| 摘要 |
A pneumatic door actuator in which an actuator rod (5) is driven by a piston (1) working within a cylinder (2), opposite ends (3, 4) of which are selectively pressurised and vented to provide motive effort for the piston (1). If a closing door is temporarily obstructed the pressure in the vented end (3) of the cylinder (2) may drop sufficiently to cause the door to be slammed shut when the obstruction is removed. The appropriate cylinder end (3) is thus vented through a valve (14) which is unseated when the difference between the pressure remaining in the cylinder and the exhaust port vent (11) exceeds a predetermined level. When this pressure difference falls the valve (14) closes trapping the remaining pressure so that it acts as a cushion when piston movement is resumed. |
