High pressure abrasive-liquid jet

Abstract

An abrasive-liquid jet cutting head comprising at least one mixing stage; a first mixing chamber arranged to accept a coherent high pressure liquid from an orifice and flow of accelerated abrasive particles from an abrasive feed tube and produce a pressurized slurry-like flow that enters a nozzle; wherein a nozzle to orifice ratio is in a range of about 1.2:1 to 2.49:1 wherein nozzle opening size to orifice opening size is 1.2 to 2.49 times larger in size.

Description

[0001] This application claims priority of United States Provisional Patent Application to Benjamin F. Dorfinan and Steven A. Rohring, Ser. No. 60 / 668,453 for METHODS FOR IMPROVING ABRASIVE JET TECHNOLOGY AND APPARATUS FOR THE SAME, filed on Apr. 5, 2005.FIELD OF INVENTION [0002] The invention relates to the field of high-pressure abrasive-liquid jet (also sometimes known as ‘Abrasive Waterjet’ or ‘Abrasivejet’) technology often used in material removal, and more specifically, improvements upon conventional abrasive-liquid jet technology in the area of cutting head assemblies considering the important relationship between cutting head components of Orifices and Nozzles (also known as Focusing Tubes or Mixing Tubes). BACKGROUND OF THE INVENTION [0003] Conventional abrasivejet technology is used to cut a variety of materials but is found to be highly inefficient in the use of energy and resources mainly due to cutting head design limitations that incorporate a 3:1 nozzle to orifice ra...

AI Technical Summary

Benefits of technology

[0019] It is a general object of the present invention to provide an improved cutting head with a smaller nozzle to orifice ratio in order to create more impact energy for faster processing of materials.

[0020] Another object of the present invention is to provide an improved cutting head using non-conventional abrasives along with optimized cutting head configurations to allow for improvements to traditional abrasivejet applications along with creating new applications currently not associated with conventional abrasivejet.

[0021] Another object of the present invention is to provide an improved cutting head to process subject materials more efficiently through optimization of the abrasive mixture process into a liquid jet stream, resulting with reduced overall costs of the abrasivejet technique for cutting or other material removing technology, as well as surface treatment.

[0022] Yet another object of the present invention is to provide a cutting head that provides improvements to the abrasivejet technique to achieve increased processing speeds, better tolerances and better quality surface finish of subject.

[0023] Still another object of the present invention is to provide a cutting head that fosters the creation of several novel manufacturing.

[0024] A further object of the present invention is to provide a cutting head that facilitates faster particle acceleration for a more effective mixing of non-traditional heavy metallic abrasive particles with the waterjet, resulting in lower costs, recycling of the heavier abrasive particles and greater cutting speeds.

Problems solved by technology

Conventional abrasivejet technology is used to cut a variety of materials but is found to be highly inefficient in the use of energy and resources mainly due to cutting head design limitations that incorporate a 3:1 nozzle to orifice ratio.

Conventional abrasivejet is also currently limited to perform one purpose at a time such as thru cutting of material or surface removal of material as there are not any abrasivejet systems currently producing useful byproducts simultaneously with the initial purpose of material removal.

A more important similarity, as well as deficiency, of conventional abrasivejet technology is the widespread use of garnet abrasives over all other abrasives.

Conventional abrasivejet technology does not effectively use abrasives other than garnet due to numerous factors such as higher initial costs of most other hard abrasives compared to garnet and the inability of other hard abrasives to cut significantly faster than garnet.

These factors generally result in higher overall costs of abrasive consumption after considering the final amount of material cut.

There is also the limitation of conventional abrasivejet cutting head technology preventing use of harder abrasives than garnet because of the increased costs of accelerated nozzle wear created by these harder abrasives.

The similarities of conventional cutting head designs' primary use of only one type of nozzle material, use of only one abrasive medium, and use of only two types of orifice materials, mainly produce a common limitation of an approximate 3:1 nozzle to orifice ratio.

Therefore, a relatively larger volume of area in the nozzle bore compared to the smaller area of volume of the liquid energy creates inefficiencies.

A solution to create a more efficient use of energy would incorporate a smaller nozzle to orifice ratio such as 2:1 but this solution is not currently viable with use of conventional cutting heads and garnet abrasives.

The best solution for conventional technology has been use of relatively small volumes of high-pressure liquid in the abrasivejet mixture allowing for viable cutting, but this also reduces the effective cutting energy by being dispersed over a greater area, hence, the effective energy is not optimally focused.

A ring orifice plate or disk such as employed in the U.S. Pat. Nos. 3,424,386, 4,080,762 and 4,125,969 to provide the fluid jets around the sand stream has many disadvantages including: the introduction of pressurized fluid tangentially into a nozzle a short distance above the orifice disk is not conducive to the generation of a coherent fluid jet due to flow disturbances upstream of the orifices; sand in the central portion of a nozzle creates an abrasive environment that can weaken the interior wall of the annular fluid chamber without being detected; pressurized fluid in the outer annular space results in a nozzle that is very large in dimensions as both interior and exterior walls must be sized to accommodate the fluid pressure; and sealing the annular orifice disk can be very troublesome.

These problems would be intensified at higher pressures.

The problem areas with the prior art cutting head shown in this patent are the orifice, the mixing chamber and the liquid jet.

A problem with this design is the separation effect of the jet as it starts to break up.

This method adds abrasive to the stream before entering the orifice.

The advantage of this method is that it produces a coherent jet, but the disadvantage is that components such as tubing, valves and orifices wear out quickly due to the abrasive suspension inside the system severely eroding everything it contacts.

Another disadvantage of the orifice designs in conventional abrasivejet is the sharp transition from the pump tubing to the relatively small orifice.

This sharp transition creates a high resistance of the pressure flow and does not allow for properly formed liquid optimization, resulting with jet distortion, and decrease in overall energy efficiency of the system.

However, there are many reasons why garnet is not the optimum abrasive available when considering the complete abrasivejet system, recycling and the ability to perform two or more processes in one operation.

One reason is that garnet is not the optimum abrasive is because it is not effectively recyclable.

Another disadvantage is that very hard subject materials such as carbides and hard ceramics are generally not cut with abrasivejet technology because of the very low cutting speed ability of garnet to cut these materials.

Conventional abrasivejet techniques also have problems with feeding heavier abrasives because of the inherent design limitation of a large nozzle to orifice ratio.

A major problem with prior art is the high concentration of air in the abrasivejet that significantly reduces the overall energy for cutting or treating.

However, the greatest problem with prior art is the relatively slower speeds of abrasive particles compared to the initial speed of the liquid jet.

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