Ultra High Pressure Pump With An Alternating Rotation To Linear Displacement Drive Mechanism

Abstract

A high pressure pump including a linear actuator comprising a servo motor to axially rotate a hollow rotor shaft in alternating directions, the servo motor having a stator positioned co-axially around the hollow rotor shaft with an interior of the rotor shaft being co-axially coupled to a drive member to convert axial rotation into reciprocal displacement, the drive member being constrained against linear movement and supporting a shaft. At least one piston is coupled to the shaft and the piston is arranged within a cylinder to define a pumping chamber, whereby alternating rotation of the rotor shaft causes reciprocal linear displacement of the piston to pressurize fluid in the pumping chamber. A drive mechanism includes a controller coupled to a servomotor and an encoder to measure movement of the hollow rotor or output shaft and send a feedback signal proportional to the movement to the controller.

1 - 18 . (canceled) 
     
     
         19 . An ultra high pressure pump, comprising:
 a motor adapted to axially rotate a hollow rotor shaft in alternating directions, the motor having a stator positioned co-axially around the hollow rotor shaft with the interior of the rotor shaft being co-axially coupled to drive means to convert axial rotation into reciprocal displacement, the motor including an encoder to monitor movement of at least one of the rotor shaft and drive means, the drive means being coupled to at least one piston having a head arranged within a cylinder to define a pumping chamber between the head of the piston and the cylinder, whereby alternating rotation of the rotor shaft causes reciprocal linear displacement of the piston to pressurize fluid in the pumping chamber to pressures greater than 50,000 psi.   
     
     
         20 . The ultra high pressure pump of  claim 19 , wherein the encoder is coupled to the motor via a closed feedback loop. 
     
     
         21 . The ultra high pressure pump of  claim 19 , wherein the encoder transmits at least one of a velocity feedback signal and a position feedback signal. 
     
     
         22 . The ultra high pressure pump of  claim 19 , wherein the stator is located within a cylindrical housing. 
     
     
         23 . The ultra high pressure pump of  claim 21 , wherein the cylindrical housing is encased in a water cooled jacket. 
     
     
         24 . The ultra high pressure pump of  claim 23 , wherein the cylindrical housing, cooling jacket, stator, rotor, drive means and shaft are all coaxial. 
     
     
         25 . The ultra high pressure pump of  claim 19 , wherein the drive means comprises a linearly fixed nut that is in direct engagement with the rotor shaft, the nut threadedly engaging a screw whereby axial rotation of the rotor shaft, and therefore the nut, imparts linear motion to the screw. 
     
     
         26 . The ultra high pressure pump of  claim 25 , wherein the screw is supported by linear bearings each supported on elongate rails. 
     
     
         27 . The ultra high pressure of  claim 26 , wherein the bearings prevent rotation of the screw while facilitating longitudinal movement of the screw. 
     
     
         28 . The ultra high pressure pump of  claim 26 , wherein one end of the screw has opposed flats that engage the linear bearings. 
     
     
         29 . The ultra high pressure pump of  claim 25 , wherein pistons are coupled to opposite ends of the screw, each piston being adapted to complete reciprocal motion within an associated cylinder thus defined two pumping chambers. 
     
     
         30 . The ultra high pressure pump of  claim 29 , wherein each cylinder has a low pressure water inlet controlled by a low pressure check valve and a high pressure outlet controlled by a high pressure check valve. 
     
     
         31 . The ultra high pressure pump of  claim 30 , wherein high pressure seals are positioned between the inner ends of the pistons and the cylinders. 
     
     
         32 . The ultra high pressure pump of  claim 31 , wherein each piston has a stroke of about 175 mm and reciprocates at about 120 strokes per minute to deliver between 2 and 4 litres of fluid per minute. 
     
     
         33 . A pump assembly for a waterjet cutting apparatus, comprising two pumps of claim  1  coupled together to produce an ultra-high pressure jet of water, the reciprocation of the pumps being out of phase to reduce pulsing of the water pressure. 
     
     
         34 . The pump assembly of  claim 33 , wherein the speed of one pump is greater than the speed of the other pump to compensate for the other pump while reversing.