Abstract:
A hole saw plug ejector includes a mandrel having a threaded end and a hole saw cup with cutting teeth on a leading edge to cut a hole in material. A pilot bit is provided in the hole saw cutting end of the mandrel. A retaining nut for holding the hole saw cup to the mandrel includes inner and outer threads. The inner threads engage the threads on the mandrel and an ejector spring engages the outer threads to provide a simplified system for changing ejector spring sizes for different sizes of hole saw cups.

Description:
REFERENCE TO MICROFICHE APPENDIX 
       [0001]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to the field of hole saws. In particular, the invention relates to a hole saw plug ejector that ejects the plug formed when a hole saw cuts a plug of material. 
         [0004]    2. Description of the Related Art 
         [0005]    Hole saws and hole saw ejectors are generally known in the art. When a conventional hole saw drills a hole, the circular cut out portion (referred to herein as the plug), which is formed from the cutting teeth of the hole saw cup, can get stuck inside the hole saw cup. Attempts have been made to eject the cut out portion. For example, U.S. Pat. No. 5,934,845 (“the &#39;845 patent”) shows a hole saw ejector having a tapered pilot bit and conical spring member. The conical spring in the &#39;845 patent is used for ejecting the cut out portion. 
         [0006]    Hole saws are used to cut many different materials, including but not limited to wood, metal, plastic and concrete. Some materials can be very difficult and time consuming to remove from the hole saw cup. 
         [0007]    When springs have been used as a plug ejector, there has been an inadequate structure to attach the spring inside of the hole saw cup. It would be desirable to have a structure and method that includes a way to attach easily the spring to the inside of the hole saw cup and a structure that allows for various sizes of hole saw cups that are used to form various sizes of holes. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    It is an object of the invention to provide a hole saw plug ejector that simplifies the ejection of the plug and that is useable on a wide range of sizes of hole saw cups and plug ejector springs. The inventive hole saw plug ejector generally comprises a mandrel having a threaded end and a substantially cylindrical saw blade cup having a leading edge. The leading edge of the hole saw cup includes cutting teeth for cutting a hole. A pilot bit is normally connected to the mandrel and the mandrel is connected to the saw blade cup. A retaining nut is included that has inner and outer threads. The retaining nut is threaded onto the threaded end of the mandrel. An ejector spring is threaded onto the outer threads of the retaining nut, whereby the spring ejects a cut hole that is formed by the saw blade cup. 
         [0009]    A snap ring groove can be provided at the distal end of the threads on the threaded end of the mandrel. A snap ring in the snap ring groove prevents the retaining nut from loosening up while allowing for simplified installation of the retaining nut. Because the snap ring prevents the retaining nut from loosening up, minimal torque need be imposed on the retaining nut. This will actually allow for the user to thread the retaining nut onto the mandrel by hand, thereby preventing over torque or wrench damage to the outer threads on the retaining nut. 
         [0010]    The outer thread diameter and the corresponding inner ejector spring diameter can increase as the hole size cup increases. Also, the ejector spring cross-section can be increased so that additional spring force is provided for larger plugs in larger hole saw cups. In this way, various size springs and spring force can be provided to assist with the removal of different sized plugs. 
         [0011]    Typically the inner threads on the retaining nut are universal fine threads and the outer threads on the retaining nut are universal course threads. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an isometric view of the inventive hole saw plug ejector. 
           [0013]      FIG. 2  is an assembly view of  FIG. 1 . 
           [0014]      FIG. 2A  shows the ejector spring with an optional disk. 
           [0015]      FIG. 3  is a sectional view of the inventive hole saw plug ejector taken from line  3 - 3  of  FIG. 1 . 
           [0016]      FIG. 4  is a partial sectional view taken from  FIG. 3 . 
           [0017]      FIG. 5  is a sectional view taken from line  5 - 5  of  FIG. 4 . 
           [0018]      FIG. 6  is a partial sectional view of the inventive device showing one of several possible sizes of the retaining nut and ejector spring. 
           [0019]      FIG. 7  is a partial sectional view of the inventive device showing one of several possible sizes of the retaining nut and ejector spring with the hole saw cup, ejector spring and retaining nut being larger than the hole saw cup, ejector spring and retaining nut shown in  FIG. 6 . 
           [0020]      FIG. 8  is a partial sectional view of the inventive device showing one of several possible sizes of the retaining nut and ejector spring with the hole saw cup, ejector spring and retaining nut being larger than the hole saw cup, ejector spring and retaining nut shown in  FIG. 6  or  7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring now to  FIG. 1 , a perspective view of the inventive hole saw plug ejector is shown. Also refer to  FIG. 2  in which an assembly drawing of  FIG. 1  is shown. A conventional hole saw cup  104  includes cutting teeth  105 . The cutting teeth  105  are used to cut a hole in the desired material to the diameter of the hole saw cup  104 . An arbor  110  is inserted into the hole  114  in the hole saw cup  104 . Pins  120  may be included on the arbor  110  which fit into anti-rotation holes  120   a  on the top of the hole saw cup  104 . When the pins  120  are engaged with the anti-rotation holes  120   a , they prevent the hole saw cup  104  from rotating when it is being used to cut a hole in material. The shank  106  is secured and rotated by a power or hand drill (not shown). 
         [0022]    Retaining nut  126  typically has inner threads  130  and outer threads  128 . The inner threads  130  thread onto the arbor threads  112  to secure the hole saw cup  104  to the arbor  110 . A pilot bit  109  is inserted into the arbor end  134  and is typically secured with a setscrew  122  (shown in  FIG. 2 ). The pilot bit  109  is used to provide an accurate starting position for the hole saw cup  104  when beginning the cutting of a hole in the desired material. 
         [0023]    The ejector spring  108  is normally threaded onto the outer threads  128  of the retaining nut  126 . The outer threads  128  on the retaining nut  126  provide a simple and secure connection between the retaining nut  126  and the ejector spring  108 . The outer threads  128  also allow for multiple sizes of retaining nuts  126  to be provided with multiple sizes of ejector springs  108  and multiple sizes of hole saw cups  104 . The retaining nuts  126 , ejector springs  108  and hole saw cups  104  may be provided for example, as a kit for end users. 
         [0024]    Refer now to  FIG. 3 , in which a cross section view taken from line  3 - 3  from  FIG. 1  is shown. The ejector spring  108  is shown threaded onto the outer threads  128  of the retaining nut  126 . The outer end of the ejector spring  108  is shown extending beyond the cutting teeth  105  of the saw hole cup  104  but below the end of the pilot bit  109 . This allows the pilot bit  109  to begin the pilot hole without the ejector spring  108  interfering with the positioning of the pilot bit  109  when drilling the pilot bit hole. After a hole has been drilled with the pilot bit  109 , the ejector spring  108  is then compressed against the plug to build up the potential energy stored in the ejector spring  108 . After a hole has been cut with the hole saw cup  104 , the energy in the compressed ejector spring  108  is released against the plug to eject it from the inside of the hole saw cup  104 . It is contemplated that a substantially flat disk  140  as shown in  FIG. 2A  may be placed, welded or otherwise secured on the distal end of the ejector spring  108  if desired. The disk  140  includes a hole  142  for the pilot drill  109  to pass through. The disk  140  can reduce friction between the end of the ejector spring  108  and the material that is being cut. 
         [0025]    Referring to  FIG. 4 , a snap ring  132  is shown in a snap ring groove  132   a . The snap ring groove  132   a  is positioned at the distal end of the arbor threads  112  and above the retaining nut  126  when the retaining nut  126  is substantially threaded onto the arbor threads  112 . The arbor end  134 , top of retaining nut  126  and snap ring  132  are also shown in  FIG. 5 , which is a section view taken along line  5 - 5  from  FIG. 4 . The snap ring  132  secures the retaining nut  126  on the arbor threads  112  even if the retaining nut  126  is not fully tightened. This can be important because the retaining nut outer threads  128  might be damaged if excessive torque were to be applied to them when the retaining nut  126  is being threaded onto the arbor threads  112 . Moreover, the retaining nut  126  can be tightened by hand, which will also avoid damaging the outer threads  128  and will allow the easy change out of different retaining nuts  126  to be used with different sized ejector springs  108 . 
         [0026]    The retaining nut inner threads  130  are normally universal fine threads and the retaining nut outer threads  128  are normally universal course threads. The ejector spring  108  inner diameter corresponds to the size of the retaining nut outer thread  128  diameter. The retaining nut inner threads  130  and outer threads  128  are normally right hand but they may also be left hand threads, if desired. 
         [0027]    In  FIG. 6  the hole saw cup  104  is shown larger than the hole saw cup  104  in  FIGS. 3 and 4 . The outer diameter of the retaining nut  126  is also shown larger than the retaining nut  126  shown in  FIGS. 3 and 4 . The outer diameter of the retaining nut  126  is larger so that the larger ejector spring  108  can be threaded onto the retaining nut outer threads  128 . 
         [0028]    In  FIG. 7  the hole saw cup  104  is shown larger than the hole saw cup  104  in  FIGS. 3 ,  4  and  6 . The outer diameter of the retaining nut  126  is also shown larger than the retaining nut  126  shown in  FIGS. 3 ,  4  and  6 . The outer diameter of the retaining nut  126  is larger so that the larger ejector spring  108  can be threaded onto the retaining nut outer threads  128 . Also note that the cross section of the ejector spring  108  is larger in  FIG. 7  than the cross section of the ejector spring  108  in  FIGS. 3 ,  4  and  6 . The larger cross section provides the ejector spring  108  with a larger spring constant, which caused it to be stiffer. A stiffer spring will tend to eject a plug with more force than a less stiff spring that has a lower spring constant. Also note that the threads on the retaining nut outer threads  128  correspond to both the inner diameter and the cross section of the ejector spring  108 . The thread pitch of the retaining nut outer threads  128  can also be changed to correspond to the spacing between coils of the ejector spring  108 . 
         [0029]    In  FIG. 8  the hole saw cup  104  is shown larger than the hole saw cup  104  in  FIGS. 3 ,  4 ,  6  and  7 . The outer diameter of the retaining nut  126  is also shown larger than the retaining nut  126  shown in  FIGS. 3 ,  4 ,  6  and  7 . The outer diameter of the retaining nut  126  is larger so that the larger ejector spring  108  can be threaded onto the retaining nut outer threads  128 . The cross section of the ejector spring  108  is larger in  FIG. 8  than the cross section of the ejector spring  108  in  FIGS. 3 ,  4 ,  6  and  7 . The larger cross section provides the ejector spring  108  with a larger spring constant, which causes it to be stiffer. A stiffer spring will tend to eject a plug with more force than a less stiff spring that has a lower spring constant. Also note that the threads on the retaining nut outer threads  128  correspond to both the inner diameter and the cross section of the ejector spring  108 . 
         [0030]    While several embodiments and elements of the invention have been shown and described, it should be understood that other variations and elements will be apparent to those skilled in the art. Therefore, it will be understood that the embodiments and elements shown in the drawings and described herein are merely for illustrative purposes, and are not intended to limit the scope of the invention, which is defined by the claims, which follow.