Abstract:
A workpiece feeding device used in a saw machine is disclosed to include a carrier having a base frame movably mounted on the machine base of the saw machine and an angle scale fastened to the base frame, a fence unit having a rip fence pivotally mounted on the base frame of the carrier and biasable relative to the angle scale, a magnetic plate assembly mounted on the base frame of the carrier and carrying a magnetic strip, and a magnetic sensor mounted in the fence unit and movable with the fence unit to measure the biasing angle of the fence unit relative to the angle scale subject to change of magnetic induction between the magnetic sensor and the magnetic strip.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to saw machines and more particularly, to a workpiece feeding device for saw machines that has angle detection means to detect the cutting angle. 
     2. Description of the Related Art 
     A conventional table saw is known comprising a machine base, a saw blade holder mounted on the machine base and holding a saw blade and a motor, a horizontal displacement mechanism mounted on the machine base and movable horizontally relative to the machine base and the saw blade holder, an angle adjustment device provided at the horizontal displacement mechanism and adapted for adjusting the cutting angle of the workpiece relative to the saw blade, and an angle scale located on the angle adjustment device for enabling the user to read the cutting angle. When the user is operating the table saw to cut a wooden workpiece, the user can adjust and set the biasing angle subject to the angle scale at the angle adjustment device and subject to the desired shape and size, obtaining the desired cutting angle of the workpiece relative to the saw blade. 
     However, the angle scale of the aforesaid table saw is a simple rule, and the user must read the readings of the angle scale with the eyes. During cutting, the angle scale may be covered by the cut chips. At this time, the user must clean the angle scale. Further, the graduations may become vague after a long use of the table saw. Further, due to the limitation of the graduations of the angle scale, the angle scale cannot satisfy a precision requirement for fine cutting. Therefore, an improvement in this regard is necessary. 
     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 workpiece feeding device for saw machine, which directly indicates the cutting angle for reading by the user to facilitate sawing operation. 
     To achieve this and other objects of the present invention, the workpiece feeding device is used in a saw machine comprising a machine base and a saw blade. The workpiece feeding device comprises a carrier, which comprises a base frame provided at one side of the machine base of the saw and movable relative to the machine base and an angle scale fastened to the base frame. a fence unit, which comprises a rip fence pivotally mounted on the base frame of the carrier and biasable relative to the angle scale, a magnetic plate assembly mounted on the base frame of the carrier and carrying a magnetic strip, and a magnetic sensor mounted in the fence unit and spaced from said magnetic strip of the magnetic plate assembly at a predetermined distance. The magnetic sensor is movable with the fence unit to change the angular position thereof relative to the magnetic plate assembly and to measure the biasing angle of the fence unit relative to the angle scale subject to change of magnetic induction between the magnetic sensor and the magnetic strip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a workpiece feeding device for use in a horizontal displacement mechanism of a saw machine according to the present invention. 
         FIG. 2  is a top view of  FIG. 1 . 
         FIG. 3  is an exploded view of  FIG. 1 . 
         FIG. 4  is an enlarged view of a part of  FIG. 3 . 
         FIG. 5  is a sectional assembly view of a part of the workpiece feeding device according to the present invention. 
         FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1˜6 , a workpiece feeding device with angle detection means in accordance with the present invention is shown installed in a saw machine (not shown) having a machine base and a saw blade mounted in the machine base. The workpiece feeding device comprises: 
     a carrier  10 , which comprises a base frame  11  provided at one side of the machine base of the saw and horizontally movable relative to the machine base, an angle scale  12  fastened to the base frame  11  at the top with screws and having angle graduations  121  marked thereon and a longitudinal slot  122  cut therethrough, a first guide block  123  mounted in the longitudinal slot  122  of the angle scale  12 , a second guide block  124  inserted through the first guide block  123 , a locating bolt  13  fastened to the second guide block  124 , a supplementary frame bar  14  mounted on the base frame  11  at the top and kept in flush with the top surface of the angle scale  12 , two calibration bolts  15  bilaterally mounted on the base frame  11  and disposed near one end of the base frame  11 , two locating plates  16  bilaterally mounted on the base frame  11  and disposed near the other end of the base frame  11 , each locating plate  16  having a coupling groove  161  mounted with bushing  162  and defining an opening  163  and a beveled edge  164  around the opening  163 ; 
     a magnetic plate assembly  20 , which comprises a plate member  21  that has its one side edge smoothly arched and a coupling flange  211  downwardly extended from the smoothly arched side edge and a through hole  212  cut through the top and bottom walls thereof, a bushing  23  mounted in the through hole  212  of the plate member  21  and defining an axial through hole  231 , and a magnetic strip  25  fastened to the smoothly arched side edge of the plate member  21 ; 
     a lock bolt  30 , which comprises a knob  31  located on its one end, an extension rod  33  forwardly extending from its other end, a screw hole  35  formed in the free end of the extension rod  33 , and a holding down portion  37  extending around the root of the extension rod  33 ; 
     a suspension arm  40 , which comprises a narrow elongated arm body  41 , a screw rod  45  perpendicularly located on one end of the arm body  41  and inserted into the through hole  231  of the bushing  23  of the magnetic plate assembly  20  and threaded into the screw hole  35  of the lock bolt  30 , and a guide block  47  located on the other end of the arm body  41  and having a T-shaped profile; 
     a magnetic sensor  50 , which comprises a substantially U-shaped clamping plate  51  affixed to the guide block  47  of the suspension arm  40  and a magnetic sensor element  53  fastened to the clamping plate  51  with screws; 
     a display unit  60 , which is mounted in the base frame  11  of the carrier  10  and, which comprises an electric circuit module (not shown) that is electrically connected with the magnetic sensor element  53  of the magnetic sensor  50  and provides a magnetic displacement measurement function, and a display module  61  for indicating the displacement data measured by the electric circuit module; and 
     a fence unit  70 , which comprises a rip fence  71  mounted on the base frame  11  of the carrier  10 , a length scale  72  located on the top side of the rip fence  71 , a sliding groove  73  of a T-shaped profile located on the bottom side of the rip fence  71  for receiving the guiding sliding movement of the guide block  47  of the suspension arm  40  to guide sliding movement of the suspension arm  40 . 
     The installation of the present invention is outlined thereinafter with reference to  FIGS. 5 and 6  again, the second guide block  124  of the carrier  10  is inserted into the sliding groove  73  of the fence unit  70  and the locating bolt  13  fastened to the second guide block  124  such that when the rip fence  71  of the fence unit  70  is moved relative to the angle scale  12 , the position of the rip fence  71  is changed relative to the angle graduations  121  of the angle scale  12 , and a relative biasing angle is thus indicated. 
     Thereafter, the magnetic sensor  50  is fastened to the suspension arm  40 , and then the screw rod  45  of the suspension arm  40  is inserted into the through hole  231  of the bushing  23  of the magnetic plate assembly  20  and threaded into the screw hole  35  of the lock bolt  30 . At this time, the magnetic sensor element  53  of the magnetic sensor  50  is spaced from the magnetic strip  25  of the magnetic plate assembly  20  at a predetermined distance so that the magnetic sensor element  53  detect the magnetic force of the magnetic strip  25 , and there is a predetermined gap left between the holding down portion  37  of the lock bolt  30  and the coupling flange  211  of the magnetic plate assembly  20 . 
     Thereafter, the guide block  47  of the suspension arm  40  is coupled to the sliding groove  73  of the fence unit  70 , allowing movement of the suspension arm  40 , the magnetic plate assembly  20  and the lock bolt  30  along the sliding groove  73  of the fence unit  70 . Therefore, after installation of the fence unit  70  in one of the two locating plates  16  of the carrier  10 , the extension rod  33  of the lock bolt  30  can be moved into the opening  163  of the locating plate  16 , i.e., the lock bolt can be moved axially through a predetermined distance and then moved transversely into or away from the opening of the locating plate between the locking position and the unlocking position. Further, the coupling flange  211  of the plate member  21  of the magnetic plate assembly  20  is coupled to the coupling groove  161  of the locating plate  16 , and then rotate the knob  31  of the lock bolt  30  to force the holding down portion  37  into engagement with the beveled edge  164  of the respective locating plate  16 , allowing the suspension arm  40  to be turned relative to the magnetic plate assembly  20 . 
     The principle and operation procedure of the present invention are explained hereinafter. When biasing the fence unit  70  relative to the coupled locating plate  16 , the rip fence  71  is moved above the angle scale  12  and the supplementary frame bar  14  to turn the suspension arm  40  about the screw rod  45 . At this time, the magnetic sensor  50  detects a change of the value of magnetic induction relative to the magnetic strip  25  of the magnetic plate assembly  20  and sends the detection result to the circuit module of the display unit  60 , enabling the circuit module of the display unit  60  to calculate the amount of angular displacement and display the calculated value on display module  61 . 
     Further, after installation of the fence unit  70  in one of the two locating plates  16  of the carrier  10 , the angular position (90-degrees angular position) of the fence unit  70  relative to the angle scale  12  and the angular position (90-degrees angular position) of the magnetic sensor  50  relative to the magnetic plate assembly  20  can be calibrated based on the reference of the calibration bolt  15 . Further, the fence unit  70  can be biased inwards within the range of 90-degrees to 45-degrees to adjust the cutting angle of the workpiece. 
     Still further, when wishing to change the position of the fence unit  70  on the carrier  10 , loosen the lock bolt  30 , and then move the magnetic plate assembly  20  and the lock bolt  30  away from the corresponding locating plate  16 , and then couple the magnetic plate assembly  20  to the other locating plate  16 , and then fasten tight the lock bolt  30  to lock the fence unit  70 . Therefore, it is convenient to mount and dismount the fence unit  70 . 
     Further, axle bearings may be used to substitute for the aforesaid bushings, smoothening biasing of the suspension arm relative to the magnetic plate assembly. 
     By means of using the workpiece feeding device with angle detection means of the present invention in a saw machine, the user can adjust the cutting angle of the workpiece by means of adjusting the biasing angle of the fence unit. By means of reading the angle scale or the indication of the display unit, the user knows the cutting angle accurately, facilitating the sawing operation.