Abstract:
A sawing machine has a casing, a moveable cover and a saw blade both pivotally mounted inside the casing. Two block rings are respectively mounted at two lateral sides of a pivoted portion of the moveable cover for preventing sawing chips generated by the saw blade sawing a workpiece in a sawing procedure from entering the pivoted portion of the moveable cover.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a machine tool, and more particularly to a sawing machine having an assembly for dustproof. 
     2. Description of the Related Art 
     FIG. 1 shows a conventional sawing machine mainly having a casing  1 , a transmission assembly  2 , a movable cover  3  and a saw blade  4 . The transmission assembly  2  has a motor  2   a  mounted at an outer side of the casing  1 , a bearing mount  2   b  mounted at an inner side of the casing  1  and a transmission shaft  2   c  running through the bearing mount  2   a , wherein the bearing mount  2   b  has an axle  2   d  projected out, the movable cover  3  has an annular rim  3   a  and an arched block plate  3   b  to engage the rim  3   a  with the axle  2   d  so that the movable cover  3  swings with the axle  2   d  to be the center of rotation. The saw blade  4  connects with the transmission shaft  2   c  and has a part thereof covered by the block plate  3   b . A separating device  5  is provided in between the movable cover  3  and saw blade  4  to keep the saw blade  4  running smoothly. When the sawing machine is cutting a specific object A, as shown in FIG. 2, the movable cover  3  has its front end in contact with the object A and moves along with it. In the meantime of the object A running forwardly, the movable cover  3  swings backwardly so that the movable cover  3  always can block the chips of the object A being sawn. 
     It is always occurred in the conventional sawing machine that the chips run into the space between the rim  3   a  and the axle  2   d  and are accumulated therein to make the movable cover  3  can not swing smoothly. Beside that, the movable cover was made of aluminum so that while a metal object was sawn by the machine, the metal chips accumulated in between the rim and the axle damage the movable cover frequently. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a sawing machine having a dustproof assembly to block the sawing chips so that the movable cover always works correctly in sawing procedures. 
     According to the objective of the present invention, a sawing machine comprises a casing having a chamber therein, an axle hole at a side thereof and an opening at a bottom thereof. Both of the axle hole and the opening communicate with the chamber. A transmission assembly has a bearing mount mounted at an inner side of the casing having a base board and an axle projected from a side of the base board, a transmission shaft running through the bearing mount and the axle hole and a power resource for driving the transmission shaft to rotate. A movable cover has an annular rim and a block plate, wherein the rim has an inner annular face, an inner face and an outer face and is engaged with the axle of the bearing mount so that the movable cover swings around the axle which serves as a center of rotation. A first block ring is installed in between the bearing mount and the movable cover, wherein the first block ring is attached to the base board of the bearing mount and the rim of the movable cover respectively. A block device is provided at an outer side of the movable cover and has a mask and a second block ring, wherein the mask has a first hole for the transmission shaft running therethrough and the second block ring has opposite sides attached to the outer face of the rim of the movable cover and the mask respectively, and a saw blade is fastened at a distal end of the transmission shaft and is located at an outer side of the block device, wherein the saw blade has a part thereof extruded out of the casing via the opening and the extruded part thereof are covered by the block plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a conventional sawing machine; 
     FIG. 2 is a front view of the conventional sawing machine, showing a specific object being sawn; 
     FIG. 3 is an exploded view of a preferred embodiment of the present invention; 
     FIG. 4 is an enlarged exploded view of partial elements of the preferred embodiment of the present invention; 
     FIG. 5 is a perspective of the elements shown in FIG. 4 being assembled; 
     FIG. 6 is a sectional view of FIG. 5, and 
     FIG. 7 is similar to FIG. 6, showing a slot on the outer side of the rim of the movable cover. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIGS. from FIG. 3 to FIG. 6, a sawing machine  100  of the preferred embodiment of the present invention mainly comprises a casing  10 , a transmission assembly  20 , a sheath  30 , a first block ring  40 , a movable cover  50 , an annular piece  60 , a block device  70  and a saw blade  80 . 
     The casing  10  has a chamber  11  therein, an axle hole  12  at an inner side and an opening  13  at a bottom, and both of the axle hole  12  and the opening  13  are communicated with the chamber  11 . The casing  10  further has two thread holes  14  beside the axle hole  12 . 
     The transmission assembly  20  includes a bearing mount  21 , a transmission shaft  22 , a gear  23  for deceleration and a motor  24  as a power resource. The bearing mount  21  has a base board  211 , an axle  212  projected from a side of the base board  211 , three thread holes  213  at a distal end of the axle  212  and two through holes  214  at the base board  211 . The bearing mount  21  is firmly secured on the casing  10  via two bolts  25  running through the through holes  214  and screwed into the thread holes  14  on the casing  10 . The transmission shaft  22  runs through the bearing mount  21  and the axle hole  12 . The gear  23  connects with the transmission shaft  22  at an end thereof and is received in the axle hole  12 . The motor  23  drives the transmission shaft  22  rotating via the gear  23 . 
     The sheath  30  is made of metal having a ring portion  31  with a diameter substantially equal to a diameter of the axle  212  and a flange portion  32  radially projected from an end of the ring portion  31 . 
     The first block ring  40  is made of rubber having an annular portion  41  and a lip portion  42  projected from an edge of the annular portion  41  for dustproof. As shown in FIG.  3  and FIG. 6, the first block ring  40  is installed in between the bearing mount  21  and the sheath  30 . The ring portion  31  of the sheath  30  is engaged with the axle  212 . The flange portion  32  is attached to the base board  211  by the annular portion  41  of the first block ring  40  pressing it. The lip portion  42  of the first block ring  40  faces outwardly. 
     The movable cover  50  is made of aluminum having an annular rim  51 , a side plate  52  and an arched block plate  53 , wherein the annular rim  51  has an inner annular face  511  , an inner face  512 , an outer face  513  and a step portion  514  on the outer face  513 . The annular piece  60  is made of metal initially installed in the annular rim  51  as shown in FIG.  6 . The annular rim  51  is engaged with axle  212  in the bearing mount  21  and the annular piece  60  is located at between the inner annular face  511  of the annular rim  51  and the ring portion  31  of the sheath  30 . The lip portion  42  of the first block ring  40  is attached to the step portion  514  so that the movable cover  50  swings with the axle  212  to be a center of rotation. 
     The block device  70  consists of a mask  71  and a second block ring  72 , wherein the mask  71  has a first hole  711  and three second holes  712  and the second block ring  72  is a rubber ring covering an edge of the mask  71 . The second block ring  72  has a lip portion  721  at the edge of the mask  71  as shown in FIG.  5 . The block device  70  is firmly secured at an outer side of the movable cover  50  with the lip portion  721  attached to the outer face  513  of the annular rim  51  via three bolts  73  running through second holes  712  and screwed into the thread holes  213  of the bearing mount  21  respectively. The transmission shaft  22  is extruded out of the block device  70  via the first hole  711  as shown in FIG.  6 . It has to be mentioned that the assembled block device  70  does not interfere with the motion of the movable cover  50 . 
     The saw blade  80  connects with the transmission shaft  22  at an end extruded out via the first hole  711 . The saw blade  80  has two separating device  90  to keep the saw blade  80  running smoothly. The saw blade  80  has a part thereof extruded out of the casing  10  via the opening  13  and the extruded part thereof is covered by the block plate  53 . 
     The main character of the present invention is to provide the rubber first and second block rings  40  and  72 , as shown in FIG. 6, at between the movable cover  50  and the axle  212  which the lip portions  42  and  721  are attached to opposite sides of the annular rim  51  of the movable cover  50  so that chips of an object sawn by the saw blade  80  are blocked thereby under a condition of without interfering with the motions of the saw blade  80  and the movable cover  50 . An alternate structure is that rubber washers (not shown) are installed in between the opposite sides of the annular rim  51 , the base board  211  and the mask  71  respectively. Another alternate structure is that the sheath  30  made of a metal piece and the annular piece  60  are provided in between the annular rim  51  and the axle  212 . The capacities of smaller friction and wearproof of the sheath  30  and the annular piece  60  make movable cover  50  swinging more smoothly and prevent the portion of the movable cover  50  adjacent to the axle  212  from wearing. 
     As shown in FIG. 7, the movable cover  50  is provided with a slot  515  at the outer face  513  of the annular rim  51  to receive the lip portion  721  of the second block ring  72  therein that make the sawing machine of the present invention having more capacity of blocking the sawing chips.