Patent attributes
A rotary valve can include a seat and a rotary actuator, each with a surface, the rotary actuator rotatably mounted to a housing. The surfaces can form a seal due to their engagement with an engagement force used to maintain the engagement. One biasing device can elevate pressure in a sealed volume in the valve at a constant level above an external pressure. The elevated pressure can produce a pressure differential across the rotary actuator, thereby producing at least a portion of the engagement force. Another biasing device can act between a splined hub and a mated splined shaft, thereby applying at least a portion of the engagement force through the shaft to the rotary actuator. Fluid flowing through a screen can create a pressure drop, thereby causing a pressure differential across the rotary actuator and applying at least a portion of the engagement force to the surfaces.