Patent GB-981012-A (GB)
Title: Fluid pressure control equipment
Inventor: MARSH GERALD CRANTON
IPC: B60T13/46
Filed: 1962-08-28
Abstract: 981,012. Fluid-pressure braking systems. GRESHAM & CRAVEN Ltd. July 26, 1963 [Aug. 28, 1962], No. 32983/62. Heading F2F. A fluid-pressure control arrangement for a vacuum or pressure-controlled device, particularly for a relay valve controlling the degree of operation of railway brakes so as to enable a goods train of which only the locomotive or the locomotive and only some of the goods wagons are fitted with brakes to be automatically given an initial partial braking followed by a delay period after which braking is increased slowly to the level set by the driver, comprises a first valve operable to a first and a second position by which is provided alternative first and second fluid paths respectively through a common choke arranged downstream thereof, a second normally open valve arranged in series with the first valve in the first fluid path and operable to its closed position upon pressure in that path reaching a first lower predetermined value, first means for delaying the rate of rise of pressure in the first path upstream of the second valve subsequent to the closing of the latter, and second means responsive to the pressure upstream of the second valve reaching a second higher predetermined value to operate the first valve to its second position so that fluid flows through the choke via the second path. As shown, a railway vehicle braking installation of the kind in which the degree of vacuum in a train pipe 11 is reduced to apply the brakes comprises a driver's valve 12 which controls the degree of vacuum in an equalizing reservoir 13 connected to an exhauster 15 via a choke 19 and check valve 17. The train pipe 11 is also connected to the exhauster via a cut-out valve 16 and the check valve 17, and is connected with the brake valve 12 and with a relay valve 14 in known manner whereby the relay valve controls the admission of air to the train pipe in accordance with the degree of vacuum in the equalizing reservoir, so that the degree of vacuum in the train pipe is controlled. For this purpose reservoir 13 is connected with a control chamber of the relay valve through a control arrangement as set out above. As shown this comprises two electromagnetic valves 31, 33 each comprising a lower valve element 43 open when de-energized and an upper valve element 39 open when energized. The electromagnets are controlled by a switch 70 having three positions as indicated on the drawing. In the " FREIGHT UNFITTED OR PARTIALLY FITTED " position of switch 70 relays 31 and 33 are both energized, the former through a normally closed switch 35 responsive to the degree of vacuum in a reservoir 34. The initial path of the air flowing from reservoir 13 to the control chamber of relay valve 14 is then via pipe 49, the upper valve element of valve 33, passage 46, passage 45, pipe 47, valve 58 which is initially open owing to the vacuum in chamber 62 acting on diaphragm 61 overcoming a spring 65 and causing a pin 60 to lift the valve, pipe 57, upper valve element 39 of valve 31, passage 42, choke 52 and pipe 54. Owing to the presence of choke 52 the relay valve 14 responds more slowly to apply the brakes gradually. At the same time air passes via a continuation of pipe 47 and a choke 66 to the reservoir 34 so that as pressure rises in the train pipe a corresponding rise takes place in the reservoir 34 and hence in chamber 62. Upon a predetermined degree of reduced vacuum being reached, spring 65 overcomes the partial vacuum in chamber 62 and valve 58 closes to block the above path through the choke 52 preventing further increase of brake application. Pressure in reservoir 34 however continues to rise until at a predetermined greater diminution of vacuum switch 35 opens deenergizing valve 31 whereby a second path between the reservoir 13 and relay valve 14 is opened via the choke 52 since air can now pass via lower valve element 43 of valve 31 and passage 42. Increase of brake application is thus resumed after an interval sufficient to allow for bunching of the wagons of the train not fitted with brakes. When the switch 70 is in the " FREIGHT FULLY FITTED " position only the valve 33 is energized at all times and air takes the second path only through the choke 52 to give a gradual increase of brake application without a break. In the " PASSENGER " position neither valve is energized and the control arrangement is inoperative. On reduction of the vacuum in reservoir 13, air is passed from the reservoir 13 via pipe 49, passage 48, the open lower valve element of valve 33, passage 55 and pipe 54 direct to the relay valve control chamber. The relay valve then responds immediately to any change in the degree of vacuum in reservoir 13. Specification 917,390 is referred to.