Patent GB-805349-A (GB)
Title: Improvements in or relating to display indicators
IPC: G09F11/28
Filed: 1957-04-17
Abstract: 805,349. Indicators. GENERAL RAILWAY SIGNAL CO. April 17, 1957 [April 23, 1956], No. 12549/57. Class 40 (1). An indicator for exhibiting one of a number of symbols carried on a belt comprises a motor controlled by main and auxiliary circuits, the main circuit serving to position the belt approximately and the auxiliary circuit serving to switch-off the motor when the belt is accurately positioned. The indicator housing has a metal side wall 11, an opposite wall 12 of insulation, insulated end walls 13, 14 and a metal U-section cover 15, Fig. 6. To side wall 11 are mounted the driving motor M, a relay SR and a gear train driving the belt 19 and contact discs 16, 17 and 18. The motor armature 24 is mounted on a pin 27 and carries pinion 28. This drives gear 37 carrying the belt pulley 38 and contact disc 16 through a gear train having an 8 to 1 reduction. Pinion 40 on gear 37 drives gear 42 carrying the second contact disc 17 through a gear train having a 2 to 1 reduction. Gear 42 meshes with an equal gear 43 carrying the driving pin of a Geneva gear which rotates contact disc 18 in steps with a 4 to 1 reduction. Relay SR controls the entry of a latching head 60 into one of four equally spaced openings in gear 35, the latch being spring-urged towards the engaging position where it locks the gear train. The control circuit energizes motor M and relay SR at the same time. Relay SR displaces its armature 59, Fig. 6, to withdraw the latch and closes a spring contact 66. The motor then drives the gear train through friction clutch 30 until the point is reached where there is no circuit through the selector circuits. When the relay is de-energized the latch is released to bear against the gear 35 and drops into the next opening that comes into line with it, to stop the gear train. The motor continues to be driven through contact 66 (the auxiliary circuit) and this does not open until the latch is fully engaged. The motor therefore overruns the locked position being allowed to do so by slip in the clutch 30. The belt 19 is driven by eight pins on the pulley 38 engaging in track holes 72. At the other end it passes over spaced rollers on axles 104, 105 which present the selected symbol to a window 75 in the endpiece 13 where it is illuminated by a lamp 112. The belt has a twist in one side so that symbols on both sides are exposed in turn as the belt makes two complete revolutions. There are 64 such symbols so that pulley 38 has to revolve eight times and the motor revolves 64 times. Selector circuits.-The contact discs 16, 17 and 18 rotate with gears 37, 42 and Geneva gear 45 and are spring loaded to bear against commutator-type printed circuits on wall 12. The contact discs have connector strips, e.g. 82, 83 fastened on by rivets 84, the rivets bearing against the circuits to make connections between certain lines thereof. The outside of the wall 12 has printed circuits for carrying the coded input signals to the various parts of the commutator circuits from the six input terminals which are on the back of the wall 12 opposite the six terminals 131-138. The latter are used mainly for supply purposes. Connections to the code leads are taken through the thickness of the wall. For each revolution of the belt, contact disc 16 makes eight revolutions, disc 17 makes four revolutions and disc 18 makes one revolution. Each commutatortype printed circuit comprises two distinct commutators: C1-C2, C3-C4 and C5-C6; these being shown separately in Fig. 17. Thus group C1-C2 consists of a commutator C1 which has an outer ring with eight segments, connected together alternately, over which passes a contact on strip 82 and a continuous inner ring making contact with the other end of strip 82. The part C2 is divided into four segments connected together in alternate pairs and co-operating with contact strip 83. In both cases one group of segments is connected to apply the input voltate on lines 139, 141 to to the motor M and through rectifier R to the relay SR. The other commutator circuits are represented by commutators C3, C4, C5 and C6 in Fig. 17, in each case the input voltage on lines 140, 142, 138, 143 being applied to the motor and relay line 159 in alternate positions. A combination of the input lines is energized by relay contacts selectively energized according to a code. The motor remains energized to feed the belt forward while it receives energy from any of the input lines through commutators C1-C6 but when all the commutator groups correspond to the setting of the code relays CR1-CR6 the main current path to relay SR and the motor will be broken. But the auxiliary circuit through the relay contact 66 will remain closed until the gear 35 moves to bring one of its openings into line with the latch 60. When this occurs the latch moves into latching position and opens contact 66 to cut the motor off as described above. The indicator can, with minor modifications be converted to a thirty-two point code or a sixteen point code capacity. A number of indicators may be mounted together in a bank.