Abstract:
A chuck for use with power tools to interchangeably accept and hold tools, such as wood or other cutting tools, especially router bits, of simple, lightweight design, improving manufacturing and assembly techniques, providing significant tool holding torque are disclosed. A method for connecting chucks, shafts and similarly threaded surfaces is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Serial No. 60/107,966, filed Nov. 12, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Chucks for use with power tools to interchangeably accept and hold tools, such as wood or other cutting tools, especially router bits, of simple, lightweight design, improving manufacturing and assembly techniques, but providing significant tool holding torque, are disclosed. 
     2. Discussion of the Related Art 
     Power tools to drive cutting, boring, and other tool elements are well known. 
     U.S. Pat. No. 5,096,212 to Joseph P. Walsh (the entire disclosure of which is herein incorporated by reference in its entirety) provided a significant advance in chucks suitable for use in coupling a power driven shaft to such tools, especially router bits. Such a chuck (illustrated in FIG. 1 (PRIOR ART)) comprised a chuck body  11 , provided with an aperture  114  into which a collet  115  can be inserted. 
     The other end of aperture  114  was provided with means, such as internal threads  120  (FIG. 2 (PRIOR ART)) for attachment to an electrically, pneumatically, hydraulically or other driven shaft. A collet  115  is insertable into aperture  114  and the shank  100  of cutting element  101  were secured in aperture  114  through the provision of a clamping mechanism extending through a bore  116  extending through aperture  114 . The clamping mechanism comprised two clamping elements  108 ,  109  pulled together by means of a screw  110 . At least clamping element  108  was threaded  90  to accept the threads  94  of screw  110  such that upon tightening the threads, screw head  96  clamped elements  108 ,  109  about collet  115  (or alternatively directly on the shaft  100  of cutting element  101 ) to securely couple the cutting element  101  and the power driven shaft of the power tool. 
     Although a great advance over the prior art chucks, the Walsh invention had several drawbacks. 
     The provision of bore  116  to accommodate two clamping elements extending through aperture  114  made the size of the chuck body relatively large and bulky to accommodate the clamping elements. Still further, clamp elements  108 ,  109  had to have alignment elements, such as keys and keyways  108 ′,  109 ′ to retain them in a desired orientation with regard to collet  115 , or shank  100 , of cutting element  101 . 
     The large size of the chuck exacerbated balancing as such chucks were used in routers known to revolve at speeds above 20,000 rpm (revolutions per minute). 
     Runout of the cutting element  101  became a problem as it was impossible to use threads  120  to simultaneously couple the chuck body  112  to the power driven shaft (not shown) while attempting to also align the respective centerline of the shank  100  and power driven shaft (not shown). 
     Another attempt at providing a chuck for a cutting tool is found in U.S. Pat. No. 5,348,319. In the device of that patent, a cam was provided which was pivotably mounted and activated by a set screw. However, the lever end of the cam, in conjunction with the set screw, could not generate sufficiently high holding power to withstand the forces tending to dislodge a cutting tool, especially a cutting tool rotating at high speed, such as in a router. To increase the length of the lever end of the cam would require enlarging the size of the chuck to accommodate the increased length, further tending to create a large and bulky mass, which, when subjected to high rotational speeds, would introduce additional problems which negates the proposed utility of the device as a chuck. 
     None of the attempts known to the inventor have been able to improve the requirements of a chuck for holding cutting, boring or other tools, and, especially, no one skilled in the art has provided an easy to use router chuck having acceptable torque for holding a cutting element without slippage while permitting ease of construction of the chuck. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve the Walsh chuck to reduce the large and bulky nature of the chuck body while retaining the excellent collet (or shank) holding properties thereof. 
     It is a further object of the invention to provide a new manner in which the chuck body of the invention can be secured to a driven shaft of a power tool in which alignment of the centerlines of the drive shaft and cutting element remain in alignment while simultaneously providing secure retention of the chuck body to the drive shaft. 
     It is a still further object of the invention to provide a collet or shank clamping element positioned at or nearly tangentially to a collet or shank receiving bore in the chuck body which does not require keys (or keyways) to align the clamping element relative to the collet or shaft to be clamped. 
     It is another object of the invention to provide a chuck of such weight, size and bulk as not to exacerbate balancing even when rotating at speeds in excess of 20,000 rpm. 
     It is a still further object to provide a method of aligning and coupling two elements, e.g., shafts, a chuck and a shaft, and other similar elements by the use of an novel centering and retaining element. 
    
    
     These and other objects of the invention will be apparent when read in light of the accompanying description of the preferred embodiments and appended drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 (PRIOR ART) is a schematic exploded view of the invention of Joseph P. Walsh as described in U.S. Pat. No. 5,096,212; 
     FIG. 2 (PRIOR ART) is a side view of a partially assembled chuck and conventional router bit with the collet of FIG. 1; 
     FIG. 3 is an exploded, schematic view of the chuck of the present invention; 
     FIG. 4 is a side view of the chuck of the present invention; and 
     FIG. 5 is an enlarged front view of the chuck body of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 3 is shown a chuck body  212  with an aperture  214  therein to accept a collet or shank of a cutting tool (not shown but similar to collet  115  and shank  100  of FIG.  1 ). Chuck body  212  defining the entrance of aperture  214  is optionally milled or chamfered at  210 . For aesthetics, the outer periphery of chuck body  212  may also be optionally chamfered or surface ground as at  208 . 
     The rear of chuck body  212  is provided with a cone-shaped extension  213  of chuck body  212  having an helical groove  215  therein. As the helical groove descends the cone-shaped extension  213  toward chuck body  212 , it intersects a circumferentially extending groove  216 . 
     A collet nut  217  is captured by a single, or a series, of coiled spring washers (or spiral locks)  218 ,  219 , etc. (a single, or series, of spiral locks, one to five being preferred), two being most preferred, which are threaded down the helical groove  215  until they are seated within groove  216  and restraining flange  250  thereby preventing relative axial movement of the collet nut  217  and chuck body  212 . Collet nut  217  is thus free to rotate about the cone shaped extension  213  but is prevented from axial movement related thereto by the series of coiled spring washers,  218 ,  219  etc. within groove  216 . 
     The cone-shaped extension has a shape such that at least a part of its outer surface is complimentary to a recess bored into the end of an element to which it is to be connected, e.g., to a shaft as a power driven shaft (not shown) of the power tool (not shown). The cone-shaped extension  213  and recess bored into the power drive shaft align the respective centerlines of aperture  214  and power driven shaft both axially and radially. 
     The collet nut  217  retains chuck body  212  to the power driven shaft by means of threads  221  on the interior of collect nut  217 , which mate with external threads on the power driven shaft but acts only as a securing means and does not act in aligning the chuck body aperture  214  to the power driven shaft. As an alternative to threads, other fastening means, such as a bayonet coupling, may be used. 
     As shown in FIG. 3, chuck body  212  is also provided with an aperture  222  tangential thereto to accept a clamping element  209 . Clamping element  209  is unthreaded and is bored through off center such that it does not rotate within aperture  222  upon tightening of a screw  294  with threads  223 . Although aperture  222  to receive clamping element  209  intersects aperture  214 , such intersection to aperture  214  does not extend for its full cross-section completely across aperture  214  as in the Walsh chuck. Rather, as shown in greater detail in FIG. 5, clamping element  209  defines an angle of intersection with the aperture  214  which clamping element intersects the circumference of the aperture  214  and contacts (when inserted into aperture  214 ) the outer periphery of a cutting tool shaft, the exterior of a collet placed within aperture  214 , etc. The angle ∝ may vary but is measured along a diameter of aperture  214  normal to the longitudinal axis of screw  294 . The area of contact defined by angle ∝ by clamping element  209  determines the degree of clamping force. I have found that clamping from about tangent to not more than 45°, preferably about 40°, provides the greatest holding power upon the shaft of a bit or upon the exterior of a collet placed within aperture  214 . In a particularly preferred embodiment, as shown in FIG. 5, the clamping element can be displaced a few degrees shy of tangent and still develop substantial torque upon the element placed within aperture  214 . The remainder of the aperture is of smaller cross section and is suitable internally threaded to receive the threads of a screw  294 . 
     The single clamping element  209  is of generally cylindrical configuration but could have other external configurations as desired. The generally cylindrical configuration is most preferred however insofar as it is easiest to form a circular cross-sectioned aperture  222  in chuck body  212  as opposed to an aperture of any other non-circular cross-sectional shape. 
     Clamping element  209  has an offset unthreaded bore therein which permits a threaded screw or other fastening element to pass therethough. The headed end  296  of screw  294  forces clamping element  209  into aperture  222  to engage with a collet (similar to collet  115  of FIG. 1) or shank of a cutting tool (similar to shank  100  of cutting element  101  of FIG. 1) to secure the same within aperture  214 . Clamping element  209  is suitably shaped such that the end distal from the end adjacent the headed end  296  of screw  294  is milled to conform the distal end with the collet or shank of the cutting tool so as to exert the greatest clamping force on an inserted collet or shank of a cutting tool (not shown) inserted into aperture  214 . Such milling can also include a chamfering of said distal end to facilitate insertion of the collet or shank. Upon rotation of screw  294  engaging threads  295  thereby forcing clamping element  209  into aperture  214 , the milled end of clamping element places a large force on either collet or shank of cutting tool inserted into aperture  214  to secure the same within the aperture. Both axial and tangential forces on the cutting tool will be resisted by means of the structural interrelationship of elements constituting the clamping mechanism. 
     Headed end  296  is shaped so as to receive any conventional tool (not shown) such as a hex socket to receive a T-handle Allen wrench (not shown) to rotate the screw to impart, or relieve, the clamping force. Because the clamping element  209  is at or nearly tangential to aperture  214 , a great mechanical advantage is achieved and the size of the clamping element necessary to achieve the same clamping effect as in the Walsh chuck can be reduced. Such reduction in size permits an overall reduction in the size (and hence weight and bulk) of the chuck body  212 . 
     The chuck body  212  (and related elements) may be made of the same or similar materials as the Walsh chuck, for example, a carbon steel (e.g., a low, medium, or a high carbon steel) or other metal such as tool steels, alloy steels, stainless steels, etc. 
     They may be finished by various surface treatments known to the art such as oxiding to darken or lighten the color of its exterior surfaces, thermally treated to alter its hardness and other treatments generally known to those in the machine tool art. 
     It is to be understood that although I have discussed the use of a collet to receive the shank of a cutting tool, it will be understood by those skilled in the art that a series of collets can be used with the chuck to accept various shanks of different sizes. It will also be understood that the shank of a cutting tool approximately the size of aperture  214  may be inserted directly into the aperture  214  without a collet, the collet(s) being used to adapt smaller sized shanks to the aperture  214 . 
     In another embodiment of the invention, I have provided a method whereby elements, such as shafts, a chuck and a shaft, etc. can be aligned and coupled with great mechanical precision. 
     In such a method, an end of a shaft (not shown) may be milled into a cone shape having a groove at the base of the cone similar to the shapes  213  and  216  of FIG. 4, respectively. A spiral groove, similar to groove  215  of FIG. 4 can be provided on the surface of the cone shape. A nut or other fastener similar to nut  217  (FIG. 3) having internal threads is then placed over the cone and surrounding the groove at the base of the cone. A series of spiral locks (preferable at least two) are manipulated over the spiral groove so as to lock the nut or other fastener to the shaft to prevent longitudinal separation of the same. 
     A shaft, chuck or other element may be interiorly milled with a shape corresponding, at least in part, to the cone shape so as to receive the same. The exterior surface of the shaft, chuck, etc. can be provided with threads matching the interior threads of the nut or other fastener and, upon engaging the respective threads, the cone will be drawn into and aligned with the complimentary surface of the shaft, chuck, etc. and further tightening will couple the elements. This method has been found to satisfactorily align the centerlines of the elements consistently to within tolerances of a few thousands of an inch. 
     Having described my invention, it will be apparent to those of ordinary skill in the art that modifications may be made thereto without departing from the spirit or scope of the invention.