Patent GB-190106449-A (GB)
Title: Improvements in Pnuematic Apparatus for Operating Railway Points, Signals, Crossing-Gates, and the like.
Inventor: O'DONNELL JOHN PATRICK
Filed: 1901-03-27
Granted: 1902-03-20
Abstract: 6449. O'Donnell, J. P., [Corrington, M., and Dodgson, F. L.]. March 27. Semaphore &c. signals; controlling and locking signals ; interlocking ; indicators and repeaters, point &c.-Relates to the pneumatic operation of railway signals, points, gates, bridge-locks, &c. on the system described in Specification No. 183, A.D. 1900. In the present invention, the air is not exnausted from the cylinders and pipes on the completion of each cycle of operations, the movement and indication in one direction being obtained by reducing the pressure below a mean pressure, and in the other direction by increasing the pressure above the mean. Also, only one indicating-pipe is employed to indicate both positions of the switch, or signal, &c., the ' safety' position of a signal, as well as its 'danger ' position, being indicated. Fig. 1 shows the arrangement for operating a switch, that for a signal being similar, except that the semaphore arm is actuated directly from the piston of the operating-cylinder C, instead of through a motion plate M. Air at the mean pressure is supplied from the reservoir A<1>, and air at a higher pressure than the mean from the reservoir A, which may feed the reservoir A' through a reducing- valve. In the position shown, air at the mean pressure is in the operating - cylinder C, the indicating-cylinder I<2>, the operating-pipe o, the indicating-pipe p, and the distributing-valves T, T'. To reverse the points, the operating lever or slide L is moved to the left, until the rollers of the pistons in the indicating-cylinders I<2>, I<1> abut respectively against the shoulders d<3>, d' of the slide. By this movement, the valve V is brought into position to connect the pipe o with a higher pressure supply in the reservoir U, which was filled from the supply pipe S' when the valve was in the normal position. The increase of pressure in the pipe o effects the movement of the distributing-valve T to such a position that air is exhausted from the left of the cylinder C, and air is admitted from the main supply to the right of the cylinder, the consequent movement of the motion plate M reversing and locking the points, as described in the Specification above referred to. Before the end of this movement, the plate M actuates the lever a, and moves the indicating- valve D so that the pressure in the indicating- pipe p is decreased, by its being put in connection with a reservoir W, which was previously open to the atmosphere. The reduction in pressure in the pipe p causes the distributing-valve T<1> to be moved to its other extreme position, in which the cylinder I<2> is exhausted and pressure is admitted into the cylinder I<1>, so disengaging the piston rollers from the shoulders d<3>, d<1>, and permitting the completion of the stroke of the operating- slide L, which also completes the stroke of the interlocking bar B. The cycle of operations for putting the switch to normal is similar, except that the pressure in the pipe o is reduced, by connection with the reservoir U<1> previously opened to the atmosphere, and the pressure in the pipe p is increased, by connection with the reservoir W<1> previously fed from the higher pressure supply. On the completion of each movement of the slide L, the pressure in the distributing-valves and pipes is equalized. The construction and action of the various valves are fully described in the Specification. A bar 49 on the slide L is provided at each end with a series of ratchet teeth adapted to be engaged by the pivoted double pawl 50, to ensure the completion of the stroke of the slide L, the pawl being reversed by studs on the slide at the end of each stroke. The space between the ratchets is sufficient to permit the switch &c. to be reversed after it has been thrown in one direction, but the pawl prevents the completion of the reversing stroke even after indication, Fig. 21 shows an arrangement for completing the stroke of the slide automatically, the pistons of the indicating-cylinders I<5>, I<6> acting on the upper surfaces of the inclined slots in ths slide L. As the cylinder which completes a movement of the slide remains under pressure, it is necessary to exhaust it before another operation of the slide can be effected. For this purpose, a slide valve 54 is interposed between the cylinders and their supply pipes, and is operated through the bar 64 by one or other of the two triggers 68, 69 on the slide, according to the direction in which the slide is to be moved. In one position, the valve connects one cylinder to exhaust and the other to supply, these connections being reversed by the movement of the valve to its other extreme position.