GB906013A - Improvements relating to fluid pressure apparatus including an abutment movable by the application thereto of fluid under pressure - Google Patents

Abstract

906,013. Pneumatic single stroke apparatus. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. Dec. 17, 1959 [Dec. 19, 1958], No. 41051/58. Class 8(2). A sequentially controlled apparatus for pneumatic rams, e.g. for propelling mini cars and the like in collieries, comprising a cylinder T, Fig. 5, with a piston Q having a piston rod connected to a pushing arm, the piston being driven by compressed air from a supply U through the control apparatus, Fig. 3, comprising an inlet K permitting the air to pass through an adjustable choke F, to a passage P and thence to the piston Q, with sufficient pressure to overcome bore friction and enable the said piston to complete the first stage of its forward stroke. At the same time air passing through a fixed charging choke G increases the pressure in the timing reservoir R until at pressures predetermined by the respective cross sectional areas of the pistons C 1 and C 2 or the compressive stresses in that co-operating springs the pistons sequentially open the auxiliary valves Bi and B 2 respectively, the poppet valve D opening and the discharge poppet valve E being held closed under the pressure of air from the inlet K, to augment the flow of air through the adjustable choke F, to the piston Q enabling the piston at or after completion of stage 1 to carry through and complete stages 2 and 3 of its stroke. A single delay mechanism, Fig. 1 (not shown), may be used but preferably a double delay mechanism, Fig. 3, is used with the addition of a further similar delay unit connected to the inlet U bar, its output connected, via a double check valve CV, to the other side of the piston Q so that at a predetermined time, pressure is transmitted to the other side of the piston to produce an opposing thrust and the fourth and last stage of the forward stroke, which is one of reduced thrust. During the discharge stroke of the ram the exhaust passes along passage P through the check valve E and the supply control valve to atmosphere. The schematic arrangement of the complete apparatus is shown in Fig. 5. The restrictive orifices F 2 and F 3 are formed by the adjustable stop S 1 and S 2 co-operating with the auxiliary valves B 1 and B 2 , whose uncontrolled operation is prevented by the check valves E 2 and E 3 . The charging choke G is preferably replaced by a check valve, having a permanent vent and which opens when the pressure in the inlet K falls below that in the timing reservoir R, thus preventing the possibility of an accidental fresh stroke being made before dissipation of the pressure in said timing reservoir.