Abstract:
A grinding tool with a toll rest includes an adjustment mechanism to adjust the position of the tool rest responsive to wear of the grinding wheel.

Description:
RELATED APPLICATIONS 
   This application claims priority under 35 U.S.C. § 119(e) from the following provisional application: U.S. Provisional Application Ser. No. 60/480,463 filed on Jun. 20, 2003. That application is incorporated in its entirety by reference herein. 

   SUMMARY OF THE INVENTION 
   The invention relates to a grinder with an adjustable tool rest to maintain a relatively constant distance between the tool rest and the grinding wheel as the grinding wheel wears down. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of a grinding wheel according to a first embodiment. 
       FIG. 2  is a side elevational view of a grinding wheel according to a second embodiment. 
       FIG. 3  is an end view of the grinding wheel in the second embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1–3  show a grinder  10  according to a various embodiments of the invention. The grinder  10  comprises a base  12 , a grinding wheel  14  rotatably mounted to the base  12 , and a motor  15  for rotating the grinding wheel  14 . The motor  15  may drive the grinding wheel  14  directly. Alternatively, the driving force may be transmitted from the motor  15  to the grinding wheel  14  via a drive train. The particular manner of supporting and driving the grinding wheel  14  is not a material aspect of the invention. 
   A tool rest  16  is movably mounted to the base  12 . The function of the tool rest  16  is to support a tool, such as a chisel, or other work piece while grinding. In broad terms, the invention comprises a mechanism for maintaining the spacing between the tool rest  16  and the grinding wheel  14  as the grinding wheel  14  wears down. Various mechanisms for maintaining the spacing between the tool rest and the grinding wheel are described. 
   In the embodiment shown in  FIG. 1 , the tool rest  16  comprises an angularly-adjustable resting plate  18  pivotably mounted to the upper end of a vertical support member  20 . The vertical support member  20  is pivotably mounted at its lower end to the base  12 . A guide roller  22  is mounted to an intermediate portion of the vertical support  20  and is adapted to engage the outer edge of the grinding wheel  14 . A spring or other biasing member  24  applies a biasing force to the tool rest  16  to move the tool rest toward the grinding wheel  14  until the guide roller  22  engages the grinding wheel  14 . One end of the spring  24  connects to the vertical support and the other end of the spring  24  connects to a spring arm  26  attached to the base  12 . The spring  24  holds the guide roller  22  in contact with the grinding wheel  14  as the grinding wheel  14  wears down, thereby maintaining the spacing between the tool rest  16  and the grinding wheel  14 . 
   In an alternate embodiment shown in  FIG. 2 , an optical detector  30  is used to detect the outer circumference of the grinding wheel  14 . The optical detector  30  may comprise a single beam or multiple beams of light. A microprocessor  32  and servo motor  34  adjust the position of the tool rest  16  based on the output signal from the optical detector. The servo-motor  34  drives a shaft  36  that connects to the vertical support  20 . 
   Other elements of my invention which may be used with either embodiment include an adjustment mechanism for adjusting the tension on the biasing spring  24 , and an anti-kickback device  28  to prevent the tool rest from kicking back when an object gets caught in the gap between the tool rest and grinding wheel. A safety mechanism could also be provided to shut off power to the grinding wheel  14  when kickback is detected. 
   Those skilled in the art will recognize that the invention may be modified in various ways. For example, the tool rest could be mounted for linear movement, rather than rotational movement as shown in  FIGS. 1 and 2 . Also, in the second embodiment, detectors other than optical detectors could be used to detect the outer circumference of the grinding wheel. Such variations are within the scope of my invention.