Abstract:
The present invention permits a screw or male member to align prior to entering a threaded section and being driven. This alignment can avoid cross threading of the screw and the internal threads as often happens with power driven screws. The present invention generally includes a device with an unthreaded section and a threaded section. A screw or male member passes through the unthreaded section prior to entering the threaded section and causes the screw or male member to be aligned before being driven.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. patent application Ser. No. 09/662,736, filed Sep. 15, 2000, now allowed, which claims the benefit of U.S. Provisional Patent Application No. 60/215,252, filed Jun. 30, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    One problem that assemblers, machine builders, manufacturers, mechanics and the like have is cross threading internal threads. When assembling of devices was performed by hand, cross threading of internal threads did not occur frequently. But, products are now increasingly assembled using power devices. Cross threading occurs more frequently when using powered devices such as electric screw drivers and power guns.  
           [0003]    Cross threading of internal threads can be especially problematic for fixed devices and inserts as opposed to nuts. Once a device has female threads and they become cross threaded, the device may be unusable. Cross threaded inserts can be extremely difficult or impossible to remove or replace. Often, cross threading internal threads means that the part needs to be disposed of which could be a very costly problem. Cross threading or the occurrences of cross threading need to be reduced. Accordingly, there is a need in the art for a device which reduces cross threading.  
         SUMMARY OF THE INVENTION  
         [0004]    This need is met by the present invention, where an anti-cross threading device is disclosed. The device includes an element, a cylindrical cavity, an unthreaded section and a threaded section. The element has an exterior surface. The cylindrical cavity is in the element extending from the surface to a first length. The cylindrical cavity has an interior surface. An unthreaded section of the interior surface extends from the element surface to a second length. The threaded section of the interior surface extends from the second length to the first length. Other devices and methods of fabrication are disclosed. The present invention permits a screw or male member to align prior to entering a threaded section. This alignment can avoid cross threading. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 illustrates a cross sectional view of a conventional screw and insert.  
         [0006]    [0006]FIG. 2 illustrates a cross sectional view of a screw and anti-cross threading insert according to one embodiment of the invention.  
         [0007]    [0007]FIG. 3 illustrates an assembly utilizing anti-cross threading inserts according to another embodiment of the invention.  
         [0008]    [0008]FIG. 4 illustrates a cross sectional view a an anti-cross threading element according to another embodiment of the invention.  
         [0009]    [0009]FIG. 5 illustrates an anti-cross threading insert according to another embodiment of the invention.  
         [0010]    [0010]FIG. 6 illustrates a method for fabricating an anti-cross threading device according to another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0011]    [0011]FIG. 1 illustrates a screw  101  and a conventional insert  102 . The conventional insert has internal threads  103  extending from top to bottom. The screw  101  has external threads  104  which match the internal threads  103  of the insert. The screw  101  is shown slightly mis-aligned with respect to the insert  102 . Any turning or driving of the screw  101  will likely cause cross threading of the internal threads  103  or the external threads  104 .  
         [0012]    [0012]FIG. 2 illustrates a screw  201  and an anti-cross threading insert  202  according to one embodiment of the invention. The anti-cross threading insert  202  includes an unthreaded section  205  and internal threads  203 . The internal threads  203  correspond to the external threads  204 . The unthreaded section  205  is at least as wide as the major diameter of screw  201 . The screw  201  will not be misaligned before the external threads  204  encounter the internal threads  203  and thus, prevent cross threading of the internal threads  203  or the external threads  204 . This contrasts to the prior art FIG. 1, where the screw  101  should be aligned with the insert  102  prior to entering the insert  102  to avoid cross threading of the internal threads  103  or the external threads  104 .  
         [0013]    [0013]FIG. 3 illustrates an assembly  310  utilizing anti-cross threading inserts  202  according to another embodiment of the invention. The anti-cross threading inserts  202  are inserted into the assembly  310  as shown. Another assembly or part (not shown) can be attached to the assembly  310  by driving a conventional screw (not shown) into at least one of the anti-cross threading inserts  202 .  
         [0014]    [0014]FIG. 4 illustrates a cross section of an anti-cross threading element according to another embodiment of the invention. The element is located or formed in a structure  401 . The structure can be some type of device or a sheet of material or any other structure that utilizes internal threading. The element comprises an unthreaded section  406  and a threaded section  405 . The unthreaded section has a length  407  and a diameter  402 . The unthreaded section  406  is tapered at the surface in this embodiment, but other embodiments may not have the unthreaded section tapered. The threaded section has a length  408  and an inner diameter  403  and an outer diameter  404  of the threads. The unthreaded section  406  diameter is greater than or equal to the outer diameter  404  of the threaded section  405 . The unthreaded section length  407  and threaded section length  408  can vary according to the application. Additionally, the inner diameter  403  and outer diameter  404  can vary according to the application. Further, the threads in the threaded section are not limited to any specific size, style or shape of threads.  
         [0015]    [0015]FIGS. 5A and 5B illustrate an anti-cross threading insert according to another embodiment of the invention. The exterior of the insert includes a lip  516  and a lower portion  517 . The lip  516  is at a first end of the insert into which a screw may enter. When the insert is used in an assembly, the lip  516  remains outside the assembly and limits the depth the insert is seated prior to a screw being driven into the insert. For this embodiment, the lip  516  has a length  510  of approximately 0.043 inches. The lip  516  has an outer diameter  512  of 0.307-0.315 inches. The lower portion  517  is adjacent to the lip  516  and is located along the same axis. The other end of the lower portion  517  is a second end of the insert. For this embodiment, the lower portion  517  includes three knurls  505  having a diameter of 0.256-0.259 inches and having a length  507  of 0.054 inches. The knurls  505  assist in gripping a base material. Between each knurl  505  is an unknurl section having a diameter  513  of 0.234 inches and a length  514  of 0.014 inches.  
         [0016]    The insert  501  includes an interior having an unthreaded portion  502  and a threaded portion  503 . The unthreaded portion  502  allows a screw to be aligned prior to entering or driving into the threaded portion  503 . The unthreaded portion  502  is located at the first end of the insert. The unthreaded portion  502  has a length of 0.100 inches in this embodiment. Typically, the unthreaded portion  502  has a length of approximately 2 to 3 threads. For this embodiment, the unthreaded portion  502  has a diameter of 0.195 inches. Additionally, the unthreaded portion  502  includes a chamfer  504 , a shallow angled cut, at the first end of the insert. The chamfer  504  has a 45 degree angle cut. However, other angles and sizes may be used for the chamfer  504 .  
         [0017]    The threaded portion  503  is axial and adjacent to the unthreaded portion  502  and ends at the second end. The threaded portion  503  includes internal threads. For this embodiment, the threads of the threaded portion  503  are STD national threads form class 2B fit. The threads are 10-32 threads and have a maximum eccentricity between internal and outer diameters of 0.002 T.I.R. The insert  501  has a length of 0.370 inches from the first end to the second end.  
         [0018]    In this particular embodiment, the insert  501  is comprised of brass. Other embodiments may utilize other materials such as aluminum, steel, plastic and the like. The insert  501  may prevent or reduce the occurrence of cross threading of internal threads.  
         [0019]    [0019]FIG. 6 illustrates a method for fabricating an anti-cross threading device according to one embodiment of the invention. A block of material is provided at  601 . The block of material can be an insert, nut, sheet of material or the like. Exterior features of the anti-cross threading device are formed on an outer surface of the block at  602 . The exterior features can include a head, shank, knurl and the like. A cylindrical cavity is formed in the block of material at  603 . The cylindrical cavity has a first diameter and a first depth. The first diameter is selected according to thread size. The first depth is selected to allow a screw or threaded male member to be securely attached to the anti-cross threading device. The cylindrical cavity is counter bored to a second depth and a second diameter forming an unthreaded section at block  604 . The second depth is less than the first depth and the second diameter is greater than or equal to the first diameter. A chamfer may be bored into the unthreaded section at block  605 . Threads are created in the remaining area or threaded area of the cavity at block  606 . The threads can be created by tapping. The threaded area is the portion of the cylindrical cavity that is not counter bored.  
         [0020]    Having described the present invention in detail and by reference to various embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention. The described embodiments and variations can be used to reduce the occurrence of cross threading and can properly align screws prior to setting screws. They may prevent screws from being inserted at an undesirable angle. They may also increase the speed and quality with which devices are manufactured. The embodiments and variations are especially helpful when power tools such as power guns are being used to drive screws into internal threads. The various embodiments can be used in the case of inserts in molded thermoset and thermoplastic plastic parts. The various embodiments can also be used in other materials which require threaded holes and are not limited to inserts.