Abstract:
A snap-in fastener secures two sheets together by snap fit. Extensions of the fastener body include a clinch feature that provides a permanent attachment to a first sheet of metal. Integral snap arms which extend beyond the opposite side of the first sheet provide a reusable means to attach to an appropriately sized hole in a second sheet thus uniting the two sheets. The sheets include rectangularly-shaped holes positioned in alignment through which the snap arms of the fastener pass to achieve attachment. A locking mechanism may be employed to hold the snap arms in their engaged position to prevent pull-out of the second panel. In addition, finger grips integral with the body of the fastener provide an ergonomically suitable handle for carrying the attached sheet.

Description:
[0001]    The present application is related to provisional patent application entitled “Rectangular-Hole Snap-In Fastener”, Ser. No. 60/183,974, filed Feb. 22, 2000, priority from which is hereby claimed. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to snap engagement fastening for quickly installed fasteners to secure two panels or sheets. In particular, it relates to panel fasteners which permit the manual securement and release of two panels or sheets.  
         BACKGROUND OF THE INVENTION AND PRIOR ART  
         [0003]    The process of assembling equipment into racks involves attaching the equipment shelf to the side rails of a rack that has a series of vertically spaced rectangular holes in the side rails. Prior art fasteners for this type of rack system utilize a cage nut assembly, washer, and screw combination. This process requires that a cage nut be installed in the rack in the correct vertical position which requires a good deal of manual dexterity, and a special tool. Next, the shelf is placed so that the holes are aligned with the cage nut, and then manually held in place while a screw and washer are put into place and tightened. This operation needs to be repeated on both sides of the rack and two to four fastener assemblies may be required for each shelf Removal of the shelf requires that all screws be removed and such loose screws and washers are then prone to be lost or fall into the sensitive electronic equipment. If retained threaded fasteners are used, each of them will require multiple turns by hand or with a tool for installation and removal. Thus, the present method of assembling rack systems is both time consuming and cumbersome. There is therefore a need to simplify the process of assembling equipment shelves to a rack having vertically spaced square holes.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention significantly simplifies affixing an equipment shelf to the sides of the equipment rack. A novel snap-in fastener for rectangular holes has been developed which is permanently affixed to the shelf Attachment of the shelf is accomplished by merely snapping the fastener into the rectangular holes in the side rails of the rack. Removal is accomplished by simply pulling on the shelf or the fastener itself. There is no loose hardware that can be lost or cause damage to the equipment. While the present invention is an advancement in the art of assembling rack systems, the fastener disclosed herein is not limited to this specific application. It may be used in any application where panels need to be quickly secured without tools. This invention provides a fastener with several important features. First, the fastener has a clinch feature that provides permanent attachment to a first sheet of metal. Secondly, integral snap-arms provide a reusable means to attach the first sheet to an appropriately-sized rectangular hole in a second sheet. In addition, other optional features such as a locking mechanism and finger grips may be included.  
           [0005]    The clinch attachment works by displacing metal from the first sheet into the undercut of the fastener. Once the metal has entered the undercut the part is permanently attached to the first sheet. The clinch profile and the overall envelope of the fastener can be sized for a wide variation of panel sizes and thickness.  
           [0006]    The snap-arms include tapered barbs that allow the ends of the arms to initially engage the rectangular hole on the second sheet. With continued axial application of force, the arms flex inward and pass through the hole, at which point the arms return to their original position and thus retain the fastener in the hole. Pulling on the fastener or the shelf releases it in a similar manner.  
           [0007]    A further embodiment of the fastener includes a locking mechanism. Once the second sheet has been engaged, a lock clip is pushed forward and snaps into place between the snap-arms thus preventing the fastener from loosening or being removed. This is accomplished by the lock clip acting as a positive stop to prevent the snap-arms from flexing inward and disengaging the hole in the second sheet. The fastener is then unlocked by simply pulling the lock clip into the unlocked position. In the unlocked position, the locking mechanism is out of the path of the flexing arm and allowing separation of the two sheets. The lock clip may include detents to ensure that the lock is held out of the path of the snap-arms while it is unlocked. The lock clip also prevents premature disengagement due to vibration. The lock clip may be molded from plastic, thereby providing a means of color identification and matching.  
           [0008]    Another embodiment includes finger grips integral with the fastener. This allows parts of the fastener to function as a handle for the equipment. The extension of the fastener body is ergonomically designed and eliminates the need for additional hardware such as handles and/or knobs. Also by locating the finger grips directly behind the snap feature, the applied forces are directed axially, reducing lateral stresses on the fastener, thereby reducing the required force of assembly and disassembly. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIGS. 1 and 1A are top right front isometric assembly views of the present invention;  
         [0010]    [0010]FIG. 2 is top right front perspective view of the present invention securing parallel sheets;  
         [0011]    [0011]FIG. 3 is a top right rear isometric view of the present invention;  
         [0012]    [0012]FIGS. 4 and 5 are top views partially sectioned showing the lock clip in different positions;  
         [0013]    [0013]FIG. 6 is a front sectional view taken from FIG. 4 as shown in that Figure;  
         [0014]    [0014]FIG. 7 is a top view of the main body element of the present invention;  
         [0015]    [0015]FIG. 8 is a side view of the lock clip element of the present invention;  
         [0016]    [0016]FIG. 8A is a sectional view taken from FIG. 8.  
         [0017]    FIGS.  9 - 12  show various alternate sheet aperture configurations;  
         [0018]    [0018]FIG. 13 is a top view of an alternate embodiment of the main body portion;  
         [0019]    FIGS.  14 - 16  are top views of alternate extension arm attachment means;  
         [0020]    [0020]FIG. 17 is a rear view of the lock clip element shown in isolation;  
         [0021]    [0021]FIG. 18 is a side view of the lock clip shown in FIG. 17;  
         [0022]    [0022]FIG. 19 is a rear view of an alternate embodiment of the lock clip of the present invention shown in isolation;  
         [0023]    [0023]FIG. 20 is a side view of the lock clip shown in FIG. 19;  
         [0024]    [0024]FIG. 21 is a top right rear isometric view of an alternate embodiment lock clip shown in isolation; and  
         [0025]    [0025]FIG. 22 is a side view of the alternate lock clip shown in FIG. 21. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    [0026]FIGS. 1, 1A,  2 , and  3  depict the basic features of the fastener of the present invention in perspective view. FIG. 1 shows the fastener  1  with its longitudinally extending side extensions  1   a  and snap-arms  1   b  aligned with properly sized mounting hole  4  in first sheet  2  prior to installation. In FIG. 1A, the fastener is permanently clinched to first sheet  2  and in position, aligned with hole  5 , for attachment to second sheet  3 . FIG. 2 shows the three elements in FIGS. 1 and 1A joined. The second sheet  3  is releasably attached by the fastener to the first sheet by means of resilient snap-arms  10  of the fastener which lie between the side extensions on either side of the longitudinal axis of the fastener. The snap-arms have barbed ends which grip the side edges of hole  5  in the second sheet  3 . Lock clip  6  is shown in its locked position with legs which extend between the snap-arms to positively wedge them apart. FIG. 3 is a perspective view from the attachment end of the fastener and more clearly shows the basic elements of a fastener including side extension  1   a , lock clip  6 , snap-arms  10  and the clinch feature  1   b . Lock clip  6  is shown in the locked position.  
         [0027]    [0027]FIGS. 4 and 5 are cross-sectional views of the assembled sheets shown in FIG. 2, with FIG. 4 showing the fastener with lock clip  6  in its locked position and FIG. 5 showing the fastener with the lock clip in the unlocked position. Referring first to FIG. 4, the sides of the main body of the fastener are shown in detail clinched into first sheet  2 . Displacer  7  forces the material of sheet  2  into undercut  8  as it is pressed into the sheet. Snap-arms  10  extend through the backside of second sheet  3  which is attached by direct contact with barbs at the ends of the snap-arms. In this Figure, the lock clip is in its locked position whereby the clip legs are moved between the ends of the snap-arms to hold them wedged apart. It will be understood that the dimensions of the fastener and the relationship between the barbs and the clinch features on the main body of the fastener to the thickness of the attached panels are critical to the snap attachment.  
         [0028]    Referring now to FIG. 5, the same elements in FIG. 4 are shown except that lock clip  6  is in its retracted and unlocked position. In this position, the legs of the lock clip are withdrawn from the ends of the snap-arms and therefore the barbs are not blocked from flexing inward as the fastener is pulled out of second sheet  3 . The snap-arms and configuration of the snap attachment barbs are designed to provide the desired amount of insertion and pull-out force.  
         [0029]    Referring now to FIG. 6, a cross-section taken from FIG. 4 as shown in that Figure, depicts greater detail of the snap-arms  10  and the lock clip  6 . From this view, lock clip  6  can clearly be seen boxing-in snap-arms  10  which abut shoulders  6   a  on the inside surface of the lock clip arms and are constrained by the side surfaces of inward facing tabs  19 . Without inward deflection, the barbs at the ends of the snap-arms will not release the second sheet and thus engagement of the clip lock provides positive attachment of the second sheet to the fastener.  
         [0030]    When in their locked position, the side edges of the snap-arms correspond in dimension to the dimension of the apertures in the sheets so that the sheets are retained laterally, axially, and against rotation. Hence, the sheets are positively secured, being held against movement in all directions. The side extensions  1   a  of the main body of the fastener I are spaced from the lock arms by a gap  10   a  to permit the snap-arms  10  to flex.  
         [0031]    Referring now to FIG. 7, the main body of the fastener is shown. Snap-arms  10  are separated by a gap K and are sized to ensure that the deflection required for snapping is within the elastic region of the material. Surface  13  is the resting surface for the second sheet that provides a positive stop for the snap-in motion when the clinched sheet  2  is thinner than the height J of the clinch feature. When the clinched sheet  2  is thicker than the height of the clinch feature, the clinched sheet acts as the positive stop for the snap-in motion, both sheets being held in face-to-face contact. A lead-in taper  16  on the barbs  18  of the arms  10  forces the arms to flex inward as they are pushed against the sides of hole  5  in the second sheet. Once fully within hole  5  of the second sheet, the arms  10  containing the barbs  18  return to their normal unflexed position on the back of the second sheet  3  to retain the first sheet and fastener assembly axially in sheet  2 . The back taper  17  of the barbs allow the fastener to be removed from the hole in a manner similar to the function of taper  16 . Angles  16  and  17  control the amount of force that is required to install and remove the fastener. Typically angle  16  is 60 degrees and angle  17  is 45 degrees so that the installation force is lower than the removal force. In this Figure, the clinch displacer  7  and undercut  8  are again clearly seen. Guide II provides a clearance fit to the first sheet mounting hole and acts as a lead to aid in aligning the fastener with sheet  2  during installation. Surface  12  is a positive stop for the installation clinch process into the first sheet. Finger grip  14  is large enough to be gripped easily and the outwardly curved radius  15  is ergonomically designed.  
         [0032]    The view direction of FIG. 8 is rotated 90 degrees relative to FIG. 7 and shows the side view of the lock clip  6  with legs  28  having inward facing tabs  19  at their ends. As shown in FIG. 6, these tabs fit between the snap-arms  10  of the fastener and are oriented 90 degrees to the snap-arms to hold them positively wedged apart, resisting inward deflection. With the lock clip tabs  19  in the locked position against the snap-arms, the snap-arms box in the inside surfaces of the rectangular hole of the second sheet to secure the two sheets against relative motion The lock clip tabs  19  have a leading taper  20  that allows the lock to snap into place over the body of the fastener when the two pieces are initially assembled. Radii  21  along the bottom corners of each tab  19  are compatible with the relief radii  22  (FIG. 7) on the snap-arms to provide a close fit in the unlocked position. Lock recess  9  of FIG. 7 is sized to closely receive the base of the lock clip so that its outer surface is flush with the finger grips of the fastener when in the locked position as shown in FIGS. 1, 2, and  3 . The lock recess  9  has parallel interior side larger than the space between the snap-arms  10  to give the lock additional stability in both the locked and unlocked positions. Surface  23  seats against the recess  9  of the fastener main body shown in FIG. 7 to provide a positive stop for the lock clip in the locked position. Detent  24  positions and holds the lock clip in the locked and unlocked positions. The outside surface of the snap-arms includes ergonomic series of raised ridges  27  so that the lock can be easily pushed and pulled. The engagement and disengagement requires only enough force to move the detents  24  and  26  past the body  25  shown in FIG. 7.  
         [0033]    [0033]FIG. 8A is a side view of FIG. 8. In FIG. 8A, the portion of the lock clip, L that remains outside of sheet  2  is wider than the dimension, K of the snap-arms shown in FIG. 7, to prevent rotation of the lock clip about  25 . Inward facing tab  19  extends from the end of leg  28  which also includes detent  24  that functions as explained above. The structure of tab  19  can be seen with greater clarity with reference to the embodiment shown in FIG. 21 which depicts the same tab structure but includes catch means.  
         [0034]    FIGS.  9 - 12  show various sheet aperture configurations, FIGS. 9, 10 and  11  show alternate configurations of the apertures in the first sheet  2 . FIG. 12 shows the basic configuration of the rectangular hole of the second releasably attached sheet  3 . FIG. 9 shows the first of the two most simple variations of holes with which the clinch will work. Length “B” of the hole  4  must be carefully dimensioned to work with the clinch feature. The width “C” must be sized closely with the thickness of the fastener to reduce the possibility of misalignment during installation. In the preferred variation with the lock feature, an extension is required in the hole  4  to accommodate the lock. This is shown by dimensions “D” and “E”.  
         [0035]    [0035]FIG. 10 is an alternate mounting hole suitable for clinch attachment and lock clearance. The diameter “F” corresponds with a circle circumscribed about the rectangle defined by dimensions “D” and “E”.  
         [0036]    [0036]FIG. 11 shows a first sheet aperture which provides the greatest amount of sheet material around the opening for added sheet strength. This configuration has three rectangular holes. The central hole provides the relief for the lock arms and room for the snap-arms to flex. The two side holes are sized to provide a proper clinch attachment. Dimension “G” should be sized to accommodate side extensions  1   b  that contains the clinch features  1   b . FIG. 12, shows the rectangle hole  5  of the second sheet  3  that receives the barbs of the snap-arms. The dimension “A” must be sized with respect to the width of the snap-arms and the barbs. Dimension A 1  of the rectangular hole  5 , must simply be greater than the thickness of the snap-arms. Dimension A 1  may be greater than the minimum to allow for lateral misalignment when multiple fasteners are used in the same sheet.  
         [0037]    [0037]FIG. 13 shows an alternate embodiment of the fastener having a curved wall  29  for greater strength. This curve allows the fastener to withstand additional force during the installation of the clinch.  
         [0038]    [0038]FIG. 14 shows greater detail of the clinch feature at the tip of the side extensions  1   b  of the fastener. The individual numbered elements correspond to those described with regard to FIG. 7.  
         [0039]    [0039]FIG. 15 shows an option to the clinch feature that allows the end of the side extensions of the fastener  31  to be folded over, thus permanently attaching it to a sheet. This configuration is optimal for attaching to very a hard sheet and any sheet sized correctly with the appropriate hole.  
         [0040]    [0040]FIG. 16 depicts an optional method of attachment to the first sheet  2  that allows the ends of the fastener side extensions  34  to be snapped into the mounting hole. This method also allows affixation for any sheet hardness, given the correct thickness of the sheet and the correct hole configuration. With this method the fastener may be removed from the first sheet  2  in case of damage. The back angle  36  can be varied to increase or decrease the force required for removal.  
         [0041]    FIGS.  17 - 21  show alternate embodiments of the lock clip. FIGS. 17 and 18 show an optional catch  37  on the lock. The catch ensures that the arms of the lock do not separate and add stability and strength to the lock clip. The catch includes leading taper  20  that allows the lock to be easily assembled to the fastener body. FIGS. 19 and 20 show an optional catch  39  and slot  40  combination that functions similarly to the corresponding features shown in FIGS. 17 and 18. The preferred material for the lock clip is a molded thermoplastic such as acetyl.  
         [0042]    [0042]FIG. 21 shows a configuration of the lock clip that utilizes a “living hinge” molded from plastic. During assembly with the fastener body, the lock clip is folded along the hinges  41 . The jaws  39  snap over the barb  40 . Taper  42  on the outside of the lock is independent of the hinge configuration, and is preferred for all configurations of the lock clip. This taper guides the lock clip along the sides of the rectangular hole  5  in second sheet  3  as it slides forward from the unlocked to the locked position. The hole  43  aids in molding the lock clip as it helps to reduce the sink, or plastic shrinkage, in the thick section of the base.  
         [0043]    [0043]FIG. 22 shows the lock clip configuration shown in FIG. 21 with the living hinge closed. Also shown in this figure are flaired projections  44  which provide a gripping surface that is oriented so that gripping force does not tighten the lock clip on the fastener base during the unlocking process.  
         [0044]    It should be understood that there may be other modifications and changes to the present invention that will be obvious to those of skill in the art. From the foregoing description, however, the present invention should be limited only by the following claims and their legal equivalents.  
       What is claimed is: