Variable output fluid pump system

Abstract

A variable output pump system is provided, the pump system having a first positive displacement pump; a pump drive operably coupled to the first positive displacement pump, wherein the pump drive operates the first positive displacement pump to have a first output profile during a first operating range and a second output profile during a second operating range, the pump drive having a hydraulic release being configured to decrease the second output profile as a hydraulic pressure increases.

1 . A pump system comprising:
 a first positive displacement pump;   a pump drive operably coupled to the first positive displacement pump, wherein the pump drive operates the first positive displacement pump to have a first output profile during a first operating range and a second output profile during a second operating range, the pump drive having a hydraulic release being configured to decrease the second output profile as a hydraulic pressure increases.   
     
     
         2 . The pump system as in  claim 1 , wherein the hydraulic release comprises:
 a fluid cavity in fluid communication with a fluid being pumped by the pump system, the fluid cavity having a surface continuously movable between a first position and a second position in response to a change in a pressure of the fluid; and   a movable first engagement member operably coupled to the movable surface;   a movable second engagement member operably associated with the first engagement member, the first engagement member and the second engagement member cooperating to decease a pump system flow output in the second operating range as the moveable surface moves from the first position to the second position.   
     
     
         3 . The pump system as in  claim 2 , further comprising a biasing member for biasing the movable surface towards the first position. 
     
     
         4 . The pump system as in  claim 3 , wherein the biasing member biases the first engagement member to increase a contact pressure between the first engagement member and the second engagement member. 
     
     
         5 . The pump system as in  claim 4 , wherein the first engagement member includes a first contact surface having a plurality of first features and the second engagement member includes a second contact surface having a plurality of second features; the second contact surface is adjacent the first contact surface;
 a lubricant transfer path defined by the plurality of first features and the plurality of second features, the lubricant transfer path being noncontiguous during portions less than all of relative angular displacement between the first engagement member and the second engagement member.   
     
     
         6 . The pump system as in  claim 5 , wherein the plurality of first features are a plurality of first openings and the plurality of second features are a plurality of second openings and the first contact surface is in frictional contact with the second contact surface through viscous fluid shear forces in the fluid. 
     
     
         7 . The pump system as in  claim 6 , wherein the viscous fluid shear forces decrease with increase of the fluid pressure during the second operating range. 
     
     
         8 . The pump system as in  claim 5 , further comprising:
 a second positive displacement pump fluidly coupled in parallel with the first positive displacement pump, the second positive displacement pump having a third output profile;   wherein a flow output of the pump system in the second operating range is substantially equal to the sum of the second output profile and the third output profile.   
     
     
         9 . A method for varying the output of a pump system, comprising:
 driving a contact surface coupled to a first pump of the pump system with a pressure-regulated slip drive by rotating an engagement surface of the pressure-regulated slip drive in a first direction about an axis, wherein viscous shear of a fluid disposed between the engagement surface and the contact surface couples the engagement surface to the contact surface; and   decreasing an output of the first pump by moving the engagement surface away from the contact surface as a pressure of a fluid pumped by the pump system moves a moveable load control member coupled to the engagement surface.   
     
     
         10 . The method as in  claim 9 , wherein the engagement surface is biased towards the contact surface by a biasing member. 
     
     
         11 . The method as in  claim 10 , wherein the engagement surface is in physical contact with the contact surface when the pressure of the fluid pumped by the pump system is below a predetermined pressure. 
     
     
         12 . The method as in  claim 9 , wherein the pump system further comprises a direct drive pump and wherein the first pump and the direct drive pump provide parallel output and as the pressure of the fluid pumped by the pump system moves the moveable load control member a predetermined distance. 
     
     
         13 . The method as in  claim 12 , wherein viscous shear of the fluid disposed between the engagement surface and the contact surface prevents the engagement surface from being rotated in a direction opposite to the first direction by a hydraulic pressure acting on the first pump. 
     
     
         14 . The method as in  claim 9 , wherein a plurality of features in the engagement surface and the contact surface define at least one non-contiguous lubricant pathway from an inner opening of either the engagement surface or the contact surface towards an outer periphery of the engagement surface or the contact surface. 
     
     
         15 . The method as in  claim 14 , wherein rotation of either the engagement surface or the contact surface relative to each other causes another non-contiguous lubricant pathway to be formed between the inner opening of either the engagement surface or the contact surface and an outer periphery of the engagement surface or the contact surface and the plurality of features includes voids in the engagement surface or the contact surface and wherein the rotation of either the engagement surface or the contact surface relative to each other eliminates the non-contiguousness of the lubricant pathway. 
     
     
         16 . A variable output pump system, comprising:
 a positive displacement pump; and   means for varying the output of the positive displacement pump by varying a pressure of a fluid in a fluid cavity of a hydraulically released slip drive drivingly coupled to at least one component of the positive displacement pump.   
     
     
         17 . The variable output pump system as in  claim 16 , wherein the means for varying the output of the positive displacement pump includes fluid pumped by the positive displacement pump and the fluid drives the positive displacement pump by creating frictional engagement between at least two facing spaced surfaces of the hydraulically released slip drive. 
     
     
         18 . The variable output pump system as in  claim 16 , wherein a torque applied to the positive displacement pump by the hydraulically released slip drive is provided by viscous shear of two facing surfaces, in a spaced relationship, of the hydraulically released slip drive when fluid in the fluid cavity is at a first pressure and the torque is also provided by Coulomb friction between the two facing surfaces when the fluid is at a second pressure, the second pressure being less than the first pressure. 
     
     
         19 . The variable output pump system as in  claim 18 , wherein the two facing surfaces further comprise voids in contact surfaces of the facing surfaces, the voids being arranged to form lubricant transfer paths, the lubricant transfer paths being intermittently non-continuous during relative angular displacement of the facing surfaces with respect to each other, wherein at least one lubricant transfer path moves from being entirely on a first contact surface of one of the facing surfaces to being entirely on a second side of the one of the facing surfaces, the second side being opposite the first contact surface.