Patent Abstract:
A shoe assembly for a power tool comprises a shoe portion including a cast and a sole plate adapted to engage a workpiece. The cast has a raised portion having a series of recesses on an interior surface thereof. The shoe assembly also includes a mounting portion for mounting the shoe portion to the housing of the tool. The mounting portion includes a resiliently displaceable ball bearing in a housing mounted to a clamp plate for engaging the recess on the raised portion of the cast in order to selectively releasably hold the shoe portion in one of a plurality of predetermined orientations relative to the mounting portion.

Full Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a shoe assembly for a power tool and relates particularly, but not exclusively, to a shoe assembly for a jigsaw. The invention also relates to power tools incorporating such assemblies.  
       BACKGROUND OF THE INVENTION  
       [0002]     Jigsaws are power tools housing a motor for reciprocatingly driving a blade. The housing generally rests on a shoe assembly for supporting the saw on a workpiece, and the blade projects through the shoe in order to cut the workpiece. Jigsaws can also be equipped to perform bevel cutting, in which the blade is tilted about the longitudinal axis of the shoe in order to produce angular cuts in the workpiece.  
         [0003]     Bevel cutting jigsaws are known which have preset angular inclinations, and mechanisms for locking the blade at an angle to the workpiece. U.S. Pat. No. 6,357,124 describes a clamping mechanism for a bevel-cutting jigsaw in which deflectable ball bearings are held on the underside of a housing of the jigsaw in order to resiliently engage indentations formed on the upper surface of a shoe of the jigsaw. There are several indentations formed at predetermined angles, so that as the housing is pivoted about the shoe, the ball bearings move resiliently in and out of the indentations. A locking mechanism is also provided to clamp the housing and shoe at a selected angle relative to each other.  
         [0004]     This prior art bevel-cutting jigsaw suffers from the drawback that the ball bearings push the shoe away from the housing, making the pivoting movement of the shoe jerky and awkward.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     Preferred embodiments of the present invention seek to overcome the above disadvantage of the prior art.  
         [0006]     According to an aspect of the present invention, there is provided a shoe assembly for a power tool having a housing, at least one working member for engaging a workpiece, and a motor for causing movement of the or each said working member relative to the housing, the shoe assembly comprising:—
        a shoe portion adapted to engage a workpiece and having at least one recess provided on a surface thereof facing away from the housing of the tool in use; and     a mounting portion for mounting the shoe portion to the housing of the tool, the mounting portion having at least one resiliently displaceable projection adapted to engage at least one said recess to selectively releasably hold the shoe portion in one of a plurality of predetermined orientations relative to the mounting portion.        
 
         [0009]     By providing a shoe portion with at least one recess provided on a surface facing away from the housing of the tool in use, engaging at least one resiliently displaceable projection, this provides the advantage of making the pivoting movement of the shoe smoother, and less awkward for the user, than in prior art devices. In a preferred embodiment, at least one said resiliently displaceable projection comprises a respective spring-loaded ball bearing. This provides the advantage that the ball bearing slides easily in and out of engagement with the respective recesses as pressure is applied to the shoe.  
         [0010]     In a preferred embodiment, at least one said spring-loaded ball bearing, at least one said clamp plate having a respective arcuate upper surface adapted to slidably engage the shoe portion such that at least one corresponding said ball bearing can selectively resiliently engage each of a plurality of said recesses of the shoe portion in response to a user pivoting said housing relative to said shoe member. This provides the advantage of increasing the strength of the link between the shoe and the housing.  
         [0011]     The assembly may further comprise first locking means adapted to lock said shoe portion in a predetermined orientation relative to the mounting portion. This provides the advantage of preventing unwanted pivoting of the shoe, and increasing the safety of the assembly. In a preferred embodiment, said first locking means comprises at least one first bolt adapted to lock at least one said clamp plate to the shoe portion. In a preferred embodiment, rotation of at least one said first bolt in a first sense causes at least one corresponding said clamp plate to disengage from the surface of said shoe potion, and rotation in the opposite sense causes at least one corresponding said clamp plate to engage the surface of said shoe portion in order to lock the clamp plate to the shoe portion.  
         [0012]     The first locking means may further comprise at least one nut rotatably mounted to said housing and adapted to receive at least one said first bolt. In a preferred embodiment, at least one said nut comprises a respective lever for rotation of said nut relative to said housing. This provides the advantage of providing easy rotation of the nut for the user.  
         [0013]     In a preferred embodiment the assembly further comprises second locking means adapted to prevent rotation of at least one said first bolt relative to a said clamp plate engaged by said bolt. This provides the advantage of locking the nut lever in place, such that the user accidentally moving the lever cannot loosen the shoe assembly. Said second locking means may comprise at least one second bolt and at least one washer, at least one said second bolt received in at least one said clamp plate such that in a first position, at least one said washer abuts a said first bolt and prevents rotation of said first bolt, and such that in a second position rotation of the first bolt is permitted.  
         [0014]     According to another aspect of the present invention, there is provided a reciprocating tool having a body, a rotary output shaft, a reciprocating member for causing a working member to execute reciprocating motion in response to rotation of said rotary output shaft, and a shoe assembly as defined above.  
         [0015]     In a preferred embodiment, the tool further comprises dust extraction means adapted to remove dust produced by the action of said working member on a workpiece. This provides the advantage removing dust from the vicinity of the tool and the user. Said dust extraction means may comprise a tube projecting from said shoe portion adapted to be connected to a source of suction.  
         [0016]     In a preferred embodiment, said reciprocating tool is a jigsaw.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     A preferred embodiment of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:— 
         [0018]      FIG. 1  is a side view of a jigsaw embodying the present invention;  
         [0019]      FIG. 2  is an exploded perspective view from the front and one side of a shoe assembly of the jigsaw of  FIG. 1 ;  
         [0020]      FIG. 3  is an exploded side perspective view of the shoe assembly of  FIG. 2 ;  
         [0021]      FIG. 4  is a cross sectional view from the side of part of the jigsaw of  FIG. 1 ;  
         [0022]      FIG. 5  is a cross sectional view of the ball bearing and ball bearing housing of the show assembly of  FIG. 2 ;  
         [0023]      FIG. 6  is a perspective view from below of the shoe cast of the assembly of  FIG. 2 ; and  
         [0024]      FIG. 7  is a perspective view from below of the shoe cast of  FIG. 6  incorporating a guard rail. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     Referring to  FIG. 1 , a jigsaw  2  comprises a housing  4  formed from moulded plastics material in two clamshell halves (not shown) as will be familiar to persons skilled in the art. A handle  6  is integrally formed with the housing  4  to allow a user to grip the jigsaw  2  and depress switch  8  to activate a motor (not shown) of the jigsaw  2 . A removable and rechargeable battery pack  10  is shown mounted to the housing  4 . The battery pack  10  is removed from the housing  4  by depressing resilient clips  12 , and the action of pushing the battery pack  10  back into rear portion  14  of the housing  4  displaces resilient clips  12  such that the battery pack  10  locks in place on the rear of housing  4 .  
         [0026]     A blade clamp  16  releasably holds a jigsaw blade (not shown), and executes reciprocating vertical movement when the jigsaw motor is activated. The blades may be of the standard type, or of the flush-cut type as shown in  FIG. 4  and which extend further forwards than standard blades, for example to enable a cut to be made close to a surface such as a wall.  
         [0027]     A shoe assembly  19  includes a metal cast  20  pivotable about an axis  22  generally parallel to a cutting plane of the jigsaw  2 . A raised portion  24  of cast  20  abuts the underside of the housing  4  such that the housing  4  is supported on the shoe assembly  19 . An aperture  25  ( FIG. 2 ) is formed in the cast  20  below blade clamp  16  in order to allow the jigsaw blade to pass through the cast  20 . A guard rail  26  is attached to the front end of cast  20 . The guard rail prevents objects from coming into contact with the blade (not shown). A lever  28  also projects from the housing  4 , the purpose of which will be described in more detail below.  
         [0028]     Referring to FIGS.  2  to  4 , a sole plate  30  is adapted to be attached to the cast  20  by screws  32 . Located between the sole plate  30  and the cast  20  is an adaptor  34  for receiving a suction pipe  36 . The suction pipe  36  passes through the rear of raised portion  24 , into adaptor  34  and is able to suck dust through the front end of adaptor  38 . A clamp plate  40  is also located between sole plate  30  and cast  20 , the clamp plate  40  having a first aperture  42  for holding ball bearing housing  44 . The clamp plate  40  also has a cylindrical bore  46  to allow bolt  48  to pass through.  
         [0029]     Referring to  FIG. 5 , a ball bearing  50  is held in ball bearing housing  44 , and mounted on top of a coil spring  52 . A circular aperture  54  is formed in the upper surface  56  of ball bearing housing  44 . The radius of circular aperture  54  is less than that of the radius of the ball bearing  50 , so that the ball bearing cannot pass through aperture  54  but can project through the aperture to a limited extent as shown by the solid line in  FIG. 5 . The ball bearing  50  can also be depressed against coil spring  52  to be positioned shown by broken line  58  such that the ball bearing does not project beyond the upper surface  56  of ball bearing housing  44 .  
         [0030]     Referring to FIGS.  2  to  4 , the ball bearing housing  44  fits inside aperture  42  formed in the top of clamp plate  40 . Bolt  48  comprises a threaded portion  60 , a smooth portion  62  and a flange section  64 . Adaptor  34  has an opening  66  having a width less than the diameter of flange  64 , such that flange  64  abuts against the edges of the underside of opening  66 . The smooth section  62  of the bolt  48  rests in cylindrical bore  46  of the clamp plate  40  such that the adaptor  34  is supported by the bolt  48  and clamp plate  46  is mounted on top of adaptor  34 . The threaded portion  60  of the bolt passes through opening  68  formed in the raised portion  24  of the cast  20 .  
         [0031]     Referring to  FIG. 6 , a plurality of indentations  70  are formed in the underside of raised portion  24  of the cast  20 . The upper surface of clamp plate  40  has an arcuate shape to allow it to slidably engage the underside of raised portion  24 , and ball bearing  50  projects from ball bearing housing  44  and clamp plate  40 , under the force of compression spring  52 , such that the ball bearing  50  is pushed into one of the indentations  70 .  
         [0032]     The method of pivoting the shoe assembly  19  relative to housing  4  will now be described with reference to FIGS.  2  to  6 .  
         [0033]     A nut  72  held in housing  4  has an inner screw thread (not shown) adapted to receive screw thread  60  of bolt  48 . The nut  72  has a lever  74  extending from it, and rotation of the lever raises or lowers bolt  48  depending on the direction in which lever  74  is turned. Flange section  64  of bolt  48  abuts the underside of the edges of opening  66  of the adaptor  34 , and pushes clamp plate  40  into sliding engagement with the underside of raised portion  24  of the cast  20 . This causes ball bearing  50  to be held in one of the indentations  70 , thus holding the shoe at a predetermined angle relative to the housing  4 .  
         [0034]     In order to change the angle of the shoe assembly  19  relative to the housing  4 , and thus the angle of blade  18  relative to a workpiece, lever  74  is rotated in order to lower the adaptor  34  and clamp plate  40  away from the underside of raised portion  24  of cast  20 . This allows compression spring  52  to extend, and ball bearing  50  to project through aperture  54 . The cast  20  can then be pivoted relative to the housing  4 . It will be understood that as adaptor  34  is connected to housing  4  via bolt  48 , the adaptor  34  moves inside of raised portion  24  with the housing  4 . During the pivoting motion, the ball bearing  50  rolls in and out of indentations  70  under the influence of coil spring  52  until the user selects the desired angular orientation of the shoe assembly  19 . Lever  74  can then be moved in the opposite direction, causing bolt  48  to move upwardly due to the engagement of the screw thread of the nut with the screw thread  60  of the bolt, raising clamp plate  40  into a tight engagement with the underside of raised portion  24 , locking the shoe assembly  19  in place.  
         [0035]     When the shoe assembly  19  is set at the desired angle, a further locking mechanism comprising a second bolt  76  and a washer  78  is provided to prevent lever  74  being accidentally rotated to loosen the assembly. Second bolt  76  is held in the circular aperture  80  of washer  78 . Clamp plate  40  has a second bore  82  having an internal screw thread adapted to engage the threaded portion  84  of second bolt  76 . Referring to  FIG. 4 , the washer  78  abuts the underside of flange  64  of the first bolt  48 . When second bolt  84  is screwed tightly into clamp plate  82 , the flange  64  of the first bolt is trapped between washer  78  and the underside of clamp plate  40 . As a result of this, the first bolt  48  cannot be raised or lowered, therefore holding lever  74  in place and fixing the shoe assembly  19  at a set angle relative to the housing  4 .  
         [0036]     In order to unlock first bolt  48 , the second bolt can be accessed by the user from the underside of the cast  20  and loosened, thus moving washer  78  away from the underside of clamp plate  40  and creating a limited space in which flange  64  can move up and down.  
         [0037]     Referring to  FIGS. 6 and 7 , a groove  86  is formed along each side of the underside of cast  20 . A guardrail  26  is formed from a single piece of steel, bent to form two legs  88  such that the legs  88  are received in groove  86 . By mounting the guard rail in this way, the legs  88  provide reinforcement to the cast  20 .  
         [0038]     It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, more than one resiliently biased ball bearing  50  may be provided, and the shoe assembly  19  may be held in the desired orientation relative to housing  4  solely by means of resilient engagement of a ball bearing  50  with an indentation  70 , i.e. without the use of the second bolt  76  and washer  78 .

Technology Classification (CPC): 1