Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
1998-11-02
2001-05-01
Scherbel, David A. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S087000, C451S088000, C451S446000, C451S447000
Reexamination Certificate
active
06224463
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a workpiece finishing system, and more particularly to a system for impinging and recycling a grit and fluid slurry used to finish a workpiece.
Traditionally, metal workpieces must be belted, polished and then buffed prior to plating. The conventional wisdom has been that any “item to be plated, if the plating is to be a bright plate, must be highly polished. The plating can be no brighter than the surface to which it is applied.” C. W. Ammen,
Electroplater's Handbook
, 1986, page 69, published by Tab Books Inc. The belting employs a course grit belt, or wheel, which must be replaced approximately every five or six pieces. The polishing and buffing wheels also require extensive manual preparation, set up and replacement. The belting, polishing and buffing steps are typically performed by hand and must be very meticulously and uniformly done to ensure a bright base surface. However, the workplace is often extremely contaminated with oil and the like, and the operations are often tedious and time-consuming. Accordingly, part-to-part inconsistencies are prevalent, and labor and scrap costs are significant. Furthermore, an animal tallow, fatty acid and wax grease-stick compound is used on the polishing wheels to retain grit. A subsequent high temperature or acidic washing step is often employed in an attempt to remove the polishing compound, but with limited success. Any polishing compound remaining on the workpiece during plating leads to unacceptable plating adhesion to the base material, thus causing a very high scrap rate during plating.
It is also know to use a sand and water slurry to clean, but not finish, metal workpieces. An exemplary water and sand abrasive system is disclosed in U.S. Pat. No. 4,817,342 entitled “Water/Abrasive Propulsion Chamber” which issued to Martin et al. on Apr. 4, 1989. It is common for such systems to simply discard the water and inexpensive sand after each use. Moreover, the sand is not of a fine enough grit and sufficient hardness to adequately finish a workpiece for subsequent plating or for grit reuse.
Moreover, various slurry recycling systems have been attempted. For example, reference should be made to the following U.S. Patent Nos.: U.S. Pat. No. 5,791,970 entitled “Slurry Recycling System for Chemical-Mechanical Polishing Apparatus” which issued to Yueh on Aug. 11, 1998; U.S. Pat. No. 5,664,990 entitled “Slurry Recycling in CMP Apparatus” which issued to Adams et al. on Sep. 9, 1997; and U.S. Pat. No. 5,477,844 entitled “Slurry Recovery System for a Wet Cutting Saw” which issued to Meister on Dec. 26, 1995; all of which are incorporated by reference herewithin. However, none of these traditional systems exhibit the quick, efficient, cost effective and high performance characteristics of the present invention which is suitable for use on a variety of workpieces.
SUMMARY OF THE INVENTION
In accordance with the present invention, a preferred embodiment of a workpiece finishing system impinges a grit and fluid slurry onto a workpiece and then recycles the slurry for subsequent reuse. In another aspect of the present invention, a recovery tank is used for generally settling and concentrating the grit in the slurry, and for separating out a portion of the fluid from the grit. A further aspect of the present invention provides a venturi-type nozzle for expelling the grit and fluid onto a workpiece, wherein the nozzle has a selectively movable inlet thereby varying the slurry concentration properties of the nozzle. Still another aspect of the present invention provides a liquid overflow shelf above a set of baffles in the recovery tank for assisting in the separation of the grit and a portion of the liquid, whereby the liquid can be recycled without grit damaging the high pressure pumping device. A method of operating a workpiece finishing system suitable for recycling a grit and fluid slurry is also provided.
The present invention workpiece finishing system is advantageous over conventional devices in that the present invention does not require the expensive, labor intensive and scrap inducing polishing and buffing steps prior to plating. It is also envisioned that the belting operation may be minimized or even potentially deleted with the present invention. The very fine size and significant strength of the preferred carbide and water slurry, in combination with the impinging angles and high pressures, provide a dull matte-type workpiece finish which is not bright. Notwithstanding, it has been found that this matte finish of the present invention provides a superior bright mirrored appearance to the final plated workpiece as compared to conventional belted, polished and buffed workpieces. The part-to-part consistency and repeatability is also tremendously improved. Furthermore, a polishing compound is not necessary by use of the present invention, thereby eliminating the conventional washing operation and significantly reducing over all cycle time and/or plating scrap rates. The slurry separation and recycling devices and function of the present invention allows the use of the carbide and water slurry to be cost effective in a production environment, considering the high cost of the carbide grit. Moreover, the present invention recovery tank and nozzle constructions minimize maintenance while encouraging flexible usage for different workpiece designs. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
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Harness & Dickey & Pierce P.L.C.
J.C.J. Metal Processing, Incorporated
McDonald Shantese
Scherbel David A.
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