Patent GB-201076-A (GB)
Title: Improvements in or relating to vacuum automatic brake apparatus for railway and the like vehicles
IPC: B60T13/46
Filed: 1922-09-14
Abstract: 201,076. Pinder, T. Sept. 14, 1922. Fluid - pressure. - In automatic vacuum-brakes, a valve is provided between the train pipe and the bottom of the brake cylinder to recuperate the vacuum in the chamber part of the vehicle cylinders without releasing the brakes. The valve is arranged to open on the cylinder side of its seating, and is operable in a certain cycle by the differing pressures in the train pipe. One form of valve, for performing the cycle at a prearranged vacuum, is shown in Fig. 1. The main chamber 1 communicates with the train pipe by a passage 2 and with the top of the brake cylinder by a non-return valve (not shown). It also communicates, by a. passage 5, chamber 3, and passage 4, with the bottom of the brake cylinder. The passage 5 may be closed by the valve 6, which is faced with a flexible rubber sheet 7. The valve 6 has a hollow stem 8, which has a pin-and-slot connection with a spindle 9 carrying a diaphragm 13 which is adapted to close a vacuum chamber 14. The chambers 1, 14 are connected by a passage 15, closed at one end by a non-return valve 16, and at the other end by a ball valve 17, which is held off its seat by a spring until the chamber 14 is exhausted to the prearranged vacuum. In the position shown, the pressures in the chambers 1, 14 are equal, the diaphragm 13 has been forced outwardly by the spring 18, and the valve 6 is consequently unseated. When air is now exhausted from the train pipe, both the top and bottom of the brake cylinder are exhausted, and air is exhausted from the chamber 14 until the ball 17 seats. When air is admitted to apply the brake, the diaphragm 13 is moved to the right and causes the valve 6 to seat. When air is again exhausted to recuperate the vacuum in the chamber part of the cylinder, the difference in pressure in the chambers 3 and 1 causes the valve 6 to seat more firmly, and an extension 8<x> on the valve stem 8 pushes the ball 16 off its seat. When the vacuum is again destroyed, air enters the chamber 14 by forcing the ball 17 off its seat and when the pressures in the chambers 1, 14 are equalized, the springs 18, 12 serve to unseat the valve 6, and the diaphragm 13 takes up position ready to recommence the cycle. Fig. 2 shows a modification for performing the cycle on complete destruction of vacuum. The chambers 1, 3 and their passages 2, 4, 5 are arranged as before, but the diaphragm 13 now closes the chamber 1 to atmosphere and is normally held raised by a spring 18. The valve stem 8 carries shoulders to each of which is pivoted a lever 20, the inner ends of the levers being so positioned that when the spindle 9 of the diaphragm 13 moves downwards it forces the outer ends of the levers upwards, and when the spindle subsequently rises, the levers grip it and the valve 6 is caused to seat. With the parts in the position shown, when air is exhausted from the train pipe, the whole apparatus is exhausted, the diaphragm 13 is depressed, and the lower end of the spindle 9 passes between the levers 20. When air is admitted to apply the brake, the spring 18 raises the diaphragm 13 and the valve 6 seats, closing the passage 5. When air is again exhausted to recuperate the vacuum in the chamber part of the cylinder, the valve 6 is retained on its seat by the difference in pressure in the chambers 3, 1, and the spindle 9 moves downwards until the inner ends of the levers 20 reach recesses 21 in the spindle, so that the outer ends of the levers fall by gravity. When air is again admitted to the train pipe, the valve 6 drops by gravity, and the diaphragm 13 and spindle 9 rise, so that the parts are again in position to recommence the cycle.