GB1168818A - Improvements in or relating to Devices for Producing Cold - Google Patents

Abstract

1,168,818. Refrigerating. PHILIPS' GLOEILAMPENFABKIEKEN N.V. 30 Nov., 1966 [3 Dec., 1965], No. 53559/66. Heading F4H. In a refrigerating machine having a piston reciprocable in a cylinder to vary the volume of an expansion space, and a gap between the piston and cylinder which communicates at one end with the expansion space and is bounded at its other end by a seal between the piston and cylinder, the walls of the gap are cooled in operation of the machine to reduce the loss of cold from the expansion space. As shown, a cold gas refrigerator comprises a displacer having upper and lower portions 4, 5 of different diameters, a seal 18 being provided between portion 4 and its cylinder wall which are otherwise spaced to define a gap extending from the seal to the expansion space 6. The walls of portion 4 and its cylinder are stepped to provide spaces 22, 23 in which expansion takes place during operation of the refrigerator so that the walls of the gap are cooled and loss of cold from space 6 is reduced. In another embodiment (Fig. 3, not shown) the piston and cylinder taper from the seal to the expansion space so that expansion cooling again occurs in the gap. A stepped piston and cylinder arrangement as described above may also be employed in a machine of the type in which the cylinder is alternately connected to the inlet and outlet of an external compressor via high and low-pressure reservoirs (Fig. 4, not shown). In a further embodiment (Fig. 5, not shown) cold from the expansion space of a first cold-gas refrigerator is transferred to the walls of the gap via a closed condensing-evaporating system or a copper strip.