US Patent 7540721 Automatic inlet check valve release

Apparatus and method for releasing a stuck inlet check valve of a paint pump including a solenoid connected to the check valve with a pusher element which momentarily displaces a moveable element such as a ball in the check valve to break any adhesion between the movable element and a valve seat. A control provides a single pulse of energy to the solenoid each time power is applied to the pump. The control includes an SCR connected between a full wave rectifier and a coil of the solenoid, with gate current removed from the SCR to commutate the SCR after a predetermined time interval after power is applied.