GB693099A - Improvements in or relating to expansion devices or engines for use in the production of cold - Google Patents

Abstract

693,099. Refrigerating. GILKES & GORDON, Ltd., G., and CREWDSON, E. March 5,1952. No. 5737/52. Class 29 [Also in Groups XXVI and XXVIII] Cold-air machines. Air compressed in a compressor 30 is supplied at 33 to a cylinder 1 in which reciprocates a double-ended free piston 8, 9 which is rotated continuously about its axis of reciprocation, the expanding air acting on the upper piston 8 and the work of expansion being absorbed by the lower piston 9 compressing air in the lower part of the cylinder. The expanded cooled air passes by a line 34 and heat exchanger 31 back to the compressor 30, a portion being removed for cooling purposes. The expansion piston 8 is shaped to conform with the cover 7 of the cylinder and has an annular series of ports 20 adapted in the uppermost position of the piston to register with inlet ports 14 in an annular chamber 13 communicating with the outlet of the compressor. The air in expanding forces the piston downwardly -until the ports 20 register with exhaust ports 18 in the cylinder and return motion of the piston forces the cold expanded gas through the exhaust ports. During each expansion stroke the gas in the lower part of the cylinder is compressed by the piston 9 and a proportion escapes through a spring-loaded valve 22 and passes through a throttling device 39 and cooler 36 to return to the lower part of the cylinder at 27 at approximately atmospheric temperature and at a pressure equal to that of the cold gas leaving the exhaust ports 18. The remainder of the compressed gas below the piston 9 returns the piston to its uppermost position to receive a fresh charge of gas to be expanded. A pipe 40 connects the port 37 to a port 41 in the cylinder wall to equalize the pressure in the cylinder space between the two pistons 8, 9 and avoid gas flow past baffle plates 25 which minimise heat leakage. The piston is caused to rotate continuously about its axis by a small jet of air or gas from an orifice 28 acting on a vane 26. Maintenance of the necessary relation between the angular and longitudinal positions of the piston for operation of the ports is effected by mechanical or electrical means, e.g. the vane 25 may comprise a bar magnet or electromagnet co-operating with a magnet 27 entering through the cylinder wall so that at this magnet or electromagnet co-operating with a magnet 27 entering through the cylinder wall so that at this axial position of the piston the magnet aligns the piston with ports 14, 20 in register.