Abstract:
A bit holder has a shank at a proximal end thereof and a blind bit-accepting hole at a distal end thereof, shaped to receive a correspondingly-shaped tool bit. The bit holder has at least one locking mechanism which includes an angled path defined in the bit holder, opening into a side of the bit-accepting hole, extending away from the bit-accepting hole in a proximal direction at an acute angle A from a central axis. A locking element is slideable in the path. A sleeve around the shank is biased towards the bit-accepting hole by a spring, such that a distal end of the locking element extends slightly into the bit-accepting hole. Moving the sleeve towards the proximal end of the bit holder retracts the locking element from the bit-accepting hole, thereby releasing the bit. A spring-loaded plunger in the blind hole may be used to eject the bit automatically when the locking mechanism is released by the sleeve.

Description:
BACKGROUND 
       [0001]    This invention relates to a quick-change tool bit holder that can secure a tool bit by using a wedging element on its external profile. This kind of locking in a quick change holder provides substantially “no play” holding of a tool bit. The wedging element moves in a guided angular path within the body of the holder, the path making a self-locking acute angle with the centre axis of the holder. 
         [0002]    The invention will normally be used for standard hexagonal bits. However, the invention can be readily adapted for use with bits having any polygonal cross-section, including square bits for example, as well as for use with bits having a non-polygonal cross-section, for example ovaloid bits with two flats and two arcs, or tri-centric bits with three flats and three arcs. In general, the invention can be adapted for use with virtually any non-circular cross-section. Typical quick change tool bit holders on the market use some kind of a locking device that engages a circumferential groove per ANSI B 107.4-1982 or an edge notch per ASME B107.600-2008 (B107.26) on the hex shank of a tool bit, resulting in restricting axial freedom of the same. 
         [0003]    Because of inherent features of the circumferential groove in the tool bits, the locking mechanism in each case is of a binary nature. This means the conditions are either, on or off, grabbed or released, locked or unlocked, etc. Due to the stack-up of tolerances in such bit holder devices, coupled with manufacturing tolerances of tool bits, there is generally excessive axial and radial play between the tool bits and the tool bit holder. Tradespersons and do-it-yourselfers accustomed to using solid screw drivers or driver/drill bits directly chucked into a hand drill strongly dislike the resulting sloppy functioning of these quick change holders. 
       SUMMARY OF THE INVENTION 
       [0004]    The quick change tool bit holder presented here offers quick interchangeability of tool bits without compromising the feel of a solid chuck, by providing a substantially no-play hold on the tool bit. The design is based upon at least one angularly guided locking element, the path of which makes a self-locking acute angle ‘A’ with the center axis of the bit holder. This locking element acts as a wedge against the outer surface of the tool bit, hence locking the bit against axial and radial freedom. 
         [0005]    Further details of the invention will be described or will become apparent in the course of the following detailed description and drawings of embodiments of the invention, presented as examples only. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a side cross-section of a first example of the invention, using a pin actuated by a spring-loaded sleeve, shown with a tool bit inserted; 
           [0007]      FIG. 2A  is a cross-section corresponding to  FIG. 1 , but without the tool bit; 
           [0008]      FIG. 2B  is an end view corresponding to  FIG. 2A ; 
           [0009]      FIG. 3A  is a top view at 90 degrees to  FIGS. 1 and 2A ; 
           [0010]      FIG. 3B  is an end view corresponding to  FIG. 3A ; 
           [0011]      FIG. 4A  is a perspective view showing the sleeve and pin of  FIGS. 1 to 3B ; 
           [0012]      FIG. 4B  is an exploded perspective view corresponding to  FIG. 4A ; 
           [0013]      FIG. 5  is a side cross-section of a second example of the invention, using a pin and a roller actuated by the spring-loaded sleeve, shown with a tool bit inserted; 
           [0014]      FIG. 6A  is a cross-section corresponding to  FIG. 5 , without the tool bit; 
           [0015]      FIG. 6B  is an end view corresponding to  FIG. 6A ; 
           [0016]      FIG. 7A  is a top view at 90 degrees to  FIGS. 5 and 6A ; 
           [0017]      FIG. 7B  is an end view corresponding to  FIG. 7A ; 
           [0018]      FIG. 8  is a perspective view showing the sleeve, pin and roller of  FIGS. 5 to 7A ; 
           [0019]      FIG. 9  is a side cross-section of a third example of the invention, very similar to the second example, but with the bit-holder body in two pieces; 
           [0020]      FIG. 10A  is a side cross-section of a fourth example of the invention, very similar to the previous examples, but using a ball; 
           [0021]      FIG. 10B  is a side cross-section where the mechanism is identical to that of  FIG. 10A , simply illustrating that for all embodiments the locking does not depend on the bit having a circumferential groove; 
           [0022]      FIG. 11  is a side cross-section of a fifth example of the invention, using a ball holder and a ball actuated by a spring-loaded sleeve, shown with a tool bit inserted; 
           [0023]      FIG. 12A  is a cross-section corresponding to  FIG. 11 , without the tool bit; 
           [0024]      FIG. 12B  is an end view corresponding to  FIG. 12A ; 
           [0025]      FIG. 13A  is atop view at 90 degrees to  FIGS. 11 and 12A ; 
           [0026]      FIG. 13B  is an end view corresponding to  FIG. 13A ; 
           [0027]      FIG. 14  is a perspective view showing the sleeve, ball holder and ball of  FIGS. 11 to 13A ; 
           [0028]      FIG. 15A  is a side cross-section of a sixth example of the invention, where the sleeve is placed in front of the open end of the body/housing, shown with a tool bit inserted; 
           [0029]      FIG. 15B  is an end view corresponding to  FIG. 15A ; 
           [0030]      FIG. 16A  is a side cross-section of a seventh example of the invention, showing two opposing bit-locking elements one acting in one direction and the other acting in the opposite direction; 
           [0031]      FIG. 16B  is an end view corresponding to  FIG. 16A ; 
           [0032]      FIG. 16C  is a side cross-section of the seventh example, showing the sleeve moved forwardly from the holder; 
           [0033]      FIG. 16D  is a side cross-section of the seventh example, showing the sleeve moved rearwardly; 
           [0034]      FIG. 17A  is a side cross-section of an eighth example of the invention, using a spring-loaded cam; 
           [0035]      FIG. 17B  is a detailed view corresponding to  FIG. 17A ; 
           [0036]      FIG. 18  is a side cross-section showing a bit being inserted;  FIG. 19  is a side cross-section showing the bit locked in place; 
           [0037]      FIG. 20  is a side cross-section of a ninth example of the invention, in which a wedge portion is provided on the inner diameter of a slideable sleeve; 
           [0038]      FIG. 21  is a corresponding view, showing a bit being inserted; 
           [0039]      FIG. 22  is a corresponding view, showing the bit locked in place; 
           [0040]      FIG. 23  is a side cross-section of a tenth example of the invention, similar to the ninth example, but having a spring-loaded plunger to eject the tool bit when the locking mechanism is released; 
           [0041]      FIG. 24  is a corresponding view, showing a bit fully inserted; 
           [0042]      FIG. 25  is a corresponding view, showing the collar being pushed forward and the bit being ejected; 
           [0043]      FIG. 26  is a side cross-section of an example of the mechanism combined with a typical screwdriver handle; 
           [0044]      FIG. 27  is an end view showing three locking mechanisms offset by 120 degrees from each other; 
           [0045]      FIG. 28  is an end view showing two locking mechanisms offset by 180 degrees from each other; 
           [0046]      FIG. 29  is an end view showing two locking mechanisms offset by 120 degrees from each other; 
           [0047]      FIG. 30  is and end view showing an alternative bit and bit holder cross-section, namely tri-centric; and 
           [0048]      FIG. 31  is and end view showing another alternative bit and bit holder cross-section, namely ovaloid. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]      FIGS. 1-4B  shows a first example of the invention. The main body of the bit holder  10  has a shank  11  and a bit-accepting end  12  with a blind bit-accepting hole  13  having a profile to match the profile of the tool bit  30 . The profile will normally be hexagonal, but as stated above, the invention can be adapted for use with bits of basically any non-circular cross-section. The shank  11  normally will be mounted in, for example, a screwdriver handle, as shown in  FIG. 26 . 
         [0050]    At least one pin  15 , preferably but not necessarily cylindrical for ease of manufacturing, acts as a locking element. In the drawings and throughout this description, generally only one locking element will be described, for convenience. However, to achieve maximum “no play” performance, there should preferably be more than one locking element. Preferably, there may be three of them, offset at 120 degrees from each other. 
         [0051]    The pin  15  preferably has a semi-spherical tip  16 , and is slideable and guided in an angularly formed path  14 , the path  14  partially opening into the bit-accepting hole  13  such that the tip  16  extends slightly into the bit-accepting hole  13 . As best seen in  FIGS. 4A and 4B , the pin  15  is anchored to a slideable sleeve  20 , by a slot near  17  the end of the pin and a notch  17 ′ in the sleeve. When the pin connects to the sleeve, the end of the pin sits in the notch and the outside of the notch sits in the slot so as to anchor the pin to the sleeve. 
         [0052]    The angle A at which the path  14  is offset from the axis of the bit holder is preferably in the range of 5 to 13 degrees. Too large an angle increases the diameter of the mechanism excessively, and reduces the effectiveness of the locking. Conversely, too small an angle increase the length of the mechanism, and ultimately also reduces the effectiveness of the unlocking. 
         [0053]    The sleeve  20  is biased towards the distal end of the holder, i.e. towards the open end of the bit-accepting hole  13 , by a spring  21  that has its one flat face against the sleeve  20  while the other face is against a stop ring  22 . The stop ring  22  is retained by lock ring  23  sitting in a recess in the main body  10 . Axial sliding movement of sleeve  20  results in angularly sliding movement of element  15  within the guided path  14  of the body. 
         [0054]    When a tool bit  30  is axially inserted into the bit-accepting hole  13 , it engages with the tip  16  of the element  15 , pushing the element  15  and in turn the sleeve  20  towards the shank  11 . As the insertion of tool bit  30  continues, the element  15  is pushed fully out of the bit-accepting hole  13  and the tip  16  is in contact with the external surface  31  of the bit  30  until the bit stops against the terminating end of bit-accepting hole  13 . Due to the spring biasing, the tip  16  of element  15  is continuously pushed against the outer surface  31  of the tool bit  30 , resulting in wedging and clamping the bit  30  inside the bit-accepting hole  13 . Any effort to pull the tool bit  30  out from the bit-accepting hole  13  only further tightens the grip on the tool bit. This kind of locking ensures “no play” fitment of the tool bit in the holder. In order to release the tool bit  30 , the sleeve  20  must be pulled back towards the shank  11  of the body  10 , against the force of the spring  21 , thus withdrawing the tip  16  from surface  31  and therefore freeing the tool bit  30  for removal. 
         [0055]    As shown in  FIG. 2A , the angular path makes an acute angle “A” with the center axis of the bit holder. Preferably, to make the pressing force between the pin  16  and the bit  30  more effective for preventing axial movement of the bit  30  in the bit-accepting hole  13 , the acute angle “A” is less than 20 degrees, and preferably less than 15 degrees. In the drawings, a preferred angle of 10 degrees is shown. 
         [0056]    A second example of the invention is shown in  FIGS. 5-8 . The mechanism is essentially identical to that of  FIGS. 1-4B , except that the sliding element  15  has a freely rotating roller  18  that replaces tip  16  of the pin  15 . This is most clearly seen in  FIG. 8 . 
         [0057]      FIG. 9  shows a third example of the invention, which is a slightly modified version of the first and second examples. In this example, the angular path for the locking element is formed partially as a slot in portion  12  of the body  10  and partially into a coaxial collar  40  press fitted onto the end  12 . With this split construction there is better access to the guide path during manufacturing, to produce a polished finish with less friction. 
         [0058]      FIGS. 10A and 10B  show a fourth example of the invention, where the bit locking element is a spherical ball  42  positioned at the distal end of the pin  15  within the angular path  14 . The bit locking function is the same as shown in the earlier examples of the invention. 
         [0059]      FIG. 10B  is identical to  FIG. 10A , except that it illustrates that the invention can be used not only with bits having a conventional circumferential groove  43  near their proximal ends ( FIG. 10A ), but also with bits having no such groove. 
         [0060]      FIGS. 11-14  show a fifth example of the invention, which is similar to the fourth example ( FIGS. 10A and 10B ). In this example, the locking element is a spherical ball  42 , but it is anchored to an extended hook portion  24  of sleeve  20 , as best seen in  FIG. 14 . 
         [0061]      FIGS. 15A and 15B  show a sixth example, which is a variation of the fifth example ( FIGS. 11-14 ). In this sixth example, the sleeve  20  is placed in front of the open end of the body/housing. The locking function is the same as in the previous examples, but in this case, to release the bit, the movement of the sleeve pushes the ball  42  away from its locking position instead of pulling it away. 
         [0062]      FIGS. 16A and 16B  show a seventh example of the invention, which is an enhanced version of the sixth example ( FIGS. 15A and 15B ). In this enhanced version, the bit can be locked in both axial directions by a dual-biased sliding sleeve  20 . One locking element  42  locks the bit against movement in one direction, and the other locking element  42 ′ locks the bit against movement in the other direction. The locking elements can be operated for bit release in one direction at a time. The extended anchoring portions  24  of the sleeve  20  have an open ended slot and another closed slot anchoring the locking elements. 
         [0063]      FIG. 16C  shows the sleeve  20  pushed forward from the holder. This forward movement of the sleeve forces the locking element  42 ′ angularly away from the tool bit and thus frees the bit to be pushed deeper into the blind hole.  FIG. 16D  shows sleeve  20  pushed rearwardly, moving the locking element  42  away from the bit, hence freeing the bit to be extracted from the holder. 
         [0064]      FIGS. 17A-19  show an eighth and somewhat different example, where the bit locking element is at least one rotatable eccentric cam  44 . This cam is lightly spring biased in a counter-clockwise direction by a spring  45 . Point ‘B’ is the highest on the peripheral surface of the eccentric cam while point ‘C’ is the lowest. A slideable sleeve  20  is strongly biased towards the open end of bit insertion bit-accepting hole  13 , keeping the eccentric cam  44  pushed in a clockwise direction such that the highest portion ‘B’ extends into the bit-accepting hole  13 . As the tool bit  30  is inserted into the matching bit-accepting hole  13  of the holder, the eccentric cam  44  is pushed into counter-clockwise rotation until it rides on the bit surface  31 , at the same time pushing the sleeve  26  back against its bias. Thus the cam  44  acts as a rotating wedge clamping the tool bit  30  within the bit-accepting hole  13  of the holder. Any effort to pull out the tool bit tends to rotate the eccentric cam  44  in a clockwise direction, resulting in further tightening the grip on the bit. In order to release the tool bit, the sleeve  26  must be pulled back against axial spring bias, allowing cam  44  to rotate counter-clockwise, thus releasing clamping force on the bit for removal. 
         [0065]      FIGS. 20-22  show a ninth example, in which the wedge portion  50  is provided on the inner diameter of a slideable sleeve  52 , the sleeve being biased towards the shank of the bit holder. The axial bias of the slideable wedge causes radial movement of a locking element  42  sitting in a radial hole  54  in the body, the hole communicating with the bit-accepting recess  13  in the holder body. The sleeve  52  is pushed against the bias of the spring, towards the front end of the holder to insert the tool bit into the accepting bit-accepting hole  13 . Once the bit is fully inserted, the sleeve is released, resulting in locking of the tool bit due to the radial force of the locking element. To release the bit  30 , the sleeve is pushed forward. 
         [0066]      FIG. 23-25  show a tenth example, similar to the ninth example ( FIGS. 20-22 ). This tenth example provides automatic locking of the bit  30  on insertion. In order to release the bit  30 , the sleeve  52  is pushed against the spring bias, resulting in taking the radial force off the locking element  42 , such that the tool bit is then ejected by a spring-loaded plunger  56 .  FIG. 24  shows a bit fully inserted, and  FIG. 25  shows the collar being pushed forward and the bit being ejected. 
         [0067]    For clarity and simplicity, most drawings do not show where the mechanism is installed. However, the usual and typical application is to mount the mechanism in a screwdriver (bit-driver) handle.  FIG. 26  is a side cross-section showing a mechanism according to the invention, mounted in a typical screwdriver/bitdriver handle  100 . Obviously any one of the described examples of the invention can be so mounted. 
         [0068]    It will be evident to those knowledgeable in the field of the invention that many variations on the examples described above are conceivable within the scope of the invention. It should therefore be understood that the claims which define the invention are not restricted to the specific examples described above. Possible variations include, for example, the shape of the pin, the structure of the connectivity and the shape of the tool bit profile. 
         [0069]    Most of the examples described above show a single locking mechanism, for clarity of illustration, and for most applications a single mechanism may suffice. However, it should also be appreciated that there can be more than one bit-locking mechanism. For example,  FIG. 27  shows three such mechanisms positioned at 120 degrees to each other, to engage three of the faces of a hexagonal tool bit. Obviously, two opposing mechanisms could also be used, as shown in  FIG. 28 .  FIG. 29  shows another example, where there are two mechanisms, offset by 120 degrees. Theoretically there could be six mechanisms, but clearly that would neither be necessary nor practical. 
         [0070]    It should also be appreciated that although most of the tool bits illustrated in the accompanying drawings are shown with a conventional circumferential groove near the proximal end of the bit, it is an advantage of this invention that the groove is not required for locking, unlike most prior art locking mechanisms. The locking means, whether a pin or a roller or a ball or other, engages a flat portion of the tool bit, such that no groove is required. See  FIGS. 10B and 16A  for specific examples of tool bits without grooves. However, it should be seen that in the other drawings, even when the tool bit does have a conventional groove, that groove is not engaged. 
         [0071]    It should also be appreciated, as stated previously, that the tool bit does not need to be a conventional hexagonal cross-section. Other non-circular cross-sections can be used, such as those shown in  FIGS. 30 and 31  (tri-centric and ovaloid respectively). 
         [0072]    Further variations may be apparent or become apparent to those knowledgeable in the field of the invention, within the scope of the invention as defined by the claims which follow.