Patent Publication Number: US-7220169-B2

Title: Sharpening apparatus

Description:
This application is a continuation of International Application No. PCT/GB2003/03453, filed 7 Aug. 2003. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a sharpening apparatus for blade-like cutting implements and, in particular, to a sharpening apparatus for the sharpening of plane blades or chisels, as used in woodworking. 
   Generally plane blades or chisels have an elongate body and a cutting edge located at one end of the body. 
   The cutting edge is normally rectilinear, and is defined at the transition between an inclined face ground at a predetermined angle on one side face of the body, and the opposite face of the body. 
   The cutting edge normally extends across the width of the blade body at a predetermined angle, usually 90°, to the longitudinal axis of the elongate body. 
   It is desirable, when re-sharpening a plane blade or chisel, to re-grind the inclined face at the same angle as it was originally ground relative to said one side face, and also to grind along the inclined face such that the cutting edge extends across the width of the body at the said predetermined angle. 
   According to one aspect of the present invention there is provided a sharpening apparatus for a blade-like cutting implement having an elongate body and a cutting edge extending widthwise across one end of the body at a predetermined angle relative to the longitudinal axis of the body, the cutting edge being formed by an inclined face formed on one side face of the body, the apparatus including a cradle for holding a blade-like implement to be sharpened and a mounting body for mounting the cradle relative to a grinding surface, the cradle being mounted on a pair of guide rails for movement along a rectilinear path, the cradle including first and second rail followers slidably connected to a first and second of the guide rails respectively, the cradle including a seat for locating the blade-like implement at a preselected reference position on the cradle such that the cutting edge of the implement to be sharpened is located parallel to said rectilinear path, the first rail and/or the first rail follower being adjustably mounted to enable the lateral position of the rectilinear path to be adjusted. 

   
     Various aspects of the invention are hereinafter described with reference to the accompanying drawings in which: 
       FIG. 1  is a perspective view of a sharpening device incorporating the sharpening apparatus according to an embodiment of the invention; 
       FIG. 2  is a partial cross-sectional view of the sharpening apparatus of  FIG. 1  along the line I-I; 
       FIG. 3  is a partial cross-sectional view of the sharpening apparatus of  FIG. 1  along the line II-II; and 
       FIG. 4  is a perspective view of the sharpening apparatus of  FIG. 1  when the cradle is detached from the second guide rail. 
   

   Referring initially to  FIG. 1  there is shown a sharpening device  10  which includes a grinding wheel  12  mounted on the drive shaft of an electric motor housed within a housing  14 . 
   A sharpening apparatus  16  is removably mounted on the housing  14 . The attachment includes a mounting body  18  which is detachably attached to the housing  14  via a tongue and groove arrangement  20 . The mounting body  18  includes a pair of generally parallel rails  22 , 24  that are spaced a predetermined distance apart, and extend widthwise of the mounting body  18  to define a rectilinear path. 
   The sharpening apparatus  16  also includes a cradle  26  slidably mounted on the rails  22 , 24  for movement along the rectilinear path. 
   A first  22  of the pair of rails is a rod-shaped member. The cradle  26  is slidably mounted thereon by means of first rail followers in the form of outwardly extending limbs  28 , 30  having apertures  32 , 34  therein through which the first rail  22  extends. 
   As shown in  FIG. 2 , the first rail  22  is preferably mounted at each end on an eccentric  58  rotatably supported in the mounting body  18 . The eccentrics  58  thereby provide an adjustment means for adjusting the lateral position of the rectilinear path. An adjustment knob  59  is preferably connected to the eccentric  58  at one end of the first rail  22  to facilitate rotation of the first rail  22  and thereby adjustment of the lateral portion of the rectilinear path. 
   The second  24  of the pair of rails is formed as a flange and extends outwardly from the mounting body  18 . The cradle  26  is slidably mounted on the second rail  24  by means of a second rail follower in the form of an outwardly extending arm  36 . The arm  36  is connected to the cradle  26  at one end, and includes a recess  38  at its other end that is shaped to receive the second rail  24  therein. 
   As shown in  FIG. 3 , the arm  36  is preferably received at its one end in a recess  25  formed in the cradle  26 , and is preferably adjustably connected at its one end to the cradle  26  by means of a plurality of teeth  40  formed along an edge thereof and adapted to engage teeth  42  formed on a sprocket wheel  44  housed in the cradle  26 . 
   The cradle  26  includes an adjustment knob  46  ( FIG. 1 ) operably connected to the sprocket wheel  44  to facilitate adjustment of the angular position of the sprocket wheel  44  relative to the teeth  42  formed on the arm  36 . 
   The separation between the cradle  26  and the second rail  24  is determined by the length  1   a  of the portion of arm  36  extending from the recess  25 . The length of the arm  36  may be adjusted by turning the adjustment knob  46  such that engagement between the teeth  40  on the arm  36  and the teeth  42  on the sprocket wheel  44  drives the arm  36  into or out of the recess  25  formed in the cradle  26 . 
   By adjusting the length  1   a  of the portion of arm  36  extending from recess  25 , and thereby the separation between the cradle  26  and the second rail  24 , the angular position of the cradle  26  may be adjusted about the longitudinal axis P a  of the first rail  22 . 
   In other embodiments, the angular position of the cradle  26  may be adjusted about the longitudinal axis of the first rail  22  by adjusting the position of the second rail  24  relative to the arm  36  in addition to, or as an alternative to adjusting the length of the arm  36 . 
   The arm  36  is preferably shaped to form a curved member. The curvature of the arm  36  provides a certain degree of resilience thereby providing a bias that helps to maintain the recess  38  in engagement with the second rail  24 . The resilience however may permit a user to disengage the arm  36  from the second rail  24 , when required, in order to reveal a blade seat  48 , as shown in  FIG. 4 . 
   The cradle  26  includes a seat  48  for holding a blade-like implement to be sharpened against a fixed edge  50  extending generally perpendicular to the longitudinal direction of the rectilinear path. 
   The seat  48  preferably includes a channel  52  formed therein that extends generally parallel to the longitudinal direction of the rectilinear path and has a rail  54  provided therein extending along the length thereof. 
   A movable block  56  is slidably mounted on the rail  54 . 
   In use, the mounting body  18  is mounted on the housing  14  of the sharpening device  10  such that the rectilinear path defined by the rails  22 , 24  extends across an exposed face of the grinding wheel  12 . 
   When a blade-like implement is positioned on the seat  48  with its cutting edge facing the first rail  22 , the movable block provides an adjustable means for holding the blade-like implement against the fixed edge  50  such that the cutting edge is located parallel to the rectilinear path. 
   The adjustable mounting of the first rail  22  provides means for adjusting the lateral position of the rectilinear path, and thereby provides means for adjusting the lateral position of the cutting edge of the blade-like implement, in use, relative to the grinding wheel  12 . 
   The adjustable mounting of the cradle  26  relative to the second rail  24  provides means for adjusting the angular position of the cradle  26  about the longitudinal axis P a  of the first rail  22 . This in turn enables the angle of the inclined face of the cutting edge of the blade-like implement to be adjusted relative to the rectilinear path and thereby adjusted relative to the grinding wheel  12 . 
   The slidable mounting of the cradle  26  on the first and second rails  22 , 24  permits sliding movement of the cutting edge of the blade-like implement along the rectilinear path. It thereby permits sliding movement of the cutting edge, in use, relative to the grinding wheel  12 . 
   The provision of a detachable arm  36 , permitting disengagement of the cradle  26  from the second rail  24 , enables a user to inspect the cutting edge of the blade-like implement during the sharpening process.