| 摘要 |
<p>PROBLEM TO BE SOLVED: To effectively stop a suction grill at a predetermined position under simple control. SOLUTION: A main sensor 31 senses a marker provided at a position of the fed length of a fed wire for vertically moving a suction grill corresponding to a stopping position of the wire. A detector 71 generates a detection signal of a predetermined level based on a signal from the sensor 31. A vertical movement controller 72 counts number of passages of the marker of the wire by a counter 75 based on a detection signal from the detector 71. And, a motor driver 76 is controlled based on its counted value and instructions from remote controllers 73, 74 to descend or ascend or temporarily stop the grill. Thus, the stopping position is accurately controlled at the time of descending the grill based on a value corresponding to an actually fed length of the wire.</p> |
