Abstract:
A planer including a frame, at least one table mounted on or within the frame, a cutting drum rotatably mounted within the frame, and a motor mounted within the frame and capable of rotatingly driving the cutting drum. The planer also includes a rotatable socket, for receiving a cutting tool, connected to the cutting drum so that rotation of the cutting drum results in rotation of the socket and the cutting tool. The planer further includes a cover for covering the cutting tool and the cover is capable of being moved from a first position where the cover covers the cutting tool to a second position where the cover does not cover the cutting tool.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a guard for a cutting tool mounted on a planer, a thicknesser or a combination of a planer and thicknesser, for cutting holes in a work piece and in particular, for cutting mortises for a mortise and tenon joints. 
   BACKGROUND OF THE INVENTION 
   A typical mortise and tenon joint can be seen in  FIG. 1  and is used to secure two workpieces  30 ,  32  together. A mortise and tenon joint consists of a tongue  34  (the “tenon”) formed on one work piece  30  which fits into a corresponding shaped hole  36  (the “mortise”) formed in the second work piece  32 . Typically the work pieces are timber. The size and shape of the tenon  34  is the same as that of the mortise  36  to provide a secure fit and thus a stable joint between the two work pieces  30 ,  32 . 
   A sketch of a typical planer and thicknesser is shown in  FIG. 2  and comprises a box like frame  4  comprising a horizontal rectangular upper table  14 , 16  and a base  6  connected to each other along their longer sides by two side walls  8 . The horizontal upper table  14 ,  16  is located directly above the rectangular base  6 . A first aperture  12  is formed by one of the shorter ends of the upper table  14 ,  16 , by the base  6  and by one end of each of the two side walls  8 . Similarly, a second aperture (not visible) is formed on the opposite side of the rectangular box frame by the other shorter end of the upper table  14 ,  16 , the other end of the base  6 , together with the other ends of each of the side walls  8 . A passage way  22  connects the two apertures  12  to each other. 
   The upper table is constructed from two rectangular sections, a front section  14  and a rear section  16 . The two sections  14 ,  16  of the upper table are constructed from single rectangular sheets of metal having smooth top surfaces. The top surface of the front section  14  is parallel to the top surface of the rear section  16 . Both the top surfaces are smooth so that a work piece can be slid across their surfaces. The height of the front section  14  can be adjusted relative to the height of the rear section  16 . The two sections  14 ,  16  are separated by a slot  18 . 
   A horizontal lower table  20  is located movably within the passage way  22 . The plane of the lower table  20  is parallel to that of the upper table  14 ,  16 . The lower table  20  is constructed as single rectangular sheet of metal having a smooth top surface. The lower table  20  extends through the full length of the passage way  22  from the first aperture  12  to the second aperture. The width of the table  20  is slightly less than that the width of the passage way  22 . The table  20  is mounted in such a manner that it can be moved vertically upwards or downwards by a height adjustment mechanism  190 , the top surface of the table remaining horizontal at all times during this process. 
   A cutting drum  24  is rotatably mounted within the frame  4  in such a manner that its axis of rotation is perpendicular to the plane of the side walls  8  and parallel to the planes of the upper  14 ,  16  and lower  20  tables. The cutting drum  24  can be rotatably driven by an electric motor (not shown) mounted within the base  6 . 
   A part of the periphery of the cutting drum  24  along its length extends through the slot  18  between the front  14  and rear  16  sections of the upper table. 
   A cutting blade is mounted within each of two grooves  28  of the cutting drum  24  which runs along the length of the cutting drum  24  in well known manner parallel to the axis of rotation. The cutting blades of the cutting drum  24  can be used to cut work pieces in well known manner which are either slid across the upper table  14 ,  16  in one direction or are slid across the lower table  20  in the other direction. 
   The cutting drum  24  is located so that, as the cutting drum  24  rotates, the maximum height of the cutting blade mounted within the cutting drum  24  through the slot  18  is the same as that of the height of the rear section  16  of the upper table, the height of the rear section being fixed. 
   Two drive rollers (not shown) are mounted on either side of the cutting drum  24  inside the frame  4  between the side walls  8  in such a manner that their axes of rotation are parallel to that of the cutting drum  24 . The two drive rollers are rotatably driven by the same electric motor which is used to drive cutting drum  24 . The function of the two drive rollers is to force any work pieces which are fed through the passageway  22  to slide across the lower table  20  and engage with the cutting blades as they pass below the axis of rotation of rotating cutting drum  24  at its lowest point in well known manner. 
   A planer and thicknesser can be used in two different modes of operation. 
   In the first mode of operation, a workpiece is slid across the upper table  14 ,  16  in order to remove the surface of the work piece which is adjacent to the smooth top surface of the upper table  14 ,  16 . The height of the front section  14  of the upper table determines the amount of material which is to removed from the work piece. The height of the front section  14  is adjusted so that the cutting action of the rotating drum  24  removes the right thickness of material from the lower surface of the work piece. The cutting drum  24  is then rotatingly driven by the electric motor. Whilst the cutting drum  24  is rotating, the work piece is slid across the front section  14  of the upper table until it engages with the cutting blade of the cutting drum  24  as it rotates, which repeatedly passes through the slot  18  between the front  14  and rear  16  sections. It is then slid onto the rear section  16  of the upper table across the rotating cutting drum  24 . As the work piece passes over the rotating blades of the cutting drum  24 , the cutting blades remove material from the underside of the work piece. 
   In the second mode of operation, a work piece is slid across the smooth surface of the lower table  20  in order to remove the top surface of the work piece. The height of the lower table  20  within the passageway determines the amount of material which will be removed from the top surface of the work piece as it is passes through the passageway. The height of the lower table  20  is adjusted so that the cutting action of the rotating drum  24  removes the correct thickness of material from the top surface of the work piece. The cutting drum  24  is then rotatingly driven by the electric motor. Whilst the cutting drum  24  is rotating, the work piece is slid across the lower table  20 , until the upper surface of the work piece engages with the rotating cutting blades of the cutting drum  24  as the cutting drum rotates. As a work piece passes under the cutting blades, the cutting blades remove material from the topside of the workiece. The two drive rollers, which are also being rotatingly driven by the electric motor force the work piece through the passageway  22 . 
   UK patent application number 0404557.1 provides a description of one design of planer and thicknesser. 
   Most planer and thicknessers have provision for a cutting tool  40  to be attached to the end of the cutting drum  24 . The most common type of cutting tool  40  is one for making mortises  36  for mortise and tenon joints. The cutting tool  40 , when mounted on the end of the cutting drum  24 , is co-axial with the drum  24  and projects from the side of the cutting drum  24  as shown in  FIG. 2 . When the cutting drum  24  is rotatingly driven by the motor, the cutting tool  40  also rotates. 
   Though the cutting tool  40  can be attached and removed as desired, it is preferable to be able to leave the cutting tool  40  attached thus saving the operator time. However, when the cutting drum  24  is rotated for any reason, the cutting tool  40  also rotates. This results in a hazard to the operator when the cutting tool  40  is not intended to be used, for example, when the planer and thicknesser is planing a work piece. 
   BRIEF SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention there is provided a planer and/or thicknesser comprising a frame; 
   at least one table mounted on or within the frame; 
   a cutting drum rotatably mounted within the frame; 
   a motor, capable of rotatingly driving the cutting drum mounted within the frame; wherein the cutting drum is arranged to cut a work piece when a work piece is passed over the table when the cutting drum is rotatably driven by the motor, 
   a rotable socket, for receiving a cutting tool, connected to the cutting drum so that rotation of the cutting drum results in rotation of the socket; 
   characterised in that there is provided a cover, at least part of which is capable of being moved between a first position where, when a cutting tool is located within the socket, the cutting tool is exposed, and a second position where the cutting tool is surrounded; 
   wherein there is further provided biasing means which urges the moveable part of the cover to the second position. 
   According to a second aspect of the present invention there is provided a guard for a planer and/or thicknesser comprising a frame; 
   at least one table mounted on or within the frame; 
   a cutting drum rotatably mounted within the frame; 
   a motor, capable of rotatingly driving the cutting drum, mounted within the frame; wherein the cutting drum is arranged to cut a work piece when a work piece is passed over the table when the cutting drum is rotatably driven by the motor, 
   a rotable socket, for receiving a cutting tool, connected to the cutting drum so that rotation of the cutting drum results in rotation of the socket; 
   characterised in that the guard comprises mounting means for attaching to a planer and/or thicknesser and at least two tubular sleeves arranged in a telescopic formation, wherein one sleeve is capable of telescopically sliding into and out of the other sleeve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present invention will now be described with reference to following drawings of which: 
       FIG. 1  shows a sketch of an exploded view of a mortise and tenon joint; 
       FIG. 2  shows a sketch of a planer and thicknesser; 
       FIG. 3  shows a perspective view of a side wall of a planer and thicknesser together with the cutting drum, cutting tool and guard (excluding springs) according to the present invention; 
       FIG. 4  shows a side view of a side wall of a planer and thicknesser together with the cutting drum, cutting tool and guard (excluding springs) according to the present invention; 
       FIG. 5  shows a side view of the guard; 
       FIGS. 6A and 6B  show perspective views of the second outer sleeve when view from its two ends; 
       FIGS. 7A and 7B  show perspective views of the first inner sleeve when view from its two ends; 
       FIG. 8  shows a side view of one of the two support rods; 
       FIG. 9  shows a view of the guard partially surrounding the cutting tool; 
       FIG. 10  shows a side view of the guard fully retracted; and 
       FIG. 11  shows a top view of the guard fully retracted. 
   

   Referring to  FIGS. 3 and 4 , a cutting tool  40  is attached to the end of the cutting drum of a planer and thicknesser. The mechanism by which the cutting tool is attached is well known and as such is not described within this specification. Furthermore, the specific design of cutting tool  40  is well known and likewise is not described in this specification. A guard, generally denoted by reference number  50  is attached to the side wall  8  of the planer and thicknesser and which is capable of surrounding the cutting tool  40 . 
   The guard will now be described in more detail. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The guard comprises two sleeves, a first inner sleeve  52  and a second outer sleeve  54 . The second outer sleeve  54  is shown in  FIGS. 6A and 6B . The first inner sleeve  52  is shown in  FIGS. 7A and 7B . When the guard is assembled, the first inner sleeve  52  slideably mounted within and is capable of sliding into and out of the second outer sleeve  54  in a telescopic fashion. 
   Referring to  FIGS. 6A and 6B , the second outer sleeve  54  comprises a tubular body  56  of approximately circular cross-section. Formed along the length of the tubular body  56  on one side is a flat section  58 . Formed in the wall of the tubular body  56 , are two elongate slots  60  which run lengthwise along the body  56  and which are located on opposite sides of the body  56  to each other in a symmetrical fashion about the flat section  58 . 
   Formed, in symmetrical fashion, on one end of the second outer sleeve  54 , are two flanges  62  which project in opposite directions radially outwards from the longitudinal axis of the second sleeve  54 . A bore  64  is formed through each of the flanges  62 . The axis of each bore  64  is parallel to the longitudinal axis of the second outer sleeve  54 . 
   A section  66  of the wall of the tubular body  56  on the opposite side to the flat section  58  has been removed. 
   Referring to  FIGS. 7A and 7B , the first inner sleeve  52  comprises a tubular body  68  also of approximately circular cross-section. Formed along the length of the tubular body  68  on one side is a flat section  70 . The diameter of the tubular body  68  of the first inner sleeve  52  is slightly less than that of the diameter of the tubular body  56  of the second outer sleeve  54 . This is to allow the first inner sleeve  52  to slideably locate within the second outer sleeve as shown in  FIGS. 3 and 4 . The flat section  70  of the first inner sleeve  52  locates adjacent the flat section  58  of the second outer sleeve  54  thus preventing (when the pegs  72  (described below) are not attached) or assists in preventing relative rotation of the first inner sleeve  52  relative to the second outer sleeve  54 . When the first inner sleeve  52  is slideably located within the second outer sleeve  54 , their longitudinal axes are co-axial. 
   Two pegs  72  project in symmetrical fashion radially outwards, in opposite directions, from the longitudinal axis of the tubular body  68  of the first inner sleeve  52 . When the first inner sleeve  52  is located within the second outer sleeve  54 , each of the pegs  72  locates within a corresponding elongate slot  60  as shown in  FIGS. 3 and 4 . The pegs  72  are attached to the tubular body  68  of the first inner sleeve  52  during assembly of the guard. When the first inner sleeve  52  is slideably located within the second outer sleeve  54 , the pegs  72  are passed through the elongate slots  60  and attached to the first inner sleeve  52 . As the first inner sleeve  52  slides into and out of the second outer sleeve  54 , each peg  72  slides along its corresponding elongate slot  60 . The elongate slots  60  limit the amount of sliding movement of the first inner sleeve  52  within the second outer sleeve  54  as well as preventing it from being withdrawn totally from the second outer sleeve  54 . 
   A section  76  of the wall of the tubular body  68  of the first inner sleeve  52  on the opposite side to the flat section  70  has been removed. 
   A rim  74  has been formed around one end of the first inner sleeve  52  having a diameter the same as the diameter of the tubular body  56  of the second outer sleeve  54 . A first helical spring  86  is sandwiched between the rim  74  of the first inner sleeve  52  and the end of the second outer sleeve  54  as best seen in  FIG. 5 . The first spring biases the first inner sleeve  52  outwardly, urging it to slide out of the second outer sleeve  54  and thus, when no additional force is applied to the first inner sleeve  52 , causes the first inner sleeve  52  to extend by its maximum amount out from the second outer sleeve  54 . It should be noted that  FIGS. 3 and 4  do not show the spring  86 . However,  FIGS. 5 ,  9 ,  10  and  11  do show the spring  86 . 
   The second outer sleeve  54  is slideably mounted on two support rods  78 .  FIG. 8  shows one of the support rods  78 . One end  80  of each of the support rods  78  is rigidly attached to the wall  8  of the frame  4  of the planer and thicknesser. The two support rods project horizontally from the wall  8 , in parallel. The longitudinal axes of the two rods  78  are co-axial with and located within the same plane as the longitudinal axis of the cutting drum  24 , the two rods  78  being located on opposite sides of the longitudinal axis of the cutting drum  24  in symmetrical fashion. 
   Each of the support rods  78  passes through a corresponding bore  64  formed in the flanges  62  of the second outer sleeve as shown in the figures. The second outer sleeve  54  can freely slide along the two rods  78 . A circlip  84  is attached to a groove  82  formed in the other end of the rods  78  to prevent the second outer sleeve sliding off the rods  78 . Thus the flanges  62  of the second outer sleeve  54  can slide between the wall  8  of the planer and thicknesser and the circlip  84 . 
   Each of the two support rods  78  has a second spring  88  surrounding it which is sandwiched between the wall  8  of the planer and thicknesser and a side of the flange  62  through which it passes. Each second spring  88  biases the flange  62  of the second outer sleeve  54  outwardly along the support rods  78  away from the planer and thicknesser, urging it to slide away from the wall  8  and thus, when no additional force is applied to the second outer sleeve  54 , causes it to slide by the maximum amount away from the wall  8 . It should be noted that  FIGS. 3 and 4  do show the second springs  88 . However,  FIGS. 5 ,  9 ,  10  and  11  do show the second springs  88 . 
   In use, the two sleeves are biased by the first  86  and second  88  springs outwardly away from the wall  8  of the planer and thicknesser so that the first inner sleeve  52  extends by its maximum amount out from the second outer sleeve  54  and the second outer sleeve  54  to slide by the maximum amount along the support rods  78  away from the wall  8 . When a cutting tool  40  is attached to the cutting drum  24 , the extended sleeves  52 ,  54 , will surround the cutting tool  40  thus preventing contact with it. The rim of the first inner sleeve will extend beyond the end of the cutting tool  40  so that the cutting tool is located entirely within the two sleeves  52 ,  54 . When an operator wishes to use the rotating cutting tool  40 , the operator pushes the sleeves  52 ,  54  against the biasing force of the springs  86 ,  88  towards the wall  8  of the planer and thicknesser so that the first inner sleeve  52  slides into the second outer sleeve  54  and the second outer sleeve slides along the support rods  78  towards the wall  8  of the planer and thicknesser, thus exposing the cutting tool. The sleeves  52 ,  54  are then held against the biasing forces of the springs whilst the cutting tool is used. The sleeves  52 ,  54  can be moved and held against the biasing forces of the springs  86 ,  88  using the work piece to be cut. 
   It will be appreciated that, though the embodiment makes reference to a cutting tool for drilling mortises for mortise and tenon joints, other types of cutting tool can be attached and which can be protected by the guard. For, example, a standard drill bit could be attached.