Patent GB-355704-A (GB)
Title: Control valve for compressed air brakes
IPC: B60T15/30
Filed: 1930-05-21
Abstract: 355,704. Fluidpressure brakes. COMPAGNIE GENERALE D'ELECTRICITE, 54, Rue La Boetie, Paris. May 21, 1930, No. 15676. Convention date, June 15, 1929. [Class 103 (i).] Valve mechanism for automatic compressed air brakes comprises two slide valves controlled by separate pistons one face of each piston being subject to brake pipe pressure, the other face of one piston to auxiliary reservoir pressure and the other face of the second piston to pressure in a secondary reservoir. One valve acts in part as an accelerator valve to connect the main pipe first to atmosphere and then to a chamber in applying the brakes. Graduated application and release of the brakes can be effected. With rapid reduction of brake pipe pressure, both reservoirs are connected to the brake cylinders. There may be two cylinders, the second one being rendered effective only for loaded vehicles and a further valve device is provided which when a predetermined pressure has been established in the one cylinder, connects in the second cylinder and restricts the supply to the cylinders. The valve devices 1, 2 comprise respectively pairs of slide valves 3, 4 and 5, 6 shown in two cross sections in the left and right-hand parts of Fig. 1. The piston chambers A, A2 are connected to the brake pipe U and the chambers B, C to the auxiliary and secondary reservoirs W, V respectively. The valve device M, Figs. 1 and 9 for restricting the supply to the brake cylinders C1, C2 and for connecting in the " load " cylinder C2 comprises two pistons 16, 18 normally held apart by a spring 19 to an extent determined by the rod 161 and a piston 17 freely arranged between them. The pistons are normally raised, Fig. 1, by a light spring 20 so as to hold open a non-return valve 13. The valve 13 may have an upper stem extending into a chamber above the chamber M, this upper chamber being connected to the passsage n to balance the pressure on the valve and a baffle may be arranged in the chamber I to prevent the air current from impinging on the piston 16. In the running position, Fig. 1, air from the main pipe is supplied to the valve chamber B and auxiliary reservoir W through passage a, slide valve 3 passage B and nozzle 8 and to the valve chamber C and secondary reservoir V from chamber B through non-return valve 10 and passage d. The brake cylinder C1 is open to atmosphere through passage e, and passages f, D, E, f<1> of slide valves 3, 4, and the cylinder C2 through passages g, h chamber F of the valve device M and port q<1>. When the brakepipe pressure is reduced the slide 4 is first moved and connects the brake pipe to atmosphere by passage a and passages G, D, E, f<1> of the valves 3, 4 and as the piston 1 moves to the extreme right-hand position, Fig. 2, the passage a is cut off from the atmosphere and is connected to a chamber x by the passages h<1>, E, g<1>. The capacity of the chamber x is sufficient to receive the air displaced by the valve pistons 1, 2, the piston 2 having moved as far as the stop 12 so that the valves 5, 6 are in the position shown in Fig. 5, whereby air is supplied from the auxiliary reservoir W and chamber B to the brake cylinder C1 through passages l, H, m, valve 13, of the valve device M, passages n, e. Air is also supplied from passage m through cock 11, restricting nozzles 14, 15, passage o, passage N around piston 17, passage n. Under the pressure in chamber I the piston 16, 18 at first move down to cut off the passage h and the cylinder C2 from the atmosphere, the piston 16 then overcomes the spring 19 causing the valve 13 to seat, Fig. 9, and the piston 17 to connect the passages g, o so that air is supplied also to the cylinder G through the nozzles 14, 15. To avoid momentarily re-opening of the valve 13 when the cylinder C2is connected, the piston may be arranged to effect this connection before the valve 13 seats. When the auxiliary reservoir pressure has equalized with the reduced brakepipe pressure, the valve 6 moves back to close the passage H. If the brake pipe pressure is rapidly reduced, the valve piston 2 overcomes the spring stop 12, the connection of the reservoir W with the cylinders C1, C2 is maintained by the branch of the passage H of the valve 5 and this valve uncovers the passage k<1> so that the reservoir V is also connected through the passage p, e1 to the cylinders. To effect a partial release after service braking, the brake pipe pressure is partly raised. The piston 2 then overcomes the spring stop 7 moving the valve 5 back to the position shown in Fig. 1, while the cavity k of the valve 6 connects the passages q, r permitting exhaust of the cylinders c1' c2 through passages e, n<1>, outlet plugs 31, 32. The piston 2 also uncovers the passage c and when the brake pipe pressure has equalized through it with that in the auxiliary reservoir the valve 6 is moved back by the stop 7 to cut off the cylinder exhaust. In the graduated release position of the valves 5, 6 the cavity L of the valve 6 connects passages s, t to vent the valve chamber C and reservoir V to a chamber y so that when the brake-pipe pressure has nearly reached normal value the piston 1 is returned and exhaust of the cylinders C1 is completed through passage e and passages and port f<1> of the valves 3, 4 and charging of the reservoirs W, V through passages a, b, d. The chamber y is vented to atmosphere through passage u in the release position of valves 3, 4. The cock 11 in the " load " position connects the " load cylinder C<2> to the triple valve and leads the air from the triple valve to the two nozzles 14, 15. In the " light " position the cock connects the cylinder C<2> to the atmosphere and the air from the triple valve only passes to the nozzle 15. The apparatus may be used for goods and passenger trains, the cylinder C<1> alone being used the passage to the cylinder C<2> being stopped by a plug. The cock when in the " passenger train " position corresponding to " load " position allows quick application and release through nozzles 14, 15 and outlets 31, 32 respectively.