Waterjet device

Abstract

An abrasive waterjet apparatus comprising a water jet fluid flow circuit, a positive displacement pump connected to the water jet fluid flow circuit, a pressure fluctuation equalising device ( 24 ) for said circuit, and an abrasive cutting nozzle assembly. The pressure fluctuation equalising device ( 24 ) comprises a high pressure chamber ( 27 ′) connected to the waterjet fluid flow circuit, a low pressure chamber ( 29 ), and a moveable pressure equalising member ( 20, 21 ) that separates said chambers. In order to equalise pressure fluctuations in the waterjet fluid flow circuit, the moveable pressure equalising member ( 20, 21 ) is arranged to alter the volume of the high pressure chamber ( 27 ′).

1 . An abrasive waterjet apparatus comprising:
 a waterjet fluid flow circuit;   a positive displacement pump connected to the waterjet fluid flow circuit;   a pressure fluctuation equalising device for said circuit; and   an abrasive cutting nozzle assembly,   said pressure fluctuation equalising device comprising
 a high pressure chamber connected to the waterjet fluid flow circuit, 
 a low pressure chamber, and 
 a moveable pressure equalising member that separates the chambers, 
 said moveable pressure equalising member arranged to alter the volume of the high pressure chamber in order to equalise pressure fluctuations in the waterjet fluid flow circuit. 
   
   
   
       2 . The abrasive waterjet apparatus according to  claim 1 , wherein the high pressure chamber is designed so that fluid contained therein exerts a first force on a first part of the moveable pressure equalising member, and the low pressure chamber is designed so that fluid contained therein exerts a second force on a second part of the moveable pressure equalising member, and wherein said pressure equalising member is arranged to be displaced in accordance with the first and the second force. 
   
   
       3 . The abrasive waterjet apparatus according to  claim 2 , wherein the cross section area, perpendicular to the direction of movement, of the first part of the moveable pressure equalising member is smaller than the cross section area, perpendicular to the direction of movement, of the second part of the moveable pressure equalising member. 
   
   
       4 . The abrasive waterjet apparatus according to  claim 1 , comprising one or more sensor devices which are adapted to detect the position or motion, or both, of the moveable pressure equalising member. 
   
   
       5 . The abrasive waterjet apparatus according to  claim 4 , further comprising a motor controller for controlling the drive of the positive displacement pump. 
   
   
       6 . The abrasive waterjet apparatus according to  claim 5 , further comprising a control system, to which said sensor devices and the motor controller are connected, whereby the control system is adapted to control the pump on the basis of the position or motion of the moveable pressure equalising member. 
   
   
       7 . The abrasive waterjet apparatus according to  claim 1 , wherein a plunger of the positive displacement pump is arranged to be returned by the fluid pressure of a fluid conduit, and wherein the flow of said fluid conduit is affected by the position of the pressure fluctuation equalising device, whereby the position of the moveable pressure equalising member can stop the pumping action. 
   
   
       8 . The abrasive waterjet apparatus according to  claim 7 , wherein the fluid conduit is connected to the pressure fluctuation equalising device through a connection, which connection is arranged to be closed by the moveable pressure equalising member, and which connection is arranged to be opened upon movement of the moveable pressure equalising member. 
   
   
       9 . The abrasive waterjet apparatus according to claim, wherein the volume of the high pressure chamber is greater than the volume of waterjet fluid discharged through the nozzle assembly of the abrasive waterjet apparatus during one pump rotation. 
   
   
       10 . A pressure fluctuation equalising device for an abrasive waterjet apparatus, said apparatus having a positive displacement pump connected to a waterjet fluid flow circuit,
 said pressure fluctuation equalising device comprising:
 a high pressure chamber connected to the waterjet fluid flow circuit, 
 a low pressure chamber, and 
 a moveable pressure equalising member that separates the chambers, 
 said moveable pressure equalising member is arranged to alter the volume of the high pressure chamber in order to equalise pressure fluctuations in the waterjet fluid flow circuit.