Patent Abstract:
A circular saw includes a base plate defining a base plane, a bevel bracket which supports a circular saw blade and is pivotally mounted on the base plate for tilting the blade, the bevel bracket having a pivoting axis which is parallel to the base plane and the blade and perpendicular to a rotational axis of the blade, and the blade partly extending through an opening forming in the base plate, and an anti-splinter device for preventing cutting chips from splintering. The anti-splinter device comprises a pair of slides mounted in the opening and forming a gap between their opposing ends, an outcoming section of the blade passing through the gap, and slide driving means associated with the bevel bracket and driving the slides to move in conformity with the tilting of the blade to allow the gap to accommodate the positional change of the outcoming section of the blade.

Full Description:
TECHNICAL FIELD  
       [0001]    The present invention relates to a circular saw with an improved anti-splinter device for preventing chip splintering during the operation of the saw. 
       BACKGROUND ART  
       [0002]    Chip splintering happens during the operation of a circular saw. While the saw blade cuts into a workpiece, chips of the workpiece will be engaged by the saw blade and splinter out from the workpiece. Due to the rotation direction of the saw blade, the splintered chips will fly to the operator and sometimes may hurt the operator. 
         [0003]    Currently, there are a few structures in the market for preventing chip splintering on the circular saw. One solution is a fixed anti-splinter structure which forms a gap through which the saw blade passes through. The gap is narrow for preventing the chips from splashing between the saw blade and the anti-splinter structure. This anti-splinter structure is effective for straight cutting operation where the saw blade is in a normal vertical orientation. However, when the saw is used for bevel cutting where the saw blade cuts a workpiece in an oblique orientation (the saw blade tilts a certain angle from its normal vertical orientation), the distance between the anti-splinter structure and the blade decreases due to orientation change of the blade. In this condition, there is a danger that the blades contacts with the anti-splinter structure, which may result in a malfunction of the saw. To avoid such contact, the gap needs to be widened, which will, however, lower down the anti-splinter function of the anti-splinter structure. 
       SUMMARY OF INVENTION  
       [0004]    An object of the present invention is to provide a circular saw with an improved anti-splinter device for preventing chip splintering during the operation of the saw and providing a safe and comfortable working environment to operators. 
         [0005]    For achieving this task, according to one aspect of the invention, a circular saw comprises a base plate defining a base plane; a bevel bracket which supports a circular saw blade and is pivotably mounted on the base plate for tilting the blade, the bevel bracket having a pivoting axis which is substantially parallel to the base plane and the blade and substantially perpendicular to a rotational axis of the blade, and the blade partly extending through an opening formed in the base plate; and an anti-splinter device for preventing cutting chips from splintering out of the opening during the operation of the saw and comprising: a pair of slides mounted in the opening and forming a gap between their opposing ends, an outcoming section of the blade passing through the gap; and slide driving means associated with the bevel bracket and driving the slides to move in the base plane in conformity with the tilting of the blade to allow the gap to accommodate the positional change the outcoming section of the blade. 
         [0006]    In a preferred embodiment, at least one of the opposing ends of the slides is formed with a slanted portion facing toward the blade. 
         [0007]    In a preferred embodiment, the anti-splinter device further comprises guide members attached to the base plate for guiding the movement of the slides. 
         [0008]    In a preferred embodiment, the slide driving means comprises a cam plate fixed to the bevel bracket at the pivoting axis, cam slots are formed through the cam plate on opposites sides of the pivoting axis, and the slides are each formed with a protrusion inserted into a corresponding cam slot. 
         [0009]    In a preferred embodiment, each of the cam slots extends from an upper end to a lower end, and the distance between the cam slots increases as they extending downwardly. 
         [0010]    In a preferred embodiment, the slide driving means comprises a cam which drives one of the slides to move in one direction and a returning means which drives the one of the slides to move in reverse direction, the slides being coupled with each other via a connecting means. 
         [0011]    In a preferred embodiment, the slide driving means comprises a sleeve fixed to the bevel bracket at the pivoting axis and a sliding lever slidably inserted through the sleeve and connected with the slides. 
         [0012]    In a preferred embodiment, the slide driving means comprises a bar-linkage which is coupled between the bevel bracket and one of the slides, the slides being coupled with each other via a connecting means. 
         [0013]    Alternatively, the slide driving means comprises a pair of bar-linkages each coupled between the bevel bracket and a corresponding one of the slides. In a preferred embodiment, the bar-linkages drive the slides in a way that their moving velocities are different from each other. 
         [0014]    According to the invention, as the saw blade changes its orientation, the anti-splinter slides move accordingly so as to keep small distances between the slides and the blade. Thus, the anti-splinter device of the circular saw always effectively prevents the chips from splashing from the workpiece as well as ensures a clear line of sight and convenient working condition for operators. Further, by providing the anti-splinter slides near the cutting area, the cutting quality can be improved. The circular saw of the invention can be effectively used for both straight cutting and bevel cutting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The foregoing and other aspects of the invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the following drawings, in which: 
           [0016]      FIG. 1  is a top perspective view of a circular saw according to an embodiment of the invention; 
           [0017]      FIGS. 2 and 3  are bottom perspective view of the circular saw of  FIG. 1 , taken in different view angles; 
           [0018]      FIG. 4  is a front view of an anti-splinter device adopted in the circular saw of  FIG. 1 ; 
           [0019]      FIG. 5  is a perspective view of a cam plate of the anti-splinter device of  FIG. 4 ; 
           [0020]      FIG. 6  is a perspective view of anti-splinter slides of the anti-splinter device of  FIG. 4 ; 
           [0021]      FIG. 7  is a front view similar to  FIG. 4  showing the movements of the cam plate and the anti-splinter slides; 
           [0022]      FIG. 8  is a front view similar to  FIG. 4  showing chip flows during the cutting operation of the saw of the invention; 
           [0023]      FIG. 9  is a front view of another embodiment of the anti-splinter device; 
           [0024]      FIG. 10  is a front view of yet another embodiment of the anti-splinter device; and 
           [0025]      FIG. 11  is a front view of yet another embodiment of the anti-splinter device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Now the preferred embodiments of the circular saw and its anti-splinter device according to the invention will be described with reference to the drawings. 
         [0027]    In this description, the term “workpiece” refers to a block of any cuttable material, such as wood, plastic material, glass, metal, or the like. 
         [0028]      FIGS. 1 to 3  show a circular saw according to an embodiment of the invention. The circular saw comprises a base plate  1  which has a generally flat shape and thus defines a base plane. The base plate  1  will be put on a surface of the workpiece to perform a cutting operation. A bevel bracket  12  is pivotable supported by the base plate  1 , and a casing  2  is pivotable supported by the bevel bracket  12  via a pivoting joint  5 . The casing  2  carries a rotary motor (not shown) and a circular saw blade  10  driven in rotation by the motor. A outcoming section of the blade  10 , which is to be cut into a workpiece, extends through an elongated opening  8  formed in the base plate  1 . The pivoting axis of the pivoting joint  5  is perpendicular to the blade  10 , so that the casing  2 , together with the motor and the blade  10 , is pivotable with respect to the bevel bracket  12  to set or change the cutting depth of the blade  10 . 
         [0029]    The casing  2 , together with the motor and the blade  10 , is also pivotable with respect to the base plate  1  around a pivoting axis X ( FIG. 4 ) to adjust the orientation of the blade  10 . The pivoting axis X is located near the base plate  1 , substantially parallel to the base plane and the blade  10  and substantially perpendicular to the rotational axis of the blade  10 . Tilting scale  4  indicates the pivoting angle of the bevel bracket  12  (i.e., the tilting angle of the blade  10 ). Fastening means  6  releasably fixes the bevel bracket  12  to a desired pivoting position, and thus fixes the tilting angle of the blade  10 . 
         [0030]    By adjusting the orientation of the blade  10 , the cutting angle between the blade  10  and the workpiece can be set. Vertical orientation of the blade  10 , which corresponds to, for example, 0° of tilting angle indicated on tilting scale  4 , is set for straight cutting, which means that the blade vertically cuts into a workpiece. Tilted orientation of the blade  10 , which corresponds to a tilting angle indicated on tilting scale  4  larger than 0°, is set for bevel cutting, which means that the blade obliquely cuts into a workpiece. 
         [0031]    During cutting operation of the saw, the blade  10  rotates in a direction shown by arrow “A” in  FIGS. 1 to 3 . At the outcoming section of the blade  10  where the blade  10  rotates out from the base plate  1 , cutting chips move out from the workpiece and fly up. In order to prevent the chips from splintering out of the base plate  1 , or reduce the speed of the chips which are flowing out of the base plate  1 , an anti-splinter device  100  is arranged about the outcoming section of the blade  10 . 
         [0032]      FIG. 4  shows the details of the anti-splinter device  100  according to an embodiment of the invention. The anti-splinter device  100  is mounted near one longitudinal end (mounting end) of the elongated opening  8  of the base plate  1  and mainly comprises a cam plate (slide driving means)  20 , left and right guide members  14  and  16  and left and right anti-splinter slides  30  and  40 , all of which will be described below. 
         [0033]    By pivoting the bevel bracket  12 , the blade  10  reaches an oblique orientation which forms a tilting angle θ with a vertical plane Y passing through the pivoting axis X. The bevel bracket  12  is pivotable in a direction so that the tilting angle θ of the blade  10  changes from 0° to a certain degree as well as in a reverse direction so that the tilting angle θ of the blade  10  returns to 0°. 
         [0034]    The terms “left and right” used here are defined when viewing the anti-splinter device  100  in a direction from another longitudinal end of the elongated opening  8  toward the mounting end of the elongated opening  8 . In the normal vertical orientation, the blade  10  is parallel to the vertical plane Y. For bevel cutting, the blade  10  pivots in clockwise direction in  FIG. 4  from its normal vertical orientation to an oblique orientation through the tilting angle θ. 
         [0035]    The cam plate  20  is fixed to the bevel bracket  12  and has a narrower top side and a wider bottom side. As shown in  FIG. 5 , a central hole  22  is formed through the cam plate  20  for inserting a screw through it to fix the cam plate  20  to the bevel bracket  12 . The pivoting axis X of the bevel bracket  12  (also of the blade  10 ) coincides with the central axis of the central hole  22 . Left and right cam slots  24  and  26  are formed through the cam plate  20  and extending between the top and bottom sides of the cam plate  20 . The cam slots  24  and  26  are symmetrical to each other with respect to a symmetrical line extending through the center of the central hole  22 . Each of the cam slots  24  and  26  is formed in a way that the distance between it and the symmetrical line increases as it extends from its upper end to its lower end. That is to say, the lower ends of the cam slots  24  and  26  are spaced apart longer than their upper ends. 
         [0036]    The left and right guide members  14  and  16  are mounted in the elongated opening  8  at their outer portions. For example, as shown in  FIG. 4 , there are engaging structures formed on the edges of the base plate  1  which delimit the elongated opening  8  and the adjoining outer portions of the guide members  14  and  16  respectively, so that the guide members  14  and  16  are engaged with and thus fixed to the edges of the base plate  1 . Other mounting methods, such as by screw, can be used for mounting the guide members  14  and  16  to the base plate  1 . The inner portions of the guide members  14  and  16  are each formed with a guiding structure for guiding a corresponding one of the slides  30  and  40  to move in a left-right direction in the base plane. 
         [0037]    The left and right slides  30  and  40  are movably mounted to the left and right guide members  14  and  16  respectively. To this end, the outer portions  32  and  42  of the slides  30  and  40  are formed with guided structures which will be guided by the guiding structures of the guide members  14  and  16  respectively. In the embodiment shown in  FIG. 4 , rectangular guiding slots are opened into the inner portions of the guide members  14  and  16 , and rectangular guided blocks are formed as the outer portions of the slides  30  and  40  and slidably inserted into the guiding slots of the guide members  14  and  16  respectively. However, other guiding structures known in the art may be used for guiding the movements of the slides  30  and  40 . 
         [0038]    The slides  30  and  40  are movable under the guide of the guide members  14  and  16  in the left-right direction, which direction being perpendicular to the pivoting axis X (the central axis of the central hole  22 ) and parallel to the base plane. 
         [0039]    When mounted to the guide members  14  and  16 , a gap is formed between the opposing ends of the slides  30  and  40  which face each other. 
         [0040]    As shown in  FIG. 6 , the inner portion  34  (right portion) of the left slide  30  comprises a vertical upper portion  38  and an slanted lower portion  36  which forms a surface facing toward the lower-right direction, and the inner portion  44  (left portion) of the right slide  40  comprises a vertical lower portion  48  and an slanted upper portion  46  which forms a surface facing toward the upper-left direction. When the slides  30  and  40  are assembled, the vertical upper portion  38  and the slanted lower portion  36  oppose to the slanted upper portion  46  and the vertical lower portion  48  respectively, with the above mentioned gap formed therebetween. 
         [0041]    The slides  30  and  40  are each formed with a cylindrical protrusion  35  or  45  at their rear ends. In the assembled state of the slides  30  and  40 , their protrusions  35  and  45  insert into the cam slots  24  and  26  respectively, so that, under the camming action of the cam slots  24  and  26 , the protrusions  35  and  45  drive the slides  30  and  40  to move with respect to the base plate  1  under the guide of the guide members  14  and  16 . 
         [0042]    The cam plate  20  is fixed to the bevel bracket  12  in an orientation such that, in the normal vertical orientation of the blade  10 , the protrusion  35  of the left slide  30  inserts in the left cam slot  24  near the upper end of the left cam slot  24 , the protrusion  45  of the right slide  40  inserts in the right cam slot  26  near the lower end of the right cam slot  26 , and the slides  30  and  40  are in their right-most position. 
         [0043]    The protrusions  35  and  45  are formed on the slides  30  and  40  in such locations that, when the slides  30  and  40  are assembled in place, the outcoming section of the blade  10  can pass through the gap formed between the slides  30  and  40 . 
         [0044]    When the bevel bracket  12  and blade  10  pivot around the pivoting axis X (the central axis of the central hole  22 ) for reaching the tilting angle θ of the blade  10  from its vertical orientation (in a clockwise direction in  FIG. 4 ), the protrusion  35  moves in the left cam slot  24  toward the lower end of it while the protrusion  45  moves in the right cam slot  26  toward the upper end of it. Since each of the cam slots  24  and  26  is formed in a way that the distance between it and the symmetrical line increases as it extends from its upper end to its lower end as described above, the movements of the protrusions  35  and  45  in the cam slots  24  and  26  cause the slides  30  and  40  move to the left, as shown in  FIG. 7 . 
         [0045]    It can be understood that, when the bevel bracket  12  pivots to return the blade  10  back to its vertical orientation (in an anti-clockwise direction in  FIG. 4 ), the slides  30  and  40  move in a reverse manner, that is, to the right. 
         [0046]    Thanks to the slanted lower portion  36  of the left slide  30  and the slanted upper portion  46  of the right slide  40 , in the oblique orientation of the blade  10 , there are still narrow but enough distances between the blade and the slides  30  and  40  without contacting between them. During bevel cutting operation of the saw, chips will flow through the gap between the opposing ends of the slides  30  and  40 , but the flowing directions of the ships will change, as shown by the arrows in  FIG. 8 , and flowing speed of the chips will be reduced, which help to prevent the chips from splintering toward the operator. 
         [0047]    The above embodiments describe a slide driving means formed by a cam plate with double cam slots for driving the slides. Other slide driving means for driving the slides moving in the same direction can also be used in the anti-splinter device of the invention.  FIGS. 9-11  show some embodiments of the slide driving means. 
         [0048]      FIG. 9  shows a single cam design of the anti-splinter device in which a single cam  50  is fixed to the bevel bracket  12  at the pivoting axis X of the bevel bracket  12  and the blade  10 , and thus is pivotable around the pivoting axis X together with the bevel bracket  12  and the blade  10  for driving the left and right slides  30  and  40 . Opposing ends of the left and right slides  30  and  40  each has a slanted portion facing to the upper-inner direction. The saw blade  10  inserts through the gap formed between the opposing ends of the slides  30  and  40 . The tip end of the cam  50 , which forms a cam surface, abuts against the inner side of a vertical abutting portion  54  of the left slide  30 . The slides  30  and  40  are coupled with each other via a connecting means  52 , for example a connection bar, so as to be move jointly with each other. 
         [0049]    When the bevel bracket  12  pivots for reaching the tilting angle θ of the blade  10  from its vertical orientation, the cam  50  pushes the left slide  30  to move to the left, and the right slide  40  follows the movement of the left slide  30  by means of the connecting means  52 . A returning means is provided for moving the slides  30  and  40  to the right when the bevel bracket  12  pivots for returning the blade  10  back to its vertical orientation. For example, the returning means may be a compression spring  56  disposed between a portion of the base plate  1  and the outer side of the abutting portion  54 . 
         [0050]    In the embodiment shown in  FIG. 9 , the abutting portion  54  is formed on the left slide  30 , and the cam  50  and the spring  56  drive the slides to move to the left and right respectively. It can be understood that, however, the abutting portion  54  may be formed on the right slide  40 , and the cam  50  and the spring  56  drive the slides to move to the right and left respectively. 
         [0051]    Alternatively, the spring  56  may be an extension spring for achieving the same function. Still alternatively, the returning means may be formed by other elastic materials or other mechanisms. 
         [0052]      FIG. 10  shows a sliding lever design of the anti-splinter device in which a sleeve  60  is fixed to the bevel bracket  12  at the pivoting axis X of the bevel bracket  12  and the blade  10 , and thus is pivotable around the pivoting axis X together with the bevel bracket  12  and the blade  10 . A sliding lever  62  is slidably inserted through the sleeve  60 . When the sleeve  60  pivots along with the bevel bracket  12 , the sliding lever  62  pivots along with the sleeve  60  and slides in the sleeve  60 . Left and right slides  30  and  40  are coupled with each other via a connecting means  64 , for example a connection bar, so as to be move jointly with each other. Opposing ends of the left and right slides  30  and  40  each has a slanted portion facing to the upper-inner direction. The lower end of the sliding lever  62  is operatively connected with the connecting means  64 , so that, when the sliding lever  62  pivots, the sliding lever  62  drives the slides  30  and  40  to move to the left or right via the connecting means  64 . 
         [0053]      FIG. 11  shows a bar-linkage design of the anti-splinter device in which a pivot shaft  70  is fixed to the bevel bracket  12  at the pivoting axis X of the bevel bracket  12  and the blade  10 , and thus is rotatable around the pivoting axis X together with the bevel bracket  12  and the blade  10 . The pivot shaft  70  is couple with each of the left and right slides  30  and  40  via a bar-linkage. Specifically, each bar-linkage comprises an active bar  72  ( 72 ′) which has one end that is fixed to the pivot shaft  70  and another end that is hinged to a first end of a link bar  74  ( 74 ′). A second end of the link bar  74  ( 74 ′) is hinged to the slide  30  ( 40 ). Thus, when the bevel bracket  12  pivots in clockwise direction, the bar-linkages drives the left and right slides  30  and  40  to move to the lift, and when the bevel bracket  12  pivots in anti-clockwise direction, the bar-linkages drives the left and right slides  30  and  40  to move to the right. Opposing ends of the left and right slides  30  and  40  are both straight vertical ends. 
         [0054]    Alternatively, only one of the left and right slides  30  and  40  is coupled with the pivot shaft  70  via a bar-linkage, and the slides  30  and  40  are coupled with each other via a connecting means. 
         [0055]    It is appreciated that, by choosing the lengths of the bars  72 ,  72 ′,  74  and  74 ′, the moving velocities of the left and right slides  30  and  40  can be set as desired. For example, the moving velocities of the left and right slides  30  and  40  may be substantially equal to each other, so that the width of the gap between them can be kept substantially constant. Alternatively, when the left and right slides  30  and  40  are moving to the left, the moving velocity of the left slide  30  may be a little higher than that of the right slide  40 , so that the width of the gap between them increases to accommodate the increasing tilting angle of the blade  10 . 
         [0056]    In all the embodiments described above, when the saw blade pivots (tilts), the slides of the anti-splinter device follow the tilting motion of the blade to move in conformity with the outcoming section of the blade, thus keeping small distances between the slides and the blade to prevent the chips from splashing from the workpiece as well as ensures a clear line of sight and convenient working condition for operators. Further, by providing the anti-splinter slides near the cutting area, the cutting quality can be improved.

Technology Classification (CPC): 1