Patent GB-1313393-A (GB)
Title: Piston-and-cylinder device having a rolling-diaphragm seal
IPC: F25B9/14
Filed: 1970-04-14
Abstract: 1313393 Pistons PHILIPS GLOEILAMPENFABRIEKEN NV 14 April 1970 [17 April 1969] 17668/70 Heading F2T [Also in Division F1] A hot-gas engine, cold-gas refrigerator, compressor or other piston-and-cylinder device comprises a piston 2 bounding a working space 3 and a further space 7 (crankcase) containing a compressible medium (gas), a rolling diaphragm 5 disposed between the piston and cylinder separating a first space 6 from a second space 6a which is either in open communication with the further space 7 as shown in Fig. 1 or separated from the further space by a seal (24), Fig. 3 (not shown), and a seal 8 which separates the first space from the working space, the rolling diaphragm being subjected to a constant pressure difference by maintaining the pressure in the second space at a constant difference from that in the first space. The seal 8, as shown in Fig. 1, is a piston ring provided with radial grooves 8c on its lower face; in use, the ring acts as a non-return valve to establish a pressure in the space 6 equal to the maximum pressure in the space 3. The area 2c of the piston may be predetermined to maintain upon movement of the piston either a constant volume in the space 6 or, as for Fig. 1, a volume which varies to produce pressure variations in this space which are equal to and in phase with pressure variations in the spaces 6a and 7. A non- return valve 32 returns gas which has diffused through the rolling diaphragm. In Fig. 3, the second space (25) is sealed from the crankcase by a piston ring (24) which is provided with radial grooves (24c) on its upper face. The areas 2c and 2e of the piston are predetermined to maintain upon movement of the piston a constant volume both in the space above (6) and in the space below (25) the rolling diaphragm.  In an embodiment of a hot-gas engine of the displacer-type, Fig. 2, a displacer 10 operates in an expansion space 12 while the piston 2 operates in a compression space 11, the two spaces communicating with each other via a cooler 13, regenerator 14 and heater 15. The displacer rod 17 passes through a hollow piston rod 4 and both rods are connected to a rhombic driving gear 19. In this embodiment, a further rolling diaphragm 20 and a further piston ring 23 are provided between the piston and the displacer rod and the spaces 6 and 21 (first and third spaces) are interconnected by ducts 22. In Fig. 4 (not shown) which is a modification of the engine shown in Fig. 2, piston rings (26, 28) separate second and fourth spaces (27, 29) below the rolling diaphragms (5, 20) from the crankcase space (7). The piston rings are provided with radial grooves facing the rolling diaphragms so that the spaces adjacent the rolling diaphragms contain a pressure equal to the maximum pressures in the spaces on the other sides of the rings. In an alternative arrangement, the radial grooves in the piston rings may be provided remote from the rolling diaphragms to establish adjacent the rolling diaphragms a pressure equal to the minimum pressure in the spaces on the other sides of the rings. In further arrangements, more than one piston ring may be employed, the seals may be housed in grooves in the cylinder or displacer rod, and instead of providing radial grooves in the faces of the piston rings, communication between the bottom of the piston ring grooves and the adjacent spaces may be provided either by a duct in the piston or grooves in the piston ring groove walls of the piston, cylinder or displacer rod. Instead of piston rings being employed, each piston seal may be formed by a narrow gap so that the average pressure of the crankcase will be produced on opposite sides of the rolling diaphragm. A generator or electric motor may be coupled with the driving gear.