Patent GB-276453-A (GB)
Title: Improvements in or relating to two-stroke-cycle internal-combustion engines
IPC: F01L5/04
Filed: 1926-06-07
Abstract: 276,453. Alston, C. H. T. June 7, 1926. Two - stroke - cycle engines; cylinders, combustion chambers for and ports of. - In engines wherein a pump supplies a charge to a combustion chamber separated from the working cylinder by a valve, the charge is stratified in the pump, so that when completed a layer of combustible mixture is near the delivery port of the pump and an inert gas such as air is in the pump chamber remote from the port. Ignition of the combustible part of the charge is started in the combustion chamber before the pump is isolated from that chamber and the air is delivered into the combustion chamber after ignition has taken place. As shown in an engine with a cylinder of two diameters the pump 11 draws mixture from a carburettor through the passage 36 during the first part of its down stroke; the inlet ports 37 direct the mixture to the upper end of the pump chamber. At the end of the suction stroke after the passage 36 has been closed air is drawn into the bottom of the pump chamber through the downwardly directed ports 38. The piston is formed with a channel 17 which allows the pump to deliver through a passage 16 into a combustion chamber 15 in communication with the working cylinder 10 through the passage 26. The admission of mixture to the pump, the delivery from the pump, the communication between the chamber 15 and cylinder 10 and the exhaust outlet 27 are controlled by two piston valves 19, 20 linked so as to move together by rods outside the valve casing; the composite valve moves 70‹ behind the main working and pump pistons. The combustion chamber lies between the two valves and contains a plug 40, with tapered lower orifice 42, the lower valve carrying a correspondingly tapered plug 43. Assuming a charge has been drawn into the pump 11, on the upstroke of the main pistons the combustible charge is delivered into the chamber 15, and is ignited by means of the plug 44; this takes place before the piston valve 19 closes the passage 16 so that the air charged is delivered by the pump 11 while the charge is burning. After the orifice 16 is closed, the plug 43 on the valve 19 acts as an auxiliary pump plunger to drive the final air charge into the combustion chamber. Before the main pistons reach top dead centre the passage 26 is opened and the hot charge transferred to the working chamber. The port 29 in the valve 20 connects the cylinder exhaust port 36 to the pipe 30; to remove products of the previous cycle from the combustion chamber a notch 18 is cut in the piston head to connect the passage 16 to the main cylinder 10 at the end of the out stroke and while the exhaust ports are still open. In each cycle a small amount of products is trapped, which is compressed on the up stroke, so that there shall not be a sudden fall of pressure as the charge flows from the combustion chamber into the cylinder. The minimum clearance is allowed in both working and pump cylinders. The passage 26 could be used as the exhaust port and the lower part of the valve 19 could control the admission of air to the pump. The passage 16 is enclosed in the water jacket to cool the gases from the pump. The power piston may be reduced except at its upper end and the double main piston bear on the cylinder through rings at the upper and lower ends only; the ports are formed with undulating edges 46, 47, Fig. 3, so that the piston rings 48 shall at all times be supported. The combustion chamber may be formed within the walls of the double valve 51, Fig. 4, the upper edge of the valve controlling the exhaust outlet. An independent poppet valve worked with the piston valves from an overhead cam shaft may be used for the exhaust. In another modification a spherical combustion chamber is formed between two co-axial piston valves or between two valves 50, 55, Fig. 7, one of which, with its axis transverse to the cylinder axis, controls the cylinder inlet 54 and exhaust 53.