GB253213A - - Google Patents

Abstract

253,2.13. Shannon, D. M. Feb. 13, 1925. Cylinders, arrangement of ports in.-In a twostroke-cycle engine, scavenging ports are arranged to be connected by control valve to the exhaust pipe at one part of the cycle, for providing additional opening for exhaust, and to the scavenging- air pipe at another part of the cycle. Fig. 1 shows a double-acting engine having exhaust ports E and scavenging ports F, each occupying one-half of the circumference of the cylinder. the annular chamber surrounding them being provided with diametrically opposite control valves G<2>, Figs. 1 and 1A, which are shown in the closed position, separating the ports E and F. When the ports are first uncovered by the piston, the valves G<2> are open, so that exhaust occurs through both sets of ports; when the cylinder pressure falls to that of the scavenging- air, the valves G<2> are closed automatically, and scavenging-air enters the ports F from the main J and past a valve H. The valves G<2> are flap valves controlled by springs g<6> and actuated automatically by the pressure of the exhaust gases and scavenging-air. Figs. 4 and 5 show a combined valve G<3>, H<3> for performing the functions, the butterfly portion G<2> controlling the connection between the exhaust space B and scavenging space C by engaging seats g<7>, g<8>, and the oscillating disc portion H<3> controlling ports h<3>, r<1> which admit the scavenging-air to the ports F when the portion G<3> is closed on to the seats g<7>, g<8>. In another form, a double flap valve acts automatically to perform both functions. Fig. 7 shows an oscillating or intermittently rotated disc valve H<@5> arranged near the ports F so as to control the admission of scavenging- air thereto; the semi-annular space C is divided into two portions, each of which is fitted with a valve H<5>. The valve H<5> may be spherical. The ports F may be longer than the exhaust ports E, so that supercharging is obtained after the piston has closed the latter. Fig. 11 shows a double-acting engine having exhaust ports E E<1> and scavenging ports F<5>, F<6> on the same side of the cylinder, supplementary exhaust and scavenging ports being arranged at F<3>, F<4>. In modifications of this form, the ports F<5>, F<6> may be combined into a single set. The air entering through ports F<3>, F<4> is deflected at an acute angle to the cylinder axis by a bridge piece arranged around the ports.