US Patent 9506382 Variable valve actuator

A valve actuation system is provided. A fluid actuator is configured to selectively prevent a valve from moving to a particular position. A source of fluid is in fluid communication with the fluid actuator. A bi-directional control valve is configured to control a flow of fluid between the source of fluid and the fluid actuator. A fluid passageway connects the bi-directional control valve with the fluid actuator. A relief valve is in fluid communication with the fluid passageway and moveable between a closed position to prevent a flow of fluid therethrough to create a high pressure circuit in the valve actuation system and an open position to allow a flow of fluid therethrough to create a low pressure circuit in the valve actuation system.