1176
THEORY AND PRACTICE OF ENGINEERING.
Book
The Chain Pump farShips is formed of a longchain, with a number of pis-tons or buckets fixed uponit at regular distances, andwhich pass over two wheelscalled sproket wheels; byturning the upper one, thebuckets are put in motion,and working in a woodentube lined with brass, asthey mount they raise thewater on the ascending side,which flows off by a troughplaced over the ship’s side.
The links of the chain areformed of two iron plates,and the buckets or saucersare two circular brass plateswith a piece of leather be-tween them.
Double-acting Fire En-gine is worked by a doublesector of iron, which has asufficient breadth of sole toreceive two chains, similarto those used in a clock:one chain is fastened to thebottom of the arched headand to the top of the piston-rod, and the other chain isfixed at one end of the topof the arched head and thelower part of the piston-rod,so that when the sector de-scends on one side, the chainfixed at its lowest partwinds round, and pullsdown the piston on that side, whilein the opposite sector the chainfixed on the upper part of its archedhead winds round and raises theother piston: the reverse takesplace at the next stroke, so that acontinued action is maintained, thewater rushing at the same timethrough the lower valve, from thecistern, and fills the cylinder; andwhen the piston descends, this valveshuts by the pressure of the water,and is forced through anothervalve into the air-vessel, the upperpart of which is filled with aircompressed by thus forcing thewater in, and which, acting by itselasticity on the surface, causes thewater to be thrown up with con-siderable velocity. An iron handleis attached to the air-vessel, whichsets the cock into a position eitherto make a communication betweenthe cistern and barrels, or betweenthe feeding pipe and barrels, shut-ting off the cistern, according as theengine is supplied.
Eet us suppose the air com-pressed in the air-vessel to half its
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Fig. 1788. CHAIN PUMP, USED IN THE NAVY.
Fig. 1789. DOUBLE'ACTING URB ENGINE