Abstract:
A tool holder system with first and second spindles, a locking ring slideably mounted on the first spindle, a first biasing mechanism biasing the locking ring towards an indentation position where the locking ring surrounds an indentation on the first spindle, and a moveable locking element mounted on the second spindle, the locking element being engageable to the indentation. The first spindle can be unlocked from the second spindle by sliding the locking ring away from the indentation position against the biasing force of the biasing mechanism and towards the second spindle. Such action moves the locking element to disengage from the indentation.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a system by which a tool holder is attached to a spindle of a drill, particularly, a hammer drill. 
       BACKGROUND 
       [0002]    A hammer drill includes a tool holder in which a cutting tool, such as a drill bit, can be supported and driven by the hammer drill. The hammer drill can often drive the cutting tool in three different ways, each being referred to as a mode of operation. The cutting tool can be driven in a hammer only mode, a rotary only mode and a combined hammer and rotary mode. A hammer drill will typically comprise a housing, an electric motor mounted in the main housing and a transmission mechanism by which the rotary output of the electric motor can either rotationally drive the cutting tool to perform the rotary only mode or repetitively strike the end of a cutting tool to impart axial impacts onto the cutting tool to perform the hammer only mode or rotationally drive and repetitively strike the cutting tool to perform the combined hammer and rotary mode. 
         [0003]    In such types of hammer drill, a hollow spindle is typically mounted within the housing which can be rotationally driven by the electric motor. The spindle can be made in a one piece construction or from a number of component parts connected together. A tool holder, which holds the cutting tool, is firmly attached to the front end of the spindle. The electric motor rotatingly drives the cutting tool held within the tool holder by rotatingly driving the spindle within the housing via a gearing in the transmission. 
         [0004]    A piston is typically mounted within the spindle and is connected to the motor via a reciprocating drive mechanism such as a crank mechanism or wobble bearing or similar such device within the transmission mechanism. A beat piece is mounted within the spindle towards the front of the spindle. The beat piece is capable of being axially slid over a limited range of movement. Also mounted within the spindle, in an axially slideable manner, between the piston and the beat piece is a ram. 
         [0005]    The motor causes a cutting tool held in the tool holder to be struck by rotatingly driving the reciprocating drive mechanism to cause the piston to be reciprocatingly driven within the spindle. The piston in turn reciprocatingly drives the ram via an air cushion, the ram repetitively striking the beat piece as it does so. The beat piece transfers the impacts from the ram to the cutting tool. The design and operation of such hammer mechanisms is well known in the art and will not be described in any more detail. European Patent Publication No. EP1157788 describes an example of such a hammer drill. 
         [0006]    The tool holder can be permanently attached to the front end of the spindle of the hammer drill. In such designs, the end of the spindle may form a component part of the tool holder with the spindle supporting a part of the cutting tool which is inserted into the end of the spindle. However, this restricts the range of cutting tools which can be used with the hammer drill as the tool holder will only be able to support certain cutting tools having specific connection arrangements which are compatible with that particular tool holder. 
         [0007]    In order to broaden the range of tool cutting tools which can be used with a particular hammer drill, it is desirable to make the tool holder releasably connectable to the spindle. By making the tool holder releasably connectable, a number of different tool holders can be supplied with each individual hammer drill to enable that hammer drill to be used with a greater range of cutting tools. In this manner, one tool holder having one type of connection system can be removed from the spindle and replaced with another tool holder having a different connection system. European Patent Application No. EP1619000 discloses an example of a tool holder which can be releasably attached to a spindle. 
         [0008]    One of the problems associated with releasably attachable tool holders is ensuring that the connection to and removal from the spindle is kept simple while maintaining a secure connection of the tool holder with the spindle when it is mounted on the spindle. Another problem with known attachable tool holders is that they significantly increase the overall length of the hammer drill when attached to the spindle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  shows a side view of the quick change tool holder attached to the spindle of a hammer drill in accordance with the present invention; 
           [0010]      FIG. 1B  shows a cross sectional view of the tool holder attached to the spindle in the direction of Arrows A in  FIG. 1A ; 
           [0011]      FIG. 1C  shows a cross sectional view of the tool holder attached to the spindle in the direction of Arrows B in  FIG. 1B ; 
           [0012]      FIG. 2A  shows the tool holder separated from the spindle; 
           [0013]      FIG. 2B  shows a vertical cross section of the tool holder separated from the spindle as shown in  FIG. 2A ; 
           [0014]      FIG. 3A  shows the tool holder engaging the end of the spindle; 
           [0015]      FIG. 3B  shows a vertical cross section of the tool holder engaging the end of the spindle as shown in  FIG. 3A ; 
           [0016]      FIG. 4A  shows the tool holder sliding onto the spindle; 
           [0017]      FIG. 4B  shows a vertical cross section of the tool holder sliding onto the spindle as shown in  FIG. 4A ; 
           [0018]      FIG. 5A  shows the tool holder locked onto the spindle; 
           [0019]      FIG. 5B  shows a vertical cross section of the tool holder locked onto the spindle as shown in  FIG. 5A ; 
           [0020]      FIG. 6A  shows the tool holder being released from the spindle; 
           [0021]      FIG. 6B  shows a vertical cross section of the tool holder being released from the spindle as shown in  FIG. 6A ; and 
           [0022]      FIG. 7  shows a schematic diagram of a hammer drill. 
       
    
    
     DESCRIPTION 
       [0023]    Referring to the  FIG. 7 , the hammer drill comprises a housing  2  in which an electric motor  4  is mounted. Electric motor  4  has a drive shaft  6 . A first gear  8  may be rigidly mounted on the drive shaft  6 . 
         [0024]    A second gear  10 , which may be mounted on a first shaft  12 , preferably meshes with the first gear  8 . The second gear  10  may freely rotate about the first shaft  12  but is preferably axially fixed on the first shaft  12 . Rotation of the first gear  8  preferably results in rotation of the second gear  10 . 
         [0025]    A collar  14  may be mounted on the first shaft  12  in an axially slideable but non-rotatable manner. When the collar  14  is in its lowest position, it preferably engages with the second gear  10  to transfer the rotary motion of the second gear  10  to the first shaft  12 . When the collar  14  is in its upper most position, the collar  14  is preferably disengaged from the second gear  10  and as such, no rotary movement is transferred to the first shaft  12 . Movement of collar  14  up and down the first shaft  12  is preferably controlled by a pivotal lever  16  which may be pivoted using a mode change knob (not shown) operated by a user. 
         [0026]    A third gear  20 , which may be mounted on a second shaft  22 , preferably meshes with the first gear  8 . The third gear  20  can freely rotate about the second shaft  22  but is preferably axially fixed on the second shaft  22 . Rotation of the first gear  8  preferably results in rotation of the third gear  20 . 
         [0027]    A collar  24  is preferably mounted on the second shaft  22  in an axially slideable but non-rotatable manner. When the collar  24  is in its lowest position, it preferably engages with the third gear  20  to transfer the rotary motion of the third gear  20  to the second shaft  22 . When the collar  24  is in its upper most position, the collar  24  is preferably disengaged from the third gear  20  and as such, no rotary movement is transferred to the second shaft  22 . Movement of collar  24  up and down the second shaft  22  is preferably controlled by the pivotal lever  16  which may be pivoted using a mode change knob (not shown) operated by a user. 
         [0028]    A bevel gear  30  may be mounted on the top of the first shaft  12 . The bevel gear  30  preferably meshes with a drive gear  32  rigidly attached to a hollow spindle  100  rotationally mounted within the housing  2 . Rotation of the first shaft  12  may rotatingly drive the hollow spindle  100  via the bevel gear  30  and drive gear  32 . 
         [0029]    A crank plate  34  may be mounted on the top of the second shaft  22 . Mounted on the crank plate  34  in turn may be an eccentric pin  36 . One end of a con rod  38  may be pivotally attached to the eccentric pin  36 . The other end of the con rod  38  may be pivotally attached to a piston  40  mounted within the hollow piston  100 . Rotation of the second shaft  22  preferably results in rotation of the crank plate  34  and eccentric pin  36 . The rotation of the eccentric pin  36  preferably results in the reciprocating motion of the piston  40  within the hollow spindle  100 . 
         [0030]    The reciprocating piston  40  may reciprocatingly drive a ram  42  slideably mounted within the hollow spindle  100  via an air spring  46 . The ram  42  in turn may repetitively strike a beat piece  44  which preferably transfers the impacts to a cutting tool  48  held within a tool holder  148  attached to the front of the hollow spindle  100 . 
         [0031]    The spindle  100 , tool holder  148  and the connection mechanism by which the tool holder  148  may be mounted on the spindle  100  will now be described with reference to  FIGS. 1 to 6 . 
         [0032]    The spindle  100  preferably has a longitudinal axis  112  and may comprise a front section  102  and a rear section  104 , with the outer diameter of the front section  102  being less than that of the rear section  104 . 
         [0033]    A shoulder  106  may be formed on the outside of the spindle  100  between the front section  102  and rear section  104 . Shoulder  106  preferably provides the transition between the outer diameters of the front section  102  and the rear section  104 . The front section  102  may also have an inner diameter which is less than that of the rear section  104 . 
         [0034]    A tubular attachment sleeve  108  may be mounted on the front section  102  in an axially slideable manner along the longitudinal axis  112 . Attachment sleeve  108  may have a rear wall  110  which preferably extends from the rear end of the attachment sleeve  108  radially inwards towards the front section  102  of the spindle  100 . The attachment sleeve  108  and rear wall  110  may be integrally formed as a one piece construction. The range of axial movement of the attachment sleeve  108  on the front section  102  is preferably limited by the rear wall  110  engaging the shoulder  106  in the rearward direction and by the rear wall  110  engaging and being prevented from passing a circlip  114  (not shown in  FIGS. 2 to 6 ) mounted in a circumferential groove formed on the front section  102  in the forward direction. 
         [0035]    A first washer  116  may be mounted inside of the attachment sleeve  108  in a slideable manner. The first washer  116  preferably has an outer diameter which is slightly less than the inner diameter of the attachment sleeve  108 . The inner diameter of the first washer  116  may be greater than that of the front section  102  of the spindle  100  to leave a radial gap  118  between the first washer  116  and the front section  102 . The first washer  116  can axially slide inside of the attachment sleeve  108  along the longitudinal axis  112  between a rear position located in close proximity to the circlip  114  (due to it abutting against a third washer  126  described in more detail below) and a front position where it abuts against a second washer  120  axially fixed within a groove inside of the attachment sleeve  108 . The plane of the first washer  116  preferably remains perpendicular to the longitudinal axis  112  as it slides axially within the attachment sleeve  108 . 
         [0036]    The inner diameter of the second washer  120  is preferably greater than that of the front section  102  of the spindle  100  to leave a radial gap  122  between the second washer  120  and the front section  102  which is greater than the radial gap  118  between the first washer  116  and the front section  102  of the spindle  100 . The only function of the second washer  120  is to limit the forward axial movement of the first washer  116  inside of the attachment sleeve  108 . 
         [0037]    A first helical spring  124  may be sandwiched between the first washer  116  and the rear wall  110  for biasing the first washer  116  forward towards and into engagement with the second washer  120 . 
         [0038]    The third washer  126  is preferably mounted inside of the attachment sleeve  108  in a slideable manner between the first washer  116  and the circlip  114 . The third washer  126  preferably has an outer diameter which is slightly greater than the inner diameter of the first washer  116 . The third washer  126  can axially slide inside of the attachment sleeve  108  along the longitudinal axis  112  between a rear position where it abuts against the circlip  114  (and is prevented from passing it) and a front position where it abuts against the first washer  116 , the third washer  126  being prevented from passing the first washer  116  due to the third washer  126  having an outer diameter which is slightly greater than the inner diameter of the first washer  116 . The inner diameter of third washer  126  is preferably slightly larger than that of the front section  102  of the spindle  100  so that it can slide along the front section  102  but is unable to pass the circlip  114 . The plane of the third washer  126  preferably remains perpendicular to the longitudinal axis  112  as it slides axially within the attachment sleeve  108 . 
         [0039]    A second helical spring  128 , which may spiral outwardly in a conical manner in the rearward direction, is preferably sandwiched between the third washer  126  and the rear wall  110 . Spring  128  preferably biases the third washer  126  forward towards and into engagement with the first washer  116 . 
         [0040]    Three indentations  130  may be formed circumferentially around the outside of the front section of the spindle  100  in a symmetrical fashion. The three indentations  130  preferably face towards the inner surface of the first washer  116  when the first washer  116  is located in its most forward position abutting the second washer  120  and the attachment sleeve  108  is in its most rearward position with the rear wall  110  abutting the shoulder  106  (as can be seen in  FIG. 1C ). 
         [0041]    The tool holder  148  preferably comprises a tool holder spindle  140  having a front section  142  and a rear section  144 . The tool holder spindle  140  has a longitudinal axis  146  which is preferably aligned with the longitudinal axis  112  of the spindle  100  when the tool holder  148  is attached to the spindle  100 . The outer diameter of the front section  142  may be smaller than that of the rear section  144 . A shoulder  146  may be formed on the outside of the spindle  140  between the front section  142  and rear section  144 . Shoulder  146  preferably provides the transition between the outer diameters of the front section  142  and the rear section  144 . The front section  142  may also have an inner diameter which is smaller than that of the rear section  144 . 
         [0042]    The inner diameter of the rear section  144  of the tool holder spindle  140  may be slightly greater than the outer diameter of the front section  102  of the spindle  100  to enable the front section  102  of the spindle  100  to be inserted into the rear section  144  of the tool holder spindle  140 . The outer diameter of the rear section  144  of the tool holder spindle  140  may be slightly smaller than the inner diameter of the first washer  116  to enable the rear section  144  of the tool holder spindle  140  to pass through and slide inside of the first washer  116  without interfering with the movement of the first washer  116  when the tool holder  148  is being mounted on and attached to the front section  102  of the spindle  100 . 
         [0043]    The front section  142  of the tool holder spindle  140  preferably supports the tool locking mechanism which is a standard SDS PLUS type locking arrangement. The rear section  144  may support the spindle locking ball bearings  150  which are utilized to lock the tool holder  148  to the front section  102  of the spindle  100 . 
         [0044]    The front section  142  preferably comprises two apertures  152  formed through the wall of the front section  142 , on opposite sides of the front section  142  facing each other and at the same axial position along the front section  142 . A tool locking ball bearing  154  is preferably mounted inside of each of the apertures  152 . The tool locking ball bearing  154  preferably have a diameter which is greater than the thickness of the wall of the front section  142  of the tool holder spindle  140 . The tool locking ball bearings  154  can move over a limited range of movement in a radial direction, within the apertures  152  between a first position where a side of the tool locking ball bearings  154  project into a tubular passage  156  inside of the front section  142  of the tool holder spindle  140  and a second position where a side of the tool locking ball bearings  154  project radially outwardly from the front section  142  of the tool holder spindle  140 . 
         [0045]    A fourth washer  158  is preferably mounted on the front section  142  in an axially slideable manner. The inner diameter of the fourth washer  158  may be slightly larger than that of the outer diameter of the front section  142  of the tool holder spindle  140 . A tubular locking sleeve  160  may be rigidly attached to the fourth washer  158  and preferably slides axially with the fourth washer  158 . 
         [0046]    A rubber nose  162  is preferably attached to the front of the front section  142  of the tool holder spindle  140 . The rubber nose  162  preferably has an integral rubber ring  164  which locates within a radial groove  166  formed circumferentially around the end of the front section  142  in order to attach the nose  162  to the front of the front section  142  of the tool holder spindle  140 . The fourth washer  158  can axially slide on the front section  142  of the tool holder spindle  140  between a rear position where it is in close proximity to a fifth washer  168  which abuts against the shoulder  146  between the front and rear sections  142 ,  144  of the tool holder spindle  140  and a forward position where the locking sleeve  160  abuts against the nose  162 . 
         [0047]    A third helical spring  170  may be sandwiched between the fourth washer  158  and the fifth washer  168  which abuts against the shoulder  146  on the tool holder spindle  140 . Spring  170  preferably biases the fourth washer  158  forward towards its most forward position where the locking sleeve  160  abuts against the nose  162 . 
         [0048]    When the fourth washer  158  is in its forward position where the locking sleeve  160  abuts against the nose  162 , the inner surface of the fourth washer  158  preferably faces towards the two apertures  152 . When the fourth washer  158  is in this position, the inner surface of the fourth washer  158  engages with the tool locking ball bearings  154  and forces them to move radially inwards to a position within the apertures  152  where part of the tool locking ball bearings  154  project into the tubular passage  156  inside of the front section  142  of the tool holder spindle  140 . The tool locking ball bearings  154  are preferably prevented from moving from these positions until the fourth washer  158  is slid rearwardly towards the fifth washer  168  to allow the tool locking ball bearings  154  to move radially outwardly. 
         [0049]    In order to lock a cutting tool  48 , such as a drill bit, into the tool holder  148 , the operator slides the fourth washer  158  rearwardly against the biasing force of the third spring  170  using the locking sleeve  160 . This allows the tool locking ball bearings  154  to move radially outwards. The rear end of the cutting tool  48  is then inserted into the tubular passage  156  of the front section  142  of the tool holder spindle  140  until grooves of the SDS PLUS locking system on the cutting tool align with the tool locking ball bearings  154 . The fourth washer  158  and locking sleeve  160  are then allowed to return to their forward position due to the biasing force of the third helical spring  170 , the fourth washer  158  moving the tool locking ball bearings  154  into the grooves of the cutting tool  48  and locking them in that position. The cutting tool  48  is accordingly prevented from exiting the tool holder  148  due to the tool locking ball bearings  154  being located and held within the grooves of the cutting tool  48 . 
         [0050]    The cutting tool  48  can be released by sliding the fourth washer  158  rearwardly against the biasing force of the third spring  170  using the locking sleeve  160 , moving the fourth washer out of the way of the tool locking ball bearings  154  allowing them to move radially outwards, out of the grooves of the cutting tool  48 . The cutting tool  48  can then be slid out of the front section  142  of the tool holder spindle  140 . 
         [0051]    The rear section  182  of the locking sleeve  160  has been preferably enlarged so that it has a diameter greater than a front section  184  of the attachment sleeve  108 . This allows the rear section  182  of the locking sleeve  160  to slide over the front section  184  of the attachment sleeve  108  when either the locking sleeve  160  is slid rearward or the attachment sleeve  108  is slid forward, the sliding movement of either of the two sleeves not engaging nor having any interaction with the other sleeve. 
         [0052]    The rear section  144  preferably comprises three apertures  204  formed through the wall of the rear section  144  in a symmetrical fashion at the same axial position along the rear section  144 . The number of apertures  204  and the position of the apertures  204  around the rear section  144  preferably corresponds to the number and positions of the indentations  130  on the front section  102  of the spindle  100 . Mounted inside of each of the apertures  204  is a spindle locking ball bearing  150  which preferably has a diameter which is greater than the thickness of the wall of the rear section  144  of the tool holder spindle  140 . 
         [0053]    The spindle locking ball bearings  150  can move over a limited range of movement in a radial direction within the apertures  204  between a first position where a side of the spindle locking ball bearings  150  project into a tubular passage  200  inside of the rear section  144  of the tool holder spindle  140  and a second position where a side of the spindle locking ball bearings  150  project radially outwardly from the rear section  144  of the tool holder spindle  140 . A circlip  202  preferably holds the spindle locking ball bearings  150  within the apertures  204 . 
         [0054]    The method of attaching and removing the tool holder  148  from the spindle  100  will now be described.  FIGS. 2A and 2B  show the tool holder  148  located remotely from the spindle  100 . The first and third washers  116 ,  126  are preferably biased to their most forward positions inside of the attachment sleeve  108  by the two helical springs  124 ,  128 , with the first washer  116  preferably abutting against the second washer  120 , and the third washer  126  preferably abutting against the first washer  116 . 
         [0055]    The front section  102  of the spindle  100  may be inserted into rear section  144  of the tool holder spindle  140  as shown in  FIGS. 3A and 3B . As it is inserted, the rear section  144  of the tool holder spindle  140  preferably passes through the first washer  116  without engaging or coming into contact with the first washer  116 , the rear end  208  of the rear section  144  engaging with the third washer  126  as it slides over the front section  102  of the spindle  100 . 
         [0056]    As the front section  102  continues to slide into the rear section  144  of the tool holder spindle  140 , the rear end  208  preferably pushes the third washer  126  rearwardly against the biasing force of the second helical spring  128  as shown in  FIGS. 4A and 4B . The force applied to the third washer  126  is preferably transferred to the rear wall  110  via the second helical spring  126  resulting in the rear wall  110  and attachment sleeve  108  moving rearwardly on the front section  102  until the rear wall  110  engages with the shoulder  106  on the spindle  100 . The attachment sleeve  108  and rear wall  110  are then held in their rearmost positions due to the biasing force of the second helical spring  128 . As the attachment sleeve  108  and rear wall  110  are then held in their rearmost positions, the third washer  126  continues to move rearwardly inside of the attachment sleeve  108  towards the rear wall  110  by the insertion of the rear section  144  of the tool holder spindle  140  into the attachment sleeve  108 . 
         [0057]    As the front section  102  of the spindle  100  continues to slide into the rear section  144  of the tool holder spindle  140 , the spindle locking ball bearings  150  engage with the end of the front section  102  of the spindle  100  and are pushed to their radially outward position, out of the tubular passage  200  inside of the rear section  144  of the tool holder spindle  140 . When the spindle locking ball bearings  150  are in their radially outer positions, they are unable to pass through the first washer  116  as the inner diameter of the first washer  116  is smaller than the radial position of the spindle locking ball bearings  150 . As the front section  102  continues to slide into the rear section  144  of the tool holder spindle  140 , the spindle locking ball bearings  150  travel along the outside of the front section  102  in their radially outer position until they engage with the first washer  116  and commence pushing the first washer  116  rearwardly against the biasing force of the first helical spring  124 . The first and third washers  116 ,  126  will both continue to be pushed rearwardly inside of the attachment sleeve  108  against the biasing force of the two helical springs  124 ,  128  by the spindle locking ball bearings  150  and the rear end  208  of the rear section  144  of the tool holder spindle  140  respectively, until the third washer  126  is adjacent the circlip  114  and the spindle locking ball bearings  150  align with the indentations  130 . Some rotational movement of the tool holder  148  on the spindle  100  may be required to provide precise alignment of the spindle locking ball bearings  150  and the indentations  130 . 
         [0058]    Once aligned, the spindle locking ball bearings  150  are able to enter the indentations  130 . The biasing force of the first helical spring  124  will then push the first washer  116  forward causing the first washer  116  to push the spindle locking ball bearings  150  into the indentations  130 . A chamfer (not shown) on the inner surface of the first washer  116  assists in moving the spindle locking ball bearings  150  into the indentations  130 . The first washer  116  then moves to the same axial position as the spindle locking ball bearings  150  where it abuts against the second washer  120 , locking the spindle locking ball bearings  150  into the indentations  130 . The tool holder is then locked onto the spindle  100  by the spindle locking ball bearings  150  being located and held within the indentations  130  by the first washer  116 . 
         [0059]    In order to release the tool holder  148  from the front section  102  of the spindle  100 , the attachment sleeve  108  is preferably slid forward against the biasing force of the second helical spring  128 , the rear wall moving away from the shoulder  106  and towards the cir-clip  114  as it does so. As the attachment sleeve  108  moves forward, the first washer  116  preferably moves forward with the attachment sleeve  108  due to the biasing force of the first spring  124 . As the first washer  116  moves forward of the spindle locking ball bearings  150 , ball bearings  150  move radially outwardly out of the indentations  130  towards the inner surface of attachment sleeve  108 . The tool holder  148  is then urged off the end of the front section  102  of the spindle  100  by the biasing force of the second spring  128  urging the third washer  126  away from the rear wall  110  which in turn pushes the rear end  208  of the rear section  144  of the tool holder spindle away from the rear wall  110 . The first washer  116  is moved sufficiently far forward by the forward movement of the attachment sleeve  108  that it passes the end of and locates to a position forward of the front section  102  of the spindle  100  by a sufficient amount to allow the spindle locking ball bearings  150  to move radially inwardly after sliding along and then moving past the front section  102  of the spindle  100  in order to pass through the first washer  116  whilst located in their radially inner position. The tool holder can then be removed and the attachment sleeve released  108 . 
         [0060]    While the present invention has been described in relation to a hammer drill, it will be appreciated that it is applicable to any power tool or other tools requiring a tool holder.