Pallets are transported on a series of parallel roller chains, which are supported by inflated air bags. Air bags in each "zone" are kept inflated by air flowing through a "normally open" valve. When a pallet is oriented the wrong way, the edge contacts a sensor arm. The arm is forced down onto the actuator plunger in the valve. This simultaneously diverts the airflow and quickly exhausts the air bag, lowering the chain and stopping the pallet.
A conveyor manufacturer's plastic valve with multiple components is a potential source of problems. Humphrey designed a single metal valve assembly to deliver improved reliability and superior performance.