GB619196A - Improvements in or relating to two-cycle internal combustion engines - Google Patents

Abstract

619,196. Two-stroke engines. SPARMANN, E. E. K. Nov. 26, 1946, No. 35043. Convention date, Nov. 27, 1945. [Classes 7 (ii) and 7 (vi)] A two-stroke internal-combustion engine has one or more cylinders 1 with upper exhaust ports 18 and lower inlet ports 19 coacting respectively with ports 20, 21 in a sleeve valve 4 surrounding the piston 5 which controls the ports 21, the sleeve valve being oscillated with a combined axial and rotary movement arranged to provide greater axial acceleration during the scavenging period than during the compression and expansion period. The upper part of the sleeve valve slides in a space 3 between the cylinder head and the cylinder. A control shaft 9 driven at the same speed as the crank shaft 7 and in either direction oscillates an arm 13 pivoted at 14 and connected through sliding and universal connections 15 to the sleeve valve to which a combined rotary and axial oscillation is thus imparted, the rotary component increasing towards the upper limit of the valve travel. The phase of the crank 9 is somewhat more than 180 degrees in advance of the crank 7 so that the axial acceleration of valve 4 is at a maximum, Fig. 2, when the valve is at the bottom of its stroke, at a time when the piston, also near the bottom of its stroke, has a relatively smaller acceleration. The slight lead of the valve is shown in Fig. 3, where the piston is starting upwards on its compression stroke and the inlet ports are open. When the crank reaches 85 degrees beyond its lower dead centre the piston overtakes the valve and closes the inlet ports and compression ensues. The exhaust opens about 70 degrees before lower dead centre and 40 degrees later the inlet valve opens and scavenging occurs and continues for about 60 degrees of crank movement. The path of the pin 16 is such that most of the rotary movement of the sleeve valve occurs near the upper limits of movement when the ports are closed. In a modification, Fig. 5, particularly for radial engines, the valve is operated from a crank pin 10 on the main shaft connected through the linkage shown to a rocking-lever 13 pivoted at 14 and connected to the valve at 15. In this form the scavenging air enters by ports 19<11>, and the combustible mixture by upper ports 191. The two sets of ports may have guide vanes inclined in opposite directions. In another modification, Fig. 8, having cylinders parallel to the power shaft 7, and pistons connected to a wobbler plate 27, a link 11 connected to the wobbler plate at 10 is also connected to a link 16 supported by pivoted links 30, 32 and connected to the sleeve valve at 15. The path 150 of the pin 15 shows that the rotary part of the valve movement is almost entirely limited to the upper end part of the travel. The required advance of the valve movement is obtained by the relative disposition of the part 10 and the piston connection point 8. Specification 506,326 is referred to.