Abstract:
An improved quick change power tool chuck is provided which is principally used on a wood working router but could also be used in many other power tool applications. The key features of the quick change chuck are the unique way that it secures the cutting bit from unwanted slippage, the large mechanical advantage thereof and the speed in which a cutting bit can be removed and replaced. The chuck can be aligned and attached to the power tool in the same manner that a standard collet is aligned and attached to the router spindle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims benefit of the filing date of Provisional Patent Application No. 60/432,638, filed on Dec. 12, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to quick change chucks for power tools and, more particularly, to an improved chuck that provides increased holding force without sacrificing ease of bit changing. 
   2. Discussion of Related Art 
   Although there are a number of existing chucks and like devices for retaining cutting bits in power tools and driven spindles, they all have some disadvantages which detract from their advantages. For example, while some chucks hold the cutting bit with enough force that slippage will not occur, the changing of the bit can be very cumbersome and time consuming. Others allow an easy changing of bits but do not provide enough holding torque to prevent slippage from occurring. There are a few chucks that allow easy changing of bits and also provide a reasonable amount of holding torque. However, at the present time, there are no chucks currently available which allow an easy change of the cutting bit and which also provide the increase in mechanical advantage necessary to enable a large enough force to be exerted on the cutting bit so as to substantially increase the holding torque. A chuck of this type would allow the power tool user to spin much larger cutting bits at higher speeds while still maintaining a substantially greater safety margin because of the increased holding force. 
   One chuck of particular interest here is that disclosed in U.S. Pat. No. 5,096,212 to Walsh. Although this chuck has advantages, there are several disadvantages to the chuck. By way of background, it is noted that routers are required to spin the cutting bit at a relatively high angular speed, typically above 20,000 rpms. Thus, the design of a router chuck has to be as lightweight and compact as possible for obvious reasons. Accordingly, if the chuck is relatively heavy and bulky in size as in the case of the chuck of the Walsh patent, unwanted and sometimes severe vibration can occur, resulting in an unsafe operating condition. Further, the chuck of the Walsh patent requires two cams which secure the tool essentially by pinching the tool shank. Since the cams are harder than the typical tool shank, an unwanted indentation in the tool shank can result if the cams are over-tightened. Another disadvantage of the Walsh chuck is that the manner in which the nut is attached to the body is inadequate. In this regard, although during the short time a chuck constructed as disclosed in the Walsh patent was distributed no failures were reported, the construction could have eventually led to catastrophic failure. Finally, the construction of the chuck of the Walsh patent employs some unnecessary parts, includes a relatively weak screw, and, in general, has the appearance of being cumbersome and awkward to use. 
   An improvement in the construction of quick change router chucks and the like is disclosed in U.S. Pat. No. 6,332,619 B1 to DeRosa. The genesis of this construction was an attempt to overcome all, or as many as possible, of the shortcomings of the Walsh chuck. The attempt was successful and the construction of the DeRosa chuck not only incorporates several improvements but has been manufactured and sold in quantity to the general public. One improvement is the use of only a single cam instead of two. The single cam was also modified and is allowed to slightly crush under pressure. However, while the cam maintains its holding power, it does not indent the tool shank. The nut is attached by the use of retaining rings which are much stronger and safer than the previously used pins. Among other advantages, the size of the chuck was greatly reduced by the elimination of one cam and a few unnecessary internal parts, and a stronger screw was incorporated. However, one disadvantage is that some of the holding power provided by the chuck had to be sacrificed by the use of the softer cam in eliminating the tool shank indentation problem created by the previous use of a harder cam. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a chuck having greatly increased holding torque, without relying on set screws, flats, keys or any other such elements or configurations that are conventionally used to prevent angular slippage between the cutting bit and the chuck. 
   A further object of the present invention is to preserve the relative ease of bit changing and mounting to the motor tool or spindle that is characteristic of quick change chucks. 
   Another object of the present invention is to allow the spinning of much larger cutting bits more safely, by providing much stronger holding of the bit. 
   A further object of the present invention is to greatly improve the holding strength to weight ratio of the chuck in comparison to other existing quick change chucks. 
   An additional object of the present invention is to eliminate any internal parts that can wear out or fail over time but yet are critical to the operation of the chuck, such as cams, plates, and the like found in prior art chucks. 
   In accordance with one aspect of the invention, there is provided a chuck device for holding a tool having a tool shaft or a connecting collet, wherein the device comprises: a chuck body including a central longitudinally extending bore therein of a predetermined circumferential shape for receiving the shaft or collet of the tool, and a pivotable portion movable between a rest position wherein the predetermined circumferential shape of the bore is maintained and there is no engagement between the pivotable portion and the shaft or collet of a tool received in the bore, and an operative position wherein a bore-facing surface of said pivotable portion extends inwardly into said bore so as to engage the shaft or collet of a tool received in said bore; and a fastener member, received in an aperture in said chuck body, for, in use, causing pivoting of said pivotable portion of said chuck body to a said operative position thereof so that the bore-facing surface of said pivotable portion engages the shaft or collet of a tool received in said bore. 
   Preferably, in the operative position of the pivotable member, the bore-facing surface of the pivotable member engages at least substantially one-half of the outer circumferential surface of the shank or collet. 
   In a preferred implementation, the pivoting portion of the chuck device is formed integrally with the chuck body. The chuck body preferably includes an annular portion including first and second orthogonal slots therein which divide said annular portion into said pivotable portion and a fixed portion. The first slot preferably extends inwardly from an end surface of the annular portion parallel to the longitudinal axis of the bore. Advantageously, the annular portion includes a circumferential surface defining the longitudinal thickness of the annular portion and first and second opposed end surfaces spaced apart by said thickness, the first slot extends into said first end surface of said annular portion for a distance greater than one half of said thickness and terminates short of said second end surface, and the second slot extends into said annular portion orthogonally to said first slot from said circumferential surface so as to terminate in said annular portion along a line a portion of which is substantially coextensive with the first slot. 
   Preferably, the aperture in which the fastener is received extends orthogonally to said bore. Advantageously, the aperture includes a threaded section and the fastener element comprises a cap screw including a threaded portion for engaging the threaded section of the aperture. Further, a washer is advantageously disposed on the threaded portion of the cap screw. 
   In a further important implementation, the chuck body comprises a main body portion, and the pivotable portion comprises a pivot arm which is formed separately from the main body portion and is pivotably mounted thereon. Advantageously, the arm is of a substantially U-shaped configuration having a first, pivoted end and a second, free end and defining said bore-facing surface between said first and second ends. Preferably, the fastener element, in use, engages the free end of said arm to clamp said bore-facing surface of the arm against the shank or collet of a tool received in the chuck bore. Advantageously, the free end of said arm includes a threaded opening therein, and the fastener element comprises a cap screw including a threaded portion adapted to be screwed into the threaded opening in the free end of the arm. 
   Preferably, the chuck device further comprises a cover for the chuck body, the cover comprising a flat end wall and an annular side wall and including an opening in said end wall adapted to be aligned with said central bore in the chuck body and an aperture in said side wall adapted to be aligned with said aperture in the chuck body. Advantageously, the chuck device further comprises an alignment pin, and the cover and chuck body include respective recesses in which opposite ends of the alignment pin are received so as to provide alignment of the cover and chuck body. Preferably, the side wall of the cover has an inner surface including a circumferential slot therein, and the chuck device further includes a locking ring adapted to be received in said slot so as to lock said cover on the chuck body. 
   Preferably, the chuck body further includes a tapered portion through which said bore extends, and the chuck device further comprises a nut adapted to be affixed to the tapered portion. Advantageously, the nut includes a side wall having internal screw threading and including a circumferential slot, the tapered portion of said chuck body includes a circumferential slot in an outer surface thereof, and the chuck device further includes at least one locking ring adapted to be received in the slots in said nut and said tapered portion of said main body so as to provide locking of said nut on said chuck body. 
   According to a related aspect of the invention, there is provided a chuck device for holding a tool having a tool shaft or a connecting collet, the device comprising: a chuck body including a central longitudinally extending bore therein of a predetermined circumferential shape for receiving the shaft or collet of the tool, and comprising a fixed portion and a deformable portion including one end connected to, and formed integrally with, said fixed portion, said deformable portion being movable between a rest position wherein the predetermined circumferential shape of the bore is maintained and there is no engagement between the deformable portion and the shaft or collet of a tool received in the bore, and an operative position wherein a bore-facing surface of said deformable portion extends inwardly into said bore so as to engage the shaft or collet of a tool received in said bore; and a fastener member, received in an aperture in said chuck body, for, in use, causing movement of said deformable portion of said chuck body to a said operative position thereof so that the bore-facing surface of said deformable portion engages the shaft or collet of a tool received in said bore. 
   As above, in the operative position of the deformable portion, the bore-facing surface of the deformable portion preferably engages at least substantially one-half of the outer circumferential surface of the shank or collet. 
   Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a preferred embodiment of the chuck assembly of the present invention; 
       FIG. 2  is a side elevational view, partially in section, of the assembly of  FIG. 1 ; 
     FIGS.  3 ( a ) and  3 ( b ) are an exploded end elevational view and side elevational view, respectively, of the main body of  FIG. 1  showing the slits in the main body that allow the clamping of the tool bit; and 
       FIG. 4  is an end elevational view of the main body in accordance with an alternative embodiment for clamping of the tool bit. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an exploded perspective view of a preferred embodiment of the chuck device of the invention while  FIGS. 2 ,  3 ( a ) and  3 ( b ) show various features of this embodiment. The chuck device is composed of nine parts as shown in  FIG. 1 , viz., a safety cover  300 , a main body  301 , a pin  310 , a washer  311 , a cap screw  312 , a lock ring  314 , a nut  315 , and two further lock rings  316  and  317 . 
   In accordance with a key feature of the invention, the main body  301  is adapted to be mechanically deformed by the incorporation thereof of two slots  323  and  324  that extend perpendicular to each other. These slots are perhaps best seen in FIG.  3 ( b ) and, as shown, divide an annular end portion of main body  301  into a fixed part or side  301   a  and a movable part or side  301   b . As illustrated in FIG.  3 ( a ), slot  323  extends inwardly from the circumferentially extending side surface of main body  301  so as to terminate in the main body  301  along a line (indicated by the dashed line  323 ) a portion of which is coextensive with orthogonal slot  324 . Slots  323  and  324  thus create a movable or pivotable portion  301   b  of main body  301  which is capable of pivotable movement or flexing about the base portion thereof if sufficient force is applied thereto. Thus, when the cap screw  312  is tightened against the fixed side  301   a  of the cam body  301 , the opposite side  301   b  of the body  301  defined by the slots  323  and  324  can flex and translate. Main body  301  includes a central aperture  303 , and the inward translation of pivotable part  301   b  causes a slight inward distortion of the central aperture  303 , as is indicated in dashed lines in FIG.  3 ( a ). This enables a large clamping force to be applied to a tool shank or collet (not shown) which has been inserted into the main aperture  303  of the device. 
   Considering this clamping operation in more detail, the main body  301  also includes a further aperture  305 , which extends perpendicular to central aperture  303 . As indicated above, aperture  303  allows placement of the tool shank (not shown) into the slightly deformable main body  301 , whereas aperture  305  allows insertion therein of the cap screw  312 , through the washer  311 . Cap screw  312  includes a threaded portion  312   a  adapted to engage to threads  306  of aperture  304 . When the threaded portion  312   a  of cap screw  312  is tightened onto threads  306 , cap screw  312  pulls the deformable part  301   b  of the body  301  against the tool shank or collet (not shown) thereby exerting a large force circumferentially on the tool shank or collet. A large mechanical advantage is obtained by applying the force tangentially to the deformable body  301  with cap screw  312 . The arrangement of deformable part  301   b  is such that the inner, bore-facing surface of deformable portion  301   b  engages substantially one-half of the outer surface of the shank or collet and the main body  301  forms almost a complete “noose” around the tool shank so that the tool is held almost completely around the circumference of the tool shank. It will be understood that although in this embodiment the bore-facing surface of deformable portion  301   b  engages substantially one-half of the outer surface of the shank or collet, a lesser portion of the shank or collect can be engaged and still provide the noose effect. 
   It will be appreciated from the foregoing that disengagement of the tool shank is readily achieved. In this regard, when cap screw  312  is loosened, the deformable part  301   b  of body  301  springs back to its relaxed or rest position, thereby freeing the tool shank to be removed. 
   As best seen in  FIG. 2 , the pin  310  is used to align the safety cover  300  which covers the main deformable body  301  with the body  301  itself and, to this end, opposite ends of pin  310  are received in respective apertures in cover  300  and main body  301 . Cover  300  also contains a central aperture  302  which allows the tool shank to be inserted into aperture  303 . Pin  310  also allows aperture  305  and a further aperture  320  (see  FIG. 2 ) provided in the side wall of cover  300  to be aligned so that the cap screw  312  and the washer  311  can be inserted into aperture  305  and engaged with threads  306 . 
   After the safety cover  300  has been placed in position over the deformable main body  301 , the locking ring or lock ring  314  is inserted into the bottom of safety cover  300  and into a groove  325  (see  FIG. 2 ) which is formed in the inner circumference of cover  300  so that ring  314  and groove  325  function as a permanent retention device. 
   The alignment of the main tool aperture  303  with respect to the driven tool spindle (not shown) is accomplished in the usual, standard manner by the use of a taper section  318  formed on the body  301 . The constructional details of the tapered section  318  will change according to the requirements of the particular geometrical configuration of the driven tool spindle. For example, parameters such as the taper angle, diameter, and length will be made to match the configuration of the driven tool spindle. 
   Turning to nut  315 , and the manner of connection thereof, to main body  301 , the aforementioned locking rings or lock rings  316  and  317  are inserted into the nut  315 . More particularly, the lock rings  316  and  317  are placed into an internal retaining groove  322  located inside of the nut  315 . The tapered section or portion  318  of the main body  301  is pushed into a central aperture  321  in nut  315  as shown in  FIG. 2 , thus allowing the locking rings  316  and  317  to expand and snap into a circumferential groove  319  in tapered portion  318 , thereby permanently attaching the nut  315  to the main body  301 . 
   After the placement of the nut  315  is completed, the locking ring  314  becomes totally inaccessible and disassembly of the chuck becomes impossible unless the chuck is destroyed or otherwise rendered inoperable. This is a safety feature that eliminates unwanted tampering with the chuck device. 
   Finally, the chuck device is inserted into the driven tool spindle (not shown) and retained thereon by the use of threads  304  located on the inside circumferential surface of the nut  315 . The nut  315  is then tightened onto the driven tool spindle thereby pulling the tapered section  318  of the main body  301  against the matching spindle taper, thereby securing the chuck device to the spindle. After the chuck device has been installed onto the router or other spindle, the chuck device is ready to accept cutting tools and is otherwise ready for use. 
   Referring to  FIG. 4 , an alternative embodiment of the invention is shown. This embodiment is similar to that of FIG.  1  and the description here will basically focus on the differences between this embodiment and that of FIG.  1 . In  FIG. 4 , a main body  401  includes a conventional central bore  402 , and also includes a milled cavity  403  which receives a rotating or pivoting arm  404 . 
   Arm  404  pivots around a pin  405  secured to main body  401  within cavity  403 . Arm  404  is of a generally U-shaped construction, as illustrated, so that the inner curved surface thereof can engage the tool shank (not shown) received in bore  402 . The free end of arm  404  is engaged by a threaded portion or section  406   a  of a cap screw  406  which is received, with a suitable clearance, in a bore  407  in main body  401 . Cap screw  406  is thus used to control tightening and loosening of the engagement between the inner surface of arm  404  and the tool shank or collet (not shown). 
   It is noted that in both embodiments described above the cap screw ( 312  or  406 ) screws into the movable or pivotable portion from the fixed portion but it will be understood that the cap screw (or other tightening element) can also screw into the fixed portion from the pivotable portion. 
   Although the invention has been described above in relation to preferred embodiments thereof, it will be understood by those skilled in the art that variations and modifications can be effected in these preferred embodiments without departing from the scope and spirit of the invention.