Abstract

A pneumatic logic control module is disclosed which includes three miniaturized, piloted, detented relay valves mounted on a pneumatic circuit board including a valve mounting plate, a circuit plate having routed flow paths formed in each face, and a connector plate having barbed ports for receiving flexible tubes. The pneumatic circuit interconnects the relay valves so that the relay valves are shifted from a normal position to an active position and locks to the normal position in a predetermined sequence to produce a series of pneumatic pressure signals. The module produces a first pneumatic pressure signal in response to a start signal which is used to initiate a first event. A return verification signal indicating that the first event has been completed terminates the first pressure signal, and initiates a second pressure signal which starts a second event. A second return verification pressure signal indicating that the second event has been completed terminates the second event pressure signal and initiates a third pressure signal. The circuit is designed to prevent any subsequent event, including a relay valve shift, from occurring before positive verification that all preceeding events have occurred. Any or all relay valves can be reset to the normal position, or any one relay valve can be preset to the active position so that the automatic sequence can be initiated at any desired event. The module has all ports necessary to permit any number of modules to be cascaded in series, in parallel, in combinations of series and parallel circuits, or in nested loops to provide complete flexibility in designing a pneumatic logic circuit. Limit valves, time delays, proximity and temperature sensors, and other devices may be used in the verification circuit. A unique circuit board assembly is also disclosed which utilizes a simplified shuttle valve structure.