Patent GB-352461-A (GB)
Title: Improvements relating to the cylinders, distribution valves, and valve gears of steam engines and the like
IPC: F01L15/12
Filed: 1930-04-08
Abstract: 352,461. Valves and valve gear. PETTY, T., Dormin, Greta Avenue, West Hartlepool, and RICHARDSONS, WESTGARTH & CO., Ltd., Hartlepool Engine Works, Hartlepool, both in Durham. April 8, 1930, No. 11140. [Class 122 (ii).] A uniflow engine is provided with mechanicallyoperated balanced flat slide valves and is designed to obtain minimum axial dimensions of cylinders and pistons. The admission, main exhaust, and compression in a cylinder is controlled by one valve. Separate passages for the steam and exhaust are provided in the valves, and in addition compression control passages operating in conjunction with cylinder compression control ports. The cylinder A has steam ports B, exhaust ports C, and a balanced slide valve E with steam ports F and exhaust ports G, one for each end of the cylinder. The exhaust ports are provided with sufficient lap 4 to ensure closure of the exhaust at the valve face when the piston is at mid position and overlaps the ports C by an amount l. The centre N of the ports C is displaced below the position of the centre of the effective piston depth when the piston is at mid stroke to allow for the effect of the obliquity of the piston and valve connecting rods. Alternatively the piston depth may equal the exhaust port depth plus the amount l, and premature exhaust on the down stroke may be prevented by increasing the exhaust lap on the lower half of the valve and increasing the valve travel. In radial-gear driven valves, the valve is given an asymmetrical motion to compensate for the asymmetry of the piston motion. A method of obtaining such a motion from a Marshall gear is described. Release is effected and undue compression prevented by ports O controlled by narrow ports P on the side of the valve, the exhaust passing initially to the auxiliary cylindrical pocket Q adjacent the main exhaust port D. The ports S may be closed by the piston or by the valve. The steam, main exhaust, and auxiliary exhaust ports F, G, P are arranged at both the front and back of the valve. The exhaust begins and ends through the auxiliary ports O, P, Q, R and the main exhaust begins by the valve uncovering the edges e, f, and ends by the piston closing ports C. Alternate methods of separating the main and auxiliary ports and passages are described. In the initial or intermediate cylinders of multiple-stage engines the ports O may be placed in a central position, or there may be more than one port. In a modification, both the upper and lower ports G and pockets H control the exhaust from each end of the cylinder, the edges of the valve providing thereby a fourfold discharge. In a further modification, instead of providing separate compression ports, portions of the steam admission ports are separated from the rest by suitable walls, and compression control ports are incorporated in the valve. In the modification shown in Fig. 7, the auxiliary exhaust ports P connect the ports O through upper and lower pockets H. The exhaust traverses openings V through the valve and pockets Y formed in the balancing saddle X. In a further modification, Fig. 10, two series of main exhaust ports c, c<1> are provided. The exhaust from the port C to the three pockets H is indicated by arrows 1, 2, 3, 4. Arrangements are described wherein the operating eccentric moves in excess of 90‹ in advance of the piston crank in contradistinction to the above constructions wherein the eccentric follows the crank. The ports F in the valve may be constructed as shown in Figs. 16 and 18. The bar 5, Fig. 16, separating the port B from the steam chest or receiver 6 is made as narrow as possible, and an additional passage 7 of the same breadth as the port B is provided through the valve and has a width equal to the port opening. A balancing passage 10 connects the cavities 9, 9<1>. These provide additional clearance space. The steam admission ports may in some cases be constructed as shown in Fig. 20. The passage 12 has a width equal to the maximum port opening, and a transverse breadth equal to that of the port B at the valve face. It is separated from the steam chest by a bar 13. Passages in the valve, e.g. 17, or in the saddle, are provided to maintain the pocket 14 in communication with the port 13 for balancing purposes. The pockets are made small to reduce the clearance. The pockets and passages may have rounded edges, or the passages may be formed as convergent-divergent nozzles 12, Fig. 23. Pressure losses by impact and eddy currents and the volume of the ports may be reduced by the construction shown in Fig. 17.