Abstract: A gas compressor for compressing working gas of a hot gas engine is using the oscillating pressure of a working gas charge for acting upon the large diameter piston of a differential piston the small diameter part of which is used as compressor piston. One side of the large diameter piston is directly connected to a variable volume chamber of the hot gas engine while the other side of the same piston is alternatively connectable either to a minimum or a maximum gas pressure source.

Abstract: The safety valve contains a resilient gland to be held between a valve seat and a valve member and is secured to the valve member by a sleeve surrounding the end of the valve member adjacent to the valve seat. The sleeve is movable relative to the valve member through a limited axial distance and a gap exists between said valve member and said sleeve.

Abstract: Leakage of gas is prevented by an oil seal established as an oil reservoir surrounding a piston rod. The reservoir is limited by spring-influenced plastic rings arranged in a seal housing. The springs are located at the low gas pressure side of the seal. Oil is supplied to the piston rod surface at the low pressure side of the seal.

Abstract: A scraper ring for removing oil from a piston rod is made of plastic and comprises conical surfaces defining a smallest diameter edge for contact with the piston rod. The ring is axially loaded with Belleville springs and a mating support ring bearing on the scraper ring.

Abstract: In Stirling engines the high pressure of the cycle requires special seals on the piston rod to prevent leakage of gas out of the high pressure cylinder into lower pressure regions such as a crankcase. A liquid oil seal is developed in a chamber around the piston rod by movement of the piston rod to carry oil into the chamber which is limited by an upper scraper member and a lower sealing gland. The chamber leads to a membrane operated pressure comparison valve releasing oil from the chamber when its pressure exceeds that of the gas in the high pressure cylinder. No gas need be pumped back into the high pressure chamber and thus no separation of gas and oil is necessary.