Patent GB-190327493-A (GB)
Title: Improvements in Apparatus for Operating Points and Signals on Railways, Tramways, and the like.
Inventor: WALKER JAMES GREENHALGH
Filed: 1903-12-15
Granted: 1904-12-15
Abstract: 27,493. Walker, J. G., and Bidder, F. W. Dec. 15. Semaphore and similar outdoor signals. -Relates to apparatus for pneumatically operating points and signals on railways, tramways, and the like, which consists of an operating- frame, situated in the signal cabin, and a controlling-cylinder situated near the points or signals for working the same, a separate operating-frame and cylinder being employed for each signal or set of points. The operating-frame, one form of which is shown in sectional side and end elevation in Figs. 1 and 4, respectively, is cbaracterized by a hand-operated disc or cylindrical valve V having recesses on its periphery which are arranged to communicate with the seven ports as required. The port P is in permanent communication with the supply of compressed fluid, and the pipes F<1>, F with the point or signal controlling cylinder. The valve is oscillated to one side or the other, when the handle H is moved, by the interaction of one set of the large teeth N<3>, N<2> and the corresponding hooked pawl C', C, and is returned to its central position by the corresponding weight W<1> or W when the pawl is released by contacting with one of the tripping-pieces K<1>, K. The locking-bars S, having teeth which engage with the small teeth R, R', prevent the handle H from being reversed before completing its movement in either direction, and also prevent the completion of the movement in that direction until the " indication " current" has been received in the corresponding cylinder A or A. When either of the locking- barshas been raised by the "indication current," it is locked in its raised position by the bolts T, T'. The Provisional Specification describes a form of the apparatus in which a loose sleeve is mounted on the lever bar M, carrying pivoted tripping-catches of bell-crank form and also a fork-piece to engage with the stem on the valve V and to rock the same. Another device, to prevent the lever bar from being pushed back before completing a stroke, consists of a slide connected to the lever bar and provided with catches and inclined faces, in connection with which works a double-ended tumbler formed with a slot and mounted loosely on a transverse rod. This catch is held down by weighted or spring-controlled pieces until raised by the inclined face of the slide as the slide advances ; it is then pushed over and tipped in the opposite direction. The controlling-apparatus at the signals consists of a cylinder D, Fig. 7, having ports Y<1>, Y', Y<3>, Y<4>, a valve Y working in a valve casing which is connected to the operating-frame by the pipes F<1>, F, and an exhaust port EX. The port VT allows the escape of any fluid that has found its way into the space between the piston ends. The valve casing is formed with a slot through which works the valve slide VS<1> operated directly from the piston-rod. On the front of the valve Y, and formed integrally with it, is a projecting boss a placed parallel to the valve and working in the slide VS<1> as shown in Figs. 8, 9, and 10. Fig. 12 shows a sectional plan of the slide in its slot in the valve casing. As the slide approaches the end of its movement, the boss a is forced into a vertical position, the corresponding end of the double-ended spring b<1>, b<9> being pressed into one of the recesses c, c<1> until it becomes vertical, when the spring is liberated. When compressed fluid is again admitted to the cylinder through either of the pipes F, F<1>, the consequent movement of the piston operates the slide VS<1> which, through the action of the spring, causes the valve to tilt so that compressed fluid is still admitted to the same side of the piston but the other side is connected to exhaust. Upon the completion of the stroke, the valve again becomes vertical, an indication current being then sent through one of the ports Y<3>, Y<4>, to the operating-frame so as to allow of the completion of its movement. The extension of the piston-rod contains a slot DLM in which works the lever DL. To put the signal to "clear," the lever DL is drawn along until the pawl M catches on the fixed piece Z. To place the signal to "danger," the piston is driven outwards, when the cam-surface MZ raises the pawl M and allows the semaphore arm to rise. A safety locking-apparatus GB is attached so as to lock the valve should any of the rods break.