Reciprocating apparatus with a controllable dwell time at each end of

Abstract

The piston of a pneumatic cylinder is reciprocated with a controllable dwell time at each end of its stroke, under the control of a digital fluidic circuit which responds to the termination of exhaust flow at the end of each piston stroke to initiate the reverse piston stroke. The air for driving the piston is supplied alternately to opposite ends of the piston through respective cylinder ports, by way of a corresponding pair of pilot valves which are controlled by the fluidic circuit so that one or the other of the pilot valves may supply driving air to the piston at any time. Whenever the piston is in motion, a stream of exhaust air flows through the exhaust port ahead of the piston, and this exhaust stream acts through the fluidic control circuit to maintain the pilot valves in their then-existing states; when the exhaust stream stops at the end of a piston stroke, the fluidic circuit responds to produce a pneumatic pulse delayed by a controllable time with respect to termination of exhaust flow, and this delayed pulse triggers a two-state fluidic device to its opposite state; this in turn reverses the states of the pilot valves so that the other pilot valve now supplies driving air to the opposite end of the piston to drive it in the opposite direction. Reciprocation can be 'turned off' by supplying a simulated exhaust stream to the fluidic circuit. Fluidic outputs indicative of the direction of piston movement and of whether reciprocation is occurring are also provided.