Patent Document

CLAIM OF PRIORITY 
   The present application is a continuation of application Ser. No. 09/954,829, filed Sep. 12, 2001 now U.S. Pat. No.6,699,207, which is a continuation of application Ser. No. 09/570,427, filed May 12, 2000, now U.S. Pat. No. 6,296,257, which is a continuation of application Ser. No. 09/329,700, filed Jun. 10, 1999, now U.S. Pat. No. 6,286,842, which is a continuation of application Ser. No. 08/704,418, filed Aug. 20, 1996, now U.S. Pat. No. 5,924,702, which is a continuation of application Ser. No. 08/476,896, filed Jun. 7, 1995, now U.S. Pat. No. 5,573,254, which is a continuation of application Ser. No. 08/322,356, filed Oct. 13, 1994, now U.S. Pat. No. 5,452,906, which is a continuation of application 08/234,227, filed Apr. 28, 1994, now abandoned, which is a continuation of application 08/099,160, filed Jul. 29, 1993, now U.S. Pat. No. 5,330,204, which is a continuation of application Ser. No. 07/884,205, filed May 18, 1992, now U.S. Pat. No. 5,253,879, which is a division of application Ser. No. 07/449,722, filed Dec. 11, 1989, now U.S. Pat. No. 5,125,673, the entire disclosure of each hereby being incorporated by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to drill chucks for use with hand drills or with electric or pneumatic power drivers. More particularly, it relates to a chuck of the keyless type which may be tightened or loosened by hand or by actuation of the driver motor. 
   2. Prior Art 
   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 screw drivers, nut drivers, burrs, mounted grinding stones and other cutting or abrading tools. Since the tools may have shanks of varying diameter or the cross-section of the tool shank may be polygonal, the device is usually provided with a chuck which is adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore. 
   A wide variety of chucks has been developed by the art. In the simplest form of chuck, three jaws spaced circumferentially 120 degree apart from each other are constrained by a conical body threaded onto the drive shaft so that rotation of the body in one direction relative to the drive shaft forces the jaws into gripping relationship with respect to the cylindrical shank of a tool while rotation in the opposite direction releases the gripping relationship. Such a chuck may be keyless if the body is rotated by hand. However, because the tightening or loosening torque which may be applied directly in a hand operation is limited, the art developed the so-called three-jaw geared chuck. This design overcomes the principal problems in the earlier design by providing guideways in the chuck body to control more accurately the motion of the jaws and teeth on the jaws which mesh with a gear driven nut mounted on the chuck body. The gear is actuated by a pinion formed on a separate key which may be rotated in a bearing hole formed in the chuck body. 
   The three-jaw geared chuck is, or can be, a high quality precision tool which can exert a relatively large gripping force on the tool. However, the separate key may easily be misplaced or accidentally left in the chuck when the driver is actuated, thus possibly leading to some personal injury. In addition, the chucking or unchucking operation is a two-handed procedure which is time consuming. 
   To overcome these perceived disadvantages of the key operated gear chuck, various keyless chucks have now been developed. Such keyless chucks fall broadly into two classes: impact and non-impact chucks. Impact chucks employ means to apply a series of impacts to the nut so as to tighten or loosen the jaws. In the non-impact design, manual or mechanical means are used to restrain one member of the chuck while a torque is applied to another member of the chuck either manually or by the power driver to move the nut relative to the jaws. A keyless chuck of the impact type is disclosed in McCarthy U.S. Pat. No. 4,840,387 while the prior art cited therein illustrates keyless chucks both of the impact and the non-impact variety. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a keyless chuck of the non-impact type is provided. The invention employs an anti-friction bearing interposed between the nut and the body to decrease the friction losses in the mechanism so as to increase the effective tightening torque. The bearing thrust ring is formed separately from the body member and pressed thereon so as to increase the effective diameter of the body while minimizing the machining requirements. The principal load-bearing parts of the chuck, i.e., the jaws, body, nut, bearing and bearing race are formed from metal while the front and back sleeves and related parts may be formed from plastic materials so as to reduce the cost and permit customizing of the chuck. 
   Additional features of the invention include an elastomeric grip boot for the front sleeve which also functions as a bit holder and centering device, a one-way torque limiting clutch for limiting the tightening torque while permitting positive loosening torque, and a torque-limiting clutch which provides greater loosening torque than tightening torque. In accordance with a process feature of the invention, the three jaws are identical with respect to their nut engaging threads and the eccentricity of their engagement is overcome by a grinding procedure following assembly of the chuck. 

   
     DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings in which: 
       FIG. 1  is a perspective view of a keyless chuck in accordance with the present invention, 
       FIG. 2  is an enlarged longitudinal view, partly in section taken along line  2 — 2  of  FIG. 1 , 
       FIG. 3  is a transverse cross-sectional view taken along line  3 — 3  of  FIG. 2 , 
       FIG. 4  is an enlarged longitudinal view, partly in section, of an alternative form of the invention including a torque limiting mechanism and a bit retaining and centering device, 
       FIG. 5  is a transverse cross-sectional view taken along  5 — 5  of  FIG. 4  and showing the torque limiting mechanism, 
       FIG. 5A  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 5B  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 5C  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 5D  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 5E  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 5F  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 5G  is a fragmentary cross-sectional view showing an alternative form of the torque limiting mechanism, 
       FIG. 6A  is a plan view of a toothed retainer disc shown in  FIG. 4 , 
       FIG. 6B  is an edge view, of the retainer disc shown in  FIG. 6A , 
       FIG. 6C  is an edge view, partly in section, of an alternative form of the retainer disc having a beveled rim, 
       FIG. 6D  is a plan view of a toothless retainer disc having a beveled rim, 
       FIG. 6E  is an edge view, partly in section, of the retainer disc shown in  FIG. 6D , 
       FIG. 7  is an enlarged longitudinal view, partly in section, of a further alternative form of the invention which is particularly adapted for manual operation, 
       FIG. 8  is a fragmentary view taken along line  8 — 8  of  FIG. 7  and showing the clutch mechanism. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1 , there is illustrated a chuck  10  in accordance with the present invention. The chuck  10  includes a front sleeve member  12 , an optional rear sleeve member  14 , a body member  16  and jaws  18 . 
   As shown more clearly in  FIG. 2 , the body member  16  is generally cylindrical in shape and comprises a nose or forward section  20  and a tail or rearward section  22 . The nose section  20  is, preferably, chamfered at its outer end. An axial bore  24  is formed in the nose section  20  of the body member  16 . Axial bore  24  is somewhat larger than the largest tool shank which the chuck is designed to accommodate. A threaded bore  26  is formed in the tail section  22  of the body  16  and is of a standard size to mate with the threaded drive shaft of a powered or hand driver (not shown). The bores  24 ,  26  may communicate at the central region  28  of the body member  16 . If desired, the threaded bore  26  may be replaced by a tapered, unthreaded bore of a standard size to mate with a tapered drive shaft. 
   Passageways  30  are formed in the body member  16  to accommodate each jaw  18 . Preferably, three jaws  18  are employed and each jaw  18  is separated from the adjacent jaw by an arc of  120  degree. The axes of the passageways  30  and the jaws  18  are angled with respect to the chuck axis but intersect the chuck axis at a common point ahead of the chuck body  16 . Each jaw  18  has a tool engaging face  32  which is generally parallel to the axis of the chuck body  16  and threads  34  on its opposite or outer surface. In accordance with a feature of the present invention, the threads  34  have a relatively fine pitch, i.e., a pitch greater than 20 threads per inch, e.g., 32 threads per inch, and the threads, preferably, are of the buttress type though other thread forms may be employed. By employing the buttress thread form the tightening force applied to the jaw threads  34  is substantially axial to the jaw  18  so as to maximize the conversion of the tightening torque applied to the chuck into a gripping force applied to the tool shank. The use of a relatively fine pitch thread results in two advantages for the chuck in accordance with the present invention. First, the relatively fine pitch results in a greater mechanical advantage so that a given tightening torque is converted into a larger gripping force. Second, it becomes possible to use interchangeable jaws  18  of identical design rather than slightly different jaws that must be selected and assembled as a set. The small eccentricity which results from the use of identical jaw pieces in accordance with the present invention can be counteracted by a grinding step as more fully described below. 
   A circumferential groove  36  is formed in the body member  16  and extends into the passageways  30 . A split nut  38  having female threads  40  is located in the circumferential groove  36  and secured therein by the front sleeve member  12 . The split nut  38  is preferably formed with circumferential serrations or teeth  44  and the outer edges are provided with a small chamfer to facilitate press fitting of the split nut  38  into the bore  42  of the front sleeve  12 . Preferably, the front sleeve is formed from a structural plastic such as a polycarbonate, a filled polypropylene, e.g., glass-filled polypropylene, or a blend of structural plastic materials. The serrations or teeth on the split nut  38  assure that the front sleeve  12  will hold the split nut  38  securely without being subjected to an excessive hoop stress. 
   A circumferential race  46 , which may be grooved or a flat surface, is formed on the rear face of split nut  38  to accommodate an anti-friction bearing, for example, ball bearing assembly  48 . If desired, the bearing assembly  48  may include a bearing retainer  49  (see  FIG. 4 ) which locates the plurality of balls while permitting them to roll. A bearing thrust ring  50  is provided with a central hole  52  sized to be press fitted on the body member  16 . One face of the bearing thrust ring  50  has formed thereon a bearing race  54 , which may be grooved or flat, against which the bearing assembly  48  rides. A plurality of jaw guideways  56  are formed around the circumference of the central hole  52  in the thrust ring  50  to permit the retraction of the jaws  18  therethrough. The guideways are shaped to conform with the toothed area of the jaws  18  so as to reduce or prevent toggling of the jaws  18 . To perform this function, the axial length of the guideways  56  must be greater than the pitch of the threads  34  on the jaws  18 . The outer circumference of the bearing thrust ring  50  may have formed thereon serrations or teeth  58  and the outer edges may be chamfered so as to facilitate pressing of the bearing thrust ring  50  into a bore  60  formed in the rear sleeve member  14 . The rear sleeve member  14  also contains a bore  62  adapted to mate with the tail section  22  of the body member  16 . If desired, the rear sleeve member  14  may be omitted and the front, sleeve member  12  extended to the tail end of the body  16 . This alternative is feasible when a spindle lock is provided on the driver or when the driver is used to tighten or loosen the jaws. 
   The circumferential surface of the front sleeve member  12  may be knurled as suggested at  63  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 the rear sleeve member  14 , if employed, may be knurled or ribbed, if desired. 
   It will be appreciated that the rear sleeve member  14  is fixed to the body member  16  while the front sleeve member  12  is fixed to the split nut  38 . Thus, relative movement of the front and rear sleeve members  12 ,  14  will cause the jaws  18  to be advanced or retracted, depending upon the direction of the relative motion. As the bearing  48  is interposed between the relatively moving parts, the frictional losses are minimized and a maximum portion of the applied tightening torque is converted to a tightening force on the tool shank. While the chuck, of  FIGS. 2 and 3  may be operated manually, it may also be operated by the power driver. 
   As noted above, the jaws  18  are preferably formed so as to be identical to each other. In threejaw geared chucks, it is common practice to offset the threads proportional to the thread pitch so that when the jaws contact each other they will meet on the axis of the chuck. By making the jaws identical a degree of eccentricity will result but this is minimized by the fine pitch of the threads. In accordance with the present invention, a grinding procedure may be performed after the chuck is assembled to remove the eccentricity resulting from the small axial displacement of the jaws relative to each other. When the eccentricity is removed, the centering accuracy of the chuck will be the same as if custom sets of jaws had been provided. 
   Reference is now made to  FIGS. 4 and 5  which illustrate an alternative form of the present invention containing a torque limiting mechanism and a bit holding and centering device. Parts which are substantially the same as in the embodiment shown in  FIGS. 2 and 3  are identified by the same designators while modified parts are designated with the additional letter “a.” 
   In the embodiment shown in  FIGS. 4 and 5  a torque limiting mechanism is provided which produces an audible “click” when the chuck has attained its maximum tightness. This may be accomplished by providing a toothed annulus  64  having a bore  66  which engages the outside diameter of, or the teeth or serrations  44  on, the split nut  38  so as to lock the split nut  38  in place. A series of flexible teeth  68  are formed on the circumference of the annulus  64  which engage ribs  70  formed on the lateral surface of a bore  72  in the front sleeve member  12   a . As most clearly shown in  FIG. 5  the flexible teeth  68  have a sloping forward edge  68   a  which engages the ribs  70  during tightening of the chuck. When a predetermined tightening torque is reached, the ribs  70  pass over the flexible teeth  68  producing an audible “click.” However, when the front sleeve  12   a  is turned so as to loosen the chuck jaws  18 , the ribs  70  lock with the teeth  68  to transfer all the applied torque to the split nut  38 . 
   It will be noted that the front sleeve  12   a  extends beyond the nose  20  of the body member  16  to the region where the jaws  18  meet in their fully closed position. A grip boot  74  may be fastened to the front sleeve  12   a  by ribs  76 ,  78  and prevented from turning relative to the front sleeve  12   a  by longitudinal ribs (not shown). The grip boot  74  is preferably made from an elastomeric material such as natural or synthetic rubber and has a relatively small flexible orifice  80  aligned with the axis of the chuck body member  16 . Preferably, the grip boot  74  is made from a relatively soft material having a Shore A hardness of from 40 to 70. The orifice  80  is sized so that it will stretch to grip the shank of a drill or other tool inserted in the chuck and temporarily center and restrain the tool during chucking or unchucking operations. 
   In the embodiment of the invention shown in  FIGS. 2 and 3 , the front sleeve  12  is held in place because it is press fitted to the split nut  38 . In the embodiment shown in  FIGS. 4 and 5  other means are required to locate the front sleeve  12   a . A circumferential groove  82  is formed in the nose section  20  of the body member  16  to receive a retainer disc  84  which is pressed into the bore  72  of the front sleeve  12   a .  FIG. 6A  shows a plan view of the retainer disc  84  having circumferential teeth  86  and flexible engaging tabs  88  formed by a series of slots  90  stamped in the disc  84  around its center hole  92 . As shown in  FIG. 6B , the retainer disc  84  is flat and relatively thin so as to enable it to be pressed on to the body member  16  and turn freely in the groove  82 . The retainer disc  84  is sized so that the teeth  86  firmly grip the bore  72  of the front sleeve member  12   a .  FIG. 6C  illustrates an alternative form of a toothed retainer disc  84   c  having a beveled rim  94 .  FIG. 6D  shows a toothless retainer disc  84   d  in plan view. Like the toothed retainer disc  84 , the center hole  92  has slots  90  formed around its edge to define flexible engaging tabs  88 .  FIG. 6E  shows the beveled rim  96  which forms a deformable gripping member. 
   As noted above with reference to  FIG. 5 , the toothed annulus  64  performs two functions: first, it holds the split nut  38  in place, and, second, it forms one part of the torque limiting mechanism.  FIGS. 5A–5G  illustrate a number of alternative designs for the toothed annulus  64 . In  FIG. 5A  the annulus  64   a  is formed with a series of axial slots  98  located intermediate its inner and outer surfaces. A tooth  100  is located midway between the ends of each slot  98  which engages with the ribs or teeth  70  formed on the bore  72  of the front sleeve member  12   a . The slots  98  provide the flexibility required for the tooth action while still maintaining the strength of annulus. In  FIGS. 5B–5G  further variations are shown in the design of the annulus. In  FIG. 5B  the annulus  64   b  is provided with a series of open slots  102  which result in a series of pawls  104  having a tooth  106  at the end thereof which engages the teeth  70   b  on the bore  72  of the front sleeve  12   a . In  FIG. 5B  the tooth  106  has a square profile so that limited torque is transmitted when the sleeve  12   a  is rotated in a clockwise direction relative to the body  16  as viewed in  FIG. 5B  but unlimited torque is transmitted with counterclockwise rotation. This difference is due to the asymmetrical shape of the tooth  70   b .  FIG. 5C  is similar to  FIG. 5B  except that the tooth  108  has a round rather than a square shape and the rear face of the tooth  70   c  has correlative shape.  FIG. 5D  is likewise similar to  FIG. 5B  except that the tooth  110  has a triangular rather than a square shape and the tooth  70   d  has a correlative asymmetric shape. 
     FIGS. 5E–5G  show modifications of the structures respectively shown in  FIGS. 5B–5D . In these modifications the tooth  70   e ,  70   f , or  70   g  is designed to be substantially symmetrical about a radius of the front sleeve  12   a  so that the tightening torque and the loosening torque are substantially equal. It will be understood that the torque transmitted through the mechanism is principally a function of the angle of the surface of the teeth  70  and  68 ,  100 ,  106 ,  108  or  110 , the coefficient of friction between the teeth, the force required to depress or deform the teeth  68 ,  100 ,  106 ,  108  or  110 , and the number of teeth in contact. The torque increases as the tooth surface approaches a radius of the front sleeve, as the coefficient of friction increases, as the stiffness of the teeth on the annulus  64  increases, and as the number of teeth in contact increases. By appropriately controlling these variables, the desired tightening and loosening torque may be predetermined. 
   Reference is now made to  FIGS. 7 and 8  which show an embodiment of the present invention which is particularly adapted for manual operation. Again, parts which are substantially the same as in the earlier embodiments bear the same designations while modified parts are designated by “a” or “b.” The embodiment of  FIG. 7  is characterized by the location of the torque limiting mechanism in the rear sleeve member  14   a . The basic structure of the body member  16 , the jaws  18 , and the split nut member  38  upon which the front sleeve member  12   b  is pressed is similar to that shown in  FIG. 2  except that a grip boot  74   a  is applied to the surface of the front sleeve member  12   b  to enhance the grippability of the sleeve member. Grip boot  74   a  does not provide the tool holding feature shown in  FIG. 4  but it is apparent that this feature could be added, if desired. The arrangement of bearing  48  and bearing thrust ring  50   a  is also similar to that shown in  FIGS. 2 and 4  except that no serrations or teeth are formed on the outer periphery of the bearing thrust ring  50   a . In the embodiment of  FIG. 7 , the bore  60   a  is sized for a sliding fit with the bearing thrust ring  50   a  and accommodates a Belleville or other form of compression spring  112  which biases the rear sleeve member  14   a  toward a back plate  114  which is press fitted onto the tail section  22  of the body member  16 . As shown in  FIG. 8 , the back plate  114  may be provided with a plurality of teeth  116  and the rear sleeve member  14   a  provided with a plurality of radial ribs  118 . It will be appreciated that during a chucking operation the rear sleeve  14   a  will be held while the front sleeve  12   b  is turned in a clockwise direction as viewed from the jaw end of the chuck. At a predetermined torque, the ribs  118  will ride over the teeth  116  while the rear sleeve  14   a  is displaced in a forward direction against the bias of the spring  112 . The teeth  116  on the back plate  114  are designed to produce a limited tightening torque and an unlimited loosening torque. By varying the angle of the teeth faces and the spring rate of the compression spring  112  the tightening and loosening torque may be varied as desired and as explained above. Of course, the teeth  116  and the ribs  118  may be interchanged, if desired, and various shapes of teeth may be employed as suggested in  FIGS. 5–5G . 
   The chuck in accordance with the present invention has a number of advantages with respect to the ease and cost of manufacture. The body member  16  may be machined from a relatively small diameter bar since the bearing thrust ring  50  is made separately and then pressed onto the body member. This reduces the machining costs for the body member. Certain parts, such as the split nut and bearing thrust ring may be formed from powdered metal or stamped or otherwise cold formed with limited machining steps. With this design of the load-bearing parts, the more massive front and rear sleeves may be formed from structural plastic materials thereby reducing weight and manufacturing costs while providing the ability to customize the chuck through the use of colors, rib shapes, knurling, or identification logos. 
   The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

Technology Category: 4