PRINCIPLES OF NAVAL ENGINEERING 



REDUCTION GEAR OIL COOLER REDUCTION GEAR OIL COOLER 



PORT REDUCTION GEAR 



STARBOARD REDUCTION GEAR 



75.258 



Figure 22-40.— Schematic diagram of reverse gear lubrication system. 



When the coupling is assembled, the two 

 rotors are placed facing each other to complete 

 the doughnut (fig. 22-42). The rotors do not quite 

 touch each other, the clearance between them 

 being 1/4 to 5/8 inch, depending on the size of 

 the coupling. The curved radial passages of the 

 two rotors are opposite each other, so that the 

 outer passages combine to make a circular 

 passage except for the small gaps between the 

 rotors. 



In the hydraulic coupling assembly, shown in 

 figure 22-42, the driving shaft is secured to the 

 engine crankshaft and the driven shaft goes to 

 the reduction gear box. The oil inlet admits oil 

 directly to the rotor cavities, which become 

 completely filled. The rotor housing is bolted 

 to the secondary rotor and has an oil-sealed 



joint with the driving shaft. A ring valve, 

 going entirely around the rotor housing, can be 

 operated by the ring valve mechanism to open 

 or close a series of emptying holes (fig. 22-42) 

 housing. When the ring valve is opened, the oil 

 will fly out from the rotor housing into the 

 coupling housing, draining the coupling com- 

 pletely in two or three seconds. Even when the 

 ring valve is closed, some oil leaks out into 

 the coupling housing, and additional oil enters 

 through the inlet. From the coupling housing, 

 the oil is drawn by a pump to a cooler, then 

 sent back to the coupling. 



Another coupling assembly used on several 

 Navy ships is the hydraulic couplingwithpiston- 

 type quick-dumping valves, .shown in figure 22- 

 43. In this coupling, in which the operation is 



590 



