Oil system

Abstract

An oil system is provided for use with a rotating machine, for example an aircraft generator and associated transmission. The oil system allows the generator to be run without lubrication for a short period of time. Such a situation is likely to occur when the aircraft is inverted or experiences zero G conditions. The oil system includes an oil reservoir that supplies oil to a first pump for supplying oil for lubricating and/or cooling the generator and for lubricating a variable transmission associated with the generator. The oil reservoir also supplies oil to a second pump that provides oil for operating hydraulic actuators for controlling the operation of the variable transmission. A return path is provided for the oil to the reservoir. The oil system further includes an oil fill inlet such that a single filling operation through the oil fill inlet causes oil to flow through the return path towards the reservoir causing air to be purged through the return path.

I claim:  
     
         1 . An oil management system for a rotating machine capable of being operated in an inverted orientation for a predetermined maximum period of time, the oil system comprising an oil reservoir, a first pump for pumping oil from the oil reservoir to the rotating machine, a gravity drain into a sump and a scavenge pump for returning oil from the sump to the reservoir, wherein the supply of oil to the rotating machine is interrupted when the machine is in its inverted orientation.  
     
     
         2 . An oil management system according to  claim 1 , wherein the interruption of the supply of oil is achieved by placing a supply duct for the first pump in the reservoir at a position where it is not in fluid flow communication with the oil when the machine is inverted or in zero G conditions.  
     
     
         3 . An oil management system according to  claim 2 , wherein said supply duct is located along a wall of the reservoir, said wall comprising a lowermost wall of the reservoir when the machine is in its non-inverted orientation.  
     
     
         4 . An oil management system according to  claim 1 , wherein mechanical means is provided to interrupt said supply of oil.  
     
     
         5 . An oil management system according to  claim 4 , wherein said mechanical means includes one selected from a gravity and an electrically operated valve.  
     
     
         6 . An oil management system according to  claim 1 , wherein a bypass valve redirects an outlet of the first pump to a flow path back to the reservoir when the machine is in its inverted orientation.  
     
     
         7 . An oil management system according to  claim 1 , wherein a second pump is provided in fluid flow connection with the oil reservoir to deliver oil therefrom to actuators forming part of a variable transmission which is part of a drive chain to the rotating machine.  
     
     
         8 . An oil management system according to  claim 7 , wherein an oil flow duct to the second pump extends within the body of the reservoir to a central region thereof such that the duct remains covered by oil irrespective of the orientation of the reservoir.  
     
     
         9 . An oil management system according to  claim 1 , wherein said oil is filtered before being returned to the reservoir.  
     
     
         10 . An oil management system according to  claim 9 , wherein only a single filter is provided.  
     
     
         11 . An oil system for an electrical generator, comprising: 
 an oil reservoir supplying oil to a first pump for supplying oil to the generator and to a variable transmission associated with the generator, said oil reservoir also supplying oil to a second pump for providing oil for operating hydraulic actuators for controlling the operation of the variable transmission; and    a return path for the oil to the reservoir, the system further including an oil fill inlet wherein a single filling operation through the oil fill inlet causes oil to flow through the return path towards the reservoir thereby purging air through an oil cooler and the return path.    
     
     
         12 . An oil system according to  claim 11 , wherein the oil reservoir has an overflow, the height of the overflow being selected such that during a filling operation oil is introduced into the oil fill inlet until such time as oil exits from the reservoir overflow, thereby ensuring that a sufficient amount of oil has been introduced into the system during a filling operation.  
     
     
         13 . An oil system according to  claim 11 , wherein fluid flow paths to external devices connected to said oil system are arranged to ensure that substantially no air is trapped in said external paths during the filling process.  
     
     
         14 . An oil system according to  claim 13 , wherein said fluid flow paths include one or more bypass fluids around said external devices, each said bypass route being either open, or forced to be open, during a said filling process, thereby allowing air to be purged from said fluid flow paths.