Patent GB-857380-A (GB)
Title: Improvements in steam and like engines
IPC: F01B17/04
Filed: 1955-09-29
Abstract: 857,380. Steam engines. WILLANS, K. W. Dec. 31, 1956 [Sept. 29, 1955], No. 27733/55. Classes 122 (2) and 122 (3). A steam or other expansible fluid-reciprocating engine comprising a plurality of cylinders 5(1), 5(4) to which the working fluid is admitted in turn, is arranged so that for each cylinder (say 5(1)) the working fluid admitted to that cylinder flows successively through a transfer port 20(4) controlled by a valve 15(4) moving with the piston 8(4) of an adjacent cylinder and then through an inlet port 21(1) controlled by a valve 15(1) moving with the piston 8(1) of the cylinder 5(1) to which the working fluid is to be admitted. The engine shown comprises four cylinders having parallel axes arranged at the corners of a square, the pistons being coupled in pairs to two twothrow crank-shafts 9, 10, in which the throws of each shaft are set at 90 degrees and the two crank-shafts are so geared together that they rotate at the same speed in opposite directions and the pistons 8(1), 8(4) of adjacent cylinders are out-of-phase by half a stroke, the corresponding throws of the cranks of the two crank-shafts being displaced at 90 degrees. The piston valves 15(1), 15(4), carried on tail rods 16 of their respective pistons, work in valve cylinders formed by liners 17 inserted in the common head casting 7. The valve cylinders 17 open into a common steam chest 18 at their upper ends and into their respective power cylinders 5 at their lower ends. Two ports 20(4), 21(1), each constituted by a ring of apertures in the walls are provided in the valve cylinders 17, each port communicating with an annular channel in the head casting, the upper or transfer port 20(4) of one cylinder being connected to the lower, or inlet port 21(1), of the adjacent cylinder. The upper edge of the piston valve 15(4) uncovers its transfer port 20(4) when the piston 8(4) is at mid-stroke or at any desired angle of lead before this position is reached. Working fluid is admitted to the cylinder 5(1) below the piston valve 15(1) and the transfer port 20(4) remains open during the working stroke of the piston 8(1) until cut-off occurs as the lower edge of the piston valve 15(1) closes the inlet port 21(1). When the inlet port 21(1) is again uncovered during the up-stroke of the piston 8(1), the transfer port 20(4) is closed by valve 15(4). Exhaust has meanwhile taken place in the cylinder 5(1) by the uncovering of the ports 23 in the cylinder wall by the piston 8(1) towards the end of its stroke. To obviate excessive compression of residual steam during the up-stroke a secondary exhaust system is provided by forming ports 25 in the tubular stem 16 of each piston valve 15(1), 15(4). The port 25(4) registers with the transfer port 20(4) during the early part of the down-stroke of piston 8(4) as piston 8(1) is nearing the end of its up-stroke, thus relieving pressure in cylinder 5( 1 ) through ports 25(4) and 26 to the exhaust chamber 24. Ports 25(4) and 20(4) will also be opened at an earlier part of the up-stroke of piston 8(1) and it may be arranged that the port 21(1) is also opened at this point to provide two periods of secondary exhaust. The pistons 29 are provided with rods 27 which pass through guide bearings 28, and with crossheads 29 guided by liners 30 in the crank-case 11. In an alternative construction (Fig. 2, not shown), the pistons 8 are of the trunk type and directly coupled to the connecting rods, the piston valves are built up from cup-shaped members with spacer discs between, and the tail-rods 16 r are solid and so do not provide for secondary exhaust. Water may be used for the lubrication of the bearings and the crank-shaft gears may be enclosed to form a lubricant pump. For alternative directions of rotation, a driven shaft may be arranged for selective connection to either crank-shaft, e.g. pinions may be slidably mounted on both shafts so that they may be alternatively engaged with the driven shaft, or constant mesh gears may be employed with friction clutch engagement for connecting the appropriate gear to its shaft. The pistons may be coupled in pairs to the opposite ends of rocking levers, or to a swash-plate, to drive a common shaft.