Positive displacement pump system

Abstract

A positive displacement pump system comprises: a first positive displacement pump comprising a rotatable element; a second positive displacement pump comprising a rotatable element; and an electric motor comprising a stator and a rotor. The rotor is coupled to the rotatable elements of the first and second positive displacement pumps to provide drive thereto. The rotor is supported for rotation by the rotatable elements of the first and second positive displacement pumps. The rotatable elements of the first positive displacement pump and the second positive displacement pump each comprise pump shafts which are coupled to a rotor shaft of the rotor.

We claim: 
     
         1 . A positive displacement pump system comprising:
 a first positive displacement pump comprising a rotatable element;   a second positive displacement pump comprising a rotatable element; and   an electric motor comprising a stator and a rotor, the rotor being coupled to the rotatable elements of the first positive displacement pump and the second positive displacement pump to provide drive thereto;   wherein the rotor is supported for rotation by the rotatable elements of the first positive displacement pump and the second positive displacement pump; and   wherein the rotatable elements of the first positive displacement pump and the second positive displacement pump each comprise pump shafts which are coupled to a rotor shaft of the rotor.   
     
     
         2 . The positive displacement pump system of  claim 1 , wherein the electric motor is supported solely by the rotatable elements of the first positive displacement pump and the second positive displacement pump. 
     
     
         3 . The positive displacement pump system of  claim 1 , wherein the pump shafts and the rotor shaft are connected by respective intermediate drive shafts extending therebetween. 
     
     
         4 . The positive displacement pump system of  claim 3 , wherein the pump shafts and the rotor shaft are hollow and the intermediate drive shaft is received within the pump shafts and the rotor shaft. 
     
     
         5 . The positive displacement pump system of  claim 3 , wherein the intermediate drive shaft is connected with the pump shafts and the rotor shaft by splined connections. 
     
     
         6 . The positive displacement pump system of  claim 1 , wherein the pump shafts and the rotor shaft are connected by an external coupling. 
     
     
         7 . The positive displacement pump system of  claim 6 , wherein the external coupling is a flexible coupling. 
     
     
         8 . The positive displacement pump system of  claim 1 , wherein each pump shaft is supported by a respective pair of bearing blocks. 
     
     
         9 . The positive displacement pump system of  claim 8 , wherein one of each pair of bearing blocks further supports the rotor shaft. 
     
     
         10 . The positive displacement pump system of  claim 9 , wherein said one of each pair of bearing blocks comprises an extension portion which supports the rotor shaft. 
     
     
         11 . The positive displacement pump system of  claim 1 , wherein the first positive displacement pump, the second positive displacement pump and the electric motor are disposed within a common housing. 
     
     
         12 . The positive displacement pump system of  claim 11 , wherein the electric motor is at least partially immersed in a pumped liquid. 
     
     
         13 . The positive displacement pump system of  claim 1 , wherein at least one or both of the first positive displacement pump or the second positive displacement pump is a gear pump and the rotating element is a first gear of the gear pump, the gear pump further comprising a second gear which meshes with and is driven by the first gear. 
     
     
         14 . A gas turbine engine including a positive displacement pump system of  claim 1 . 
     
     
         15 . The gas turbine engine of  claim 14 , wherein the positive displacement pump system is part of a fuel or oil supply system.