in motor trucks. Friction clutches may be single-cone ordouble-cone. Figure 11-25, D, shows a disc clutch, alsoused in autos. A disc clutch also may have several plates(multiple-disc clutch). In a series of discs, each drivendisc is located between two driving discs. You may havehad experience with a multiple-disc clutch on your car.The Hele-Shaw clutch is a combined conical-discclutch (fig. 11-25, E). Its groove permits cooling andcirculation of oil. Single-disc clutches are frequently dryclutches (no lubrication); multiple-disc clutches may bedry or wet (either lubricated or operated with oil).Magnetic clutches are a recent development inwhich the friction surfaces are brought together bymagnetic force when the electricity is turned on (fig.11-25, F). The induction clutch transmits power withoutcontact between the driving and driven parts.The way pressure is applied to the rim block, splitring, band, or roller determines the names of expandingclutches or rim clutches. In one type of expandingclutch, right- and left-hand screws expand as a slidingsleeve moves along a shaft and expands the band againstthe rim. The centrifugal clutch is a special applicationof a block clutch.Machines containing heavy parts to be moved, suchas a rolling mill, use oil clutches. The grip of the coilcauses great friction when it is thrust onto a cone on thedriving shaft. Yet the clutch is very sensitive to control.Diesel engines and transportation equipment usepneumatic and hydraulic clutches. Hydraulic couplings(fig, 11-25, G), which also serve as clutches, are used inthe hydraulic A-end of electric-hydraulic gun drives.SUMMARYIn this chapter we discussed the following elementsand mechanisms used in naval machinery:Two types of bearings are used in naval machinery:sliding and antifrictional.Springs are another element used in machinery.Springs can be twisted, pulled, or stretched byforce and can return to their original shape whenthe force is released.One basic mechanism of machines is the geardifferential. A gear differential is a mechanismthat is capable of adding and subtractingmechanically. Other basic mechanisms includelinkages, couplings, cams and cam followers,and clutches.11-15
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