Abstract:
A sawing machine has a cutting angle adjustment mechanism for adjusting the cutting angle of a saw blade. The adjustment mechanism includes a handwheel for rotation by the user to bias a bracket on which a saw unit having the saw blade is mounted so as to further adjust the cutting angle of the saw blade, and a positioning member, which is rotatable between a first position to lock the bracket in position and stop the handwheel from biasing the bracket and a second position to allow operation of the handwheel to bias the bracket.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a sawing machine and more specifically, to a sawing machine having a cutting angle adjustment mechanism for controlling the cutting angle of the saw blade. 
   2. Description of the Related Art 
   Conventionally, a table saw uses a screw rod for controlling the tilting angle of a bracket to further adjust the cutting angle of the saw blade of the saw unit at the bracket. However, it takes much time and labor to rotate the screw rod to the desired position. 
   Nowadays, handwheel and gear transmission mechanisms are commonly used in table saws for adjusting the cutting angle of the saw blade conveniently with less effort. A handwheel and gear transmission mechanism for this purpose comprises an arched rack fixedly provided at the base of the table saw, a handwheel, which has a gear fixedly provided at one side for engaging the arched rack for allowing rotation of the handwheel to tilt the bracket that carries the saw unit, and a spring member provided between the bracket and the handwheel and adapted to force the gear of the handwheel away from the arched rack. When wishing to change the cutting angle of the saw blade of the saw unit, the operator must press the handwheel to force the gear of the handwheel into engagement with the arched rack, and then rotate the handwheel to bias the bracket. When released the hand, the spring member automatically pushes the handwheel away from the arched rack, keeping the bracket in the adjusted tilting angle. This design is functional; however, it is not safety in use. When the operator or another worker passes through one side of the table saw and touches the handwheel accidentally, the handwheel may be forced into engagement with the arched rack such that the handwheel will be rotated to change the tilting angle of the bracket. In this case, the operator shall have to correct the cutting angle of the saw blade of the saw unit again. 
   SUMMARY OF THE INVENTION 
   The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a sawing machine having a cutting angle adjustment mechanism, which prevents biasing of the tilting angle adjustment handwheel accidentally. 
   To achieve this object of the present invention, the sawing machine comprises a base and a cutting angle adjustment mechanism for adjusting the cutting angle of a saw blade. The cutting angle adjustment mechanism comprises a bracket on which a saw unit having the saw blade is mountable pivotally mounted inside the base, an axle coupled to the bracket, a handwheel movably coupled to the axle and provided with a gear at one side thereof, a screw rod coupled to the bracket, a toothed plate fixedly fastened to the base, located between the handwheel and the bracket and provided with a smoothly arched sliding slot through which the screw rod extends, and a rack for the engagement of the gear of the handwheel for allowing the bracket to be biased upon a rotary motion of the handwheel, and a positioning member fastened to the screw rod and provided with a stop flange turnable with the positioning member in and out of the space between the gear of the handwheel and the base. The stop flange prohibits engagement of the gear of the handwheel with the rack when it is turned with the positioning member into the space between the gear of the handwheel and the base. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of the preferred embodiment of the present invention. 
       FIG. 2  is a schematic sectional side view of a part of the preferred embodiment of  FIG. 1 . 
       FIG. 3  is a perspective view of the reinforcing plate and the toothed plate used in the preferred embodiment of the present invention. 
       FIG. 4  is similar to  FIG. 1  but showing the stop flange of the positioning member moved away from the space between the gear of the handwheel and the outside wall of the base. 
       FIG. 5  is a schematic sectional side view of a part of the preferred embodiment shown in  FIG. 4 . 
       FIG. 6  is a perspective view of the positioning member used in the preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIGS. 1 and 2 , a table saw  100  provided by the preferred embodiment of the present invention comprises a base  10 , a worktable  20 , a saw unit (not shown) located inside the base  10  and installed with a saw blade (not shown), and a cutting angle adjustment mechanism  30  installed in the base  10  for controlling the cutting angle of the saw blade installed in the saw unit that is mounted to the cutting angle adjustment mechanism  30 . Because the saw unit is of the known art and not within the scope of the claims of the present invention, no further detailed description in this regard is necessary. 
   The cutting angle adjustment mechanism  30  comprises a pivot shaft  31 , a bracket  32 , a screw rod  33 , an axle  34 , a reinforcing plate  35 , a toothed plate  36 , a positioning member  37 , a handwheel  38 , and a spring member  39 . 
   The bracket  32  is vertically pivotally mounted inside the base  10  below the worktable  20  by the pivot shaft  31  to carry the saw unit, and can be biased to adjust the cutting (tilting) angle of the saw blade installed in the saw unit. 
   The screw rod  33  and the axle  34  are pivotally mounted in the front wall  321  of the bracket  32  at different elevations and arranged in parallel to the pivot shaft  31 . Further, the screw rod  33  and the axle  34  each have one end respectively extending out of the corresponding side of the base  10 . 
   The reinforcing plate  35  and the toothed plate  36  are attached together and affixed to one side of the base  10 . As shown in  FIG. 3 , the reinforcing plate  35  has a first smoothly arched sliding slot  351  and a second smoothly arched sliding slot  352  arranged in parallel. The toothed plate  36  has a smoothly arched sliding slot  361  corresponding to the first smoothly arched sliding slot  351  of the reinforcing plate  35 , a smoothly arched stop wall  363  arranged corresponding to the curvature of the second smoothly arched sliding slot  352  of the reinforcing plate  35 , and a smoothly arched rack  362  raised from and formed integral with one side of the smoothly arched stop wall  363 . The screw rod  33  is inserted through the first smoothly arched sliding slot  351  of the reinforcing plate  35  and the smoothly arched sliding slot  361  of the toothed plate  36  to the outside of the base  10 . The axle  34  is inserted through the second smoothly arched sliding slot  352  of the reinforcing plate  35  to the outside of the base  10 . 
   Referring to  FIG. 6  and  FIG. 2  again, the positioning member  37  comprises a socket  371 , a handle  372 , and a stop flange  373 . The socket  371  is fixedly capped on the end of the screw rod  33  outside the base  10 . The handle  372  is perpendicularly formed integral with the peripheral wall of the socket  371  and suspending outside the base  10  for turning by the operator to rotate the screw rod  33 . The stop flange  373  extends outwards from the peripheral wall of the socket  371 . When the trust flange  373  is rotated to a position as shown in  FIG. 2 , the socket  371  and the screw rod  33  are also rotated to force the bottom of the socket  371  into close contact with the outside wall of the base  10  and to further lock the screw rod  33  to the base  10 , keeping the screw rod  33  positioned in a specific position in the smoothly arched sliding slot  361  of the toothed plate  36 . At this time, the bracket  32  can be held in a specific tilting position.  FIGS. 4 and 5  show the positioning member  37  is turned to an unlocking position where the bottom of the socket  371  is kept away from the outside wall of the base  10 . 
   The handwheel  38  is slidably fastened to the end of the axle  34  outside the base  10 , and can be moved along the extending direction of the axle  34  between a first position (idle position) P 1  (see  FIG. 2 ) and a second position (engagement position) P 2  (see  FIG. 5 ). The handwheel  38  comprises a wheel body  381 , a gear  382  disposed at one side of the wheel body  381 , and a handle  383  disposed at the other side of the wheel body  381  at an eccentric location. 
   The spring member  39  is sleeved onto the axle  34  and stopped between the bracket  32  and the handwheel  38 . The spring member  39  imparts an outward pressure F to the handwheel  38  to force the gear  382  away from the smoothly arched rack  362  of the toothed plate  36 , i.e., to hold the handwheel  38  in the first position P 1 . 
   The operation of the cutting angle adjustment mechanism  30  is described hereinafter. When the handwheel  38  is in the first position P 1  as shown in  FIG. 2 , the bottom of the socket  371  of the positioning member  37  is stopped against the outside wall of the base  10  and the stop flange  373  is set between the gear  382  of the handwheel  38  and the outside wall of the base  10 . If the operator or a person touches the handwheel  38  and forces the handwheel  38  inwards accidentally, the gear  382  of the handwheel  38  will touch the stop flange  373  of the positioning member  37  at first, i.e., the stop flange  373  stops the gear  382  of the handwheel  38  from touching the rack  362  of the toothed plate  36 , preventing a change of the cutting angle of the saw blade of the saw unit. 
   Referring to  FIG. 5 , when wishing to change the cutting angle of the saw blade of the saw unit, rotate the socket  371  of the positioning member  37  and the screw rod  33  to move the stop flange  373  to the position shown in  FIGS. 4 and 5 , i.e., to move the stop flange  373  away from the space between the gear  382  of the handwheel  38  and the outside wall of the base  10 , and then impart a force F to the handwheel  38  to move the handwheel  38  to the second position P 2  and to simultaneously force the gear  382  of the handwheel  38  into engagement with the rack  362  of the toothed plate  36 , and then operate the handle  383  or the wheel body  381  to rotate the handwheel  38 , thereby biasing the bracket  32  to the desired tilting angle. 
   Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.