Abstract:
A tool-bit holder for receiving a tool-bit that automatically captures the tool-bit as it is inserted into the holder with a quick release mechanism to prevent axial withdrawal of the tool-bit from the holder. The tool-bit includes a shank portion with a circumferential groove. The tool-bit holder also includes a hub having a longitudinal bore for receiving the shank and a radial bore partially housing a detent ball used to capture the tool-bit shank at its circumferential groove within the tool-bit holder. A sleeve is axially slidably mounted relative to the hub and has a radial bore in communication with the radial bore of the hub for reception of the detent ball. The sleeve is axially biased by a spring and forces the detent ball against and along an inner ramp face fixed relative to the hub. The inner ramp face forces the detent ball radially inwardly and through the radial bore to seat in the circumferential groove of the tool-bit shank. Attempted axial extraction of the tool-bit from the longitudinal bore without releasing the detent ball locks the ball against the inner ramp face and prevents extraction of the tool-bit. The tool-bit is released when the bias force of the spring is relieved or countered by axially sliding the sleeve relative to the hub, so that the tool-bit can then be withdrawn from the hub.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority from provisional application No. 60/166,281 filed Nov. 18, 1999 for “Self-Locking Chuck Mechanism” by James L. Wienhold and from provisional application No. 60/225,350 filed Aug. 15, 2000 for “Self-Locking Chuck Mechanism” by James L. Wienhold. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to tool-bit holders. Specifically, the present invention relates to a tool-bit holder that automatically captures tool-bits as they are inserted into the holder. 
     In many situations, an operator must frequently change tools while working on a particular project. Often the operator is in a position where quickly exchanging one tool-bit for another is awkward. In order to change tool-bits held within existing tool-bit holders, an operator must manipulate a tool-bit locking mechanism. For example, to change tools held by a conventional three-jaw chuck, the operator must loosen the jaws to remove or insert a tool-bit, and tighten the jaws to secure a tool-bit. This usually requires the operator to use both hands to perform an exchange. Because of the awkwardness inherent in exchanging tools in such tool-bit holders, the operator&#39;s work is slowed. 
     In some situations an operator may not be able to access the securing or releasing mechanism of the tool-bit holder. For example, such mechanisms are inserted into a handle, such as a screw driver handle, such that to directly activate a sleeve or other mechanism for securing or releasing the tool-bit may be impossible. These situations require that a tool-bit be automatically secured or released by the tool-bit holder as the tool-bit is inserted or pulled out of the tool-bit holder. 
     Several devices have been designed to reduce the awkwardness inherent in exchanging tools in a tool-bit holder. However, all require some degree of manipulation of the tool-bit holder to secure and release a tool-bit shank. As a result, an automatic tool-bit holder in which a tool-bit shank may be inserted and secured without additional manipulation of a locking or releasing device would be highly desirable. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is a tool-bit holder for a tool-bit that automatically captures a shank of the tool-bit as the shank is inserted into the holder and prevents axial retraction of the tool-bit while the holder is in a locking position. 
     The automatic tool-bit holder of the present invention includes a hub having a longitudinal bore for inserting and capturing the shank. The hub includes a radial bore through which a detent ball may intrude into the longitudinal bore and seat into a circumferential groove in the shank of the tool-bit. The radial bore has a width smaller than the diameter of the detent ball to prevent the detent ball from falling radially into the longitudinal bore of the hub. 
     A spring or the like, axially biases a sleeve to force the detent ball in contact with an inner ramp face. Preferably, sleeve lies at least partially within a fixed collar disposed annularly about the hub. As the detent ball is forced into contact with the inner ramp face, the detent ball is directed radially inwardly along the inner ramp face and through the radial bore into the hub to contact the shank, and ultimately to seat in the groove to capture the tool-bit. The tool-bit is released when the bias force is relieved or countered, by axially sliding the sleeve relative to the hub. 
     In one alternative embodiment of the present invention, the sleeve is slidable within the longitudinal bore, eliminating the need for a fixed collar. The sleeve has an opening axially aligned with the radial bore to carry the detent ball. A compressed spring disposed between the sleeve and a closed end of the longitudinal bore provides the axial bias force pressing the detent ball in contact with an inner ramp face of the radial bore. As the detent ball is forced into contact with the inner ramp face, the detent ball is directed radially inwardly along the inner ramp face and through the opening in the sleeve to contact the shank, and ultimately to seat in the groove to capture the tool-bit. The tool-bit is released when the bias force is relieved or countered, by axially sliding the sleeve relative to the hub. 
     The present invention may also be defined in relation to a tool-bit holder of the type which has a hub a detent ball, a sleeve and a spring. The hub has a longitudinal bore formed for axially receiving a tool-bit shank therein, such that the longitudinal bore has an open end and a terminating face. The hub also has a radial bore therethrough. The detent ball is radially movably disposed in the radial bore of the hub for selected engagement with a circumferential groove on the tool-bit shank. The sleeve is axially slidably mounted relative to the hub or engaging the detent ball and the spring biases the sleeve into engagement with the detent ball. The present invention includes a radial bore in the sleeve that communicates with the radial bore of the hub for receiving the detent ball. In addition, the invention includes a longitudinally extending inner ramp face that is fixed relative to the hub for engaging the detent ball. The inner ramp face is opposed to the bias of the spring such that the inner ramp face extends radially outwardly toward the terminating face of the longitudinal bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a tool-bit shank prior to full insertion into a first embodiment of an automatic tool-bit holder of the present invention, with the tool-bit holder in an unloading position. 
     FIG. 2 is a sectional view as taken along lines  2 — 2  in FIG. 1, showing only the hub and detent ball of the tool-bit holder of the first embodiment. 
     FIG. 3 is a plan view of the hub of the automatic tool-bit holder of the first embodiment, as seen along the plane defined by lines  3 — 3  in FIG.  1 . 
     FIG. 4 is a sectional view of the tool-bit shank being inserted or released from the first embodiment of the tool-bit holder, with the tool-bit holder in a loading position. 
     FIG. 5 is a sectional view of the tool-bit shank being captured by the tool-bit holder of the first embodiment, with the tool-bit holder in a locking position. 
     FIG. 6 is a sectional view of the tool-bit shank being released from the tool-bit holder of the first embodiment, with the tool-bit holder in a retracting position. 
     FIG. 7 is a sectional view of a tool-bit shank prior to full insertion into a second embodiment of an automatic tool-bit holder of the present invention, the tool-bit holder is in an unloading position. 
     FIG. 8 is a sectional as taken along lines  8 — 8  in FIG. 7 showing only the hub and detent ball of the tool-bit holder of the second embodiment. 
     FIG. 9 is a plan view of a hub of the tool-bit holder of the second embodiment, as seen along the plane defined by lines  9 — 9  in FIG.  7 . 
     FIG. 10 is a sectional view of the tool-bit shank being inserted or released from the second embodiment of the tool-bit holder, with the tool-bit holder in a loading position. 
     FIG. 11 is a sectional view of the tool-bit shank being captured by the tool-bit holder of the second embodiment, with the tool-bit holder in a locking position. 
     FIG. 12 is a sectional view of the tool-bit shank being released from the tool-bit holder of the second embodiment, with the tool-bit holder in a retracting position. 
    
    
     While the above-identified drawing figures set forth two preferred embodiments of the invention, this disclosure is intended to present the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which follow the scope and spirit of the principles of this invention. 
     DETAILED DESCRIPTION 
     The present invention is a tool-bit holder for automatically capturing and retaining a tool-bit. A first embodiment of an automatic tool-bit holder is shown in FIG.  1 . The tool-bit holder  10  includes a hub  12 , a collar  14 , a sleeve  16 , a detent ball  18  and a spring  20 . 
     The hub  12  has a forward distal end  22 , ending in a forward face  26 , and a rear proximal end  24 . Preferably, the proximal end  24  of the hub  12  is shaped to provide a connection to a chuck for a power tool. Alternatively, the proximal end  24  provides a connection to other devices such as tools used for drilling and driving. The proximal end  24  typically has a hexagonally-shaped cross-section. A longitudinal bore  28 , preferably hexagonally-shaped, extends perpendicularly into the forward face  26  and axially toward the proximal end  24  of the hub  12 . The longitudinal bore  28  has an open end  29  and terminates in the hub  12  at a terminating face  30 . The longitudinal bore  28  is substantially aligned along the longitudinal axis of the hub  12  and is shaped to admit the shank of a standard quick release tool-bit  32 . Preferably, the terminating face  30  is substantially perpendicular to the longitudinal axis of the hub  12 , although a person skilled in the art would realize that the terminating face  30  may have a concavity due to the boring process. The hub  12  has a radial bore  34  located along the longitudinal axis of the hub  12  and the radial bore  34  is preferably aligned to extend substantially perpendicular to the longitudinal axis of the hub  12 . The radial bore  34  extends completely through the hub  12  such that the radial bore  34  communicates with the longitudinal bore  28 . 
     As is typical, the tool-bit  32  includes a hexagonally-shaped shank  36 . The shank  36  includes a circumferential groove  38  near the rear end of the shank  36 . The circumferential groove  38  includes three distinct profiles, including a radially inwardly extending rear radiused shoulder  40 , a centered flat portion  42  and a radially inwardly extending forward radiused shoulder  44 . The shank  36  has a rear face  45 . When the shank  36  is completely admitted in the hub  12 , the rear face  45  of the shank  36  rests against the terminating face  30  of the longitudinal bore  28 . 
     The collar  14  is fixedly attached to the hub  12  forward of the radial bore  34  adjacent the open end  29  of the longitudinal bore  28  and is disposed annularly about the hub  12 . The collar  14  has a forward face  46  at the distal end  22  of hub  12  extending radially outwardly from the longitudinal axis of the hub  12  and preferably forms one continuous plane with the forward face  26  of the hub  12 . The collar  14  also has a proximal end  48 . The proximal end  48  is preferably ramped up from the collar  14  (radially away and rearwardly), although a person skilled in the art would realize that the proximal end  48  could be stepped up (out and away) from the collar  14  as well. The proximal end  48  of the collar  14  forms a channel  50  that lies substantially proximate to the radial bore  34  of the hub  12 . The proximal end  48  has a longitudinal face  52  forming one wall of the channel  50  and an inner ramp face  54  forming another wall of the channel  50 . The inner ramp face  54  preferably extends radially outwardly and axially rearwardly from the longitudinal axis of the hub  12 . A person skilled in the art would realize that additional faces may be used to form the walls of the channel  50  and that such faces may have various angular orientations. 
     The sleeve  16  is slidably mounted along the hub  12  substantially rearward of the radial bore  34 . The sleeve  16  is disposed annularly about the hub  12 . Preferably the sleeve  16  is keyed to the hub  12  due to the detent ball  18  to prevent relative rotation between the hub  12  and the sleeve  16 . An optional external outer sleeve may be installed over sleeve  16  to allow free rotation of an operator grasping area relative to hub  12 . The sleeve  16  lies at least partially within the channel  50  of the collar  16  such that the sleeve  16  axially slides along the hub  12  and within the channel  50 . The sleeve  16  has a radial bore  56  in communication with the radial bore  34  of the hub  12 . 
     The detent ball  18  is disposed within the radial bore  56  of the sleeve  16  and the radial bore  34  of the hub  12 , which are circumferentially aligned. The longitudinal face  52  on the proximal end  48  of the collar  14  prevents the detent ball  18  from leaving its position within the channel.  50  and completely falling radially out of the tool-bit holder  10 . As can be seen by FIG. 2, the diameter  58  of the detent ball  18  is greater than the width  60  of the radial bore  34  of the hub  12  (at its radially inner end), thereby preventing the detent ball  18  from completely falling radially into the longitudinal bore  28 . FIG. 3 is a plan view of the hub  12 , and also illustrates the location of the radial bore  56  of the sleeve  16  relative to the radial bore  34  of the hub  12 . The radial bore  56  of the sleeve  16  is circular and the radial bore  34  of the hub  12  is elongated longitudinally. 
     The spring  20  is disposed between a shoulder  61  of the sleeve  16  and a washer  62 . The spring  20  is of the compression spring type, such that the spring  20  biases the sleeve  16  axially toward the open end  29  of the longitudinal bore  28 . A retaining clip  64  prevents the washer  62  from moving toward the proximal end  24  of the hub  12 . When the sleeve  16  is urged towards the open end  29  of the longitudinal bore  28 , the detent ball  18  in the radial bore  56  of the sleeve  16  opposes the bias of the spring  20  and engages the inner ramp face  54 . The inner ramp face  54  extends radially outwardly and toward the terminating face  30  of the longitudinal bore  28 . The sleeve  16  is slidably positionable along the hub  12  between a locking position and a retracting position (or a tool-bit loading position and unloading position). When the sleeve  16  is in the locking position (FIG.  5 ), the spring  20  is less compressed than when the sleeve  16  is in the retracting position (FIG.  6 ), and when the sleeve  16  is in the loading position (FIG.  4 ), the spring  20  is less compressed than when the sleeve  16  is in the unloading position (FIG.  1 ). 
     FIG. 1 illustrates a sectional view of the tool-bit holder  10  while it is in the unloading position prior to full insertion of tool-bit shank  36  into the longitudinal bore  28 . The tool-bit holder  10  stays in the unloading position until the shank  36  comes in contact with the detent ball  18  as it enters the longitudinal bore  28  (as shown in FIG.  4 ). While the tool-bit holder  10  is in the unloading position, the spring  20  urges the sleeve  16  axially towards the distal end  22  of the hub  12 . The detent ball  18  rides along with the sleeve  16  in the radial bores  34 ,  56 . The detent ball  18  is urged radially inwardly along the inner ramp face  54  until it can go no further and stops the sleeve  16  from further axially forward movement along the hub  12 . The detent ball  18  is prevented from completely falling radially into the longitudinal bore  28  by the radial bore  34  of the hub  12  (as can be seen in FIG. 2) because the diameter  58  of the detent ball  18  is greater than the width  60  of the radial bore  34  (at its radially innermost end). 
     FIG. 4 illustrates a sectional view of the tool-bit holder  10  in the loading position as the shank  36  of the tool-bit  32  is directed through the longitudinal bore  28  towards the terminating face  30 . The shank  36  comes in contact with the detent ball  18  and urges the detent ball  18  radially outwardly against the inner ramp face  54 . This in turn forces the sleeve  16  to slide axially rearward (in direction of arrow  65 ) towards the proximal end  24  of the hub  12 , at least until the detent ball  18  contacts the radial bore  34 . The detent ball  18  rides in the radial bore  56  of the sleeve  16  along the shank  36  (the radial bore  56  is circular, as seen in FIG.  3 ). The spring  20  compresses as the sleeve  16  slides axially rearward toward the proximal end  24 . 
     FIG. 5 shows a sectional view of the tool-bit holder  10  in the locking position. As the shank  36  of the tool-bit  32  moves into the longitudinal bore  28 , the circumferential groove  38  of the shank  36  becomes axially aligned with the radial bore  34  of the hub  12  and the detent ball  18 . The shank  36  stops its progression into the longitudinal bore  28  when the rear face  45  of the shank  36  contacts the terminating face  30  of the longitudinal bore  28 . When the circumferential groove  38  is axially aligned with the detent ball  18 , the detent ball  18  can no longer ride along the shank  36  and the spring  20  urges the sleeve  16  axially forward (in direction of arrow  67 ) along the hub  12  towards the distal end  22  of the hub  12 . The axially forward movement of the sleeve  16  forces the detent ball  18  (riding in the radial bore  56  of the sleeve  16 ) radially inwardly along the inner ramp face  54  of the collar  14 . The inner ramp face  54  urges the detent ball  18  radially inwardly through the radial bore  34  of the hub  12  and forces the detent ball  18  to seat in the circumferential groove  38  of the shank  36 . The detent ball  18  sits on the radially, inwardly extending rear radiused shoulder  40  of the circumferential groove  38 . The spring  20  urges the sleeve  16  axially forward towards the distal end  22  of the hub  12  (in direction of arrow  67 ). The detent ball  18  is stopped by the inner ramp face  54  of the collar  14  such that the sleeve  16  is prevented from moving axially forward along the hub  12  beyond the locking position (FIG.  5 ). 
     In the locking position, the tool-bit  32  is locked into the tool-bit holder  10  and cannot be pulled from the tool-bit holder  10 . When an attempt to remove the tool-bit  32  from the hub  12  is made by pulling the shank  36  along its longitudinal axis towards the distal end  22  of the hub  12 , the rear radiused shoulder  40  of the circumferential groove  38  forces the detent ball  18  against the inner ramp face  54  of the collar  14 . The inner ramp face  54  prevents the detent ball  18  from radially outwardly moving out of the circumferential groove  38 . The detent ball  18  remains seated in the circumferential groove  38  and does not allow the shank  36  to be removed from the longitudinal bore  28 . 
     FIG. 6 shows a sectional view of the tool-bit holder  10  with the sleeve  16  in the retracting position, thereby allowing removal of the tool-bit  32  from the longitudinal bore  28 . The sleeve  16  is moved axially rearwardly (in direction of arrow  65 ) along the hub  12  toward the proximal end  24  of the hub  12  and against the bias force of the spring  20 , thereby compressing the spring  20 . Movement of the sleeve  16  is generally performed by the tool operator. As the sleeve  16  is moved axially rearwardly along the hub  12 , the detent ball  18  riding in the radial bore  56  of the sleeve  16  is urged radially outwardly along the inner ramp face  54 , removing the detent ball  18  from its seat in the circumferential groove  38 . Once the detent ball  18  is removed from the circumferential groove  38 , the shank  36  of the tool-bit  32  is free to be released from the longitudinal bore  28 . The tool-bit  32  is removed by pulling the shank  36  longitudinally toward the distal end  22  of the hub  12 , thereby releasing the tool-bit  32  from the tool-bit holder  10 . 
     A second embodiment of an inventive automatic tool-bit holder  70  is shown in FIGS. 7-12. The second embodiment is particularly adapted to be inserted into a tool handle  72 , such as a screwdriver handle. When inserted into the handle  72  a large portion of the tool-bit holder  70  is inaccessible, requiring a tool-bit catch and release mechanism that operates with limited access. The tool-bit holder  70  includes a hub  74 , a sleeve  76 , a detent ball  78  and a spring  80 . 
     The hub  74  has a forward distal end  82  and a rear proximal end  84 . The distal end  82  ends in a forward face  86  that is generally perpendicular to the longitudinal axis of the hub  74 . A longitudinal bore  88 , preferably cylindrically shaped but alternatively hexagonally-shaped, extends perpendicularly into the forward face  86  and axially toward the proximal end  84  of the hub,  74 . The longitudinal bore  88  has an open end  89  and terminates in the hub  74  at a terminating face  90 . The longitudinal bore  88  is substantially aligned along the longitudinal axis of the hub  74  and is shaped to admit a standard quick release tool-bit  92 . Preferably, the terminating face  90  is substantially perpendicular to the longitudinal axis of the hub  74 , although a person skilled in the art would realize the terminating face  90  may have a concavity due to the boring process. 
     The hub  74  has a radial bore  94  preferably extending radially outwardly and axially rearwardly of the longitudinal axis of the hub  74 . The radial bore  94  is located along the longitudinal axis of the hub  74 . The radial bore  94  extends completely through the hub  74  such that the radial bore  94  communicates with the longitudinal bore  88 . The radial bore  94  has an inner ramp face  96  and a second inner face  98  substantially parallel to the inner ramp face  96 . The width of the radial bore  94  is sufficient to allow the detent ball  78  to move into and out of the radial bore  94 . A person skilled in the art would realize that additional faces may be used to form the walls for the radial bore  94  and that the faces may have varying angular orientations. The inner ramp face  96  may alternatively be provided as a circumferential recess within the hub  74 . 
     A longitudinal face  99  on the handle  72  into which automatic tool-bit holder  70  is inserted prevents the detent ball  78  from completely falling radially out of the tool-bit holder  70  (the longitudinal face  99  of the handle  72  provides a cover over the radial outward end of the radial bore  94  in the hub  74 ). Preferably, an inner face of the handle  72  or an outer face of the hub  74  (or both) is knurled to create a secure fit between the handle  72  and the tool-bit holder  70 . Alternatively, the handle  72  and the hub  74  are keyed or held together for coupled rotation by a detent ball mechanism or other suitable connecting means. In applications where the tool-bit holder  70  is not inserted into a handle, a plug or external sleeve (not shown) covers the radial bore  94  of the hub  74  (to define the longitudinal face  99 ) in order to prevent the detent ball  78  from falling radially out of the tool-bit holder  70 . 
     A tool-bit used in the embodiment may take the same form as the previously described tool-bit. Typically, the tool-bit  92  includes a hexagonally-shaped shank  100 . The shank  100  includes a circumferential groove  102  near the rear end of the shank  100 . The circumferential groove  102  includes three distinct surface profiles, including a radially inwardly extending rear radiused shoulder  104 , a centered flat portion  106  and a radially inwardly extending forward radiused shoulder  108 . The shank  100  has a rear face  110 . When the shank  100  is completely admitted into the hub  74 , the rear face  110  of the shank  100  rests against the terminating face  90  of the longitudinal bore  88 . 
     The sleeve  76  is slidably mounted along the hub  74  and disposed annularly within the longitudinal bore  88  of the hub  74 . Preferably, the sleeve  76  is keyed to the hub  74  to prevent relative rotation between the hub  74  and the sleeve  76 . The sleeve  76  has a radial bore  112  in communication with the radial bore  94  of the hub  74 . The sleeve  76  has a distal portion  116  that extends beyond the open end  89  of the longitudinal bore  88 . The distal portion  116  has a radially extending flange  114 . Preferably, the flange  114  extends approximately 90° perpendicular and outward from a distal portion  116  of the sleeve  76 . The flange  114  engages the forward face  86  of the hub  74  while in the loading and retracting positions. A person skilled in the art would realize the while an annular flange would suffice for this purpose, the flange  114  is optional and may vary in size and configuration for preferred operator finger contact area, such as one or more radially projecting tabs. 
     The detent ball  78  is disposed in the radial bore  112  of the sleeve  76  and the radial bore  94  of the hub  74 . The longitudinal face  99  on the handle  72  prevents the detent ball  78  from leaving its position within the radial bore  94  and completely falling radially out of the tool-bit holder  70 . As can be seen by FIG. 8, the diameter  118  of the detent ball  78  is greater than the width  120  of the radial bore  112  of the sleeve  76  (at its radially inner end), thereby preventing the detent ball  78  from completely falling radially into the longitudinal bore  88 . FIG. 9 illustrates the location of the detent ball  78  as it rides in the sleeve  76  along the hub  74  relative to the radial bore  94 . 
     The spring  80  is disposed between the terminating face  90  of the longitudinal bore  88  and a radial surface  122  of the sleeve  76 . Preferably, the spring  80  engages to the radial surface  122  and extends within a channel  124  of the sleeve  76 . The spring  80  is of the compression spring-type, such that the spring  80  urges the sleeve  76  axially toward the open end  89  of the longitudinal bore  88 . When the sleeve  76  is urged towards the open end  89  of the longitudinal bore  88 , the detent ball  78  in the radial bore  112  of sleeve  76  opposes the bias of the spring  80  and engages the inner ramp face  96 . The inner ramp face  96  extends radially outwardly and toward the terminating face  90  of the longitudinal bore  88 . The sleeve  76  is slidably positionable along the hub  74  between a locking position and a retracting position (or a tool-bit loading position and unloading position). When the sleeve  76  is in the locking position (FIG.  11 ), the spring  80  is less compressed than when the sleeve  76  is in the retracting position (FIG.  12 ), and when the sleeve  76  is in the loading position (FIG.  10 ), the spring  80  is more compressed than when the sleeve  76  is in the unloading position (FIG.  7 ). 
     FIG. 7 illustrates a sectional view of the tool-bit holder  70  while it is in the unloading position prior to full insertion of the shank  100  into the longitudinal bore  88 . The tool-bit holder  70  stays in the unloading position until the shank  100  comes in contact with the detent ball  78  as it enters the longitudinal bore  88  (as shown in FIG.  10 ). While the tool-bit holder  70  is in the unloading position, the spring  80  urges the sleeve  76  axially forward towards the distal end  82  of the hub  74 . The detent ball  78  rides in the radial bores  96 ,  112  along with the sleeve  76  as it moves axially forward. The detent ball  78  is urged radially inwardly along the inner ramp face  96  until the inner ramp face  96  stops the detent ball  78  and prevents the sleeve  76  from further axial forward movement along the hub  74 . The detent ball  78  is prevented from completely falling radially into the longitudinal bore  88  by the radial bore  94  of the hub  74  (as can be seen in FIG. 8) because the diameter  118  of the detent ball  78  is greater than the width  120  of the radial bore  94  (at its radially inner end). 
     FIG. 10 illustrates a sectional view of the tool-bit holder  70  in the loading position as the shank  100  of the tool-bit  92  is directed through the longitudinal bore  88  toward the terminating face  90 . The shank  100  comes in contact with the detent ball  78  urging the detent ball  78  out of the longitudinal bore  88  and forcing the sleeve  76  to slide axially rearward (in direction of arrow  125 ) toward the proximal end  84  of the hub  74  (sleeve  76  will move axially rearward until the detent ball  78  retreats radially outwardly into the radial bore  94  far enough to clear shank  100 ). The detent ball  78  rides in the radial bore  112  of the sleeve  76  along the shank  100 , and as the sleeve  76  slides rearwardly, shank  100  urges the detent ball  78  radially outwardly against the inner ramp face  96  of the hub  74 . The spring  80  compresses as the sleeve  76  slides axially rearward toward the proximal end  84  of the hub  74 . 
     FIG. 11 shows a sectional view of the tool-bit holder  70  in the locking position. As the shank  100  of the tool-bit  92  moves into the longitudinal bore  88 , the circumferential groove  102  of the shank  100  is axially aligned with the radial bore  94  of the hub  74  and the detent ball  78 . The shank  100  stops its movement into the longitudinal bore  88  when the rear face  110  of the shank  100  contacts the terminating face  90  of the longitudinal bore  88 . When the circumferential groove  102  is axially aligned with the detent ball  78 , the spring  80  urges the sleeve  76  axially forward (in direction of arrow  127 ) along the hub  74  toward the distal end  82  of the hub  74 . The axially forward movement of the sleeve  76  forces the detent ball (riding in the radial bore  112  of the sleeve  76 ) radially inwardly along the inner ramp face  96  of the hub  74  (in direction of arrow  127 ). The inner ramp face  96  urges the detent ball  78  radially inwardly through the radial bore  112  of sleeve  76  forcing the detent ball  78  to seat in the circumferential groove  102  of the shank  100 . The detent ball  78  sits substantially on the radially inwardly extending rear radiused shoulder  104  of the circumferential groove  102 . The spring  80  continues to urge the sleeve  76  axially forward toward the distal end  82  of the hub  74 . The detent ball  78  riding in the radial bore  112  of the sleeve  76  is stopped by inner ramp face  96  of the hub  74  such that the sleeve  76  is prevented from further axially forward movement along the hub  74 . 
     In the locking position, the tool-bit  92  is locked into the tool-bit holder  70  and cannot be pulled from the tool-bit holder  70 . When an attempt is made to remove the tool-bit  92  from the hub  74  by pulling the shank  100  along the longitudinal axis towards the distal end  82  of the hub  74 , the rear radiused shoulder  104  of the circumferential groove  102  forces the detent ball  78  against the inner ramp face  96  of the hub  74 . The inner ramp face  96  prevents the detent ball  78  from moving radially outwardly from the circumferential groove  102  and thereby prevents the shank  100  from being removed from the longitudinal bore  88 . 
     FIG. 12 shows a sectional view of the tool-bit holder  70  with the sleeve  76  in the retracting position, thereby allowing the removal of the tool-bit  92  from the longitudinal bore  88 . The sleeve  76  is moved axially rearwardly (in direction of arrow  125 ) along the hub  74  toward the proximal end  84  of the hub  74  and against the bias force of the spring  80 , thereby compressing the spring  80 . Movement of the sleeve  76  is generally performed by the tool operator by pushing on the flange  114  of the distal portion  116  of the sleeve  76  towards the proximal end  84  of the hub  74 . As the sleeve  76  is moved axially rearwardly along the hub  74 , the detent ball  78  is urged radially outwardly along the inner ramp face  96 , thereby removing the detent ball  78  from its seat in the circumferential groove  102 . Once the detent ball  78  is removed from the circumferential groove  102 , the shank  100  of the tool-bit  92  is free to be released from the longitudinal bore  88 . The tool-bit  92  is removed by pulling the shank  100  along the longitudinal axis toward the distal end  82  of the hub  74 , thereby releasing the tool-bit  92  from the tool-bit holder  70 . 
     Preferably, the components in both embodiments are formed of a metal material such as steel or aluminum. However, the parts of the automatic tool-bit holder may be formed of other materials, such as polymeric or polymeric composites, ceramics or ceramic composites. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, an elastomeric body may provide the bias force instead of a spring. In addition, the spring may be a leaf spring or a washer rather than a coil spring as shown in the FIGS. Also, the cross-sectional shape of the longitudinal bore may be square, triangular, other polygonal shapes that fit tool-bits having various cross-sectional shapes. Further, the longitudinal bore may have various polygonal cross-sectional shapes to prevent relative rotation between the tool-bit and the longitudinal bore.