Patent GB-606986-A (GB)
Title: Improvements in internal-combustion-operated free-piston compressors and gas-generators having pneumatic starters
IPC: F02B71/02
Filed: 1946-01-22
Abstract: 606,986. Free-piston gas producers and compressors. PESCARA, R. P. Jan. 22, 1946, No. 2160. Convention date, Dec. 26, 1944. [Classes 7 (i), 7 (ii) and 7 (v)] In an internal-combustion operated freepiston compressor or gas producer having at least one free piston assembly and arranged to be started by admitting a charge of gas under pressure into a starting space (other than the combustion chamber) which is bounded by a portion of the free-piston assembly, means are provided to put the starting space periodically into communication with a space at an instantaneously lower pressure and are so arranged that during each complete oscillation of the free-piston assembly two separate communication periods alternate with two closed periods the two closed periods extending both before and after the instants when the free-piston assembly occupies its inner and outer dead points respectively. The invention is described as applied to an opposed-piston free-piston compressor having a double-acting compressor associated with one power piston and an accumulator piston operating in a pneumatic accumulator cylinder associated with the other power piston. The inner side of the compressor supplies air to the engine case for scavenging and the outer side supplies air for use externally. The engine is started by introducing starting air into the pneumatic accumulator cylinder 2 through a starting valve 20, Fig. 1, coupled in known manner to a piston 21 provided with a non-return valve 23. Fig. 2 shows a portion of the wall of the accumulator chamber with a transfer port 13 associated with it. The port establishes communication between the accumulator cylinder and the engine case 6 at the inner side of the accumulator piston during each stroke of the piston 11. After the engine has been started the pressure in the accumulator cylinder is higher than is desired. The pressure when the transfer port is uncovered is, however, higher than in the engine case so that a progressive reduction in pressure is obtained until the desired pressure is reached in the accumulator cylinder. The accumulator cylinder may be provided with make-up air from the engine case through the port 13. As shown a non-return valve 15 is provided in the port 13. Thus a restricted passage is provided for the flow of air from the accumulator to the engine case by way of a port 16 in the valve. For the flow from the engine case to the accumulator the valve opens and provides a passage of larger area. A return spring 17 is provided for the valve. It is stated that the accumulator chamber need not necessarily be connected periodically to the engine case but may be connected to atmosphere or where a scavenging pump is provided at the rear of the accumulator piston the accumulator can be connected periodically to this pump. The invention is also applicable to a free-piston compressor or gas generator which is started by supplying compressed air to a compressor cylinder or other starting space. In this case it is necessary to provide means for closing during normal running the transfer duct by which the starting air is allowed to escape progressively from the compressor cylinder or starting space.