Abstract:
A preload locking wire insert comprised of a unitary, coiled wire having a particular polygonal cross-section for use in combination with a threaded fastener and a complementary threaded bore in a work piece, wherein the wire insert provides a ramping surface which locks the threads of the fastener into place against the inner threaded wall of the bore in the work piece. A further embodiment provides for the wire insert to be threaded into the bore in either direction, with no regard to orientation, while still retaining the definitive locking aspect.

Description:
FIELD 
       [0001]    The present disclosure relates to fastener inserts and, more particularly, to preload locking inserts formed from hardened material such as stainless steel or other metal alloy, which are utilized in tapped holes. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Fastener assemblies come in a variety of shapes, sizes, designs, and materials. Many fastening assemblies include not only a fastener such as a bolt, pin, or screw, but also include a fastener insert to be positioned within a tapped hole. One specific type of fastener insert useful in association with a threaded fastener is the helically coiled wire insert, as described in U.S. Pat. No. 2,672,070 entitled “Wire Coil Screw Thread Insert for Molded Material,” for example. 
         [0003]    Generally speaking, tapped threads are strengthened due to the inherent strength of such helically coiled wire inserts. 
         [0004]    Notwithstanding the utilization of these threaded inserts, additional locking performance of a threaded fastener&#39;s engagement within a tapped hole may be enhanced by means of specific locking thread construction, as described in U.S. Pat. Nos. 4,076,064 and 4,171,012. These prior art locking thread designs effectively utilize a ramped thread form to more evenly distribute the load over a longer length of engagement. 
         [0005]    Although the prior art discloses a wide variety of different types of wire insert concepts, none teach or suggest incorporating a locking thread form for achieving the benefits of increased strength of the fastener and threaded hole. Furthermore, there is a lack in the art of a preload locking wire insert which may further provide for the insertion of the insert in either direction, without regard to orientation, while still retaining the locking capabilities on the wire insert disclosed herein. 
       SUMMARY 
       [0006]    Therefore, it is an object of the invention to provide a novel and improved self-locking threaded connection which is more reliable than heretofore known self-locking connections. 
         [0007]    It is a further object of an additional embodiment of the present invention to provide a preload locking wire insert which is designed to be inserted into a threaded hole unidirectionally, which more evenly distributes the load over a given length of engagement. 
         [0008]    It is a further object of an additional embodiment of the present invention to provide a further embodiment of the preload locking wire insert which may be inserted into a threaded hole in either direction, without regard to orientation, while still allowing a fastener to be locked there within. 
         [0009]    A further object of the present invention is to provide a helical threaded insert which has a reduced cross-section created by a series of pinched coils, allowing for the prevailing torque capabilities of a threaded fastener within a threaded hole when placed in the threaded hole. 
         [0010]    A further object of the present invention is that it does not cause damage to the work piece during installation, as by shaving or similar action. 
         [0011]    These and other advantages of the present invention will become apparent from the drawings and detailed description of the invention provided below, describing a preload locking wire insert comprised of a unitary, extruded, and coiled wire having a particular polygonal cross-section for use in combination with a threaded fastener and a complementary threaded bore in a material, wherein the wire insert provides a ramping surface which locks the threads of a male fastener into place against the inner threaded wall of a bore in a given material. In a further embodiment, the particular cross-section provides for the wire insert to be threaded into the hole in either direction, with no regard to orientation, while still retaining the definitive locking aspect. 
         [0012]    As detailed in the additional embodiments, the present invention may contain features such as installation-assisting notches and/or one or more prevailing torque locking coils, positioned along the length of the wire insert, which provide additional securement of the fastener within the threaded hole. 
         [0013]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0014]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0015]      FIG. 1  is a pre-assembled perspective view showing the installation orientation of the wire insert, threaded fastener, and the receiving hole; 
           [0016]      FIG. 2  is a post-assembled, cross-sectional view of a prior art wire insert, threaded fastener, and receiving hole similar to  FIG. 1 ; 
           [0017]      FIG. 3  is a perspective, isolated view of the preload locking wire insert embodying an installation notch; 
           [0018]      FIG. 4  is a bottom view of the locking wire insert of  FIG. 3 ; 
           [0019]      FIG. 5  is a perspective, isolated view of the preload locking wire insert, illustrating the cross-section of the wire which provides the locking means; 
           [0020]      FIG. 5A  is a perspective, isolated view of the preload locking wire insert, illustrating a plurality of prevailing torque locking coils in association therewith; 
           [0021]      FIG. 5B  is an aerial view of the prevailing torque locking ring elements of  FIG. 5A ; 
           [0022]      FIG. 6  is a cross-sectional view of the extruded wire insert, as shown, prior to coiling; 
           [0023]      FIG. 7  is a cross-sectional view of the wire insert, after coiling, yielding the locking design of the wire insert; 
           [0024]      FIG. 8  is a partial cross-sectional side view of the preload locking wire insert positioned within a threaded hole in a work piece; 
           [0025]      FIG. 9  is a partial cross-sectional side view of the preload locking wire insert positioned within a threaded hole in a work piece in conjunction with a threaded fastener prior to tightening; 
           [0026]      FIG. 10  is a partial cross-sectional side view of the preload locking wire insert positioned within a threaded hole in a work piece in conjunction with a threaded fastener after tightening the fastener down, locking the fastener into place; 
           [0027]      FIG. 11A  is a perspective, isolated view of the bi-directional, preload locking wire insert embodying an installation notch; and 
           [0028]      FIG. 11B  is a cross-sectional side view of the bi-directional locking wire insert of  FIG. 11A . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that, throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0030]    Referring now to the figures, in particular to  FIG. 1 , the preload locking wire insert  20 , threaded fastener  10 , and receiving hole  15  within a given work piece  14  are shown prior to assemblage. The receiving hole  15 , within which the locking insert may be utilized, may be within any type of medium, but generally aluminum, titanium, or steel alloys thereof will be discussed herein. The receiving hole  15  comprises a series of bored-out threads  16  within the inner wall, corresponding to the pitch of the wire insert  20  and threaded shank  12  of the threaded fastener. As illustrated in this figure and shown in further detail in  FIGS. 11A and 11B , one embodiment of the present invention is shown which provides for the wire insert  20  to be orientated in either direction with regard to the fastener  10  and the hole  15 . 
         [0031]    Prior art wire inserts  17 , as illustrated in  FIG. 2 , generally have a symmetrical cross-section comprised of a diamond-shape. Although these fasteners may assist in securing the fastener to a work piece  14 , they do not provide the additional locking feature provided by the particular design of the present invention, and thus fail to achieve the objectives accomplished by this invention. 
         [0032]    As shown in  FIGS. 3 and 4 , additional embodiments of the present invention may include a notch  22  proximal one or both ends of the wire insert  20 . This notch allows for simplified installation of the wire insert within the hole of a work piece, prior to the installation of a male threaded fastener. The series of coils  24  can be comprised of any number, depending upon the particular application with which the insert  20  is utilized, and the coils  24  are subsequently turned to yield a particular pitch for the insert  20 , corresponding to the pitch of the threads  16  within the hole  15  and the threads  12  on the fastener  10 . 
         [0033]    Referring now to  FIGS. 5 ,  6 , and  7  together, the cross-section of the preload locking wire insert  20  is shown, illustrating the particular design which yields the locking capabilities of the insert  20 . The insert prior to coiling is of a generally oblong cross-section  21  as shown in  FIG. 6 , created by extruding the wire by means of a roll-extrusion process. Once the wire is extruded, the distinctive final cross-section of insert  20 , as shown in  FIG. 7 , is formed by coiling the wire, yielding the end result illustrated in  FIG. 5 . The extrusion and coiling processes yield the definitive cross-section of the insert  20 , comprising an upper thread surface  25 , a lower thread surface  26 , a major diameter  27 , an inner lower fastener cooperating surface  28 , and an inner upper fastener cooperating surface  29 . 
         [0034]    The particular positioning of the preload locking wire insert  20  can be shown in place within the hole  15  of work piece  14  in  FIG. 8 . The inner walls of the hole  15  comprise a plurality of threads  16  bored or molded therein. Each thread  16  comprises lower beveled surface  19  and an upper beveled surface  18 . When wire insert  20  is inserted within the hole  15 , the upper thread surface  25  of each coil  24  of the insert  20  cooperates with upper beveled surface  18  of thread  16 , and the lower thread surface  26  cooperates with lower beveled surface  19 , creating a snug fit of insert  20  within the hole  15 . 
         [0035]    Referring now to  FIGS. 9 and 10 , threaded fastener  10  is shown partially inserted and fully inserted and tightened down, respectively, locking the fastener in place with the insert  20 . With the wire insert  20  already in place within hole  15 , the fastener  10  is threaded into the insert, whereby the upper thread surface  120  of the threads  12  of fastener  10  slidingly engage the inner, upper fastener cooperating surface  29  of the insert as shown in  FIG. 9 . A small gap  34  remains between the upper thread surface  120  of the threads  12  and the lower fastener cooperating surface  28  of the insert, which indicates the fastener  10  is not locked into place and further allows for the ease of inserting the fastener into the insert. Once the fastener  10  is fully inserted, illustrated by  FIG. 10 , additional torquing of the fastener head  11  locks the fastener into place by means of upward force imposed upon lower fastener cooperating surface  28  of the insert by upper thread surface  120  of the threads  12 . The ramping force of upper thread surface  120  upon the lower fastener cooperating surface  28  creates a radially outward projected force of the insert  20 , which frictionally locks into threads  16  of the hole  15  in the work piece  14 . 
         [0036]    When fully locked into place, a small gap  36  remains between the lower thread surface  122  of threads  12  and the upper fastener cooperating surface  29  of the insert. It is pertinent to restate that, because the wire insert  20  of this embodiment may be inserted into the hole in either orientation while retaining the locking features of its design, the numerals indicating the upper and lower surface of the wire insert  29 ,  28  would be reversed, in regard to interacting with the surfaces of thread  16  on the inside of the hole, as well as the thread surfaces of fastener  10 . 
         [0037]    A further embodiment of the present invention is shown in  FIGS. 5A and 5B , wherein at least one prevailing torque locking coil  30  may be positioned among the standard coils  24 . These prevailing torque locking coils  30  are created post-extrusion of the wire insert, during or after coiling, and comprise a series of pinched corners  32 , which create generally linear sections of the wire there between. These linear sections create additional frictional force against the threads  12  of the fastener, while the pinched corners  32  create additional frictional force against the inner walls of hole  15 . In conjunction with the locking features outlined above, additional securement of the fastener  10  and insert  20  within the hole  15  of the work piece  14  is achieved. 
         [0038]    In a further embodiment of the present invention, it is to be noted that the wire insert  20  may be coated in one or more of a plurality of materials including, but not limited to, silver, cadmium, or a solid film lubricant prior to installation. 
         [0039]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.