Patent GB-598934-A (GB)
Title: Improvements in or relating to internal combustion engines having means for cooling a piston by air or gas
IPC: F01P1/04
Filed: 1945-09-13
Abstract: 598,934. Cooling pistons. SULZER FRERES SOC. ANON. Sept. 13, 1945, No. 23614. Convention date, Sept. 15, 1944. [Class 122 (i)] [Also in Group XXVII] A piston has an internal chamber of constant volume which is closed during at least part of the stroke except for a passage lying close to the combustion surface or crown of the piston and communicating with a space in an engine containing relatively cool air or gas the pressure of which varies substantially during each stroke, the arrangement being such that due to this pressure variation some air or gas is caused to flow through the passage to or from the chamber during each stroke for cooling the piston. In a modification, the piston has two internal chambers which communicate with one another through the passage lying close to the piston crown each of which communicates through a non-return valve with a space in an engine containing relatively cool air or gas, the pressure of which varies substantially during each stroke, one non-return valve allowing air or gas to pass from a chamber to the space and the other allowing air or gas to pass from the space to the other chambers. Fig. 1 shows a free piston gas generator in which a power piston 5 is cooled by air from an energy storage cushion 16. The air passes through a passage 21 in the piston to an annular passage 20 between an insert 18 and the interior surface of the piston crown 19. From the annular passage the air passes to a storage space 22 inside the piston. After the piston has travelled some way on its compression stroke the air from the storage space 22 returns to the cushion 16. The size of the space 22 can be chosen so that the cooling of the piston by air flowing out of the space 22 continues after the piston has commenced the outward stroke. An automatic valve 26 may be provided to pass air from a compressed air source 25 periodically to the storage space 22, and then away to atmosphere. Instead of the passage 21 being connected to the energy storage cushion 16 it may be connected to a compressor space 3 as shown by dotted lines. The storage cushion 16 may have a cooling jacket 57. Fig. 6 shows a modification in which storage spaces 51 and 52 are formed in the piston and are connected by an annular space 50 and an annular diffuser 55. During a working stroke air from the storage cushion 16 passes through the spaces 51 and 50 and diffuser 55 to the space 52. On the return stroke air flows from the space 51 to the space 52 and back into the cushion. Non-return valves 53, 54 are provided. A cooling coil 59 is arranged in the storage cushion. A cooling coil may be arranged outside the cooling jacket 57 of Fig. 1. In Fig. 6 if a second energy storage cushion space 60 is employed the space 52 may be connected to this instead of to the cushion 16. In a modification the space 60 can be connected through a passage 61 and space 52 to the passage 50 and the space 51 instead of opening into the cushion 16 has an end 62 cooperating with a port 63 connected to the atmosphere. During the compression stroke air escapes from the cushion 60 until the port 63 is covered when the air in the cushion is compressed. The space 60 may be provided with a valve for admitting additional compressed air or alternatively the pipe 64 may be connected to a pressure space in which the pressure is regulated for example in accordance with the output. A number of ways of forming the passage adjacent the surfaces to be cooled are described. The pipe 21 may have a flange having a spiral groove on its face adjacent to the piston crown the groove forming a spiral passage through which the air passes to the chamber 22. Alternatively the. pipe 21 may lead into a spiral passage in the crown of the piston. In another arrangement the annular passage 20 does not open directly into the chamber 22 but is connected to an annular channel in the piston crown the annular channel opening into the chamber 22. An electrically driven three-way cock may replace the automatic valve previously referred to.