MODERN STEAM PRACTICE.

316

made large enough to contain the quantity of water which can berequired from it at once by the simultaneous action of all thehydraulic machines connected with it. If, how-ever, the engine pumps more water into theaccumulator than the hydraulic machines re-quire, the plunger rises and makes room in thecylinder for the surplus; and when, on the otherhand, the supply from the engine is less thanthe quantity required, the plunger with its loaddescends and makes up the deficiency out ofthe störe. The accumulator serves also as aregulator to the engine, for when the plungerrises to a certain height it begins to close thethrottle valve in the steam pipe, so as graduallyto reduce the speed of the engine, until thedescent of the plunger again requires an increaseof power. The introduction of the accumulatorremoved all the obstacles to the extension ofwater-pressure machinery, which has been nowpractically tested in nearly all the principaldocks and in many of the government establish-ments in this country. This dass of machineryFi g . 201.—verticai Secdon of has also been adopted in many of the principalAccumulator.— a, Cyimder. ra q wa y s t a tions, not only for cranage, but also

b, Plunger, c, Loaded case. J 7 J 07

for working turntables, traversing machines,waggon-lifts, hauling machines, &c. It is also extensively used forraising and tipping waggons in the shipment of coal, for openingand closing bridges, and for many other purposes.

PUMPING ENGINE FOR CHARGING THE ACCUMULATOR.

The most approved form of the pumping engine for chargingthe accumulator is that of two high-pressure cylinders fixed hori-zontally, with double-acting pumps directly connected with thepiston rods; the form of pump being the solid bücket and plungerSystem. In the arrangement shown (Fig. 202) the OUT stroke of thepump forces the water contained in the annular space surroundingthe plunger E into the accumulator, while a further supply of waterenters behind the piston F through the suction valve G. In theIN stroke the water behind the piston is discharged through the