Patent GB-601492-A (GB)
Title: Improvements in engine lubricating systems more particularly for aircraft
IPC: F01M5/00
Filed: 1945-10-03
Abstract: 601,492. Lubricating systems for aircraft engines. HOFFMAN, A. C., GEDDES, W. H., and OLCOTT, J. D. Oct. 3, 1945, No. 25716. Convention date, April 30. [Class 12 (iii)] In an engine lubricating system more particularly for aircraft in which provision is made for adding an oil diluent as and when required, the flow to an oil cooler or the byepassing thereof when cold and the return whilst warming-up to an inner compartment or when hot to the main compartment of a reservoir tank, is effected under the control of means responsive to the temperature of the oil, the oil when hot being directed to the main compartment of the tank where it flows as a thin stream over a tortuous path provided by baffle plates to facilitate deaeration and evaporation of the diluent. If a diluent is being added, this acts directly on the thermal element and thereby exercises an over - riding - control to direct the return flow to the inner (warming-up) compartment and so provides a supply of diluted oil in readiness for a subsequent starting from cold. When diluent is thus being added, the oil flow through the cooler, which may have jacket and core sections, is directed so as to give maximum cooling and thereby prevent the viscosity being lowered notwithstanding the addition of diluent. The inner compartment is arranged to provide a subsidiary reservoir of diluted oil which is used for the propeller feathering mechanism. Fig. 1 is a diagrammatic layout of the system, while Fig. 2 shows the oil-circulating tank, Fig. 4 an enlarged view of a valve at the head of the tank with a thermal element for controlling the flow to one or other compartment of the oil-circulating tank, and Fig. 9 the thermal valve arrangements for the byepassing of the oil-cooler. Oil is circulated from a tank 16 to the engine 10, then drained from the sump and returned via an oil cooler 21 back to the tank 16 through a valve chamber 59, whereby the oil, depending on its temperature, is directed either to a small inner circulating compartment 28, Fig. 2, or to the main body of the tank where it is directed from a manifold 39 in a wide thin stream over inclined mesh screens or baffle plates 42, 44 to facilitate the release of air and fuel-oil vapour which rises through a perforated screen 53 and passes away by a vent 55 ; venting pipes 51, 52 are also provided to collect the air and vapour from the undersides of the baffles 42, 44. At starting or near the end of the previous run, fuel oil is admitted to the valve chamber 59 by pipe 87 when a solenoid valve 88 is energized by manual closure of a switch 93. This fuel oil is led through a hollow fixed guide 84 for the sliding sleeve 82 of a duplex valve member 66, 67 so as to flow over the thermal element portion 79 thereof by ports 82a provided in the sleeve 82 and leading to the thermal element portion which has an outer shrouding 85 to shade it from the returning lubricating oil ; the fuel oil leaves the shrouding by ports 96 which in other circumstances allow the returning lubricating oil to contact the thermal element portion. The fuel oil being cold the duplex valve 66, 67 is urged to the left-hand side by a spring 81, since the thermal element 79 is in its contracted condition. Accordingly, valve member 66 closes its port 64 and valve member 67 opens its port 65 whereby the returning lubricating oil (with the diluent fuel oil) is directed to the small inner compartment 28 through a pipe 31 depending into an encircling closed-bottom cylinder 32 with open top. Such returned oil is drawn off through pipe 15 for re-circulation. As this small portion of oil being circulated warms up, the thermal element 79 expands and acting through a rubber or like plug 73 on an abutment stem 76 causes the duplex valve to move over to the right so that intermediately both ports 64, 65 are open, whereby some returning warm oil passes to the main portion of the tank increasing the hydrostatic head therein and reducing that of the inner compartment so that weighted flap valves 48 open to allow passage of oil from the main portion of the tank into the pipe 15 for circulation. The main body of oil has been warmed in the region around the small inner compartment 28 and to facilitate flow of such warmed portion the baffles 42, 44 are made open around such inner chamber. As the oil warms up still further, the yalve member 67 closes the port 65, whereby all the circulating oil is directed to the open port 64. It should be noted that if excessive pressure arises in the valve housing of the circulating tank, the valve element 67 by moving still further to the right will re-open the port 65. A leak port 97, in the valve member 66, allows a small flow of oil or diluent to the main portion of the tank at all times. The fuel oil in the lubricating oil now vaporizes off and passes away by the vent 55. A leak port 98 in a division wall of the valve chamber 59 allows oil to leak to the inner chamber so that there is always a supply of fluid in the closed-bottom cylinder 32 available to be drawn off by pipe 34 and pressure pump 37, Fig. 1, for use in the propeller-feathering mechanism 35. Each operation of the feathering mechanism may be arranged to energize the solenoid valve 88 so that the closed-bottom cylinder 32 is always replenished. When the circulating oil is. cool, the thermal valve 119, Fig. 9, of the cooler closes port 112 and opens port 116 so that the oil passes direct to the outlet passageway 108. As the oil warms up, the port 116 will close and port 112 will open so that the oil is directed to the top header of the cooler. However, until the oil gets hotter, it can still pass direct to the outlet by a thermalvalve port 121. If, however, diluent is being added, then a heater element 124, energized simultaneously with the solenoid valve 88, Fig. 1, admitting the diluent, actuates the thermal valve 122 to close the port 121 so that this circulating fluid is compelled to pass through the cooler. This ensures that the viscosity is prevented from falling too low by the combined effect of warming up and dilution.