Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
2000-07-18
2001-09-04
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S036000, C451S075000, C451S090000, C451S091000, C451S102000
Reexamination Certificate
active
06283832
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for rapidly moving an ultra high pressure liquid stream of a water jet head so that the stream discharged from the head can be used for surface treatment operations such as milling, polishing or cleaning of a workpiece surface.
DESCRIPTION OF THE PRIOR ART
Waterjet systems are used for cutting many types of materials. A waterjet system includes a waterjet head that is supplied with liquid at an ultra high pressure (UHP), for example 10,000 to 60,000 pounds per square inch (psi). The UHP liquid is discharged from the head in a high velocity stream against a workpiece. The liquid stream is used to cut through materials such as wood, paper and foam. An abrasive particulate material can be added to the stream, and the liquid/abrasive stream can be used to cut through composites, metals and other dense materials. The stream typically is concentrated in a small area, for example, for example as small as 0.05 inch diameter and has a high flow rate of perhaps one to three gallons per minute (gpm). Because of their high energy concentrations, such waterjet streams cannot be used for surface treatment operations such as cleaning, polishing or milling. A typical waterjet liquid or liquid/abrasive stream cuts too deeply and rapidly into the workpiece surface if it is stationary for even a small fraction of a second, and uniform surface treatment has not been possible.
It has been recognized that a continuously and rapidly moving, and accurately controlled, waterjet stream could be used for surface treatment operations if the energy dissipation could be uniformly spread over the workpiece surface area. However, there has been a longstanding and unsolved problem with providing an apparatus or method for achieving this result.
Waterjet systems normally incorporate a head drive arrangement, such as a computer numerically controlled (CNC) X-Y-Z drive system intended to move the waterjet head in a programmable pattern for making preprogrammed accurate cuts in a workpiece. These known drive systems cannot move the head continuously and quickly enough in a controlled fashion to carry out a satisfactory surface treatment operation without damaging the workpiece surface.
In an attempt to solve this problem, it has been proposed to provide a waterjet head incorporating a discharge nozzle with an angled outlet passage and a swivel arrangement for rotating the nozzle. The intent of this approach is to provide a UHP stream that rotates at high speed to increase the workpiece surface area contacted by the stream and reduce the energy concentration of the stream. U.S. Pat. No. 4,669,760 discloses such a swivel fitting arrangement for a UHP liquid stream, and U.S. Pat. Nos. 4,854,091 and 4,936,059 disclose swivel assemblies for liquid/abrasive streams. The arrangements disclosed in these patents have not been successful, at least in part because of the difficulty of using relatively movable swivel joint components for carrying a highly abrasive stream of material. In addition, swivel arrangements suffer from other disadvantages including complexity and the lack of a convenient way to easily adjust system parameters.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide an improved method for rapidly moving an UHP stream in an orbital or oscillatory path; to provide a method that can employ a conventional waterjet head and thereby avoid difficulties experienced with special swivel assemblies and the like; to provide a method in which system parameters can easily and conveniently be controlled; to provide a method that is inexpensive, reliable and simple; and to provide a method that overcomes problems with past approaches and solves the longstanding problem of using an UHP stream for workpiece surface treatment operations.
In brief, in accordance with the invention there is provided a method for treating a workpiece surface with a high pressure and high velocity liquid stream discharged onto the workpiece surface from the outlet nozzle of a waterjet head having a longitudinal axis. The method includes locating the waterjet head adjacent to the workpiece surface with the axis of the waterjet head intersecting the workpiece surface. The waterjet head and its outlet nozzle are held so they do not rotate around the waterjet head axis. The waterjet head is driven so that the waterjet head axis repetitively moves along a closed path.
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“Hydrocut Water Jet Cutting Machine”, the title pages and pp. 2-4, 2-5, 2-7, 2-8, 2-12, 4-29, 4-30 and 2-24 through 6-26 of EASB Cutting Systems manual No. F14-135 dated May 1999.
Eley Timothy V.
Kolehmainen Philip M.
McDonald Shantese
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