PISTON AND CYLINDER ASSEMBLY

摘要

An axially expandable and contractable cylinder and piston assembly is provided with an internal axially back and forth movable guide ring for the piston. Helical teeth or thread means at the outer periphery of the guide ring mesh with complementary helical teeth or thread means at the inner periphery of the piston, and helical teeth or thread means at the inner periphery of the guide ring are slanted oppositely to its outer helical teeth or thread means and mesh with complementary helical teeth or thread means on the cylinder.