Ultra high pressure pump

An ultra high pressure pump comprising a servo motor adapted 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 the interior of the rotor shaft being co-axially coupled to drive means to convert axial rotation into reciprocal displacement, the drive means having opposed ends, each end coupled to a 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 pistons to pressurise fluid in the pumping chambers to pressures greater than 50,000 psi, the servo motor including an encoder to monitor position or velocity of the drive means, means to monitor the current flowing through the stator and a pressure sensor coupled to the output of the pumping chambers, whereby signals from the encoder, pressure sensor and stator are fed back to a computerised control unit to ensure that the pump operates at a selected pressure.

A water jet cutting machine comprising a cutting head driven by a computer numerical controlled (CNC) controller, the cutting head being coupled to an ultra high pressure pump according to any one of the preceding claims, whereby control of the pressure of the pump is independent of the control of the cutting head.

A method of operating a water jet cutting machine comprising supplying cutting medium at a pressure of greater than 50,000 psi from a pump driven by a servo motor with a feedback loop, using a computer to control, in real time, the supply pressure by monitoring the position or velocity of the servo motor, the current supplied to the servo motor and the output pressure of the pump.