Figure 11-15.-Sleeve coupling.pivot, and the two links connect at two points in differentdirections from the pivot. By properly locating theconnection points, the output links can move in anydesired direction.All linkages require occasional adjustments orrepair, particularly when they become worn. To makethe proper adjustments, a person must be familiar withthe basic parts that constitute a linkage. Adjustments arenormally made by lengthening or shortening the rodsand shafts by a clevis or turnbuckle.COUPLINGSThe term coupling applies to any device that holdstwo parts together. Line shafts that make up severalshafts of different lengths may be held together by anyof several types of shaft couplings.SLEEVE COUPLINGYou may use the sleeve coupling (fig. 11-15) whenshafts are closely aligned. It consists of a metal tube slitat each end. The slitted ends enable the clamps to fastenthe sleeve securely to the shaft ends. With the clampstightened, the shafts are held firmly together and turn asone shaft. The sleeve coupling also serves as aconvenient device for making adjustments betweenunits. The weight at the opposite end of the clamp fromthe screw merely offsets the weight of the screw andclamp arms. Distributing the weight evenly reduces theshaft vibration.OLDHAM COUPLINGThe Oldham coupling, named for its inventor,transmits rotary motion between shafts that are parallelbut not always in perfect alignment.Figure 11-16.-Oldham coupling.An Oldham coupling (fig. 11-16) consists of a pairof disks, one flat and the other hollow. These disks arepinned to the ends of the shafts. A third (center) disk,with a pair of lugs projecting from each face of the disk,fits into the slots between the two end disks and enablesone shaft to drive the other shaft. A coil spring, housedwithin the center of the hollow end disk, forces thecenter disk against the flat disk. When the coupling isassembled on the shaft ends, a flat lock spring is slippedinto the space around the coil spring. The ends of the flatspring are formed so that when they are pushed into theproper place, the ends of the spring push out and lockaround the lugs. A lock wire is passed between the holesdrilled through the projecting lugs to guard theassembly. The coil spring compensates for any changein shaft length. (Changes in temperature may cause theshaft length to vary.)The disks, or rings, connecting the shafts allow asmall amount of radial play. This play allows a smallamount of misalignment of the shafts as they rotate. Youcan easily connect and disconnect the Oldham typecouplings to realign the shafts.OTHER TYPES OF COUPLINGSWe use four other types of couplings extensively innaval equipment:1. The fixed (sliding lug) coupling, which isnonadjustable; it does allow for a small amount ofmisalignment in shafting (fig. 11-17).2. The flexible coupling (fig. 11-18), whichconnects two shafts by a metal disk. Two coupling hubs,11-10
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