Abstract:
A surgical device comprising: a handle assembly; a locking collar; and a set of replaceable bits that load along an axis into the handle assembly; wherein the locking collar is fully removable from the handle assembly, the locking collar loads axially to a first position, and the locking collar rotates between the first position and a second position; wherein, in the first position, the locking collar is free to be axially removed from the handle assembly and the replaceable bits are free to be loaded or unloaded from the handle assembly; wherein, in the second position, the locking collar is prevented from axial movement relative to the handle assembly and the replaceable bits are prevented from being received within, or removed from, the handle assembly; and the locking collar is guided to the first position and between the first position and the second position by a groove in the handle assembly mating with a member carried by the locking collar. And a surgical device comprising: a handle assembly comprising a rotatable drive shaft; a removable handle assembly adapter for connection to the handle assembly, the removable handle assembly adapter comprising a rotatable transmission shaft for connection to the rotatable drive shaft of the handle assembly; and a removable nosepiece assembly for connection to the removable handle assembly adapter and for selectively securing the shaft of a working element to the rotatable transmission shaft of the removable handle assembly adapter; wherein the removable handle assembly adapter and the removable nosepiece assembly each comprise a locking collar; and wherein the removable handle assembly adapter and the handle assembly each comprise a connector assembly, the connector assembly comprising: a housing comprising an opening; a collet sleeve disposed within the opening and connected to an input shaft, the collet sleeve comprising a lumen for receiving an output shaft; a locking element movable relative to the collet sleeve between (i) a locked position in which the output shaft is secured to the collet sleeve, and (ii) an unlocked position in which the output shaft is not secured to the collet sleeve; and a cam element movable relative to the collet sleeve between (i) a first position in which the locking element is free to assume its unlocked position, and (ii) a second position in which the cam element cams the locking element into the locked position; such that movement of the locking collar causes the cam element to move between the first position and the second position.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/986,607, filed Apr. 30, 2014 by Gyrus ACMI, Inc. (d.b.a. Olympus Surgical Technologies America) and Kevin C. Edwards et al. for ROTARY TOOL WITH IMPROVED COUPLING (Attorney&#39;s Docket No. OLYMPUS-0405 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to surgical apparatus and procedures in general, and more particularly to rotary tools of the sort used to drive working elements such as drill bits and burrs. 
       BACKGROUND OF THE INVENTION 
       [0003]    In many surgical procedures, it is necessary or desirable to drill or abrade an object, e.g., bone. In these situations, it is common to provide a rotary tool comprising a handle assembly having a high speed motor, and a coupling assembly at the distal end of the handle assembly for releasably connecting a working element (e.g., a drill bit or burr) to the high speed motor, such that the working element (e.g., the drill bit or burr) can be turned by the high speed motor and then used for the desired purpose (e.g., drilling or abrading bone). 
         [0004]    The present invention provides a novel coupling assembly for releasably connecting a working element (e.g., a drill bit or burr) to a high speed motor of a handle assembly of a rotary tool. 
         [0005]    For purposes of clarity of description, the present invention will sometimes hereinafter be discussed in the context of a high speed drill bit or burr, however, it should be appreciated that the present invention is also applicable to other working elements, e.g., a dental polishing head, etc. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention comprises the provision and use of a novel coupling assembly for releasably connecting a working element (e.g., a drill bit or burr) to a high speed motor of a handle assembly of a rotary tool. 
         [0007]    For purposes of clarity of description, the present invention will sometimes hereinafter be discussed in the context of a high speed drill bit or burr, however, it should be appreciated that the present invention is also applicable to other working elements, e.g., a dental polishing head, etc. 
         [0008]    In one preferred form of the invention, there is provided a surgical device comprising: 
         [0009]    a handle assembly; 
         [0010]    a locking collar; and a set of replaceable bits that load along an axis into said handle assembly; 
         [0011]    wherein said locking collar is fully removable from said handle assembly, said locking collar loads axially to a first position, and said locking collar rotates between said first position and a second position; 
         [0012]    wherein, in said first position, said locking collar is free to be axially removed from said handle assembly and said replaceable bits are free to be loaded or unloaded from said handle assembly; 
         [0013]    wherein, in said second position, said locking collar is prevented from axial movement relative to said handle assembly and said replaceable bits are prevented from being received within, or removed from, said handle assembly; and 
         [0014]    said locking collar is guided to said first position and between said first position and said second position by a groove in said handle assembly mating with a member carried by said locking collar. 
         [0015]    In another preferred form of the invention, there is provided a surgical device comprising: 
         [0016]    a handle assembly, said handle assembly comprising:
       a collet sleeve, said collet sleeve comprising at least one opening extending radially through said collet sleeve;   a hollow housing;   at least one canted cam slot formed in said hollow housing, said at least one canted cam slot having a first end and a second end;   a biasing collar, said biasing collar comprising at least one biasing collar engagement element, said at least one biasing collar engagement element extending through said at least one canted cam slot and extending outwardly from the outer surface of said hollow housing, said biasing collar being configured to move between a first biasing collar position and a second biasing collar position;   a cam element, said cam element being configured to move between a first cam element position and a second cam element position;   a biasing element, said biasing element biasing said cam element towards said second cam element position; and   at least one locking element, said at least one locking element being configured to move in said at least one opening in said collet sleeve; and       
 
         [0024]    a locking collar, wherein said locking collar is fully removable from said handle assembly, and further wherein said locking collar is configured to directly engage the portion of said at least one biasing collar engagement element which extends outwardly from the outer surface of said hollow housing and is configured to rotate between a first locking collar position and a second locking collar position; 
         [0025]    wherein, when said locking collar is in its first locking collar position, said at least one biasing collar engagement element is engaged with said locking collar and is driven to said first end of said at least one canted cam slot, causing said biasing collar to be driven to said first biasing collar position, in which position said biasing collar urges said cam element to said first cam element position, and further wherein, with said cam element in said first cam element position, said at least one locking element is free to move radially outward in said at least one opening of said collet sleeve; and 
         [0026]    wherein rotation of said locking collar from said first locking collar position to said second locking collar position causes said at least one biasing collar engagement element to be driven to said second end of said at least one canted cam slot, and said biasing collar is driven to said second biasing collar position, such that said biasing collar is retracted beyond the travel of said cam element, allowing said biasing element to drive said cam element to its said second cam element position, in which position said at least one locking element is driven into said at least one opening in said collet sleeve so that a portion of said at least one locking element extends radially inward from the inner wall of said collet sleeve. 
         [0027]    In another preferred form of the invention, there is provided a method for securing a working element to a surgical device, said method comprising: 
         [0028]    providing a surgical device comprising:
       a handle assembly, said handle assembly comprising:
           a collet sleeve, said collet sleeve comprising at least one opening extending radially through said collet sleeve;   a hollow housing;   at least one canted cam slot formed in said hollow housing, said at least one canted cam slot having a first end and a second end;   a biasing collar, said biasing collar comprising at least one biasing collar engagement element, said at least one biasing collar engagement element extending through said at least one canted cam slot and extending outwardly from the outer surface of said hollow housing, said biasing collar being configured to move between a first biasing collar position and a second biasing collar position;   a cam element, said cam element being configured to move between a first cam element position and a second cam element position;   a biasing element, said biasing element biasing said cam element towards said second cam element position; and   at least one locking element, said at least one locking element being configured to move in said at least one opening in said collet sleeve; and   
           a locking collar, wherein said locking collar is fully removable from said handle assembly, and further wherein said locking collar is configured to directly engage the portion of said at least one biasing collar engagement element which extends outwardly from the outer surface of said hollow housing and is configured to rotate between a first locking collar position and a second locking collar position;   wherein, when said locking collar is in its first locking collar position, said at least one biasing collar engagement element is engaged with said locking collar and is driven to said first end of said at least one canted cam slot, causing said locking collar to be driven to said first locking collar position, in which position said locking collar urges said cam element to said first cam element position, and further wherein, with said cam element in said first cam element position, said at least one locking element is free to move radially outward in said at least one opening in said collet sleeve; and   wherein rotation of said locking collar from said first locking collar position to said second locking collar position causes said at least one biasing collar engagement element to be driven to said second end of said at least one canted cam slot, and said biasing collar is driven to said second biasing collar position, such that said biasing collar is retracted beyond the travel of said cam element, allowing said biasing element to drive said cam element to its said second cam element position, in which position said at least one locking element is driven into said at least one opening in said collet sleeve so that a portion of said at least one locking element extends radially inward from the inner wall of said collet sleeve;       
 
         [0040]    rotating said locking collar so as to cause said biasing collar to move said cam element into said first cam element position; 
         [0041]    positioning the shaft of a working element in said collet sleeve; and 
         [0042]    rotating said locking collar so as to cause said biasing collar to move so as to allow said cam element to assume its second cam element position. 
         [0043]    In another preferred form of the invention, there is provided a surgical device comprising: 
         [0044]    a handle assembly comprising a rotatable drive shaft; 
         [0045]    a removable handle assembly adapter for connection to said handle assembly, said removable handle assembly adapter comprising a rotatable transmission shaft for connection to said rotatable drive shaft of said handle assembly; and 
         [0046]    a removable nosepiece assembly for connection to said removable handle assembly adapter and for selectively securing the shaft of a working element to said rotatable transmission shaft of said removable handle assembly adapter; 
         [0047]    wherein said removable handle assembly adapter and said removable nosepiece assembly each comprise a locking collar; and 
         [0048]    wherein said removable handle assembly adapter and said handle assembly each comprise a connector assembly, said connector assembly comprising:
       a housing comprising an opening;   a collet sleeve disposed within said opening and connected to an input shaft, said collet sleeve comprising a lumen for receiving an output shaft;   a locking element movable relative to said collet sleeve between (i) a locked position in which said output shaft is secured to said collet sleeve, and (ii) an unlocked position in which said output shaft is not secured to said collet sleeve; and   a cam element movable relative to said collet sleeve between (i) a first position in which said locking element is free to assume its said unlocked position, and (ii) a second position in which said cam element cams said locking element into said locked position;       
 
         [0053]    such that movement of said locking collar causes said cam element to move between said first position and said second position. 
         [0054]    In another preferred form of the invention, there is provided a kit comprising: 
         [0055]    a handle assembly comprising a rotatable drive shaft; 
         [0056]    a removable nosepiece assembly; and 
         [0057]    a set of replaceable bits; 
         [0058]    wherein said removable nosepiece assembly is configured for mounting to said handle assembly and for accepting a replaceable bit so that said replaceable bit is connected to said rotatable drive shaft; and 
         [0059]    a removable handle assembly adapter having a rotatable shaft, said removable handle assembly adapter being configured at one end for mounting to said handle assembly and being configured at another end for receiving said nosepiece assembly so that said replaceable bit is connected to said rotatable drive shaft via said rotatable shaft of said removable handle assembly. 
         [0060]    In another preferred form of the invention, there is provided a surgical device comprising: 
         [0061]    a handle assembly comprising 
         [0000]    a powered drive shaft; and
 
a first connector assembly;
 
         [0062]    a removable nosepiece assembly for connection to said handle assembly, said removable nosepiece assembly comprising: 
         [0063]    a first shaft with a first shaft engagement portion for connection to said powered drive shaft of said handle assembly; 
         [0064]    a second shaft with a second shaft engagement portion for connection to the shaft of a working element; and 
         [0065]    a second connector assembly; 
         [0066]    wherein each of said first and second connector assemblies comprises:
       a housing comprising an opening;   a collet sleeve disposed within said opening and connected to an input shaft, said collet sleeve comprising a lumen for receiving an output shaft;   a locking element movable relative to said collet sleeve between (i) a locked position in which the output shaft is secured to said collet sleeve, and (ii) an unlocked position in which the output shaft is not secured to said collet sleeve;   a cam element movable relative to said collet sleeve between (i) a first position in which said locking element is free to assume its said unlocked position, and (ii) a second position in which said cam element cams said locking element into said locked position; and   a locking collar mounted to said housing such that rotation of said locking collar causes said cam element to move into said second position.       
 
         [0072]    In another preferred form of the invention, there is provided a surgical device comprising: 
         [0073]    a handle assembly comprising a rotatable drive shaft; 
         [0074]    a removable handle assembly adapter for connection to said handle assembly, said removable handle assembly adapter comprising a rotatable transmission shaft for connection to said rotatable drive shaft of said handle assembly; and 
         [0075]    a removable nosepiece assembly for connection to said removable handle assembly adapter and for selectively securing the shaft of a working element to said rotatable transmission shaft of said removable handle assembly adapter; 
         [0076]    wherein at least one of said removable handle assembly adapter and said removable nosepiece assembly comprises a removable locking collar; and 
         [0077]    wherein at least one of said removable handle assembly adapter and said handle assembly comprises a connector assembly, said connector assembly comprising:
       a housing comprising an opening and a canted slot;   a collet sleeve disposed within said opening and connected to an input shaft, said collet sleeve comprising a lumen for receiving an output shaft;   a locking element radially movable relative to said collet sleeve between (i) a locked position in which said output shaft is secured to said collet sleeve, and (ii) an unlocked position in which said output shaft is not secured to said collet sleeve;   a cam element longitudinally movable relative to said collet sleeve between (i) a first position in which said locking element is free to assume its said unlocked position, and (ii) a second position in which said cam element cams said locking element into said locked position, said cam element being yieldably biased into said second position;   a biasing collar for biasing said cam element into said first position; and   an element extending through said canted slot and secured to said biasing collar and said locking collar, such that rotation of said locking collar causes said element to move within said canted slot, whereby to cause said biasing collar to move said cam element between said second position and said first position.       
 
         [0084]    In another preferred form of the invention, there is provided a method for securing a replaceable bit to a handpiece surgical device, said method comprising: 
         [0085]    providing a surgical device comprising:
       a handpiece handle comprising a powered rotatable drive shaft;   a removable handpiece handle assembly adapter for connection to said handpiece handle assembly, said removable handpiece handle assembly adapter comprising a rotatable transmission shaft for connection to said powered rotatable drive shaft of said handpiece handle assembly; and   a removable coupling nosepiece assembly for connection to said removable handpiece handle assembly adapter and for selectively securing the shaft of a working element to said rotatable transmission shaft of said removable handpiece handle assembly adapter;   wherein at least one of said removable handle assembly adapter and said removable nosepiece assembly comprises a removable locking collar; and   wherein at least one of said removable handpiece handle assembly adapter and said handpiece handle assembly comprises a connector assembly, said connector assembly comprising:
           a housing comprising an opening and a canted slot;   a collet sleeve disposed within said opening and connected to an input shaft, said collet sleeve comprising a lumen for receiving an output shaft;   a locking element radially movable relative to said collet sleeve between (i) a locked position in which the said output shaft is secured to said collet sleeve, and (ii) an unlocked position in which the said output shaft is not secured to said collet sleeve;   a cam element longitudinally movable relative to said collet sleeve between (i) a first position in which said locking element is free to assume its said unlocked position, and (ii) a second position in which said cam element cams said locking element into said locked position, said cam element being yieldably biased into said second position;   a biasing collar for biasing said cam element into said first position;   a locking collar removably mounted to said housing; and   an element extending through said helical canted slot and secured to said biasing collar and said locking collar, such that rotation of said locking collar causes said element to move within said helical canted slot, whereby to cause said biasing collar to move said cam element into said first position;   
               
 
         [0098]    rotating said locking collar so as to cause said biasing collar to move said cam element into said first position; 
         [0099]    positioning a shaft in said lumen of said collet sleeve; and 
         [0100]    rotating said locking collar so as to cause said biasing collar to move within said housing so as to allow said cam element to assume its second position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0101]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
           [0102]      FIG. 1  is a schematic view showing a novel rotary tool provided in accordance with the present invention; 
           [0103]      FIG. 2  is an exploded schematic view of the novel rotary tool shown in  FIG. 1 ; 
           [0104]      FIG. 3  is a sectional schematic view of the novel rotary tool shown in  FIG. 1 ; 
           [0105]      FIGS. 4-13  are schematic views showing construction details of the novel rotary tool shown in  FIG. 1 ; 
           [0106]      FIGS. 14 and 15  are schematic views showing another novel rotary tool provided in accordance with the present invention; 
           [0107]      FIGS. 16 and 17  are schematic views showing still another novel rotary tool provided in accordance with the present invention; 
           [0108]      FIGS. 18 and 19  are schematic views showing construction details of the novel rotary tool shown in  FIGS. 16 and 17 ; 
           [0109]      FIGS. 20-24  are schematic views showing yet another novel rotary tool provided in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0110]    The present invention comprises the provision and use of a novel coupling assembly for releasably connecting a working element (e.g., a drill bit or burr) to a high speed motor of a handle assembly of a rotary tool. 
         [0111]    For purposes of clarity of description, the present invention will sometimes hereinafter be discussed in the context of a high speed drill bit or burr, however, it should be appreciated that the present invention is also applicable to other working elements, e.g., a dental polishing head, etc. 
         [0112]    Looking first at  FIGS. 1-3 , there is shown a novel rotary tool  5  for turning a working element (e.g., a drill bit or burr)  10 . Rotary tool  5  generally comprises a handle assembly  15  having a distal mount  20  extending distally therefrom, and a nosepiece assembly  22  mountable to, and fully removable from, distal mount  20  of handle assembly  15 . Nosepiece assembly  22  comprises a distal tip  23  for rotatably supporting working element  10 . 
         [0113]    More particularly, handle assembly  15  comprises a cavity  25  having a high speed motor  30  (e.g., an 80,000 rpm motor) disposed therein. Distal mount  20  of handle assembly  15  comprises a cavity  35 . Cavity  35  in distal mount  20  may be aligned with cavity  25  in handle assembly  15 . High speed motor  30  turns a shaft  40  which extends into cavity  35  in distal mount  20 . 
         [0114]    A coupling assembly  45 , generally disposed in distal mount  20  of handle assembly  15 , releasably receives the shaft  50  of working element  10  and selectively couples the shaft of the working element to high speed motor  30 . 
         [0115]    More particularly, and looking now at  FIG. 4 , coupling assembly  45  generally comprises a collet sleeve  55  which is secured to shaft  40  of high speed motor  30 . Collet sleeve  55  is preferably connected to shaft  40  of high speed motor  30  by a universal joint or a similar type of connector so as to minimize alignment and vibration issues. Collet sleeve  55  is sized to receive shaft  50  of working element  10  ( FIG. 3 ), and comprises at least one opening  60  extending through the side wall of collet sleeve  55 . In one preferred form of the invention, collet sleeve  55  comprises three openings  60  extending through the side wall of collet sleeve  55 . The three openings  60  may be equally-circumferentially spaced about the longitudinal axis of collet sleeve  55 . Collet sleeve  55  is rotatably mounted within cavity  35  of distal mount  20 , e.g., by a plurality of bearings  65 . In this way, when shaft  40  of high speed motor  30  is turned, collet sleeve  55  is also turned. In one preferred form of the invention, there is provided a distal bearing  65 A comprising an inner race  66 A secured to collet sleeve  55  and an outer race  67 A secured to distal mount  20 ; and a proximal bearing  65 B comprising an inner race  66 B secured to collet sleeve  55  and an outer race  67 B secured to distal mount  20 . 
         [0116]    In order for coupling assembly  45  to releasably secure shaft  50  of working element  10  to collet sleeve  55 , coupling assembly  45  also comprises at least one collet ball  70  (or other locking element) which is disposed in the at least one opening  60  of collet sleeve  55  (where three openings  60  are provided in collet sleeve  55 , three collet balls  70  may be provided, with one collet ball  70  being disposed in each opening  60 ). Note that the at least one opening  60  of collet sleeve  55  is configured so that the at least one collet ball  70  can protrude into the central lumen  75  of collet sleeve  55 , but the at least one collet ball  70  cannot pass completely into central lumen  75  of collet sleeve  55  due to the provision of shoulders  80  at the innermost points of the at least one opening  60 . In an alternative construction, the at least one opening  60  comprises at least one tapered opening, in which case shoulders  80  are replaced by the tapering side wall of the at least one tapered opening. 
         [0117]    A cam element  85  is disposed about collet sleeve  55 . Cam element  85  comprises a first surface  90  and a second surface  95 , with a transition surface  100  disposed therebetween. As will hereinafter be discussed, when first surface  90  of cam element  85  is aligned with the at least one collet ball  70 , the at least one collet ball  70  is free to move radially outward to the extent necessary so that the at least one collet ball  70  does not intrude into central lumen  75  of collet sleeve  55 ; at the same time, when first surface  90  of cam element  85  is aligned with the at least one collet ball  70 , first surface  90  will prevent the at least one collet ball  70  from completely exiting the at least one opening  60 , so that the at least one collet ball  70  will remain connected to collet sleeve  55 . As a result, when first surface  90  of cam element  85  is aligned with the at least one collet ball  70 , first surface  90  will limit radially-outward movement of the at least one collet ball  70  and prevent the at least one collet ball  70  from “completely falling out of” the at least one opening  60  and becoming loose within cavity  35 . However, when cam element  85  is moved proximally (e.g., under the power of a spring  105  or other biasing element), transition surface  100  of cam element  85 , and then second surface  95  of cam element  85 , will engage the at least one collet ball  70 , whereby to cam the at least one collet ball  70  radially inwardly, into central lumen  75  of collet sleeve  55  (whereby to secure the shaft  50  of a working element  10  to collet sleeve  55 ). 
         [0118]    It should be appreciated that cam element  85  and spring  105  rotate in conjunction with collet sleeve  55 , with spring  105  extending between the inner race  66 A of distal bearing  65 A and the distal end of cam element  85 . 
         [0119]    Note that in one preferred construction, three collet balls  70  are provided, one for each of three equally-circumferentially-spaced openings  60 , and shaft  50  of working element  10  has a triangular cross-section ( FIG. 5 ), whereby to provide a secure, stable connection between coupling assembly  45  and the shaft  50  of a working element  10  when the three collet balls  70  are forced radially inwardly into contact with the shaft  50  of a working element. Note also that, if desired, the at least one collet ball  70  can be replaced by at least one element having a different configuration, e.g., the at least one collet ball  70  may be replaced by at least one pin, by at least one finger, etc. 
         [0120]    A biasing collar  110  ( FIG. 4 ) is provided to selectively bias cam element  85  distally, against the power of its associated spring  105 . More particularly, biasing collar  110  is itself biased distally by a spring  115  (or other biasing element), such that when biasing collar  110  is unconstrained (see below), biasing collar  110  will engage the proximal end of cam element  85  so as to force cam element  85  distally, such that first surface  90  of cam element  85  is aligned with the at least one collet ball  70  ( FIG. 4 ). However, when biasing collar  110  is forced proximally (see below), against the power of spring  115 , cam element  85  is free to move proximally under the power of its associated spring  105 , so that transition surface  100  of cam element  85 , and then second surface  95  of cam element  85 , engage the at least one collet ball  70 , whereby to cam the at least one collet ball  70  radially inwardly, into central lumen  75  of collet sleeve  55 . In one preferred form of the invention, biasing collar  110  rides against the inner surface of mount  20  of handle assembly  15 . 
         [0121]    Note that spring  115  extends between the outer race  67 B of proximal bearing  65 B and the proximal end of biasing collar  110 . 
         [0122]    Note also that biasing collar  110  and spring  115  do not rotate with collet sleeve  55  when collet sleeve  55  is rotated by high speed motor  30  of handle assembly  15 , as will hereinafter be discussed. Means are provided for (i) selectively holding biasing collar  110  proximally spaced from cam element  85  (even when cam element  85  is biased proximally under the power of spring  105 ) so that frictional forces are not created between cam element  85  (which rotates with shaft  40  of high speed motor  30 ) and biasing collar  110  (which does not rotate with shaft  40  of high speed motor  30 ), and (ii) allowing the user to force biasing collar  110  proximally, against the power of spring  115 , so that cam element  85  can move proximally under the power of its associated spring  105  and thereby drive the at least one collet ball  70  into central lumen  75  of collet sleeve  55 , whereby to lock the shaft  50  of a working element  10  within coupling assembly  45 . 
         [0123]    More particularly, and looking now at  FIG. 6 , at least one canted cam slot  120  is provided in distal mount  20 . The at least one canted cam slot is canted with respect to the longitudinal axis of distal mount  20 . The at least one canted cam slot  120  extends proximally and circumferentially between a distalmost surface  125  and a proximalmost surface  130 . In one preferred form of the invention, the at least one canted cam slot  120  has a substantially straight configuration. In another preferred form of the invention, the at least one canted cam slot  120  has a substantially helical configuration. The at least one canted cam slot  120  also comprises a canted cam extension  135  which extends distally, and circumferentially, from proximalmost surface  130 . At least one pin (or other element)  140  ( FIG. 7 ), fixed to biasing collar  110 , extends radially through the at least one canted cam slot  120  of distal mount  20 , such that by moving the at least one pin  140  from its distalmost position within the at least one canted cam slot  120  ( FIGS. 6 and 8 ), biasing collar  110  can be moved from its distalmost position ( FIG. 4 ) to its proximalmost position ( FIG. 9 ). Thus, by moving the at least one pin  140  proximally within the at least one canted cam slot  120 , biasing collar  110  can be moved proximally within distal mount  20  so that cam element  85  is free to move proximally under the power of spring  105 , whereby to cam the at least one collet ball  70  radially inwardly, whereby to intrude into central lumen  75  of collet sleeve  55  (e.g., to grip the shaft  50  of a working element  10  inserted into central lumen  75  of collet sleeve  55 , or to prevent the shaft  50  of a working element  10  from being inserted into central lumen  75  of collet sleeve  55 ). In one preferred form of the invention, the at least one pin  140  is press fit or otherwise adhered to biasing collar  110 . 
         [0124]    In addition, by moving the at least one pin  140  into canted cam extension  135  of the at least one canted cam slot  120  ( FIG. 10 ), biasing collar  110  is releasably held proximally spaced from cam element  85  so that cam element  85  can cam the at least one collet ball  70  radially inwardly so as to grip the shaft  50  of a working element  10  (and also so that no frictional forces will be created between rotating cam element  85  and stationary biasing collar  110 ). In one preferred form of the invention, two canted cam slots  120 , which may be diametrically-opposed to one another, are provided in mount  20 , each having an associated canted cam extension  135 , and two diametrically-opposed pins  140  extend radially outward from biasing collar  110  and through the two diametrically-opposed canted cam slots  120  (see  FIG. 7 ). 
         [0125]    Means are also provided for moving the at least one pin  140  within the at least one canted cam slot  120 . More particularly, these means are provided by the aforementioned nosepiece assembly  22 . 
         [0126]    Looking now at  FIGS. 2 ,  3 ,  7  and  11 , nosepiece assembly  22  comprises means for supporting the shaft  50  of a working element  10  (e.g., distal tip  23 , which may include bearings  142 , see  FIGS. 2 and 3 ) and a locking collar  145  (see  FIGS. 7 and 11 ) disposed proximal to the aforementioned distal tip  23 . Locking collar  145  is rotatable relative to distal mount  20  of handle assembly  15  when nosepiece assembly  22  is mounted to a handle assembly  15 . In one preferred form of the invention, locking collar  145  and distal tip  23  rotate as a unit. In another preferred form of the invention, locking collar  145  is rotatable relative to distal tip  23 . In either case, however, locking collar  145  is rotatable relative to distal mount  20  of handle assembly  15  when nosepiece assembly  22  is mounted to handle assembly  15 . Note that where locking collar  145  is rotatable relative to distal tip  23 , distal tip  23  is secured against rotation relative to distal mount  20 , e.g., by the provision of a keying feature such as male-female connection, where the male feature is provided on one of the distal tip  23  and the distal mount  20 , and the female feature is provided on the other of the distal tip  23  and the distal mount  20 . 
         [0127]    Locking collar  145  generally comprises at least one groove (or slot)  150  for receiving the radially-outermost portion of the at least one pin  140  when nosepiece assembly  22  is mounted on distal mount  20  of handle assembly  15 . As a result, when locking collar  145  is rotated, the at least one pin  140  is also rotated, causing the at least one pin  140  to move proximally within the at least one canted cam slot  120  of distal mount  120 , and hence causing biasing collar  110  to move proximally within distal mount  20  (and hence allowing cam element  85  to move proximally under the power of spring  105 , whereby to cam the at least one collet ball  70  radially inwardly into the lumen  75  of collet sleeve  55 ). In one preferred form of the invention, where coupling assembly  45  comprises two pins  140  extending through two canted cam slots  120  of distal mount  120 , nosepiece assembly  22  comprises two grooves (or slots)  150  for receiving the two diametrically-opposed pins  140 . Where two pins  140 , two canted cam slots  120 , and two grooves (or slots)  150  are provided, each of the two pins  140 , two canted cam slots  120 , and two grooves (or slots)  150  may be diametrically-opposed from one another. 
         [0128]    In order to releasably lock nosepiece assembly  22  to distal mount  20 , distal mount  20  comprises an L-shaped groove (or slot)  155  ( FIG. 12 ) having a longitudinally-extending section  160  and a circumferentially-extending section  165 . Locking collar  145  of nosepiece assembly  22  comprises a ball  170  ( FIG. 11 ) which is received in L-shaped groove (or slot)  155 , i.e., ball  170  is received in longitudinally-extending section  160  when nosepiece assembly  22  is advanced onto distal mount  20  (or retracted off distal mount  20 ), and ball  170  is received in circumferentially-extending section  165  when locking collar  145  is rotated so as to (i) lock the shaft  50  of a working element  10  to coupling assembly  45  (and hence to handle assembly  15 ), or (ii) unlock the shaft  50  of a working element  10  from coupling assembly  45  (and hence from handle assembly  15 ). If desired, ball  170  can be replaced by a corresponding pin or finger or other element which is connected to locking collar  145  and is received in L-shaped groove (or slot)  155 . 
         [0129]    Thus it will be seen that nosepiece assembly  22  can be mounted to distal mount  20  of handle assembly  15  by aligning ball  170  of nosepiece assembly  22  with longitudinally-extending section  160  of L-shaped groove (or slot)  155  of distal mount  20 , and then moving the two parts together until ball  170  is aligned with circumferentially-extending section  165  of L-shaped groove (or slot)  155  of distal mount  20 . As this occurs, the at least one pin  140  of coupling assembly  45  is received in the at least one groove (or slot)  150  of locking collar  145 , and as nosepiece assembly  22  is mounted to distal mount  20  of handle assembly  15 , the at least one pin  140  of coupling assembly  45  is disposed at the distal end  125  of the at least one canted cam slot  120  of distal mount  20 . At this point, coupling assembly  45  is in the position shown in  FIG. 4  (i.e., unlocked). 
         [0130]    Thereafter, the shaft  50  of a working element  10  may be advanced into, or retracted from, central lumen  75  of collet sleeve  55 , since biasing collar  110  will normally force cam element  85  distally, so that the at least one collet ball  70  is free to move radially outward in the at least one opening  60  in collet sleeve  55 . The shaft  50  of a working element  10  can be advanced such that the at least one collet ball  70  is able to settle into at least one recess  175  ( FIG. 13 ) formed in the shaft  50  of a working element  10 . Note that in one preferred form of the invention, where three equally-circumferentially-spaced openings  60  and three collet balls  70  are provided, three equally-circumferentially-spaced recesses  175  are also provided, such that each equally-circumferentially-spaced recess  175  can receive one collet ball  70 . 
         [0131]    Locking collar  145  may then be rotated, whereby to cause the at least one pin  140  to move within the at least one canted cam slot  120 , whereby to force biasing collar  110  proximally. As this occurs, cam element  85  is free to move proximally, whereby to force the at least one collet ball  70  radially inwardly, whereby to lock shaft  50  of working element (e.g., a drill bit or burr)  10  to coupling  45 . 
         [0132]    At the end of the rotation of locking collar  145 , the at least one pin  140  settles into canted cam extension  135  of the at least one canted cam slot  120 . With the at least one pin  140  settled into canted cam extension  135  of the at least one canted cam slot  120 , biasing collar  110  is held proximally spaced from cam element  85 , so that there is no frictional contact between biasing collar  110  (which is rotationally stationary) and cam element  85  (which rotates with collet sleeve  55 ). 
         [0133]    At this point, motor  30  may be energized so as to rotate its shaft  40 , whereby to rotate collet sleeve  55  of coupling assembly  45 , and hence rotate working element  10  (which is releasably secured to collet sleeve  55 ). Working element  10  may then be used for its intended purpose, e.g., to drill or abrade bone. 
         [0134]    Thereafter, when working element  10  is to be released from handle assembly  15 , locking collar  145  of nosepiece assembly  22  is rotated again, but this time in the opposite direction, whereby to cause the at least one pin  140  to move out of canted cam extension  135  of the at least one canted cam slot  120 , and then distally along the at least one canted cam slot  120 , whereby to cause biasing collar  110  to move distally, such that cam element  85  also moves distally. As this occurs, cam element  85  allows the at least one collet ball  70  to move radially outwardly, whereby to free shaft  50  of working element  10  from handle assembly  15 . 
         [0135]    Note that in one preferred form of the invention, when the at least one pin  140  is in the at least one canted cam slot  120 , the power of spring  115  alone is insufficient to drive biasing collar  110  distally (and hence insufficient to drive the at least one pin  140  distally, and hence insufficient to rotate locking collar  145  about distal mount  20 ). In this form of the invention, manual movement of locking collar  145  is required to drive biasing collar  110  distally (and hence to drive the at least one pin  140  distally, and hence to rotate locking collar  145  about distal mount  20 ). 
         [0136]    However, in another form of the invention, when the at least one pin  140  is in the at least one canted cam slot  120 , the power of spring  115  alone is sufficient to drive biasing collar  110  distally (and hence sufficient to drive the at least one pin  140  distally, and hence sufficient to rotate locking collar  145  about distal mount  20 ). In this form of the invention, manual motion of locking collar  145  is only necessary to move the at least one pin  140  out of canted cam extension  135  and into the at least one canted cam slot  120 , and manual motion of locking collar  145  is not thereafter required to drive biasing collar  110  distally (and hence to drive the at least one pin  140  distally, and hence to rotate locking collar  145  about distal mount  20 ). 
         [0137]    In one preferred form of the invention, the equally-circumferentially-spaced recesses  175  may be provided in sets (e.g., sets of three equally-circumferentially-spaced recesses), and multiple sets of the equally-circumferentially-spaced recesses  175  may be provided in axially-spaced locations along shaft  50  of working element  10 , such that shafts of differing lengths may be accommodated. By way of example but not limitation, see  FIGS. 3 and 13 , which show four axially-spaced sets of three equally-circumferentially-spaced recesses  175  (i.e.,  175 A,  175 B,  175 C,  175 D) formed in shaft  50  of working element  10 . 
         [0138]    If desired, the at least one pin  140  may be replaced by at least one other element, e.g., at least one ball. Where a ball is used in place of a pin, the ball may be retained in a pocket formed in biasing collar  110 , and in another pocket formed in locking collar  145 , with the ball extending through the at least one canted cam slot  120 . However, the use of a pin offers significant advantages over the use of a ball, since (i) a pin can be press fit to biasing collar  110 , which provides a fast and simple connection between biasing collar  110  and the pin; (ii) the height of a pin is independent of the width of the pin, whereas the “height” of a ball is the same as the “width” of the ball—so that as the “height” of the ball is increased to make a secure engagement with locking collar  145 , the “width” of the ball must increase as well; and (iii) a pin generally makes a better camming contact with the at least one canted cam slot  120  than a ball. For at least these reasons, it is generally preferred to use a pin (rather than a ball) to connect biasing collar  110  to locking collar  145 . 
         [0139]    As seen in  FIGS. 14 and 15 , distal tip  23  of nosepiece assembly  22  may include a curved extension  180  for rotatably receiving a working element  10  having a flexible shaft. Note that where nosepiece assembly  22  comprises a curved extension  180  and working element  10  comprises a flexible shaft, it is common to drive the working element  10  at a slower speed than where the working element  10  is substantially straight and rigid, in order to reduce the stress on the flexible shaft of the working element  10  and thereby help preserve its working life. To this end, it can be advantageous to provide handle assembly  15  with means for detecting when distal tip  23  of nosepiece assembly  22  comprises a curved extension  180 . In one preferred form of the invention, and looking now at  FIG. 15 , handle assembly  15  can include a plurality of Hall sensors  185 , and nosepiece assembly  22  (comprising a distal tip  23  having a curved extension  180 ) can include a plurality of magnets  190 , such that handle assembly  15  can detect when a nosepiece assembly  22  (of the sort comprising a distal tip  23  having a curved extension  180 ) is mounted to handle assembly  15  (and hence reduce the operating speed of motor  30  so as to preserve the working life of the working element  10 ). 
         [0140]    Note that, if desired, and as shown in  FIGS. 14 and 15 , bearings  142  may be omitted from nosepiece assembly  22 , and shaft  50  of a working element  10  may be supported by a simple sliding contact made directly against nosepiece assembly  22 . 
         [0141]    As noted above, in accordance with the present invention, nosepiece assembly  22  is configured as a separate element from handle assembly  15 , and is mountable to, and fully removable from, distal mount  20  of handle assembly  15 . 
         [0142]    It should be appreciated that, by providing nosepiece assembly  22  as a fully-separable element from handle assembly  15 , it is possible to provide a wide variety of different nosepiece assemblies  22 , with each nosepiece assembly  22  being configured for a different purpose (e.g., for performing a different task, for supporting a differently-configured working element, etc.), with each nosepiece assembly  22  comprising a distal tip  23  for slidably supporting a working tool  10  and a locking collar  145  for engaging the at least one pin  140  of a coupling assembly  45  disposed in distal mount  20  of handle assembly  15 . 
         [0143]    Significantly, the nosepiece assembly may be configured to provide an angled shaft configuration. In this form of the invention, and looking now at  FIGS. 16-19 , there is provided a nosepiece assembly  22 A which comprises the aforementioned locking collar  145  for engaging the at least one pin  140  of coupling assembly  45  of handle assembly  15 , and the aforementioned distal tip  23  for slidably receiving the shaft  50  of a working tool  10 . However, in this form of the invention, nosepiece assembly  22 A also comprises a second coupling assembly  45 A, a second locking collar  145 A, and a pair of shafts  195 ,  200 . Second coupling assembly  45 A is substantially the same as the coupling assembly  45  previously disclosed, except that it is disposed in nosepiece assembly  122 A distal to locking collar  145 . Second locking collar  145 A is provided on nosepiece assembly  22 A and is configured to engage the at least one pin  140 A of second coupling assembly  45 A, whereby to lock or unlock a working element  10  to second coupling assembly  45 A. Shaft  200  is received by the aforementioned coupling assembly  45  in distal mount  20  of handle assembly  15  when nosepiece assembly  22  is mounted to handle assembly  15 , such that when locking collar  145  is rotated, shaft  195  is mechanically connected (via coupling assembly  45  in distal mount  20  of handle assembly  15 ) to drive shaft  40  of high speed motor  30 . Shaft  195  includes a beveled gear  205  at its distal end. Shaft  200  is connected to collet sleeve  55 A of coupling assembly  45 A, and includes a beveled gear  210  at its proximal end which is rotatably connected to gear  205  of shaft  195 , such that when shaft  40  of high speed motor  30  is rotated, collet sleeve  55 A is also rotated (i.e., via the intervening collet sleeve  55  of coupling assembly  45  of handle assembly  15 , and via the intervening shaft  195  and shaft  200  of nosepiece assembly  22 ). In this form of the invention, second coupling  45 A of nosepiece assembly  22  releasably receives the shaft  50  of working element  10 . Second locking collar  145 A of nosepiece assembly  22 A is used to selectively lock/unlock the shaft  50  of a working element  10  to second coupling assembly  45 A of nosepiece  22 A. 
         [0144]    Significantly, by forming nosepiece assembly  22 A so that the longitudinal axis of shaft  195  is set at an angle to the longitudinal axis of collet sleeve  55 A of second coupling  45 A, “off-angle” drilling can be effected without requiring the use of a nosepiece assembly having a curved extension  180  and a drill bit having a flexible shaft. This is a significant advance in the art, since it allows high speed “off angle” drilling or burring to be effected for prolonged periods of time without unduly limiting the life of working element  10 . 
         [0145]    If desired, the angled shaft nosepiece assembly  22 A ( FIGS. 16-19 ) can be provided as a single assembly, which mounts and dismounts as a unit from distal mount  20  of handle assembly  15 . 
         [0146]    Alternatively, if desired, and looking now at  FIGS. 20-24 , there is shown a nosepiece assembly  22 B which comprises (i) a nosepiece assembly  22 C, and (ii) a handle assembly adapter  22 D, wherein nosepiece assembly  22 C and handle assembly adapter  22 D are separable from one another ( FIGS. 20-22 ), but may be connected together, e.g., at the time of manufacture, at the time of use, etc. ( FIGS. 23 and 24 ), so as to together form the complete nosepiece assembly  22 B. The nosepiece assembly  22 B may be an angled shaft nosepiece assembly. 
         [0147]    In this form of the invention, nosepiece assembly  22 C may be identical to the aforementioned nosepiece assembly  22 , i.e., nosepiece assembly  22 C comprises a distal tip  23 C and a locking collar  145 C. 
         [0148]    In this form of the invention, handle assembly adapter  22 D may comprise a distal mount  20 D containing a coupling assembly  45 D which receives the shaft  50  of a working element  10  and is activated by locking collar  145 C of nosepiece assembly  22 C. And in this form of the invention, handle assembly adapter  22 D may comprise a shaft  195 D for being received in coupling assembly  45  in distal mount  20  of handle assembly  15 , and a shaft  200 D for transferring the rotation of shaft  195 D to collet sleeve  55 D of coupling assembly  45 D disposed in handle assembly adapter  22 D (and hence transferring rotation of shaft  195 D to the shaft  50  of a working element  10  disposed in central lumen  75 D of collet sleeve  55 D). In this form of the invention, handle assembly adapter  22 D comprises a locking collar  145 D for actuating coupling assembly  45  in distal mount  20  of handle assembly  15 . It will also be appreciated that in this form of the invention, handle assembly adapter  22 D is releasably secured to distal mount  20  of handle assembly  15  by loading locking collar  145 D of handle assembly adapter  22 D onto distal mount  20  of handle assembly  15  in a manner analogous to the manner in which nosepiece assembly  22  is mounted onto distal mount  20  of handle assembly  15 , and in this form of the invention, nosepiece assembly  22 C is releasably secured to distal mount  20 D of handle assembly adapter  22 D by loading locking collar  145 C of nosepiece assembly  22 C onto distal mount  20 D of handle assembly adapter  22 D in a manner analogous to the manner in which nosepiece assembly  22  is mounted onto distal mount  20  of handle assembly  15 . 
         [0149]    Thus it will be seen that, in this form of the invention, nosepiece assembly  22 B comprises a first mounting mechanism comprising a locking collar  145 D for securing handle assembly adapter  22 D to distal mount  20  of handle assembly  15 , and a second mounting mechanism for securing nosepiece assembly  22 C to distal mount  20 D of handle assembly adapter  22 D. However, it should also be appreciated that, if desired, an alternative mounting mechanism may be used to secure handle assembly adapter  22 D to distal mount  20  of handle assembly  15  (while still using a locking collar  145 C to secure nosepiece assembly  22 C to handle assembly adapter  22 D); and/or an alternative mounting mechanism may be used to secure nosepiece assembly  22 C to handle assembly adapter  22 D (while still using the aforementioned locking collar  145 D to secure handle assembly adapter  22 D to distal mount  20  of handle assembly  15 ). 
       MODIFICATIONS OF THE PREFERRED EMBODIMENTS 
       [0150]    It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.