Patent GB-191114974-A (GB)
Title: Improvements in Steam Engines.
Inventor: EASTWOOD WILLIAM
Filed: 1911-06-27
Granted: 1912-06-27
Abstract: 14,974. Eastwood, W. June 27. Combined fluid - actuated and mechanical gears; linkage gears; valve-spindles and valvespindle guides; slide valves; separate admission and exhaust valves.-Relates to admission valves and valve-gears suitable for ordinary and terminal-exhaust steam-engines, and also to exhaust valves and gears primarily for use in starting terminal-exhaust engines. The valve-spindles of the admission valves are provided with pistons which are engaged by separatelyoperated suction and closing cylinders to open and close the valve. The admission valve 4, Fig. 1, is made in two parts 4<a>, 4<b>, which may be forced against the perforated packing-ring 5 by fluid pressure or a spring. A spring may be arranged in the space behind the packing-ring. The valve-spindle 7 passes through a stuffing- box 8 and carries an enlargement 7<1> upon which are mounted suction and closing pistons 10, 19. Suction and closing cylinders 11, 20 are arranged to slide in the casing 12 and co-operate with the pistons 10, 19. The suction cylinder 11 is reciprocated by an eccentric 16 upon a countershaft 17 through a bell-crank 14 and links 13, and the closing cylinder is operated by link 20<a> and lever 20<b> from a countershaft operated by an eccentric, the angular position of which is adjusted by a shaft or other governor. A spring-pressed valve 23 is arranged in the spindle enlargement 7<1> and controls ports 24 by which air passes to the space between the parts 10, 11 to break the vacuum. The valve 23 is operated on the downward movement of the piston 20 by a spindle 26 connected thereto. The valve 4 is provided with a cushioning- chamber 30, and in the modification shown in Fig. 3 with a chamber 27 and a ported projection which slides over a stationary part 28. The steam entrapped in the chamber on the downstroke of the valve helps the next opening stroke of the valve. The operating eccentric of the closing cylinder may be hand-controlled, as when used for the low-pressure cylinder of a compound engine. In the modification shown in Fig. 2, atmospheric air is entrapped in space 34 above the suction cylinder and passes through port 35 to space 24 to assist in closing the valve. The pressure of this air counterbalances the upward steam pressure on the valve spindles. In lieu of the chamber 27, Fig. 3, an air chamber 38 is formed between the valve-chest cover 9 and the suction piston 10<1>. In a second modification, a spring is used to counteract the pressure of the steam on the valve-spindle, and, if desired, to help to close the valve. In a third modification, the suction cylinder and piston are placed away from the heated cover of the valve chest, and the part 20, which is in the form of a disk, is placed next the cylinder cover. The shaft carrying the levers 20<b>, 32 is placed out of centre to keep down the overall length. In a fourth modification, the suction cylinder is connected directly to the eccentric strap, the valve is placed horizontally, and the suction cylinder is placed away from the valve. The closing cylinders at each end of the main cylinder are operated by separate shafts, or by a common shaft when the governor-controlled eccentric runs at twice the speed of the engine. In constructions wherein the closing-cylinder makes two closing-strokes for one opening stroke of the suction cylinder, the cut-off is rapid and confined between o ne - quarter and sevensixteenths of the stroke. In the arrangement shown in Fig. 7, the closing-cylinder and piston are dispensed with. The air compressed by the suction cylinder is passed by a normallystationary governor-controlled valve 23 to operate on the end of the suction piston and close the valve. The disk 19<Î> supports the weight of the spindle and relieves the stuffing- box. When the steam valve 4 is brought to rest by an internal cushioning chamber 30, Fig. 1, the suction-cylinder walls and casing 12 may be provided with holes to break the vacuum and the valve 23 dispensed with. The auxiliary exhaust valve, Fig. 1, consists of parts 42, 42<1>, 43, 43<1> between which are arranged packing- rings. The parts 43, 43<1> form a relief valve and may slide along a key 45 on the spindle 46 against the resistance of a spring 47. The valve is actuated by a suction piston 50 working in a cylinder 48 secured to the spindle when there is pressure in the condenser, but becomes inoperative when the condenser vacuum is formed. The piston 50 is operated by the steam eccentric 16 through a bell-crank which reciprocates a sleeve 54, 56 secured in its operative position between a collar 57 and a fly-nut 58. In a modification, the auxiliary exhaust valve is operated by a lever connected to the suctionpiston operating-pin. The lever closes the valve by pressing on the end of the valve-spindle, and opens it by engaging a weighted pivoted catch, which is thrown out of gear when the engine attains its full speed. In ordinary engines having two admission and two exhaust valves, the valve controls the main exhaust, the suction cylinder 48, Fig. 1, is dispensed with, and the spindle is positively operated by the bell-crank 52. When using the valve - gears on non- condensing engines, the cylinder ends are provided with auxiliary clearance spaces which are put into communication with the cylinder when the engine is stationary; or the piston is made with reversible sections containing cavities which may be arranged towards or away from the cylinder space; or the engine may be provided with an additional shallow piston to replace the ordinary piston. The Provisional Specification also states that where the engine is non-condensing and the desired speed has been attained, the vacuum in the cylinder 48, Fig. 1, may be broken automatically or by hand; or the exhaust valve may be operated through a clutch or clutches put into action by the governor when the speed is below the normal.