Abstract:
A chuck including a body with a nose section defining an axial bore formed therein, a plurality of jaws movably disposed with respect to the body, and a sleeve rotatably mounted about the body so that rotation of the sleeve moves the jaws relative to the axial bore. A bearing has a first race, a second race, and at least one bearing element disposed therebetween, one of the first race and the second race defining a ratchet and the other defining a pawl biased toward the ratchet. A biasing element is disposed between the pawl and the sleeve. The biasing element exerts a biasing force on the pawl toward the ratchet and the ratchet and the pawl prevent the second race from rotating in the opening direction with respect to the first race when engaged.

Description:
This application is a continuation of U.S. patent application Ser. No. 13/706,524, filed Dec. 6, 2012, now U.S. Pat. No. 8,678,400, which is a continuation of U.S. patent application Ser. No. 13/186,296, filed Jul. 19, 2011, now U.S. Pat. No. 8,328,205, which is a continuation of U.S. patent application Ser. No. 12/772,413, filed May 3, 2010, now U.S. Pat. No. 7,984,913, which is a continuation of U.S. patent application Ser. No. 11/435,405, filed May 17, 2006, entitled “Locking Chuck,” now U.S. Pat. No. 7,708,288, which claims priority to U.S. Provisional Application No. 60/682,615, filed May 18, 2005, the entire disclosures of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     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 actuation of the driver motor. 
     Both hand and electric or pneumatic tool drivers are well known. Although twist drills are the most common tools on such drivers, the tools may also comprise screw drivers, nut drivers, burrs, mounted grinding stones, and other cutting or abrading tools. Since the tool shanks may be of varying diameter or of polygonal cross section, the device is usually provided with a chuck adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore. 
     A variety of chucks have been developed in the art. In an oblique jawed chuck, a chuck body includes three passageways disposed approximately 120° apart from each other. The passageways are configured so that their center lines meet at a point along the chuck axis forward of the chuck. The passageways constrain three jaws which are movable in the passageways to grip a cylindrical or polygonal tool shank displaced approximately along the chuck center axis. The chuck includes a nut that rotates about the chuck center and that engages threads on the jaws so that rotation of the nut moves the jaws in either direction within the passageways. The body is attached onto the drive shaft of a driver and is configured so that rotation of the body in one direction with respect to the nut forces the jaws into gripping relationship with the tool shank, while rotation in the opposite direction releases the gripping relationship. The chuck may be keyless if it is rotated by hand. Examples of such chucks are disclosed in U.S. Pat. Nos. 5,125,673 and 5,193,824, the entire disclosures of which are incorporated by reference herein. Various configurations of keyless chucks are known in the art and are desirable for a variety of applications. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods. 
     An embodiment of the present invention includes a chuck for use with a manual or powered driver having a rotatable drive shaft. The chuck includes a generally cylindrical body having a nose section and a tail section, the tail section being configured to rotate with the drive shaft and the nose section having an axial bore formed therein. A plurality of jaws are movably disposed with respect to said body in communication with said axial bore. A sleeve is rotatably mounted about the body in operative communication with the jaws so that rotation of the sleeve in a closing direction moves the jaws toward a longitudinal axis of the axial bore and rotation of the sleeve in an opening direction moves the jaws away from the longitudinal axis. A bearing has a first race adjacent the body, a second race adjacent the sleeve and at least one bearing element disposed between the first race and the second race. One of the first race and the second race define a ratchet and the other of the first race and the second race defines a pawl biased toward the ratchet, and a biasing element disposed between the pawl and the sleeve. The biasing element exerts a biasing force on said pawl toward said ratchet and wherein said ratchet and said pawl are configured so that when said pawl engages said ratchet, said ratchet and pawl prevent said second race from rotating in said opening direction with respect to said first race. 
     Another embodiment of the invention provides a chuck for use with a manual or powered driver having a rotatable drive shaft. The chuck includes a generally cylindrical body having a nose section and a tail section, the tail section being configured to rotate with the drive shaft and the nose section having an axial bore formed therein. A plurality of passageways are formed therethrough and intersect the axial bore. A plurality of jaws are movably disposed in said passageways. A generally cylindrical first sleeve is rotatably mounted about the body and in operative communication with the jaws so that rotation of the first sleeve in a closing direction moves the jaws toward a longitudinal axis of the axial bore and rotation of the first sleeve in an opening direction moves the jaws away from the longitudinal axis. A bearing has a first race adjacent the body, a second race adjacent the first sleeve and a plurality of bearing elements disposed between the first race and the second race. The first race defines a ratchet, the second race defines a deflectable first pawl biased toward the ratchet, the ratchet and the first pawl being configured so that when the first pawl engages the ratchet, the ratchet and first pawl permit the second race to rotate in the closing direction with respect to the first race but prevent the second race from rotating in the opening direction with respect to the first race. A biasing element is disposed between the second race and the first sleeve, and the biasing element is configured to bias the first pawl toward said ratchet. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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, which makes reference to the accompanying figures, in which: 
         FIG. 1  is a longitudinal view, partly in section, of a prior art chuck; 
         FIG. 2  is an exploded view of a chuck as shown in  FIG. 1 ; 
         FIG. 3  is an exploded view of the bearing and nut of the chuck as shown in  FIG. 1 ; 
         FIG. 4A  is a partial perspective view of the sleeve of the chuck as shown in  FIG. 1 ; 
         FIG. 4B  is a partial perspective view of the bearing and sleeve of the chuck as shown in  FIG. 1 ; 
         FIG. 4C  is a partial perspective view of the bearing and sleeve of the chuck as shown in  FIG. 1 ; 
         FIG. 5  is a perspective view of a chuck jaw of the chuck as shown in  FIG. 1 ; 
         FIG. 6  is an exploded view of a chuck in accordance with an embodiment of the present invention; 
         FIG. 7  is a longitudinal view, in section, of a chuck as shown in  FIG. 6 ; and 
         FIG. 8  is an exploded view of a chuck in accordance with an embodiment of the present invention. 
     
    
    
     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 
     Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the present disclosure. 
     Referring to  FIGS. 1 and 2 , a prior art chuck  10  includes a body  14 , a nut  16 , a front sleeve  18 , a nose piece  20  and a plurality of jaws  22 . Body  14  is generally cylindrical in shape and comprises a nose or forward section  24  and a tail or rearward section  26 . Nose section  24  has a front face  28  transverse to the longitudinal center axis  30  of body  14  and a tapered surface  32  at its forward end. The nose section defines an axial bore  34  that is dimensioned somewhat larger than the largest tool shank that the tool is designed to accommodate. A threaded bore  36  is formed in tail section  26  and is of a standard size to mate with the drive shaft of a powered or hand driver (not shown). The bores  34 ,  36  may communicate at a central region  38  of body  14 . While a threaded bore  36  is illustrated, such bore could be replaced with a tapered bore of a standard size to mate with a tapered drive shaft. Furthermore, body  14  may be formed integrally with the drive shaft. 
     Body  14  defines three passageways  40  to accommodate the three jaws. Each jaw is separated from the adjacent jaw by an arc of approximately 120°. The axes of passageways  40  and jaws  22  are angled with respect to the chuck center axis  30  such that each passageway axis travels through axial bore  34  and intersects axis  30  at a common point ahead of the chuck body. The jaws form a grip that moves radially toward and away from the chuck axis to grip a tool, and each jaw  22  has a tool engaging face  42  generally parallel to the axis of chuck body  14 . Threads  44 , formed on the jaw&#39;s opposite or outer surface, may be constructed in any suitable type and pitch. As shown in  FIG. 5 , each jaw  22  may be formed with a carbide insert  112  pressed into its tool engaging surface. 
     As illustrated in  FIGS. 1 and 2 , body  14  includes a thrust ring  46  that, preferably, may be integral with the body. It should be understood, however, that thrust ring  46  and body  14  may be separate components. Thrust ring  46  includes a plurality of jaw guideways  48  formed around its circumference to permit retraction of jaws  22  therethrough and also includes a ledge portion  50  to receive a bearing assembly as described below. 
     Body tail section  26  includes a knurled surface  54  that receives an optional rear sleeve  12  in a press fit at  55 . Rear sleeve  12  could also be retained by press fit without knurling, by use of a key or by crimping, staking, riveting, threading or any other suitable securing mechanism. Further, the chuck may be constructed with a single sleeve having no rear sleeve. 
     Nose piece  20  retains nut  16  against forward axial movement. The nose piece is press fit to body nose section  24 . It should be understood, however, that other methods of axially securing the nut on the body may be used. For example, the nut may be a two-piece nut held on the body within a circumferential groove on the outer circumference of the body. Nose piece  20  may be coated with a non-ferrous metallic coating to prevent rust and to enhance its appearance. Examples of suitable coatings include zinc or nickel, although it should be appreciated that any suitable coating could be utilized. 
     The outer circumferential surface of front sleeve  18  may be knurled or may be provided with longitudinal ribs  77  or other protrusions to enable the operator to grip it securely. In like manner, the circumferential surface of rear sleeve  12 , if employed, may be knurled or ribbed as at  79  if desired. 
     Front sleeve  18  is secured from movement in the forward axial direction by an annular shoulder  91  on nose piece  20 . A frustoconical section  95  at the rearward end of the nose piece facilitates movement of jaws  22  within the chuck. 
     The front and rear sleeves may be molded or otherwise fabricated from a structural plastic such as polycarbonate, a filled polypropylene, for example a glass filled polypropylene, or a blend of structural plastic materials. Other composite materials such as, for example, graphite filled polymerics may also be suitable in certain environments. As should be appreciated by one skilled in the art, the materials from which the chuck is fabricated will depend on the end use of the chuck. 
     Nut  16  has threads  56  for mating with jaw threads  44 . Nut  16  is positioned about the body in engagement with the jaw threads so that when the nut is rotated with respect to body  14 , the jaws will be advanced or retracted depending on the nut&#39;s rotational direction. 
     As illustrated in  FIG. 3 , the nut&#39;s forward axial face includes recesses  62  that receive respective drive dogs  64  ( FIG. 2 ) extending from the inner surface of front sleeve  18 . The angular width of the drive dogs is less than that of the recesses, resulting in a slight range of relative rotational movement, for example between 6° and 10° between the nut and the front sleeve. 
     Nut  16  also defines a plurality of grooves formed as flats  68  about the nut&#39;s outer circumference. Flats  68  receive respective tabs  70  extending forward from an inner race  72  of a bearing assembly  74 . The engagement of tabs  70  and flats  68  rotationally fix the inner race to the nut, although it should be understood that there may be a slight rotational tolerance between the two. 
     Inner race  72  receives a plurality of bearing elements, in this case bearing balls  76 , disposed between it and an outer race  78  seated on thrust ring ledge  50  ( FIG. 1 ). Outer race  78  is rotationally fixed to body  14  by a plurality of tabs  80  received in corresponding grooves  82  in the thrust ring ledge. In an embodiment of the invention described herein, outer race  78  is not rotationally fixed with respect to the thrust ring, and tabs  80  and grooves  82  are therefore omitted. In such embodiment, outer race  78  can rotate with respect to the body until the jaws close onto a tool shank, at which point rearward force from the nut through the bearing gives rise to friction between outer race  78  and the thrust ring that holds the outer race in place rotationally on the body. 
     Returning to the prior art chuck in  FIGS. 1 through 3 , outer race  78  also includes a ratchet formed by a plurality of sawtooth-shaped teeth  84  disposed about the inner circumferential surface of the outer race. A first pawl  86  extends from one side of each tab  70 . First pawl  86  is biased radially outward from the inner race, thereby urging a distal end  88  of each first pawl  86  towards the outer race ratchet. 
     Each tooth  84  has a first side with a slope approaching 90° with the periphery of the outer race. A second side of each tooth  84  has a lesser slope. First pawl  86  is deflectable and is generally disposed in alignment with the slope of the second side. Thus, rotation of inner race  72  in a closing direction  90  with respect to outer race  78  moves first pawl distal ends  88  repeatedly over teeth  84 , causing a clicking sound each as end  88  falls against each subsequent tooth second side. This configuration of teeth and first pawls  86 , however, prevents the inner race&#39;s rotation in an opposite opening direction  92 . Application of rotational force to the inner race in this direction forces distal ends  88  into the steep-sloped first sides of teeth  84 . Since pawl  86  is generally perpendicular to the first sides, it does not deflect inward to permit rotation. As discussed below, direction  90  corresponds to the chuck&#39;s closing direction, while direction  92  corresponds to the chuck&#39;s opening direction. Accordingly, when pawls  86  engage ratchet teeth  84 , the teeth permit the inner race&#39;s movement in the chuck&#39;s closing direction  90  but prevent its movement in the opening direction  92 . 
     A second deflectable pawl  94  extends from the other side of each tab  70 . Like first pawls  86 , each second pawl  94  is biased radially outward. Unlike first pawls  86 , however, second pawls  94  do not engage the outer race ratchet. 
     First and second pawls  86  and  94  include tabs  96  and  98 , respectively, at their distal ends. Referring also to  FIG. 4A , an inner circumferential surface of sleeve  18  defines first and second recesses  100  and  102 . During the chuck&#39;s operation, each tab  98  is received in one of these recesses, depending on the sleeve&#39;s rotational position with respect to the nut as discussed in more detail below. The sleeve also defines a third recess  104  and a cam surface  106 . Also depending on the sleeve&#39;s rotational position, each tab  96  is received either by the cam surface or by recess  104 . The sleeve includes a pair of recesses  100 ,  102  for each tab  98  and a recess  104  and cam surface  106  for each tab  96 . 
       FIG. 4C  illustrates the disposition of pawls  86  and  94  when sleeve  18  is in a first of two positions with respect to nut  16 , while  FIG. 4B  illustrates these components when the sleeve is in a second position with respect to the nut. For ease of illustration, both figures omit the nut. However, referring to  FIG. 2  and to the sleeve&#39;s second position as shown in  FIG. 4B , each drive dog  64  is disposed against or adjacent to a side  108  of the gap  62  in which it is received. Each of the sleeve&#39;s recesses  102  receives a tab  98  of a second pawl  94 , and each recess  104  receives a tab  96  of a first pawl  86 . Accordingly, the distal end  88  of each first pawl  86  engages ratchet teeth  84 , and inner race  72  can rotate only in direction  90  with respect to outer race  78 . 
     Referring now to  FIG. 4C , when front sleeve  18  moves in opening direction  92  with respect to outer race  78 , each tab  98  moves out of its recess  102  and into its recess  100 , as indicated by arrow  107 . Each tab  96  rides up and out of its recess  104  onto its cam surface  106 , as indicated by arrow  110 . As indicated by arrow  113 , this pushes each deflectable tab  86  radially inward, thereby disengaging distal ends  88  from ratchet teeth  84 . Thus, the inner race is free to rotate with respect to the outer race. 
     As described in more detail below, when sleeve  18  rotates in opening direction  92  so that the inner race moves from the position shown in  FIG. 4B  to the position shown in  FIG. 4C , drive dogs  64  move within groove  62  of nut  16  ( FIG. 2 ) so that each drive dog is against or immediately adjacent to a side  111  of the groove. 
     In operation and referring to  FIGS. 2, 3, 4B and 4C , when the chuck is between the fully opened and the fully closed positions, nut grooves  62  receive drive dogs  64  so that the drive dogs are adjacent groove sides  111 . Inner race  72  is disposed with respect to outer race  78  so that tabs  96  and  98  are received by cam surface  106  and recess  100 , respectively. That is, sleeve  18  is in the first position with respect to the nut, as shown in  FIG. 4C . In this condition, tabs  98  and recesses  100  rotationally fix inner race  72  to sleeve  18 . Since inner race  72  is rotationally fixed to nut  16  by tabs  70  and flats  68 , an operator rotating sleeve  18  rotationally drives the nut through the bearing&#39;s inner race  72 , thereby opening or closing the jaws. When the operator rotates the sleeve, the bearing inner race and the nut in the closing direction (indicated by arrow  90  in  FIG. 4C ) to the point that the jaws tighten onto a tool shank, the nut is urged rearward up the jaw threads, thereby pushing the nut against inner race  72 , bearing elements  76 , outer race  78 , and thrust ring  46 . The rearward force creates a frictional lock between the nut and inner race  72  that further holds the inner race and the nut in place rotationally with respect to the body. 
     The wedge between the nut threads and jaw threads increasingly resists the nut&#39;s rotation. When the operator continues to rotate sleeve  18  and the resistance overcomes the hold provided by tabs  98  in recesses  100 , sleeve  18  rotates with respect to nut  16  and inner bearing race  72 . This moves drive dogs  64  from sides  111  of grooves  62  to sides  108  and pushes tabs  98  out of recesses  100  into recesses  102 . Simultaneously, cam surfaces  106  rotate away from tabs  96  so that the tabs are released into recesses  104 , thereby engaging distal ends  88  of first pawls  86  with ratchet teeth  84 , as shown in  FIG. 4B . At this point, inner race  72 , and therefore nut  16 , is rotationally locked to outer race  78 , and therefore body  14 , against rotation in the chuck&#39;s opening direction. That is, the nut is rotationally locked to the chuck body in the opening direction. Since the nut&#39;s rotation with respect to the body is necessary to open the chuck, this prevents inadvertent opening during use. 
     Inner race  72 , and therefore nut  16 , may, however, still rotate with respect to outer race  78 , and therefore body  14 , in the chuck&#39;s closing direction. During such rotation, sleeve  18  drives nut  16  through drive dogs  64  against groove sides  108 , as well as through inner race  72 . This continues to tighten the chuck and as described above and produces a clicking sound to notify the operator that the chuck is in a fully tightened position. 
     To open the chuck, the operator rotates sleeve  18  in opening direction  92 . Sleeve  18  transfers this torque to inner race  72  at the engagement of tabs  96  and  98  in recesses  104  and  102 , respectively. Because pawls  86  engage outer race  78 , which is rotationally fixed to the body, the inner race cannot rotate with the sleeve. Thus, upon application of sufficient torque in opening direction  92 , sleeve  18  moves with respect to the inner race and the nut. This moves tab  96  back up onto cam surface  106 , thereby disengaging first pawl  86  from ratchet teeth  84 . Tab  98  moves from second recess  102  into first recess  100 , and drive dogs  64  move from sides  108  to sides  111  of grooves  62 . Thus, the sleeve moves to its first position with respect to the nut, as shown in  FIG. 4C , and the inner race and nut are free to rotate with respect to the outer race and chuck body. Accordingly, further rotation of sleeve  18  in the opening direction moves jaws  22  away from the chuck axis, thereby opening the chuck. 
     The pawls and ratchet may be formed in any suitable configuration. Furthermore, the chuck may be realized in a variety of configurations whereby a bearing having a ratchet configuration is disposed between a sleeve, for example a nut or other suitable configuration, and the chuck body. For example, a chuck may include a body, a nut that is rotationally fixed to and axially movable with respect to the body, and an outer sleeve that threadedly engages the nut so that rotation of the sleeve moves the nut axially on the body. The jaws may be axially fixed to the nut and received in body passageways so that the nut&#39;s axial movement drives the jaws towards and away from the chuck&#39;s axis. In this configuration, an outer sleeve may be permitted to rotate over a limited angular distance with respect to a second sleeve. A bearing including a ratchet configuration as discussed above may be disposed between the second sleeve and the chuck body. Depending on the chuck&#39;s configuration, the pawls and ratchet may be interchanged as appropriate. 
       FIGS. 6 and 7  illustrate an embodiment of a chuck  11  of the present invention having a body  14 , a nut  16 , a front sleeve  18  (comprised of a metal outer part  19 , a polymer inner part  21  and a metal insert  17 ), a nose piece  20  and a plurality of jaws  22 . An embodiment shown in  FIG. 8  has a front sleeve  18  comprised of a metal outer part  19  and a polymer inner part  21  without a metal insert. Body  14 , which is constructed substantially the same as the body described above with respect to  FIG. 2 , is generally cylindrical in shape and comprises a nose or forward section  24  and a tail or rearward section  26 . Nose section  24  has a forward end  32  that tapers from a smooth cylindrical outer circumference to a front face transverse to the longitudinal center axis of body  14 . The nose section defines an axial bore  34  that is dimensioned somewhat larger than the largest tool shank the tool is designed to accommodate. A threaded bore  36  is formed in tail section  26  and is of a standard size to mate with the drive shaft of a powered or hand driver (not shown). Front bore  34  and rear bore  36  may communicate at a central region  38  of body  14 . While a threaded bore  36  is illustrated, such bore could be replaced with a tapered bore of a standard size to mate with a tapered drive shaft. Furthermore, body  14  may be formed integrally with the drive shaft. A rear ring  37  is also formed integrally with body  14  and defines a plurality of guideways  39  to accommodate jaws  22  in their rearward positions. 
     Body  14  defines three passageways  40  to accommodate the three jaws. Each jaw is separated from the adjacent jaw by an arc of approximately 120°. The axes of the jaw passageways and jaws  22  are angled with respect to the chuck center axis such that each passageway axis travels through the forward axial bore in the body and intersects the chuck axis at a common point. The jaws form a grip that moves radially toward and away from the chuck axis to grip a tool, and each jaw  22  has a tool engaging face  42  generally parallel to the axis of chuck body  14 . Threads  44 , formed on each jaw&#39;s opposite or outer surface, may be constructed in any suitable type and pitch. As also indicated in  FIG. 5 , each jaw  22  may be formed with one or more carbide inserts  112  pressed into its tool engaging surface. 
     As illustrated in  FIGS. 6 through 8 , body  14  includes a thrust ring  46  that, in a preferred embodiment, may be integral with the body. It should be understood, however, that thrust ring  46  and body  14  may be separate components. Thrust ring  46  includes a plurality of jaw guideways  48  formed around its circumference to permit retraction of jaws  22  therethrough and includes a ledge portion  50  to receive a bearing assembly as described below. 
     Body tail section  26  includes a knurled surface  54  that receives a dust cover  13  in a press fit. Dust cover  13  could also be retained by press fit without knurling, by use of a key or by crimping, staking, riveting, threading or any other suitable securing mechanism. Further, the chuck may be constructed with two hand-actuatable sleeves, as shown in  FIGS. 1 and 2 . Nose piece  20  is press fit to body nose section  24  and retains nut  16  against forward axial movement. Nose piece  20  may be coated with a non-ferrous metallic coating to prevent rust and to enhance its appearance. Examples of suitable coatings include zinc or nickel, although it should be appreciated that any suitable coating could be utilized. It should also be understood that other methods of axially securing the nut on the body may be used. For example, the nut may be a two-piece nut held on the body within a circumferential groove on the body&#39;s outer circumference. 
     Front sleeve  18  is secured from movement in the forward axial direction by an annular shoulder  91  on nose piece  20 . A frustoconical section  95  at the rearward end of the nose piece facilitates movement of jaws  22  within the chuck. 
     The outer circumferential surface of front sleeve outer part  19  may knurled or may be provided with longitudinal ribs or other protrusions to enable the operator to grip it securely. Outer front sleeve part  19  and metal insert  17  ( FIGS. 6 and 7 ) may be deep drawn or otherwise fabricated from steel or other metal material such as Zamac (zinc aluminum metal alloy casting). The metal insert is preferably steel hardened to an HRC 43-51 Inner sleeve part  21  may be molded or otherwise fabricated from a structural plastic such as polycarbonate, a filled polypropylene, for example a glass filled polypropylene, or a blend of structural plastic materials. Other composite materials such as, for example, graphite filled polymerics may also be suitable in certain environments. Metal insert  17  may be pressed or otherwise assembled inside inner sleeve part  21  in close conformity so that the inner sleeve part retains the metal insert. In one preferred embodiment, inner sleeve part  21  is molded about the metal insert. As should be appreciated by one skilled in the art, the materials from which the chuck of the present invention is fabricated will depend upon the end use of the chuck, and the above materials are provided by way of example only. 
     Generally, the outer surface of inner part  21  conforms to the inner surface of outer part  19 . However, polymer inner part  21  defines a plurality of flanges  23  that extend forward from the main portion of the inner sleeve part. Flanges  23  include front edges  25  that extend radially outward to thereby define a groove  27  between edges  25  and the front edge of the inner sleeve part&#39;s main portion. The segmented arrangement of flanges  23  allows the flanges to flex inward as the outer part is assembled over the inner part. A front edge  29  of outer sleeve part  19  extends radially inward and is notched to receive flanges  23 . Thus, at the notches, front edge  29  extends radially inward into groove  27 , while flanges  23  extend through the notches. Thus, groove  27  retains outer sleeve part  19  in the axially forward and rearward directions between the tabs&#39; front edges  25  and the forward edge of the main portion of sleeve inner part  21 . Sleeve outer part  19  rotationally drives sleeve inner part  21  through the interengagement of front edge  29  and flanges  23  and through a plurality of spaced-apart dogs (not shown) extending radially inward from the outer sleeve part&#39;s inner circumferential surface into corresponding notches  31  in the front outer surface of inner sleeve part  21 . It should be understood that the two-part sleeve shown in  FIGS. 6 through 8  may be replaced with a unitarily-formed polymer sleeve such as shown in  FIGS. 1 and 2 . 
     Nut  16  has threads  56  for mating with jaw threads  44  and is positioned about the body in engagement with the jaw threads so that when the nut is rotated with respect to body  14 , the jaws will be advanced or retracted depending on the nut&#39;s rotational direction. 
     The nut&#39;s forward axial face includes recesses  62  that receive respective drive dogs  64  extending from the inner surface of inner sleeve part  21 . Recesses  62  and drive dogs  64  are constructed as described above with respect to  FIG. 2 . Similarly, the inner surface of metal insert  17  (or, in the embodiment of  FIG. 8 , sleeve inner part  21 ) defines recesses  100 ,  102  and  104  and a cam surface  106  as is described above with respect to the inner surface of sleeve  18  in  FIGS. 1 and 2 . For the purpose of clarity, the positions of recesses  100 ,  102  and  104  and cam surface  106  in inner sleeve part  21  behind insert  17  are indicated in  FIG. 6  as recesses  100   a ,  102   a , and  104   a , and cam surface  106   a.    
     Nut  16  also defines a plurality of grooves, formed as flats  68  about the nut&#39;s outer circumference, that receive respective tabs  70  extending forward from an inner race  72  of a bearing assembly  74 . The engagement of tabs  70  and flats  68  rotationally fix the inner race to the nut, although it should be understood that there may be a slight rotational tolerance between the two. 
     Inner race  72  receives a plurality of bearing elements, in this case bearing balls  76 , disposed between it and an outer race  78  seated on thrust ring ledge  50 . Outer race  78  is rotationally fixed to body  14  by a plurality of tabs  80  received in corresponding grooves  82  in the thrust ring ledge, as is described above with respect to  FIGS. 1 and 2 . In an alternate embodiment, outer race  78  is not rotationally fixed with respect to the thrust ring, and the tabs and grooves are therefore omitted. In such alternate embodiment, outer race  78  can rotate with respect to the body until the jaws close onto a tool shank, at which point rearward force from the nut through the bearing gives rise to friction between outer race  78  and thrust ring ledge  50  that ultimately holds the outer race in place rotationally on the body. 
     As discussed above with respect to outer race  78  in  FIG. 2 , outer races  78  in  FIGS. 6 through 8  include a ratchet. In the illustrated embodiments, the ratchet is formed by a plurality of saw tooth-shaped teeth  84  disposed about the outer race&#39;s inner circumferential surface. A first pawl  86  extends from one side of each tab  70  and is biased radially outward from the inner race, thereby urging a distal end  88  of each first pawl  86  toward the outer race ratchet. Teeth  84  are formed, and interact with pawl distal end  88 , as described above with respect to the corresponding components of  FIGS. 1 through 4 . 
     A second deflectable pawl  94  extends from the other side of each tab  70 . Like first pawls  86 , each second pawl  94  is biased radially outward. Unlike first pawls  86 , second pawls  94  do not engage the outer race ratchet. Pawls  86  and  94  are constructed identically to pawls  86  and  94  as described above with respect to  FIGS. 1 and 2 . First and second pawls  86  and  94  include tabs  96  and  98 , respectively, at their distal ends that interact with recesses  100 ,  102  and  104 , and cam surface  106 , in the same manner as described above. Moreover, the operation of the chucks shown in  FIGS. 6 through 8 , with respect to opening, closing and locking by the interaction of pawls  86  and  94  with the inner surface of sleeve  18  (more particularly, the inner surface of metal insert  17  in  FIGS. 6 and 7  and inner sleeve part  21  in  FIG. 8 ), is the same as the operation of chuck  10  shown in  FIGS. 1 through 4 , and is therefore not repeated. 
     In drill chuck  10  as shown in  FIGS. 1 and 2 , nut  16  defines a smooth cylindrical shoulder  130  extending in the axial direction between a curved surface  132  and a transverse annular shoulder  134  extending between shoulder  130  and an annular shoulder  136  upon which flats  68  are defined. In the embodiments of the present invention illustrated in  FIGS. 6 through 8 , a resilient structure is disposed between shoulder  130  and first and second pawls  86  and  94  in sufficient volume and/or geometry so that the resilient intermediate structure increases the pawls&#39; radially outward bias to thereby dampen vibrations that arise from the chucks&#39; usage with a given power driver and that otherwise tend to dislodge the pawls from their positions with respect to the outer race and sleeve, as shown in  FIGS. 4B and 4C . 
     As shown in  FIGS. 6 through 8 , for example, a groove  138  is formed in shoulder  130  so that, when nut  16  is assembled onto body  14 , groove  138  is defined in a plane perpendicular to the chuck axis and receives an O-ring  140 . In one preferred embodiment, O-ring  140  is made of VITON, a fluoroelastomer manufactured by DuPont Dow Elastomers LLC of Wilmington, Del., and has an axial width of about 1/16 inches, an inner diameter of about 1.000 inches and an outer diameter of about 1.125 inches. 
     The diameter defined by shoulder  130  on either side of groove  138  is approximately 1.244 inches, while the diameter of a circle defined by the trough of groove  138  is approximately 1.200 inches. Thus, O-ring  140  stretches when installed into groove  138 , and its outer diameter becomes approximately 1.325 inches. A radius defined from the axis of chuck body  14  to any of pawls  86  and  94  in their positions as shown in  FIG. 4B  is approximately 0.651 inches, corresponding to a diameter of 1.302 inches. First and second pawls  86  and  94  thereby compress O-ring  140 , which, due to its resilience, responsively applies a radially outward force to the pawls. This radially outward force provides a secondary radially outward bias to the pawls that supplements the pawls&#39; inherent radially outward bias and increases the pawls&#39; tendency to remain seated in either of their two above-described positions during the power driver&#39;s operation. That is, O-ring  140  increases resistance to vibrational forces that may tend to push the pawls radially inward out of their respective grooves defined in the inner diameter of the sleeve, thereby inhibiting the chuck from opening or closing during use. 
     It will also be recognized that the increased radially outward bias increases the force necessary to be applied by the user in moving the sleeve between the locking mechanism&#39;s two operative positions. Thus, it should be understood that the materials and geometry of O-ring  140  may be selected to dampen vibrations in a power driver having a given power rating while still permitting effective manual operation by the user. For example, it is expected that a drill chuck as described above with respect to  FIGS. 6 through 8  (where O-ring  140  has a Shore A hardness from 60 to 80 and where outer race  78  is rotationally fixed to body  14  by tabs  80  received in grooves  82  in the thrust ring) will resist vibrations generated by a model GSB 18-2 RE 750 watt AC impact drill, manufactured by BOSCH Tool Corporation of Farmington Hills, Mich., such that the chuck does not undesirably open or over tighten. 
     In another preferred embodiment, groove  138  is formed into shoulder  130  in a square cross section, and O-ring  140  is formed in a correspondingly square cross section. The dimensions of the nut and O-ring otherwise remain the same. 
     It should also be understood that various materials may be used to construct O-ring  140 . For example, materials include various suitable elastomers such as acrylonitrile-butadiene (NBR, buna N, or nitrile rubber), chloroprene rubber (CR, or neoprene), polyacrilic rubber, silicone rubber, butyl rubber (ITR), styrene-butadiene (SBR, or buna S rubber), chlorosulfonated polyethelene (CSM, commercially available under the name HYPALON), or polysulfide rubber (T, or thiokol polymer) or thermoplastics such as suitable fluorocarbons (e.g. Teflon TFE or FEP), impact grade polystyrenes comprising polystyrene and rubber, and polyamide resins (nylon). O-rings made from commercially available materials such as the fluoroelastomers and perfluoroelastomers VITON, KALREZ, SIMRIZ, CHEMRAZ and AFLAS, and HYPALON (chlorosulfonated polyethylene), are available from Marco Rubber &amp; Plastic Products, Inc. of North Andover, Mass. 
     The shape of O-ring  140  may vary as desired. For example, O-ring  140  maybe molded into a shape that conforms at its inner diameter to the outer surface of shoulder  130  (with or without a groove  138 ) and that conforms at its outer circumference to the surfaces of pawls  86  and  94  that face the nut. The molded O-ring is preferably made by compression molding and can be formed from any of the above-described materials suitable for compression or injection molding. The O-ring can be molded as a separate component or can be molded directly around the nut. 
     To determine whether a given dampening structure, whether an O-ring of a selected material and geometry or any other selected resilient device, will sufficiently dampen vibrations for a given chuck configuration on a given driver, the structure may be assembled on a chuck and tested with the driver. Referring to the drill chuck as shown in  FIGS. 6 through 8 , for example, the chuck may be assembled and operated with a drill bit shank so that jaws  22  securely grip the tool shank. An alignment mark is then made axially along the outer surface of sleeve  18 , nose piece  20  and the tool shank so that the mark lies on the sleeve, nose piece and tool shank in a plane that includes the axis of chuck body  14 . The driver/chuck/bit is then operated to drill holes in selected materials, for example steel, concrete, diorite and wood. A hammer function may be applied while drilling in concrete and diorite. After each hole is drilled, or after each of a certain number of holes is drilled, the alignment of the marks on the sleeve, nose piece and bit is checked to determine whether the chuck has undesirably opened or over tightened. 
     The construction of the pawls and ratchet teeth contribute to the resistance of the locking mechanism to vibrations and, consequently, to the degree to which a supplemental outward bias is desirable. For example, the depth of pawl teeth  84  constructed as described above contributes to the effectiveness of the primary outward bias and, in a preferred embodiment as shown in  FIGS. 6 through 8 , is approximately 14/1000 inches. Further, pawls  86  and  94  are preferably constructed with sufficient stiffness so that when the inner and outer races are assembled together on the nut (but apart from the chuck body and jaws), and the nut and inner race are rotationally secured, at least an about 2 in-lb torque is required to ratchet pawl end  88  over teeth  84 , and in a preferred embodiment, the torque required is within a range of about 2 to about 3 in-lbs. In the example described below in which an about 0.7 gram layer of RTV sealant is disposed between the nut and the pawls, the torque required to ratchet the pawl over the ratchet teeth is within a range of about 4 in-lbs to 5 in-lbs. 
     It should also be understood that mechanisms other than O-rings may be used to apply additional bias to the pawls. In another preferred embodiment, for example, groove  138  in shoulder  130  may be omitted, so that shoulder  130  has a smooth surface as in  FIGS. 1 and 2 , and a spring band is received over the shoulder. The spring band is comprised of a central annular ring that may fit loosely over or be pressed to shoulder  130 . A number of spring arms extend outward from, and are biased radially away from, the central band. There is one spring arm for each pawl  86  and  94 , and a distal end of each spring arm engages its corresponding pawl to thereby apply a supplemental radially outward bias to the pawl. Particularly where the spring band&#39;s central ring fits loosely about the nut, the distal end of each spring arm may define tabs shaped correspondingly to tabs  96  and  98  (see  FIG. 3 ) so that the spring arm tabs are received in tabs  96  and  98  to thereby rotationally orient the spring band with respect to inner race  72 . 
     In a further preferred embodiment, shoulder  130  is again smooth, and O-ring  140  is replaced by a layer of silicone RTV (room-temperature vulcanized) rubber, for example 732 multi-purpose silicone RTV sealant made by Dow Corning Corporation and available from IDG Corporation of Belmont, N.C. The RTV sealant may be applied manually or automatically. For a construction as shown in  FIGS. 6 through 8 , in which six pawls  86  and  94  are used, six nozzles may be arranged in a pattern so that when the nozzles are brought to a position proximate shoulder  130 , the nozzles deposit dots of RTV sealant at positions on the shoulder corresponding to the opposing pawls. 
     In a preferred embodiment in which shoulder  130  defines a diameter of approximately 1.244 inches, a total of approximately 0.7 grams of RTV sealant is disposed on the shoulder. It should be understood, however, that the amount of RTV sealant may vary as desired, with the lower end of the desirable range being the point at which the RTV sealant fails to provide sufficient resilient force for a given chuck and driver, and the upper end of the desirable range being the point at which RTV sealant extends beyond an operative space between shoulder  130  and the pawls and thereby fails to contribute to the additional bias force. In the arrangement (with a smooth shoulder  130 ) as described above with respect to  FIGS. 1 and 2 , a range of 0.4 grams to 1.6 grams was found to be desirable. Using a chuck as in  FIGS. 6 through 8  with the method described above, a 0.7 gram layer of RTV sealant was found to dampen vibrations in a model GSB 18-2 RE 750 watt AC impact drill and a model GSB 20-2 RCE 1010 watt AC impact drill manufactured by BOSCH Tool Corporation of Farmington Hills, Mich. 
     While one or more preferred embodiments of the present 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. Thus, the depicted embodiments are presented by way of example only and are not intended as limitations on the present invention. It should be understood that aspects of the various one or more embodiments may be interchanged both in whole or in part. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may be fall within the literal or equivalent scope of the present disclosure.