 1 shown attached to a panel disposed within a housing slot, with the expansion assembly of the retainer assembly being in an expanded position; 
     FIG. 5 is a cross-sectional view of the retainer assembly illustrated in FIG. 4; 
     FIG. 6 is a cross-sectional view of the retainer assembly illustrated in FIG. 2, taken along line  6 — 6 ; 
     FIG. 7 is a cross-sectional view of the retainer assembly illustrated in FIG. 3, tan along line  7 — 7 ; and 
     FIG. 8 is a cross-sectional view of the retainer assembly illustrated in FIG. 3, taken along line  8 — 8 . 
    
    
     DETAILED DESCRIPTION 
     The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, Id however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well. 
     The invention is a retainer assembly  10  adapted to attach to a panel  12  that is capable of reversibly mounting within a housing slot  14 . As shown in the embodiment illustrated in the Figures, the retainer assembly  10  comprises an elongate guide rail  16 , an expansion assembly  18 , and an expansion actuator  20 . 
     The guide rail  16  has a slot abutment wall  22  having a continuous external surface  24  and an opposed internal surface  26 . In the embodiment illustrated in the drawings, the guide rail  16  includes two opposing side walls  28  that are attached to the slot abutment wall  22  such that the guide rail  16  is substantially U-shaped in cross-section so as to form an elongate channel. The width of the slot abutment wall  22  is typically between about 0.20 inches and about 1.0 inches and the width of each side wall  28  is between about 0.20 inches and about 1.0 inches. In the embodiment illustrated in the drawings, the width of the slot abutment wall  22  is about 0.25 inches and the width of each side wall  28  is about 0.25 inches. The length of the retainer assembly  10  is typically between about 1.5 inches and about 20 inches. In the embodiment illustrated in the drawings, the length of the retainer assembly  10  is about 14 inches. 
     Upon attachment of the retainer assembly  10  to a panel  12 , the slot abutment wall  22  of the guide rail  16  is disposed spaced apart from the panel  12  and the internal surface  26  of the slot abutment wall  22  faces toward the panel  12 . In the embodiment illustrated in the drawings, the slot abutment wall  22  is disposed away from the panel  12  by at least a distance equivalent to the width of the side walls  28 . The distance between the panel  12  and the slot abutment wall  22  of the expansion assembly  18  when the expansion assembly  18  is attached to the panel  12  varies according to the width of the expansion assembly  18 . 
     In a preferred embodiment, the side walls  28  of the guide rail  16  have two sets of opposed side wall openings  30 . As illustrated in FIG. 1, the side wall openings  30  are generally rectangular and disposed spaced apart from each other. 
     Preferably, the guide rail  16  is formed of a thermally conductive material such as a metal or a metal alloy. 
     The expansion assembly  18  moves between a contracted position and an expanded position. As the expansion assembly  18  moves to the expanded position, it applies force to the internal surface  26  of the slot abutment wall  22 . The expansion assembly  18  has a forward wall  32  and a rearward wall  34  that is spaced apart from the rearward wall  34  by a width. The forward wall  32  of the expansion assembly  18  is disposed proximate to the internal surface  26  of the guide rail  16 . The rearward wall  34  of the expansion assembly  18  includes means for attachment of the expansion assembly  18  to a panel  12 . In the embodiment illustrated in the Figures, the expansion assembly  18  is disposed substantially within a U-shaped guide rail  16 . 
     Preferably, the expansion assembly  18  is formed of a thermally conductive material such as a metal or a metal alloy. In a preferred embodiment, the expansion assembly  18  and the guide rail  16  have a surface coating such as nickel plating that can be applied by conventional techniques such as electroless plating or anodized plating. 
     In a preferred embodiment, the rearward wall  34  of the retainer assembly  10  includes mounting members  36  for attaching the retainer assembly  10  to a panel  12 . As illustrated in FIG. 5, the rearward wall  34  of the expansion assembly  18  has threaded holes  36  that serve as the mounting members  36  and the retainer assembly  10  can be attached to the panel  12  by screws  37  passing through the panel  12  and into the threaded holes  36  in the rearward wall  34  of the expansion assembly  18 . As illustrated in FIG. 5, is when the expansion assembly  18  is attached to a panel  12  and placed in a housing slot  14 , the rearward wall  34  of the expansion assembly  18  is disposed proximate to the panel  12  and the external surface  24  of the slot abutment wall  22  is disposed proximate to the housing slot  14 . 
     In a preferred embodiment, the expansion assembly  18  comprises slidably engaging wedged block components  38 . Each block component has a forward face  40  and a spaced apart rearward face  42 . As illustrated in FIGS. 6-8, the forward face  40  of the block components  38  is disposed proximal to the internal surface  26  of the guide rail  16  and the forward wall  32  of the expansion assembly  18  is formed by the forward face  40  of several block components  38 . As illustrated in FIG. 3, the forward wall  32  and rearward wall  34  of the expansion assembly  18  are discontinuous and portions of the forward wall  32  may be disposed more proximal to internal surface  26  of the slot abutment wall  22 . As illustrated in FIG. 2, the rearward wall  34  of the expansion assembly  18  is formed by the rearward face  42  of several block components  38 . 
     In the embodiment illustrated in the drawings, the block components  38  are substantially rectangular in cross-section and each block component  38  has two opposing end surfaces. Preferably, at least two of the block components  38  have at least one wedged end surface and the wedged end surfaces of the block components  38  are in abutment and disposed end-to-end such that they are in sliding contact with each other. 
     As illustrated in FIG.  1  and FIGS. 6-8, each block component  38  has a block hole  44  extending longitudinally through the block component  38 . As illustrated in FIG.  7  and FIG. 8, several of the block components  38  have block holes  44  that are elongated between the forward face  40  of the block component  38  and the rearward face  42  of the block component  38 . In the embodiment illustrated in the drawings, one block component  38  has a circular block hole  44  and another block component  38  has a threaded circular block hole  44 . As illustrated in FIG. 1, two of the block components  38  have threaded holes  36  on their rearward face  42  that serve as the mounting members  36  for attaching the retainer assembly  10  to a panel  12 . 
     The expansion actuator  20  is in operable connection with the expansion assembly  18  and functions to alternatively expand and contract the width between the forward wall  32  and the rearward wall  34  of the expansion assembly  18 . In the embodiment illustrated in the drawings, engagement of the expansion actuator  20  causes at least two wedged block components  38  to slide together such that the forward faces  40  of two block components  38  and the rearward faces  40  of at least two block components  38  are discontinuous and the width of the expansion assembly  18  is increased. The width of the expansion assembly  18  is the greatest distance between the discontinuous forward wall  32  of the expansion assembly  18  and the discontinuous rearward wall  34  of the expansion assembly  18 , which is also the greatest distance between forward face  40  of a block component  38  and the rearward face  42  of another block component  38 . 
     In the embodiment illustrated in the drawings, the expansion actuator  20  comprises an actuator screw  46 . As illustrated in FIG.  7  and FIG. 8, the actuator screw  46  passes through the block holes  44  in the block components  38 . When the retainer assembly  10  is attached to a panel  12 , the actuator screw  46  is spaced apart from the panel  12  by a fixed distance as a result of the actuator screw  46  passing through block components  38  having substantially circular block holes  44  that are only slightly larger than the actuator screw  46 . As illustrated in FIG.  7  and FIG. 8, block components  38  having elongated block holes  44  are capable of moving relative to the fixed actuator screw  46 . 
     The actuator screw  46  has a first opposed end  48  and a second opposed end  50 . As illustrated in FIG. 5, the first opposed end  48  of the actuator screw  46  includes a screw head member  52  that is incapable of passing through the block hole  44  of the most proximal block component  38 . The screw head member  52  has an alien is wrench opening  54  that allows the actuator screw  46  to be turned by an alien type tool. In alternative embodiments (not shown), the screw head member  52  has an opening which accommodates a screwdriver and the actuator screw  46  can be turned by a screwdriver. 
     As illustrated in FIG. 1, a screw head flange  55  is disposed between the screw head member  52  and the most proximal block component  38  The screw head flange  55  is sized and dimensioned such that it is incapable of passing through the block hole  44  of the most proximal block component  38 . A screw head spring  56  is disposed within the screw head flange  55  and is in abutment with the screw head member  52 . The screw head spring  56  places a constant force against the screw head member  52 . 
     As illustrated in FIGS. 2 and 3, the second opposed end  50  of the actuator screw  46  has a crimped portion  58  that prevents the second opposed end  50  of the actuator screw  46  from passing into the block component  38  that is disposed most proximal to the second opposed end  50  of the actuator screw  46 . The crimped portion  58  prevents the retainer assembly  10  from being disassembled from the second opposed end  50 . 
     Preferably, the retainer assembly  10  further includes at least one retainer clip  60  that is and is sized and dimensioned to fit within the Ushaped guide rail  16 . In the embodiment illustrated in the drawings, the retainer assembly  10  has two retainer clips  60 . As illustrated in FIG. 1, each retainer clip  60  has a generally U-shaped internal surface which defines a clip opening  62  that is sized and dimensioned to accommodate the actuator screw  46 . Each retainer clip  60  has an external clip surface which comprises one planar clip surface  64  that is disposed in parallel and proximal to the internal surface  26  of the slot abutment wall  22 . The external surface of the retainer clip  60  also includes two angled planar surfaces  66  which extend in part through one set of the opposed side wall openings  30 . The retainer clips  60  have a width that is slightly less than the width of the side wall openings, such that the retainer clips  60  are free to move back and forth a short distance within the side wall openings. 
     As illustrated in FIG. 1, the retainer clips  60  function to secure the expansion assembly  18  to guide rail  16 . In this embodiment, the elongate actuator screw  46  extends through the block holes  44  in the block components  38  and through the retainer clip  60  in order to align the block components  38  and secure the block components  38  to the guide rail  16 . 
     The invention also includes a method of reversibly mounting a panel  12  in a housing slot  14  comprising the steps of selecting the retainer assembly  10  described herein, attaching at least one retainer assembly  10  to a panel  12  such that the reward wall of the retainer assembly  10  is proximal to the panel  12  and the slot abutment wall  22  of the guide rail  16  is spaced apart from the panel  12 , adjusting the expansion actuator  20  such that the width between the forward wall  32  and the rearward wall  34  of the expansion assembly  18  is contracted, sliding the panel  12  into a housing slot  14  having two spaced apart and parallel housing slot  14  walls such that a portion of the panel  12  is proximal to one housing slot  14  wall and the external surface  24  of the slot abutment wall  22  is disposed proximal to the opposing housing slot  14  wall, and adjusting the expansion actuator  20  such that the width between the forward wall  32  and the rearward wall  34  of the expansion assembly  18  is expanded until the external surface  24  of the slot abutment wall  22  guide rail  16  is pressed tightly against the housing slot  14  and the panel  12  is firmly retained within the housing slot  14 . 
     In a preferred embodiment, there are two retainer assemblies  10  attached to the panel  12 . In another preferred embodiment, the retainer assembly  10  is mounted to a panel  12  that is adapted to have a circuit board attached thereto. 
     In operation, turning the actuator screw  46  in one direction causes the threaded block component  38  to move towards the screw head member  52  such that the distance between the screw head member  52  and the threaded block component  38  is reduced and at least two block components  38  in sliding contact move toward each other. This causes the distance between at least a portion of the forward wall  32  and at least a portion of the rearward wall  34  to increase so that the forward wall  32  of the expansion assembly  18  places a force upon the slot abutment wall  22  of the guide rail  16 . In response, the slot abutment wall  22  uniformly moves away from the rearward wall  34  of the expansion assembly  18 . 
     Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.