Variable output control for a fixed displacement pump

Abstract

A device for adjusting the volume of fluid flow produced by a stroke of a piston pump includes a cylinder communicating with an outlet of the pump. A plunger displaces fluid from the cylinder to the outlet as the plunger moves in the cylinder. A lost motion piston moves in the cylinder. A fluid source supplies fluid to a first space in the cylinder located between the plunger and the piston. A port, through which fluid is supplied from the fluid source to a second space in the cylinder, is located above the piston such that the port is opened and closed by the piston. A stop establishes a maximum distance that the piston can move away from plunger toward the port without closing the port.

1 . Apparatus for adjusting the volume of fluid flow produced by a stroke of a piston pump, establishing the volume of fluid flow produced by a stroke of a fluid pump, comprising: 
 a cylinder communicating with an outlet of the pump;    a plunger for displacing fluid from the cylinder to the outlet as the plunger moves in the cylinder;    a piston moveable in the cylinder;    a fluid source for supplying fluid to the cylinder between the plunger and the piston;    a port communicating with the cylinder and fluid source, opened and closed by the piston; and    a stop for establishing a maximum distance that the piston can move away from plunger toward the port without closing the port.    
   
   
       2 . The apparatus of  claim 1 , further comprising: 
 a first check valve for alternately opening and closing communication between the fluid source and the cylinder; and    a second check valve for alternately opening and closing communication between the cylinder and the outlet.    
   
   
       3 . The apparatus of  claim 1 , further comprising: 
 a first check valve for alternately opening and closing communication between the fluid source and the cylinder;    a second check valve for alternately opening and closing communication between the outlet and the cylinder;    wherein the first check valve opens and closes in response to differential pressure across the first check valve; and    the second check valve opens and closes in response to differential pressure across second check valve.    
   
   
       4 . The apparatus of  claim 1 , wherein the cylinder includes a head that closes the second against entry and exit of fluid except through the port.  
   
   
       5 . The apparatus of  claim 1 , further comprising: 
 an actuator for changing the location of the stop, thereby adjusting a distance that the piston can move away from the port.    
   
   
       6 . The apparatus of  claim 1 , further comprising: 
 an actuator for changing the location of the stop, thereby adjusting a distance that the piston can move in the cylinder before closing the port.    
   
   
       7 . The apparatus of  claim 1 , wherein the second space has a length along the cylinder ort is closed that varies as the piston moves in the cylinder.  
   
   
       8 . The apparatus of  claim 1 , wherein the stop limits the distance that the piston can from the port toward the plunger.  
   
   
       9 . Apparatus for adjusting the volume of fluid flow produced by a stroke of a piston pump, comprising: 
 a cylinder communicating with an outlet of the pump, including an axial end closed by a head;    a plunger for displacing fluid from the cylinder to the outlet as the plunger moves in the cylinder;    a piston moveable in the cylinder;    a fluid source for supplying fluid to the cylinder between the plunger and the piston;    a port communicating with the cylinder, opened and closed by the piston; and    a stop located for contact with the piston for limiting movement of the piston toward the plunger, and establishing a distance that the piston can move away from plunger toward the port without closing the port.    
   
   
       10 . The system of  claim 9 , further comprising: 
 an engine for producing linear reciprocating output, said engine output being driveably connected to the plunger.    
   
   
       11 . The system of  claim 9 , further comprising: 
 a free piston engine producing linear reciprocating output, said engine output being driveably connected to the plunger.    
   
   
       12 . The system of  claim 9 , wherein the piston is moves in the cylinder in response to differential pressure across the piston.  
   
   
       13 . The apparatus of  claim 9 , further comprising: 
 a first check valve for alternately opening and closing communication between the fluid source and the cylinder; and    a second check valve for alternately opening and closing communication between the cylinder and the outlet.    
   
   
       14 . The apparatus of  claim 9 , further comprising: 
 a first check valve for alternately opening and closing communication between the fluid source and the cylinder;    a second check valve for alternately opening and closing communication between the cylinder and the outlet;    wherein the first check valve opens and closes in response to differential pressure across the first check valve; and    the second check valve opens and closes in response to differential pressure across second check valve.    
   
   
       15 . The apparatus of  claim 9 , wherein the cylinder includes a head that closes the second against entry and exit of fluid except through the port.  
   
   
       16 . The apparatus of  claim 9 , further comprising: 
 an actuator for changing the location of the stop, thereby adjusting a distance that the piston can move away from the port.    
   
   
       17 . The apparatus of  claim 9 , further comprising: 
 an actuator for changing the location of the stop, thereby adjusting a distance that the piston can move in the cylinder before closing the port.    
   
   
       18 . The apparatus of  claim 9 , wherein the second space has a length along the cylinder ort is closed that varies as the piston moves in the cylinder.  
   
   
       19 . The apparatus of  claim 9 , wherein the stop limits the distance that the piston can from the port toward the plunger.  
   
   
       20 . A method for adjusting a portion of the stroke of a piston pump that is effective in displacing fluid from the pump, comprising the steps of: 
 providing a cylinder supplied with fluid, and a plunger displaceable in the cylinder for pumping fluid from the cylinder;    providing a spill port communicating with the cylinder;    locating a piston at a first position in the cylinder between the spill port and the plunger, the piston being displaceable in response to displacement of the plunger;    establishing a length of piston displacement between the first position and a second position where the piston closes the spill port; and    displacing the plunger in the cylinder.    
   
   
       21 . The method of  claim 21 , further comprising the step of adjusting the length of piston displacement between the first position and a second position.  
   
   
       22 . The method of  claim 21 , further comprising the step of: 
 providing a stop contacted by the piston for limiting said length of piston displacement.    
   
   
       23 . The method of  claim 21 , further comprising the steps of; 
 providing a stop contacted by the piston for limiting said length of piston displacement; and    adjusting said length of piston displacement between the first position and a second position.