Patent GB-149922-A (GB)
Title: Improvements in and relating to train brake systems
IPC: B61L3/12
Filed: 1920-08-06
Abstract: 149,922. Sprague Safety Control & Signal Corporation, (Assignces of Sprague, F. J.). Aug. 7, 1919, [Convention date]. Fluid pressure. - Improvements are made in the semiautomatic braking system for trains and the means for controlling the same from track apparatus described in Specifications 18213/15 and 101,348, and 104,176, [both in Class 38 (v), Electric switches &c.]. The utilization of an impulse received by train apparatus from appliances on the track is made dependent upon the retardation due to a brake application or upon the fluid pressure by which the brakes are applied or upon either of these features in conjunction with the speed of the train. In the last case, switches dependent upon both the speed and the retardation of the train may be used. Other improvements include the following features :-a wide range of permissible speeds at an active home track magnet is provided for; the brakes are applied at an active home track magnet independently of the time occupied in passing from the distant to the home magnet; resetting devices are provided on the track; compound permanent and electro-magnets for neutralizing their effect on train apparatus are fitted on the track and co-act with magnetic receivers on the train to open the relay circuit by which the brake application is initiated. The brake system shown in Fig. 1 includes valves similar in function to those described in Specification 18213/15 but differing in construction. The control valves 8, 20 for the service application and the emergency application respectively are mounted in one casing and are controlled by the cores of electro-magnets 33, 34 also mounted on one frame 30. Both valves are held closed when the magnets are energized. When the magnet 33 is de-energized, the vent valve 36 opens and valve 8 is lifted by the pressure on its lower side and pressure fluid passes from main reservoir M to the cylinders which move the driver's valve or, as shown, to the chamber 4. which carries a whistle 7 and contains oil which is forced into cylinders 2 which move the driver's valve by means of the yoke 3 to lap position. The pilot valve 6 is then opened and the space above the diaphragm 13, which is normally connected to the equalizing-reservoir E through the automatic service brake valve 15, is exhausted, and the supply valve 10 is closed by the brake-pipe pressure below the diaphragm 13, thereby enclosing air at train pipe pressure in the chamber 11 and above the diaphragm 17. Pressure then falls in the equalizing reservoir and on the upper side of the piston of the equalizing cylinder until the difference of pressure above and below the diaphragm 17 overcomes the spring 16, the valve 15 is thereby closed and further escape of air from the equalizing reservoir is stopped. When the emergency control magnet 34 is de-energied, air pressure in the chamber 22b, which is supplied from the brake pipe BP through the tubular valve-stem 22 and a leakage port in the piston 22a, lifts the valve 20. Piston 22a then falls and opens valves 21, 23, the former of which is the emergency brake valve. The valve 20 also vents the chamber above the diaphragm 26 and allows the valve 25 to open communication from the main reservoir M to the application cylinder pipe AC. The valve 20 recloses at once, but the chamber 22b is vented through the port 23. The track equipment in each section preferably comprises two permanent magnets 50, 51 with de-magnetizing coils controlled by track relays, so that the magnets are inoperative on passing train-carried apparatus when the coils are energized owing to the track being clear, and a resetting magnet 52, preferably an electro-magnet, which is active when the track is clear. The resetting magnet may be a permanent magnet or it may be a compound magnet. The distant application magnet 50 is placed just outside the entrance to a section and is dependent upon the distant relay D connected to the advance section. The home application magnet 51 is placed at such distance in the rear of the distant application magnet as will permit a train to be stopped before reaching the latter. The magnet 51 is controlled by the home relay H of the advance section. The receiving apparatus on the train comprises magnetic plates with polepieces which, when the plates are carried past a track magnet in active condition, move an armature to open a contact 57, 58. The opening of the contact 57 in the application receiver initiates the application by way of contact 69. Lamps 65<b>, 65<c> in parallel with the coil 34 are arranged in circuit with brushes in contact with the cylinder 67 so placed that the circuit of the lamps is broken at a speed slightly of the brakes and the opening of contact 58 in the resetting receiver effects the resetting of the train apparatus. Fig. 40 illustrates the principle by which the circuit of the brake controlling magnet 34 is controlled according to the speed of the train and the degree of application of the brakes. The cir. cuit between the coil 34 and the negative side of battery 43 may be completed over either of the contacts 62 or 63 independently of speed or brake conditions or by way of contact 71 closed when pressure in the application cylinder pipe AC exceeds that in the distributing valve release pipe DVR (a condition which exists only, when the whole train is braked) and contact 72, which is movable by the piston 48 subjected to the pressure in the engine brake cylinder and moved to the left of the drawing as that pressure increases so as to maintain contact with the cylinder 67 movable axially by the governor 66 over a greater range of speed. This branch circuit is completed below that at which the circuit to the magnet 34 is opened and serve as a warning of the pending automatic braking. The control of the circuit by the air-pressure in the brake-cylinders may be replaced by control by a switch which takes up a position according to the retardation or acceleration of the train, as hereinafter described. Switches which make or break circuits according to the speed of a driven member and the retardation of the train may replace the governor-controlled and the brake-controlled contacts. The circuits of the brake controlling magnets 33. 34 and of the lamps 65<a>, 65<b>, 65<c> are controlled by service relay 78 an emergency relav 79 and a reset relay 80, all of which are fitted with maintaining contacts. Relays 78, 79 are de-energized by the opening of contact 57 in the receiver apparatus and relay 80 by contact 58; normally the two former are energized and the latter de-energized as indicated in Fig. 1. The circuits of the brake-controlling magnets 33, 34 also include contacts 77, 81 controlled by a Bourdon tube 45 so as to be open when pressure exists in the brake pipe. The circuit of each of the three relays are mutually dependent upon contacts of the other relays. If, when running under normal conditions, an energized distant track magnet is passed the contact 57 is opened and magnets 78, 79 are de-energized. The circuit of magnet 34 is opened at contact 62 but remains closed at contact 63 and this magnet is not therefore de-energized. The circuit of magnet 33 is opened at contact 75 and this magnet initiates a service application of the brakes. After the track magnet is passed, the contact 57 re-closes and relay 79 is energized by way oi arm 83 and closes contact 85 which energizes reset relay 80. The opening of the valve 6, either automatically or by the driver's operation of the brake valve, exhausts the pressure in the Bourdon tube 45 which closes contacts 77, 81 and completes the circuit to the relay 78, which picks up its armatures and reenergizes the valve magnet 33. The braking also causes the closure of contact 71 by the Bourdon tube. If the speed is properly controlled and the reset magnet on the track is energized when passed, the contact 58 is momentarily opened and then closes. The reset relay 80 drops its armatures and closes the circuit to the green lamp 65<a> and a branch of the circuit to the coil 34. The relays are thus set to normal condition. If, however, the train passes another active track magnet, the second momentary opening of the contact 57 causes the relays 78, 79 to drop their armatures and since contacts 81, 83 are open the relays remain de-energized and an emergency application results. Detailed description of the operation of the train-carried apparatus under different conditions dependent upon the action of the track apparatus and the proper or improper operation of the brake valves by the driver and upon the speed of the train is given in the Specification.