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A variable displacement pump and pump control system therefor to pump a fluid at selected pump output flow rates having a variable displacement pump and a fluid volume displacement selection controller to select a volume of fluid to be forced from the pump inlet to the pump outlet by the rotating me

A variable displacement pump and pump control system therefor to pump a fluid at selected pump output flow rates having a variable displacement pump and a fluid volume displacement selection controller to select a volume of fluid to be forced from the pump inlet to the pump outlet by the rotating member during a rotation thereof. A movable lead screw is coupled to the displacement selection controller so as to be capable of altering the position thereof, and a lead screw positioner is provided for selectively moving, or preventing the moving of, the movable lead screw by extending and retracting the lead screw through a threaded opening.

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1. A variable displacement pump and pump control system therefor to pump a fluid at selected pump output flow rates in a range of pump output flow rates, the system comprising: a variable displacement pump having a rotor shaft with which to rotate a pump rotating member about an axis of rotation to

1. A variable displacement pump and pump control system therefor to pump a fluid at selected pump output flow rates in a range of pump output flow rates, the system comprising: a variable displacement pump having a rotor shaft with which to rotate a pump rotating member about an axis of rotation to force fluid that has entered a pump inlet to a pump outlet, and a fluid volume displacement selection controller to select a volume of fluid to be forced from the pump inlet to the pump outlet by the rotating member during a rotation thereof,a movable lead screw coupled to directly transmit force to the displacement selection controller so as to alter the position thereof as a result of selected motion of the movable lead screw, anda lead screw positioner for selectively moving, or preventing the moving of, the movable lead screw by extending and retracting the movable lead screw through a threaded opening, wherein the lead screw positioner comprises an electrically powered motor, and wherein the lead screw positioner extends and retracts the movable lead screw by rotating the movable lead screw. 2. The system of claim 1 further comprising a position return force arrangement coupled to the displacement selection controller so as to tend to return the displacement selection controller to at least one position from which it was altered by motion of the movable lead screw. 3. The system of claim 2 wherein the position return force arrangement returns the displacement selection controller to at least one position from which it was altered by motion of the movable lead screw if the lead screw positioner is neither moving nor preventing the moving of the movable lead screw. 4. The system of claim 3 wherein the returning by the position return force arrangement of the displacement selection controller to at least one position from which it was altered by motion of the movable lead screw increases the volume of fluid to be forced to the pump outlet by the rotating member during a rotation thereof. 5. The system of claim 3 wherein the returning by the position return force arrangement of the displacement selection controller to at least one position from which it was altered by motion of the movable lead screw decreases the volume of fluid to be forced to the pump outlet by the rotating member during a rotation thereof. 6. The system of claim 2 wherein the position return force arrangement does not return the displacement selection controller to at least one position from which it was altered by motion of the movable lead screw if the lead screw positioner is neither moving nor preventing the moving of the movable lead screw. 7. The system of claim 1 wherein the electrically powered motor has an output shaft and drives the output shaft to rotate at a selected rotation rate. 8. The system of claim 7 wherein the motor output shaft also comprises the movable lead screw. 9. The system of claim 7 wherein the motor output shaft is coupled to the movable lead screw. 10. The system of claim 9 wherein the motor output shaft is coupled to the movable lead screw through a gear set. 11. The system of claim 1 wherein the displacement selection controller is a movable structure in the variable displacement pump with movements thereof changing the volume of fluid forced to the pump outlet by the rotating member during a rotation thereof. 12. The system of claim 11 wherein the variable displacement pump is a vane pump. 13. The system of claim 12 wherein the displacement selection controller in the vane pump comprises a movable cam ring surrounding the pump rotating member with a ring portion axis of symmetry substantially parallel to the axis of rotation but offset therefrom. 14. The system of claim 13 wherein the cam ring is pivotable about a pivot axis substantially parallel to the ring portion axis of symmetry but located adjacent to a part of the ring portion. 15. The system of claim 12 wherein the displacement selection controller comprises a cam ring which is slidable in a direction substantially perpendicular to the ring portion axis of symmetry. 16. The system of claim 1 further comprising an electric motor coupled to the rotor shaft. 17. A variable displacement pump and pump control system therefor provided in an aircraft to pump a fuel to a gas turbine engine at selected pump output fuel flow rates in a range of pump output fuel flow rates, the system comprising: a variable displacement pump having a rotor shaft coupled to a gearbox coupled in turn to the gas turbine engine with which to rotate a pump rotating member about an axis of rotation to force fluid that has entered a pump inlet to a pump outlet,and a fluid volume displacement selection controller to select a volume of fluid to be forced from the pump inlet to the pump outlet by the rotating member during a rotation thereof,a movable lead screw coupled to directly transmit force to the displacement selection controller so as to alter the position thereof as a result of selected motion of the movable lead screw, anda lead screw positioner for selectively moving, or preventing the moving of, the movable lead screw by extending and retracting the movable lead screw through a threaded opening, wherein the lead screw positioner comprises an electrically powered motor, and wherein the lead screw positioner extends and retracts the movable lead screw by rotating the movable lead screw. 18. The system of claim 17 further comprising a position return force arrangement coupled to the displacement selection controller so as to tend to return the displacement selection controller to at least one position from which from which it was altered by motion of the movable lead screw. 19. The system of claim 18 wherein the position return force arrangement returns the displacement selection controller to at least one position from which it was altered by motion of the movable lead screw if the lead screw positioner is neither moving nor preventing the moving of the movable lead screw, thus decreasing the volume of fluid to be forced to the pump outlet by the rotating member during a rotation thereof. 20. The system of claim 18 wherein the electrically powered motor has an output shaft and drives the output shaft to rotate at a selected rotation rate.