US Patent 9677389 Dart valve assembly for a bypass plunger

A dart valve assembly includes a dart valve and a clutch that restrains the movement of the dart valve within the bore of a dart valve cage or plunger body between a closed and an open position. The clutch includes a clutch bobbin formed of a synthetic material, and both the inside diameter of the clutch bobbin and the outside diameter of the dart valve stem of the dart valve assembly are configured with a sequence of alternating ridges and grooves to improve clutch action through reduced friction.