Abrasivejet Cutting Head With Novel Entrainment Structure and Method

Abstract

An abrasivejet cutting head assembly comprises abrasive inlet means for permitting entry of abrasive material into the head's longitudinally-extending passageway about an inlet axis that is preferably non-intersecting with the passageway's longitudinal axis. The abrasive is then prevented from entrainment into the waterjet by means within the passageway that only permits entrainment downstream from the region of abrasive entry after the abrasive particles have attained a generally coherent downstream velocity. The foregoing can be accomplished within the cutting head, within a user-replaceable insert in the cutting head or within the abrasivejet nozzle.

1 . An abrasivejet cutting head comprising:
 a body having a first internal longitudinally-extending through-passageway extending between upstream and downstream end regions about a longitudinal axis,   a waterjet-forming orifice member within the passageway for producing a generally axially aligned waterjet when the passageway upstream of the orifice member is coupled to a source of high pressure water,   abrasive inlet means for permitting entry of abrasive material into the passageway about an inlet axis, said abrasive material becoming entrained with the waterjet within a mixing region within the passageway downstream from the entry of abrasive material;   means for substantially preventing entrainment with the waterjet until said abrasive material has acquired a generally longitudinal velocity; and   means for releasably securing a generally axially-extending abrasivejet nozzle in alignment with said longitudinal axis to receive the abrasive-containing waterjet for discharge against a workpiece.   
   
   
       2 . The abrasivejet cutting head of  claim 1  including means for imparting a generally swirling movement of the abrasive material about the passageway prior to entrainment as the abrasive material moves towards the mixing region. 
   
   
       3 . The abrasivejet cutting head of  claim 1  wherein the said inlet axis is non-intersecting with said longitudinal axis 
   
   
       4 . The abrasivejet cutting head of  claim 1  or  3  including
 a generally tapered passageway between the waterjet-forming orifice member and the mixing region.   
   
   
       5 . The abrasivejet cutting head of  claim 1  or  3  wherein the walls of the passageway define a generally spiral path in the longitudinal direction. 
   
   
       6 . The abrasivejet cutting head of  claim 1  or  3  wherein the generally tapered passageway forms a cone. 
   
   
       7 . The abrasivejet cutting head of  claim 6  wherein the walls of the passageway converge at an angle in the range of between and including approximately 10° and approximately 70°. 
   
   
       8 . The abrasivejet cutting head of  claim 7  wherein the walls of the passageway converge at approximately a 20° angle. 
   
   
       9 . The abrasivejet cutting head of  claim 1  or  3  including means defining a second waterjet-accommodating passageway extending generally co-axially within said first passageway to carry the waterjet emerging from the waterjet-defining orifice past the entering abrasive to the mixing region. 
   
   
       10 . The abrasivejet cutting head of  claim 9  wherein said second passageway-defining means comprises a generally annular cone-shaped structure. 
   
   
       11 . The abrasivejet cutting head of  claim 10  wherein said generally cone-shaped structure has tapered exterior walls converging at approximately an 8° angle. 
   
   
       12 . An abrasivejet cutting head comprising:
 a body having a first internal longitudinally-extending through-passageway extending between upstream and downstream end regions about a longitudinal axis,   a waterjet-forming orifice member within the passageway for producing a generally axially aligned waterjet when the passageway upstream of the orifice member is coupled to a source of high pressure water,   abrasive inlet means for permitting entry of abrasive material into the passageway about an inlet axis, said abrasive material becoming entrained with the waterjet within a mixing region within the passageway downstream from the entry of abrasive material;   means for substantially preventing entrainment with the waterjet until said abrasive material has acquired a generally longitudinal velocity;   an generally axially-extending abrasivejet nozzle; and   means for releasably securing the generally axially-extending abrasivejet nozzle in alignment with said longitudinal axis to receive the abrasive-containing waterjet for discharge against a workpiece.   
   
   
       13 . The abrasivejet cutting head of  claim 12  including means for imparting a generally swirling movement of the abrasive material about the passageway prior to entrainment as the abrasive material moves towards the mixing region. 
   
   
       14 . The abrasivejet cutting head of  claim 12  wherein said inlet axis is non-intersecting with said longitudinal axis. 
   
   
       15 . The abrasivejet cutting head of  claim 12  or  14  including
 a generally tapered passageway between the waterjet-forming orifice member and the mixing region.   
   
   
       16 . The abrasivejet cutting head of  claim 15  wherein the mixing region is within the abrasivejet nozzle. 
   
   
       17 . The abrasivejet cutting head of  claim 16  second means defining a second waterjet-accommodating passageway extending generally co-axially within at least a portion of the abrasivejet nozzle to carry the waterjet emerging from the waterjet-defining orifice past the entering abrasive to the mixing region. 
   
   
       18 . The abrasivejet cutting head of  claim 17  wherein said second passageway-defining means comprises a generally annular cone-shaped structure. 
   
   
       19 . The abrasivejet cutting head of  claim 18  wherein said generally cone-shaped structure has tapered exterior walls converging at approximately an 8° angle. 
   
   
       20 . A user-replaceable insert for use in an abrasivejet cutting head of the type including:
 a body having a first internal longitudinally-extending through-passageway extending between upstream and downstream end regions about a longitudinal axis,   a waterjet-forming orifice member within the first passageway for producing a generally axially aligned waterjet when the first passageway upstream of the orifice member is coupled to a source of high pressure water,   first abrasive inlet means for permitting entry of abrasive material into the first passageway about a first inlet axis, and   means for releasably securing the generally axially-extending abrasivejet nozzle in alignment with said longitudinal axis to receive the abrasive-containing waterjet for discharge against a workpiece,   the insert comprising:   an insert body having a second internal longitudinally-extending through-passageway extending between upstream and downstream end regions about a second longitudinal axis, the waterjet-forming orifice member being mounted within the second passageway for producing the generally axially aligned waterjet when the first passageway upstream of the orifice member is coupled to a source of high pressure water;   second abrasive inlet means for permitting entry of abrasive material into the second longitudinal passageway about a second inlet axis; and   means for substantially preventing contact between the waterjet and abrasive material within the second longitudinal passageway until the waterjet is downstream from said entry,   said insert being adapted to be mounted within the cutting head with the first and second longitudinal axes in substantial alignment and with the first and second inlet axes in substantial alignment where the abrasive enters the second longitudinal passageway.   
   
   
       21 . The insert of  claim 20  wherein the second inlet axis is non-intersecting with said second longitudinal axis. 
   
   
       22 . The insert of  claim 20  or  21  including wherein at least a longitudinally extending portion of the interior walls of the insert define a generally tapered passageway between the waterjet-forming orifice member and the mixing region. 
   
   
       23 . The insert of  claim 20  or  21  including a waterjet-isolation member having a third waterjet-accommodating passageway extending generally co-axially with the second longitudinal axis within at least a portion of the insert to carry the waterjet emerging from the waterjet-defining orifice past the entering abrasive to a mixing region. 
   
   
       24 . The insert of  claim 23  wherein the waterjet-isolation member has a generally annular cone-shaped outer structure circumscribing the third passageway. 
   
   
       25 . The insert of  claim 24  wherein said generally cone-shaped structure has tapered exterior walls converging at approximately an 8° angle. 
   
   
       26 . An abrasivejet cutting head comprising:
 a body having a first internal longitudinally-extending through-passageway extending between upstream and downstream end regions about a longitudinal axis,   a waterjet-forming orifice member within the passageway for producing a generally axially aligned waterjet when the passageway upstream of the orifice member is coupled to a source of high pressure water,   means for securing a generally axially-extending abrasivejet nozzle in alignment with said longitudinal axis to discharge an abrasive-containing waterjet against a workpiece;   a generally annular, longitudinally extending abrasivejet nozzle secured by said securing means to discharge from its distal end an abrasive-containing waterjet against a workpiece, and having an abrasive-accommodating abrasive inlet passage communicating between its interior and exterior for permitting entry of abrasive material into abrasive nozzle about an inlet axis, and   a prevention member for substantially preventing entrainment of the abrasive material with the waterjet until the waterjet reaches a position downstream for the abrasive inlet.   
   
   
       27 . The abrasivejet cutting head of  claim 26  wherein the said inlet axis is non-intersecting with said longitudinal axis. 
   
   
       28 . The abrasivejet cutting head of  claim 27  or  28  including a generally tapered passageway between the waterjet-forming orifice member and said downstream position of entrainment. 
   
   
       29 . The abrasivejet cutting head of  claim 28  wherein the walls of the passageway converge at an angle in the range of between and including approximately 10° and approximately 70°. 
   
   
       30 . The abrasivejet cutting head of  claim 29  wherein the walls of the passageway converge at approximately a 20° angle. 
   
   
       31 . The abrasivejet cutting head of  claim 26  wherein the prevention member is attached to the waterjet-forming orifice member. 
   
   
       32 . The abrasivejet cutting head of  claim 26  wherein the prevention member is mechanically linked to the waterjet-forming orifice member. 
   
   
       31 . For use in an abrasivejet cutting head, an abrasivejet nozzle comprising:
 a generally tubular, body extending from an upstream end to a downstream end about a longitudinal axis and having an internal diameter in the range of approximately 0.015 inches to approximately 0.080 inches throughout at least the substantial portion of its length, said body having an abrasive-inlet opening downstream from its upstream end for permitting entry of abrasive material into the interior of the nozzle from an external source along an inlet axis that is not coaxially aligned with said longitudinal axis.   
   
   
       32 . The abrasivejet nozzle of  claim 31  wherein the inlet axis is not parallel to the longitudinal axis. 
   
   
       33 . The abrasivejet nozzle of  claim 31  wherein the inlet axis is non-intersecting with the longitudinal axis.