Abstract:
A tree-type fastener includes one or more fin stabilizer bases disposed on a shaft of the fastener. When the fastener is subjected to a pull-out force, the fins may be prevented from stacking up, buckling or bending by the fin stabilizer base. The stabilizer base is configured to provide no interference with a work piece when inserted in a work piece aperture. The fastener of the invention provides a high removal force to insertion force ratio and a strong, single piece device. The fastener may also be adapted for modification of new and existing tree-type fasteners.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This Non-Provisional Application claims benefit to U.S. Provisional Application Ser. No. 60/750,105 filed Dec. 14, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to fasteners, and more particularly, to tree-type fasteners.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is known that tree-type fasteners are used to join component panels, one or more work pieces, or other structures. The tree-type fastener is typically made of a plastic material and includes multiple standard retention fins located along a longitudinal shaft, the fins extending outwardly from the shaft. The fins may have a shape such as annular, flat, angled, spiral or round, to name a few. These fasteners are designed to be driven axially into an aperture to connect one or more work pieces, and the fins may engage the edges of the aperture and the work piece surfaces to join together the work pieces. Known tree-type fasteners may be found, for example, in U.S. Pat. Nos. 5,468,108, 5,907,891, and 6,669,426.  
         [0004]     When tree-type fasteners are subjected to excessive pull-out forces the fins have a tendency to bend or flex. In these situations, the fins typically stack-up on top of each other as the fastener is pulled through the hole. The fastener end may act to increase the force necessary to pull the fastener through the hole. However, even if the fastener is prevented from being pulled out of the hole, the tree-type fastener with bent or flexed fins may now wobble in the hole due to the stack-up of the fins along the shaft. If the fastener is for an automotive component, such as a routing clip, a fastener that may wobble in the hole could lead to undesirable performance of that component. For known tree-type fasteners made of conventional plastic resins, the removal force of the fastener typically ranges from 30-60 lbs. Some current designs of tree-type fasteners utilize highly angled fins to achieve relatively greater insertion to removal ratios. Even these designs, however, typically do not reach above 50-60 lbs. of removal force.  
       SUMMARY OF THE INVENTION  
       [0005]     Aspects of the invention provide one or more robust fin stabilizer bases disposed on the shaft of the tree-type fastener. As a result, if the fastener is subjected to a pull-out force, the fin stabilizer base will prevent the fins from stacking up, buckling or caving in. The fin stabilizer base is configured to provide no interference with a panel when inserted in a mating panel aperture, and is preferably located along the shaft at a distance from the fastener head that is greater than the width of the panel and any additional components through which the fastener is to be installed.  
         [0006]     Features of embodiments of the invention include a low required insertion force combined with a high removal force and a robust, yet clean design. Because the fastener is fabricated as a single piece, the fastener may be manufactured with a relatively low tooling investment. Features of the invention may also be adapted with new or existing tree-type fastener designs such as 2-barb, 4-barb, and split tree, among other designs.  
         [0007]     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a side view of an embodiment of the invention.  
         [0009]      FIG. 2  is a side view of the embodiment of  FIG. 1 .  
         [0010]      FIG. 3  is a cross-section view of another embodiment of the invention.  
         [0011]      FIG. 4  is a cross-section view of a further embodiment of the invention.  
         [0012]      FIG. 5  is a cross-section view of a still further embodiment of the invention. 
     
    
       [0013]     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof.  
       DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0014]     The Figures illustrate exemplary embodiments of tree-type fasteners of the invention. These embodiments may include a fin stabilization base, also referred to as a fin stabilizer or force multiplier base, located at one or more desired positions along the fastener shaft. In one embodiment, the fin stabilizer is located at a distance below the known work piece thickness of the application, as well as below any additional components attached to the work piece by the fastener. At this location, the fin stabilizer acts as a stop or support structure for the fins by supporting the underside of the fins to prevent the fins from rolling over or stacking-up one on top of another. By placing a fin stabilizer strategically along the shaft, the extraction force required to remove the fastener will significantly increase and wobbling due to damaged fins may also be prevented. It should be understood that additional fin stabilizers may be utilized to further increase the extraction force required to extract the fastener. These fin stabilizers may be positioned at any location along the shaft and between each component that is fastened together.  
         [0015]     Referring to  FIGS. 1 and 2 , an exemplary embodiment of a tree-type fastener  10  is illustrated. Fastener  10  may include a head  11  disposed at the top of a shaft  12  and an end piece  13  disposed at the bottom of the shaft  12 . The head  11  may define any suitable configuration or shape. The end piece  13  also may have any suitable configuration or shape including the depicted substantially conical shape with the wider end attached to the shaft and the narrower end pointed down along the axis as the shaft. Fins  14  may be disposed on the shaft at a predetermined longitudinal spacing from each other and extending outwardly from the shaft in a generally perpendicular manner or at an angle. The embodiment shown in  FIG. 1  illustrates two types of fins  14 , one group disposed on the lower half of the shaft  12  and extending around the full shaft circumference, and the other group comprising two sets of fins  14  disposed on opposite surfaces of the shaft  12  without contacting the shaft surfaces that are located intermediate of the fin sets. It should be understood that the fins  14  may define any suitable shape, may be positioned at any location on the fastener shaft  12 , and may define any extension angle or multiple extension angles with respect to the shaft  12 .  
         [0016]     A fin stabilization base  15  or fin stabilizer may be disposed on the shaft  12  and may extend generally perpendicular to the shaft  12 . The stabilization base  15  may be positioned on the shaft  12  in a longitudinal gap between two fins  14 . The stabilization base  15  may define a truncated conical shape as illustrated in  FIG. 1 , though other shapes and configurations of the base  15  are possible and may be used with the invention. The fin stabilization base  15  is configured to have a diameter that is less than the diameter of the work piece to which the fastener is mounted. With this configuration, there will be no interference between the stabilization base  15  and the aperture edges during installation of the fastener  10 . Consequently, the stabilization base  15  will not significantly increase the insertion force required to insert the fastener  10  through the aperture as compared to a conventional tree-type fastener that does not include a stabilization base  15 . This allows the fastener  10  to be installed with a low ergonomic force, in the range of approximately 5 and 15 lbs. In alternative embodiments of the invention that may use multiple fin stabilization bases  15  disposed on the fastener shaft, each stabilization base may define a diameter that is smaller than the diameter of the aperture to which the fastener is mounted to thereby provide a low required insertion force for the fastener.  
         [0017]     The fin stabilization base  15  generally functions as a fin stop support and further as an extraction force multiplier. As the fins  15  buckle or bend during extraction of the fastener, the fin stabilization base  15  will cause any buckling or bending of the fins to slow or stop. In some embodiments, with the use of the fin stabilization base  15 , the extraction or removal force required to remove the fastener from the aperture to which it is mounted may increase significantly to well over 70 lbs in some embodiments and, in other embodiments, to over 100 lbs. By adding at least one fin stabilization base  15 , significantly greater extraction forces will now be required to remove the fastener from the aperture to which the fastener is mounted.  
         [0018]     The fin stabilization base  15  may be embodied in numerous configurations, including as a ring, square, triangle, or any other robust or solid base shape. An object of the invention is to achieve significant removal-to-insertion force ratios. This may be accomplished by varying the location and number of fin stabilization bases on each fastener. This is, of course, dependant on the specific panel and aperture dimensions, and any other unique application requirements. The placement of at least one fin stabilization base  15  at one or more intervals along the shaft allows the fastener  10  to achieve a high retention force at low insertion force levels. In addition, the end piece  13  shown in  FIG. 1  may also act as a force multiplier. If fins  14  are disposed sufficiently near the end of the shaft to receive support from the end piece  13 , upon application of a removal or extraction force, the end piece  13  will function as a stop to prevent buckling or bending of the fins and thereby increase the extraction force required for removal of the fastener.  
         [0019]     Referring to  FIGS. 3-5 , there are illustrated alternative embodiments of a fastener with a fin stabilization base or a force multiplier base of the invention. These embodiments are shown in cross-section views and are similar to the embodiment of  FIG. 1 . The features and functions of the embodiment of  FIG. 1  are expressly incorporated by reference into the alternative embodiments of  FIGS. 3-5 .  
         [0020]     Referring to  FIG. 3 , a fastener  30  may include a head  31  disposed at the top of a shaft  32  and an end piece  33  disposed at the bottom of the shaft  32 . The fastener  30  may include a “2-fin” configuration that further includes a pair of fins  34  positioned on opposing sides of a fin stabilization base  35 . The fin stabilization bases  35  may be configured on the shaft  32  and may include a solid circular ring that extends around the circumference of the shaft  32 .  
         [0021]     Referring to  FIG. 4 , a fastener  40  may be configured as a “split-tree” fastener design where fins  44  are configured on opposing sides of the shaft  42 . The fins  44  may also be disposed longitudinally offset from each other. With this embodiment, two fin stabilization bases  45  may be disposed on opposite sides of shaft  42  and longitudinally offset with respect to each other. The fastener  40  may include a head  41  disposed at the top of a shaft  42  and an end piece  43  disposed at the bottom of the shaft  42 .  
         [0022]     Referring to  FIG. 5 , a fastener  50  may include two sets of barb-shaped fins  54  disposed on opposing sides of shaft  52 . The fastener  50  may also include a solid rectangular fin stabilization base  55  positioned in a longitudinal gap between fins  54  and fin  56 . The fin stabilization base  55  is disposed around the circumference of shaft  52  and extends generally perpendicular to the shaft axis. Similar to the other embodiments, the fastener  50  may include a head  51  disposed at the top of a shaft  52  and an end piece  53  disposed at the bottom of the shaft  52 .  
         [0023]     The designs of embodiments of the present invention may be implemented into all current as well as new fastener applications without significant tooling changes. The fastener does not change or affect current low ergonomic insertion requirements. The design is flexible in many various embodiments with the fin stabilization base comprising, for example, the shape of a ring, a rectangle, a triangle, a cone, a truncated cone, or more than one offset blocks or rings. The location, size and thickness of the fin stabilization base will determine the ultimate retention force. Thus, changing the location and number of bases employed and the base characteristics makes the retention force adjustable to the specific application desired.  
         [0024]     It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It is also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.  
         [0025]     Various features of the invention are set forth in the following claims.