Patent GB-713242-A (GB)
Title: Improvements in and relating to hydraulic buffers and draw-gear
IPC: B61G9/08
Filed: 1949-11-04
Abstract: 713,242. Pistons; cylinders. FITZJOHN, A. P., and TURTON, PLATTS & CO., Ltd., G. Nov. 1, 1950 [Nov. 4, 1949], No. 28334/49. Class 122(1) [Also in Group XXXII] A cylinder 80 and piston 81, Fig. 1, in a buffing and draw gear for a vehicle define oil chambers A, B connected by a passage 91a in the piston, the gear also comprising means 95 associated with the cylinder co-operating with the piston 81 for affording progressively increasing resistance to displacement of oil through the passage 91a on relative piston and cylinder inward movement, compressed air cushioning means 83 actuable on the oil in the oil chamber of the piston, and an oil chamber 100a circumferentially between the cylinder and the piston intermediate the ends of the piston and communicating at all times with the oil chamber in the piston. In the construction shown in Fig. 1, applicable to vehicle draw and buffing gear, a yoke 79 slidably mounted on the vehicle frame has surfaces 99, 100 respectively engageable with stop members 97, 98 provided on the hydraulic cylinder 80 and the rod 82 of the piston 81. The stop members 97, 98 are also engageable with respective stops (not shown) on the vehicle frame. Liquid is contained between the end of the cylinder 80 and the piston 81. and within a bore 89 in the piston rod 82. The bore 89 is connected by ports 88 with the annular space 87 between the piston rod 82 and cylinder 80. Liquid in the space 87 acts on an annular piston 86 to compress air in a further annular space 83. In operation, on movement of the yoke 79 to the left (corresponding to a draught shock), the stop 97 on the cylinder abuts the corresponding stop on the vehicle frame, and the yoke 79 engages the stop 98 and drives the piston 81 inwardly within the cylinder. Liquid flow from the space A to the space B is metered by the action of grooves 96 in a stem 95. On movement of the yoke 79 to the right (buffing), the stop 98 engages its corresponding stop on the frame, and the yoke 79 engages the stop 97 and drives the cylinder 80 over the piston 81. In a modification (Fig. 2. not shown), the stem 95 may be carried by a piston slidably mounted within the hydraulic cylinder. The space between the floating piston and the end-wall of the cylinder is filled with compressed air. A further external compressed air chamber, into which oil may be displaced. is connected with the space B. The floating piston may be free to travel within the whole cylinder space or may be limited by a stop. In the construction shown, Fig. 3, respective liquid and air cylinders 122 and 121 are slidable over opposite ends of a common hollow piston 120. A floating piston 145 separates the interior of the piston 120 into an air chamber 144 and a liquid chamber 143. Flow of liquid from the cylinder 122 to the chamber 143 is metered by a grooved stem 146 and flow of air from the cylinder 121 to the chamber 144 is restricted by an orifice 132. Liquid in an annular space 128 forms a gland for the cylinder 121 and is acted on by an annular piston 127 exposed at one end to pressure of air in the cylinder 121. Specification 713,318, [Group XXXII], is referred to.