Seal for piston rod of Stirling engine

Claim 1

In a seal for a piston rod of a Stirling engine having a reciprocating piston rod, an intermediate chamber surrounding the piston rod and held at a minimum pressure of a working gas, a fluid-filled chamber surrounding the piston rod for lubricating the piston rod, and an oil scraper disposed between the intermediate chamber and the fluid-filled chamber for blocking flow of a fluid from the fluid-filled chamber to the intermediate chamber, an improvement comprising an annular sealing member fixedly secured to the piston rod at a position where said annular sealing member will be situated immediately above the oil scraper when the piston rod is at a bottom dead center point of its reciprocating motion, the intermediate chamber being formed to include a first space of a first diameter and a second space of a second diameter smaller than said first diameter, said second space having its diameter sized to an outer diameter of said annular sealing member and being contiguous to the oil scraper, whereby when the piston rod descends toward the bottom dead center point, said annular sealing member is carried thereby into said second space toward the oil scraper to pressurize said second space in order to forcibly return a fluid from said second space to the fluid-filled chamber through the oil scraper.