Control device for loading and unloading mechanism

Abstract

A control device for loading and unloading mechanism adapted to be incorporated in a fork lift truck comprises a sensor unit 100 including a lifting height sensor 102, a control unit 200 comprising a control command producing circuit 240 constituted by a microcomputer 230 producing a control command on the basis of comparing calculation between the output of the sensor unit 100 and the concerned data stored in the microcomputer 230, and a driving unit 300 producing a driving output signal so as to the lifting height of the fork 18 in accordance with the control command fed from the control unit 200. The control device includes a component operable for inhibiting storage of sampled lifting height data when the actual lifting height data are not within an allowed range, thereby to prevent erroneous operation based on erroneous data and to effect smooth follow-up speed control to the target height when automatic lifting height control is effected. The control device further comprises structure for slowly stopping the fork at the time of the automatic lifting height control. Prior to the automatic lifting height control, when lifting height data is stored in the microcomputer 230, the control device is designed so that lifting height data within a predetermined range can be sampled. Furthermore, the valve opening angle of the control valve for actuating a lift cylinder 346 is limited to a predetermined range, thereby stabilizing a lifting height speed.