a a is a cylinder, which is supported upon a frame (not shown in the figure), and closed at each end by a cover b, the internal surface of which is faced so as to be a true plane,; x is a smaller concentric cylinder, into which is keyed the shaft e, and which therefore revolves with the shaft; c is a rectangular piston firmly connected to the smaller cylinder x, and furnished round its sides with metallic packing; g g are two sliders moving in steam tight cases i, and in rebates formed in the cylinder covers; they form the steam abutments, and are drawn alternately within the slide cases, to allow the piston to pass by means of a cam on the shaft, which operates on cross heads attached to the slide rods, which latter work in stuffing-boxes. After the passages of the piston the upper slider descends, and is brought to rest upon the revolving cylinder b by its own weight; the lower is pressed against the cylinder b, by a counterpoise: 6, 7, 13, and 14, are the passages by which the steam enters the cylinder, and passes off to the condenser, or the atmosphere, as the case may be.
These passages are connected with a steam chest, attached to the frame of the engine, and furnished with a common slide valve, for the purpose of reversing the engine, as will be hereafter explained.
In order to put this engine in motion, we will suppose that the slide in the steam chest is so arranged that the valves 6 and 7 are the induction valves, and 13 and 14 the eduction valves. The piston being in the position shown, the valve 14 is then open to the condenser, and the valve 7 to the boiler, and the steam rushing in between the upper slider, (which then forms the abutment) and the piston, forces round the latter in the direction of the arrow. As soon as the piston has passed the lower slider, the cam on the piston shaft recedes from the cross head of the lower slider, and the slider is gradually forced up by its counterpoise until it comes in contact with the shaft; the piston will then be at G and both sliders shut, and only the two valves 7 and 14 open. As the piston continues to revolve, the cams gradually open the upper slider and the valve 13, and gradually close the valve 14, so that when the piston reaches the valve 13, the former is completely shut, and the latter completely open, and when the piston reaches the upper slider, it is completely withdrawn from the cylinder, and thereby allows the piston to pass it. At this point, the steam is entering through 6, and escaping through 13, the lower slider being then the abutment upon which the steam acts.
After the piston has passed the upper slider, the cam allows the piston gradually to return to its place in the cylinder, and after the piston has passed the valve 6, that valve begins gradually to open, and the valve 7 to close. Therefore when the piston has reached the pipe, the upper slider is in its seat in the cylinder, the valves 7 and 14 are quite shut, and 6 and 13 quite open: the cam 4 then begins to give motion to the lower slider as before described, and the cam 10 to the valves, so that a constant rotation of the axis is kept up.
GALLOWAY's ROTATORY ENGINE.
To reverse the motion of this engine, the sliding valve in the steam chest is moved in its face, so that the valves 6 and 7 become the eduction valves, and 13 and 14 the induction valves.