Patent GB-426870-A (GB)
Title: Improvements in and relating to level crossing signalling arrangements
IPC: B61L29/28
Filed: 1933-09-30
Abstract: 426,870. Level - crossing signals. NAAMLOOZE VENNOOTSCHAP MACHINERIEEN-EN APPARATEN FABRIEKEN MEAF, (formerly NAAMLOOZE VENNOOTSCHAP MACHINERIEEN-EN APPARATEN FABRIEKEN), 30, Croeselaan, Utrecht, Holland. Sept. 30, 1933, Nos. 26975 and 26976. Convention dates, June 27 and July 13. [Class 105] For the control of a levelcrossing signal two short insulated track sections A, B and C, D are provided at each side of and some distance from the crossing while the crossing itself has at each side abutting short insulated track sections ; the two outermost sections A, C include a normally energized relay 1 which drops on entry of a train and a contact thereof disconnects the inner remote sections B, D from their associated normally de-energized relay 2 and connects them with the sections A, C, so that the relay 1 continues de-energized while the section B or D is being run through ; with a leaving train however the section B being entered first, the relay 2 is energized first and a contact thereof either opens a direct earth connection to prevent the relay 1 being dropped or prepares a stick circuit which is completed when the relay 1 drops shortly after and the relay 2 thus being energized prevents the signal being operated. The signal is cleared when the train leaves the section abutting the far side of the crossing. The rail length E at the actual crossing is connected with the abutting short, insulated rail lengths G, H only when the train has reached section G or H. In the normal state only a relay 1 is energized, the circuit being from battery B1 over the rail length A, a conductor leading to the rail length C, a return conductor to the relay 1, and back to the battery B1 ; the earth connection over a back contact 21b of the relay 2 at normal conditions has no operative effect. When a train enters at A or C such rail length is earthed through the train axles and the non- insulated rail F with the result that the relay 1 is shunted out. A back contact 11b of the relay 1 picks up a relay 3 which then sticks over its own front contact 32a and a back contact 42b of a relay 4 ; contact 31 of the relay 3 opens its back contact b to extinguish the clear signal W and closes its front contact a to light the danger lamp R. Contact 12 of the dropped relay 1 opens its front contact a to disconnect the relay 2 from rail length B and its back contact b links the lengths A, B so that the present conditions persist until the train leaves rail B whereupon the relay 1 is re-energized but the danger signal continues since relay 3 is stuck up. When the train reaches rail G the relay 2 is energized and its front contact 23a picks up a relay 4 over front contact 33a of the stuck up relay 3. The relay 4 sticks up over front contact 23a and its own front contact 42a while the back contact 42b breaks the stick circuit of the relay 3. The front contact 43a of the relay 4 links the rail E with the rails G, H so that the present conditions persist until the train has left these lengths G, E, H, whereupon the relay 2 drops, so breaking the stick circuit of relay 4, and now the clear signal W is lit since the relays 3, 4 now close their back contacts 31b, 41b. As the train leaves the stretch, the rail length D being reached first, the relay 2 is energized and its back contact 21b is opened to remove the direct earth connection of relay 1 so that the relay 1 will not drop when rail C is earthed through the axles. Front contact 22a of relay 2 links the rails C, D so that the present conditions persist until the train leaves rail C. It will be noted that the already existing clear signal is not affected since the relay 3 is not picked up on account of the relay 1 not having been dropped. The non-insulated rail F need only be electrically effective at the regions opposite the insulated short rail lengths and any disturbance of the rails can be caused to give a warning by the circuit of the normally energized relay 1 being arranged to include in its circuit such regions of the non-insulated rail but the action with a leaving train is that the relay 1 then necessarily drops and the signal control arrangement already described must be modified. Fig. 2 shows such a modification. A train entering section A drops the relay 1 a contact 12 of which disconnects the relay 2 and links the sections A, B so that these conditions are maintained while the train runs through section B. The danger signal R is energized over front contact 31a of a relay 3 which is picked up over back contact 11b of relay 1 and back contacts 42b, 21b of relays 4, 2 and which sticks over its own front contact 32a until the section G at the crossing is reached whereupon the relay 2 is energized and causes the energization of the relay 4 which breaks the stick circuit of the relay 3 at contact 42b but maintains the danger signal until the section H abutting the far side of the crossing has been left. The leaving train first enters the section D and so energizes the relay 2 a front contact 23a of which prepares a stick circuit for this relay 2 which is closed when the train by next entering the section C has caused the relay 1 to drop and close back contact 13b. Thus therelay 2 continues energized until the sections D, C are left and since the back contact 21b was opened before the back contact 11b closed it will be seen that the relays 3, 4 are not picked up and thus no danger signal is given by a leaving train.