Improvements in and relating to free pistons for use in eduction pipes of apparatus for raising liquid in wells

摘要

635,772. Piston packing. BROWN, N. F. Feb. 13, 1947, Nos. 4145, 11732 and 23313. [Class 122(i)] [Also in Group XXVIII] An oil well pump wherein the piston is held at the bottom of a well tube whilst a slug of oil is formed above it and then the holding means is released and the piston is raised by gas pressure. At the same time as the holding means are released, a piston 52 acts upon liquid trapped in the cylinder 50 and forces it through ports 49 to expand a resilient packing sleeve against the well tube 8. In an alternative arrangement, the packing sleeve is expanded by moving one end relatively to the other by mechanical means. Specifications 403391, 493,283, 584,410, 616,885, 616,887, [all in Group XXVIII], 635,771 and 635,772 are referred to.