Patent Publication Number: US-2022226973-A1

Title: Multi-size tool bit holder for a rotary power tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 17/277,782, filed Mar. 19, 2021, issued as U.S. Pat. No. 11,292,109, which is a national phase filing under 35 U.S.C. 371 of International Application No. PCT/US2019/055712, filed on Oct. 10, 2019, which claims priority to U.S. Provisional Patent Application No. 62/743,937, filed on Oct. 10, 2018, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to tool bit holders, and more particularly to tool bit holders for rotary power tools. 
     BACKGROUND OF THE INVENTION 
     Power tools having a rotational output (i.e. rotary power tools) typically include chuck assemblies with a plurality of jaws that are adjustable to grip and secure a tool bit (e.g., a drill bit). Some chuck assemblies are configured to accept a continuous range of bit sizes (referred to herein as “continuously variable chucks”). Continuously variable chucks are versatile but can be relatively heavy, large, and expensive to produce. In addition, changing bits requires loosening and then retightening the chuck. Other chuck assemblies or tool bit holders are configured to accept one standard size of hex-shanked bits. By taking advantage of a standard shank geometry, such bit holders can be optimized to reduce weight, size, manufacturing cost, and time required to change bits as compared to continuously variable chucks. However, multiple standard nominal sizes exist for hex-shanked bits. For example, ¼-inch hex bits are commonly used for fastener driver, drill, and accessory bits, and 7/16-inch hex bits may be used for higher torque applications. 
     SUMMARY OF THE INVENTION 
     A need exists for a tool bit holder able to accept multiple standard sized bit shanks without suffering the disadvantages of continuously variable chucks. 
     The present invention provides, in one aspect, a multi-size tool bit holder including a first sleeve with a first bit holding bore extending along an axis and a first accommodating bore extending through a sidewall of the first bit holding bore. The multi-size tool bit holder also includes a second sleeve coupled for co-rotation with the first sleeve and movable relative to the first sleeve between a first position and a second position. The second sleeve includes a second bit holding bore extending along the axis and a second accommodating bore extending through a sidewall of the second bit holding bore. The multi-size tool bit holder also includes a retaining element. A first bit shank of a first nominal size is insertable into the first bit holding bore when the second sleeve is in the second position to secure the first bit shank within the first sleeve, a second bit shank of a second nominal size different than the first nominal size is insertable into the second bit holding bore when the second sleeve is in the first position to secure the second bit shank within the second sleeve, and the retaining element has a first securing position in which the retaining element extends through the first and second accommodating bores when the second sleeve is in the first position and into a groove in the second bit shank to axially secure the second bit shank within the second sleeve. 
     The present invention provides, in another aspect, a multi-size tool bit holder including a first sleeve with a first bit holding bore extending along an axis, a second sleeve coupled for co-rotation with the first sleeve and movable relative to the first sleeve between a first position and a second position, the second sleeve including a second bit holding bore, a plurality of retaining elements movable between a first securing position in which the retaining elements project into the second bit holding bore, a first release position in which the retaining elements are withdrawn from the second bit holding bore, a second securing position in which the retaining elements project into the first bit holding bore, and a second release position in which the retaining elements are withdrawn from the first bit holding bore, and a collar surrounding the first sleeve. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a tool bit holder according to an embodiment of the invention. 
         FIG. 2  is a cross-sectional view of the tool bit holder of  FIG. 1  retaining a shank of a second nominal size. 
         FIG. 3  is a cross-sectional view of the tool bit holder of  FIG. 1  retaining a shank of a first nominal size. 
         FIG. 4  is a perspective view of an exemplary tool bit that can be retained by the tool bit holder of  FIG. 1 . 
         FIG. 5  is a diagram illustrating two different nominal sizes of shanks that may be used on the tool bit of  FIG. 2 . 
         FIG. 6  is a cross-sectional view of a tool bit holder according to another embodiment of the invention. 
         FIG. 7  is an exploded view of a tool bit holder according to another embodiment of the invention. 
         FIG. 8  is a cross-sectional view of the tool bit holder of  FIG. 7  retaining a shank of a second nominal size. 
         FIG. 9  is a cross-sectional view of the tool bit holder of  FIG. 7  retaining a shank of a first nominal size. 
         FIG. 10  is a cross-sectional view of a tool bit holder according to another embodiment of the invention. 
         FIG. 11  is an end view of a first sleeve and a second sleeve according to an embodiment. 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
       FIGS. 1-3  illustrate a tool bit holder  10  including a spindle  12  for connection to a rotational output of a rotary power tool (e.g., a drill, impact driver, etc.; not shown). The spindle  12  may be integrated into the rotary power tool and removably coupled to the remainder of the tool bit holder  10  by any suitable means. In some embodiments, the spindle  12  may be removably coupled to the rotary power tool. The bit holder  10  is configured to receive and secure tool bits with standardized shanks of at least two different predetermined, nominal sizes. For example, the illustrated bit holder  10  is configured to receive a tool bit  14  with a hexagonal shank  18  that can be either a first nominal size  22  or a second nominal size  26  ( FIGS. 4 and 5 ). The first and second nominal sizes  22 ,  26  are preferably standard hexagonal shank sizes, such as 7/16-inch and ¼-inch, and the illustrated shank  18  also includes a groove  30 . In other embodiments, the bit holder  10  may be configured to receive tool bits with other types of shanks (e.g., square, three-flat, round, etc.). In addition, the bit holder  10  may be configured to receive tool bits of three or more different nominal shank sizes. 
     Referring to  FIG. 1 , the bit holder  10  includes a first sleeve  34  and a second sleeve  38  coupled for co-rotation with the spindle  12  about a longitudinal axis  42 . The first sleeve  34  has a first or back end  46  engaged with a shoulder  50  on the spindle  12 , and a second or front end  54  opposite the back end  46 . The first sleeve  34  is fixed to the spindle  12  (e.g., by press-fitting, welding, brazing, or via one or more inter-engaging features or fasteners, such as screws or pins). In other embodiments, the first sleeve  34  may be integrally formed as a single piece with the spindle  12 . The second sleeve  38  is slidably received within the first sleeve  34  and includes a first or back end  58  facing the spindle  12  and a second or front end  62  opposite the back end  58 . In the illustrated embodiment, the second sleeve  38  is shorter in length than the first sleeve  34 , and therefore can be received in its entirety within the first sleeve  34  ( FIG. 3 ). In other embodiments, the second sleeve  38  may be configured to protrude at least partially from the first sleeve  34 . 
     A first bit holding bore  66  extends longitudinally into the first sleeve  34  from the front end  54 , and a second bit holding bore  70  extends longitudinally into the second sleeve  38  from the front end  62 . In the illustrated embodiment, the bit holding bores  66 ,  70  extend entirely through the respective sleeves  34 ,  38 . A bit shank  18   a  of a first size (e.g., the nominal size  22 ) is receivable within the first bit holding bore  66  ( FIG. 3 ), and a bit shank  18   b  of a second size (e.g., the nominal size  26 ) is receivable within the second bit holding bore  70  ( FIG. 2 ). Thus, in the illustrated embodiment, the bit shank  18   b  has a smaller nominal size than the bit shank  18   a . The bit holding bores  66 ,  70  each have an inner geometric profile (e.g., a hexagonal profile, a splined profile, a triangular profile, a square profile, etc.) corresponding with an outer geometric profile of the bit shanks  18   a ,  18   b  such that insertion of the bit shanks  18   a ,  18   b  into the respective sleeves  34 ,  38  couples the bit shanks  18   a ,  18   b  for co-rotation with the sleeves  34 ,  38 . In some embodiments, the inner geometric profile of one or both bit holding bores  66 ,  70  may be configured to engage only a subset of surfaces on the corresponding bit shank  18   a ,  18   b . In some embodiments, the inner geometric profiles of the respective bit holding bores  66 ,  70  may be the same, or the inner geometric profiles of the respective bit holding bores  66 ,  70  may differ. 
     The second sleeve  38  is movable between a first position ( FIG. 2 ), in which the front end  62  of the second sleeve  38  is generally flush with the front end  54  of the first sleeve  34 , and a second or retracted position ( FIG. 3 ), in which the second sleeve  38  is moved toward the spindle  12  such that the front end  62  of the second sleeve  38  is recessed behind the front end  54  of the first sleeve  34 . When the second sleeve  38  is in the first position, the tool bit holder  10  is configured to receive the smaller bit shank  18   b  within the bit holding bore  70  of the second sleeve  38 . When the second sleeve  38  is in the second position, the tool bit holder  10  is configured to receive the larger bit shank  18   a  within the bit holding bore  66  of the first sleeve  34 . 
     Referring to  FIGS. 2 and 3 , the bit holder  10  further includes a plunger  74  extending from a front end of the spindle  12  and a collar  78  surrounding the first sleeve  34 . The plunger  74  is fixed to the spindle  12 ; or, in some embodiments, the plunger  74  may be integrally formed as a single piece with the spindle  12 . A front end  82  of the plunger  74  defines a back stop that engages a rear end of the bit shank  18   b  when the bit shank  18   b  is inserted into the second bit holding bore  70  ( FIG. 2 ). In other embodiments, the plunger  74  may be omitted. In such embodiments, the second bit holding bore  70  is a blind bore, the end of which defines a back stop to engage the rear end of the bit shank  18   b . The collar  78  is axially movable along the first sleeve  34  and is biased rearward in the illustrated embodiment (i.e. in the direction of arrow A) by a first spring  86 . In other embodiments, the collar  78  may be configured to be biased forward (i.e. in the direction of arrow B) by the first spring  86 . A second spring  90  surrounds the plunger  74  and spans between the back end  58  of the second sleeve  38  and the front end of the spindle  12 . The second spring  90  biases the second sleeve  38  forward (i.e. in the direction of arrow B). 
     In the illustrated embodiment, the plunger  74  includes a spring seat  94  that radially constrains an inner diameter of the second spring  90 . In other embodiments, the second spring  90  may be radially constrained on its outer diameter (e.g., by the interior wall of the first sleeve  34 ). In some embodiments, the second spring  90  may be a conical spring to facilitate centering the second spring  90  within the first sleeve  34 . Alternatively, the second spring  90  may include two or more stepped cylindrical portions, or the second spring  90  may be a wave spring or any other suitable type of spring for biasing the second sleeve  38 . In yet other embodiments, the second spring  90  may include a plurality of springs (e.g., coil springs) arranged about an periphery of the first sleeve  34 . In such embodiments, each of the plurality of springs may be accommodated in a respective pocket, groove, or the like. 
     With reference to  FIG. 3 , a front end of the illustrated spring seat  94  also defines a back stop that limits movement of the second sleeve  38  to the second position. Forward movement of the second sleeve  38  is limited to the first position by engagement between a radial flange  98  adjacent the rear end  58  of the second sleeve  38  and an internal shoulder  102  in the first sleeve  34 . In alternative embodiments, a retaining ring, a friction ring (e.g., a ring of elastomeric material), projecting pin, or any other suitable means may be provided to limit forward and/or rearward movement of the second sleeve  38  within the first sleeve  34 . In other embodiments, the second spring  90  may itself limit rearward movement of the second sleeve  38  (e.g., when the second spring  90  is fully compressed). 
     The first spring  86  is received between the collar  78  and the first sleeve  34 . Extending between a first retaining ring  106  coupled to the exterior of the first sleeve  34  and a second retaining ring  110  coupled to an interior of the collar  78 , the first spring  86  bears against the second retaining ring  110  to bias the collar  78  rearward (in the direction of arrow A). Rearward movement of the collar  78  is limited by engagement between the first retaining ring  106  and an interior wall  114  of the collar  78  to define an initial position of the collar  78 . Forward movement of the collar  78  (in the direction of arrow B) is limited by full compression of the first spring  86  between the first and second retaining rings  106 ,  110  to define an actuated position of the collar  78  (not shown). One or more washers (not shown) may be provided between either or both the retaining rings  106 ,  110  and the first spring  86  to increase axial retention of the first spring  86 . In some embodiments, either or both of the retaining rings  106 ,  110  may be replaced by integral shoulders formed on the collar  78  or the first sleeve  34 . In addition, other projections, shoulders, or the like may be provided to limit movement of the collar  78  relative to the sleeve  34 . 
     With continued reference to  FIGS. 2 and 3 , a plurality of first retaining elements  118  is received in a plurality of first accommodating bores  122  extending radially through the first sleeve  34 . A plurality of second retaining elements  126  is received in a plurality of second accommodating bores  130  extending radially through the second sleeve  38 . In the illustrated embodiment, the first retaining elements  118  and the second retaining elements  126  are ball bearings. Alternatively, one or more of the retaining elements  118 ,  126  may be pins or other solid bodies. In some embodiments, one or more of the retaining elements  118 ,  126  may include a resilient portion configured to bias the retaining element toward a particular position. For example, in some embodiments, the first retaining elements  118  may be coupled to or integrally formed with the free ends of a snap-ring. 
     The first retaining elements  118  are engageable with the groove  30  in the first bit shank  18   a  to axially retain the first bit shank  18   a  in the first sleeve  34  ( FIG. 3 ). Likewise, the second retaining elements  126  are engageable with the groove  30  in the second bit shank  18   b  to axially retain the second bit shank  18   b  in the second sleeve  38 . The illustrated bit holder  10  includes two first retaining elements  118  and two first accommodating bores  122 , disposed on opposite sides of the first sleeve  34  (i.e. offset from each other by 180 degrees). Likewise, the bit holder  10  includes two second retaining elements  126  and two second accommodating bores  130 , disposed on opposite sides of the second sleeve  38 . In other embodiments, the number or spacing of the first retaining elements  118  and first accommodating bores  122 , and the second retaining elements  126  and second accommodating bores  130 , may vary. For example, in some embodiments only one first retaining element  118  and/or one second retaining element  126  may be used. In some embodiments, the retaining elements  118 ,  126  may be configured to engage other portions of the bit shanks  18   a ,  18   b , such as flats or corners of the bit shanks  18   a ,  18   b . 
     Each of the first retaining elements  118  and the second retaining elements  122  is movable in a radial direction (i.e. a direction transverse to the axis  42 ) between a securing position (illustrated in  FIGS. 2 and 3 ) and a release position (not shown). In the securing position, the first retaining elements  118  project at least partially into the first bit holding bore  66 . Likewise, the second retaining elements  122  project at least partially into the second bit holding bore  70  when in the securing position. When the collar  78  is in the initial position, as illustrated in  FIGS. 2 and 3 , an annular engagement surface  134  of the collar  78  overlies the first accommodating bores  122  in the radial direction. As such, the engagement surface  134  prevents the first retaining elements  118  from moving to the release position. When the second sleeve  38  is in the first position ( FIG. 2 ), the first retaining elements  118  overlie the second accommodating bores  130  in the radial direction. As such, when the first retaining elements  118  are held in the securing position by the collar  78 , the first retaining elements  118  prevent the second retaining elements  126  from moving to the release position. When the collar  78  is moved to the actuated position (not shown), a relief  138  in the collar  78  aligns with the first accommodating bores  122 . The first retaining elements  118  can then move outward into the relief  138  to the release position, which in turn allows the second retaining elements  126  to move outward to the release position. In other embodiments, the collar  78  may be movable to the actuated position by rotating the collar  78  about the axis, by moving the collar  78  in a radial direction. 
     In use, to couple a tool bit  14  with the first, larger bit shank  18   a  to the bit holder  10 , a user first moves the collar  78  forward (in the direction of arrow B) toward the actuated position, against the biasing force of the first spring  86 . This aligns the relief  138  with the first accommodating bores  122 . The user then inserts the bit shank  18   a  into the first bit holding bore  66 . The rear end of the bit shank  18   a  bears against the front end  62  of the second sleeve  38  and moves the second sleeve  38  rearward (in the direction of arrow A) toward the second position ( FIG. 3 ). This compresses the second spring  90 . 
     As the bit shank  18   a  continues to be inserted in the direction of arrow A, the bit shank  18   a  encounters the first retaining elements  118  and pushes them radially outward and into the relief  138 , such that the first retaining elements  118  are moved to the release position. This allows the back end of the bit shank  18   a  to clear the first retaining elements  118 . The bit shank  18   a  is fully inserted when the second sleeve  38  reaches the second position and engages the spring seat  94  on the plunger  74 . At this point, the groove  30  in the bit shank  18   a  aligns with the first accommodating bores  122 . The user can then release the collar  78 , which returns forward to the initial position under the influence of the first spring  86 . An angled transition surface  142  between the relief  138  and the annular engagement surface  134  of the collar  78  bears against the first retaining elements  118 . This displaces the first retaining elements  118  inward to the secured position such that the first retaining elements  118  project into the groove  30  ( FIG. 3 ), thereby axially retaining the bit shank  18   a . In some embodiments, the second sleeve  38  may be configured to transmit axial impacts from the spindle  12  to the bit shank  18   a  (e.g., when the bit holder  10  is used in conjunction with a hammer drill or rotary hammer, for example). The front end  62  of the second sleeve  38  is chamfered, which prevents the back end of the bit shank  18   a  from marring the second bit holding bore  70 . In some alternative embodiments, the rear end of the bit shank  18   a  may engage the front end  82  of the plunger  74  when fully inserted. 
     The engagement surface  134  of the collar  78  prevents the first retaining elements  118  from moving back to the release position until the user desires to remove the tool bit  14  by moving the collar  78  to the actuated position where the first retaining elements  118  are again aligned with the relief  138 . The tool bit  14  can then be pulled in the direction of arrow B, which moves the retaining elements  118  into the relief  138  to clear the groove  30 . Removal of the tool bit  14  is assisted by the second sleeve  38 , which pushes against the back end of the bit shank  18   a  under the influence of the second spring  90 . In some embodiments, a friction ring may be provided in the first sleeve  34  to prevent the tool bit  14  from falling out of the bit holder  10  under the influence of the second spring  90  without additional pulling force exerted on the bit  14  by the user. 
     To couple a tool bit  14  with the second, smaller bit shank  18   b  to the bit holder  10 , the user again moves the collar  78  forward (in the direction of arrow B) toward the actuated position, against the biasing force of the first spring  86 . This aligns the relief  138  with the first accommodating bores  122 . The user then inserts the bit shank  18   b  into the second bit holding bore  70 . At this point, the second sleeve  38  is in the first position ( FIG. 2 ), under the influence of the second spring  90 . As the bit shank  18   b  continues to be inserted in the direction of arrow A, the bit shank  18   b  encounters the second retaining elements  126  and pushes them radially outward through the second accommodating bores  122 . The second retaining elements  126  bear against the first retaining elements  118 , and push the first retaining elements  118  into the relief  138 , such that the first retaining elements  118  and the second retaining elements  126  are moved to the release position. This allows the back end of the bit shank  18   b  to clear the second retaining elements  126 . 
     The bit shank  18   b  is fully inserted when the back end of the bit shank  18   b  engages the front end  82  of the plunger  74 . At this point, the groove  30  in the bit shank  18   b  aligns with the second accommodating bores  130 . The user can then release the collar  78 , which returns to the initial position under the influence of the first spring  86 . The first retaining elements  118  move inward to the secured position and bear against the second retaining elements  126 , which moves the second retaining elements  126  inward to the secured position. The second retaining elements  126  project into the groove  30 , thereby axially retaining the bit shank  18   b . The plunger  74  may be configured to transmit axial impacts from the spindle  12  to the bit shank  18   b  (e.g., when the bit holder  10  is used in conjunction with a hammer drill or rotary hammer, for example). 
     The engagement surface  134  of the collar  78  prevents the first retaining elements  118  and the second retaining elements  126  from moving back to the release position until the user desires to remove the tool bit  14  by moving the collar  78  to the actuated position where the first and second actuating elements  118 ,  126  are aligned with the relief  138 . The tool bit  14  can then be pulled in the direction of arrow B, which moves the retaining elements  126 ,  118  outward to clear the groove  30 . 
     With reference to  FIGS. 2 and 3 , in some embodiments, the plunger  74  may assist in ejecting the bit shank  18   b  from the second sleeve  38  and/or the bit shank  18   a  from the first sleeve  34 . In such embodiments, the plunger  74  may be movable relative to the first sleeve  34  and biased in the direction of arrow B (e.g., by an additional spring; not shown). For example, referring to  FIG. 2 , when a tool bit  14  with the second bit shank  18   b  is coupled to the tool bit holder  10 , the end  82  of the plunger  74  may engage the rear end of the bit shank  18   b  to move the bit shank  18   b  forward in the direction of arrow B when the collar  78  is moved to the actuated position. This may advantageously prevent the second retaining elements  126  from re-engaging with the groove  30  if the user releases the collar  78  before withdrawing the tool bit  14 . In addition, with reference to  FIG. 3 , when a tool bit  14  with the bit shank  18   a  is coupled to the tool bit holder  10 , both the plunger  74  and the second sleeve  38  may push against the back end of the bit shank  18   a  to aid in removal of the tool bit  14 . 
     In some embodiments, the end  82  of the plunger  74  may include a magnet. The magnet may be embedded or molded within the end  82  of the plunger  74 , or received in a recess in the end  82  of the plunger  74 . In some embodiments, the magnet may be fixed to the end  82  of the plunger  74  by epoxy or other suitable adhesive, brazing, one or more fasteners, or any other suitable means. The magnet may retain either of the bit shanks  18   a ,  18   b  in the respective bit holding bores  66 ,  70 . As well as providing additional security for bit shanks  18   a ,  18   b  including the groove  30 , providing the magnet at the end  82  of the plunger  74  may advantageously allow the tool bit holder  10  to also retain bit shanks without a groove  30 . 
     In some embodiments, the tool bit holder  10  may include a third sleeve (not shown) received within and movable relative to the second sleeve  38  in generally the same manner that the second sleeve  38  is received within and movable relative to the first sleeve  34 . In such embodiments, the tool bit holder  10  is configured to receive and retain tool bit shanks of three different nominal sizes, generally in the same manner described above. 
       FIG. 6  illustrates a tool bit holder  210  according to another embodiment. The tool bit holder  210  is similar to the tool bit holder  10  described above with reference to  FIGS. 1-3 , and features and elements of the tool bit holder  210  corresponding with features and elements of the tool bit holder  10  are given like reference numbers plus ‘200.’ In addition, the following description focuses primarily on differences between the tool bit holder  210  and the tool bit holder  10  for the sake of brevity. 
     The tool bit holder  210  includes a plurality of third retaining elements  223  received within a plurality of third accommodating bores  225  extending radially through the first sleeve  234 . The illustrated bit holder  210  includes two third retaining elements  223  and two third accommodating bores  225 , disposed on opposite sides of the first sleeve  234  (i.e. offset from each other by 180 degrees). In other embodiments, the number or spacing of the third retaining elements  223  and third accommodating bores  225  may vary. For example, in some embodiments only a single third retaining element  223  may be used. In the illustrated embodiment, the third retaining elements  223  are ball bearings; however, in other embodiments, the third retaining elements  223  may be pins or the like. 
     With continued reference to  FIG. 6 , the collar  278  includes an internal ring member  281  disposed between the first spring  286  and the second retaining ring  310 . When the larger bit shank  18   a  held by the first sleeve  234 , the radial flange  298  on the second sleeve  238  engages the third retaining elements  223  and forces them to project radially outward out of the third accommodating bores  225 . The internal ring member  281  is engageable with the third retaining elements  223 , which prevents movement of the collar  278  forward toward the actuated position. The collar  278  can only be moved toward the actuated position to release the bit shank  18   a  if the bit shank  18   a  is first pushed rearward, in the direction of arrow A. This aligns a groove  283  in the second sleeve  238  adjacent the radial flange  298  with the third retaining elements  223 , allowing the third retaining elements  223  to move radially inward and out of the path of the internal ring member  281 . In other embodiments, the plunger  274  may be extended to be engageable with the back end of the bit shank  18   a . In such embodiments, when the bit shank  18   a  is pushed rearward, the plunger  274  may be configured to move the third retaining elements  223  out of engagement with the internal ring member  281  to permit movement of the collar  278 . 
     The collar  278  can then be actuated and the tool bit  14  removed, assisted by the influence of the second spring  290 . The tool bit holder  210  thus inhibits accidental ejection of the tool bit  14  from the tool bit holder  210  by requiring two separate actions to release the bit shank  18   a.    
       FIGS. 7-9  illustrate a tool bit holder  410  according to another embodiment. The tool bit holder  410  is similar to the tool bit holder  10  described above with reference to  FIGS. 1-3 , and features and elements of the tool bit holder  410  corresponding with features and elements of the tool bit holder  10  are given like reference numbers plus ‘400.’ In addition, the following description focuses primarily on differences between the tool bit holder  410  and the tool bit holder  10  for the sake of brevity. 
     In the illustrated embodiment of the tool bit holder  410 , the second sleeve  438  is fixed to the spindle  412 , and the first sleeve  434  is movably coupled to the second sleeve  438 . In particular, the first sleeve  434  is axially movable along the second sleeve  438  between a first position ( FIG. 8 ) in which the front end  454  of the first sleeve  434  is generally flush with the front end  462  of the second sleeve  438 , and a second position ( FIG. 9 ) in which the front end  454  of the first sleeve  434  projects beyond the front end  462  of the second sleeve  438 . When the first sleeve  434  is in the first position, the tool bit holder  410  is configured to receive the smaller bit shank  18   b  within the bit holding bore  470  of the second sleeve  438 . When the first sleeve  434  is in the second position, the tool bit holder  410  is configured to receive the larger bit shank  18   a  within the bit holding bore  466  of the first sleeve  434 . 
     In the illustrated embodiment, the tool bit holder  410  further includes a retention sleeve  435  surrounding at least a portion of the first sleeve  434 . The retention sleeve  435  may be fixed to the first sleeve  434  (e.g., by press-fitting the retention sleeve  435  onto the first sleeve  434 ) and thus movable with the first sleeve  434  between the first and second positions. In the illustrated embodiment, the first sleeve  434  is engageable with a front side of a shoulder  439  formed on the second sleeve  438  to limit movement of the first sleeve  434  to the first position ( FIG. 8 ), and the retention sleeve  435  is engageable with a back side of the shoulder  439  to limit movement of the first sleeve  434  to the second position ( FIG. 9 ). In some embodiments, the first sleeve  434  and/or the retention sleeve  435  may include one or more retention features (e.g., detents, recesses, ribs, or the like) configured to retain the first sleeve  434  and the first and/or the second positions. 
     The tool bit holder  410  further includes a collar  478  surrounding at least a portion of the first sleeve  434 . In the illustrated embodiment, the collar  478  is disposed adjacent the retention sleeve  435 . The collar  478  is coupled to the first sleeve  434  for axial movement therewith. In addition, the collar  478  is rotatable to a limited extent relative to the first sleeve  434  between an initial or unactuated position (illustrated in  FIGS. 8-9 ) and an actuated position. A spring  486 , which is a torsion spring in the illustrated embodiment, biases the collar  478  toward the unactuated position. 
     When the collar  478  is in the initial position, as illustrated in  FIGS. 8-9 , an annular engagement surface  534  of the collar  478  overlies the first accommodating bores  522  in the radial direction. As such, the engagement surface  534  prevents the first retaining elements  518  from moving to the release position. When the collar  478  is rotated to the actuated position (not shown), a relief  538  ( FIG. 7 ) in the collar  478  aligns with the first retaining elements  518 . The first retaining elements  518  can then move outward into the relief  538  to the release position, which in turn may allow the second retaining elements  526  to move outward to the release position. 
     In use, to couple a tool bit  14  with the larger bit shank  18   a  to the bit holder  410 , a user first pulls the first sleeve  434  forward to the second position of the first sleeve  434  illustrated in  FIG. 9 . The user then rotates the collar  478  toward the actuated position, against the biasing force of the spring  486 . The user then inserts the bit shank  18   a  into the first bit holding bore  466 . 
     As the bit shank  18   a  is inserted in the direction of arrow A, the bit shank  18   a  encounters the first retaining elements  518  and pushes them radially outward and into the relief  538  in the collar  478 , such that the first retaining elements  518  are moved to the release position. This allows the back end of the bit shank  18   a  to clear the first retaining elements  518 . The bit shank  18   a  is fully inserted when it engages the front end  462  of the second sleeve  434 . At this point, the groove  30  in the bit shank  18   a  aligns with the first retaining elements  518 . The user can then release the collar  478 , which returns forward to the initial position under the influence of the first spring  486 . 
     To eject the bit shank  18   a , the user again rotates the collar  478  to the actuated position. The user may then withdraw the bit shank  18   a , or the user may move the first sleeve  434  toward its first position, illustrated in  FIG. 8 , while maintaining the collar  478  in the actuated position. As the first sleeve  434  is moved toward the first position, the end  462  of the second sleeve  438  pushes the bit shank  18   a  out of the first bit holding bore  466 . 
     To couple a tool bit  14  with the smaller bit shank  18   b  to the bit holder  10 , the user moves the first sleeve  434  to the first position (if it is not already) and then rotates the collar  478  toward the actuated position, against the biasing force of the spring  486 . The user then inserts the bit shank  18   b  into the second bit holding bore  470 . As the bit shank  18   b  continues to be inserted in the direction of arrow A, the bit shank  18   b  encounters the second retaining elements  526  and pushes them radially outward. The second retaining elements  526  bear against the first retaining elements  518  and push the first retaining elements  518  into the relief  538 , such that the first retaining elements  518  and the second retaining elements  526  are moved to the release position. This allows the back end of the bit shank  18   b  to clear the second retaining elements  526 . 
     The bit shank  18   b  is fully inserted when the back end of the bit shank  18   b  engages the back end of the second bit holding bore  470 , or another stop or plunger in other embodiments. The user can then release the collar  478 , which returns to the initial position under the influence of the spring  486 . The first retaining elements  518  move inward to the secured position and bear against the second retaining elements  526 , which moves the second retaining elements  526  inward to the secured position. The second retaining elements  526  project into the groove  30 , thereby axially retaining the bit shank  18   b . 
       FIG. 10 . illustrates a tool bit holder  610  according to another embodiment. The tool bit holder  610  is similar to the tool bit holder  410  described above with reference to  FIGS. 7-9 , and features and elements of the tool bit holder  610  corresponding with features and elements of the tool bit holder  410  are given like reference numbers plus ‘200.’ In addition, the following description focuses primarily on differences between the tool bit holder  610  and the tool bit holder  410  for the sake of brevity. 
     The illustrated tool bit holder  610  includes a first plurality of retaining elements  718  formed as tapered pins. The retaining elements  718  in the illustrated embodiment may extend through both the first sleeve  634  and the second sleeve  638 , such that only a single set of retaining elements  718  is required. The collar  678  may include a plurality of stepped reliefs (not shown) to allow the retaining elements  718  to have a plurality of securing and/or release positions or depths, thereby accommodating differently sized shanks  18   a ,  18   b , and optionally grooves  30  of different depths. 
       FIG. 11  illustrates a first sleeve  834  and a second sleeve  838  according to another embodiment. The first sleeve  834  and the second sleeve  838  may be incorporated into any of the tool bit holders  10 ,  210 ,  410 ,  610  described above, for example. 
     The bit holding bore  870  of the second sleeve  838  includes a non-circular inner geometric profile (e.g., a hexagonal profile in the illustrated embodiment). The second sleeve  838  further includes an outer surface  871  with a circular profile or cylindrical shape. A portion of the outer surface  871  (e.g., near the rear end of the second sleeve  838 ) may include a non-circular profile to maintain a torque-transmitting coupling between the bit holding bore  866  of the first sleeve  834  and the second sleeve  838 . Because the circular profile of the outer surface  871  can be ground to tight tolerances, run-out during operation may be reduced. 
     Thus, the present invention provides, in some aspects, a tool bit holder configured to quickly receive and retain tool bit shanks of at least two different nominal sizes, without the abovementioned deficiencies of a continuously variable chuck. 
     Various features of the invention are set forth in the following claims.