Abstract:
A captive fastener assembly that employs a concentric collar protrusion protruds from the bottom circular edge of the screw hole, surrounds the lower transitional shaft of the fastener to hold the fastener steadily aligned with the receiving hole when the to-be-fastened parts as being opened or closed.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a fastener assembly that self-aligns the fastener to the fastener target hole during the operation when to-be-fastened parts are being opened or closed. 
       BACKGROUND OF THE INVENTION 
       [0002]    Typical captive fasteners, particularly captive screws, comprise a screw head, and a cylindrical, elongated screw body, with most of its lower part threaded with external treads. This type of fastener is typically used to fasten two to-be-fastened objects, one is herein called a holding part, and the other is called a target part. The holding part in existing fastener assemblies typically has a hole (hereinafter as ‘holding hole’) with a diameter that allows the fastener to be fit through. The interior surface of the holding hole may be threaded with interior threads mating the exterior threads on the fastener. Further, on the target part, there is also a hole (hereinafter as “target hole”) with a diameter that allows the fastener to be fit through. The interior surface of the target hole is also typically threaded with interior threads mating to the exterior threads on the fastener. The hole on the target part and the holding part are typically concentrically aligned to receive the fastener. 
         [0003]    Such existing fasteners are typically threaded into the holding part until the bottom threaded portion on the fastener breaks through the far side surface of the holding part, thus holding the fastener by a transitional shaft between the threaded portion and the head of the fastener. The diameter of the transitional shaft of the captive fastener is smaller than the internal diameter of the threaded hole in both object and target parts to which the fastener is assembled. 
         [0004]    This existing type of captive fastener especially poses a problem when retained in a hinged door manner that brings the head of the fastener initially into position at an off angle with respect to the direction for proper mating and thread engagement. As the door is tightened and brought into its fully seated position, the off angle is gradually eliminated; however, it can take considerable manipulation of the screw position to ensure that the threads are properly aligned before the door reaches the fully seated position. Wear-and-tear occurs to both the internal and external threads during this procedure. 
         [0005]    The radial clearance between the fastener shaft and the holding hole allows movement (wiggling) of the fastener within the hole. This wiggling or freedom of movement causes an angular skew between the fastener center axis and the axis of the holding hole. The ability for the fastener to move becomes problematic when a user attempts to engage the fastener to the threaded target hole while trying to align the fastener with the target hole. 
         [0006]    The problem is particularly acute for some screw assemblies when used for instruments or appliances where opening and closing of the screw fastened hinged parts are frequently needed. 
         [0007]    Thus there has been an unmet need for a captive screw assembly that allows the screw to be held steadily and closely aligned with the target hole. 
         [0008]    Existing efforts have been focused on the door hinge mechanism and the accuracy of the location of the holding and target holes. However, effective improvements have not been found to address the herein discussed alignment issue, particularly to remove the screw ‘wiggling’ issue. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention disclosed herein aims to solve the problems related to captive fasteners, particularly to the misalignment between the fastener and the target hole of the fastener caused by the minor freedom of movement of the fastener. 
         [0010]    Accordingly, it is a general object of the present disclosure to provide a captive fastener assembly that holds the fastener to be steadily and closely aligned with the target hole of the fastener for optimal mating thread alignment and engagement. 
         [0011]    It is a further object of the present disclosure to provide a captive fastener assembly that employs a collar-like protrusion on the holding part surrounding the lower transitional shaft of the fastener to provide improved alignment of the fastener by limiting the angular skew of the fastener&#39;s center axis with respect to the center axis of the target hole. 
         [0012]    It is further an object of the present disclosure to provide a captive fastener assembly that allows the fastener to be self-aligned with its target hole, which avoids the damages to the threads of both the fastener and the target hole. 
         [0013]    It is further an object of the present disclosure to provide a captive fastener assembly that allows the fastener to be self-aligned with its target hole, therefore enhancing the efficiency of the fastening procedure. 
         [0014]    One major novel aspect of present invention comprises a circular, collar-like protrusion extending outward from opposite side of the head of the fastener on the holding part containing a captive fastener. The circular protrusion contains an inner circular bore with a diameter larger than the threads of the captive fastener. The circular protrusion along with the inner bore forms a collar around the threads of the captive screw. This collar element is used in conjunction with the threaded holding hole to hold the fastener to be aligned with the target hole of the target part to be fastened. As the fastener transitions axially, the external threads of the fastener become confined by the inner wall of the collar thus limiting the amount of freedom the fastener can move radially. The restriction of movement by this inner bore keeps the fastener better aligned during the assembly process. The length, inside wall diameter, and outside wall diameter of the collar can vary depending on specific applications. 
         [0015]    This collar-like protrusion does not interfere with the functionality of the captive fastener. The fastener maintains its rotational freedom and the ability to move along the axial direction as intended, allowing normal screw engagement and disengagement to and from the threaded target hole, respectively. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a cross-sectional view of the captive fastener assembly according to the present invention in a fully assembled (closed) condition. 
           [0017]      FIG. 2  is another cross-sectional view of captive fastener assembly according to the present invention in a disassembled (open) condition. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring to  FIG. 1 , the presently disclosed fastener assembly is comprised of a holding part  6  with a holding hole  22 , a target part  4  with a target hole  10 , a captive fastener  8 , and a protruded collar  12 . 
         [0019]    Further, fastener  8  comprises a fastener head  28 , a transitional shaft  24  and external threads  20   a.    
         [0020]    Target part  4  further comprises target hole  10  and interior threads  20   b.    
         [0021]    Fastener  8 , holding hole  22  and target hole  10  are intended to be aligned along a common axis  18  when being under a closed condition. 
         [0022]    As shown in  FIG. 1 , a fastener head  28  and a typical self-tapped or threaded holding hole  22  are conventionally used to hold a captive fastener  8  to a holding part  6 . As a novel aspect of the present invention, the concentric protruded collar  12  and an inner circular bore  14  extend outward from the holding part  6  toward the target part  4 . The diameter of circular bore  14  is preferably slightly greater in size than the outside diameter of the threads  20   a.  Providing this radial clearance ensures the intended function of the fastener  8  is not compromised. Normal axial movement of the fastener  8  along axis  18  and rotational movement of fastener  8  are not affected. 
         [0023]    Angular deviation of the fastener  8  from the central axis  18  is minimized because of the limiting space allowed between fastener threads  20   a  and inner bore  14 . Fastener  8  aligns itself, being held collectively by bore  14 , head  28  and holding hole  22 . This design results in an improved alignment of fastener  8  to target hole  10  in the target part  4  and ultimately a less cumbersome assembly procedure. 
         [0024]    Collar  12  and bore  14  may be modified in both diameter and length based on the intended application. Preferably, the length of collar  12  should extend slightly over the threaded portion  20   a  of the fastener  8  when the fastener  8  is in a fully engaged position as shown in  FIG. 1 . This prevents the threads of the fastener near its transitional shaft  24  from catching on the end face of collar  12  when the fastener  8  is being disengaged. The depth of bore  14  is preferably long enough to allow full disengagement between threads of fastener  20   a  and target hole  10  before the holding part  6  and target part  4  begin to separate from each other. 
         [0025]    A recess  16  is employed on target part  4  with a corresponding shape and location designed to accept collar  12 . 
         [0026]    Internal threads  20   b  within the target hole  10  can either be machined into target part  4  or a threaded insert  26  can be employed as shown in  FIGS. 1 and 2 . 
         [0027]      FIG. 2  illustrates the assembly in the ‘open’ position prior to assembly. The fastener  8  is threaded into holding part  6  until it becomes captive. Target part  4  includes a hole  10  with internal threads  20   b  possibly by the means of a separate part (i.e. threaded insert  26 ) to accept the fastener  8 . Proper design and installation of the assembly insures threaded hole  10  &amp;  20   b  of the target part  4 , the captive fastener  8 , and the holding part  6  are all concentric to one another along the common axis  18 . Collar  12  and bore  14  of holding part  6  maintain the concentricity between fastener  8  and holding part  6 . 
         [0028]    As can be seen in  FIG. 2 , fastener  8  aligns itself to target hole  10 , being held collectively by bore  14 , head  28  and holding hole  22 . The novel fastener assembly design with the extruded collar  12  and bore  14  allows fastener  8  to be concentrically inserted into hole  10 , without damaging threads  20   b.  Threads of fastener  20   a  are free to move along common axis  18  and recede within bore  14  to avoid interference with target part  4  as collar  12  aligns and seats with recess  16 . Once seated, the threads of fastener  20   a  are then free to move in the opposite direction to be fully screwed into internal threads  20   b.  The design also improves the efficiency of assembly procedure since it reduces the time it takes for operator to align fastener  8  and hole  10 , or to locate hole  10 . 
         [0029]    Although the present invention has been described in relation to particular exemplary embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention not be limited by the specific disclosure.