Pump with variable stroke piston

Abstract

A pump apparatus includes a housing located on an axis. The housing has a chamber, an inlet valve and an outlet valve. A piston driver is configured to axially reciprocate. A piston is a piston configured to reciprocate in the chamber to draw liquid into the chamber through the inlet valve during an intake stroke and to discharge the liquid out of the chamber through the outlet valve during a delivery stroke. A spring axially biases the piston to a base position relative to the driver, so that the driver, when reciprocating, will drive the piston to reciprocate. A preload structure preloads the spring to enable pressure of the liquid in the chamber to displace the piston away from the base position against the spring bias after the pressure exceeds a threshold level.

1 . A pump apparatus comprising: 
 a housing located on an axis and having a chamber, an inlet valve and an outlet valve;    a piston driver configured to axially reciprocate;    a piston configured to reciprocate in the chamber to draw liquid into the chamber through the inlet valve during an intake stroke and to discharge the liquid out of the chamber through the outlet valve during a delivery stroke;    a spring that axially biases the piston to a base position relative to the driver, so that the driver, when reciprocating, will drive the piston to axially reciprocate; and    a preload structure that preloads the spring to enable pressure of the liquid in the chamber to displace the piston away from the base position against the spring bias after the pressure exceeds a threshold level.    
   
   
       2 . The apparatus of  claim 1  wherein the spring has a spring constant that increases with increasing compression of the spring.  
   
   
       3 . The apparatus of  claim 1  wherein the spring is configured to render the volume of liquid delivered during each delivery stroke inversely related to output pressure of the pump.  
   
   
       4 . The apparatus of  claim 3  wherein the spring is configured to render the volume of liquid delivered during each delivery stroke inversely proportional to the output pressure.  
   
   
       5 . The apparatus of  claim 1  wherein the preload is manually adjustable.  
   
   
       6 . The apparatus of  claim 5  wherein manual adjustment of the preload adjusts the depth of the piston in the chamber.  
   
   
       7 . The apparatus of  claim 1  wherein the spring is a bias spring, and the apparatus further comprises a return spring having a lower spring constant than the bias spring urging the piston out of the chamber.  
   
   
       8 . The apparatus of  claim 1  wherein the preload structure includes a protrusion on the piston that is located in the driver and is axially urged by the spring against a stop surface of the driver.  
   
   
       9 . The apparatus of  claim 8  wherein the stop surface is between the rod protrusion and the spring.  
   
   
       10 . The apparatus of  claim 1  wherein the spring is configured to absorb the entire reciprocation stroke of the driver in a case where liquid is blocked from exiting the outlet valve piston while the driver continues to reciprocate.  
   
   
       11 . The apparatus of  claim 1  further comprising an inlet hose connected to a water source.  
   
   
       12 . A pump apparatus comprising: 
 a housing located on an axis and having a chamber, an inlet valve and an outlet valve;    a piston driver configured to axially reciprocate;    a piston configured to reciprocate in the chamber to draw liquid into the chamber through the inlet valve during an intake stroke and to discharge the liquid out of the chamber through the outlet valve during a delivery stroke; and    a spring that axially biases the piston to a base position relative to the driver, so that the driver, when reciprocating, will drive the piston to axially reciprocate while enabling pressure of the liquid in the chamber to displace the piston away from the base position against the spring bias, the spring having a spring constant that increases with increasing compression of the spring.    
   
   
       13 . The apparatus of  claim 12  wherein the spring includes coil springs with different spring constants.  
   
   
       14 . A pump apparatus comprising: 
 a housing located on an axis and having a chamber, an inlet valve and an outlet valve;    a piston driver configured to axially reciprocate;    a piston configured to reciprocate in the chamber to draw liquid into the chamber through the inlet valve during an intake stroke and to discharge the liquid out of the chamber through the outlet valve during a delivery stroke;    a spring that axially biases the piston to a base position relative to the driver, so that the driver, when reciprocating, will drive the piston to axially reciprocate while enabling pressure of the liquid in the chamber to displace the piston away from the base position against the spring bias; and    an inlet hose connected to the inlet valve and configured to be connected to a liquid source.    
   
   
       15 . The apparatus of  claim 14  wherein the inlet hose has a threaded end configured to be screwed onto a water faucet.  
   
   
       16 . A pump apparatus comprising: 
 a housing located on an axis and having a chamber, an inlet valve and an outlet valve;    a piston driver configured to axially reciprocate;    a piston configured to reciprocate in the chamber to draw liquid into the chamber through the inlet valve during an intake stroke and to discharge the liquid out of the chamber through the outlet valve during a delivery stroke; and    a spring that axially biases the piston to a base position relative to the driver, so that the driver, when reciprocating, will drive the piston to axially reciprocate while enabling pressure of the liquid in the chamber to displace the piston away from the base position against the spring bias, the spring being configured render the volume of liquid delivered during each delivery stroke inversely related to output pressure of the pump.    
   
   
       17 . The apparatus of  claim 16  wherein the delivery stroke volume is approximately inversely proportional to output pressure of the pump.  
   
   
       18 . A pump apparatus comprising: 
 a housing located on an axis and having a chamber, an inlet valve and an outlet valve;    a piston driver configured to axially reciprocate;    a piston configured to reciprocate in the chamber to draw liquid into the chamber through the inlet valve during an intake stroke and to discharge the liquid out of the chamber through the outlet valve during a delivery stroke; and    a spring that axially biases the piston to a base position relative to the driver, so that the driver, when reciprocating, will drive the piston to axially reciprocate while enabling pressure of the liquid in the chamber to displace the piston away from the base position against the spring bias, the spring being configured to absorb the entire reciprocation stroke of the driver in a situation where the liquid is blocked from exiting the outlet valve while the driver continues to reciprocate.