Abstract:
A chuck for use with a power driver includes a generally cylindrical body, a plurality of jaws and a driving disk axially moveably disposed about the body in driving engagement with the jaws so that axial movement of the driving disk with respect to the body moves the jaws toward or away from the chuck body axis. The driving disk defines a threaded outer circumferential surface that engages a threaded inner circumferential surface of a generally cylindrical sleeve so that relative rotation between the sleeve and driving disk axially moves the driving disk with respect to the body. The driving disk defines a plurality of cylindrical slots extending at least partially radially therethrough. Each jaw includes a portion thereof that is shaped cooperatively with respect to the cylindrical slot and that is received thereby so that the jaw is axially fixed, and radially slidable with respect to the driving disk.

Description:
[0001]    This is a continuation of U.S. Application Ser. No. 09/507,158 filed Feb. 18, 2000, the entire disclosure of which is incorporated by reference herein and which claimed the benefit of U.S. Provisional Application No. 60/134,338, filed May 14, 1999. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to chucks for use with drills or with electric or pneumatic power drivers. More particularly, the present invention relates to a chuck of the keyless type which may be tightened or loosened by hand or by actuation of the driver motor.  
           [0003]    Both hand and electric or pneumatic tool drivers are well known. Although twist drills are the most common tools used with such drivers, the tools may also comprise screwdrivers, nut drivers, burrs, mounted grinding stones, and other cutting or abrading tools. Since the tools may have shanks of varying diameter or may have a polygonal cross-section, the device is usually provided with a chuck that is adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore.  
           [0004]    A wide variety of chucks have been developed in the art. In one form of chuck, three jaws spaced circumferentially approximately 120 E apart from each other are constrained by angularly disposed passageways in a body attached to the drive shaft. The chuck is configured so that rotation of the body in one direction with respect to a constrained nut forces the jaws into or away from gripping relationship with a tool shank. Such a chuck may be keyless if it can be tightened or loosened by manual rotation. An example of such chuck is disclosed in U.S. Pat. No. 5,125,673, commonly assigned to the present assignee and the entire disclosure of which is incorporated herein by this reference.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention recognizes and addresses disadvantages of prior art construction and methods.  
           [0006]    Accordingly, it is an object of the present invention to provide an improved chuck for use with a power driver.  
           [0007]    This and other objects are achieved by a chuck for use with a power driver having a rotatable spindle. The chuck includes a generally cylindrical body configured to rotate with the spindle. The body defines a tail section configured to rotate with the spindle of the power driver and a nose section having an axial bore formed therein. A plurality of jaws are in communication with the axial bore. A driving disk is axially movably disposed about the body in driving engagement with the jaws so that axial movement of the driving disk with respect to the body moves the jaws toward or away from the axis of the axial bore, depending on the direction of the axial movement. The driving disk defines a threaded outer circumferential surface. A generally cylindrical sleeve is rotatably mounted about the body and defines a threaded inner circumferential surface that engages the threaded outer surface of the driving disk so that relative rotation between the driving disk and the sleeve moves the driving disk axially with respect to the body. The driving disk defines a plurality of cylindrical slots extending at least partially radially therethrough. Each jaw includes a portion thereof that is shaped cooperatively with respect to the cylindrical slot. The jaw portion is received by the slot so that the jaw is axially fixed, and radially slidable, with respect to the driving disk.  
           [0008]    In another embodiment, a chuck includes a generally cylindrical body defining a tail section configured to rotate with the drive shaft of the power driver, a nose section having an axial bore formed therein, and a plurality of angularly disposed passageways in the nose section and intersecting the nose section axial bore. A plurality of jaws are respectively disposed in the passageways. A driving disk is axially movably disposed about the body in driving engagement with the jaws so that axial movement of the driving disk with respect to the body moves the jaws toward or away from the axis of the axial bore, depending on the direction of the axial movement. The driving disk defines a threaded outer circumferential surface. A generally cylindrical sleeve is rotatably mounted about the body and engages the jaws so that the jaws move axially forward with the driving disk. The driving disk defines a threaded inner circumferential surface that engages the threaded outer surface of the driving disk so that relative rotation between the driving disk and the sleeve moves the driving disk axially with respect to the body. A guide ring is axially fixed to the body and defines a generally frustoconical section that extends axially rearward from the passageways generally parallel to and abutting the jaws. In a still further embodiment of the present invention, a radially inward biased retainer replaces or supplements the guide and engages the jaws axially rearward of the passageways.  
           [0009]    In a still further embodiment of the present invention, a chuck includes a generally cylindrical body defining a tail section configured to rotate with the spindle of the power driver and a nose section having an axial bore formed therein. A plurality of jaws are in communication with the axial bore. A driving disk is axially movably disposed about the body in driving engagement with the jaws so that axial movement of the driving disk with respect to the body moves the jaws toward or away from the axis of the axial bore, depending on the direction of the axial movement. The driving disk defines a threaded outer circumferential surface. A generally cylindrical sleeve is rotatably mounted about the body and defines a threaded inner circumferential surface that engages the threaded outer surface of the driving disk so that relative rotation between the driving disk and the sleeve moves the driving disk axially with respect to the body. A bearing is disposed between the sleeve and the nose section of the body so that rearward axial force is transferred from the sleeve to the body through the bearing.  
           [0010]    In a further preferred embodiment of the present invention, a chuck includes a generally cylindrical body defining a tail section configured to rotate with the spindle of the power driver and a nose section having an axial bore formed therein. A plurality of jaws are in communication with the axial bore. A driving disk is axially moveably disposed about the body in driving engagement with the jaws so that axial movement of the driving disk with respect to the body moves the jaws toward or away from the axis of the axial bore, depending on the direction of the axial movement. The driving disk defines a threaded outer circumferential surface. A generally cylindrical sleeve is rotatably mounted about the body and defines a threaded inner circumferential surface that engages the threaded outer surface of the driving disk so that relative rotation between the driving disk and the sleeve moves the driving disk axially with respect to the body. The outer circumferential surface of the driving disk defines a discrete thread that extends at most 360° about the circumferential surface. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:  
         [0012]    [0012]FIG. 1 is a front plan view, partly in section, of a chuck in accordance with a preferred embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is a front plan view, partly in section, of the chuck as in FIG. 1 in a closed position;  
         [0014]    [0014]FIG. 3 is a cross-sectional view of the chuck as in FIG. 1 taken along the line  3 - 3 ;  
         [0015]    [0015]FIG. 4 is a cross-sectional view of the chuck as in FIG. 2 taken along the line  4 - 4 ;  
         [0016]    [0016]FIG. 5 is an exploded view of the chuck as in FIG. 1;  
         [0017]    [0017]FIG. 6 is a perspective view of the driving disk, back ring and jaws of the chuck as in FIG. 1;  
         [0018]    [0018]FIG. 7A is a rear view of a jaw as shown in FIG. 6;  
         [0019]    [0019]FIG. 7B is a side view of a jaw as shown in FIG. 6;  
         [0020]    [0020]FIG. 7C is a top view of a jaw as shown in FIG. 6;  
         [0021]    [0021]FIG. 7D is a bottom view of a jaw as shown in FIG. 6;  
         [0022]    [0022]FIG. 7E is a front view of a jaw as shown in FIG. 6;  
         [0023]    [0023]FIG. 8 is a perspective view of a driving disk, spring retainer and jaws for use in a chuck in accordance with a preferred embodiment of the present invention;  
         [0024]    [0024]FIG. 9A is a front plan view, partly in section, of a chuck in accordance with a preferred embodiment of the present invention;  
         [0025]    [0025]FIG. 9B is a perspective view of a guide ring as shown with the chuck in FIG. 9A;  
         [0026]    [0026]FIG. 10 is a front plan view, partly in section, of a chuck in accordance with a preferred embodiment of the present invention;  
         [0027]    [0027]FIG. 11 is an exploded view of a chuck in accordance with a preferred embodiment of the present invention;  
         [0028]    [0028]FIG. 12 is a partial perspective view of a driving disk and jaw of the chucks as in FIGS. 10 and 11;  
         [0029]    [0029]FIG. 13 is a cross-sectional view taken along the line  13  - 13  in FIG. 12; and  
         [0030]    [0030]FIG. 14 is a partial sectional front plan view of the chuck and one of the bearings as in FIG. 11.  
         [0031]    Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]    It is to be understood by one of ordinary skill in the art that the present discussion is a description of one or more exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary construction.  
         [0033]    Referring generally to FIGS. 1 and 5, a chuck  10  in accordance with the present invention has a central longitudinal axis depicted by the dashed line designated at  12 . Chuck  10  includes a front sleeve  14 , an optional rear sleeve  16  and a plurality of jaws  18 . A body  20  is generally cylindrical in shape and comprises a nose or forward section  22  and a tail or rearward section  24 . An axial bore  26  is formed in the nose section and is somewhat larger than the largest tool shank that the chuck is designed to accommodate. As should be understood in this art, body  20  may be formed from steel bar stock or any other suitable material.  
         [0034]    Body  20  defines threaded bore  28  in its tail section. Bore  28  is of a standard size to mate with the drive shaft of a powered or hand driver (not shown). While a threaded bore  28  is illustrated, such bore could be replaced with a tapered bore of a standard size to mate with a tapered drive shaft. The bores  26 ,  28  may communicate at a central region  30  of body  20 . Central region  30  may be formed with a socket to accept a drive bit so that the body may be screwed onto the spindle by the bit. Such a socket configuration is described in U.S. Pat. No. 5,193,824, incorporated herein by reference.  
         [0035]    Body  20  also defines three passageways  32  to respectively accommodate the three jaws  18 . In a three-jaw configuration, each passageway, and therefore each jaw, is separated from each adjacent passageway by an arc of approximately 120 E. The longitudinal axes of the passageways  32  and the jaws  28  are angled with respect to the chuck&#39;s longitudinal axis  12  but intersect the chuck axis at a common point ahead of chuck body  20 . Referring also to FIGS. 7B, 7D and  7 E, each jaw  18  has a tool engaging face  34  that is generally parallel to the longitudinal axis of chuck body  20 .  
         [0036]    Body  20  includes a thrust ring member  36 , which in a preferred embodiment forms an integral part of the body. Although not presently preferred, the thrust ring may be a separate component from the body&#39;s main portion. As shown in FIGS. 1 and 5, thrust ring  36  includes a ledge portion  40  that receives a bearing assembly  42 . The bearing assembly includes a bearing cage  44  enclosing bearing balls  46  that forwardly bear, with respect to chuck body  20 , on a forward washer  48  and rearwardly bear on a rearward washer  50 . Rearward race  50  abuts a shoulder surface  52  formed between the raised and ledge portions of thrust ring  36 . Forward race  48  bears in an axially forward direction against a shoulder  54  of sleeve  14 . Bearing assembly  42  may comprise any suitable construction, for example a bearing assembly of the type described in U.S. Pat. No. 5,348,318, incorporated herein by reference.  
         [0037]    Tail section  24  of body  20  can include a rear cylindrical portion having a knurled surface  56  thereon for receipt of rear sleeve  16 . The rear sleeve may be pressed onto the knurled surface, or could be retained in place by press fit without knurling or by use of a key. It could also be retained by crimping, staking, riveting, threading or any other suitable securing mechanism. Where front and rear sleeves  14  and  16  are replaced by a single sleeve extending substantially the length of body  20 , a retaining disk may be pressed or otherwise retained on tail section  24  to maintain the sleeve on the body in the rearward direction.  
         [0038]    At the front end of the chuck, nose section  22  is beveled and is adapted to receive a nosepiece  57  for restraining front sleeve  14  from forward axial movement with respect to the chuck body. Alternatively, a snap ring or other suitable mechanism may be used to axially restrain the sleeve. Nosepiece  57  may be pressed onto nose section  22  or attached in any other suitable manner. Rearward axial movement of the sleeve on the body is prevented by thrust ring  36  through bearing assembly  42 .  
         [0039]    The outer circumferential surface of sleeve  14  may be knurled or may be provided with longitudinal ribs or other protrusions to enable the operator to grip it securely. In like manner, the circumferential surface of rear sleeve  16 , if employed, may be knurled or ribbed if desired. The front and rear sleeves may be fabricated from a structural plastic such as polycarbonate, a filled polypropylene, for example glass filled polypropylene, or a blend of structural plastic materials. Other composite materials such as, for example, graphite filled polymerics could also be suitable in certain environments. Further, the sleeves may be constructed from suitable metals, such as steel. As would be appreciated by one skilled in the art, the materials from which the chuck of the present invention is fabricated will depend on the end use of the chuck, and the above are provided by way of example only.  
         [0040]    The interior surface  59  of sleeve  14  defines female threads  58 . The threads are a modified square thread formation in an eight pitch configuration along the length of sleeve  14 . It should be understood, however, that any suitable thread shape or formation may be employed, for example including a modified buttress thread. In one preferred embodiment, the squared interface  57  between the outer surface and back side of thread  58  is replaced by a curved surface.  
         [0041]    A driving disk  60  includes a male thread  62  extending about an outer circumferential surface  64 . Thread  62  has the same pitch as thread  58  so that when thread  62  is received by thread  58 , relative rotation between sleeve  14  and driving disk  60  moves the driving disk axially within the sleeve. In particular where the driving disk is molded, thread  62  may have sloped sides, for example at an approximately 5 E slope, extending from surface  64  to the thread&#39;s outer diameter.  
         [0042]    Referring also to FIGS. 6 and 7A- 7 E, driving disk  60  includes three equiangularly spaced apart slots  66  extending axially through the driving disk and receiving respective end sections  68  of jaws  18  therethrough. Each end section has a generally rectangular cross-section that corresponds to the cross-section of its slot  66  so that the slot slidably receives the jaw end section but prevents rotation of the jaw about the jaw&#39;s axis.  
         [0043]    Each end section  68  meets the generally cylindrical main portion of the jaw at an interface that defines two shoulders  70  on respective sides of the end section. The shoulders are formed at an angle φ between jaw axis  74  and a plane defined by shoulders  70  so that when the jaws are received in slots  32  of body  20 , the shoulders are flush against a flat front face  72  of driving disk  60 . In one preferred embodiment, front face  72  is perpendicular to the chuck axis, and angle φ is therefore equal to 90 E minus an angle Θ between jaw axis  74  and chuck axis  12 .  
         [0044]    Each end section  68  also defines a slot  76  extending generally radially into the end section parallel to the shoulders  70 . The end sections extend through the slots  66  so that slots  76  are rearward of and parallel to a flat rear face  78  of driving disk  60 .  
         [0045]    Each slot  76  receives a respective elongated spring arm  80  that extends inward from and generally circumferentially within a steel back ring  82 . Arms  80  bias their distal ends  84  radially inward with respect to back ring  82 . Thus, ends  84  engage closed ends  86  of slots  76  at respective grooves  88 . Grooves  88  grip the jaw end sections to restrain rotation of ring  82  about chuck axis  12  when jaws  18  are received in slots  32 . Furthermore, arms  80  axially fix ring  82  with respect to the jaws.  
         [0046]    Shoulders  70  and back ring  82  axially fix the jaws to driving disk  60 . Furthermore, the jaws pass both through driving disk slots  66  and body slots  32 , thereby rotationally securing the driving disk with respect to the body. Since the driving disk cannot rotate with respect to the body, rotation of sleeve  14  with respect to the body moves driving disk  60  axially with respect to chuck axis  12  by the cooperation between threads  62  and  58 . Depending on the sleeve&#39;s rotational direction, the driving disk moves axially forward or backward on the body and bears on either shoulders  70  or back ring  82  to move jaws  18  axially in slots  32  to an open or closed position.  
         [0047]    [0047]FIG. 1 shows jaws  18  retracted to a fully open position. Referring to FIG. 3, jaw end sections  68  are at their radially outwardmost position with respect to the chuck axis. As seen in FIG. 2, however, end sections  68  move radially inward toward axis  12  as the front sleeve&#39;s rotation moves driving disk  60  forward and jaws  18  to a closed position. Referring to FIG. 4, distal ends  84  nevertheless remain engaged in slots  76  due to the radially inward bias of arms  80 .  
         [0048]    Spring arms  80  help to maintain the jaws in an aligned position in passageways  32 . Specifically, as jaws  80  are pushed axially forward toward the chuck nose, the jaw outer surfaces  83  tend to push against an edge  85  defined by body  20  at the outer edge of passageways  32 . The jaws could pivot on this edge, pushing jaw noses  87  radially inward and end sections  68  radially outward. The spring arms, however, apply a radially inward force upstream of the passageways. This biases the jaws&#39; outer surface  83  against each passageway&#39;s inner surface  89  and thereby restrains the jaws from pivoting at edge  85 .  
         [0049]    Any suitable mechanism may be used to retain the jaws axially within the jaw passageways. For example, referring to a driving disk and jaw assembly shown in FIG. 8, back ring  82  (FIG. 6) may be replaced by a garter spring  91  or any other suitable retainer, such as an expandable polymer collar, that applies a radially inward force to jaw end sections  68 . The driving disk pushes the jaws back in an opening direction through the garter spring. Alternatively, the driving disk may be formed with T-shaped slots, one of which is indicated in phantom at  97 , instead of slots  66 . Each of three equiangularly spaced slots  97  extends radially into the driving disk from surface  64  parallel to front and rear faces  72  and  78 , and may extend entirely through the disk. Jaw end sections  68  are formed in a corresponding T-shape so that slots  97  slidably receive respective jaws. The slots allow the jaw ends to move radially as the driving disk moves the jaws between open and closed positions. A dry lubricant coating may be provided on the jaw ends and/or slots  97  to facilitate this movement. The cooperation between the jaw ends and slots  97  maintains the jaws at the proper angle with respect to the driving disk so that the jaws are maintained in alignment in the jaw passageways in the assembled chuck. In either of these embodiments, the chuck is otherwise constructed as shown in FIGS. 1, 2 and  5 .  
         [0050]    Referring to still another preferred embodiment of a chuck  10  shown in FIGS. 9A and 9B, a guide ring  93  is pressed onto body  20 . Three equiangularly spaced prongs  95  extend from ring  93  against respective jaw outer surfaces  83 . The prongs abut each jaw opposite (i.e. directly across the jaw&#39;s diameter from) the passageway surface  89  upstream from edge  85 . This prevents the jaws from pivoting outward behind edge  85  and thereby maintains the jaws in axial alignment with the passageways. Garter spring  91  provides an expandable collar through which the driving disk drives the jaws to an open position and provides additional inward bias. A T-slot construction as described above, or the back ring  82  (FIG. 6), could be used instead of an expandable collar.  
         [0051]    Referring again to FIGS. 1 through 7, when jaws  18  clamp onto a tool shank, rearward axial force is translated to front sleeve  14  through the jaws and the driving disk. This force is transferred to body  20  through bearing assembly  42  at shoulder  52 .  
         [0052]    Rotation of sleeve  14  clockwise, when viewed from nose section  22 , moves driving disk  60  axially forward with respect to chuck axis  12 , thereby moving jaws  18  to a closed position. Conversely, counterclockwise rotation of the front sleeve moves the jaws in an opening direction. Referring also to FIG. 5, a stop  92  is provided at the rear edge of thread  58 . When the jaws reach a fully open position as shown in FIG. 1, a rear edge  94  of thread  62  abuts stop  92 . This prevents further rotation of the sleeve with respect to the driving disk and thereby prevents the jaws from binding in the chuck&#39;s rear area. A similar stop  96  is provided at the front end of thread  58  to stop a forward edge  98  of thread  62  to prevent the jaws from binding in the fully closed position when there is no tool in chuck bore  26 .  
         [0053]    Thread  62  defines one turn around surface  64  of driving disk  60 . A gap  100  between thread edges  94  and  98  has an angular width greater than the width of stop  92 . This facilitates the chuck&#39;s assembly in that the driving disk may be placed directly down onto thread  58  over the stop. Rear sleeve  16  then prevents the driving disk from disengaging from the front sleeve when the chuck is in a fully opened position. While a slight gap is shown between the rear sleeve and the driving disk in FIG. 1, either or both of these components may be extended toward the other so that their edges  102  and  104  abut in the assembled chuck.  
         [0054]    While the Figures illustrate an eight-pitch thread, it should be understood that a higher pitch may be used to improve the mechanical advantage. For example, in one preferred embodiment, a sixteen-pitch thread is provided on the front sleeve and driving disk. The driving disk thread includes four turns, and the stop  92  (FIG. 5) is therefore attached to the sleeve by any suitable means after the driving disk is threaded into the sleeve, for example by riveting, plastic welding or a slot/key interface.  
         [0055]    Referring now to FIG. 10, a chuck  10  in accordance with the present invention includes a sleeve  14  that extends from body nose section  22  to tail section  24 . An axial bore  26  is formed in the nose section and is somewhat larger than the largest tool shank that the chuck is designed to accommodate.  
         [0056]    Body  20  defines a threaded bore  28  in its tail section. Bore  28  is of a standard size to mate with the drive shaft of a powered or hand driver (not shown). While a threaded bore  28  is illustrated, such bore could be replaced with a tapered bore of a standard size to mate with a tapered drive shaft. The bores  26 ,  28  may communicate at a central region of body  20 . The central region may be formed with a socket to accept a drive bit so that the body may be screwed onto the spindle by the bit.  
         [0057]    Body  20  also defines three passageways  32  to respectively accommodate the three jaws  18 . In a three-jaw configuration, each passageway, and therefore each jaw, is separated from each adjacent passageway by an arc of: approximately 120° . The longitudinal axes of the passageways  32  and the jaws  28  are angled with respect to the chuck&#39;s longitudinal axis but intersect the chuck axis at a common point ahead of the chuck body. Each jaw  18  has a tool engaging face  34  that is generally parallel to the longitudinal axis of the chuck body.  
         [0058]    Body  20  also includes a thrust ring member  36  that includes a ledge portion  40  that receives a bearing assembly  42 . The bearing assembly includes a bearing cage  44  enclosing bearing balls  46  that forwardly bear, with respect to chuck body  20 , on a forward washer  48  and rearwardly bear on a rearward washer  50 . Rearward race  50  abuts a shoulder surface  52  formed between the raised and ledge portions of thrust ring  36 . Forward race  48  bears in an axially forward direction against a shoulder  54  of sleeve  14 .  
         [0059]    Although the chuck as shown in FIG. 10 includes a single sleeve  14 , it should be understood that it may also include an optional rear sleeve as shown in FIG. 1. In such an arrangement, tail section  24  of body  20  may include a rear cylindrical portion having a knurled surface thereon for receipt of the rear sleeve.  
         [0060]    At the front end of the chuck, nose section  22  is beveled and is adapted to receive a nosepiece  57  for restraining sleeve  14  from forward axial movement with respect to the chuck body. Alternatively, a snap ring or other suitable mechanism may be used to axially restrain the sleeve. Nosepiece  57  may be pressed onto nose section  22  or attached in any other suitable manner. Rearward axial movement of the sleeve on the body is prevented by thrust ring  36  through bearing assembly  42 .  
         [0061]    The interior surface  59  of sleeve  14  defines female threads  58 . The threads are in an eight pitch configuration along the length of sleeve  14  and define a curved forward surface. It should be understood, however, that any suitable thread shape or formation may be employed, for example including a modified square thread or a modified buttress thread.  
         [0062]    A driving disk  60  includes a male thread  62  extending about an outer circumferential surface  64 . Thread  62  has the same pitch as thread  58  so that when thread  62  is received by thread  58 , relative rotation between sleeve  14  and driving disk  60  moves the driving disk axially within the sleeve. In particular where the driving disk is molded, thread  62  may have a shape that conforms with the curved surface of thread  58 .  
         [0063]    Referring also to FIGS. 11, 12 and  13 , driving disk  60  includes three equiangularly spaced apart radial slots  106  extending entirely radially through the disk. Slots  106  are cylindrical in shape and may be formed by boring radially inward into the driving disk outer surface with a suitable boring tool. As shown particularly in FIGS. 12 and 13, jaw end sections  68  are formed in a cooperating semi-circular shape so that slots  106  slidably receive the respective jaws. The slots allow the jaw ends to move radially as the driving disk moves the jaws between open and closed positions. A dry lubricant coating may be provided on the jaw ends and/or slots  106  to facilitate this movement. The cooperation between the jaw ends and slots  106  maintains the jaws at the proper angle with respect to the driving disk so that the jaws are maintained in alignment in the jaw passageways in the assembled chuck.  
         [0064]    Rotation of sleeve  14  clockwise, when viewed from nose section  22 , moves driving disk  60  axially forward with respect to the chuck axis, thereby moving jaws  18  to a closed position. Conversely, counterclockwise rotation of the front sleeve moves the jaws in an opening direction. Referring to FIG. 11, a stop  92  is provided at the rear edge of thread  58 . When the jaws reach a fully opened position, for example as shown in the embodiment of FIG. 1, a rear edge  94  of thread  62  abuts stop  92 . This prevents further rotation of the sleeve with respect to the driving disk. A similar stop (not shown) is provided at the front end of thread  58  to stop a forward edge  98  of thread  62  to prevent the jaws from binding in the fully closed position when there is no tool in the chuck bore.  
         [0065]    Thread  62  defines one turn that extends slightly less than 360° around surface  64  of driving disk  60 . A gap  100  between thread edges  94  and  98  has an angular width greater than the width of stop  92 . This facilitates the chuck&#39;s assembly in that the driving disk may be placed directly down onto thread  58  over the stop. A back plate  108  secured in a groove  110  by a snap-ring  112  prevents the driving disk from disengaging from the sleeve when the chuck is in a fully opened position in which rear thread edge  94  abuts stop  92 .  
         [0066]    Bearing assembly  42  may comprise any suitable construction. FIG. 11, for example, illustrates two bearing configurations  42   a  and  42   b.  In the embodiment indicated at  42   a,  the washer that forms bearing race  48  includes radially aligned recesses  114  in the washer&#39;s rearward face so that each of bearing balls  46  are received in a respective recess  114 .  
         [0067]    As it is rotated, sleeve  14  exerts a relative rotational force between races  48  and  50 . Normally, washer  48  carries balls  46  so that cage  44  rotates with washer  48 . Before the jaws close on the tool, however, there is relatively little rearward axial force against washer  50 . Thus, balls  46  slide against the washer, which remains in position against the chuck body. Where the frictional force between balls  46  and washer  50  is greater than that between sleeve  14  and washer  48 , the entire bearing assembly remains rotationally held to the body as the sleeve rotates.  
         [0068]    When the jaws close onto a tool shank, driving disk  60  exerts rearward axial force against sleeve  14 , which in turn translates this force to the body through bearing  42   a.  At this point, the increased frictional force between balls  46  and race  50  causes the balls to rotate against the washer, which is rotationally held by friction to thrust ring  36 . Since sleeve  14  rotationally drives washer  48  by friction, this causes balls  46  to roll out of their recesses  114  into the next recess. Continued rotation of sleeve  14  continues movement of the balls through successive recesses, causing a clicking sound that notifies the operator that the chuck is approaching a fully tightened position.  
         [0069]    In another embodiment, and referring also to FIG. 14, bearing  42   b  includes a first race  48  having recesses  114  defined about the radially outward edge of its rearward face. Opposite race  50  includes a shroud  116  extending axially forward therefrom. The shroud defines a plurality of spring arms  118  biased axially forward toward washer  48  so that tabs  120  defined at the distal ends of arms  118  engage respective recesses  114 . Thus, as sleeve  14  is rotated to a closed position, races  48  and  50  are rotationally linked to each other and rotate either with sleeve  14  or chuck body  20 , depending on whether the sleeve or the body exerts the greater frictional force on the bearing assembly. As should be understood by those skilled in this art, this depends on the dimensions of the components and the materials from which they are made. For example, where the bearing assembly and the body are made of metal, but the sleeve is made of a polymer material, the bearing typically remains with the body as the sleeve rotates.  
         [0070]    When the chuck jaws tighten onto a tool shank, however, frictional forces between washer  48  and sleeve  14  and between washer  50  and thrust ring  36  overcome the link between washers  48  and  50 . Further rotation of sleeve  14  therefore rotates washer  48  with respect to washer  50 , overcoming the biasing force of spring arms  118 . Thus, the arms are deflected so that each tab  120  moves out of its recess  114  and into the next recess. Continued rotation of sleeve  14  moves tabs  120  in and out of successive recesses, creating a clicking sound notifying the user that the chuck is approaching a fully closed position.  
         [0071]    Upon opening the chuck, having either bearing  42   a  or  42   b,  from a fully closed position, washers  48  and  50  initially rotate with respect to each other, again creating the clicking sound. As soon as the jaws release from the tool shank, however, the bearing assembly operates as described above prior to the fully closed position.  
         [0072]    It should be understood that the bearing assembly according to the present invention may be constructed in any suitable manner. For example, the recesses may be formed as radially extending dimples in the front face of washer  48 , as shown with respect to assemblies  42   a  and  42   b  in FIG. 11, or may comprise gaps between teeth extending radially outward from the washer&#39;s edge.  
         [0073]    While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. The embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. Thus, it should be understood by those of ordinary skill in this art that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the literal and equivalent scope of the appended claims.