Patent GB-558496-A (GB)
Title: An improved system and apparatus for signalling on traction systems
IPC: B61L3/06
Filed: 1942-07-14
Abstract: 558,496. Electric selective signalling. ELECTRICAL COMPONENTS, Ltd., and SOMMER, W. July 14, 1942, Nos. 9776/42, 4419/43 and 8516/43. [Class 40 (i)] [Also in Group XL] Photo-electric railway and like signalling systems using one or more photo-electric cells are arranged to distinguish between single light impulses on individual cells and successions of impulses on one cell or a combination of impulses on different cells. The light impulses may be produced from lamps on the track or from lamps on the vehicle in conjunction with mirrors on the track reflecting the light back to the cells on the vehicle. The lamps on the track or the mirrors on the track are controlled by usual signalling mechanism. The light may be pulsated by a shutter or by arranging the mirrors in the form of grids. The cell circuit is made irresponsive to slow changes of light and responsive to impulses by a condenser coupling or responsive to pulsations by a transformer coupling. In one circuit arrangement, Fig. 1, for distinguishing between a single light impulse and two such impulses in quick succession on the same cell, a photo-electric cell 70 is coupled by a condenser 71 to the grid of a gas triode 72. When a single light impulse is received, the triode 72 is triggered, and current flows from terminals 97 through triode 72, relay 78, relay coil 76, bimetallic switch 74, and contacts 92. Relay 77 attracts its armature 79, closing contacts 80, so that current flows from terminals 91 through push-button switch 75, holding-in coil 96, circuit 94, and red lamp 73. The lamp indicates "danger" and the circuit 94 may be used to apply brakes. After a given time the bimetallic switch 74 breaks the primary circuit and the several parts return to normal. The secondary circuit may also be broken by the push-button switch 75. The relay 77 is slow acting; but the relay 78 is quick acting and its effect is to close contacts 16 in the circuit of a second gas triode 82, which, however, remains inoperative when a single light impulse is received by the cell 70. If two light impulses affect the cell 70 in quick succession before the relay 77 has time to operate, the first impulse causes the closing of contacts 16 and the second impulse triggers the triode 82 causing a current to flow from terminals 97 through triode 82, relay 99, push-button switch 95, green lamp 93, and bimetallic switch 14. Relay 99 opens contacts 92, preventing operation of relay 77; and green lamp 93 indicates signals set at "clear". After a given time the circuit is broken bv the bimetallic switch 14; or at any time by the pushbutton 95. The successive impulses may be obtained by two mirrors spaced apart along the track to reflect light from the same lamp to the same cell on the vehicle. In another arrangement, Fig. 6, for distinguishing between single, multiple and combination light impulses, two cells 20, 30 are respectively coupled to two gas triodes 22, 32. If a single impulse is received by the cell 20, the triode 22 is triggered and a green lamp 23, lights in series with bimetallic switch 24, and coils 116 and 56. Coil 116 swings armature 100 over contacts .101, without effect since coil 56 by itself is unable,to move armature 58. Green lamp 23 remains operative until the circuit is broken by bimetallic switch 24 or push-button switch 25. If a single impulse is received by the cell 30, triode 32 is triggered and current flows through coil 36, bimetallic switch 34, and coils 26 and 106. Armature 100 is now attracted to contacts 103, agains without effect since coil 26 by itself is unable to move armature 58. Relay 37, however, is operated by coil 36 and locks up in series with red lamp 33, push-button switch 35, and the circuit 42 which applies brakes until the circuit is broken by push-button switch 35. If both cells 20, 30 are simultaneously affected, both triodes 22, 32 are triggered and both coils 56, 26 energized at the same time. The relay 57 now attracts its armature 58, but coils 116, 106 being also simultaneously energized armature 100 remains in central position over contacts 102. The attracted armature 58 breaks the circuits of lamps 23, 33 and energizes holding coil 60 in series with pushbutton switch 55, bimetallic switch 109, and yellow lamp 53 and circuit 52 which serves to reduce speed or prevent speed exceeding a given maximum. If the cells are affected in quick succession instead of simultaneously, the armature 58 is attracted when both coils 56, 26 become energized, but one of the coils 116, 106 operates before the other and moves the armature 100 to one side or the other, and the subsequent energization of the other one of the coils 116, 106 is ineffective against the now more powerful attraction of the first energized coil. By this action, current is made to flow from terminals 41 through lamp 104 and circuit 108 if cell 20 is the first affected, or through lamp 105 and circuit 107 if cell 30 is the first affected; these currents persist until the circuit is broken by the push-button switch 55 or the bimetallic switch 109. The lamp 104 may be used to indicate "slow down men working on track ahead," and the lamp 105 to indicate "obstruction ahead, proceed with caution." The light impulses for this apparatus may be controlled by two pairs of mirrors on the track. The mirrors 3, 4, Fig. 3, of each pair are slightly inclined to each other to reflect the light from a lamp 2 on the vehicle to cells 20, 30 respectively, one above the other on the vehicle. The mirrors are carried by posts 6 and a hinged shutter is provided for each mirror and controlled simultaneously with the usual visible signals 7. The pairs of mirrors are spaced apart as shown at A, B, Fig. 7. In another modification, the selector device 100 of Fig. 6 is omitted together with the lamps 104, 105 and circuits 108, 107 and the contact 61 controls only the lamp 53 and circuit 52 which are permanently connected to one of the terminals 41. No contacts 102 are then required. With this arrangement, only the first three functions of the arrangement of Fig. 6 can be performed, and only one pair of mirrors is required.