| 摘要 |
A fluid actuator for a gate has a main fluid ram (10) with piston means (12) drivable to move a piston rod (18) between first and second positions, a control spool valve (30) for causing the piston means to be driven and a timer or driver spool valve controlling operation of the control valve. In one form the piston means comprises a single piston in a cylinder and the piston rod is moved into and out of the cylinder. In another form the piston means comprises a pair of pistons coupled to opposite ends of the piston rod and moveable in respective ones of two horizontally opposed cylinders. An operating lever connecting the actuator to a gate is coupled to the piston rod in a way allowing both sliding and pivoting movement of the lever relative to the rod. The driver valve body is driven between its operative positions by a cam which moves with the piston rod and in moving causes the control valve (after a predetermined time delay) to reverse the direction of movement of the piston rod. If in closing a gate coupled to the actuator meets an obstruction the resultant over (or under) pressure causes the opening cycle to be restarted. A hybrid is also described system in which compressed air is used to control operation of the control valve which in turn passes compressed air to liquid reservoirs forcing the liquid therein to drive the piston means. |
