Abrasive water jet cutting apparatus

An apparatus for cutting a work by means of an abrasive water jet containing abrasive particles, comprising:

• (a) a source of water under pressure;
• (b) abrasive suspension supply means for supplying an abrasive suspension such that abrasive particles with an average size of up to about 100 microns are held in suspension in water;
• and
• (c) an abrasive water jet nozzle assembly to be held opposite the work to be cut and communicating with both the pressurized water source and the abrasive suspension supply means, the nozzle assembly mixing the pressurized water and the abrasive suspension for directing the resulting mixture against the work as an abrasive water jet, said nozzle assembly comprising:
• (i) a nozzle body having a tip end to be directed toward the work and a base end to be directed away from the work, said nozzle body having an axial bore extending between said base end and said tip end;
• (ii) a pressurized water nozzle tip mounted in said axial bore of said nozzle body and adjacent said base end thereof and having an orifice in communication with the pressurized water source;
• (iii) an abrasive water nozzle tip mounted on said tip end of said nozzle body and having an orifice in alignment with said orifice of the pressurized water nozzle tip;
• (iv) an internal nozzle member mounted in said axial bore of said nozzle body and between said pressurized water nozzle tip and said abrasive water nozzle tip and having defined therethrough an ejected water passageway in alignment and communication with said orifices of said pressurized water nozzle tip and said abrasive water nozzle tip;
• (v) an abrasive suspension inlet port defined in said nozzle body for the admission of the abrasive suspension from the abrasive suspension supply means;
• (vi) an abrasive suspension chamber of annular shape defined between said nozzle body and said internal nozzle member so as to surround said ejected water passageway in said internal nozzle member, said abrasive suspension chamber being in communication with said abrasive suspension inlet port in said nozzle body;
• (vii) a plurality of abrasive suspension passageways defined in said internal nozzle member for communicating said abrasive suspension chamber with said ejected water passageway, said abrasive suspension passageways being angularly spaced from one another about said ejected water passageway;
• and
• (viii) said orifice of said abrasive water nozzle tip having an upstream opening of a diameter equal to, or slightly smaller than, a diameter of said ejected water passageway, said upstream opening being joined with said ejected water passageway in such a manner that said orifice of the abrasive water nozzle tip includes an upstream tapered portion having a diameter that increases gradually toward said upstream portion and forms a smooth continuation of said ejected water passageway to produce a streamlined flow of the ejected water, said abrasive suspension passageways being joined with said ejected water passageway so as to be directed to said upstream opening and having walls which merge with said upstream tapered portion of said orifice of said abrasive water nozzle tip to supply the abrasive suspension into said upstream opening in the form of an outer layer of streamlined flow of the abrasive suspension, surrounding the streamlined flow of the ejected water.