Patent GB-197962-A (GB)
Title: Improvements in refrigerating machines
IPC: F25B9/00
Filed: 1923-05-22
Abstract: 197,962. Automatic Refrigerating Co., (Assignees of Lundgaard, I.). May 22, 1922, [Convention date]. Refrigerating, cold-air machines for.-In a machine working in a closed cycle and comprising a compressor piston 25 and a displacement piston 40 arranged within a common cylinder having regenerator passages 6 and heat interchangers 5 and: 7, as described in Specification 195,628, the refrigerating medium is transferred between the expansion and compression chambers at substantially constant pressure and while the compression piston is in motion. The interchangers comprise leaves or fins 19, 24 in the air passages and similar fins 20, 21 in the cooling passages. The crank casing is sealed from the atmosphere by an oil seal in the crank-shaft stuffing-box 75, and communication is provided between the interior of the crank casing and the compression chamber at periods of minimum pressure, to obtain an equalization of pressure through the system, with a higher average compression pressure and low expansion pressure. The oil seal comprises a perforated ring 78 slidable on the shaft between packings in a space separating a fixed bearing 76 and a ball bearing 77. The communication between the compression chamber and crank casing may consist of a port 60 in the piston 25, Fig. 1, registering with a port 61 in the cylinder wall when the piston reaches the end of its downward stroke. The port 61 is connected by a pipe 62 to a chamber 63, which may contain a drying agent such as calcium chloride, and this chamber is connected by a pipe 64 to the crank casing. In a modification, a port 100, Fig. 3, is formed in the wall of the compression chamber, and communicates with the crank casing through a pipe 101, a lift valve 106, and a pipe 103. The lift valve is attached to a diaphragm 107 subjected on the inner side to the pressure in the compression chamber, so as to open when the pressure in the crank casing, due to leakage past the piston 25, exceeds the minimum pressure in the cycle. The piston 25 is connected by links 2& to a rocking beam 27 actuated by a connecting-rod 29 on the crank-pin 30. The displacement piston 40 consists of a shell 41 of heat-insulating material attached to a plate 42, and is provided with a rod 43 passing through a bush 45 in the compressor piston and extending to a guide bearing 46 at the bottom of the crank casing. A collar 48 forming an abutment for a spring 55 is attached to the rod 43 by a pin 49, to which a pair of links 50 are connected. The other ends of these links are connected to a member 51 pivoted on the same shaft 28 as the beam 27 and carrying a roller 52 bearing against a cam 54 on the crank shaft. This mechanism is so arranged as to produce the following cycle :-On the up-stroke of the compressor piston the air is compressed between the two pistons, while the displacement piston remains at the top of its stroke. The displacement piston then descends rapidly and discharges the compressed air through the cooling and regenerator passages to the expansion chamber above the upper piston, after which the two pistons move downwards together for a period. The displacement piston then rises rapidly and moves the air in the reverse direction back to the compression chamber. The relative pressures and volumes at different parts of the cycle are illustrated in the Specification by diagrams. The fluid to be cooled is circulated through a hollow cover 9 held in position on the cylinder by a heat-insulated strut 12 bearing against a channelled frame member 11 connected to the base 1 by tie-rods 10.