GB501864A - Improvements in or relating to sleeve valves for two-stroke internal combustion engines - Google Patents

Abstract

501,864. Valves. HOWALD, W. Jan. 26, 1938, No. 2553. Convention date, Jan. 27, 1937. [Class 7 (vi)] A sleeve valve for two - stroke engines controlling with its upper edge inlet or exhaust ports in the cylinder is so arranged that, when the piston is in its upper deadcentre position, the rubbing surfaces of the cylinder and sleeve valve are both screened from direct contact with the combustion gases. Fig. 3 shows a section of half a cylinder with the sleeve valve 2 working in a recessed part of the cylinder 1, so that the rubbing surfaces U<1> and U<2> are screened by the piston 4 from the hot gases. The upper edge of the valve controls exhaust ports A, and ports D in the valve control scavenging-ports B and charging-ports B<1>. Alternatively, the upper edge of the valve may control ports used for both scavenging and charging, while the valve ports D control two rows of exhaust ports, the preliminary exhaust passing to a turbine. Fig. 6 shows the piston 4 fitted with a wide upper packing-ring 15, which is not split, but arranged to have radial play, its rear surface being machined down as shown to afford resilience. In a modification, the ring 15 is formed with a resilient lip at its lower edge also. In cases where the upper ring 15 passes entirely above the shoulder S on the cylinder, the second ring is also made entire and with radial play. The upper end of the sleeve valve and tho cylinder walls may be tapered slightly inwards to allow for heat expansion. The valve, cylinder, and piston rings may be of steel with the rubbing surfaces hardened by nitrogenizing or chrome hardening; or the valve may be made of aluminium, copper, or nickel alloys; or the valve and cylinder may be of steel coated with such alloys ; or the piston-rings may be of hardened beryllium bronze or of steel coated therewith. Specification 462,427 is referred to.