Principles of naval engineering - Historic Naval Ships Association

Chapter 22. -DIESEL AND GASOLINE ENGINESRING VALVEMECHANISM!SECONDARY ROTOR(RUNNER)RINGVALVESECONDARYROTORRADIALPASSAGERADIALPASSAGEPRIMARY ROTOR ^'(IMPELLER)COVER ORROTOR HOUSING'DRIVENSHAFTROTORHOUSING \\(COVERCOUPLINGHOUSINGRING VALVE-5.33Figure 22-41.— Runner, impeller, and cover ofhydraulic coupling.similar to the one described above, a seriesof piston valves, around the periphery of therotor housing, are normally held in the closedposition by springs. By means of air oil pressureadmitted to the valves, as shown in figure22-43, the pistons are moved axially so as touncover drain ports, allowing the coupling toempty. Where extremely rapid declutching isnot required, the piston-valve coupling offersthe advantages of greater simplicity and lowercost than the ring-valve coupling.Another type of self-contained unit for certaindiesel engine drives is the scoop controlcoupling, shown in figure 22-44. In couplingsof this type, the oil is picked up by one of twoscoop tubes (one tube for each direction ofrotation), mounted on the external manifold.Each scoop tube contains two passages: asmaller one (outermost) handles the normalflow of oil for cooling and lubrication, and alarger one which rapidly transfers oil from thereservior directly to the working circuit.^^RAIN75,260Figure 22-42.— Hydraulic coupling assembly.The scoop tubes are operated from the controlstand through a system of linkages. Asone tube moves outward from the shaft centerlineand into the oil annulus, the other is beingretracted.Four spring-loaded centrifugal valves aremounted on the primary rotor. These valvesare arranged to open progressively as the speedof the primary rotor decreases. The arrangementprovides the necessary oil flow for coolingas it is required. Quick-emptying pistonvalves are provided to give rapid emptying ofthe circuit when the scoop tube is withdrawnfrom contact with the rotating oil annulus.Under normal circulating conditions, oil fedinto the collector ring passes into the pistonvalve control tubes. These tubes and connectingpassages conduct oil to the outer end of thepistons. The centrifugal force of the oil in thecontrol tube holds the piston against the valveport, thus sealing off the circuit. When thescoop tube is withdrawn from the oil annulusin the reservoir, the circulation of oil will be591