Cylindrical stack of retaining rings for the surface treatment of turbine vanes

Abstract

The present invention relates to a segment of a fastener, the fastener comprising several such segments arranged to form a fastening ring, the segments comprising a carrier segment and a top cover segment.

Description

[Technical Field]

[0001] The present invention relates to a mount for multiple substrates to be treated in a surface treatment. [Background technology]

[0002] A range of different processes for polishing the surface layer of a workpiece is known, depending on the application, material, and structure of the surface layer. In addition to simply removing material from the surface, the purpose of polishing often includes reducing the surface roughness. This may be desired for purely aesthetic reasons, such as to produce a shiny surface, or may be required for technical requirements, such as to reduce the coefficient of friction, minimize the adhesion or inclusion of foreign particles so that the required surface porosity is maintained, or prevent surface contamination. This can improve aerodynamics, increase efficiency, and reduce oil consumption. In the art, the roughness of solid surfaces is generally characterized by various roughness measurement parameters, which can be found in the corresponding technical literature.

[0003] One of these roughness measurement parameters is the so-called "average roughness value Ra", which is a measure of the roughness of a surface as the average absolute deviation of the roughness profile from the center line in a predefinable measurement path, given for example in micrometers (μm) depending on the degree of roughness.

[0004] As mentioned above, various methods are used to reduce surface roughness depending on the application. For example, turbine vanes for aircraft turbines or land-based gas turbines used to generate electrical energy are provided with metal alloy layers, particularly MCrAlY layers, where M represents a metal such as nickel (Ni), cobalt (Co), or iron (Fe), and CrAlY (chromium, aluminum, yttrium) refers to a superalloy that is well known for this and other purposes. These layers can be applied in a vacuum chamber, for example, with a thickness of 50 μm to 250 μm, resulting in a surface roughness Ra of typically about 6 μm to 12 μm. Furthermore, it is often necessary to provide the aforementioned MCrAlY layer with a thermal barrier layer, often referred to by those skilled in the art as a TBC coating (thermal barrier coating). Such TBC coatings can be manufactured, for example, on a zirconia (ZrO2) basis. In typical cases, the thermal barrier layer is approximately 100 μm to a maximum of 500 μm thick, in particular more than 1 mm, and essentially comprises 92% ZrO2 and 8% yttrium oxide (YO2O3) for stabilization. The particle size of the particles constituting the layer can be, for example, 45 μm to 125 μm, and the porosity of the thermal barrier layer typically reaches 5% to 20%. Typical values ​​for the roughness of TBC coatings are found in the range of 9 μm to 16 μm. It should be pointed out at this point that the parameters of the aforementioned layers and their chemical composition can, in certain cases, differ considerably from the examples given above.

[0005] In general, other coatings such as TiAlN or AlTiN may still be used as alternatives.

[0006] However, the surface roughness that the layer exhibits after application to the workpiece is often unacceptable and must be reduced, for example by polishing. For example, important in the implementation of turbine vanes for land-based turbines, surface roughness values ​​Ra of up to 0.3 μm are required for aerospace applications and up to 0.8 for power generation turbines.

[0007] The required surface roughness can be achieved on MCrAlY layers, or on metal or metal alloy surfaces in general, using various methods, for example by customary abrasive blasting techniques with fine corundum, by shot peening or cut wire peening with hard steel bodies, rust-free steel bodies or ceramic blasting bodies, as well as conventional sand blasting.

[0008] In order to achieve the best possible surface quality, ie a minimum and / or uniform roughness of the material surface, various methods are available for vibration polishing in combination with polishing elements having an abrasive action.

[0009] However, most polishing of TBC layers involves only the last mentioned vibration polishing method, as they treat the surface sufficiently gently in the polishing process to avoid micro-cracking damage, spalling of surface areas or similar damage in porous TBC coatings.

[0010] To carry out vibratory polishing, two variants of polishing apparatus are widely used: the so-called rotary vibrator and the tray vibrator.

[0011] A tray vibrator is a device that essentially comprises an abrasive container containing corresponding abrasive elements and that can be vibrated by a suitable device. In the simplest case, the workpiece to be treated is placed in the abrasive container and abraded by the abrasive elements, which under vibration have an overall behavior similar to that of a viscous liquid.

[0012] Divider slides can be provided to prevent adjacent workpieces from contacting or damaging each other within the polishing chamber, and can be attached to the outside of the workpiece. Certain surface areas of the workpiece can be further protected by covering them so that only a portion of the workpiece is smoothed and / or, for example, to protect endangered edges. Summary of the Invention [Problem to be solved by the invention]

[0013] These devices known from the prior art have the drawback of producing unsatisfactory results, especially in polishing rotationally asymmetric workpieces and / or workpieces with porous surfaces, such as turbine vanes with TBC coatings.

[0014] For example, an unacceptably high level of mechanical strain may be exerted on an externally clamped workpiece being processed in a tray vibrator, which in the worst case scenario may result in damage to the workpiece and / or the surface being treated, especially porous and / or brittle surfaces. If the workpiece to be polished is placed directly in the polishing chamber of a tray vibrator according to the prior art, i.e., without external clamping, there is a risk that the workpiece may come into direct contact with the walls of the tray vibrator or any partition slides and / or adjacent workpieces, thereby making it impossible to prevent damage to the workpiece or sensitive areas of its surface, especially its edges. In particular, there is a risk that a large number of point strains may result if, for example, the distance between the workpiece surface and the adjacent boundary wall is less than two polishing elements, such that the polishing elements are jammed between the workpiece surface and the adjacent boundary wall.

[0015] It is clear that damage of the aforementioned kind can be reduced by adequately covering the critical surface areas. However, this is only possible for surface areas that do not need to be polished. Furthermore, this method is very complicated to implement, since in each case two or more surface areas must often be protected separately by appropriate coverings, which involves complex installation or removal of corresponding parts and is therefore economically inefficient. A further substantial drawback is the fact that, in particular for rotationally asymmetric workpieces such as turbine vanes for land-based applications or aircraft turbine engines, known methods result in insufficient surface roughness and / or particularly unevenly polished areas, i.e., areas on the workpiece surface with uneven roughness. For example, due to the asymmetric mass distribution of the turbine vane, the turbine vane simply rotates unevenly between the polishing elements in the polishing chamber, and the variously oriented surfaces of the turbine vane are subjected to different polishing pressures by the polishing elements during polishing, ultimately resulting in various surface areas with different surface roughnesses, or even in the event that a sufficient surface roughness is not reached at all on certain surfaces of the turbine vane. The above also applies to other respects to grinding methods in which the workpiece is externally clamped. The aforementioned drawbacks arise not only in the grinding of turbine vanes, which is described here as an example, but also in vibration grinding in general, especially in vibration grinding of rotationally asymmetric workpieces.

[0016] To at least partially overcome these drawbacks, Tanner, U.S. Pat. No. 6,817,051, discloses a vibratory polishing apparatus for workpieces having a porous surface coating, comprising a polishing container and a guide device disposed within the container for guiding and holding the workpiece within the polishing container, the guide device having first and second guide members spaced apart by at least one spacer and a retainer for positioning and holding the workpiece between the guide members, the guide device being formed and disposed within the polishing container so as to be freely movable, freely rotatable, and able to assume any position relative to the polishing container while preventing the workpiece from contacting the polishing container during polishing.

[0017] On the one hand, this is a good solution for achieving a smooth surface on the turbine vanes without damaging the edges. However, this solution has two main problems: i) Generally, many of these turbine vanes need to be polished. To fix the vanes in the guides, many manual operations are involved, which is time-consuming and makes the whole process economically unattractive. ii) The fact that the guide device is configured and arranged so that it is freely movable, freely rotatable and can assume any position relative to the grinding vessel makes the grinding process inefficient, since vibrations are only indirectly transmitted to the vanes.

[0018] SUMMARY OF THE INVENTION Accordingly, the present invention relates to a surface processing apparatus, and more particularly to a surface polishing apparatus that at least partially overcomes the above-mentioned problems. [Means for solving the problem]

[0019] The present invention is based on several principles. -Transmitting the vibrations of the vessel directly to the fixture by using a fixture directly connected to the vessel; - using a fixture in which a plurality of substrates can be arranged in a plane and oriented radially, with one end oriented at the center of a circle and the other end extending radially away from the center, all substrates being at the same distance from the center and constituting a fixed ring; - forming a fixing ring so that several fixing rings can be stacked to form a stack of fixing rings, all fixing rings of the stack having their centers on one axis forming the central axis, the stack of fixing rings being a cylindrical stack;

[0020] According to a preferred embodiment of the invention, the fixing ring is formed by disassemblable segments.

[0021] According to another preferred embodiment, the outer surface of the cylindrical stack is closed, thereby covering the outer edge of the substrate to be polished.

[0022] According to another preferred embodiment, the inner edge of the substrate to be polished is covered by an inner ring provided by the fixing ring.

[0023] According to another preferred embodiment, the outer segment comprises a lower socket base formed by a spacer portion and / or the top cover segment comprises an upper socket base formed by a spacer portion to hold and shield the base of the turbine vane mounted therebetween.

[0024] According to another preferred embodiment, the inner segments or rings carry radial extensions shaped to abut the tips of the turbine vanes for protection, preferably having a base connecting the extensions to the inner ring at their tips and shaped to match the shape and curvature of the tips of the turbine vanes attached to the segments, like the extensions of turbine blades.

[0025] According to another preferred embodiment, the segments comprise an outer surface segment arranged radially outward of an outer segment shaped such that the turbine vane base can be arranged thereon with the vanes extending radially outward and inward. The inner segment is realized to shield the inwardly extending turbine vane tips, and the outer surface segment is realized to shield the outwardly extending turbine vane tips. Optionally, either the outer surface segment or the inner segment, or both, carry radial extensions formed to abut the turbine vane tips for protection.

[0026] According to another preferred embodiment, the segments are made from thermoplastic polyurethane (TPU) materials and / or derivatives.

[0027] According to one aspect of the present invention, the cylindrical stack comprises a bottom ring, at least one fixing ring, and a closing ring. In a preferred embodiment, the bottom ring comprises at least two mandrels extending vertically and parallel to the central axis, which can be used to secure the bottom ring and the closing ring together, thereby tightly sandwiching the at least one circular ring. If the at least one circular ring is composed of separable segments, it is highly preferred to have at least two mandrels per segment, which pass through corresponding holes in the segments to hold them in place in the ring.

[0028] The invention will now be explained in more detail by way of example and with the aid of the drawings. [Brief explanation of the drawings]

[0029] [Figure 1] 1 shows a fixation ring according to the present invention; [Figure 2] 1 shows exploded segments, several of which are combined to form a fixation ring according to the invention; FIG. [Figure 3] FIG. 3 shows exploded segments similar to those shown in FIG. 2 according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a top view of the assembled segments according to FIG. 3. [Figure 5] FIG. 6 shows exploded segments similar to those shown in FIGS. 2 to 5 according to a third embodiment of the present invention. [Figure 6] 7A and 7B show assembled and disassembled configurations of a turbine vane with a mounting shoe arrangement arranged on a fixing ring according to FIG. 2, FIG. 3 or FIG. 6. [Figure 7] FIG. 10 illustrates a decomposed segment configuration according to a fourth embodiment of the present invention. [Figure 8] FIG. 2 is a cutaway view of an assembled cylindrical stack according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] A turbine vane has a base with a blade on top, the end of the blade furthest from the base is commonly called the tip of the blade.

[0031] FIG. 1 shows a stationary ring 101 according to the invention, constructed from seven segments 103, 105, 107, 109, 111, 113, and 115. Turbine vanes (shown in dashed lines) are placed in these segments, oriented so that the base is farthest from the center of the ring and the blade tips are closest to the center of the ring. The base is covered by the outer ring of the stationary ring, and the tip blades are covered by the inner ring. The remaining blades are freely accessible from above and below. FIG. 1 shows a stationary ring that is only partially loaded with turbine vanes, specifically only segments 103 and 105. The figure also shows several guide lines from the ring center to some of the turbine vanes, indicating their radial orientation.

[0032] 2 shows an exploded view of segment 201, including a carrier segment 203 and a top cover segment 221. The carrier segment is loaded with three turbine vanes, shown in dashed lines. A fourth turbine vane is also shown in dashed lines, loaded within carrier segment 203.

[0033] The carrier segment 203 comprises an outer segment 205 and an inner segment 207, which form an outer ring and an inner ring when the segments are assembled to the fixed ring. The outer segment 205 and the inner segment 207 are fixed together by segment end plates 209 and 211. To increase the stability of the carrier segment 203, two connecting arms 213 and 215 are used to further stabilize the outer segment 205 and the inner segment 207. Furthermore, the carrier segment 203 comprises at least two holes 217 (in FIG. 2, the second hole 217 is not visible because it is behind the turbine vane already loaded on the carrier segment). These holes allow the mandrel of the bottom ring to penetrate the segment 201, so that the segment can be accurately positioned by so-called skewering. Furthermore, the carrier segment comprises at least two screw holes 219 (in FIG. 2, the second screw hole 219 is not visible because it is behind the turbine vane already loaded on the carrier segment). These screw holes are used to secure the top cover segment 221 onto the carrier segment 203 using screws 223 and 225 .

[0034] The outer ring 205 of the support segment 203 is formed so that a turbine vane can be placed thereon. The shape may be, for example, a step shape for placing the base of the turbine vane thereon. In other words, the shape of the outer ring 205 is adapted to the shape of the base of the turbine vane.

[0035] The inner ring 207 of the carrier segment 203 has the main function of shielding the blade tips. It may be an unstructured surface that the blade tips simply contact when loaded onto the carrier segment 203.

[0036] When the top cover segment 221 is fixed to the carrier segment 203, it serves to firmly fix the turbine vane loaded in the carrier segment 203. Therefore, the shape of the top cover segment 221 is also adapted to the shape of the base of the turbine vane. To attach the top cover segment 221 to the carrier segment 203 loaded with the turbine vane, the top cover segment 221 is provided with holes 227 and 229 that correspond to the screw holes 219 of the carrier segment 203.

[0037] The top cover segment 221 further comprises at least two holes 231 and 233. These holes are used to allow the mandrel of the bottom ring to pass through the segment 201 and to accurately position the segment in a so-called skewered manner.

[0038] When the carrier segment 203 is loaded with the turbine vane and the top cover segment 221 is attached to it, the turbine vane body is clamped between the carrier segment 203 and the top cover segment 221 and is therefore firmly fixed and completely covered. Furthermore, the blade tips are covered by the inner ring 207 of the carrier segment 203. However, the turbine vane blades are completely accessible from the top and bottom, so that for example abrasive material can reach the respective surfaces without obstructions.

[0039] Figures 3 and 4 show a second embodiment according to the invention. Apart from the components and features already described in relation to Figure 2, this segment 201 also comprises a carrier segment 203 and a top cover segment 221, both having several spacer portions 204, 222. In the carrier segment 203, they form a lower socket area 206 in the outer segment 205.

[0040] The top cover segment 221 includes a spacer portion 222 for forming an upper socket area 224. The lower socket area 206 and the upper socket area 224 form a two-part socket for encasing the foot of a turbine blade when the carrier segment 203 and the top cover segment 221 are assembled with the turbine blade mounted therebetween.

[0041] Furthermore, the inner segment or inner ring 207 of the carrying segment 203 carries a protective extension 208 that extends radially in the direction of the attached turbine blade and preferably conforms to the shape and curvature of the blade such that the extension widens inward towards the inner ring.

[0042] A third embodiment of the segment 201 (FIG. 5) provides further protection and support for the turbine blade. In addition to the spacer portions 204 and 222 that form the lower and upper socket areas 206 and 224, lower and upper cutouts 210 and 226 can be formed to allow the blade feet to be pressed into the lower and upper socket gaps 206 and 224 when the carrier segment 203 and the top cover segment 221 are attached and fixed together.

[0043] In addition to these socket areas 206 and 224, an additional thin-walled shell 226 can be provided (FIG. 6) that protects the foot of the blade like an additional protective sock. These two shells 226 are very thin and conform to the shape of the foot of the blade. They are preferably made of a resilient yet strong material, such as TPU or similar, that allows a resilient yet very robust fixation of the turbine blade between the carrier segment 203 and the top cover segment 221.

[0044] 7 shows a fourth embodiment of the segment 401, which allows a double-circle arrangement of blades in a carrier 403. The carrier segment 03 comprises an outer segment forming a central mounting ring 05 having a lower socket area 406, an inner segment ring 407 extending radially inward to protect the tips of the attached blades, and an outer surface segment forming an outer segment ring 409 extending radially outward to protect the tips of the attached blades. A top cover segment 421 can be fixed to the segment 403 by screws.

[0045] To provide a strong yet resilient containment of the turbine blade during sharpening, the segments are preferably made from a strong yet resilient material, such as thermoplastic polyurethane (TPU) materials and derivatives.

[0046] 8 is a cutaway view of an assembled cylindrical stack 301 according to the invention. Cylindrical stack 301 comprises bottom ring 303, first, second, third and fourth locking rings 305, 307, 309 and 311, and closing ring 313. Bottom ring 303 is completed by adding dashed lines to the cutaway view, thereby showing mandrels, such as 315 and 317, that allow the individual segments to be loaded onto bottom ring 303 and to align them with the locking rings.

[0047] The closure ring 313 is then placed on top of the stack of bottom and fixing rings and secured with screws. A central shaft is provided in the center of the stack, and the bottom and closure rings are connected to this central shaft via arms.

[0048] The entire stack can then be secured to a vibrating vessel and the setup can be used as a trayed and / or rotating system. [Explanation of symbols]

[0049] 101 Fixing ring 103, 105, 107, 109, 111, 113, 115 segments 201 segments 203 Supported Segments 205 outer segment (outer ring) 207 Inner Segment (Inner Ring) 209,211 Segment end plate 213,215 Connecting arm 217 holes (for mandrel) 219 screw hole (for screws) 221 Upper lid segment 223,225 Screws 227,229 holes (corresponding to screw hole 219) Holes 231, 233 (corresponding to hole 217) 301 Cylindrical laminate 303 Bottom Ring 305, 307, 309, 311 Fixing ring 313 Closure ring 315,317 Mandrel 204,222 Spacer part 206 Lower Socket Area 224 upper socket area 208 Extension 210,226 Upper and lower notches 226 Shell 401 segments 403 Support (support segment) 405 Central Mounting Ring (Outer Segment) 406 Lower Socket Area 407 Inner Segment Ring 409 Outer Segment Ring 421 Upper lid segment

Claims

1. A segment of a fixture for a turbine vane having a base and an upper blade, said fixture comprising several such segments arranged to form a fixing ring, said segments comprising a carrier segment and a top cover segment; the carrying segments comprise outer and inner segments that form outer and inner rings when the segments are assembled into a fixed ring; the outer segment is shaped to fit the shape of the base of the turbine vane so that the turbine vane can be placed thereon, and the inner segment is realized to shield the blade tips of the turbine vane; segment.

2. 10. The segment of claim 1, wherein the outer segment includes a lower socket gap formed by a spacer portion and / or the top cover segment includes an upper socket gap formed by a spacer portion, formed to retain and shield the base of the turbine vane.

3. The segment of claim 1 , wherein the inner segment carries a radial extension configured to abut the tip of the turbine vane for protection.

4. 4. The segment of claim 3, wherein the radial extension has a base portion connecting the extension to the inner ring and a tip portion formed to match the shape and curvature of the tip of the turbine vane attached to the segment, such as an extension on a turbine blade.

5. 2. The segment of claim 1, comprising an outer surface segment disposed radially outward of the outer segment, the outer segment shaped to allow the turbine vanes to be disposed thereon with the vanes extending radially outward and radially inward, the inner segment realized to shield the inwardly extending tips of the turbine vanes, and the outer surface segment realized to shield the outwardly extending tips of the turbine vanes.

6. The segment of claim 1 , wherein the segment is made from thermoplastic polyurethane (TPU) materials and derivatives of thermoplastic polyurethane.

7. A fixing ring formed by segments according to any one of claims 1 to 6, characterized in that means are envisaged which allow for releasable fixing of two or more rings which are stackable on top of one another.

8. 8. A cylindrical stack of retainer rings according to claim 7.

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