Patent ID: 7188670

Claim:
A plunger having an upper end and a lower end, and defining an internal chamber, for intermittently lifting fluids from a well having a bottom well stop means, said plunger comprising: (a) at least one hollow cylindrical seal mandrel disposed between the upper end and lower end, wherein the seal mandrel defines a plurality of openings; (b) a resilient seal sleeve attached to the seal mandrel in a fluid-tight manner, covering the seal mandrel openings; (c) a valve assembly disposed at the upper end of the plunger, above the seal mandrel, comprising a valve body defining a valve opening, a valve stem and valve slidingly disposed within the valve body which valve is moveable between a first position wherein the valve opening is closed and a second position wherein the valve opening is open; and (d) wherein the valve stem is actuated by the well stop means inserting into the plunger internal chamber.