GB744248A - - Google Patents

Abstract

744,248. Ports; valves. YOKOI, M. Feb. 10,. 1953, No. 3772/53. Classes 7(2) and 7(6) In. -a two-stroke engine with piston-. 'controlled scavenging and exhaust ports arranged circumferentially in the cylinder wall near the B.D.C.. position of the piston and having first stage exhaust ports E<SP>1</SP>1- E<SP>1</SP>6, second stage exhaust ports E1-E3 and scavenging ports S1-S5, the ports E<SP>1</SP>1-E<SP>1</SP>6 being so positioned that they are uncovered by the piston earlier than the other ports during the expansion stroke, the engine comprising; an exhaust chamber 22 in direct communication with the ports E1- E3, and a short substantially-straight radially-extending fan-shaped passage 12` leading from the ports : E<SP>1</SP>1-E<SP>1</SP>6 to the chamber 22. the end of the passage 12 adjacent the chamber 12 having a, crosssectional area less than one-half of that of the chamber 22, there is provided a rotary valve 13 in the form of an acuteangled segment mounted on stub shafts 14 only one of which is shown, and positioned in the chamber 22 near the end of the passage 12, the valve serving to close the ports E<SP>1</SP>1-E<SP>1</SP>6 at the beginning of the compression stroke prior to the closing of the scavenging ports and being so' located that in one position it closes the passage 12, whilst when the latter is opened the valve lies in the-chamber 22 so that the exhaust gases entering the chamber neither undergo any sharp directional change nor encounter any restriction during expansion. The ports E<SP>1</SP>1-E<SP>1</SP>6 which are located above the scavenging and second stage exhaust ports are provided with guide ribs whilst holes 16, 17 in the cylinder head and wall, respectively, may be used to accommodate pressure indicators, not shown. The scavenging ports S5 may be replaced by an exhaust port, and ports E<SP>1</SP>5 and E<SP>1</SP>6 may be omitted. The 'scavenging air reservoir is indicated by the numeral 21.. In a double-acting engine two sets of first-stage exhaust-ports and one set of scavenging and second stage exhaust ports are arranged in the central portion of the cylinder; this embodiment, includes two rotary exhaust valves which are geared together.