Patent GB-189714220-A (GB)
Title: Improvements in Steam and other Fluid Pressure Engines.
Inventor: SCOTT ARTHUR FORBES
Filed: 1897-06-11
Granted: 1898-06-11
Abstract: 14,220. Scott, A. F. June 11. Compound engines; central-valve engines ; valves and v a l v e gear.-Relates to steam and other fluid-pressure engines of the kind described in Specifications No. 15,858, A. D. 1886, No. 12,258, A.D. 1889, and No. 21,955, A.D. 1892, in which certain receivers or clearance spaces are employed to provide a continual thrust downwards or against the crank. The present invention comprises various improved arrangements of such engines, chiefly compound engines with tandem cylinders in which the pistons move in opposite directions and work on three cranks; it also comprises centralvalve engines, various modifications of a form of linkage valve gear, and means for nullifying the effect of the obliquity of the connecting- rods. (1) In the arrangement shown in Fig. 1. the pistons H<2>, L<2> have their apposed faces open to the inter-piston space or receiver R<2>. The rod of the former piston works through the latter and drives a central crank, while the low-pressure piston drives two opposite cranks, one on each side. Steam, partly under the control of the piston distributing-valve V, and partly under the control of the pistons themselves, is first expanded on top of the high-pressure piston, then beneath the lowpressure piston, and during the latter part of their return stroke is compressed in the inter - piston, space and in another receiver R in order to maintain the connecting-rod bearings in constant thrust against the crank-pins. (2) Fig. 5 shows a form in which the high-pressure cylinder is disposed so that its piston-rod passes as closely as possible to the wall of the low-pressure cylinder. This allows the valve-chest to be placed in very close proximity to each of the two cylinders. (3) In Fig. 7 is shown the application of the invention to a central-valve engine. The lettering in this case is the same as in Fig. 1. Other examples of central-valve engines are also shown in the Specification. (4) In each of the above engines the piston distributing-valve may be balanced by a method resembling that employed for maintaining the downward thrust on the main pistons. This is effected through the medium of a valve receiver space F. (5) Several modified forms of Joy's valve gear are described. In that shown in Fig. 1, the valve-actuating floating lever T is pivoted at one end to the high-pressure connecting-rod and at the other end to a link W connected to the valve-spindle crosshead. At an intermediate point it is pivoted to a radius rod U, the point of support of which can be adjusted in the curved guide Y for reversing the engine or varying the grade of expansion. (6) The effect of the obliquity of the connecting-rods is to disturb the balance of the inertia of the pistons and parts working in opposite directions. In order therefore to cause the vertical motion of the piston to synchronize more accurately with that of the crank, the crosshead is made in two parts. The piston-rod is attached to one of these, H<4>, to which the connecting-rod is linked by an arm Q, Fig. 21.