Patent GB-163435-A (GB)
Title: Improvements relating to train speed controlling systems
IPC: B61L3/00
Filed: 1920-02-12
Abstract: 163,435. Belfield, R., (Westinghouse Air Brake Co.). Feb. 12, 1920. Fluid-pressure.-Relates to apparatus of the kind described in Specification 155,369 for imposing various speed limits on a train by means on the track according to the nature of the signal indication. If through lack of attention or incapacity, the driver fails to depress a penalty valve, after passing a caution signal, the low speed limit is imposed instead of the medium speed limit. Except when the low speed limit is thus imposed the imposition of this limit and of the medium speed limit is delayed after the corresponding signal indication has been passed, for an interval dependent upon the speed of the train at the time. If an application of the brakes is initiated, a predetermined minimum train-pipe pressure reduction is effected before the brakes can be released so as to ensure a differential of pressure on the triple valve pistons sufficient to effect their return when the pressure is restored. Release of the brakes is delayed until venting of the train-pipe has been completed and the pressure throughout the train-pipe has equalized so as to avoid shocks due to uneven braking at different parts of the train. The apparatus comprises a speed limit selector valve D adapted to assume high, low and medium speed positions under the control of magnet valves A, B energized by track circuits. According to the position of the valve D, one or other of the pilot valves 17, 18, 19 is operative when opened by the centrifugal governor 7 to actuate the brake application valve E which then connects the reservoirs Q<1>, Q<2> of equalizing discharge valve mechanism K, L to reduction reservoirs R<1>, R<2> thereby venting the train-pipe 37 to apply the brakes. Fig. 1 shows the apparatus in " danger " conditions in which the magnets A, B are both deenergized to impose the low speed limit the speed being below such limit however so that the valve D is in the normal or high speed position. The valve chambers 50, 52, 44 and 46 of the valves D, E, F and G are constantly under pressure from the main reservoir 41 through passages 43, 49 and 45. In " clear " conditions both magnets A, B are energized thereby closing the exhaust valves 27, 29 and opening the valves 28, 30 to supply reservoir air from the passage 71 to the passages 75 and 73. The passage 73 supplies air to the piston chamber 72 of the valve G which is thereby depressed. The air supplied to the passage 75 flows by cavity 76 of the valve F and passages 77 to piston chamber 74 of valve D and by cavity 76 passage 79, cavity 80 in valve G and passage 81 to the piston chamber 78 of the valce D. The pressure in all chambers of the valve D thus being equal this value assumes the central position shown under the action of spring stops 82, 83 in which the low and medium speed ports 130, 126 are blanked. In these conditions if the high speed limit is exceeded, the pilot valve 19 is opened by the plate 10 on the stem 9 of the governor 7 and vents the piston chamber 85 of the application valve E through the passage 84 so that the brakes are applied as described below. If a caution signal is passed only the magnet B is energized. The valve 30 of this magnet admits pressure air to the piston chamber 72 of the valve G which thus assumes the lower position as in high speed conditions. Normally in passing a caution signal the driver depresses the penalty valve N thereby venting the piston-chamber 48 of the valve F through passage 112, cavity 113 in valve E and passages 114, 115. The valve F therefore assumes the upper position shown in Fig. 2. The venting of the chamber 48 is continued to maintain the valve F in this position after the penalty valve N is released, through the cavity 76 of the valve F, passage 75 and the magnet valve A. The chamber 74 of the selector valve D is thus connected to a delaying valve H actuated by a piston 25 and subject on its upper side to the pressure in a timing reservoir T<1> through passage 120 cavity 121 of valve G, passage 122, cavity 123 of valve F and passage 62 and on its lower side to feed valve pressure through passage 128 and pipe 127. The timing reservoir T<1> and upper chamber of valve II are also connected by the cavity 123 of valve F and passage 124 to the pilot valve 20 which is conical so that it opens an escape orifice dependent upon the extent to which it is depressed by the governor 7 and thus upon the speed of the train. The reservoir T<1> is originally charged to main reservoir pressuro through the passages 62, 61 and chamber 46 of valve F (Fig. 1) and when the pressure therein has escaped sufficiently through the valve 20 the piston 25 moves up (Fig. 2) and connects the passage 119 leading from the chamber 74 of the selector valve D to the passage 120 and thus to the reservoir T<1> and the atmosphere. The. pressure in chamber 78 of the valve D is maintained since the passage 79 to which it is connected is blanked by the valve F and the valve D therefore moves up to the medium speed position in which the passage 84 from the application valve E is connected by cavity 125 of valve D to the passage 126 leading to the governor actuated pilot valve 18. The delaying valve device H, 20 enables the speed of the train to be maintained until the point is reached at which the reduced speed is necessary. If the driver fails to depress the penalty valve N after passing a caution signal, the chamber 78 of the valve D is vented through passage 81, cavity 80 of valve G, passage 79,. cavity 76 of valve F passage 75 and magnet valve A. The chamber 74 is also vented through passage 72, cavity 76 and valve A and the pressure acting between the differential pistons of the valve D moves it to the lower position in which the passage 84 from the application valve E is connected by cavity 129 of this valve D to the passage 130 leading to the low speed pilot valve 17. The low speed limit is thus immediately imposed. If the penalty valve N is depressed after the caution signal has been passed there is no action since the valve E being in application position cuts oft the valve N from the valve F. If a danger signal is pressed both magnets A, B are deenergized (Fig. 1). In these conditions the valve G assumes the upper position since the chamber 72 thereof is vented through passage 73 and the magnet valve B. The governor actuated valve 16 and a timing reservoir T<2> are connected to the upper chamber of the delaying valve H by cavity 131 of valve G and the chamber 78 of the selector valve D is connected to the valve H by cavity 133 of valve G and passage 119 so that after an interval dependent upon the speed of the train as described above for the imposition of the medium speed limit the chamber 78 is vented through the valve 16 and as the chamber 74 is also vented by the valve A the valve D is moved to the lower position to connect the passage 84 from the application valve E to the passage 130 leading to the governor actuated valve 17 thus imposing the lower speed limit. The operation of the brake application and release valve E is as follows :-The chamber 50 of this valve is constantly under pressure from the main reservoir 41 by passages 43, 49 and this pressure normally equalizes into the piston chamber 85 through a port 96 in the piston. The chamber beneath the lower piston 5 is normally vented through passage 100 and the port 102 of the release timing valve M. The valve E therefore assumes the release position shown in Fig. 1 in which the train-pipe 37 is charged by the main reservoir 41 by the valve chamber 50, port 103, passage 104, pipe 105 and the driver's valve 35. The reservoirs Q<1>, Q<2> connected to the upper chambers ot the equalizing discharge valve 19, L are charged from the train-pipe 37 by passage 54, check valve 55, passage 56, cavity 57 of valve E and respectively by passages 58 and 60. The reduction reservoirs R', R<2> are respectively connected to the exhaust ports 67, 68 of the valve E by cavities 66, 70. When the piston chamber 85 is vented through the passage 84 by the opening of one or other of the valves 17, 18, 19 by the governor 7 the valve E moves to its uppermost position, Fig. 6, thereby connecting the equalizing reservoirs Q<1>, Q<2> respectively to the reduction reservoir R<1>, R<2> by valve cavities 66 and 70, thus raising the pistons and valves 86, 87 of the discharge valves K, L and venting the train-pipe 37 through passage 137, cavity 138 of the valve E passage 139 into the timing reservoir 88 provided with the atmospheric port 99. When the valve E is in application position, the chamber 85 thereof is connected to a normally open manual valve O by passage 92 and cavity 93. The pressure in the reservoir 88 closes the valve M and permits the pressure in the chamber 50 of valve E to equalize through the passage 101 into the chamber of the piston 5. If by the closure of the governor valves 17, 18, 19 and the manual valve O the venting of the chamber 85 of the valve E is stopped this valve is moved only to lap position by the spring stop 97 in which while it stops the venting of the equalizing reservoir Q<1> into the reservoir R<1> and closes the discharge valve K the reservoir Q<2> is still connected to the reservoir R<2>. After the discharge valve L has closed and the pressure in the timing reservoir has leaked away the valve M opens to vent the chamber of the piston 5 of the valve E and this valve then returns to the release position. Thus if an application of the brakes is initiated a reduction in train-pipe pressure corresponding to the equalization of the pressures in the reservoirs Q<2>, R<2> is ensured and the recharging of the train-pipe is delayed for an interval after the venting of the train-pipe has ceased. The manual release valve O may be dispensed with. To effect quick equalization of the pressure in the train-pipe 37 and the reservoir Q<1> if this reservoir is cut off from the