Abstract:
A workpiece supporting device of a circular sawing machine includes a base frame for rotatably supporting a worktable and having an arcuate surface region which defines an angularly extending guiding route. A platform is disposed on and is movable along the guiding route, and has an upper mounting surface that cooperates with the worktable to support a workpiece. A tightening mechanism is displaceable between unmovable and movable positions, where the platform is brought into tight and loose engagements with the arcuate surface region. An actuator is coupled with the tightening mechanism is operable to displace the tightening mechanism. The platform is movable along the guiding route when the tightening mechanism is in the movable position such that the worktable is turnable within a relatively large angular range.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a circular sawing machine, more particularly to a workpiece supporting device of a circular sawing machine having a worktable that is turnable relative to a base frame within a relatively large angular range. 
         [0003]    2. Description of the Related Art 
         [0004]    Referring to  FIG. 1 , a conventional circular sawing machine  10  generally includes abase frame  11 , a turntable  12  rotatably mounted on the base frame  11 , and a circular saw unit  13  cantileveredly mounted over the turntable  12  and pivotably movable toward and away from the turntable  12 . The base frame  11  is provided with left and right platforms  111  for supporting a workpiece. Left and right fences  112  are supported respectively on the left and right platforms  111  for positioning the workpiece. The circular saw unit  13  has a circular saw blade  131  and a handle  132 . The turntable  12  includes a neck table portion  121  extending forwardly, and a locking member  122  disposed on a front end of the neck table portion  121 . In use, a user can grip the handle  132  to move the circular saw unit  13  downward to perform a cutting operation. 
         [0005]    The user can turn the turntable  12  to a desired angular position, tighten the locking member  122  to lock the turntable  12  at the desired angular position, and move the circular saw unit  13  toward the turntable  12  for cutting the workpiece. Thus, the turntable  12  is operable to cut the workpiece at different angular positions. However, since a left or right side of the neck table portion  121  will abut against the left or right platform  111  during a cutting operation so as to limit the angular adjustment of the turntable  12  to be within a range defined by the platform  111  and the neck table portion  121 , the angular cutting angles of the circular saw blade  131  relative to the workpiece are limited. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to provide a workpiece supporting device of a circular sawing machine in which a turntable for supporting a workpiece is rotatable relative to a base frame within a relatively large angular range. 
         [0007]    According to this invention, the workpiece supporting device of a circular sawing machine includes a base frame having a major wall to which a central axis is normal. An upper major wall surface of the major wall has a central area which supports a worktable, a frontward surface region which extends radially and outwardly from the central area, and an arcuate surface region which extends rearwardly from the frontward surface region. The arcuate surface region defines a guiding route extending angularly about the central axis. A platform is disposed to be movable along the guiding route so as to turn about the central axis, and has an upper mounting surface that cooperates with an upper table surface of the worktable to support a workpiece. A tightening mechanism is disposed to be displaceable between an unmovable position, where the platform is brought into tight engagement with the arcuate surface region, and a movable position, where the platform is brought into loose engagement with the arcuate surface region. An actuator includes a shank rotatable relative to the base frame, an actuated end coupled with the tightening mechanism to displace the tightening mechanism from the unmovable position to the movable position to thereby permit the platform to be movable along the guiding route, and an operated end disposed to facilitate manual turning of the shank about the rotating axis. Preferably, the actuated end has a cam which is rotatably engaged with a cam follower of the tightening mechanism such that turning of the cam results in movement of the tightening mechanism relative to the platform so as to bring the platform into tight or loose engagement with said arcuate surface region. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which: 
           [0009]      FIG. 1  is a perspective view of a conventional circular sawing machine; 
           [0010]      FIG. 2  is an exploded perspective of the first preferred embodiment of a workpiece supporting device of a circular sawing machine according to this invention; 
           [0011]      FIG. 3  is a fragmentary exploded perspective view of a portion of the first preferred embodiment; 
           [0012]      FIG. 4  is a top view of the first preferred embodiment; 
           [0013]      FIG. 5  is a front view of the first preferred embodiment; 
           [0014]      FIG. 6  is a bottom view of the first preferred embodiment; 
           [0015]      FIG. 7  is a sectional view taken along lines VII-VII of  FIG. 6 , illustrating a tightening mechanism in an unmovable position; 
           [0016]      FIG. 8  is a sectional view taken along lines VIII-VIII of  FIG. 6 ; 
           [0017]      FIG. 9  is a sectional view taken along lines IX-IX of  FIG. 6 ; 
           [0018]      FIG. 10  is a top view illustrating a state in which a worktable is permitted to be turnable within a relatively large angular range; 
           [0019]      FIG. 11  is a sectional view similar to  FIG. 8 , illustrating the tightening mechanism in a movable position; 
           [0020]      FIG. 12  is a sectional view similar to  FIG. 9 , illustrating the tightening mechanism in the movable position; 
           [0021]      FIG. 13  is a sectional view of a portion of the second preferred embodiment according to this invention; and 
           [0022]      FIG. 14  is a sectional view taken along lines XIV-XIV of  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Referring to  FIGS. 2 to 6 , the first preferred embodiment of a workpiece supporting device of a circular sawing machine according to the present invention is shown to comprise a base  20 , a worktable  40 , left and right platforms  30 , left and right tightening mechanisms  50 , left and right actuators  60 , and left and right stopping units  70 . The circular sawing machine includes a circular saw unit (see  FIG. 1 ) that is cantileveredly mounted over the workpiece supporting device to be pivotably movable toward and away from the workpiece supporting device. 
         [0024]    The base  20  includes a base frame  21  and left and right mounts  22 . The base frame  21  has a major wall to which a central axis (X) is normal, and which has upper and lower major wall surfaces ( 21   a,    21   b ) opposite to each other in an upright direction. The upper major wall surface ( 21   a ) has a central area  215  which has a circumferential borderline  216  surrounding the central axis (X), a frontward surface region  211  which extends radially and forwardly of the circumferential borderline  216  and which angularly extends about the central axis (X), and left and right arcuate surface regions  212  which extend rearwardly from the frontward surface region  211 . Each of the arcuate surface regions  212  has an arcuate rail unit  213  including inner and outer arcuate rails that extend angularly about the central axis (X) and that are spaced apart from each other by an arcuate zone (A) and that serve as a guiding route  213 . 
         [0025]    The left and right mounts  22  respectively flank the left and right arcuate surface regions  212 . Each of the mounts  22  extends uprightly to form a sidewall segment  221  and a base segment  222  that rests on a flat surface, such as the surface of a workbench, a floor surface, etc., to suspend the respective arcuate surface region  212  from the flat surface such that the base segment  222  is disposed below the lower major wall surface ( 21   b ). 
         [0026]    The worktable  40  has an outer periphery  41  aligned with the circumferential borderline  216  and is superimposed on the central area  215 . The worktable  40  has an upper table surface  42  which defines a cutting line  43  that extends from the central axis (X) towards a foremost point of the frontward surface region  211 , and that serves as a reference for guiding movement of the circular saw unit toward the workpiece supporting device for cutting a workpiece. 
         [0027]    The left and right platforms  30  are movable along the arcuate rail units  213 , respectively, so as to turn about the central axis (X). Each of the platforms  30  has an upper mounting surface  31  that cooperates with the upper table surface  42  of the worktable  40  to support the workpiece, and a bottom frame  32  which is spaced apart from the upper mounting surface  31  and which includes a slidable arcuate web  321  that extends angularly about the central axis (X), that is made from a wear-resistant material, and that is guided to slide on the respective arcuate rail unit  213 . The slidable arcuate web  321  has an arcuate slot  322  which extends therethrough and which is aligned with the arcuate zone (A) in the upright direction. Each of the platforms  30  further has a force-focusing member  33  which is configured to resemble the slidable arcuate web  321  and has an arcuate slot  331  and which is superimposed upon the slidable arcuate web  321 . 
         [0028]    Each of the left and right tightening mechanisms  50  includes a bolt unit having two bolts  51 , an elongated washer body  52 , a cam follower  53 , a bearing member  54 , and two coil springs  55 . With reference to  FIGS. 7 and 8 , the bolts  51  are angularly spaced apart from each other, are engaged with the respective arcuate zone (A), and respectively extend in the upright direction through the arcuate slots  322 ,  331  to terminate at enlarged heads  511 , respectively. The bolts  51  are movable relative to the respective arcuate zone (A) and the respective slidable arcuate web  321  in the upright direction. The elongated washer body  52  has two through bores for extension of the bolts  51  therethrough, respectively, and are configured to force the respective force-focusing member  33  to abut against the respective slidable arcuate web  321 . The enlarged heads  511  of the bolts  51  are movable in the upright direction between a movable position, where the respective slidable arcuate web  321  is in loose engagement with the respective arcuate rail unit  213  so as to permit the respective platform  30  to slide along the respective guiding route, and an unmovable position, where a pressing force emanating from the enlarged heads  511  is focused by the elongated washer body  52  onto the respective slidable arcuate web  321  so as to bring the respective slidable arcuate web  321  into tight engagement with the respective arcuate rail unit  213 , thereby tightening the respective platform  30  on the respective arcuate surface region  212 . Furthermore, the bolts  51  extend downwardly to terminate at lower ends that are disposed below the lower major wall surface ( 21   b ) of the base frame  21 . The cam follower  53  interconnects the lower ends of the bolts  51  and has a follower surface  531  confronting the lower major wall surface ( 21   b ). The bearing member  54  interconnects and is movable relative to the lower ends of the bolts  51  in the upright direction, and has a bearing surface  541  confronting the follower surface  531 . The coil springs  55  are respectively sleeved on the lower ends of the bolts  51 , and are disposed between the lower major wall surface ( 21   b ) and the bearing member  54  so as to bias the bearing member  54  downwardly and away from the lower major wall surface ( 21   b ). 
         [0029]    Each of the left and right actuators  60  includes a shank  61 , an actuated end  62 , an operated end  63 , and a torsion spring  64 . The shank  61  is rotatably mounted in the base segment  222  of the respective mount  22  about a rotating axis (R), and extends along the rotating axis (R). The actuated end  62  is disposed inwardly of the shank  61 , and has a cam  621  which is frictionally engaged with and which is rotatably interposed between the follower and bearing surfaces  531 ,  541  to be turned with the shank  61  about the rotating axis (R). The operated end  63  extends from the shank  61  and outwardly of the base segment  222  of the respective mount  22 , and has a handle  631  to facilitate manual turning of the cam  621  about the rotating axis (R). The torsion spring  64  has two ends respectively engaging the shank  61  and the lower major wall surface ( 21   b ). The handle  631  has a bent portion  632  for manual operation by the user, and a protrusion  633  facing the base segment  222  of the respective mount  22 . 
         [0030]    With reference to  FIGS. 3 and 9 , each of the left and right stopping units  70  includes front and rear stoppers  71  which are disposed on the base segment  222  of the respective mount  22  such that the protrusion  633  is stopped by the stoppers  71  during operation of the handle  631  so as to limit the extent of turning of the operated end  63  about the rotating axis (R). 
         [0031]    Referring to  FIGS. 7 ,  8  and  9 , when one of the left and right tightening mechanisms  50  is in the unmovable position, the respective handle  631  is operable to cause the protrusion  633  to abut against the front stopper  71 . At this stage, the cam follower  53  and the bearing member  54  are moved away from each other in the upright direction by the cam  621  such that the bolts  51  are moved downwardly to bring the slidable arcuate web  321  into tight engagement with the arcuate rail unit  213 , and the bearing member  54  is in tight engagement with the lower major wall surface ( 21   b ) so as to secure the respective platform  30  on the respective arcuate surface region  212 . 
         [0032]    Referring to  FIGS. 10 ,  11  and  12 , when it is desired to increase the turning angle of the worktable  40 , the handle  631  of the left and right actuators  60  is turned to permit the protrusion  633  to abut against the rear stopper  71 . At this stage, the respective tightening mechanism  50  is displaced to the movable position. Specifically, the bolts  51  are moved to bring the slidable arcuate web  321  into loose engagement with the arcuate rail unit  213 , and the bearing member  54  is moved away from the lower major wall surface ( 21   b ) by means of the coil springs  55 , thereby permitting the respective platform  30  to be movable along the guiding route  213 .  FIG. 10  illustrates the state in which the worktable  40  has a largest turning angle. 
         [0033]    Referring to  FIGS. 13 and 14 , the second preferred embodiment of a workpiece supporting device according to this invention is similar to the first embodiment in construction, except that, in this embodiment, the lower major wall surface ( 21   b ) of the base frame  21  has two support ribs  217  such that the shank  61  is supported on the support ribs  217 , and two coil springs  56  are respectively sleeved on the lower ends of the bolts  51 , and are disposed between the lower major wall surface ( 21   b ) and the cam follower  53  to bias the cam follower  53  downwardly and away from the lower major wall surface ( 21   b ). 
         [0034]    While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.