Abstract: A liquid pressure striking device defines a double-acting cylinder in a main body thereof having a tool at its lowest portion, and the double-acting cylinder houses therewithin a piston having an upper rod and a lower rod. The lower rod suspends a hammer for striking the tool, and the upper rod is provided on its outer circumference with a change-over valve mechanism which comprises a valve body of special structure for automatically switching the liquid flow under pressure by vertical movement of the piston, and a valve chamber having a plurality of concaves for controlling said valve body. Above the upper part of the valve chamber, there is provided an accumulator serving as a cap or cover of the main body. The main body is formed with an inlet passage of the liquid and an outlet passage, communicating with the accumulator and the valve chamber.

Abstract: A band type strapping machine comprises a feeding and tightening roller driven by a motor, an auxiliary roller in contact with the feeding and tightening roller, a cam shaft which is rotated by the motor through a reduction gear and a clutch mechanism and which has cams for respectively actuating a rear gripper, a heater, a press bar and a front gripper, wherein the motor is capable of instantaneous change of normal and reverse rotations and has a large starting torque, and an electromagnetic clutch is fitted to the rotary shaft of the tightening and feeding roller so as to be movable in the axial direction depending upon increase of a band tightening force whereby detection of the tightening force caused by the movement of the electromagnetic clutch is mechanically related to the engagement or disengagement of the clutch mechanism.