| 摘要 |
PURPOSE:To prevent a damage caused by making contact with a rock, etc. by switching and connecting the pipings at the hydraulic oil supply side to the return piping to a tank by the signal from a stroke end detector accommodated in a cylinder. CONSTITUTION:As a valve 5 is switched to connect a pump 6 to a piping 4, a piston 2 is displaced to the left and when the piston 2 reaches near a stroke end, its end surface pushes a push rod 37 of a servo cylinder 33A of a stroke end detector to the left. Thus, the oil within a chamber 34 flows into a chamber 25A through a piping 32A and moves a spool 24 to the left. Accordingly, a port 28 communicates with a port 27 and a piping 4A communicates with a piping 3A. As the pressure in a chamber B is high, the pressurized hydraulic oil supplied from the pump 6 to the piping 4 passes through the piping 4, the chamber 23, the piping 3A and 3 is turn and in returned to a tank 7, and the piston 2 is moved by inertia force and its speed is reduced. The pressurized hydraulic oil from the pump 6 is returned to the tank 7 and the pump 6 is driven at no load. Since the stroke end detector is accommodated within the piston 2, it is not liable to be damaged. |
