GB601367A - Improvements in internal-combustion-operated free-piston engines - Google Patents

Abstract

601,367. Cooling pistons. PESCARA, R. P. Dec. 6, 1945, No. 33071. Convention date, Nov. 18, 1944. [Class 122 (i)] [Also in Group XXVII] The interior of a pneumatic energy accumulator of a free-piston engine or gas generator, sealed at least during normal operation under steady running conditions, is divided into two spaces which communicate with one another through a restricted passage, the arrangement being such that the ratio of the volumes of the spaces varies as a consequence of the movement of the associated free-piston and accordingly creates an alternating current of air between the spaces and the passage is formed in the free-piston and opens close to the piston crown. As shown (Fig. 1), a free-piston gas generator has pneumatic energy accumulators formed between a cover 12 of a cylinder 9 and the interior of a stepped free-piston 5, 8. The accumulator is divided into two spaces by a partition 15 inside the piston having restricted orifices 16 through which the spaces communicate with one another. The smaller space Ca between the piston crown 5a and the partition is fixed in volume while the volume of the larger space a, b, c varies as the free piston operates. The movement of the piston thus sets up an alternating current of air between the two spaces and helps to cool the crown 5a of the piston. A space between the piston 8 and a partition 11 forms a compressor supplying compressed air to a scavenging space 2. The exhaust products are delivered through ports 4. The crown 5a of the piston is removable and is held in position by a split sleeve 17. In a modification, Fig. 3, a cushion space a, b, Ci, Cb of a gas generator is divided into two parts by a restricted passage between the end of a tube 23 within the power piston 5 and cooling ribs 24 on the interior surface of the piston. A modification of this arrangement is described in which an annular partition between the tube and the interior of the piston divides the space within the piston into two parts, the portion nearer the compressor cylinder being connected to the space outside the power piston by holes in the tube. In a second modification of this arrangement, the outer end of the compressor piston 8 is closed and the space within this piston is connected tor the space within the power piston. In each of these arrangements a cooling coil 38 supplied with cooling water is located within the tube 23. In a further modification comprising a two-stage opposed free-piston compressor, one end of which is shown in Fig. 5, a cushion space d, e at each end is divided into two parts by a restricted orifice 37, the space d being of fixed volume. The power pistons 32 are each connected to compressor pistons 33, 34 which compress air on the outward stroke. The piston 33 works in a cylinder 30 forming a lowpressure compressor and the piston 34 forms with a cylinder 31 a high-pressure compressor. A cooling coil is located in the space e.