Abstract:
A hand held, portable drill bit sharpener is provided which may be powered by a standard commercially available electrical power tool. The power tool may be used to actuate the drill bit sharpener by arranging the drive shaft of the sharpener into the power tool chuck. This drive shaft is connected through a gear set to a biased rotating sharpening stone which is pressed against a drill bit tip. The drill bit may be held in the sharpener using a standard keyless drill bit chuck.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS (IF APPLICABLE) 
     This application claims priority to U.S. Provisional Application Ser. No. 61/398,969 filed Jul. 6, 2010 which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to a drill bit sharpener and in particular to a drill bit sharpener that may be powered by a standard electrical power tool. 
     Professional carpenters and other construction professionals, as well as do-it-yourselfers, are often confronted with a drill bit becoming dull or even breaking with use. Once a drill bit is dulled, jobs cannot be completed as quickly, or with the same degree of quality as before. To avoid this situation the user has two options: The dulled or broken drill bit can be thrown away and a new drill bit purchased or the drill bit can be resharpened and used again. 
     The first option is wasteful, expensive and requires an inventory of drill bits be maintained, increasing operating costs for the operator. The resharpening option has the advantage of reusing drill bits many times and extending the useful life of a drill bit. However, drill bit sharpening tools tend to be stand-alone units that may be very expensive and are not easily accessible on a jobsite or in a remote work environment. This results in the drill user having to leave the job site, wasting time and reducing the worker&#39;s productivity. 
     Accordingly, while existing drill bit sharpeners are suitable for their intended purposes the need for improvement remains, particularly in providing a low cost, easy-to-use, portable, drill bit sharpening tool that may be easily transported to and about a job site. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a sharpener is provided. The sharpener includes a case having a shaft extending from a first end of the case, the shaft having a first end sized to couple with an electrical power tool. A gear train is coupled to the shaft. A grinding stone is operably coupled to the gear train, the grinding stone having a conical recess on one side. A drill chuck is coupled to the case opposite the shaft, the drill chuck being substantially axially aligned with the conical recess. 
     According to another aspect of the invention, another sharpener is provided. The sharpener includes a case having a hollow interior area. A shaft extends from a first end of the case, the shaft having a first end sized to couple with an electrical power tool. A first gear train is disposed within the hollow interior area and coupled to the shaft. A second gear train is disposed within the hollow interior area and coupled to the first gear train. A grinding stone is operably coupled to the second gear train, the grinding stone having a conical recess a side opposite the second gear train. A drill chuck is coupled to the case opposite the shaft, the drill chuck being substantially axially aligned with the conical recess. 
     According to yet another aspect of the invention, yet another sharpener is provided. The sharpener includes a case having a hollow interior area. A shaft extends from a first end of the case, the shaft having a first end sized to couple with an electrical power tool. A first gear train is disposed within the hollow interior area and coupled to the shaft. A second gear train is disposed within the hollow interior area and coupled to the first gear train. A grinding stone is operably coupled to the second gear train, the grinding stone having a conical recess a side opposite the second gear train. A drill chuck is coupled to the case opposite the shaft, the drill chuck being substantially axially aligned with the conical recess. A slip collar is coupled for axial movement to the case, the slip collar being disposed between the grinding stone and the drill chuck. A spring is arranged within the hollow interior area to bias the grinding stone towards the slip collar. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is an exploded view of a drill bit sharpener in accordance with an embodiment of the invention; and 
         FIG. 2  is a side sectional view of the drill bit sharpener of  FIG. 1 . 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Drill bits, such as those used with electrical power tools are subjected to large amounts of wear during use. As a result, the drill bits will become worn or dull after a period of use, causing the operator to replace the drill bit or re-sharpen the bit edges. Embodiments of the invention provide a drill bit sharpener that is portable and may be readily transported, such as in a tool box or in a tool belt for example, to a desired operating location. The drill bit sharpener is configured to removably couple with an electrical power tool, which may be used to actuate the sharpener. Embodiments of the invention provide advantages in allowing an operator to quickly and easily re-sharpen a drill bit without having to leave the area where the work is being performed. 
     Referring to  FIG. 1 , a drill bit sharpener  20  is shown that is arranged to couple with, and be actuated by, an electric power tool (not shown), such as a corded or cordless electric drill. The drill bit sharpener  20  includes an input shaft  22  that is sized to be received in a standard electrical drill chuck (not shown). An opposite end of the shaft  22  is coupled to a first planetary hub  24  having a plurality of first planet gears  26 . In the exemplary embodiment, the first planetary hub  24  has three first planet gears  26 . The first planet gears  26  rotate within a ring gear  28 . The first planetary hub  24 , first planet gears  26  and ring gear  28  define a first gear train  29   
     The first planet gears  26  are retained on the first planetary hub  24  by retaining collars  30 . The first planet gears  26  rotate a sun gear  32  that is coupled to a second planetary hub  34 . The second planetary hub  34  has a plurality of second planet gears  36 . In the exemplary embodiment, the sharpener  20  has three second planet gears  36  which are retained on the second planetary hub  34  by collars  38 . The second planet gears  36  rotate within a second sun gear  40 . The second planetary hub  34 , second planet gears  36  and second sun gear  40  define a second gear train  46 . The second sun gear  47  is connected to a grinding stone  42  that is used to grind a desired profile onto the drill bit. The grind stone  42  may include a conical recess  44  ( FIG. 2 ) that is sized to receive the end of the drill bit. The angle of the conical recess  44  will depend on the point angle of the drill bit being sharpened. In some embodiments, the grind stone  42  is removably coupled to the second sun gear  47  to allow different drill bits to be sharpened. In the exemplary embodiment, the angle of the conical recess  44  may be between 60 to 135 degrees. 
     The second planet gears  36  rotate a second sun gear  47 . The second sun gear  47  is connected to the grinding stone  42  by a shaft  49 . In the exemplary embodiment, each of the gear trains  29 ,  46  develop a gear ratio of 18:1. This results in a total speed increase of 36 times the input power tool speed. 
     The gear trains  29 ,  46  are mounted within a case  48  by a plurality of bearing supports  50 ,  52 ,  54 . Each of the bearing supports  50 ,  52 ,  54  may have a bearing, such as a ball-bearing  61 . The case  48  has a first end  51  having an opening  53 . The opening  53  is sized to allow the shaft  22  to exit the case  48 . On a second end  55 , the case  48  has a second opening  57  sized to receive a slip collar  66 . In one embodiment, the case  48  has a generally hollow interior area  56  defined by an inner wall  58 . A plurality of circumferential grooves  60 ,  62 ,  64  may be formed on the inner wall  58 . The grooves  60 ,  62 ,  64  are sized to receive and retain the bearing supports  50 ,  52 ,  54  within the interior area  56 . 
     The grinding stone  42  is arranged between a slip collar  66  and bearing support  54 . A biasing member, such as spring  68  for example, biases the grinding stone  42  against a drill bit that is held in a drill chuck  70 . As is known to those skilled in the art, a drill chuck is a type of clamp used to hold an object with radial symmetry. In the exemplary embodiment, the drill chuck  70  has a plurality of jaws  71  that are arranged in a radially symmetrical pattern to hold the drill bit in place. In some embodiment, the drill chuck  70  may have a keyed or keyless jaw assembly that allows the jaws  71  to be opened or closed for removing and installing the drill bit. 
     In the exemplary embodiment, the slip collar  66  includes a bore  72  and a counter bore  74 . The bores  72 ,  74  are substantially axially aligned with the conical recess  44 . The counter bore  74  is sized to receive at least a portion of the grinding stone  42 . The slip collar  66  may also include a flange  76  that engages the inner wall  58  of the case  48  to allow the slip collar to be axially aligned within the case  48 . The slip collar  66  allows the drill chuck  70  to translate in a direction parallel to the drill bit. This arrangement provides advantages in improving the alignment between the drill bit and the grinding stone  42 . 
     In operation, the operator couples the shaft  22  to an electrical power tool, such as an electric drill, for example. The drill bit is then inserted into the drill chuck  70 , causing the end of the drill bit to contact the grinding stone  42 . The jaws  71  of the drill chuck  70  are tightened to hold the drill bit in the sharpener  20 . The operator actuates the electrical power tool causing the shaft  22  to rotate. The rotation of the shaft  22  is translated through the gear trains  29 ,  46  causing the grinding stone  42  to rotate against the end of the drill bit held in the drill chuck  70 . The rotation of the grinding stone  42  sharpens the drill bit. 
     It should be appreciated that while embodiments herein discuss using the sharpener with an electrical drill, this is for exemplary purposes and the claimed invention should not be so limited. The claimed sharpener may be used with any electrical power tool having a rotating element that the shaft of the sharpener may be attached, such as but not limited to a router, a rotary tool, a cordless drill, a corded drill, or a drill press for example. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.