PATENT ABSTRACT
A chamfering tool comprising: a base having first and second walls meeting each other along a longitudinal axis and defining a longitudinal recess along the bottom of the base for engaging a work piece and a longitudinal ridge along the top of the base; a viewing window in the base for viewing the work piece, the viewing window intersecting the longitudinal recess and the longitudinal ridge; and a blade clamp mounted on the base and arranged to clamp at least part of a blade in the viewing window.

PATENT DESCRIPTION
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a chamfering tool. 
       BACKGROUND OF THE INVENTION 
       [0002]    With the current population growth in the world today there is great importance on constructing new buildings for a variety of purposes. New construction techniques often require efficient processes for a quicker build time. One such technique is to use drywall (also known as plasterboard) panels in the interior fitting of the building. The drywall panel provides a premade surface for the interior of the building which can be decorated with minimal treatment beforehand. One such use of drywall panels is in the interior layout of the building whereby interior walls are constructed from a lightweight timber frame and the drywall panels are fixed to the timer frame. 
         [0003]    Drywall is manufactured in large rectangular panels but often the drywall must be worked and shaped before use. For example if two pieces of drywall are required to meet at a corner, a 45 degree chamfer can be made on each drywall piece. The chamfers are then arranged to be placed adjacent to each other and provide a flush 90 degree corner. 
         [0004]    A known tool for cutting a chamfer is shown in U.S. Pat. No. 316,079 which shows plane with a gage having two flat surfaces meeting at a right angle. The right angle runs longitudinally and engages flat surfaces at the edge of the work piece. A problem with the plane is that the blade and the gage must be adjusted before chamfering a corner of a panel. The user may also have difficulty initially aligning the edge of the work piece with the gage to ensure a clean chamfer. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    Embodiments of the present invention aim to address the aforementioned problems. 
         [0006]    According to an aspect of the present invention there is a chamfering tool comprising: a base having first and second walls meeting each other along a longitudinal axis and defining a longitudinal recess along the bottom of the base for engaging a work piece and a longitudinal ridge along the top of the base; a viewing window in the base for viewing the work piece, the viewing window intersecting the longitudinal recess and the longitudinal ridge; and 
         [0007]    A blade clamp mounted on the base and arranged to clamp at least part of a blade in the viewing window. 
         [0008]    In this way the viewing window allows the user to see the edge of the work piece before the blade engages the work piece. This means that the user can make sure both the first and second walls are engaging the work piece before the blade removes material. The user can see the longitudinal ridge of the tool from above. The longitudinal ridge shows the straight edge of the work piece, which is obscured by the tool. This helps the user align the tool with the work piece. 
         [0009]    Preferably the base comprise a first end and a second end and the viewing window is between the first and second ends. The viewing window may be in the middle of the base which means that a portion of the base engages with the work piece before the blade. This means that the tool can be steadied by the work piece itself before the blade cuts the work piece. 
         [0010]    Preferably the first and second walls are substantially perpendicular to each other. 
         [0011]    Preferably the viewing window comprises at least one edge inclined with respect to the longitudinal axis. The viewing window may be inclined approximately 20 degrees with respect to the longitudinal axis. This means that the blade is angled at a shallow angle with respect to the work piece engages the work piece smoothly. This stops the blade juddering when the tool engages the work piece. 
         [0012]    Preferably the depth of the viewing window the extends in the first and second surfaces at least halfway between the longitudinal ridge and an edge of the first and/or second wall remote from the longitudinal ridge. Optionally the viewing window can extend substantially to the edge of the first and/or second wall remote from the longitudinal ridge. Preferably the viewing window is symmetrical about the longitudinal axis. 
         [0013]    Preferably the chamfering tool comprises a gate member mounted around the viewing window and the blade clamp is arranged to clamp against the gate member. 
         [0014]    Preferably the chamfering tools comprises a handle mounted on the base either side of the longitudinal ridge. Preferably the handle is mounted adjacent to the viewing window. The handle may comprise a groove for receiving a user&#39;s digits. Placing the handle adjacent to the viewing window means that the handle is substantially in the middle of the chamfering tool. This means that the user can comfortably use the chamfering tool with one hand. The groove is ergonomic and suitable for receiving a thumb and a finger either side of the handle. 
         [0015]    Preferably the blade clamp is arranged to clamp the blade substantially perpendicular to the longitudinal axis. This means that the user can more easily align the work piece with the tool. Preferably the blade clamp is arranged to clamp the blade such that the middle of the blade is aligned with the longitudinal axis. This means that blade will less likely to experience a turning moment when the blade engages the work piece and the blade will remain fixed with respect to the tool. 
         [0016]    Preferably the blade clamp comprises a recessed portion for engaging at least two edges of a blade. This means blade is less likely to move with respect to the tool during use. Preferably the chamfering tool comprises a trapezoidal blade. The recess of the blade clamp can engage the two non-parallel sides of the trapezoidal blade. Additionally or alternatively the recess of the blade clamp engages edge opposite the blade edge of the trapezoidal blade. 
         [0017]    Preferably the blade clamp comprises a tool free knob for clamping the blade. This means that the user can easily adjust and replace the blade. 
         [0018]    Preferably the chamfering tool is configured to chamfer panels and the entire depth of an edge of the panel is visible in the viewing window. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Various other aspects and further embodiments are also described in the following detailed description and in the attached claims with reference to the accompanying drawings, in which: 
           [0020]      FIG. 1  shows a perspective view of the chamfering tool; 
           [0021]      FIG. 2  shows side view of the chamfering tool; 
           [0022]      FIG. 3  shows a perspective view of the base of the chamfering tool; 
           [0023]      FIG. 4  shows an underneath view of part of the blade clamp of the chamfering tool; 
           [0024]      FIG. 5  shows a plan view of part of the chamfering tool; 
           [0025]      FIG. 6  shows a perspective view of the chamfering tool; and 
           [0026]      FIG. 7  shows a front end view of the chamfering tool engaging a work piece. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1  shows a perspective view of a chamfering tool  100 . The chamfering tool  100  comprises a base  102 . The base  102  is generally elongate extending along a longitudinal axis  108 . The base  102  has a first wall  104  and a second wall  106  which meet at and extend along the longitudinal axis  108 . 
         [0028]    In some embodiments the first and second walls  104 ,  106  are substantially perpendicular to each other. This means the first and second walls  104 ,  106  can engage a flat surface and an edge of a work piece which are perpendicular to each other. In other embodiments the angle between the first and second walls  104 ,  106  can be any suitable angle. 
         [0029]    Typically the work piece is a panel P (see  FIG. 7 ) such as a portion of drywall. Hereinafter the work piece will be referred to as a panel P although other objects with elongate edges could be used with the chamfering tool. The panel P comprises large flat surfaces and a thin edge. 
         [0030]    The base  102  of the chamfering tool  100  comprises a bottom  110  and a top  112 . The bottom  110  of the base  102  comprises first and second surfaces  114 ,  116  which meet and define a longitudinal recess  107 . The first and second surfaces  114  and  116  are arranged to engage the flat surface of the panel and the edge of the panel. In use the bottom  110  of the base  102  will typically be facing downwards and the top  112  of the base  102  will be facing upwards. 
         [0031]    As mentioned the first and second walls  104 ,  106  are perpendicular to each other and define a longitudinal ridge  109  and a longitudinal recess  107 . The longitudinal recess  107  and ridge  109  are parallel to each other and parallel to the longitudinal axis  108 . In some embodiments the longitudinal recess  107  is an internal corner or vertex defined by the intersection of the first and second walls  104 ,  106 . In some embodiments the longitudinal ridge  109  is an external corner or vertex defined by the intersection of the first and second walls  104 ,  106 . 
         [0032]    The longitudinal ridge  109  extends along the base  102  on the top  112  of the base and provides a visual reference of the obscured corner of the panel P which is being chamfered. The walls  104 ,  106  are made from a sheet material such as metal. The walls  104 ,  106  can be made from any suitable material. The walls  104 ,  106  show the profile of the corner of the panel P underneath in use. 
         [0033]    A viewing window  120  is cut out of the middle of the base  102 . The viewing window  120  allows the user to see the panel P. The window  120  will now be described in further detail with respect to  FIG. 3 .  FIG. 3  shows a perspective view of the base  102 . The base  102  in some embodiments is constructed from a sheet material, such as sheet metal. The base  102  is folded along the three fold lines F 1 , F 2 , F 3 . Folds along F 1 , and F 3  require bending the sheet material up by  135  degrees. This defines two upward side walls  118 ,  122 . Fold F 2  requires bending the sheet material down by  90  degrees. Fold F 2  runs along the same line as the longitudinal axis  108 . Of course in other embodiments the angles the sheet material of the base  102  is bent through can be varied. 
         [0034]    The viewing window  120  is stamped or cut out of the base  102 . In some embodiments the viewing window  120  is stamped before the base  102  is folded. The viewing window  120  defines a large cut out from the base  102 . This provides sufficient space to view the panel P when the chamfering tool  100  engages the panel P. The viewing window  120  extends at least halfway between the longitudinal ridge  109  and an edge  124  of the first or second wall  104 ,  106  distal from the longitudinal ridge  109 . The viewing window  120  intersects the longitudinal ridge  109  and the longitudinal recess  107  between the ends of the base. 
         [0035]    The viewing window  120  is sufficiently large enough to view the entire of an edge of the panel P when the first and second wall  104 ,  106  engage the panel P. A blade is mounted in the viewing window  120  but the viewing window  120  is sufficiently large enough to accommodate the blade and still provide visibility of the panel P to the user. 
         [0036]    The viewing window  120  is substantially triangular in shape and is substantially symmetrical about the longitudinal axis  108 . The viewing window  120  defines an inclined edge  126 . The inclined edge  126  is inclined with respect to the longitudinal axis  108 . In some embodiments the inclined edge  126  with respect to the longitudinal axis  108  by about 20 degrees. A shallow angle of 20 degrees provides a smooth cut on the panel P. 
         [0037]    Returning to  FIGS. 1 and 2 , the chamfering tool comprises a blade clamp  128 .  FIG. 2  shows a side view of the chamfering tool  100 . The blade clamp  128  is arranged to clamp the blade (not shown) to the chamfering tool  100 . The blade clamp  128  comprises a clamping plate  130  and a tightening knob  132 . The clamping plate  130  urges the blade against a gate member  134 . The blade clamp  128  is arranged to mount the blade in the viewing window such that at least a portion of the blade intersects with the longitudinal ridge and recess  109 ,  107 . 
         [0038]    The gate member  134  will be briefly described in reference to  FIGS. 2 and 5 .  FIG. 5  shows a plan view of the gate member  134 . The gate member  134  is substantially flat and made from a sheet material such as metal. The gate member  134  is fixedly mounted to the base  102 . The gate member  134  comprises a two projections  136  which engage with the base  102  in slots  138  and notch  140 . The gate member  134  also comprises two feet  142  which engage with the topside of the first and second walls  104 ,  106 . The feet  142  are folded downwardly such that the feet engage the upward side walls  118 ,  122  and the first and second walls  104 ,  106 . The gate member  134  is mounted on the inclined edge  126  of the viewing window  120 . The relative positions of the inclined edge  126  and the slots  138  cause the inclined edge  126  to urge the gate member  134  upwardly. In this way the two projections  136  slide down the slots  138  and are urged into the notches  140  in the upward side walls  118 ,  122 . This means that the gate member  134  is held in place with respect to the base  102 . The gate member  134  comprises a “V” shaped cut out  144  to align with the viewing window  120 . The V-shaped cut out  144  means that the gate member  134  does not obscure the viewing window  120 . 
         [0039]    The gate member  134  comprises a circular hole  146  for receiving a threaded bolt  150 . The head  148  of the threaded bolt  150  is adjacent to the underside of the gate member  134 . The threaded bolt  150  projects through a slot  152  (as shown in  FIG. 4 ) in the clamping plate  130  and the tightening knob  132  is threadedly mounted onto the threaded bolt  150 . 
         [0040]    The blade clamp  128  can be tightened and loosened by hand using the tightening knob  132 . The tightening knob  132  does not require a tool for tightening or loosening the blade clamp  128 . In some embodiments the tightening knob  132  can be any means suitable to tighten and loosen the blade clamp  128  without a tool. The slot  152  allows the clamping plate  130  to be moved and clamped in different positions relative to the base  102 . In this way the blade can be set at different relative positions in the viewing window  120  and different depth cuts can be achieved. 
         [0041]    A handle  160  is mounted on the base  102 . The handle  160  will now be discussed in further depth with respect to  FIGS. 1 and 6 .  FIG. 6  shows a perspective view of the handle  160 . The handle  160  comprises a general V-shaped cross section to provide a reciprocal recess  162  for receiving the gate member  134  and the clamping plate  130 . The surface  164  of the recess  162  is inclined at the same angle with respect to the longitudinal axis  108  as the inclined surface  126  of the viewing window  120 . The handle  160  is mounted on the base  102  either side of the longitudinal ridge  109  on the top  112  of the base  102 . The handle  160  comprises projections  154  in two arm portions  165 . The projections  154  engage with reciprocal projection receiving holes  156  in the upward side walls  118 ,  122  of the base  102 . The projections  154  clip into the projection receiving holes  156 . The handle  160  is made from a resilient material such as a plastic material. The arms  165  of the handle  160  are biased outwardly such that the arms  165  are squeezed together to insert the projections  154  into the holes  156 . Once the projections  154  are inserted in the holes  156 , the arms  165  urge the projections outwardly fixing the handle  160  to the base  102 . The handle  160  is also fixed to the base by screws  166  and screw holes  168 . 
         [0042]    The handle  160  comprises an outer groove  170 . The outer groove  170  extends substantially along the entire outer surface of the handle  160 . The outer groove  170  is ergonomically adapted to receive digits of a user. In some embodiments the groove  170  receives a user&#39;s thumb on one side of the longitudinal axis  108  and a user&#39;s finger on the other side of the longitudinal axis  108 . The handle  160  is adjacent the viewing window  120 . The handle  160  and the viewing window  120  are mounted along the longitudinal ridge  109  between the ends of the base  102 . Since both the viewing window  120  and the handle  160  are mounted in the middle of the base  102 , the centre of gravity of the chamfering tool  100  is closer to the handle. This means that the tool can be operated with one hand if necessary. 
         [0043]    In some embodiments, the clamping plate  130  comprises a recess for receiving the blade. In other embodiments the clamping plate  130  is flat and the blade is sandwiched between the clamping plate  130  and the gate member  134 . 
         [0044]    The recess  172  will now be discussed in reference to  FIG. 4 .  FIG. 4  shows an underneath plan view of the clamping plate  130 . The recess  172  guides the user when the installing or replacing the blade. In some embodiments the chamfering tool  100  uses trapezoidal blades. Of course, in other embodiments other shaped blades can be used. In some embodiments a lip  174  of the recess  172  engages with a parallel edge of the blade opposite the blade edge. In this way the lip  174  orientates the blade edge perpendicular to the longitudinal axis  108 . 
         [0045]    In other embodiments, and as shown in  FIG. 4 , the recess  172  is configured to engage with a parallel edge of the blade opposite the blade edge with lip  174  and the two non-parallel edges with side lips  176 . Engaging the blade at sides as well stops sideways movement of the blade in the blade clamp  128 . When a blade is mounted flush against lip  184  and side lips  176 , the sharp blade edge extends beyond the clamping plate  130 . 
         [0046]    By providing a recess  172  with a predetermined position for locating the blade, the user can easily install the blade. In some embodiments the recess is arranged such that the middle of the blade is mounted in line with the longitudinal axis  108 . The blade is also orientated substantially perpendicular to the longitudinal axis  108 . In this way the blade does not experience a turning moment when the blade engages the panel and the blade is less likely to move out of place. 
         [0047]    In other embodiments the recess is replaced with two positioning pegs (not shown) for engaging with two cut out portions on trapezoidal blades. 
         [0048]    Use of the chamfering tools will now be briefly discussed with respect to  FIG. 7 .  FIG. 7  shows an end view of the chamfering tool  100  engaging a panel P. The first wall  104  engages the large flat surface  202  of the panel P and the second wall  106  engages the thin edge  204  of the panel P. The corner  206  of the panel P engages with the longitudinal groove  107 . A portion of the base  102  extends in front of the viewing window  120  and the blade. This means that the chamfering tool  100  can be located on the panel P before a cut is made. This helps steady and align the chamfering tool before cutting. The longitudinal ridge  109  provides a visual reference of the corner  206 , obscured by the tool, which is being chamfered. This helps the user keep the tool straight when cutting the panel. The viewing window  120  also permits the user to see that the first and second surfaces  114 ,  116  are engaging the panel. The depth of cut can be adjusted by adjust the position of the blade with respect to the gate member  134  by loosening the blade clamp  128 . 
         [0049]    Embodiments of the present invention have been discussed with particular reference to the examples illustrated. However it will be appreciated that variations and modifications may be made to the examples described within the scope of the invention.