A history of the growth of the steam-engine . is links connecting the wrist-plate with the arms movingthe steam-valves have catches at their extremities, whichare disengaged by coming in contact, as the arm swingsaround with the valve-stem, with a cam adjusted by thegovernor. This adjustment pennits the steam to follow thepiston farther when the engine is caused to slow down,and thus tends to restore the proper speed. It disengagesthe steam-valve earlier, and expands the steam to a greater STATIONARY ENGINES. 321 extent, when the engine begins to run above the properspeed. When
A history of the growth of the steam-engine . is links connecting the wrist-plate with the arms movingthe steam-valves have catches at their extremities, whichare disengaged by coming in contact, as the arm swingsaround with the valve-stem, with a cam adjusted by thegovernor. This adjustment pennits the steam to follow thepiston farther when the engine is caused to slow down,and thus tends to restore the proper speed. It disengagesthe steam-valve earlier, and expands the steam to a greater STATIONARY ENGINES. 321 extent, when the engine begins to run above the properspeed. When the catch is thrown out, the valve is closedby a weight or a strong spring. To prevent jar when themotion of the valve is checked, a dash-pot is used, in-vented originally by F. E. Sickels, This is a vessel havinga nicely-fitted piston, which is received by a cushion ofwater or air when the piston suddenly enters the cylinderat the end of the valve-movement. In the original water-dash-pot of Sickels, the cylinder is vertical, and the plunger. Fio. 99.—GreeDe Engine. or piston descends upon a small body of water confined inthe base of the dash-pot, Corlisss air dash-pot is now oftenset horizontally. In the Greene steam-engine (Fig. 99), the valves are 323 THE STEAM-ENGINE OF TO-DAY. four in number, as in the Corliss. The cut-off gear consistsof a bar, A, moved by the steam-eccentric in a directionparallel with the centre-line of the cylinder and nearly co-incident as to time with the piston. On this bar are tap-pets, C C, supported by springs and adjustable in height bythe governor, G. These tappets engage the arms £ B, onthe ends of rock-shafts, E E, which move the steam-valvesand remain in contact with them a longer or shorter timeand holding the valve open during a greater or less part ofthe piston-stroke, as the governor permits the tappets torise with diminishing engine-speed, or forces them down asspeed increases. The exhaust-valves are moved by an in-dependent eccentri
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Keywords: ., bookcentury1800, bookdecade1870, bookidc, booksubjectsteamengines
