Patent Publication Number: US-2006013671-A1

Title: Threaded insert with multi-lobe broach

Description:
TECHNICAL FIELD  
      The present invention relates to threaded inserts for machinery and, more particularly, relates to a threaded insert with a multi-lobed broach for receiving a removal tool.  
     BACKGROUND OF THE INVENTION  
      Threaded inserts have been used to replace worn or stripped threaded holes in machinery for many years. A threaded insert is a short, hollow cylinder threaded on both sides to permit replacement of the inner thread when it becomes worn or stripped. The outer threads screw into a bolt hole in a piece of machinery, and a bolt screws or other threaded fastener threads into the inner thread. When the inner thread becomes worn or stripped, a removal tool, such as a screwdriver, is employed remove and replace the threaded insert.  
      Although threaded inserts have been in use for years, conventional threaded inserts include a flat-head screwdriver removal tool socket for removing and replacing the insert. This type of removal tool socket is typically employed because it is easy to cut into the insert. The flat-head screwdriver removal tool socket can itself become stripped, however, which makes the threaded insert difficult to remove. Accordingly, there is an ongoing need for a threaded insert with a removal tool socket that is not susceptible to stripping.  
     SUMMARY OF THE INVENTION  
      The present invention meets the needs described above in a threaded insert with a multi-lobed broach for receiving a removal tool. The multi-lobed broach, such as a six-lobed socket, is not susceptible to being stripped by the removal tool to the same degree as a conventional flat-head screwdriver socket. Although conceptually simple, the need for this improvement in threaded inserts has remained unmet for many years.  
      Generally described, the invention includes a threaded insert having a cylindrical body with an open end, an outer surface, and an internal channel having an inner surface. The threaded insert includes an outer thread on the outer surface for engagement with a piece of machinery and an inner thread on the inner surface for engagement with a threaded fastener. The threaded insert also includes a multi-lobed broach at the open end for receiving a removal tool. The threaded insert also typically includes a closed end opposite the open end. A typical broach includes six lobes.  
      The invention may also be practiced as a method for manufacturing a threaded insert including a cylindrical body having an open end, an outer surface, and an internal channel having an inner surface. An outer thread is machined on the outer surface of the cylindrical body for engagement with a piece of machinery. A multi-lobed broach is also machined at the open end of the cylindrical body for receiving a removal tool. After the broach has been formed, an inner thread is machined on the inner surface for engagement with a threaded fastener. Cutting the inner thread after the broach prevents the cutting of the broach from damaging the inner thread.  
      In view of the foregoing, it will be appreciated that the present invention provides an improved threaded insert. The specific techniques and structures for implementing the threaded insert, and thereby accomplishing the advantages described above, will become apparent from the following detailed description of the embodiments and the appended drawings and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of an illustrative threaded insert.  
       FIG. 2  is an end view of the threaded insert.  
       FIG. 3  is a cross-sectional side view of the threaded insert. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
      The present invention may be employed as a threaded insert for virtually any type of machinery that uses threaded fasteners. In particular, the threaded insert is well suited to the corrugated board industry, where it may be used in a variety of applications such as attaching printing, slotting, scoring and cutting dies to rollers or drums. Of course, there are many other applications in the corrugated board and other industries for threaded inserts. For example, it is presently believed that the threaded insert will be particularly useful in the aviation industry and other high-vibration applications in which treaded fasteners are used, such as automobiles, ships, refinery equipment, power plants, and so forth. Nevertheless, is should be understood that the present invention is not limited to any particular industry or application. It should also be understood that threaded inserts can be provided in a variety of lengths, inner diameters, outer diameters, thread specifications and broach designs.  
       FIG. 1  is a side view of a typical threaded insert  10  showing dimensions and manufacturing specifications of this particular example.  FIG. 2  is an end view of the threaded insert, and  FIG. 3  is a cross-sectional side view of the threaded insert. As shown in the figures, the threaded insert  10  includes a cylindrical body  12  with an open end  14 , an outer surface  16 , and an internal channel  18  having an inner surface  20 . The insert includes an outer thread  22  on the outer surface for engagement with a piece of machinery and inner thread  24  on the inner surface for engagement with a threaded fastener. The insert also includes a multi-lobed broach  26  at the open end  14  for receiving a removal tool. The insert also typically includes a closed end  28  opposite the open end. The first thread  22  may be self-tapping. A typical broach includes six lobes, as shown in  FIG. 2 .  
      The threaded insert  10  is manufactured by cutting or stamping a cylindrical blank, typically from steel. The internal channel  18  is then drilled into the blank. The multi-lobed broach  26  should be cut into the inner surface  20  at the open end  14  of the blank before the inner thread  24  is machined into the inner surface. This prevents damage to the inner thread  24  from the cutting of the broach  26 . The threads may be machined into the insert using a milling machine or any other suitable technique.  
      In view of the foregoing, it will be appreciated that present invention provides significant improvement in threaded inserts. It should be understood that the foregoing relates only to the exemplary embodiments of the present invention, and that numerous changes may be made therein without departing from the spirit and scope of the invention as defined by the following claims.