STATIONARY ENGINES.
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as also a plug tap, which can be regulated at pleasure from theengine-room floor. There is a central rod secured through thebottom of this internal box ortray, and connected to a leverweighted at the end, with a fixedpin as the fulcrum, placed be-tween the weight and the box;this weight is slightly in excessof the tray and adjuncts whenthe internal box is full of water.
The action is as follows:—Theoutside box, in the first place,must be nearly full of water, andwe will suppose the tray emptyand raised by the weight actingthrough the oscillating lever; theplug rod of the engine descend-ing acts on mechanism that de-presses the tray, and water flowsthrough the flap valves in the bot-tom until the plug rod ascends,when the preponderance of the weighted lever raises the internalbox or tray above the level of the water in the outside box, conse-quently the water in the tray gravitates into the external reservoir—hence the name cataract; and the time the water takes to flow outof the one into the other is regulated by the plug tap,—if it is fullopen the water will flow out quickly, and the tray will rapidlyascend, the cataract rod releasing the valves; but should the plugtap be nearly closed, it is evident that the water will flow out of thetray slowly; and as this tap is regulated, the number of strokes ofthe engine will be increased or diminished: but the number of strokesrarely exceeds twelve per minute as the maximum, and four perminute as the minimum. This form of cataract is exceedinglysimple, and even rüde in construction, yet it answers the purposeadmirably so long as the level of water is maintained in the externalbox, which must be looked to occasionally, as evaporation will takeplace or leakage occur.
Instead of the wooden tray a plunger pump (Fig. 105 ) is sometimesfitted inside of a box of cast iron, having a valve at the bottom foradmitting water or oil into the pump, fitted with a tap for regulating
f
Box for water. b, Tray. c, Inlet valve.d 3 Regulating valve. e, Small hand wheel.