PLUNGER LIFT ASSEMBLY WITH AN IMPROVED FREE PISTON ASSEMBLY

摘要

An improved free piston assembly for use with a plunger lift assembly is provided. The improved free piston assembly includes a sleeve member, a flow restriction member, and retention means. In some embodiments, the sleeve member has an inner surface contoured to provide a seat for the flow restriction member during lifting operations. The flow restriction member can be a ball held in the interior of the sleeve by retention means capable of overcoming the force of gravity but at the same time designed to release the flow restriction member when a rod of the plunger lift assembly contacts the flow restriction member. The retention means may have pressure members inwardly biased by springs held in place by a retaining ring fittably received by a groove in the exterior surface of the sleeve. In other embodiments, the retention means are in the form of a raised lip or retention sleeve.