Patent GB-101348-A (GB)
Title: Improvements in or relating to Automatic Airbrake Systems.
IPC: B61L3/12
Filed: 1915-12-31
Abstract: 101,348. Sprague Safety Control & Signal Corporation, (Assignees of Sprague, F. J.). Dec. 31, 1914, [Convention date]. Electrical systems, automatic; track apparatus actuating signals on trains and for stopping trains.-A vehicle is controlled by a unicyclic current generated in a conductor on the vehicle moving into and out of the field of a magnet on the track; the apparatus is adjustable so that the energy of the induced current varies with the speed of the vehicle and with the strength of the magnetic field, and may be arranged to suit different conditions requiring application of the brakes. The detector circuits on the train include relay devices as described in Specification 104,176, [Class 38 (iv), Electric supply and transmission systems &c.], which comprise a coil 433 in a circuit of constant potential, normally shunted by a branch circuit including the contacts 452, 411 which, when opened, is maintained open by the said coil. In the train apparatus according to the present invention, the primary opening of the shunt circuit is caused bv the unicyclic induced current passing in the coil 410 opening the contact 411. The circuit to the electro-magnets on the track is controlled by track relays, as shown in Fig. 1. The relays 328, 348 are controlled by the track relay 307'. The circuits to the track magnets 320, 340 are further controlled by the relays 303, 303<1>, which are de-energized to close these circuits only when an approaching train bridges the insulating-joints in the track rails. By properly proportioning the size of the track magnets 320, 340 and inductive receivers 400, the windings on these members and on the detector relay 410, and the magnitude of the non-inductive resistance 413 in the detector circuit, the magnitude of the current in the detector relay may be made proportional to the speed of passage of the receiver over the track magnet. This enables the apparatus to be adjusted so that the detector relay may draw its armature only when the train is running above a predetermined speed over a track magnet. The sensitiveness of the detector is varied by the adjustment of the air-gap and of the retracting-spring of the armature and the non-inductive resistance. For limiting the speed of trains over a given section of track the apparatus may be arranged so that an operative impulse is received only if a track magnet is passed at a speed in excess of the predetermined limit, or the track magnets may be spaced apart at different distances, and the cycle of operations on the train so timed that, if a second impulse is received by the detector in less than a given time after the previous impulse, the brakes are applied. The strength of each of the track magnets is also determined by the braking conditions required. At curves or other places where it is required to limit the speed of trains passing in one direction, while no restriction is necessary in the other direction, a track magnet of the strength required, according to the allowable speed, may be connected up as shown in Fig. 17. A length of rail 312<1> is insulated and connected, through a rheostat 370 and a battery 322 to the magnet 320, the other pole of which is connected to the other rail. The magnet 320 is placed a suitable distance beyond the rail 312', dependent upon the wheel base of the locomotive. A train A moving towards the curve completes the circuit to the track magnet as soon as its first wheels run on to the insulated rail 312<1>, and the length of rail is sufficient to allow the magnet to obtain its maximum field by the time the receiver 400 passes the magnet, and this field is such that, if the speed of the train is excessive, the detector on the train is energized. If the locomotive is running backwards off the curve, the magnet is only energized as its first wheels run on to the rail 312<1>, and the magnet 320 has only a weak field when the receiver 400 passes. If the engine runs off the curve funnel-first, the receiver passes the magnet before the circuit thereto is closed. The Specification as open to inspection under Sect. 91 (3) (a) includes also the subject-matter of Specification 104,176, [Class 38 (iv.), Electric sup. ply and transmission systems &c.], which does not appear in the Specification as accepted.