Abrading – Machine – Scouring device
Reexamination Certificate
2001-08-14
2003-04-08
Eley, Timothy V. (Department: 3724)
Abrading
Machine
Scouring device
C451S036000, C451S113000, C451S170000
Reexamination Certificate
active
06544110
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for performing abrasive work on a work piece using an abrasive visco-elastic medium and, in particular, to apparatus and methods that impart a relative cyclic motion between the work piece and the medium to provide a separation between the medium and work piece during each cycle which separation is occupied by a fluid having a viscosity less than that of the visco-elastic medium and where the deformation of the medium is between 50 and 99%.
BACKGROUND
1. Technical Field
The present invention relates to the technical field of machining and particularly to the field of non-traditional machining processes and equipment employing the techniques of and compositions for abrasive flow machining, grinding, deburring, radiussing, leveling and polishing of work pieces. Such processes are typically employed in the working of castings, forged parts, machined parts, and the like. Most often metal parts and the like. The present invention particularly relates to such operations where the flow is attained by relative motion, preferably orbital motion, between the work piece and the abrasive medium.
2. Prior Art
Abrasive flow machining has gained wide acceptance for a number of applications as the machining and finishing technique of choice. Such techniques are particularly adapted, for example, to working interior passages in work pieces, for light grinding, deburring, radiussing leveling and polishing of complex surfaces, and particularly three-dimensioned surfaces where surface detail requires working, and in repetitive working of multiple work pieces of complex form and shape.
In its simplest form, abrasive flow machining requires passing a visco-elastic medium containing an abrasive across the surfaces to be worked. The visco-elastic medium functions as a carrier for the abrasive, and transmits working force to the abrasive as the abrasive is carried across the surface. The medium flows to conform to the surface of the work piece.
In many contexts, advantage is taken of the visco-elastic character of the medium to pump the abrasive filled medium through passages, across surfaces, and between a work piece surface and a suitable member to confine the flow and constrain the medium in engagement with the surface of the work piece.
In many contexts, particular advantages are attained when the visco-elastic abrasive medium is also rheopectic, i.e., increasing in apparent viscosity with applied stress. (The behavior of rheopectic materials is, in essence, the converse of thixotropic behavior.) With the appropriate application of stress, typically either shear or compressive stress, to the medium, it is possible to substantially attain plug flow of the medium across the surfaces of the work piece to be worked in the operation. Substantially higher working force is applied to the surface by such plug flow when compared to viscous flow of the medium.
A more detailed description of the basic prior art on orbital abrasive flow polishing and grinding can be found in U.S. Pat. Nos. 3,521,412, 3,634,973, McCarty and U.S. Pat. No. 3,819,343, Rhoades.
One particularly attractive implementation of abrasive flow machining has been the employment of an rheopectic visco-elastic abrasive medium in combination with an orbital drive mechanism, where the medium and a work piece are confined together in a pressurized chamber with a “displacer member” generally conforming to the inverse of the shape of the work piece surfaces to be worked, and where the orbital motion of the work piece relative to the chamber displacer member and the contained medium causes the work piece to be effectively worked. Such operations take advantage of the ability of the medium to conform to the surfaces of the work piece, and even complex, highly detailed surface shapes can be worked with considerable success and effectiveness. See U.S. Pat. No. 5,125,191, Rhoades.
It is in the context of such abrasive machining to which the present invention particularly relates, although the considerations disclosed and described herein may have broader and more general applicability in specialized circumstances.
PROBLEMS IN THE ART
Orbital working with abrasive flow machining techniques have been employed with effectiveness. Such operations have been limited in some contexts, however, by several factors. First and foremost, the mode of operation in the prior work is based upon fluid or plastic flow of the medium across the surfaces of the work piece. The action is based on “extrusion” of the medium through a restricted gap between the work piece and the mating displacer or mandrel. Such flow does an excellent job of polishing surfaces at high speed, but for more demanding operations involving significant removal of stock from the work piece, the operation is typically slow. There is a need in the art for techniques for attaining adequate working at higher and more productive rates.
Second, the chamber in which the orbital working takes place must be closed or seated to confine the medium within the chamber, assuring adequate strain rates are attained and imparted to the medium to provide the required work, adding to the complexity of the equipment and the time and effort required to change work pieces. These requirements also contribute substantially to the cost of the process and equipment and may, in some cases, be a limiting factor determining the rate of production.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide an improved abrasive machining process and apparatus in which a separation is maintained during the processing between the visco-elastic medium and portions of the work piece. It is another object of the present invention to provide an improved abrasive machining process and apparatus employing a visco-elastic abrasive medium which conforms to the shape and conformation of each work piece.
It is another object of the present invention to provide an improved abrasive machining process and apparatus employing a visco-elastic abrasive medium which performs abrasive work on each work piece predominantly by elastic deformation.
It is still another object of the present invention to provide an improved abrasive machining process and apparatus employing a visco-elastic abrasive medium with no requirement for a sealed working chamber.
Yet another object of the present invention is to simplify the requirements for mandrels and displacer elements employed in the system for abrasive machining, and in some cases to eliminate such requirements entirely.
It is yet another object of the present invention to provide an improved abrasive machining process and apparatus employing a visco-elastic abrasive medium for light grinding, deburring, radiussing, leveling and polishing of complex surfaces, and particularly three-dimensioned surfaces where surface detail requires working and repetitive working of multiple work pieces of complex form and shape.
These and still other objects, which are made apparent in the following disclosure and description of the invention, are attained in the present invention.
SUMMARY OF THE INVENTION
The present invention provides light grinding, deburring, radiussing, leveling and polishing of complex surfaces, and particularly three-dimensioned surfaces where surface detail requires working, and in repetitive working of multiple work pieces of complex form and shape. Generally, the apparatus of the present invention comprises a chamber which can be either closed or open for mounting a work piece. Preferably the new medium is fed to a gap, the chamber preferably includes a plurality of inlets for feeding a visco-elastic abrasive medium therein. A drive is provided for imparting relative motion between the work piece and the visco-elastic medium by contacting the visco-elastic medium so as to create a separation between the medium, and portions of the work piece. The separation is filled with a fluid of less viscosity than the medium, such as air. The separation is preferably maintained in the areas adjacent the inlets.
Gilmore James Randall
Rhoades Lawrence J.
Eley Timothy V.
Extrude Hone Corporation
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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