Patent GB-191123345-A (GB)
Title: Improvements in or relating to Railway Signalling Apparatus.
Inventor: HURST ARTHUR
IPC: B61L23/12
Filed: 1911-10-23
Granted: 1912-05-09
Abstract: 23,345. Hurst, A. Oct. 23. Signalling - instruments ; miniature signals.- Permissive block instruments for indicating in cabins the condition of a section as regards occupation by trains are so connected that cooperation between the respective signalmen is necessary before any indication can be given. Indications are given in each cabin that the apparatus in the other cabin has operated correctly. Fig. 3 shows a back view of the apparatus in a cabin at the down end A of a section and Fig. 5 shows the dial plate d of this apparatus which exposes one indication at a time through an opening c in the front of the casing. The instrument at the ' up ' end B of the section differs only in the inscriptions on the dial plate. Both instruments show ' line closed ' normally with the section clear. To pass an up train from station A to station B, the operator at A turns the handle f clockwise in Fig. 3, and depresses the plunger e, and the operator at B turns the handle f counterclockwise in Fig. 3. The result at A is as follows: the pawl s lifts the rack m on the back of the dial plate; the pawl is withdrawn; the locking- die 6 is rotated to release the plunger e, which may then be depressed, and the tooth 15 lifts the slide 13 and closes the contacts 16; the crank 30 lifts the rod 29, thereby removing the spring pressure on the armature rocker 1. The opening c in the casing is covered by the bar 11 connected to the slide 13 by the rod 12. At the station B the tooth 23 lifts the slide 25 and closes the contacts 26. A circuit through the magnets w at A and 22 at B is closed as follows: battery 32 at B, contacts 26, magnet 22, contact 34, line wire 35 from B to A, contacts y, x, magnet w, contacts 16, contact 37 to earth. The magnet w at A moves the rocker 1, the rod 18 releases the slide 13 from the tooth 15 thereby opening the circuit at contacts 16, and uncovering the opening c, and the end of the rocker 1 holds the slide m. The rocker is held in this position by the latch 9 engaging the surface of cam 7, until the handle f is replaced, thereby returning the latch n to hold the slide m in its new position in which the inscription ' 1 up ' is exposed to the opening c. At station B, the magnet 22 rocks its armature 20 and withdraws the latch n and pushes forward the latch 19 to hold the slide m after it has fallen half the distance between two teeth. The slide 25 is released from the tooth 23 and opens the contacts 26. When the magnet 22 is de-energized the latch 19 is withdrawn and the latch n reset to catch and hold the slide m at the next tooth. The inscription ' 1 up ' is then exposed at station B. The terminal 37 serves as a lightning-arrester. Proper operation of the instruments is indicated by a polarized needle detector b, the circuit to which is made through studs 38, 39, alternately and contacts 45, 47 and the line wire to similar contacts at the other station so as to connect two half batteries in series if the instruments are in correct positions or in opposition if the instruments are out of step. The current passes in alternate directions so as to deflect the needle to opposite sides at each operation of the instruments. When no current passes the needle stands vertical. The contact 53 serves as a detector for normal position by moving the two handles f so as to connect contacts 47, 53 at each station.