Abstract:
The present invention is directed to a threaded insert having an internal threaded surface and an external threaded surface. The threaded surfaces have threads that are threaded in opposite directions. Thus, if the internal threaded surface is a right handed thread, then the external threaded surface will be a left handed thread. Through the use of the opposite direction threads the insert counteracts torque applied to a threaded fastener as it is inserted or removed. This results in a threaded insert that both resists over tightening of the fastener, and assists in the removal of the fastener from the insert.

Description:
TECHNICAL FIELD 
       [0001]    This application claims priority under 35 U.S.C. 119(e) from provisional U.S. Patent Application No. 60/909,260 filed Mar. 30, 2007, the contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to threaded inserts for connecting fastening devices to other components. More specifically, the present invention relates to a threaded insert for connecting a fastening device into a component material where corrosion or seizing is likely to occur. 
       BACKGROUND OF THE INVENTION 
       [0003]    Threaded inserts are commonly used to provide strength or prevent damage to soft or lightweight materials where a threaded fastener or other item is repeatedly inserted and removed from the material. Threaded inserts are placed in the associated material of a parent part such that the fastener can be inserted into the threaded insert. The threaded insert may be molded directly into the material. However, in other approaches the insert is screwed or otherwise rotated into the parent material. Once the threaded insert is connected to the parent material the fastener can be rotated into the insert, thereby connecting the fastener to the parent part. Often, the fastener is designed to be removed and reinserted into the threaded insert multiple times without causing damage to the underlying parent part. However, the design of typical inserts makes it difficult to remove fasteners that have become frozen, corroded, or otherwise locked into the insert without damaging the underlying parent material. Further, the design of many inserts makes it difficult to remove the insert from the material when recycling. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to a threaded insert having an internal threaded surface and an external threaded surface. The threaded surfaces have threads that are threaded in opposite directions. Thus, if the internal threaded surface is a right handed thread, then the external threaded surface will be a left handed thread. Through the use of the opposite direction threads the insert counteracts torque applied to a threaded fastener as it is inserted or removed. This results in a threaded insert that both resists over tightening of the fastener, and assists in the removal of the fastener from the insert. 
         [0005]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
           [0007]      FIG. 1A  is a perspective view of a threaded insert according to one embodiment; 
           [0008]      FIG. 1B  is a cut away view of a threaded insert; 
           [0009]      FIG. 2A  is a partial cut away view of a threaded insert molded into a parent component and a fastener; 
           [0010]      FIG. 2B  is a partial cut away view of a threaded insert inserted into a parent component and a fastener; 
           [0011]      FIG. 2C  is a cut away view of a threaded insert molded into a parent component, a threaded fastener and a removable component; 
           [0012]      FIG. 2D  is a cut away view of a threaded insert inserted into a material and a fastener; and 
           [0013]      FIG. 3  is a perspective view of a threaded insert according to an alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1A  is a perspective view of a threaded insert  100  according to at least one embodiment of the present invention.  FIG. 1B  is a cutaway view of threaded insert  100  according to at least one embodiment. For purposes of this discussion  FIGS. 1A and 1B  will be discussed together. Threaded insert  100  has an external threaded surface  110  and an internal threaded surface  120 . In contrast to previous threaded inserts the external threaded surface  110  is threaded in a direction opposite the direction of threading of the internal threaded surface  120 . 
         [0015]    In one embodiment, insert  100  is placed in a soft material such as plastic or aluminum where the repeated insertion and removal of an item, such as a fastener, directly into the material could damage the material. One embodiment of the design of insert  100  is especially advantageous in environments where corrosion is likely. Further, in one embodiment, insert  100  is formed as a zinc die cast and includes a 96+ hour salt spray corrosion resilient trivalent zinc plating. However, other materials can be used for insert  100 . 
         [0016]    In one embodiment external threaded surface  110  includes thread  111 , and internal threaded surface  120  includes thread  121 . Thread  111  and thread  121  are in one embodiment helical ridges that are disposed on surfaces  110  and  121 . Threads  111  and  121  can be formed, for example, cutting into the surface or during casting or molding of insert  100 . In one embodiment, thread  111  is a left handed thread, and thus thread  121  is a right handed thread. However, in other embodiments the direction of the threads can be reversed. In one embodiment, thread  111  has a pitch that is greater than the pitch of threads  121  on the internal surface. The arrangement of thread  111  versus thread  121  acts to counteract torque imparted by a threaded fastener as it is inserted into the insert. 
         [0017]    When placing threaded insert  100  into a material several approaches can be used. In one embodiment, insert  100  is rotated into the parent component. In this embodiment, insert  100  can be placed in a pre-bored hole that has been formed in the parent component, or can be a self drilling insert. In another embodiment, insert  100  is a self-tapping insert. In yet another embodiment, insert  100  is placed or molded in the parent material during manufacturing. However, other methods can be used. 
         [0018]    In one illustrative embodiment, thread  111  includes discontinuities or notches  112  in the thread that provide additional torque resistance when molded or rotated into a material. Depending on the method of insertion of the insert (molding or rotating) the notches operate in a slightly different manner in the material. In embodiments where insert  100  is molded into the material, notches  112  are surrounded by the molded material of the parent component. An insert  100  molded into the parent component  200  is illustrated in  FIG. 2A . This surrounding of parent component  200  provides additional torque resistance by hindering the rotation of the insert. In embodiments where the insert is rotated into the parent component, as illustrated for example in  FIG. 2B , the notches assist in holding the insert into the component or provide exit paths for material when self tapping. 
         [0019]    The threaded insert according to at least one embodiment of the present invention protects the underlying material during insertion of a threaded fastener  210  into the threaded insert  100 . During insertion threaded fastener  210  is rotated in such a manner that threads  211  of the fastener engage internal threads  121  of insert  100  as illustrated in  FIGS. 2C and 2D . 
         [0020]      FIG. 2C  illustrates removable component  205  connected to parent component  200  via threaded fastener  210  and insert  100 . In this example, threaded fastener  210  is passed through an aperture of removable component  205 . As threaded fastener  210  is rotated within insert  100 , removable component  205  and parent component  200  are drawn together. 
         [0021]    When end  212  of the fastener  210  reaches the bottom (stop surface) of thread  121  additional rotation of fastener  210  does not result in the additional tightening of the fastener  210  relative to the parent component  200  or removable component  205 . Instead, this rotational force is transferred to the insert  100  and causes insert  100  to rotate in a direction that would tend to remove the insert  100  from parent component  200 . Thus, the insert  100  acts to prevent over tightening of the fastener  210 . A similar function may be achieved by interaction between the other stop surface(s), the insert  100  and the fastener  210 . 
         [0022]    According to at least one embodiment, insert  100  is also designed to assist in the removal of fastener  210 , especially when the fastener has become fused or otherwise stuck in insert  100 . This usually occurs in environments where the fastener is likely to corrode such as high salt or high moisture areas. When removing fastener  210 , the fastener is rotated, for example, in an anti-clockwise direction. The anti-clockwise rotation of fastener  210  causes threads  211  of fastener  210  to travel along internal threads  121  of insert  100  such that fastener backs out of insert  100 . At the same time if the fastener has become fused to the insert the anti-clockwise rotation acts to cause external threads  111  to rotate insert  100  into component  200 . This creates an additional forces tending to release the fastener from the insert, while at the same time preventing the insert from breaking free from the material, and being removed from the material along with the fastener. 
         [0023]      FIG. 3  is a perspective view of threaded insert  300  according to one embodiment of the present invention. In this embodiment threaded insert  300  includes a blind internal thread. However, other types of threads can be used. The blind internal thread assists in keeping contaminates (such as plastic powder) out of the internal threads during molding of the material around the insert, or during the insertion of the insert into the parent component. 
         [0024]    Insert  300  also includes a torque coupling area  310 . Torque coupling area  310  assists in the insertion and/or removal of insert  300  from the parent component. Typically, the need to remove the insert arises from damage to the part during use or during the manufacturing process of the associated part. In prior art approaches the insert is removed using a costly and unsafe routering process to free the insert from the part. In one embodiment, torque coupling area  310  is a recessed area that is recessed into a portion of the insert. In the embodiment illustrated in  FIG. 3  the recessed area is a hex recess. The hex recess area allows the insert to be rotated when a corresponding hex is placed in the recess. However, other interfaces can be used, such as a flat head or Phillips head screwdriver interface. The torque coupled area and the external threads provide a simpler and safer means for recovering the insert  300  from the part prior to recycling. However, in other embodiments torque coupling area  310  can be a configured perimeter to assist in the insertion/removal of the insert. In these embodiments the configured perimeter can be arranged such that the insert can be engaged by a wrench or socket. Typically, the configured perimeter is raised above a top surface of the material. However, other configurations can be used. 
         [0025]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.