Abstract:
A cutter blade driving and positioning control structure formed of a rotary drive, a transmission unit, a sliding unit, a linear motor and a cutter unit and used in a plastic pelletizing machine for making plastic pellets is disclosed. The rotary drive provides a rotary driving force for driving the transmission unit to rotate the cutter unit. The linear motor is adapted to reciprocate the transmission unit, moving the cutter unit back and forth rapidly with minimized energy consumption.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to plastic pelletizing technology, and more particularly to a cutter blade driving and positioning control structure used in a plastic pelletizing machine for making plastic pellets, which moves and rotates the cutter unit of the plastic pelletizing machine rapidly and accurately, saving much energy consumption and prevents perforated plate damage due to an overpressure. 
     2. Description of the Related Art 
     A plastic pelletizing machine for making plastic pellets is known using a motor to rotate a cutter over the surface of a perforated plate, thereby cutting off the extruded plastic material into plastic pellets. However, because the plastic pelletizing machine must be wholly shifted to move the cutter into contact with the surface of the perforated plate before operation, the shifting apparatus adapted to shift the plastic pelletizing machine is heavy and has a large size. Further, the shifting apparatus consumes much power during operation and cannot move the plastic pelletizing machine back and forth rapidly. 
     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 cutter transmission and control mechanism for plastic pelletizing machine, which moves and rotates the cutter unit of the plastic pelletizing machine rapidly and accurately, saving much energy consumption and prevents perforated plate damage due to an overpressure. 
     To achieve this and other object of the present invention, a cutter blade driving and positioning control structure of the invention is used in a plastic pelletizing machine for making plastic pellets. The cutter blade driving and positioning control structure comprises a rotary drive, a transmission unit, a sliding unit, a linear motor and a cutter unit. The rotary drive comprises a drive motor, and a driving shaft coupled to and rotatable by the drive motor. The driving shaft comprises a plurality of longitudinal coupling grooves equiangularly spaced around the periphery thereof. The transmission unit comprises a transmission shaft and a bearing block. The transmission shaft is a tubular shaft sleeved onto the driving shaft of the rotary drive and pivotally mounted in the bearing block, comprising a plurality of longitudinal coupling ribs equiangularly spaced around an inner perimeter thereof and respectively slidably coupled to the longitudinal coupling grooves of the driving shaft so that rotating the driving shaft causes rotation of the transmission shaft in the bearing block. The sliding unit is disposed at one lateral side relative to the driving shaft of the rotary drive, comprising a seat member and a sliding block. The sliding block has one side thereof slidably coupled to the seat member, and an opposite side thereof fixedly connected to the linking block of the transmission unit. The linear motor comprises a motor body affixed to the drive motor of the rotary drive, and an inductor connected to the bearing block of the transmission unit and adapted to move the bearing block alternatively back and forth relative to the motor body when activated. The cutter unit is connected to the transmission shaft of the transmission unit and rotatable and axially movable by the transmission unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an oblique top elevational view of a cutter blade driving and positioning control structure used in plastic pelletizing machine in accordance with the present invention. 
         FIG. 2  is a side view of the cutter blade driving and positioning control structure in accordance with the present invention. 
         FIG. 3  is an elevational view of a part of the cutter blade driving and positioning control structure in accordance with the present invention. 
         FIG. 4  is an exploded view in an enlarged scale of a part of the cutter blade driving and positioning control structure in accordance with the present invention. 
         FIG. 5  is a sectional view taken along line A-A of  FIG. 2 . 
         FIG. 6  is a schematic sectional view illustrating the operation of the present invention (I). 
         FIG. 7  is a schematic sectional view illustrating the operation of the present invention (II). 
         FIG. 8  is a schematic sectional view illustrating the operation of the present invention (III). 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1-6 , a cutter blade driving and positioning control structure for plastic pelletizing machine in accordance with the present invention is shown. The cutter transmission and control mechanism comprises a rotary drive  1 , a transmission unit  2 , a sliding unit  3 , a linear motor  4 , and a cutter unit  5 . 
     The rotary drive  1  comprises a motor  11 , a driving shaft  12  coupled to and rotatable by the motor  11 . The driving shaft  12  comprises a plurality of longitudinal coupling grooves  121  equiangularly spaced around the periphery thereof. 
     The transmission unit  2  comprises a transmission shaft  21 , a bearing block  22 , and a linking block  23 . The transmission shaft  21  is a tubular shaft sleeved onto the driving shaft  12  of the rotary drive  1  and pivotally mounted in the bearing block  22 , comprising a plurality of longitudinal coupling ribs  211  equiangularly spaced around an inner perimeter thereof and respectively slidably coupled to the longitudinal coupling grooves  121  of the driving shaft  12 . Thus, rotating the driving shaft  12  can rotate the transmission shaft  21  in the bearing block  22 . Further, the bearing block  22  is connected to the linking block  23 . 
     The sliding unit  3  is disposed at one lateral side relative to the driving shaft  12  of the rotary drive  1 , comprising a seat member  31  and a sliding block  32 . The sliding block  32  has its one side, namely, the bottom side slidably coupled to the seat member  31  and its opposite side, namely, the top side fixedly connected to the linking block  23  of the transmission unit  2 . Further a sensor  33  is mounted at one side of the seat member  31  and adapted to detect the sliding distance of the sliding block  32 . 
     The linear motor  4  comprises a motor body  41  affixed to the motor  11  of the rotary drive  1 , and an inductor  42  connected to the bearing block  22  of the transmission unit  2  and adapted to move the bearing block  22  alternatively back and forth relative to the motor body  41  when activated. 
     The cutter unit  5  comprises a coupling shaft  51 , a cutter holder  52 , a spring member  53 , a plurality of cutter blades  54 , a locating member  55 , and a plug member  56 . The coupling shaft  51  is a tubular shaft axially slidably sleeved onto the driving shaft  12  of the rotary drive  1  and fixedly connected to the transmission shaft  21  of the transmission unit  2 , comprising a plurality of axial coupling teeth  511  equiangularly spaced around an outer perimeter of a front end thereof. The cutter holder  52  comprises an accommodation hole  521  axially disposed in one end thereof, a displacement hole  523  axially disposed in an opposite end thereof in communication with the accommodation hole  521 , and a plurality of axial coupling grooves  522  equiangularly spaced around an inner perimeter thereof within the accommodation hole  521  and axially slidably coupled to the axial coupling teeth  511  of the coupling shaft  51 . The spring member  53  is mounted in the accommodation hole  521  and stopped with its one end against an inside wall of the cutter holder  52  between the accommodation hole  523  and the displacement hole  521  and its other end against the front end of the coupling shaft  51 . The locating member  55  is movably mounted in the displacement hole  523  and inserted through the spring member  53  into the accommodation hole  521 . The cutter blades  26  are affixed to one end of the locating member  55  outside the cutter holder  52  and rotatable and axially movable with the locating member  55 . The plug member  56  is mounted in the accommodation hole  521  of the cutter holder  52  around the locating member  55  and connected to the coupling shaft  51  for enabling the locating member  55  to be rotated with the coupling shaft  51 . 
     Referring to  FIGS. 1-7 , during operation of the plastic pelletizing machine, the motor  11  of the rotary drive  1  is controlled to rotate the driving shaft  12 , thereby rotating the transmission shaft  21  of the transmission unit  2  and the coupling shaft  51  of the cutter unit  5 . When going to move the cutter blade  54  of the cutter unit  5  into contact with the plastic pelletizing machine&#39;s perforated plate  6 , the inductor  42  of the linear motor  4  is activated to move in direction away from the motor body  41  of the linear motor  4 , thereby carrying the bearing block  22  in direction toward the perforated plate  6 . When the bearing block  22  is moved in direction toward the perforated plate  6 , the transmission shaft  21  is carried by the bearing block  22  to move the cutter unit  5  toward the perforated plate  6 , forcing the cutter blade  54  into contact with the plastic pelletizing machine&#39;s perforated plate  6 . Further, during movement of the bearing block  22 , the sliding block  32  is moved relative to the seat member  31  that guides the sliding movement of the sliding block  32  accurately toward the perforated plate  6  within a predetermined range. Subject to the detection of the sensor  33  at the seat member  31 , the moving distance of the sliding block  32  is accurately measured, and thus the displacement of the sliding block  32  can be accurately controlled. 
     Referring to  FIG. 8 , when the inductor  42  of the linear motor  4  moves the bearing block  22  toward the perforated plate  6 , the coupling shaft  51  will be moved to force the spring member  53  against the cutter holder  52 . If the inductor  42  keeps moving the coupling shaft  51  toward the perforated plate  6  after contact between the cutter blade  54  of the cutter unit  5  and the surface of the perforated plate  6 , the spring member  53  will be compressed to compensate the displacement of the coupling shaft  51 , preventing perforated plate damage due to an overpressure. 
     In general, the technical feature of the present invention is the arrangement of the transmission unit  2  to rotate the cutter unit  5  and the arranged of the linear motor  4  to move the transmission unit  2  alternatively back and forth, enabling the cutter unit  5  to be moved back and forth rapidly, saving energy consumption in displacement of the cutter unit  5 .