Pneumatic timer at ambient air pressure - is for reversing pump and uses bellows fixed to piston, having controlled air bleed rate to delay reversing of bidirectional valve

摘要

The pneumatic pump controller comprises an actuating rod driven by a piston, a bi-directional control valve, and a controlled delay timer for the interval between forward and reverse strokes. The valve (10) admits air initially to the left side of a piston in a cylinder (14). The piston moves to the right to draw fluid from a reservoir (32) into the left hand chamber of the cylinder. At the same time, a link (38) fixed to the piston rod (28A) slides along the piston rod (52) of the timer (44) till it reaches a stop (58). Further piston motion draws a vacuum in the bellows (42) attached to the timer piston (50) and also displaces the bidirectional (10) valve from one detent stop to another (80), reversing the direction of compressed air supply to the piston so it immediately commences to move to the left, forcing the fluid in the left chamber out (83). Air is meanwhile allowed into the timer bellows at a controlled rate. The timer piston (50) is forced back against the air in the bellows (42) by a spring (56) and as it returns the linkage (56) from the timer piston rod to the bidirectional value forces this valve in the opposite direction to recommence the cycle.