Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
1999-12-14
2001-08-07
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S053000, C451S060000, C451S099000, C451S446000, C222S146600, C241SDIG014, C062S346000, C062S354000
Reexamination Certificate
active
06270394
ABSTRACT:
FIELD OF THE INVENTION
The invention provides an apparatus and method for blasting small ice particulates onto surfaces, for cleaning, decontaminating, deburring, or smoothing the surfaces. More particularly, the invention provides ice particulates within a narrow range of size distribution supplied through an apparatus that makes these particulates and motivates them to a required velocity, without intermediate storage of the particulates.
BACKGROUND OF THE INVENTION
In recent years there has been increasing interest in the use of ice blasting techniques to treat surfaces. For certain applications, ice blasting provides significant advantages over chemical surface treatment, blasting with sand or other abrasive materials, hydro-blasting, and blasting with steam or dry ice. The technique can be used to remove loose material, blips and burrs from production metal components, such as transmission channel plates after machining, and even softer material, such as organic polymeric materials, including plastic and rubber components. Because water in either frozen or liquid form is environmentally safe, and inexpensive, ice blasting does not pose a waste disposal problem. The technique can also be used for cleaning surfaces, removing paint or stripping contaminants from a surface, without the use of chemicals, abrasive materials, high temperatures, or steam.
Because of these apparent advantages, ice blasting has generated significant commercial interest which lead to the development of a variety of technologies designed to deliver a high pressure spray containing ice particulates for performing particular surface treatment procedures. Some of these technologies are shown, for example, in U.S. Pat. Nos. 2,699,403; 4,389,820; 4,617,064; 4,703,590; 4,744,181; 4,965,968; 5,203,794; and 5,367,838. Despite all the effort devoted to ice-blasting equipment, the currently available equipment still suffers significant shortcomings that lead to job interruption and downtime for equipment maintenance. This is a particular disadvantage in using ice blasting in a continuous automated production line to treat surfaces of machined parts.
In general, in the prior art equipment, the ice particulates are mechanically sized, a process that can cause partial thawing of ice particulates so that they adhere together, producing larger particulates. As a result, there is not only a wide distribution in the size of ice particulates produced, and the velocity at which these particulates are ejected from a nozzle onto the surface to be treated, but also frequent blockages that necessitate equipment downtime for clearing the blocked area. Moreover, in the available equipment, the ice particulates are retained in storage hoppers, where they are physically at rest, while in contact with each other. This results in ice particulates cohering to form larger ice blocks that ultimately cause blockages with resultant stoppage of the ice blasting operation due to an insufficient supply of ice particulates to the blasting nozzle. In other equipment, the ice particulates flow along a path with abruptly varying cross-sectional area for flow. This frequently causes the accumulation of fine ice particulates in certain low pressure areas. This accumulation also ultimately results in blockage of the apparatus, causing the ice blasting operation to come to an unscheduled stop.
There yet exists a need for ice-blasting apparatus, and a method of ice blasting, that can be carried out continuously, with minimal risk of unscheduled stoppages due to ice blockages forming in the apparatus. Such an apparatus, and method of its operation, will allow more efficient ice-blasting operations, reducing labor costs for unscheduled stoppages, labor costs incurred in freeing the equipment of blockages, and permit more ready integration of ice blasting into an automated production line.
SUMMARY OF THE INVENTION
The invention provides an apparatus for producing ice particulates within a narrow size distribution, and delivering these ice particulates at a predetermined velocity onto a substrate, thereby treating the surface of the substrate to remove contaminants, to deburr, or to otherwise produce a smooth, clean surface. The apparatus of the invention may be operated continuously, with significantly reduced risk of blockage by accumulated ice, as compared to currently-available ice-blasting equipment.
In general, the invention provides an ice particulate-making apparatus that has a curved, refrigerated surface on which a thin ice sheet is formed, which is then fragmented into ice particulates that are fluidized and carried in a conduit of flowing air to impact onto the surface to be treated. The conduit is preferably smooth, and of substantially uniform cross-sectional area for flow, to minimize or eliminate ice particulate agglomeration and consequent clogging of the apparatus. To further reduce the risk of apparatus blockages, the invention prefers (but is not limited to use of transport air at a temperature above about 32° F. This temperature minimizes the risk of valves, for example freezing after prolonged use, and is yet sufficiently low that significant ice melting does not occur while the ice is in contact with the transport air.
In accordance with one embodiment of the invention, the apparatus includes a refrigerated device with a curved surface, such as a cylindrical drum that is preferably rotatably mounted with outer surfaces adapted to form a thin layer of ice. In one embodiment, the drum is horizontally mounted in a basin of water. As the drum, that is refrigerated to a surface temperature of at least 0° C., rotates in the basin, a thin curved ice sheet forms on the cylindrical outer surfaces of the drum. An ice breaking tool, such as a doctor-knife, is mounted near the side of the drum that is ice-coated, and extends along the length of the drum. The knife is oriented to intercept a leading edge of the ice sheet and fragment it into ice particulates as the drum rotates. An ice-receiving tube is located adjacent, and extends along the length of, the doctor-knife and is oriented so that a longitudinal slot in the tube is able to receive the ice particulates formed. In preferred embodiments, a vibrator device is attached to or integral with the tube to reduce the risk of ice agglomeration on the tube. One end of the tube is coupled to a hose supplying cold air, and the other end is coupled to an ice delivery hose that applies suction to the interior space of the tube. The delivery hose terminates in an ice blasting nozzle. As ice particulates enter into the ice-receiving tube, the particulates are carried by a continuously flowing stream of cold air into the delivery hose and thence into the ice-blasting nozzle. The flow conduit of the ice particulates (tube and hoses) has a substantially smooth (i.e. free of obstructions and surface irregularities) inner surface, and substantially uniform cross-sectional area for flow, thereby avoiding low velocity spots where ice particulates may settle, accumulate, and cause blockages.
In another embodiment, the refrigerated drum is sprayed with water to form the thin ice sheet. The drum may be horizontally mounted, as preferred to form a uniform thickness ice-sheet, or may be inclined at an angle. In one such embodiment of the invention, the refrigerated drum is vertically-oriented and water is sprayed onto the drum to form a thin curved ice sheet. As explained above, a doctor-knife extends along the length of the drum to fragment ice particulates from the sheet into an adjacent co-extensive ice-receiving tube.
In a further alternative embodiment of the invention, the refrigerated cylindrical surface is the interior surface of an annulus. At least one spray nozzle is mounted to direct water onto the cylindrical walls of the annulus to form a thin ice sheet. As before, a doctor-knife extending along the length of the cylindrical wall is used to fragment ice particulates of narrow size distribution from the ice sheet into a slot in an ice-receiving tube that is adjacent to and co-extensive with th
Fisher Norman W.
Visaisouk Sam
Christensen O'Connor Johnson & Kindness PLLC
Eley Timothy V.
Universal Ice Blast, Inc.
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