Patent Publication Number: US-7222862-B2

Title: Tool holder

Description:
This invention relates a tool holder for a power tool, in particular a drilling and/or hammering tool. 
   Such tool holders are mounted at the forward end of the drilling and/or hammering tool and are arranged to releasably lock a tool or bit within them. In a drilling tool or in a hammering tool with a rotary mode, the tool holder will generally be rotatingly driven, for example by a spindle of the hammering and/or drilling tool, and the tool holder will rotatingly drive the tool or bit locked within it. Where the tool holder is used on a hammering tool, the tool or bit is mounted within the tool holder so as to be able to undergo limited reciprocation and during operation in a hammering mode, a hammering mechanism of the hammer will impart repeated impacts to the tool or bit mounted within the tool holder. Mechanisms including a manually axially slideable actuating sleeve and/or a manually rotatable actuating sleeve are well known in the art on tool holders for enabling locking or release of a tool or bit within a tool holder. 
   The tool holder itself often will need to be capable of being released from the drilling and/or hammering tool in order to allow it to be changed, for example when a different type of tool or bit is to be held in the hammer. In this case the tool holder body or a spindle of the drilling and/or hammering tool is provided with one or more locking elements, for example locking balls, that are movable in a radial direction (with respect to the axis of the spindle) to retain the tool holder body on the spindle, or to allow release of the tool holder body therefrom. Mechanisms including a manually axially slideable actuating sleeve and/or a manually rotatable actuating sleeve are well known in the art on tool holders for enabling locking or release or relative rotation of a tool holder with respect to a spindle of the hammer. It should be noted that such actuating sleeves may remain on the spindle of a drilling and or hammering tool when the remainder of the tool holder is removed from the spindle. 
   It is often required to provide an axial end stop within tool holder actuating sleeves for fixing components of the tool holder within the sleeves. Such axial end stops are generally provided by using circlips. Circlips are fitted within an annular recess formed within the radially inwardly facing surface of an actuating sleeve, so that a portion of the circlip extends radially inwardly of the radially inwardly facing surface of the sleeve. However, circlips are difficult to assemble and if they are assembled incorrectly, they can prevent the tool holder from operating correctly and can cause damage to components of the tool holder. 
   Also, it is often required to mark the external surface of a tool holder actuating sleeve with symbols indicating, for example, the direction in which the sleeve is moveable or a locked position of the sleeve. These markings may be provided by painting or by making the markings in a contrasting colour to the colour of plastic of the actuating sleeve. 
   According to the present invention there is provided a tool holder for a power tool, in particular a drilling and/or hammering tool comprising a manually actuable sleeve wherein components of the tool holder are held within the sleeve by a snap ring which ring is fitted within the sleeve, characterised in that the snap ring has at least one resilient arm and the sleeve has a corresponding number of recesses formed on its radially inwardly facing surface which recesses can be viewed from a radially outwardly facing surface of the sleeve, arranged such that the or each arm is engageable with a corresponding recess in a snap fit, and the portion of the or each arm which can be viewed from the radially outwardly facing surface of the sleeve is in the shape of a symbol. Thus, the snapring has the dual function of maintaining components within the manually actuable sleeve and of providing an indication of an instructive symbol or icon on the external surface of the manually actuable sleeve which is informative to the user of the drilling and/or hammering tool. For this purpose the shape of the symbol or the outline of the shape may be formed in a contrasting colour to the colour of the external surface of the sleeve. In particular the snap ring may be made from a material, for example a plastics material, of a different colour to the colour of material, for example a plastics material, from which the sleeve is made. 
   In a preferred embodiment at least the radially outermost part of the or each recess is formed in the shape of the symbol. It is also preferred that the radially outermost part of the or each arm is formed in the shape of the symbol to fit the corresponding recess. 
   In order to be viewed from the radially outwardly facing surface of the manually actuable sleeve, the recesses may comprise a through hole which extends to the radially outwardly facing surface of the sleeve. Alternatively, a transparent cover could surround the radially outermost portion of the recesses. To effectively fit the snap ring to the manually actuable sleeve, it is preferred that the or each resilient arm is formed with a latch element in the shape of the symbol and the latch element is received in a snap fit within a correspondingly shaped recess. The snap fit between each resilient arm and the corresponding recess may be reinforced by fitting a peg element in a space located radially inwardly of the resilient arm. 
   The symbol, may be for example, an arrow designating the direction in which the manually actuable sleeve can be moved. 
   The manually actuable sleeve may be actuable to fit and/or remove a tool or bit from the tool holder and/or the manually actuable sleeve may be actuable to fit, remove or rotate the tool holder relative to a power tool. 
   According to the present invention there is also provided a drilling and/or hammering tool comprising a spindle on which a tool holder of the type described above is fitted. The tool may be a hammering tool wherein the tool holder can be rotatingly driven by the spindle and the spindle contains a hammering mechanism which can generate repeated impacts on a rearward end of a tool or bit mounted within the tool holder. 

   
     One form of tool holder in accordance with the present invention will now be described by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a longitudinal cross-section of a tool holder according to the present invention mounted on the forward end of a spindle of a rotary hammer; 
       FIG. 2  is a disassembled perspective view of a manually operated sleeve of the tool holder of  FIG. 1 ; and 
       FIG. 3  is a disassembled perspective view on an alternative embodiment of a manually operated sleeve of the tool holder of  FIG. 1 . 
   

     FIG. 1  shows a tool holder that can be releasably mounted at the forward end  18  of a spindle  1  of a rotary hammer. The hammer includes a spindle  1  that is provided with an air-cushion hammer mechanism comprising a piston, that is caused to reciprocate within the spindle by a swash or wobble mechanism driven by a motor. Reciprocating motion of the piston causes a ram to reciprocate, which strikes a beatpiece  8 . The beatpiece  8  strikes the shank of a drill or chisel bit (not shown) that is held in the bore of the tool holder  10  in known manner. In a combination rotary hammer mode, the tool holder  10  is also rotatingly driven by the spindle  1 . Such hammers are well known in the art. 
   The tool holder  10  as shown is designed to hold a bit that has a pair of closed-end elongate recesses for receiving a locking element  20  for retaining the bit in the tool holder while allowing some degree of axial movement, and a pair of open-ended grooves for receiving rotary driving splines  12 , such bits being of a design referred to as “SDS Plus”, but tool holders for other designs such as SDS Max, hex shank etc. may also be employed. The tool holder includes a hollow, generally cylindrical tool holder body  14  that has a rearward end  16  that can be inserted into the forward end  18  of the hammer spindle  1 . A locking ball  20  for retaining a tool or bit in the tool holder  10  is located in an elongate aperture  22  in the tool holder body  14 , and is held in a position in which it extends into the bore of the tool holder body  14  (and into the recess of any bit held therein) by means of locking ring  24 . The locking ring  24  is located in an axially slidable release sleeve  26  which can be moved rearwardly against the bias of a spring  28  to allow the locking ball  20  to move radially outwardly into recess  30  in order to allow removal of the bit. 
   The tool holder body  14  is held in the spindle  1  by means of four locking balls  32  located in apertures  34  in the spindle wall. The apertures  34  are slightly tapered in order to prevent the balls falling into the bore of the spindle  1 , and the balls are held in the apertures by means of a snap ring  36 . The locking balls  32  can move to a limited extent in the radial direction between a radially outermost position which allows attachment and removal of the tool holder  10 , and a radially innermost position in which the tool holder is retained on the spindle. The tool holder body  14  has four depressions  38  in its outer surface for receiving the locking balls  32  when the tool holder  10  is retained on the spindle. 
   The tool holder  10  is provided with a manually operable sleeve  40  that can be rotated about the tool holder body  14  to a limited extent, and which houses a locking ring  42  that is positioned about the locking balls  32 , and is held in the sleeve  40  by a snap ring  100 . In a first rotational position of the locking ring  42  with respect to the locking balls (position shown in  FIG. 1 ) the tool holder  10  is locked on the spindle  1 . In a second rotational position of the locking ring  42  with respect to the locking balls, pockets in the locking ring  42  are aligned radially outwardly of the locking balls  32 . This enables the locking balls  32  to move radially outwardly to allow insertion of the tool holder main body  14  completely into the forward end  18  of the spindle or to allow removal of the tool holder main body  14  from the forward end  18  of the spindle. The sleeve ( 40 ) is manually rotated by a user to rotate the locking ring ( 42 ) between the first and second rotational positions. 
   The locking ring  42  is held within the interior of the sleeve  40  by means of a retention or snap ring  100  having a generally “L” shaped circumferential cross-section. The retention ring  100  is provided with four resilient flap or arm portions  102  which fit inside a corresponding recess  39  formed in the interior of the sleeve  40 . Each flap portion  102  is provided with a small protuberance  104 , as shown in the shape of a double-headed arrow. The protruberances  104  will snap fit due to the resilience of the flap portions  102  inside a correspondingly shaped through hole  105  in the wall of the sleeve in order to provide a positive engagement of the retention ring  100  in the sleeve  40 . The snap ring  100  is made from a plastics material made of a first colour and the sleeve  40  is made from a plastics material of a second contrasting colour and so the double headed arrows  104  formed on the snap ring  100  can be viewed from the exterior of the sleeve to inform a user that the sleeve  40  is actuated by rotating it. 
   In the above embodiment the snap ring  100  is used in relation to an actuating sleeve  40  which is actuable to enable the tool holder to be mounted on or removed from the spindle  1  of the hammer. The snap ring has the dual function of fixing the locking ring  42  within the sleeve  40  and of providing an external indication on the sleeve  40  to a user that the sleeve is actuable by rotation. 
   Such a snap ring can also be used in an actuating sleeve which is actuable to enable a relative rotation between the tool holder and a spindle of a hammering tool in order to move the tool holder to a desired orientation with respect to the hammer. 
   Such a snap ring can also be used on a tool release sleeve, of a type similar to the sleeve  26 , which is actuable to enable insertion of a tool or bit into the tool holder and/or removal of a tool or bit from the tool holder. The snap ring could again have a dual function, in this case of providing an axial end stop for fixing components within the tool release sleeve and for providing an external indication of the direction in which the tool release sleeve is actuable. For a tool release sleeve which is axially slideable on the tool holder main body  14  , then the protruberances  104  on the resilient flap portions  102  and the correspondingly shaped through holes in the tool release sleeve would be formed as double headed arrows pointing in a direction parallel to the longitudinal axis of the tool holder main body  14 . 
   It should further be noted that it is known to have a tool holder which is removeably mounted on the spindle of a hammer comprising a manually actuable sleeve which is actuable to fit the tool holder on the spindle or remove the tool holder from the spindle, in which the actuating sleeve remains on the spindle when the remainder of the tool holder is removed. Such an actuating sleeve may also be provided with a snap ring of the type described above, which snap ring provides the dual function of maintaining components within the actuating sleeve and providing an external indication to a user of how the actuating sleeve is actuated. 
   An alternative design to that shown in  FIG. 2  is shown in  FIG. 3 , with like parts identified by like numerals. Again a retention ring  100  is provided with four resilient flap or arm portions  102  which fit inside a corresponding recess  39  formed in the interior of the sleeve  40 . The protruberances  104  will snap fit due to the resilience of the flap portions  102  inside a correspondingly shaped through hole  105  in the wall of the sleeve in order to provide a positive engagement of the retention ring  100  in the sleeve  40 . A set of pegs  101  are provided, with one peg for each resilient arm portion  102  in order to reinforce the positive engagement between the retention ring  100  and the sleeve  40 . After the snap ring  100  has been snap fitted into place within the sleeve  40  the pegs are inserted axially (with respect to the axis of the tool holder  10 ) through a hole  103  provided in each arm portion and into a space between each arm portion  102  and the main body of the ring  100 . The pegs  101  are U-shaped and are made of a resilient material and the pegs are elastically deformed by moving the arms of each U-shaped peg together in order to fit the pegs through the holes  103 . Once the pegs are position through the holes  103  and the arms of the peg are released, the pegs resume their usual shape and a pair of rearwardly facing shoulders  101   a ,  101   b  on each peg engage the edge of the holes  103  in the arm portions  102  in order to hold the pegs  101  in place. The pegs  101  limit the radially inward movement of the arm portions  102  towards the main body of the snap ring and so reinforce the connection between the snap ring  100  and the sleeve  40 .