| 摘要 |
PURPOSE:To prevent a work and a driver bit from being broken, by prventing the driver bit from being raised until the time period for which electrical charge reaches a value at which a rotary shaft is made free, is elapsed, and by returning the driver bit to its original position after the lapse of the time period, thereby the screw is prevented from being further screwed into. CONSTITUTION:When a screw-fastening starting part 21 is actuated, a power supplying part 38 is operated for initiating the supply of power to a starter drive circuit 45, and timers Ta, Tb initiate time counts. A pulse motor 10 initiates a high speed rotation by an instruction from a logic circuit 42 so that provisional fastening is started. The final fastening is carried out when the screw gets to fit a work after the completion of the provisional fastening and the timer Td counts the time-up. Under the condition of starting the body being returned to its original position, a timer Ti counts the time-up, and therefore, a smoothing condenser contained in the power supplying part 38 discharges. The logic circuit 42 issues an instruction for lifting when the rotary shaft of the motor 10 is made free, and therefore, a lift cylinder 14 initiates the lift movement thereof. |
