Patent GB-695109-A (GB)
Title: Improvements in or relating to pneumatic buffing appliances
IPC: B61G11/12
Filed: 1949-11-04
Abstract: 695,109. Pistons. FITZJOHN, A. P., and TURTON, PLATTS & CO., Ltd., G. Nov. 1, 1950 [Nov. 4, 1949; April 24, 1950], Nos. 28333/49 and 10059/50. Class 122(i) [Also in Group XXXII] A pneumatic buffing appliance comprises a cylinder 6, Fig. 3, and piston 55 having an oil seal 22 disposed between mechanical sealing means 23, 23, a spring restrained member 15 forming a displaceable part of the pressure end face of the piston and actuable (under air pressure in the cylinder) upon the oil in the oil seal 22, an end wall a to the cylinder defining a supplementary air chamber 11 coaxial with the cylinder 6, and an orificed spring-pressed valve 12 in the wall a adapted to open up the supplementary chamber 11 to the cylinder 6 on compression of air in the cylinder 6 by inward movement of the piston 55. The valve 12 has restricted-flow ports 13. A plunger 51 rigid with the valve 12 is slidable within a bore 57 in the rod of the piston 55. The bore 57 forms an auxiliary chamber which is open to atmosphere by a passage 58, and is connected with the chamber 11 by a bore 52 in the plunger 51. The passage 58 includes a filter 62. The bore 52 has non-return valves 53, 54 at each end, which prevent flow back from the chamber 11 to the chamber 57. In operation, on compression, the piston 55 compresses air in the cylinder 6, and the valve 12 opens to admit air to the chamber 11. On rebound, the valve 12 closes, and flow between the chamber 11 and cylinder 6 is restricted to the ports 13. At the commencement of the compression stroke, the passage 58 is cut off by the plunger 51. Air compressed in the chamber 57 passes through the valves 53, 54 to the chamber 11, and cylinder 6, if the pressure in the latter has dropped (due to leakage or other causes). In the construction shown in Fig. 4, the auxiliary chamber is constituted by the space 70 of the cylinder 6 behind the piston and is connected to the chamber 11 by an external pipe 72. On compression, air is drawn into the auxiliary chamber 70 through a non-return valve 71, and on rebound, air compressed therein is pumped through non-return valves 73 and the pipe 72 to augment pressure in the chamber 11 and cylinder 6. In a modified construction (Fig. 5, not shown), the non- return valve 71 is replaced by an axial slot at the outer end of the piston rod. The slot enters the chamber 70 towards the end of the compression stroke and connects it with the atmosphere. In each of the above constructions, the auxiliary chamber is provided with a pressure relief valve. The invention is applicable to buffers for vehicles, in which case the buffer head may be carried by the piston rod 56. Alternatively (Fig. 1, not shown), the buffer head may be carried by a cylinder slidably mounted on the exterior of the cylinder 6, and within a concentric outer guiding cylinder which is rigid with the cylinder 6. The interior surface of the buffer head 2 bears on the outer end of the piston 56. In a modified construction of main piston (Fig. 2, not shown), oil in the space 22 is charged from an external source via a non- return valve mounted in a recess in the piston rod 56.