Patent GB-190601564-A (GB)
Title: Improvements in and relating to Staff and the like Signalling Systems for Railways and the like.
Filed: 1906-01-20
Granted: 1907-01-19
Abstract: 1564. British Thomson-Houston Co., [General Electric Co.]. Jan. 20. Controlling traffic on railways, staff systems for. -A purely automatic permissive system enables successive staves to be withdrawn for the dispatch of succeeding trains in one direction between stations, but no oppositely bound train may be dispatched until all the staves are replaced in one or other of the two instruments. Hunting-switch ratchet mechanism forms the basis of each staff instrument, and a special electro-magnetic locking- arrangement is provided at each staff receptacle. Fig. 1 shows diagrammatically the instruments of two adjacent stations A, A' ; at each station there is provided a ratchet-wheel B with oppositelypointing teeth on the two sides, and two electromagnetically-actuated pawls C effect the rotation of the ratchet. A locking magnet coil L and a safety magnet coil S control the issue of a staff, and require to be both de-energized and either one or both to be again energized before a staff may be completely withdrawn from its receptacle, as explained later. In the normal position shown, the circuit of the magnet L is open at the contacts f, and that of the magnet S is closed through the contacts h, e, an outer contact-ring D on the ratchet B, contact d, line 2, contact d', outer contact-ring D' on the ratchet B', contacts e<1>, h<1>, magnet S', battery I<1>, earth, and the battery I, back to the magnet S. On an attempt being made to withdraw a staff at the station A, the contacts J are closed by the staff and a circuit is closed energizing the right-hand coil G, the left-hand coil H, and through the line 1 energizing the righthand coil H<1> and the left-hand coil G<1> and being completed from the battery I' to earth and the battery I and to the contact J. The ratchet B is thus released by the left-hand coil H, and rotated one tooth in a clockwise direction by the righthand pawl C. Similarly, the ratchet B' is rotated one tooth in a contra-clockwise direction. This rotation causes the momentary de-energizing of the magnet S, the circuit being broken at the contacts e, and subsequent energization of the magnet S by the remaking of the circuit at the contacts h, e after rotation of the ratchet allows complete withdrawal of a staff. The rotation of the ratchet B' has, however, connected the contacts f<1> by the finger F, and permanently energized the locking-magnet L<1> until the ratchet B<1> is oppositely rotated by the insertion of the withdrawn staff. The energized magnet L<1> then prevents any withdrawal of the staves at the station A'. Succeeding staves may be withdrawn from the instrument at the station A, and with each withdrawal the ratchets B, B<1> moved, as described above, one tooth in the clockwise and counterclockwise direction respectively. When a staff is inserted in the receptacle at the statiou A<1>, the contacts J<1> are bridged, closing a circuit from the battery I' through the right-hand coil G<1>, the lefthand coil H', lead 4, right-hand coil H, left-hand coil G, battery I to earth, and back to the battery I. The ratchets B, B' are thus rotated one step backwards to their normal positions, and this happens with each succeeding staff inserted into the box at the station A' until, when all the staves are in one box or the other, the apparatus is in its normal position shown, and then a staff may be withdrawn from either box. Two sets of contacts e are provided on each ratchet B, all alternate contacts e being connected. If both ratchets are injured and do not rotate after the contacts J, J<1> are bridged, the circuits of the magnets S, S<1> are not broken, and the staff cannot be withdrawn. If only one ratchet rotates, the circuit of the magnets S, S' is not again made after being broken, because of this alternate connexion of the contacts e, e', and again a staff cannot be withdrawn. The staves K, Fig. 2, are contained in a box M, and carry a contact-strip k to bridge the spring contact-strips J, Fig. 1, on attempted withdrawal. If, in this attempt, either the magnet L, Fig. 2, or the magnet S is energized, the movable core s is raised, and the attached pivoted dog T enters a long-hole u in the staff, and prevents withdrawal in the dottedline position shown. If then the magnets L, S are de energized, the dog T falls, and allows the tablet to be withdrawn until another hole v is engaged by a rod P carried on a yoke O surrounding the rod N, and pivoted at o. Subsequent energizing of the magnet S then withdraws the rod P from the hole v, and allows complete withdrawal of the staff. In this final energizing of the magnet S, the dog T is of course again raised, but is moved by the spiral apring t against the under side of the staff behind the hole u.