| 摘要 |
752,199. Pistons. FORD MOTOR CO., Ltd. April 8, 1954 [April 13, 1953], No. 10336/54. Class 122(1) [Also in Group XXIX] The piston of a piston-and-cylinder servomotor for the steering unit of a motor vehicle (see Group XXIX) is made up of sections with limited relative movement allowed between the sections so that, during recovery strokes, there is free communication between both ends of the cylinder but, during power strokes, such communication is shut off, and, in addition, the pressure on the sealing means between the piston and the cylinder is lowered during recovery strokes so as to minimize wear. In an embodiment wherein the piston is fixed and the cylinder moves over the piston, the motive fluid supply and exhaust passages pass through the stem of the piston and comprise a passage 52 and port 83, and a passage 51. The piston itself comprises angled rims 59 pressed'towards each other by springs 68 and with a ribbed ring: 62 located between them. A pair of piston sections 73 which can slide on the rims 59, are pressed apart by a coil spring 77 and house a resilient ring 82 acting as the normal piston sealing ring. A further resilient sealing ring 64 is located around the ring 62. With no pressure fluid applied to the cylinder, sections 73 are kept apart by the spring 77, and free communication between the two sides of the piston is provided by passages 79 in the section 73 and by clear. ances between the ring 64 and the adjacent parts of sections 73. If pressure fluid is applied to one end of the cylinder, it will act on the adjacent section 73 to force the latter into contact with the ring 64 to close off the passage between the two ends of the cylinder. |
