Patent GB-362946-A (GB)
Title: Improvements relating to traffic controlling apparatus for railways and the like
IPC: B61L23/24
Filed: 1930-09-11
Abstract: 362,946. Tablet instruments for railway traffic control. KERSHAW, A. G. and WESTINGHOUSE BRAKE & SAXBY SIGNAL CO., Ltd., 82, York Road, King's Cross, London. Sept. 11, 1930, No. 27139. [Class 105.] A tablet instrument for controlling traffic on railways having a manually operated handle for permitting withdrawal of a tablet is provided with means for positively engaging and guiding the tablet throughout its whole passage through the instrument so that the tablet is maintained substantially horizontal independently of its engagement with the adjacent tablets above and below. The tablet instrument shown is similar to that described in Specification 203,241, [Class 105, Railway signals &c.]. Fig. 1 is a sectional elevation, Fig. 2 a sectional plan, Fig. 3 a sectional side elevation, and Fig. 5 a part top plan. A handle 1 when pulled out and turned actuates, by means of a cam displacing a yoke member 12, an apertured delivery plate 16 carrying a tablet which does not, however, drop into the shoot until the handle moves axially inward under spring action and by its pin 56 rocks a lever 54 which is linked to and therefore withdraws an arm 50 normally extending across the shoot opening. The handle is normally locked by one of two electromagnets 21, 22 engaging a rack 20 which is in mesh with a toothed sector 19 of the spindle of the handle. A link 23 connected to the sector 19 rocks a commutator 25 through a clutch 26 and a plunger 37 in the handle spindle actuates by means of a double-cranked shaft 34, 36 a link 31 which operates a fork member 29 adapted to force a tablet past a finger 28 on the commutator sleeve and therefore to reverse the commutator 25 which by reason of the clutch 26 can be moved independently of the actuation by the handle 1. To permit a train to travel from a station A to a station B the operator at A presses his plunger 37 and sends a line current over a commutator (not shown) to B, giving a signal and releasing the lock magnet 21 at B so that the handle at B can be turned clockwise. When this has been done, the operator at B can energize the magnet 22 at A to permit that handle to be turned and deliver a tablet in the manner described above. The two handles are now set in opposite directions and are locked so that they cannot be returned to their normal positions until a tablet is returned to one or other instrument. To insert a tablet a slide 40, Fig. 5, on the top of the casing is withdrawn and the tablet is inserted in its aperture 41, whereupon the slide can be returned as a pawl 45 which would otherwise engage the aperture to prevent this return movement is now held raised by the presence of the tablet. When the tablet reaches the casing aperture notches in its rim engage guide ribs 46 and the tablet drops, but remaining horizontal, until it reaches the projecting finger 28 past which it is forced by operating the fork 29 through the intermediary of the plunger 37; this action reverses the commutator 25 and the electrical connections now permit the instruments to be restored to normal. Fig. 8 shows the tablet with the guide notches 61 and one form of special central aperture 60 to distinguish the tablets of different sections.