Patent GB-249504-A (GB)
Title: Improvements in fluid pressure brake applying apparatus
IPC: B60T13/66
Filed: 1926-03-09
Abstract: 249,504. General Railway Signal Co., (Assignees of Bushnell, C. S.). March 20, 1925, [Convention date]. Fluid-pressure; indicators, applications of.- An automatic train-control system comprising a drivers rotary brake valve of the Westinghouse type adapted to be automatically operated, is provided with a supplemental valve connected to the rotary valve and adapted to connect a reduction reservoir to atmosphere in the running position of the brake valve and to the equalizing reservoir in the service position of the brake valve. The rotary part of the driver's valve is connected to the operating handle by a disengageable connection which is automatically disengaged when the valve is automatically operated. The usual rotary part 2, Fig. 2. of the valve has a squared portion 3a engaging a squared opening in the stem 20 of the supplemental exhaust valve 22. Rotatablv mounted about the valve stem 20 is a handle plate 7 integral with the valve handle 7a, 53. Also rotatably mounted about this stem is an actuator pinion 33 engaging a rack 16 connecting two pistons 13, 14 in cylinders 10. 11 of the automatic brake-valve actuator. The valve stem 20 carries a latch 36 which, on operation of the automatic brake-valve actuator, is disengaged, by a pin 44 on the pinion 33 from a circular cam 47 projecting from the handle plate 7. Immediately thereafter, a lug 43 on the actuator pinion engages a lug on the supplemental valve stem, which is turned with the two valves connected thereto. During this movement, although the handle 7a is disconnected from the valves, the valves may be moved by the engagement of a lug on the handle plate with a lug on the values stem. The braking system shown in Fig. 10 comprises an equalizing reservoir 80 and a reduction reservoir R controlled by an electropneumatic valve EPV normally energized by a current the circuit of which is broken on an automatic brake application. This valve normally admits pressure from the main reservoir through pipes 83, 69 to the cylinder 11 of the brake-valve actuator, which is exhausted through a port 85 when the valve EPV is de-energized. Under normal conditions, the brake pipe is connected through ports in the usual engineer's valve to the main reservoir and the equalizing reservoir. The supplemental exhaust valve 22, Fig. 2, blanks the equalizing reservoir and connects the reduction reservoir to atmosphere. If the handle of the engineer's valve is moved to the service position, the reduction reservoir exhaust-port is cut off and this reservoir is connected to the equalizing reservoir through the supplemental exhaust valve and a restricted passage. This causes the brake, pipe to be vented through the usual equalizing discharge piston 89. To make a further reduction, the valve handle is moved to the lap position, thereby exhausting the reduction reservoir to atmosphere, and when the handle is returned to service position air will again flow from the equalizing reservoir to the reduction reservoir to produce a lower equalizing pressure. On automatic operation of the braking system and exhaustion of main reservoir pressure from behind the piston of the cylinder 11, the smaller piston of the cylinder 10 is subjected to mainreservoir pressure to move the pistons until a stop 18, Fig. 3, is reached when the two valves are in the service position. If the circuit of the valve EPV is again closed, the brake-valve actuator returns to normal position but the valves must be returned by hand. The system shown in Fig. 12 is modified by the provision of two reduction reservoirs R<1>, R<2> normally isolated by the lower valve-member 90 of an electricallyoperated valve EV. The upper valve member 91 vents the reservoir R<2> to the atmosphere. The valve EV is normally energized. Also a circuit closer DPC and slow acting relays 93, 94 are provided. On automatic operation of this system, the valve EPV and relay 93 are de-energized, the rotary valve and supplemental exhaust valve are operated, and the pressure, in the equalizing reservoir is reduced until it is equal to the pressure in the reduction reservoir R<1>. This causes the circuit closer DPC to close a contact 103 as the pressure in a chamber 95 connected to the brake pipe is higher than the equalizing reservoir pressure in a chamber 96, and a. circuit is closed through the relay 94. When the brake-pipe pressure has almost fallen to equalizing-reservoir pressure through the usual equalizing piston valve, contacts 103 re-open and the relay 94 is de-energized and de-energizes through a contact 112 the valve EV, which connects the reservoirs R', R<2> together, causing the equalizing-reservoir pressure to be again lowered and a second stage of reduction in brake-pipe pressure takes place. The consequent reclosing of contacts 103 has no effect on the apparatus as they are connected in a stick circuit for the relay 94 and therefore are not able to pick up this relay. To cause the second stage of the brake application to overlap with the first, the engineer's valve handle is moved to the lap or second position thereby dropping the relay 94 by opening contacts 51, 53, Fig. 3 mounted on the engineer's valve. These contacts are also opened on manual operation of the system, thus connecting reservoirs R<1>, R<2> from the beginning of the manual operation so that they function as the single reservoir R, Fig. 10. A single pressure-circuit controller 95b, Fig. 14, may be substituted for the circuit closer DPC, the pressure chamber of which is connected to the series exhaust port from the engineer's valve, that is the port through which flows the exhaust from the equalizing discharge piston 89. The contacts of this circuit controller are closed as long as air is escaping from the engineer's valve. In the modification shown in Fig. 14, apparatus is provided which has to be operated from the ground necessitating stopping of the train, in order that the train may continue, if an automatic application of the brakes has not been anticipated by a manual operation. An automatic application is brought, about by the opening of a contact 82 controlling the valve EPV. A contact 82a is also opened which breaks the stickcircuit for a relay PR allowing the contact 165 in the circuit of the valve EPV to open, and it remains open till the train is brought to a stop and the engineer presses a button PB from the ground. On manual application of the apparatus, the stick circuit is completed through the relay PR by contacts 170 operated by the engineer's valve handle in the service or emergency position. The stick circuit is closed through a circuit including the contacts 120<b> of the circuit controller 95<b>. Thus the relay remains energized as long as the engineer's valve is in a braise-applying position or as long as brake-pipe pressure is discharging from the service exhaust. After the engineer's valve handle is moved to service position. it is returned to loop position and, owing to a modified construction of supplemental exhaust valve the reduction reservoirs are not discharged in this position. With this reduction in equalizing reservoir pressure, the equalizing discharge piston begins to function and brake-pipe pressure is discharged through the chamber 95<b> closing the contacts 120<b>. With the engineer's valve left in service position, a full application takes place as contacts 53 are opened by the engineer's valve and the reduction reservoirs R<1>, R<2> equalize in pressure with the equalizing reservoir pressure. When the apparatus has been automatically operated and the valve EPV de-energized, the equalizing reservoir 80 is connected to the first reduction reservoir R<1>. The automatic movement of the engineer's valve to the service position causes venting of the excess-pressure headgovernor pipe 123 and venting through an adjustable valve 133 of the pressure in a reservoir 130, bringing about the opening of contacts 142 connected to a piston 141 operated on by the pressure in reservoir 130. These contacts are opened a predetermined time after the brake valve has been automatically operated, depending on the adjustment of the valve 133, which is adjusted according to the length of the train &c. The opening of the contacts 142 de-energizes the valve EV, which connects the reduction reservoirs R<1>, R<2>, effecting a further reduction in equalizing- reservoir pressure. A cock 152 controlling the connection between the large cylinder 11 of the automatic valve actuator, the valve EPV, and the main reservoir and also the connection between the engineer's valve and the brake pipe, which cock may be locked in position, is provided for use while double heading.