Patent GB-190818782-A (GB)
Title: Improvements in Valve-gear for Four-cycle Internal Combustion Engines in which Compressed Air is Employed to Scavenge the Cylinders.
Inventor: HELLMANN WILHELM
Filed: 1908-09-07
Granted: 1909-09-07
Abstract: 18,782. Hellmann, W. Sept. 7. Gas and like engines.-Valve mechanism, for fourstroke-cycle engines in which compressed air for scavenging is admitted through the main inlet valve, and at the end of the suction stroke air at atmospheric pressure is drawn through the mixing - chamber and inlet valve, in order to prevent both premature ignition and back ignition, is arranged so that the compressed air is separately controlled and can only enter the combustion chamber while the inlet valve is being opened. A number of arrangements for carrying out this process'are described'in some of which means are provided for controlling the supply of gas by the governor, and for cutting off the scavenging air altogether below a certain load. In Fig. 1, the inlet valve 5 is shown connected to a sleeve 6, controlling the compressed air supply 1, air supply 2, and gas supply 3. As the inlet valve begins to lift, compressed air is admitted through the port 12 ; the sleeve 6 next closes the port 12 and opens the gas and air ports. A regulating-valve 7 for controlling the supply of gas according to the load on the engine is operated independently of the inlet valve, and is raised during the suction stroke, so that towards the end of the stroke the valves are in the position shown in Fig. 3 ; in this position the compressed-air port is closed by the valve 7, and the gas port by the sleeve 6, while atmospheric air is drawn through the mixing chamber as shown by the arrow. The valve 7 is connected to its spindle 18 by a screw pair 19, 20 and is prevented from rotating, so that the valve is adjusted longitudinally on its spindle when the spindle is rotated by means of a governor rod 21 carrying a circular rack which engages with a pinioo 23 on the spindle. When the speed of the governor increases, the valve 7 is lowered on its spindle, the opening of the gas port is delayed, and air only is admitted to the cylinder during the earlier part of the suction stroke. Modifications are described in which the valve 6 is replaced by a piston valve arranged in a separate casing, and it is stated that a rotary slide valve may be used, or there may be a rotary slide valve controlling the compressed - air and atmospheric - air ports and a separate member for the gas ports. In one arrangement a separate piston valve is used for the compressed air and separate beat valves for the air and gas, the three valves being on one spindle. In another modification the valves 5, 6 are concentric but separate. When the valve 6 is separate from the inlet valve 5, it may be operated so as to admit compressed air when the inlet valve first opens, and to close the compressed-air port until after the closing of the inlet valve. In many of the modifications, the valve 7 is not used, and governing is effected by throttle valves in the air and gas supply passages ; and in some of the modifications, the positions of the compressed air, air, and gas ports are interchanged. In one modification, a mixture of gas and air is supplied through the passage 3, and a separate port is provided in the valve 6 for the admission of air from the passage 2 at the end of the suction stroke. In another modification, a sleeve connected with the inlet valve controls the air port and a port for gas or for a mixture of gas and air, while an independently-operated cylindrical slide valve in a separate casing controls the supply of compressed air. In another arrangement, a double-beat mixing-valve operated from the same lever as the inlet valve, controls the air and gas supplies, while a cylindrical slide valve controls the compressed air supply for scavenging, and admits atmospheric air after the mixing-valve is closed. In further modifications, the compressed air is caused to exercise an injector action on the gas or mixture ; governing is effected by delaying the admission of gas so that at reduced loads the injector action at the beginning of the stroke forces only air into the cylinder. In one arrangement, the compressed air passes through a nozzle formed in a tubular valve which opens the air and gas ports before the compressed-air port is closed. In the form shown in Fig. 12, a fixed nozzle 8 is provided in the casing of the inlet valve, a valve 36 controls the air supplies, and the gas supply is controlled by a valve 41 under the influence of the governor ; leakage of compressed air between the valve 36 and the nozzle 8 is prevented by forming the valve with a nozzle 39 within the nozzle 8. The air valve may be in two parts arranged above and below the injector nozzle and operated together. Arrangements are also described in which a single valve controls the compressed-air and atmosphericair supplies to two cylinders or to the two ends of a double-acting cylinder. In Fig. 14 the valve is shown in two parts 44, 45 mounted on the same pair of spindles. When the inlet valve 5<a> opens, the valve 44 admits compressed air from the passage 1 through the port 42 ; during the suction stroke in the left-hand cylinder, the valve 44, 45 rises to the position shown in Fig. 17, first closing the port 42, then opening a port 43 to admit atmospheric air to the left-hand cylinder, and finally opening a port 46 to admit compressed air to the right-hand cylinder ; during the suction stroke in the right-hand cylinder the valve descends, first closing the port 46 and then opening a port 47 to admit atmospheric air to the right-hand cylinder. A valve, not shown, under the influence of the governor admits gas to the passage 3, and is operated so as to close before the inlet valve. In another arrangement the air passes from the ports 43, 47 to separate mixing-valves, and the mixture of gas and air is then led to the passages 3. When working below a certain load, the gear of the valve 44, 45 is thrown out of action, by hand or by the governor, and the valve remains at rest in its midposition, with the ports 42, 46 closed, and the ports 43, 47 open, so that scavenging does not take place. This may be effected by moving the cam bowl out of line with the cam, and causing it to run on a circular disk. Another arrangement in which a single valve controls the air supplies to two combustion chambers is shown in Fig. 19. The outer edges of the hollow recessed piston valve 48 open and close ports in the valve casing to the compressed air supply 1, while the inner edges of the valve open and close the same ports to the atmospheric air supply 2, similarly to the action of an ordinary D-slide valve. In modifications of this arrangement, a rocking slide valve or a valve similar to the trick slide valve may be used. In the arrangement shown partially in Fig. 25, a cylindrical member 54 connected to the valve, controls the compressed air supply 1 ; in the position shown, a double port opening 58, 59 is obtained for atmospheric air, and the part 54 instead of being continuous, may have a port, as shown, or several ports to give increased opening for the compressed-air supply.