Patent GB-315320-A (GB)
IPC: B60T7/12
Filed: 1929-07-10
Abstract: 315,320. Hallot, P. July 11, 1928, [Convention date]. Fluid-pressure.- A combined distributor and accelerator valve for compressed air brakes comprises a slide valve actuated by a pair of pistons of unequal diameter which define chambers connected respectively to the train-pipe, the auxiliary reservoir and the brake cylinder and adapted to give graduated application and release of the brakes; a second valve acting as the accelerator valve being also actuated by the pistons to connect the trainpipe to the brake cylinder. The invention also includes : a valve for restricting the flow of air from the auxiliary reservoir to the brake cylinder after the initial flow; a valve for preventing the brake cylinder from exhausting unless the auxiliary reservoir is charged to a predetermined value; a valve actuated by a speed responsive de. vice driven from the vehicle wheel axle to release air from the brake cylinder if the wheel tends to skid. As shown in Fig. 3, the speed controlled pressure regulator comprises a slide-valve 11 controlling ports 13, 15 connected respectively to the brake cylinder and to the atmosphere through a spring-loaded valve 16. The valve is connected to the spring-controlled sliding collar 6 of a centrifugal device the shaft 1<1> of which is suspended by links 23, 24 so that it may be swung by a connection from the brake piston to engage a roller 37 on the shaft with the vehicle wheel 38 to drivethe regulator when the brakes are applied. When the device is driven above a predetermined speed the valve 11 is held in position by the centrifugal device to disconnect the posts 13, 15, but if on account of the tendency to skid this speed is reached, these ports are connected as shown and the braking pressure is momentarily relieved and the wheel again assumes the speed of the train. This action is repeated until the speed of the train reaches the predetermined value when the braking pressure will fall to the minimum value determined by the spring 17. The centrifugal device may be mounted directly on the wheel axle. The distributor, Figs. 8 and 9, comprises a pair of pistons 83, 84 secured to a rod 87 and operating a slide valve 89. Normally, air from the train-pipe connected at C is supplied through the passage 97 to chamber 96, thence through the groove 98 to the chamber 99 which is connected to the auxiliary reservoir by the passages 100, R and the brake cylinder which is connected by the passage H to the port b is connected by the valve 89 to atmosphere by the port a. The chamber 104 on one side of the piston 84 is permanently connected to the brake cylinder while the other side of the piston is open to atmosphere. When the train-pipe pressure is reduced, the pistons and the valve 89 are moved to the left whereby the port b is connected by the valve cavity e to a port c in the valve seat which communicates with the auxiliary reservoir. Compressed air is thus supplied to the brake cylinder until equilibrium of the pressures on the pistons 83, 84 is re-established when the valve 89 is moved to lap position. The release of the brakes can similarly be graduated by increasing the train-pipe pressure by determined amounts. The auxiliary reservoir passage R, Fig. 9, contains a valve 102 which is normally seated by a spring S so as to leave open only the restricted passage 101. When however the passage R is firstconnected to the brake cylinder in the application of the brakes, the valve is unseated to allow a free flow of air but returns to its seat when the brake cylinder pressure reaches a predetermined value. The accelerator valve 93 is actuated by an extension 91 of the main valve rod 87 and a second slide valve 94 having a lostmotion connection with the rod 91. When the pistons 83, 84 move to the brake application position the ports shown in the slide valves and a port d connected to the brake cylinder are coincident and the train-pipe which is connected to the chamber 96, thus vents to the cylinder. This communication is cut off when the pistons 83, 84 move to the right but is re-established at each successive reduction of train-pipe pressure. Release of the brakes unless the auxiliary reservoir is charged to a predetermined pressure is prevented by the valve shown in Fig 7. The auxiliary reservoir pressure acts through the passage 141 on a spring- pressed piston 142 connected to a slide-valve 146 which controls the passage 148 connected to the brake cylinder exhaust passage a, Fig. 8, of the distributor. When the passage 148 is open the air from the brake cylinder is connected to the atmosphere through passages 149, 150. The Specification as open to inspection under Sect. 91 (3) (a) includes the following subjectmatter : A relief valve controlled by an inertia device shown in Fig. 5 (Cancelled) may be substituted for the device shown in Fig. 3. This device comprises a flywheel 44 with a threaded boss mounted on a screw 43 secured to the rotating shaft 1<1>. If the braking pressure tends to lock the vehicle wheel, the wheel 44 by reason of its inertia turns on the screw 43 and thus moves laterally in one direction or the other depending upon the direction of rotation of the shaft 1<1>, compressing the springs 50 or 51 and actuating the valve through the rod 55 and one or other of the sliding collars 48, 49. In a modification, which is of the kind described in French Specification 628,744, bevel gearing is provided whereby the secured shaft is driven in the same direction irrespective of that of the wheel axle and the flywheel is driven by a cotter pin on the shaft engaging a slot in the boss of the flywheel. Further, the device above described may be continued with those described in Specifications 154,174; 158,157, [Class 7 (iv), Internal-combustion engines, Igniting in], 169,989, and 183,460. This subject-matter does not appear in the Specification as accepted.