Abstract:
A supporting device is adapted for mounting a protective cover to shield a cutting blade of a cutting machine, and includes a mount unit with a proximate tightening surface, a tightening bolt passing through the proximate tightening surface, a supporting frame adapted for holding the protective cover and having a guiding slot for passage of the tightening bolt so as to be movable between a position of use and a retreat position, a movable tightening member with a distal tightening surface and a cam follower surface, a cam actuating member having a cam surface mating with the cam follower surface and turnable to tighten or loosen the supporting frame, and a biasing member disposed to keep the actuating body in a tightening position.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a supporting device for mounting a protective cover to shield a cutting blade of a cutting machine, more particularly to a supporting device which is easily operated to be tightened firmly to a position of use or a retreat position. 
   2. Description of the Related Art 
   In a conventional table cutting machine, such as a circular saw machine, a supporting device is disposed adjacent to a circular saw blade for mounting a protective cover to shield the circular saw blade. The supporting device is detachably disposed on a worktable so as not to obstruct specific working operation, such as cutting a slot in a workpiece. 
   Referring to  FIG. 1 , a conventional supporting device  10  includes a fixed mount unit  11 , a tightening mount unit  12  movably disposed on the fixed mount unit  11 , and a control unit  13  disposed between the fixed and tightening mount units  11 , 12 . The fixed mount unit  11  has a fixed mount  111  secured on a tabletop (not shown) of a cutting machine. The fixed mount  111  has a sliding slot  112  in a side thereof for fitting of a tightening mount unit  12 . The tightening mount unit  12  has a tightening plate  121  which is fitted to the sliding slot  112 , a cam follower piece  122  which is embedded into the tightening plate  121 , and a limiting pin  123  which extends outwardly of the tightening plate  121 . The control unit  13  has a tightening bolt  131 , a cam piece  132  which meshes with the cam follower piece  122 , a handgrip  133  which extends radially from the cam piece  132 , and a limiting protrusion  134  which is disposed on the cam piece  132  to abut against the limiting pin  123 . A clearance is present between the tightening plate  121  and a side of the fixed mount  111  for accommodating a lower portion of a supporting frame  1 . An upper portion of the supporting frame  1  is adapted to hold a protective cover (not shown). When the user operates the handgrip  133  to rotate the cam piece  132 , the cam follower piece  122  is pressed toward the fixed mount  111  so as to tighten the supporting frame  1  for positioning the protective cover on the cutting machine. However, the cam piece  132  may be rotated to cause movement of the cam follower piece  122  away from the tightening plate  121  when the machine is vibrated during the cutting operation, thereby resulting in undesired detachment of the supporting frame  1  from the tightening mount unit  12 . 
   Referring to  FIG. 2 , another supporting device  20  includes a mounting unit  21 , a supporting frame unit  22  and a control unit  23 . The mounting unit  21  has a fixed mount  211  and a tightening plate  212 . The supporting frame unit  22  has a supporting frame  221  which is disposed between the fixed mount  211  and the tightening plate  212 , and which has an arcuate slot  2211 . The control unit  23  has a tightening bolt  231  which extends through the arcuate slot  2211  and into the fixed mount  211 , two washers  232  which are sleeved on the tightening bolt  231 , a guide pin  233  which is disposed on the tightening bolt  231 , and a cam actuator  234  which is sleeved on the tightening bolt  231  at one end thereof, and which has a handgrip at the other end. The cam actuator  234  has a spirally extending groove  2341  which surrounds the tightening bolt  231  for guiding movement of the guide pin  233 . Thus, when the user rotates the cam actuator  234 , the cam actuator  234  can press the tightening plate  212  via the washers  232  towards the fixed mount  211  so as to tighten the supporting frame  221 . However, undesired loosening of the supporting frame  221  may occur after a long-term use. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to provide a supporting device which is easily operated to be tightened firmly to a position of use or a retreat position relative to a cutting machine. 
   According to this invention, the supporting device includes a mount unit which is adapted to be secured to a cutting machine. The mount unit includes a major abutment wall which has a proximate tightening surface that has an axial hole extending therethrough along a tightening axis. A tightening bolt has a shank which passes through the axial hole, and which has front and rear ends, and an intermediate segment. A supporting frame has an upper end which is adapted to hold a protective cover, and a middle segment which has proximate and distal tightened major surfaces opposite to each other along the tightening axis, and a guiding slot that extends through the proximate and distal tightened major surfaces to permit passage of the shank therethrough such that the middle segment is movable between a position of use where the shank is remote from the upper end, and a retreat position where the shank is closer to the upper end. A movable tightening member is sleeved on the shank, and has a thrust major wall which has a distal tightening surface to press the distal tightened major surface of the supporting frame so as to force the proximate tightened major surface to abut against the proximate tightening surface of the mount unit. The thrust major wall further has a cam follower surface which is opposite to the distal tightening surface, and which has first and second pressed areas that are angularly displaced from each other about the tightening axis, and that are respectively proximate to and distal from the distal tightening surface along the tightening axis. A cam actuating member includes an actuating body and a handgrip. The actuating body is sleeved on the shank, and has a cam surface and an outmost major surface opposite to each other. The cam surface has first and second pressing spots which are angularly displaced from each other about the tightening axis such that the first and second pressing spots are brought into contact with the first and second pressed areas respectively when the cam surface is brought to mate with the cam follower surface in a loosened position, and such that, when the actuating body is turned about the tightening axis to a tightening position, the first pressing spot is displaced to contact the second pressed area with an axial frictional force so as to move the distal tightening surface to press the distal tightened major surface, thereby forcing the proximate tightened major surface to abut against the proximate tightening surface. The handgrip extends from the actuating body radially so as to turn the actuating body about the tightening axis between the loosened and tightening positions. A biasing member is disposed on the shank adjacent to the rear end of the shank such that, as a result of displacement of the actuating body to the tightening position, the biasing member acquires an increment of a biasing force which biases the front end of the shank towards the supporting frame so as to counteract the axial frictional force to thereby keep the actuating body in the tightening position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings, in which: 
       FIG. 1  is a perspective view of a conventional supporting device; 
       FIG. 2  is a perspective view of another conventional supporting device; 
       FIG. 3  is an exploded perspective view of a preferred embodiment of a supporting device according to this invention; 
       FIG. 4  is a perspective view of the preferred embodiment when assembled on a cutting machine; 
       FIG. 5  is a fragmentary schematic side view showing a supporting frame of the preferred embodiment in a position of use; 
       FIG. 6  is a sectional view of the preferred embodiment taken along lines  6 - 6  of  FIG. 5  and showing a cam actuating member in a loosened position; 
       FIG. 7  is a fragmentary schematic side view showing the supporting frame in a retreat position; 
       FIG. 8  is a sectional view of the preferred embodiment taken along lines  8 - 8  of  FIG. 7  and showing the cam actuating member in a tightening position; 
       FIG. 9  is an exploded perspective view of another preferred embodiment of a supporting device according to this invention; 
       FIG. 10  is a sectional view of the preferred embodiment shown in  FIG. 9  when a cam actuating member is in a loosened position; and 
       FIG. 11  is a sectional view of the preferred embodiment shown in  FIG. 9  when the cam actuating member is in a tightening position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 5 , a preferred embodiment of a supporting device according to the present invention is adapted to be mounted on a cutting machine  100 , such as a table saw machine. The cutting machine  100  includes a machine body  101 , a worktable  102  mounted on the machine body  101 , a drive motor  103  mounted in the machine body  101 , and a circular saw blade  104  mounted axially on the drive motor  103  to be driven to rotate about a rotating axis. The circular saw blade  104  has a working part that extends outwardly of the worktable  102  for working a workpiece (not shown) supported on the worktable  102 . With reference to  FIGS. 3 ,  4  and  6 , the supporting device of this embodiment is shown to comprise amount unit  30 , a tightening bolt  80 , a supporting frame  40 , a movable tightening unit  50 , and a biasing member  60 . 
   The mount unit  30  includes an elongated fixed mount  30  which is adapted to be secured to the drive motor  103  at a left end thereof, and which has a throughbore  312  at a right end  311  thereof. The throughbore  312  defines a tightening axis parallel to the rotating axis of the saw blade  104 . The mount unit  30  further includes a movable mount  32  which has a major abutment wall  320  that is disposed forwardly of the right end  311  of the fixed mount  31  along the tightening axis, and that has an elongated axial hole  323  extending therethrough and coaxial with the throughbore  312 . The major abutment wall  320  has a proximate tightening surface  326  facing forwardly. 
   The movable mount  32  has an anchoring wall  327  which extends rearwardly from an upper edge of the major abutment wall  320 , and which has a pair of positioning holes  322  that extend therethrough and that are elongated in a longitudinal direction parallel to the tightening axis. A pair of first screw fasteners  35  are disposed to respectively extend through the positioning holes, and are respectively and threadedly engaged with two screw holes  313  in the fixed mount  31 . Thus, the position of the movable mount  32  relative to the fixed mount  31  in the longitudinal direction is adjustable by movement of the first screw fasteners  35  in the positioning holes  322  in the longitudinal direction. In addition, a second screw fastener  34  is threadedly engaged with a screw hole  321  in a center of the anchoring wall  327  and extends to abut against the fixed mount  31  so as to generate a depressing force to render an angular position of the major abutment wall  320  of the movable mount  32  relative to the fixed mount  31  adjustable by virtue of varying the depression force. Thus, the longitudinal and angular positions of the supporting frame  40  can be corrected to be in line with the saw blade  104 . 
   Further, the major abutment wall  320  of the movable mount  32  has two limiting pins  324  and two retaining pins  325  which extend from the proximate tightening surface  326  and which are disposed upwardly, downwardly, leftwardly and rightwardly of the axial hole  323 , respectively. 
   The tightening bolt  80  has a shank  81  which is configured to pass through the axial hole  323  and the throughbore  312 , and which has front and rear ends  811 , 812  opposite to each other in the tightening axis, and an intermediate segment  813  that is interposed between the front and rear ends  811 , 812  and that has a non-circular cross-section so as to be movable relative to the major abutment wall  320  along the tightening axis. The tightening bolt  80  further has a screw nut  82  which is threadedly engaged with the rear end  812  of the shank  81 , and a flexible joint  83  which is received in the throughbore  312 , which is sleeved on the intermediate segment  813  of the shank  81  between the screw nut  82  and the major abutment wall  320  of the movable mount  32 , and which has an accommodation chamber  831 . 
   The supporting frame  40  has upper and lower ends  42 , 43  opposite to each other, and a middle segment  41  interposed between the upper and lower ends  42 , 43 . The upper end  42  is adapted to hold a protective cover (not shown). The middle segment  41  has proximate and distal tightened major surfaces  414 , 415  opposite to each other along the tightening axis, and an arcuate guiding slot  411  which extends through the proximate and distal tightened major surfaces  414 , 415  and which permits passage of the shank  81  therethrough. The middle segment  41  further has two upper retaining holes  413  and two lower retaining holes  412  proximate to the upper and lower ends  42 , 43 , respectively. The guiding slot  411  is configured to permit the middle segment  41  to be movable between a position of use, as shown in  FIG. 5 , where the shank  81  is remote from the upper end  42 , and where the lower retaining holes  412  engage the retaining pins  325  so that the lower limiting pin  324  reaches a lowermost area of the guiding slot  411 , and a retreat position, as shown in  FIG. 7 , where the shank  81  is closer to the upper end  42 , and where the upper retaining holes  413  engage the retaining pins  325  so that the upper limiting pin  324  reaches an uppermost area of the guiding slot  411 . By means of the upper and lower retaining holes  413 , 412  and the retaining pins  325  that serve as a retaining unit, the supporting frame  40  can be retained in a corresponding one of the position of use and the retreat position. 
   The movable tightening unit  50  includes a movable tightening member  51  and a cam actuating member  52 . The movable tightening member  51  is sleeved on the intermediate segment  813  of the shank  81 , and has a thrust major wall  511  to which the tightening axis is normal. The thrust major wall  511  has a distal tightening surface  512  which confronts and which is to be brought to press the distal tightened major surface  415  so as to force the proximate tightened major surface  414  to abut against the proximate tightening surface  326 , and a cam follower surface  513  which is opposite to the distal tightening surface  512  along the tightening axis, and which is of a wedge shape. Specifically, as shown in  FIGS. 6 and 8 , the cam follower surface  513  has first and second pressed areas ( 513   a , 513   b ) which are angularly displaced from each other about the tightening axis, and which are respectively proximate to and distal from the distal tightening surface  512  along the tightening axis. In addition, the movable tightening member  51  further has left and right limited pins  514  which are disposed on the thrust major wall  511  at an outer periphery of the cam follower surface  513  and which are radially opposite to each other. 
   The cam actuating member  52  includes an actuating body  521  and a handgrip  53 . The actuating body  521  is sleeved on the intermediate segment  813  of the shank  81 , and has a cam surface  522  and an outmost major surface  523  opposite to each other in the tightening axis to abut against the front end  811  of the shank  81 . The cam surface  522  is of a wedge shape. Specifically, as shown in  FIGS. 6 and 8 , the cam surface  522  has first and second pressing spots ( 522   a , 522   b ) which are angularly displaced from each other about the tightening axis such that, the first and second pressing spots ( 522   a , 522   b ) are brought into contact with the first and second pressed areas ( 513   a , 513   b ), respectively, when the cam surface  522  is brought to mate with the cam follower surface  513  in a loosened position (as shown in  FIG. 6 ), and such that, when the actuating body  521  is turned about the tightening axis to a tightening position (as shown in  FIG. 8 ), the first pressing spot ( 522   a ) is displaced to contact the second pressed area ( 513   b ) with an axial frictional force so as to move the distal tightening surface  512  to press the distal tightened major surface  415 , thereby forcing the proximate tightened major surface  414  to abut against the proximate tightening surface  326 . The handgrip  53  is disposed to extend from the actuating body  521  radially so as to turn the actuating body  521  about the tightening axis between the loosened and tightening positions. In addition, the actuating body  521  further has a limiting pin  524  which is disposed at an outer periphery thereof and which abuts against a corresponding one of the left and right limited pins  514  so as to restrict turning of the actuating body  521  within a certain range. 
   The biasing member  60  is a coil spring  60  in this embodiment. The coil spring  60  is disposed to surround the shank  81 , and has an end abutting against the major abutment wall  320 , and an opposite end which is received in the accommodation chamber  831  in the flexible joint  83 . Thus, the coil spring  60  acquires a biasing force which urges the tightening bolt  80  and the movable tightening unit  50  rearwardly so as to force the middle segment  41  of the supporting frame  40  to abut against the proximate tightening surface  326 . Moreover, the biasing force of the coil spring  60  is adjustable by threaded movement of the screw nut  82  while being kept in line with the tightening axis. Furthermore, as a result of displacement of the actuating body  521  to the tightening position, as shown in  FIG. 8 , the coil spring  60  is being compressed to acquire an increment of the biasing force which can bias the front end  811  of the shank  81  towards the supporting frame  40  so as to counteract the axial frictional force to thereby keep the actuating body  521  in the tightening position. 
   As illustrated, the supporting frame  40  can be tightened firmly in the tightening position so as to hold a protective cover (not shown) against vibration of the cutting machine  100  during a cutting operation. In addition, by operating the handgrip  53  to turn the actuating body  521  about the tightening axis, the supporting frame  40  can be easily tightened to and loosened from the movable mount  32  such that the supporting frame  40  can be moved to a corresponding one of the position of use and the retreat position when being loosened. Furthermore, by means of the retaining unit, i.e., the retaining pins  325  and the retaining holes  413 , 412 , the supporting frame  40  can be retained in the corresponding one of the position of use and the retreat position. 
   Alternatively, referring to  FIGS. 9 to 11 , in another preferred embodiment of the supporting device according to this invention, instead of the coil spring  60 , the biasing member  70  includes two spring disks  73  which are sleeved on the shank  81  and which are configured to be squeezable between the major abutment wall  320  and the screw nut  82  so as to acquire the increment of the biasing force. In addition, instead of the flexible joint  83 , the tightening bolt  80  has an elastic washer  84  which is interposed between the screw nut  82  and one of the spring disks  73  so as to facilitate restoration of the spring disks  73  to their unsqueezed state once the actuating body  521  is displaced to the loosened position. 
   While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.