IE903757A1 - Cutting tool assembly - Google Patents

Abstract

In rotating machines such as turbines there are ring-like components with thin internal liners which must be removed after a period of service and replaced. Conventional methods of removal by turning on a vertical lathe may result in damage to the underlying surface because the component is distorted and deviates from true circularity. In the modified system the toolbit (22) is clamped in a holder (32) which is free to move radially on a slideway (34). Fastened in the holder is a follower (26) which lies opposite the toolbit and is forced against the outer cylindrical surface (16) of the component (10) by a spring (30). The distance between the toolbit and the follower can be adjusted by a micrometer screw (28). When the liner is being machined out the toolbit will follow distortions of the ring and only remove lines material. USE/ADVANTAGE - Accurate, easily adjustable method of removing liner material without damage to component.

Description

Cutting Tool Assembly Technical Field This invention relates to a cutting tool 5 assembly, and especially to a cutting tool assembly with a slideable mount.

Background Art Reworking turbine engine components with contoured closed shapes, such as stators or other ring shaped articles, frequently requires precise removal of thin coatings. These coatings are used to maintain close clearances between stationary and rotating components and/or protect the components from heat, oxidation-corrosion and wear. Such coated components consist of a closed, contour shaped, metallic substrate (hereafter referred to as a ring shaped part) having a metallic bond coat, typically approximately 0.008 inches thick, and either an abradable seal, thermal barrier coating, abrasive coating, or hard facing, typically between approximately 0.008 to 0.024 inches thick, on the bond coat. These latter coatings may be metallic, intermetallic ceramic, and mixtures thereof along with intentional porosity in some circumstances. Abradable seals may also include a metallic honeycomb filled with an abradable material.

After a period of use, the ring shaped part will require repair and the coating must be removed.

Various techniques have been employed to accomplish this task: machining, chemical stripping, grit blasting and combinations thereof (U.S. Pat. Nos. 4,339,282, and 4,425,185, incorporated herein by reference). However, each of these techniques has inherent disadvantages. Once the article has been used in an engine it often becomes warped. If machining, with a conventional tool holder, is employed to remove the coating, part of the metal substrate may also be removed; damaging the article. Chemical stripping uses strong acids or bases which can attack the substrate; while grit blasting can also cause substantial damage to the substrate if not performed skillfully.

Machining, as mentioned above, can be accomplished with a lathe and particularly with a vertical turret lathe. Lathes have commonly been utilized in the art for part fabrication to remove burrs or chips, for thread cutting, and to remove rubber or plastic from steel rollers; among other applications. (U.S. Pat. Nos. 1,354,776, 2,351,892, 3,763,727, and 3,771,392, incorporated herein by reference). Lathe tooling has developed such that a spring may be used with a movable cutting tool (U.S. Pat. Nos. 932,576, and 2,726,650, incorporated herein by reference).

Yet, a lathe tool which will consistently cut a designated amount off the inner diameter of a (warped) closed, contour shaped article, a stator for example, without damaging the article, is not currently available. Either a designated amount of material will be removed, not allowing compensation for deformities, or a varying amount of material will be removed with the blade retracting when material with a varying hardness is encountered. As a result, the search for improved, accurate, easily used cutting tool continues.

Disclosure of Invention This invention consists of a slideably mounted 5 cutting tool assembly for machining closed, contour shaped articles, which have a plane perpendicular to the center axis, such as rings or stators, to remove a layer from a circumferentially disposed surface (usually an essentially cylindrical surface). With the use of a slideable mount located by a guide mechanism (a cam follower) which contacts a second circumferentially disposed workpiece surface (usually essentially cylindrical) (different from that being machined, but coaxial thereto), a cutting means is able to follow the eccentricities of an out of round article as relative motion is produced between the tool assembly and the workpiece. This allows the desired amount of coating, or coating and bond coat to be removed without damaging the substrate.

The foregoing and other features and advantages of the present invention will become more apparent from the following description and accompanying drawings.

Brief Description of Drawings Figure 1 shows an embodiment of the present invention.

Figure 2 shows the Figure 1 embodiment in combination with a cross sectional view of a contoured closed shaped article which is being cut.

Best Mode for Carrying Out the Invention Figure 1 shows one embodiment of the present invention. The major components include: a tool holder/follower, a cutter, a rotatable table. Figure 1 shows a closed, contoured shaped component (10) which is adapted to rotate about a center line (12). The object (10) has a cylindrical inner surface (14) and a cylindrical outer surface (16). The inner surface (14) has thereon a coating (18) which must be removed without damaging the metallic substrate. This is accomplished by the invention tool means (20) despite warpage and other distortion of the component which has occurred in service.

The invention tool assembly (20) as shown in greater detail in Figure 2 wherein cutting means (22), in this case a carbide or similar material tool, is mounted on a cutter support (24) in opposition to a cam follower guide means (26). The spacing between the cutter (22) and the guide means (26) is controlled by the micrometer means (28) . The closed, contour shaped component has inner surface (14) and outer surface (16) and in the particular case shown in Figure 2 has a filled honeycomb structure (38) brazed to the interior of the ring shaped article.

The cam follower guide means (26) is adapted to ride on the outer surface (16) of the closed, contour shaped component and the spring (30) biases the tool mount (32) so that the guide means (26) contacts the outer surface (16) of the ring. Guide means (26) is preferably arranged so that it follows the outer surface (16) without excessive friction, this may be achieved with a ball or roller bearing arrangement in the guide means (26) which actually contacts the surface (16). While a spring (30) is shown for biasing the cutter (22), other alternatives such as hydraulic and pneumatic cylinder may be used. In certain applications this biasing means may be optional. The gap between the guide means (26) and the cutter (22) is adjusted by the micrometer means (28) so that all or a portion of the honeycomb is removed depending upon the exact requirements.

Warpage of the ring will, as a major consequence, produce a ring with a radius which varies slightly.

The tool holder means (32) is adapted to slide in a radial direction (with respect to the ring) (R) on the arm (34) which is held perpendicular to the center line axis. The sliding action will occur automatically as the article rotates and the effective article diameter changes. Thus the tool cuts at a constant distance from the outer diameter rather than at a constant diameter from the contoured closed center of the ring as in the prior art.

In the embodiment shown in Figures 1 and 2 the ring rotates about its center line axis. It is clear, however, an equivalent result could be obtained by rotating the arm (34) about the same center line axis while keeping the major axis of the arm essentially aligned with the radius. It is also apparent that while the cutter (22) is shown removing an internal coating it could easily be modified to remove a coating from the outer ring surface by having the guide means locate on the inner diameter.

The artisan will appreciate that variations on this theme are possible. The cutting means can be moved radially (relative to the ring) during the process (as for example if the micrometer means were to be adjusted during cutting), it can be moved axially as well so that a narrow cutter (a single point tool) can remove the coating. It is also possible to use multiple cutter means. As an alternative to the type of cutter shown in Figures 1 and 2, a powered high speed grinding wheel could be used to remove the coating.

Although this invention has been shown and described with respect to detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.

Claims (11)

CLAIMS:

1. An apparatus for removing a fixed amount of material from an inner surface of a part having a closed, contoured shape, said part having an outer surface, which comprises: a. a guide means for following said outer surface of said part; b. a cutter means for removing said material from said inner surface; and c. connection means for connecting said cutter means and said guide means such that said guide means and said cutter means follow said contoured shape, including any eccentricities.

2. A machine for removing at least one layer of material from the interior surface of a contoured closed shaped article, said article having an outside cylindrical surface, which comprises: a. means for holding said article; b. a cutting tool assembly for removing at least one layer of material from said article, said cutting tool assembly including: i. an arm, disposed essentially on a radius of said ring shaped article; ii. a slideable mount which is located on said arm; iii. said mount having a guide means for locating against the article outer surface; iv. said guiding means having a low friction cam follower guide means for allowing the guiding means to locate and follow the article's outer diameter; v. a micrometer means for controlling said guide means; vi. said mount having a cutting means for removing material from the article interior surface said cutting means being held at a fixed distance from said guide means along a radius of the article; vii. means for creating relative motion between said machine and said cutting tool assembly; whereby the motion between the machine and the cutting tool assembly causes the cutting means to remove at least one layer of material from said article, and wherein said mount floats on said arm allowing a fixed thickness of material to be removed from the article outer diameter surface despite eccentricities in the article circularity.

3. An article as in claim 2 wherein said low friction cam follower guide means is selected from the group consisting of roller bearings and ball bearings.

4. An article as in claim 2 wherein said cutting 25 means is selected from the group consisting of cutting tools and high speed grinders.

5. An article as in claim 2 wherein said forcing means is selected from the group consisting of springs, hydraulic cylinders, and pneumatic cylinders.

6. Apparatus for removing material from the interior surface of a ring shaped article, said article having an outside surface, including: a. cutting means for removing said coating from said interior surface; b. guide means adapted to slide on said outer surface, said cutting means and said cutting means being aligned on a common radius of said ring; c. mounting means connecting said cutting means to said guide means, said mounting means being adjustable to vary the gap between said cutting means and said guide means so that a controllable gap separates said cutting means from said guide means; d. said mounting means being slideably mounted and being adapted to move along a radius of said ring shaped article; e. wherein said ring shaped article is positioned between said cutter means and said guide means and relative motion, between said ring and said cutting means, is induced about an axis approximately through the center of said ring and said cutter removes a controlled layer of material from said interior surface.

7. A method for removing material from the interior surface of a closed, contour shaped article, said article having an outer diameter, which comprises: a. using a cutting tool assembly, said assembly having: i. a guide means for following said outer diameter of said article; ii. a cutter means for removing said material from said inner diameter; and iii. connection means for connecting said cutter means and said guide means such that said guide means and said cutter means follow said contoured shape, including any eccentricities; b. holding said article; c. creating relative motion between said cutting tool and said article; whereby the relative motion between said cutting tool assembly and said article causes said cutter means to traverse said interior surface removing a controlled amount of material, and wherein said guide means controls the amount of material said cutter means removes.

8. An apparatus for removing a fixed amount of material from an inner surface of a part having a closed contoured shape substantially as herein described with reference to and as shown in the accompanying drawings.

9. A machine for removing at least one layer of material from the interior surface of a contoured closed shaped article, substantially as herein described with reference to and as shown in the accompanying drawings.

10. A method for removing material from the interior surface of a closed, contour shaped article, substantially as herein described with reference to the accompanying drawings . 1 5

11. The features described in the foregoing specification, or any obvious equivalent thereof, in any novel selection.