DETAILS of screw engines.

279

and surface to produce a perfect contact for thewhole. Now with a deep ring, or a singlesurface in contact, a proportionate amount ofpower is requisite to keep the ring to its work;but when the surface is subdivided—or a seriesof shallow rings—the effect is more practicallyproduced, simply because the power is dividedalso. This class of piston has met with muchfavour for locomotives, and is becoming morem use for marine purposes than was onceanticipated.

Mechanical means for the adjustment of

THE GLANDS OF STUFFING BOXES.

When the packing around the trunk ofan engine requires to be tightened, the glandMiust be shifted; and to do this effectually eachMut should be simultaneously turned. NowWith separate manipulation—'the general prac-tice—this is a tedious as well as a dangerous

Fig. 124.

b urgh’s pinion and wheel motion for adjustingtrunk glands.

operation when the engine is in motion. To°b\iate these evils, we have designed the

arrangement of pinion and wheel motion asshown by Fig. 124. This is a double-toothedring, the inner teeth being in gear with pinions,which are virtually nuts screwed on as manystuds. The outside teeth of the ring are ingear with a spur pinion, and this latter ismitred at its extremity, a second mitre pinionimparting motion when required. The actionis therefore as follows—the perpendicular rodis prolonged to the top of the platform orcylinder, surmounted with a cranked handle;on imparting motion to the mitred pinions,

Fig. 125.

WORM AND PINION MOTION FOR ADJUSTING PISTON ROD

GLANDS.

the spur pinion causes the ring to revolve,when each screw pinion acts against the