Patent GB-477319-A (GB)
Title: Improvements in or relating to train control systems
IPC: B61L3/12
Filed: 1937-01-14
Abstract: 477,319. Track - apparatus for train control. HUDD, A. E. Jan. 14, 1937, No. 3893/36. [Class 105] The invention relates to train-control apparatus of the kind in which at each signal location a first track magnet moves by magnetic action an armature of a magnetic receiver on the train to give a warning signal or braking action, which is cancelled if the receiver is re-set by a second track magnet, this latter being operative only if the signal is at clear, and wherein means are provided by which the driver can re-set the receiver. The invention consists in that the armature is permanently polarized and is so initially set that only a single movement occurs on passing a track magnet and that the operative poles of the track magnets and the permanently polarized armature or a collecting plate therefor overlap and that at least one of them lies on the centre line of the track. The receiver is housed in a non-magnetic steel casing. Visual indicator means show the last operation of the apparatus whether a warning signal, a clear signal, or a re-setting by the driver. At a distant signal at clear the track magnets are arranged to operate and shortly afterwards restore the receiver armature. At a home signal at danger two spaced warning actions are given. The magnetic receiver is shown with a permanent magnet armature 10 which engages polepieces 15, 13 attached to upper and lower collecting plates 16, 14, the upper plate 16 being substantially longer and forming the top closure of the non-magnetic steel housing 35 in which the receiver parts are enclosed. The armature 10 carries on an arm 11 a valve 12 which opens the pipe 34 when a track permanent magnet 17 is passed. The movement of the permanent-magnet armature 10 (poled N, S as indicated) to the warning position occurs when the lower collecting plate 14 is over the N pole of the track magnet 17, and the long upper plate 16 is still extending over the S pole of the track magnet. The apparatus shown is for a vacuum braking system and accordingly the opening of the valve 12 admits atmospheric pressure to the underside of a diaphragm 43 whereby a slide valve 55 is raised to connect a vacuum reservoir 29 to a horn 53, and to open a pipe 54 to a chamber 48 having a throttle 6 to the atmosphere. A delay chamber 62 retards the building up of atmospheric pressure entering through this pipe 54 and thus only after an interval is a diaphragm 61 raised to open the main valve 65 for venting the train pipe 67. If the driver is alert he operates a push 27, whereby the vacuum of reservoir 29 is applied through a pipe 23 to a chamber 20 so causing a diaphragm 18 to move to the left ; a slotted stem 30 on the diaphragm has a lost-motion connection 31 with the arm 11 and thus resets the permanent-magnet armature 10 and re-closes the valve 12. A nullifying valve 32 is opened so long as the stem 30 is held over. A visual indicator 57 is operated by the stem 45 of the slide valve 55. Figs. 7, 8 show the interior mechanism. When the stem 45 rose, the pointer 100 was moved anticlockwise to the warning position by the fork 109 engaging a lug 106 on the spindle end-member 104. The operation of the re-set push 27 also applied vacuum by a branch pipe 124 to the left hand side of a diaphragm 120, Fig. 7, whereby a nose piece 119 was withdrawn laterally from a detent 114. Since the re-set action caused the slide valve 55 to descend the pointer tends to return clockwise under the action of a spring 111, but the spindle end-member 104 engages by its flange 105 in the fork of the detent 114 and thus the pointer only moves to the " cancelled '' position. The flange 105 exerts a cam action on the limb 117 of the fork of the detent to raise the detent sufficiently for the sloping part 125 of the nose piece 119 to enter below the detent. At the next operation of the apparatus the detent will therefore rise to its top position as soon as the spindle end member 104 has moved anticlockwise. If the wayside signal is at clear the receiver is operated and immediately restored by a second track magnet and thus the stem of the slide valve is raised and immediately lowered and therefore the pointer returns clockwise without being stopped by the detent. The detent is only lowered if a driver's re-set action occurs. At a signal location with combined home and distant signals, Fig. 3, the track magnets comprise a pair of adjacent magnets 93, 94 at the signal and at a position 200 yards before the signal a pair of magnets 90, 91 spaced 10 yards. If the distant signal is at clear the action at the advance magnets 90, 91 is that the receiver is operated and shortly afterwards restored ; the rise and fall of the slide valve 55 causes a brief operation of the horn. With the home signal at clear the track magnets 93, 94 give a practically simultaneous operation and restoration and thus no action arises in the controlled apparatus. With the distant and home signals at danger the permanent magnet of each pair operates the receiver, and there is no restoration; the driver must therefore re-set twice. The track electromagnets are energized over a cabin lever contact 96 and signal detector contacts 97, 98 so that the wayside signals must have responded to the lever movement if the track magnets are to give a clear signal. The track magnets may be arranged vertically or transversely so that the receiver passes only over one pole. The atmospheric air entering the receiver casing passes through a drying filter 39 filled with silica gel. Electric arrangements may be provided for transmitting the control from the receiver and for its re-setting and for giving lamp indications of the operations, Fig. 4 (not shown). The permanently polarized armature of the receiver may consist of a movable soft-iron armature which is polarized by a fixed permanent magnet forming a wall of the receiver casing, Fig. 15 (not shown).