To easily adjust the speed of a driving part by providing a control part operated by a rotational operation around the axis of a handle bar for controlling the operation direction and the operation amount of the driving part.
A switch valve 21 is gradually rotated and opened following the rotation of a lower handle bar 23 and when the valve is gradually rotated to a specified rotational position, the oil paths 26c and 26a of a switch bar and the oil paths 28 and 27 of a housing 25 are gradually opened and communicated with one another and following this, oil pressure is gradually supplied to a hydraulic motor 11. Thus, the hydraulic motor 11 is gradually started. Then, when the motor is rotated to a position for engagement by a positioning mechanism 24, the oil paths 26c and 26a are fully opened and the rotational speed of the hydraulic motor 11 reaches its maximum level.
GUNJI TSUTOMU
KIMURA TAKASHI
FURUKAWA ELECTRIC CO LTD