Patent GB-817845-A (GB)
Title: Improvements relating to compressed fluid braking apparatus
IPC: B60T15/30
Filed: 1957-02-27
Abstract: 817,845. Fluid-pressure brakes. WESTING HOUSE AIR BRAKE CO. Feb. 27, 1957 [Feb. 27, 1956], No. 6556/57. Class 103 (1). In a compressed fluid-braking apparatus of the kind wherein the supply of compressed fluid to and its release from a brake cylinder is controlled automatically in dependence on selected variations of the pressure of compressed fluid in a brake pipe relative to a reference pressure in a control reservoir, the rate of variation of brake pipe pressure to cause the release of compressed fluid from the brake cylinder is effective to provide direct release of compressed fluid from the brake cylinder or alternatively selective graduated release of compressed fluid from the brake cylinder corresponding to the extent of the imposed variation. When the system is charged, compressed fluid in brake pipe 4 flows into passage 12 to the auxiliary reservoir 2 by way of check valve device 7, passage 13, choke 14 and pipe 16. Fluid is also supplied to control reservoir 3 by way of passage 12, and control reservoir charging choke 28, passage 27, groove 23 in slide valve 18 of cut-off valve device 17, passage 25 and pipe 26. At the same time compressed fluid supplied to brake pipe 4 also flows by way of pipe and passage 109 to brake pipe pressure chamber 108 in selector valve device 6 as well as from passage 109 through choke 111 to chamber 110. The chamber 22 of the cut-off device 17 at this stage is connected to atmosphere through device 6 by way of port 100. At the same time as compressed fluid is being supplied to auxiliary reservoir 2 by way of passage 15, such fluid from passage 15 also flows to chamber 72 in service valve device 66 and to chamber 47 in the quick-service valve device 35; compressed fluid being supplied to control reservoir 3 by way of passage 25 also flows to control reservoir pressure chamber 88 of device 66. When the brakes are to be applied, manipulation of the driver's brake valve (not shown) reduces pressure of compressed fluid in the brake pipe 4; which reduction is effective in the brake pipe pressure chamber 46 in the quick service valve device 35 to cause the auxiliary reservoir pressure in chamber 47 to actuate the diaphragm 37 to move slide valve 36 to its quick service position in which it abuts end wall 50. Compressed fluid is then permitted to flow from brake pipe 4 to the quickservice volume chamber 42 and initially to atmosphere. At the same time compressed fluid withdrawn from the brake pipe by way of quick-service valve device 35 flows to control chamber 20 in cut-off valve device 17 and actuates slide valve 18 to its closed position where slide valve engages with end wall of chamber 33 and cuts-off communication of the control and auxiliary reservoir 3 and 2 with the brake pipe. The reduction in brake pipe pressure resultant from the filling of the quickservice volume chamber 42 acts on brake pipe pressure chamber 87 in service valve device 66 to cause higher control reservoir pressure in chamber 88 to act on diaphragm 71 and cause valve 67 to be lifted by valve-stem 68 acting against force of spring 92. Compressed fluid from auxiliary reservoir 2 then flows to brake cylinder 1 by way of pipe 16, auxiliary reservoir passage 15, the supply chamber 72 in service valve device 66, unseated supply valve 67, the passage 61, choke 98 and pipe 97. The supply of compressed fluid from auxiliary reservoir 2 to the brake cylinder 1 is terminated when brake cylinder pressure in pressure chamber 82 in service valve device 66 reaches a value corresponding to reduced brake pipe pressure in chamber 87 of service valve device to seat the supply and release valve 67 whilst leaving it engaged with seat element 69 to hold the desired pressure in the brake cylinder 1 hence any particular degree of brake cylinder pressure may be obtained by operation of the service valve device 66 according to the degree of reduction in brake pipe pressure relative to control reservoir or reference pressure, either continuously or in graduated steps. Graduated release of the brakes to any desired degree and in any number of steps may be effected by a partial restoration in brake pipe pressure at less than a certain quick release rate as determined by appropriate manipulation of the driver's brake valve. As brake pipe pressure is thus increased at less than such quick-release rate, compressed fluid from brake pipe flows to chamber 110 by way of pipe and passage 109 and the choke 111 at such a rate that brake pipe pressure in chamber 108 does not exceed that in chamber 110 acting on the diaphragm 103 sufficiently to overcome the opposition of the spring 105 so that the slide valve 93 remains in the position in which it is shown in the drawing. The chamber 22 in the cut-off valve device 17 therefore remains vented to the atmosphere through the passage and pipe 99, port 96, chamber 101, and the port 100 in the device 6, and the cut-off valve device 17 consequently remains in its closed position isolating the control reservoir 3 from the brake pipe. Rising brake pipe pressure in chamber 87 in service valve device 66 acts on diaphragm 71 to move stem 68 in direction of control reservoir pressure chamber 88 to permit release of compressed fluid from brake cylinder 1 and to atmosphere by way of pipe 97, choke 98, passage 61 and passage 78 in stem 68 to restricted exhaust passage 81 until the pressure in brake cylinder chamber 82 in service valve device 66 reduces to a value corresponding to the selected degree of restoration in brake pipe pressure in chamber 87, pressure in control reservoir pressure chamber 88 acting on diaphragm 71 to move the stem 68 and return seat element 69 into engagement with the supply and release valve 67 to hold the desired degree of brake cylinder pressure in the brake cylinder 1. Such reduction in brake cylinder pressure effected by operation of the service valve device 66 in response to partial restoration of brake pipe pressure may be repeated until full release of the brakes corresponding to complete restoration in brake pipe pressure to its normal value has been achieved whereupon the brake cylinder pressure will be reduced to that of the atmosphere and the service valve device 66 will remain in its release position in which it is shown in the drawing. To effect a direct release of the brakes, compressed fluid is supplied fairly rapidly to brake pipe 4 by means of driver's brake valve at a certain selected quick-release rate, such fluid flowing through the pipe 109 to selector valve device 6 in the first vehicle of the train, causing brake pipe pressure in chamber 108 to proponderate over the less rapidly increasing pressure of fluid in chamber 110 supplied through choke 111 sufficiently to operate the diaphragm 103 or actuation of the slide valve 93 to establish communication between pipes 99 and 97 by registration of the groove 102 with ports 95 and 96. Thereupon, compressed fluid from the brake cylinder 1 flows to the chamber 22 in the cut-off valve device 17 by way of pipes 97 and port 95 in selector valve device 6 and groove 102 in valve 93, the port 96, and the pipe and passage 97. Upon supply of compressed fluid from the brake cylinder 1 to the chamber 22 the cut-off valve device 17 moves to its open position shown in the drawing and permits compressed fluid from the control reservoir 3 to flow into the brake pipe 4 for equalization of air pressure.