Patent GB-190518402-A (GB)
Title: Improvements in Apparatus for Working Railway Signals and Points by Compressed Air or other Gas.
Filed: 1905-09-12
Granted: 1906-08-09
Abstract: 18,402. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. Sept. 12. Compound and multiple expansion engines; valvegear; engines with reciprocating cylinders. - In pneumatic-power actuation of railway signals and points, both forward and return strokes are positively made by compressed-air actuation, and the air used for the forward stroke is further expanded in another cylinder to provide the return stroke, the valves being electro-magnetically actuated. The mechanisms are locked by mechanical catches in certain positions. In one form, a valve 4, Fig. 1, is opened when an electro-magnet 1 is energized by movement of a signalman's lever, and compressed air is thereby admitted to a cylinder A to lower the signal. When the magnet 1 is deenergized, the armature 7 falls, closing the valve 4 and opening a valve 3 so that the air passes from the cylinder A to a cylinder B of larger diameter to raise the signal. The air expansion in the cylinder B is preferably arranged so that the final pressure is below atmospheric, so as to provide a braking suction action of the piston. The valve 5 has been previously closed by contact with the base of the cylinder B; or the valve 5 may be dispensed with; leakage past the piston of the cylinder B being allowed after it has traversed a short'distance in its stroke. The first portion of this stroke may thus provide a cushioning effect to avoid concussion. To ensure the fall of the armature 7 when the magnet 1 is de-energized, a second electro-magnet 2 is provided which positively ensures descent of the valve-rod and armatures. A spring catch 6 may'be provided to engage with a notch 9 in tkie ledee C to prevent unauthorized attempts to lower the signal by a pull on the rod. Normally this catch is held in inoperative position by a lever 6 actuated by the armature and valverod of the magnets 1, 2: In another form, the cylinders A, B, Fig. 2, are placed side by side and and the pistons actuate a rocking lever C connected to the signal or point mechanism. The piston of the cylinder A is only connected to the lever C through a locking-piece 9, so that initial movement of this piston moves the piece 9 out of the path of a stop 10. When the air passes from the cylinder A to the cylinder B for the return stroke, the spring 11 returns the piece 9 into the locking position to lock the signal in the danger' position. In another form, one cylinder A, Fig. 3, forms the piston of the larger cylinder B. The valve 4 is first opened and air passes through the flexible pipe 17 to the cylinder A, the pistou'12 of which begins to descend, driving a lever 15 against a stop 16. This stops the downward motion of the piston 12, so that the relative motion of the piston 12 and cylinder A is obtained by the ascent of the cylinder A in the cylinder B, so operating the signal through tho lever C. The reverse motion is obtained by opening the valve 3, when the cylinder A is driven downwards, acting as piston in in the cylinder B ; downwards, acting as piston in the cylinder B; finally, a spring restores the lever 15 to its normal position, locking the lever C against unauthorized attempts to operate it. A different piston may be employed with two ends of different diameters, working in different cylinders, the smaller one exhausting into the larger for the return stroke ; or equal cylinders may be used, the second piston being connected to the semaphore-operating lever at a greater distance from its pivot than the forward-stroke piston.