Abstract:
An end pin has a composite shoulder with a fixed lower half and a rotatable upper half. The halves are alignable in a first, installation mode of minimal footprint relative to the hole and slit in the end piece to permit the pin to be easily inserted through the hole in the end piece. The upper half is rotated into a second, locking mode that increases the footprint of the pin over the hole and slit, thereby preventing inadvertent disengagement of the strap from the pin.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 U.S.C. §109(e), of U.S. Provisional Application No. 61/517,346 filed Apr. 18, 2011 for “Rotatable End Pin for Instrument Strap”. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to attachments for securing a strap to an instrument such as a guitar or the like. 
         [0003]    Musicians, particularly guitar players, often use a strap to suspend the instrument from their bodies in order to play while standing. The strap typically has end pieces made from leather or similar semi-rigid materials. Each end piece has a stamped hole and contiguous slot that is designed to slip over an end pin that rigidly projects from the guitar body. Over time, due to both the weight of the instrument and the repeated application and removal of the strap, the stamped hole can become distorted and enlarged. When this occurs, the end piece can slip off of the pin, disengaging the strap from the instrument and causing the instrument to fall to the floor, resulting in damage. 
       SUMMARY 
       [0004]    The unintended slipping of the end piece from the end pin is greatly reduced or eliminated by our novel end pin, which attaches to the instrument strap in such a way that removal is quite difficult if not impossible unless deliberate steps are taken by the player. 
         [0005]    We disclose an end pin that has a composite top or shoulder with a fixed half and a rotatable half such that the halves are alignable in a first, installation mode of minimal footprint relative to the hole and slit while the pin is inserted through the hole in the end piece, whereupon one half is rotated into a second, locking mode that increases or maximizes the footprint relative to the hole and slit. 
         [0006]    In the first mode the strap can be easily attached to the instrument, and then easily locked in the second mode by applying rotation to a portion of the pin. This creates a very wide surface area contact areas between pin and strap end. The enlarged contact area prevents the pin from inadvertently slipping back through the stamped hole and slot in the strap end. 
         [0007]    One embodiment is directed to an end pin unit for attachment to a musical instrument body, comprising a lower pin member forming a lower shoulder; an upper pin member forming an upper shoulder; a screw for attaching one of the pin members in fixed orientation on a musical instrument body; and a rotatable connection between the upper and lower pin members. The shoulder of one pin member can be alternately rotated into a first mode in which the upper and lower shoulders are oriented to permit attachment of the end strap and a second mode in which the upper and lower shoulders are aligned differently, to prevent detachment of the end strap. 
         [0008]    In one preference, the screw has a head and a threaded shank and the lower pin member has a central bore for threadably receiving the screw shank and thereby assuming a fixed orientation relative to the instrument body when the screw is threaded into the body. Thus, the upper shoulder is rotatable relative to the fixed lower shoulder. 
         [0009]    In another preference, the rotatable connection includes detents for alternately holding the shoulders in the first and second modes. 
         [0010]    The method embodiment is directed to a first mode, characterize by passing a slotted opening of the end piece over a composite shoulder of the end pin so that the composite shoulder protrudes above the end piece, followed by a second mode in which one portion of the composite shoulder remains fixed, while another portion of the composite shoulder is rotated. In the second mode the total area of the shoulder portions that face the end piece, is larger than the total area of the shoulder portions that face the end piece in the first mode, thereby trapping the end piece beneath the shoulders. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0011]    The preferred embodiment will be described in more detail with reference to the accompanying drawing, in which: 
           [0012]      FIG. 1  is an oblique view of the pin configured in a first mode, for slipping through the slit into the hole of the guitar strap end piece; 
           [0013]      FIG. 2  is a section view of the configuration of pin and end strap in the first mode shown in  FIG. 1 ; 
           [0014]      FIG. 3  is an oblique view similar to  FIG. 1 , showing the pin in a second mode, configured to prevent removal from the strap; 
           [0015]      FIG. 4  is a section view of the configuration of pin and end strap in the second first mode shown in  FIG. 3 ; 
           [0016]      FIG. 5  is an oblique view of the pin shown in  FIGS. 1-4 , according to the first mode, before engage with the end strap; 
           [0017]      FIG. 6  is an exploded view of the pin shown in  FIG. 5 ; 
           [0018]      FIG. 7  is a longitudinal section view of the pin in the first mode; 
           [0019]      FIG. 8  is a longitudinal section view of the pin in the second mode; and 
           [0020]      FIGS. 9-11  illustrate the rotation of the upper portion of the pin during installation on the strap end piece. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIGS. 1 and 2  show one embodiment in the first mode, whereby the end piece  10  of an instrument strap has a longitudinal slot  12  and a hole or transverse slot  14  through which the pin  16  is attached to the strap. The pin  16  has a screw portion  18  by which the pin is permanently mounted to the guitar body as represented at  20 . In the first mode, upper  22  and lower  24  pin members each form laterally or radially oblong (e.g., elliptical) shoulders that are congruently aligned on the upper surface of the end piece  10  with their major axes along the longitudinal slot  12 . This minimizes the footprint of the pin  16 , for facilitating passage of the slots  12 ,  14  over the pin. 
         [0022]      FIGS. 3 and 4  show a second mode associated with  FIGS. 1 and 2 , whereby the upper pin member  22  has been rotated 90 degrees. This places the upper shoulder into a transverse orientation relative to the shoulder of the lower pin member  24  (i.e., transverse to the longitudinal slot  12 ). This produces an overall crossing (“+” or “X”) configuration of plural pin members  22 ,  24  that maximizes the footprint of the pin facing the upper surface of the end piece  10 . 
         [0023]    As shown in  FIGS. 5-8 , the pin assembly or unit  16  contains a wood screw  18  for attaching the unit  16  to the instrument  20 . Preferably, a non rotatable lower pin half or member  24  has a small diameter through bore that threadably receives the screw shank whereby the lower pin member  24  can be fixed relative to the screw  18  and the instrument body. A radially inner region has four small indentations or detents  26 , each at 90 degrees to the next. The upper pin half or member  22  has a through bore and a radially inner region that has four protrusions  28 , also at 90 degrees, that match the detents  26  in the lower half  24 . Once the unit  16  is assembled, the upper part  22  can rotate about a cylindrical boss  30  at the entrance to the bore in the lower pin half  24 . An annular wave spring washer  32  in the assembled pin  16 , provides tension between the screw head  34  and the rim of a counter bore or recess  36  that accepts the screw head  34  in the upper half  22 . A soft annular washer  38  sits between the lower half  24  and the instrument body  20  to protect the instrument finish. 
         [0024]    The boss or protrusion  30  in the lower half passes through (e.g., radially inwardly of the rim of) the upper half counterbore  36  to a point slightly proud of the bottom or rim of the counterbore. This forms a rotatable joint between the upper  22  and lower  24  pin members. The wave washer  32  is placed around the boss  30 , and rests on the counterbore face and extends above the boss  30  at its uppermost points. The screw  18  is passed through both upper and lower halves  22 ,  24  and screwed to the instrument until the screw head  34  abuts the lower half boss  30 . At this stage the spring  32  is slightly compressed, applying force between screw head  34  and counterbore  36 , holding the upper half protrusions  28  into the lower half detents  26 . There is still enough “play” for the washer  32  to be compressed into a flat shape. 
         [0025]    The installation procedure will be described with reference to  FIGS. 1-4  and  9 - 11 . The user attaches the end piece  10 , passing the compound, elliptically shaped pair of shoulders of the pin  16  through the stamped hole and slots  12 ,  14  in the end piece  10  ( FIGS. 1 ,  2  and  9 ). The upper pin half  22  is then rotated about the center axis by hand, forcing the protrusions  28  out of the detents  26 . The wave washer  32  is now mostly flat, applying the maximum force between screw head  34  and counterbore  36 . ( FIG. 10 ). When the upper pin half  22  reaches 90 degrees of rotation the washer  32  forces the protrusions  28  back into the matching set of detents  26 . The washer  32  then relaxes to its original state, still applying some tension to the upper half counterbore  36  which holds the upper half in place. ( FIGS. 3 ,  4 , and  11 ). The pin is now in a cross shape, and the resulting added surface area creates a condition where the strap end piece cannot inadvertently be removed from the pin. 
         [0026]    Reversing the rotation procedure realigns the upper and lower halves  22 ,  24  to the installation configuration ( FIGS. 1 ,  2 ,  5 , and  9 ) so the strap end piece can be disengaged from the pin  16 . 
         [0027]    In a general way, the procedure can be summarized as first, passing a slotted opening  12 ,  14  of the end piece  10  over a composite shoulder  22 ,  24  of the end pin unit  16  so that the composite shoulder protrudes above the end piece. While one shoulder  24  remains fixed, another portion  22  of the composite shoulder is rotated, whereby after rotation the total footprint area of the transversely oriented composite portions that directly face downwardly toward the end piece (i.e. the radially outer areas of  22  and  24 ), is larger that the total footprint area of the composite portions that directly face downward toward the end piece immediately after the end piece is passed over the composite shoulder (i.e., only the area of member  24 ). 
         [0028]    In the illustrated embodiment, the lower pin member  24  has a centerline, the shoulder on the lower pin member is oblong and symmetrical about that centerline, and likewise the upper pin member  22  has the same centerline (axis of rotation) and the shoulder on the upper pin member is oblong and symmetrical about that common centerline. The shoulders are identical in a somewhat lens shape and when oriented in the first mode the congruent shoulders also form a larger lens shape. In the second mode the shoulders are transverse. 
         [0029]    Both members should have a substantially circular central area where at least four quadrilaterally symmetric detents and protrusions (e.g.,  26  and  28 ) can be engaged and disengaged via relative rotation of the upper and lower shoulders. The cross section views of  FIGS. 7 and 8  illustrate these central areas, but the peripheries of the shoulders can be different so long as when aligned in the installation mode the footprint is small enough to slip over the hole and/or slot  12 ,  14  in the strap end piece  10 . 
         [0030]    In the preferred embodiment of the lower member  24  shown in  FIGS. 6-8 , a lower, foot portion  40  rests directly or indirectly on the instrument body, a cylindrical pedestal portion  42  rises to an oblong, preferably elliptical shoulder portion  44 , which surrounds the upwardly projecting boss  30 . In the preferred embodiment of the upper member  22 , the counterbore  36  defines a recess having a sidewall which rotatably accommodates the head  34  of the screw and an annular rim that rotatably accommodates the boss  30 . 
         [0031]    It should be appreciated, however, that other shapes for the upper and lower pin members  22 ,  24  and associated shoulders are possible within the spirit and scope of the invention. For example, the fixed, lower pin member  24  can have a more conventional, round top defining an annular shoulder, while the rotatable, upper pin member can be oblong as shown at  22 .