Patent GB-190911460-A (GB)
Title: Improvements in the Electric Staff or Tablet System of Controlling Railway Traffic.
Inventor: BLACKALL ALFRED THOMAS
IPC: B61L23/24
Filed: 1909-05-14
Granted: 1910-05-05
Abstract: 11,460. Blackall, A. T., and Jacobs, C. M. May 14. Staff and tablet systems.-A modified apparatus of the kind described in Specification 424/05, is described for using occupation instruments in a section between stations in which tablet instruments of the kind described in Specification 23,311/98, are employed. Each occupation instrument is provided with a battery. Fig. 1 shows an elevation, and Fig. 2 a plan view of an occupation instrument, with a tablet t inserted in the instrument, the tablet being provided with an attached key K for this purpose, although the tablet itself might be used as a key. A disk commutator C mounted on a spindle S is rotated by the key K, which engages with a boss b. Projections on a locking-disk D mounted on the spindle S engage with a lever i attached to the armature h of an electro-magnet M. The movements of the disk C are thus controlled by the locking-disk D and the magnet M. Contact springs 1 ... 6 engage with shaped contact strips on the disk C, and two polarized relays P', P' are provided in each instrument. In the normal position of the apparatus shown in Fig. 4, the line l connecting the tablet instruments T<1>, T<2> is connected at each of the two occupation instruments shown through the contact springs 2, 3 and a strip 12 on the disk C. If a tablet is inserted in an occupation instrument, the disk C can be turned clockwise from the first to the second of its five different positions. This locks the tablet in the instrument and connects one side of the line l through the spring 2, strip 13, and spring 1, to a key k<1> and the other side of the line l through the spring 3, strip 14, spring 4 to a key k<2>. Since the tablet instruments T', T' are then in a condition corresponding to one tablet being out, any currents sent will be of positive polarity, and will operate the polarized relays P<1>, P<2> to complete the circuit of a local battery b<2> and the magnet M through the contacts 7, 8. The energization of the magnet M frees the lock on the disk C, which may be turned clockwise into the third position. When this has been done, and the current from a tablet instrument has ceased, the magnet M is de-energized and the disk C locked. In the third position, the polarized relays P<1>, P<2> remain connected to the tablet instruments as before, and, in addition, the negative pole of a local battery b<1> is connected to the front contacts 11 of the keys k<1>, k<2> through springs 5, 6 and a strip 15. If then the keys k<1>, k<2> are depressed, currents of negative polarity are sent through the tablet instruments, which allow the restoration of the tablet instruments in the known manner to their normal positions, in which currents of negative polarity can be sent from them to line. If such currents are then sent to the occupation instrument, the polarized relays P<1>, P<2> are energized, and the circuit of the magnet M is completed through the contacts 9, 10. The energized magnet M releases the lock on the disk C, which can then be turned to the fourth position, and since the locking-projection g, Fig. 1, in this position is inclined, the disk can be further turned into the fifth position. In this position, the keys k<1>, k<2> are disconnected from the line l, and the magnet M is deenergized, so that the disk C cannot be turned back from the fifth beyond the fourth into the third position. In the fifth position, the-tablet line l is connected through the springs 2, 3, and a strip 16, and a tablet can be withdrawn from either tablet instrument. To withdraw a tablet from an occupation instrument, the disk C is turned back from the fifth into the fourth position, to connect up the divided line l to the relays P<1>, P<2> through the springs 1 ... 4 as before. Current of negative polarity is then sent from a tablet instrument, which energizes the relays P<1>, P<2> and closes the circuit of the magnet M through the contacts 9, 10. The energized magnet M releases the locked disk C, and allows it to be turned back into the third position. In this position, as described above, negative current can be sent from the occupation instrument to the tablet instruments, enabling halfdrawers to be obtained at the tablet instruments in the known manner. In this position, positive current can be sent from each tablet instrument, which operates the polarized relays P<1>, P<2> to complete the circuit of the magnet M at the contacts 7, 8, so that the lock is again removed, and the disk C can be turned back from the third through the second to the first position, after which the tablet can be taken out of the occupation instrument.