Abstract: 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.

Abstract: A dart valve assembly for a bypass plunger is disclosed including a dart valve and a clutch. The clutch bobbin, installed within the bore of a valve cage or a plunger body, is formed of a synthetic material. The clutch restrains the movement of the dart valve within it as the dart valve moves between a closed and an open position. The synthetic bobbin reduces friction and substantially increases the service life of the dart valve assembly. The clutch bobbin surrounds and exerts a predetermined clamping tension on the stem of the dart valve. Both the outside diameter of the dart valve stem and the inside diameter of the clutch bobbin are configured with a sequence of alternating ridges and grooves to improve clutch action.