IL226953A - Device designed for clamping a turbine blade - Google Patents

Description

Device designed for clamping a turbine vane The invention relates to a device that is designed for clamping a turbine vane. By means of the device that has the turbine vane and forms a unit with it, the turbine vane can be clamped or respectively inserted into the clamping device of a treating apparatus in order to treat the ends of the turbine blade. The invention also relates to an associated, prepared turbine vane. Turbine vanes are manufactured from metal alloys. In order to submit the turbine vane which is a cast iron body that is subject to several tolerances for treatment, in particular grounding, satisfying optimal precision regarding the surface and shape, there are special requirements for clamping the workpiece.

Clamping units are known that are formed by a voluminous clamping block and a turbine vane cast therein. For example, a clamping block is manufactured as a metal casting block, wherein low-melting metal alloys are used as the casting material. This material is soft and correspondingly sensitive to mechanical damage. Consequently, the mechanical clamping of the clamping block is not sufficiently rigid. It is very extravagant to separate the metal casting block from the turbine vane. A great deal of energy must be supplied to reach melting points above 130°C to separate the casting blocks. Furthermore, according to DE-A1-3439 250, a clamping block made of filled plastic is known that encases the turbine blade. The plastic body can be over-moulded onto the turbine blade. The plastic body is particularly voluminous and as such is subject to significant shrinkage. Rigidity is also sacrificed due to the plastic material which consequently impairs the desired clamping, and the precision requirements cannot be reliably satisfied.

Consequently, the aims of the invention are to arrange a clamping for a turbine vane to be treated in such a manner that the rigidity of the clamping significantly improves in order to obtain precise treatment by reliably freeing the turbine blade from influences to which it is sensitive as a workpiece, such as influence of surface indentations and deformations, when clamping it. Complex auxiliary clamping means are to be eliminated. 13763 drad as filed A device according to the invention mentioned hereinbefore is characterized in that the device is formed by a clamping unit having at least two clamping block parts forming a clamping block that enclose the turbine vane with a turbine blade shell formed from a plastic shell layer that remains at least substantially dimensionally stable under clamping force and at least substantially accommodates the turbine blade over its axial length and at least substantially surrounds it in a positive-fitting manner at its profile contour and can be separated from the turbine blade, wherein on a concave underside of the turbine blade and convex upper side of the turbine blade, the plastic shell layer has outwardly exposed patrix surfaces that are defined by a three-dimensionally structured patrix profile forming a relief, and in that the clamping block parts each have a matrix surface on an inside which is defined by a three-dimensionally structured matrix profile forming a relief, wherein the patrix surfaces and matrix surfaces are formed as associated complementary surfaces that correspond to one another and create a reference and clamping engagement. According to the invention, two clamping block parts are preferably provided that will be termed clamping block halves in the following and form, on the one hand, a concave matrix surface and, on the other hand, a convex matrix surface.

Aims of the invention are also achieved in that a turbine vane comprising an axially extending turbine blade and tip shrouds optionally formed on its ends is designed as a part that can be inserted into said device such that the turbine blade is surrounded by a removable turbine blade shell that completely or at least substantially encloses the turbine blade at its profile contour at least substantially over its axial length and accommodates it in a positive-fitting seat and is formed from a shell layer that is made of plastic and remains dimensionally stable under clamping force, wherein the plastic shell layer has outwardly exposed patrix surfaces on a concave underside of the turbine blade and a convex upper side of the turbine blade, the surfaces (8) are each defined by a three-dimensionally structured patrix profile forming a relief, extend over the entire peripheral surface and axial length of the turbine blade shell and are designed for a reference and clamping engagement in associated complementary matrix surfaces of clamping block parts of said invention. 13763 drad as filed The device according to the invention is formed by a multi-part clamping unit that can be clamped in the clamping device of a treating apparatus. According to the invention, the turbine blade to be clamped is designed with a patrix surface defined by a threedimensionally structured patrix profile forming a relief on the concave underside of the turbine blade forming its suction side, as well as on its convex upper side of the turbine blade forming the pressure side. In combination therewith, it is important for the turbine blade shell to be designed as a relatively thin shell layer made of plastic with a jacket profile corresponding to the cross-sectional profile of the leaf-shaped turbine blade formed by the concave and convex contour, i.e., having an equivalent shape with the turbine blade. It is particularly preferable for the turbine blade shell to be provided as a plastic jacket moulded on onto the turbine blade. The positive-fitting seat is to be understood as a gap-free and play-free positive-locking seat, possibly subjected to minimal plastic shrinkage while being manufactured, that immovably embeds the turbine blade in the plastic shell in every direction.

Forming the turbine blade shell from plastic also has the particular advantage that the plastic shell functions as a damping layer in the clamped clamping unit which reduces vibration from machining. The profiled surface extends substantially over the entire axial length of the turbine blade. That is, the ends of the turbine blade, if at all, remain free of the patrix surface at the transitional area to the front heads or ends that can have shaped tip shrouds. The patrix surface therefore extends continuously over the turbine blade with a pattern consisting of surface shapes determined by differences in height.

The patrix surface is therefore formed by a three-dimensional surface pattern that has elevations and recesses like a raster and/or wave structure. The matrix surfaces of the clamping block halves are formed complementary to the patrix surfaces. Patrix and matrix are understood to be positive and negative moulds that precisely mesh with each other in a positive-locking manner without play. Patrix and matrix belong to each other and correspond with each other over the entire pattern surface. This yields surfaces creating a reference and clamping engagement over said axial length. These mesh with each other like a key/lock structure in the clamping unit. Defined contact surfaces and measuring points are achieved for positioning the turbine vane to be treated as a blank with maximum precision. 13763 drad as filed In the clamping unit according to the invention, the turbine blade is positioned clamped in a positive-locking manner and in three axial directions by means of the layer-forming plastic jacket. The plastic remains dimensionally stable under clamping force even after the jacket is created. Since the turbine blade is preferably completely enclosed in a positive-fitting seat with the turbine blade shell made of plastic, no point of the turbine blade surface is directly clamped, only the plastic layer. Another advantage of the substantial clamping rigidity is in particular that high cutting performances are possible when machining the ends of the turbine vane. Overall, a clamping system is achieved with the device according to the invention that is easy to manufacture and handle, compactly built, economical to operate without expending significant energy, scarcely subject to wear, offers significant clamping rigidity and protects the turbine vane from harmful influences while clamping such as indentations and deformation. The thin-layer turbine blade shell made of plastic can be easily removed mechanically as such from the turbine blade without damaging it.

Both matrix profiles advantageously have three dimensionally structured shapes that yield a distinct, three-axis position of the turbine vane when meshed with corresponding, complementary shapes in the associated patrix surfaces of the turbine blade.

The matrix surfaces, and correspondingly, the patrix surfaces advantageously have three-dimensional surface patterns designed as substantially continuous height and depth contour lines over the axial length in the form of elevated and recessed longitudinal edges. Such patterns have groove or furrow-like structures. A stair-shaped outer contour of the turbine blade shell has proven particularly advantageous, wherein the matrix profiles and patrix profiles have stair- shaped steps extending the axial length of clamping. At least over part of the profile of the turbine blade, these form a stepping perpendicular to the longitudinal axis of the turbine blade. In a preferred design, the stair-like steps have an at least substantially rectangular stair profile. Step surfaces are also advantageous that are designed as parallel step surfaces aligned at least substantially perpendicular to the dimension of the turbine blade depth. In particular, the first step surfaces are equally spaced by means of second step surfaces at a right angle to them. 13763 drad as filed A particularly optimum distribution of clamping force on the plastic layer forming the turbine blade shell is achieved with the invention. In general, it is particularly advantageous when strip-like parallel first surfaces are formed in axial direction that are parallel with clamping surfaces of the clamping block parts, or respectively with corresponding contact surfaces of a clamping device coming into contact with such clamping surfaces. First step surfaces can be advantageously formed at least partially with a step width that changes over the axial step length. The patrix and matrix surfaces can also be formed partially or completely by spatial surface patterns with island-like structures such as for example crater-like elevations and recesses.

According to one embodiment, a special directional structure of the spatial surface pattern can be formed in that at least one matrix surface with an associated patrix surface has at least a tongue or bay-like shape that extends in the axial direction of the axial clamping length. Such shapes or other axial shapes can advantageously form a stepping in the axial direction.

The matrix surfaces can be interrupted by at least one recess aligned transverse to the longitudinal axis of the associated clamping block half that is designed to be narrow in comparison to the axial length of the matrix surface and forms a pocket for load and pressure distribution.

In one embodiment of the invention, the clamping block halves with the matrix surfaces can be designed as mould duplicates of injection moulds that serve to produce the turbine blade shell as a thin-layer plastic part that is injection-moulded onto the turbine blade. This makes the clamping block parts particularly easy and economical to manufacture. The mould duplicates of the clamping block parts can be formed allowing for and incorporating a shrinkage factor that, if applicable, due to the very thin plastic shell layer produced in the injection moulding process, corresponds to very minor shrinkage of the injection-moulded hardened patrix surfaces relative to the dimensions of the injection mould to adapt the dimensions.

In order to form the clamping system according to the invention, the turbine blade shell has a small thickness defined by only a few millimetres. Consequently, since the 13763 drad as filed advantageously very small shrinkage of the material of the turbine blade shell manufactured by injection moulding is constant and known, the aforementioned adaptation of the shape of the matrix surfaces of the clamping block halves can be reliably performed to a specific extent.

In a particularly preferred design, the turbine blade shell is made of thermoplastic plastic injection-moulded onto the turbine blade. Such a jacket can be easily produced with conventional injection moulding machines that advantageously only experience minor injection pressure for the purposes of the invention. The advantage of thermoplastic plastics is that they can be precisely configured to the desired requirements, wherein in particular, dimensional stability is reliably retained even under high clamping pressure. The thermoplastic plastics can be used to mould the particularly thin- wall plastic jackets with finely structured profiles. Another advantage is that the thermoplastic plastic of the turbine blade shell can be provided for re-use in a technically easy and economical manner after removing the shell.

In one embodiment of the turbine blade jacket, the turbine blade shell is formed with at least one weak region, in particular in the form of an attenuation/partition line to form a predetermined breaking point for breaking open and removing the turbine blade shell from the turbine blade. Such predetermined breaking points can be easily produced and handled since the turbine blade shell is formed to be thin in the first place. Elements of the patrix profile can be used to form a breaking-open shape at at least one predetermined breaking point for introducing force to break open the turbine blade shell.

Dependent claims relate to the named and further practical and advantageous embodiments of the invention. Each partial feature of an exemplary embodiment is to be considered a partial feature of other embodiments that are not described. Only particularly practical and advantageous embodiments and possibilities of the invention will be described in more detail on the basis of the following description of the exemplary embodiments shown in the schematic drawing.

In the figures 13763 drad as filed Fig. 1 A to 1C show plan views and profile views of sections of a clamping unit according to the invention, Fig. 2A to 2D show axonometric and sectional views of the clamping unit from Fig. 1 in a clamping device of a treating apparatus, Fig. 3 A to 3E show an axonometric view and sectional views of a concave clamping block half of the clamping unit of the device according to Fig. 1 and 2, and Fig. 4 A to 4E show an axonometric view and sectional views of a convex clamping block half of the clamping unit of the device according to Fig. 1 and 2.

A clamping unit 5 can be seen in Fig. 1 A to C that forms a device for inserting a turbine vane 6 to be machined as a blank into a treating apparatus. A clamping device 1 of such a treating apparatus (otherwise not shown) can be seen in Fig. 2A to 2C.

The clamping unit 5 comprises two clamping block halves 31, 32 forming a clamping block 3, as well as the turbine vane 6 accommodated therebetween. It has an axially elongated turbine blade 61 as well as tip shrouds 62, 63 formed on its ends. The turbine vane 6 is a workpiece to be machined with an exposed outer contour. In the exemplary embodiment, the turbine vane 6 is a rotor blade of an airplane turbine that is formed from a high-strength material, that is, a special metal alloy. The turbine vane 6 is a single-piece shaped part that requires particularly precise grinding of the front ends, in this case, the tip shrouds 62, 63, to produce it. These need to be ground with a grinding machine (treating apparatus) with maximum precision, wherein high grinding pressure may be exerted on the workpiece during the grinding process. The tolerances of the turbine blade prevent the entire surface from being directly clamped. By means of the clamping unit 5 according to the invention, the turbine vane 6 is not subject to damaging clamping forces, wherein the turbine blade in the clamping unit 5 that indirectly holds it 13763 drad as filed is nonetheless enclosed in a positive-locking manner and thereby integrated in a compound structure ensuring maximum clamping rigidity.

As can be seen in Fig.lA to C, the turbine blade 61 is encompassed over its axial length with a single-piece turbine blade shell 7 forming a jacket that is formed by a thin-plastic shell layer. The turbine blade shell 7 extends over the entire length of the turbine blade 61 with the exception of areas at the ends of the turbine blade 61 that are short in comparison to the length of the turbine blade. The thin-plastic shell layer is moulded onto the turbine blade 61 in an injection moulding process. Such injection moulding can be produced using conventional injection moulding machines. An example is disclosed wherein the turbine blade shell 7 completely encloses the profile of the turbine blade 61; the turbine blade shell 7 is formed by a part with a closed perimeter in which the turbine blade 61 is located in a fixed, tight seat in a positive-locking manner. The cross-section of the contour of profile of the turbine blade shell 7 is leaf-shaped with a convex and concave curvature corresponding to the contour of the turbine blade 61.

In general, special features of the thin-layer turbine blade shell 7 according to the invention are found in particular in the special structure of its outwardly exposed shell surface.

On a concave turbine blade underside 611, the turbine blade shell 7 has a thin wall due to layer formation, i.e., having only a very thin layer thickness, in which is formed an outwardly exposed three-dimensional structured surface, that is, a structured surface termed a patrix surface 801 in the following. In the same manner, a patrix surface 802 is formed on a convex turbine blade upper side 612 in the equally thin-layered turbine blade shell 7. The entire surface of the two patrix surfaces 8 is each defined by threedimensionally structured patrix profiles 81 forming a relief, that is, by a patrix profile 811 on the concavely curved side, and a patrix profile 812 on the convexly curved side. They extend over the entire perimeter and the axial length of the turbine blade shell 7.

In the exemplary embodiment, the two patrix profiles 81 have stair-shaped steps 82 extending in the axial length of clamping. 13763 drad as filed As can be seen in Fig. 2A to 2D, the clamping block halves 31, 32 of the clamping block 3 each have a structured surface on their inside facing the turbine blade 61 that also forms a three-dimensional surface pattern. This forms matrix surfaces 4 that are each defined by a three-dimensionally structured matrix profile 41 forming a relief, that is, the matrix surface 401 with the matrix profile 411 on the concave turbine blade underside 611, and the matrix surface 402 with the matrix profile 412 on the convex turbine blade upper side 612. The patrix surfaces 8 and the matrix surfaces 4 each belong in pairs to the turbine blade underside 611 and turbine blade upper side 612. It is also possible for a least one of the clamping block halves to be divided into a plurality of clamping block parts. That is, at least two clamping block parts can be provided which form a correspondingly divided matrix surface on the convex and/or concave side of the turbine blade 61.

In the clamping unit 5 with joined parts, the patrix surfaces 8 engage in the matrix surfaces 4 in a positive-locking manner such that, in a clamped state, a full-surface reference engagement that precisely fixes the clamped position and a full-surface clamping engagement are created. The patrix surfaces 8 and matrix surfaces 4 are associated surfaces that correspond to one another and are complementary with corresponding dimensions, that is, forming a positive part on the one hand, and an associated, precisely fitting negative part on the other hand.

Fig. 2 A to 2D disclose the clamping device 1 for receiving or clamping the turbine vane in the treating apparatus with a simple design having a main body 2, a stationary clamping jaw 21 as well as a movable clamping jaw 22. The clamping block half 31 is firmly connected and precisely positioned for example by means of a screwed connection to the clamping jaw 21. The other clamping block half 32 is likewise connected to the movable clamping jaw 22. According to Fig. 2A to 2C, the clamping device 1 can be seen as an open clamping unit 5 that is depicted with all its parts, that is, the clamping block halves 31, 32 and the turbine vane 6 with the turbine blade shell 7.

A clamping device 1 which is only disclosed as an example in Fig. 2A to 2C can be a part of any known treating apparatus that is equipped with cutting tools for machining the free ends of the turbine vane 6 of the clamping unit 5. 13763 drad as filed In the following, the structure of the matrix surface 401 of the clamping block half 31 will be further described with reference to Fig. 3A to 3E.

Viewed in profile cross-section, the matrix surface 401 of the clamping block half 31 forms a concave enclosure that corresponds with the convex turbine blade upper side 612. The matrix profile 41 according to Fig. 3A to 3E has stair-shaped steps 42 extending in axial length of clamping. As can be seen in particular in Fig. 3E and 3D, the steps 42 are rectangular with a stair profile. First step surfaces 421 which are parallel are aligned perpendicular to a dimension 45 corresponding to the depth dimension 85 of the turbine blade depth (Fig. IB). The depth dimension 45 is defined as the entire stair height between a low-lying stair bottom edge 451 and a high-lying stair top edge 452. A floor surface 450 on the low-lying stair bottom edge 451 corresponds to a secant area 850 that can be seen in the concave area and neighbours the one longitudinal edge of the turbine blade 61 as can be seen in Fig. IB. Extending between the first step surfaces 421 are second step surfaces 422 with the same step height. The parallel first step surfaces 421 are parallel to clamping surfaces 313, 323 of the clamping block halves 31, 32 which apply clamping force (in particular Fig. IB, 2A-2D).

As can be seen in particular in Fig. 3B, the first step surfaces 421 have step widths 423 that change over the axial length of the step. As can be seen in Fig. 3A to 3E, the step surfaces 421 are narrow over the majority of the stair height, wherein in the bottom stair height area neighbouring the stair floor surface 450, larger step widths are formed, that is, by steps that have a tongue or bay-shaped shape 43. In the exemplary embodiment, three such elongated shapes are formed. These are axially offset such that a stepping is also formed in the axial direction in this region. This axial stepping lies between the above-described peripheral stepping and a lower peripheral stepping 46 opposed to and designed in the same manner with step surfaces being parallel to the clamping surfaces 313, 323.

As can be seen from Fig. 3A and 3B, shapes 44 in the form of projections and recesses alternately arranged over the clamping length are formed in the low-lying, that is, low region of the clamping block half 31. 13763 drad as filed The other clamping block half 32 of the clamping unit 5 is portrayed in Fig. 4A to 4E.

View in its profile, this clamping block half 32 has a convex shape over a stair height 45' that corresponds to the concave turbine blade underside 611 and is designed to engage in this underside. The matrix surface 402 is correspondingly designed as with the matrix surface 401 of the first clamping block half 31. The correspondence is that the steps 42 and step surfaces 421, 422 are designed like the clamping block half 31 with the difference that an outer curvature is formed in the clamping block half 32 instead of the inner curvature of the clamping block half 31. A high-lying surface 450' is correspondingly present which, in the clamping unit 5, opposes the floor surface 450 of the clamping block half 31 on the shell surface. The stair height 45' is defined by the height of the stair between a high-lying stair upper edge 451' on the step surface 450' and a low-lying stair bottom edge 452'. The stair height 45' corresponds to the depth dimension 85 of the turbine blade 61.

As can be seen from Fig. 4A to 4E, the steps 42 with tongue or bay-shaped shapes 43 lie on the high-lying upper side of the clamping block half 32 defined above. The steps 42 with the narrow step surfaces that have changing step widths follow the tongue or bay shaped steps and form the majority of the entire stair height. The steps having the first parallel step surfaces 421 with a changing step width 423 and the second step surfaces 422 with the same width are designed corresponding to the step surfaces and step widths, being denoted alike, of the first clamping block half 31.

As described above, the patrix surfaces 8 and matrix surfaces 4 are correspondingly designed with positive or negative spatial surface patterns. The description of the structures of the matrix surfaces 4 therefore likewise applies to the structures of the equivalent and complementary patrix surfaces 8. As shown in Fig. IB and 2D, the patrix surfaces 8 also correspondingly comprise first parallel step surfaces 821 with a changing step width 823, second step surfaces 822 to form equal step heights, tongues 83, shapes 84 and a low stepping 86.

The clamping block halves 31, 32 depicted with their matrix surfaces 4 in Fig. 3 A to 3 E and Fig. 4A to 4E can be manufactured as mould duplicates of injection moulds (not shown) of an injection moulding machine (not shown) known per se by means of which 13763 drad as filed

Claims (10)

Claims:

1. A device designed for clamping a turbine vane, characterized in that the device is formed by a clamping unit having at least two clamping block parts forming a clamping block that enclose the turbine vane with a turbine blade shell formed from a plastic shell layer that remains at least substantially dimensionally stable under clamping force, that at least substantially accommodates the turbine blade over its axial length and at least substantially surrounds it in a positive-fitting seat at its profile contour and can be separated from the turbine blade, wherein on the concave underside of the turbine blade and convex upper side of the turbine blade, the plastic shell layer has outwardly exposed patrix surfaces that are respectively defined by a three-dimensionally structured patrix profile forming a relief, and in that the clamping block parts each have a matrix surface on an inside which is defined by a three-dimensionally structured matrix profile forming a relief, wherein the patrix surfaces and matrix surfaces are formed as associated complementary surfaces that correspond to one another and create a reference and clamping engagement.

2. Device according to claim 1 , characterized in that both matrix profiles have three-dimensionally structured shapes that yield a distinct, three-axis position of the turbine vane in mutual engagement with corresponding, complementary shapes in the associated patrix surfaces of the turbine blade.

3. Device according to claim 1 or 2, characterized in that the matrix profiles and patrix profiles have stair-shaped steps extending in the axial length of clamping.

4. Device according to claim 3, characterized in that first step surfaces that are aligned substantially perpendicular to the dimension of the turbine blade depth are designed as parallel step surfaces.

5. Device according to claim 3 or 4, characterized in that the first step surfaces are designed at least partially with a step width that changes over the axial step length. 13763 drad as filed

6. Device according to any one of claims 1 to 5, characterized in that at least one of the matrix surfaces with an associated patrix surface has shapes that extend axially in the direction of the axial length of clamping and form a stepping in the length of clamping.

7. Device according to any one of claims 1 to 6, characterized in that the matrix surfaces are interrupted by at least one recess that is aligned transverse to the longitudinal axis of the associated clamping block parts and is designed narrow in comparison to the axial length of the matrix surface and forms a pocket for distributing load and pressure.

8. Device according to any one of claims 1 to 7, characterized in that the clamping block parts with their matrix surfaces are formed as mould duplicates of injection moulds that serve for manufacturing the turbine blade shell as a plastic part injection-moulded onto the turbine blade.

9. Device according to claim 8, characterized in that the matrix surfaces of the mould duplicates are designed incorporating a shrinkage factor of the injectionmoulded, hardened patrix surfaces relative to the dimensions of the injection moulds with dimensions adapted to correspond to the shrinkage.

10. A turbine vane, that is designed as a part insertable into a device according to any one of claims 1 to 9, characterized in that the turbine blade is surrounded by a removable turbine blade shell that encloses the turbine blade at its contour profile at least substantially over its axial length and accommodates it in a positive-fitting seat, and is formed from a shell layer that is made of plastic and remains dimensionally stable under clamping force, wherein the shell layer has outwardly exposed patrix surfaces on a concave underside of the turbine blade and convex upper side of the turbine blade, the surfaces are each defined by a three-dimensionally structured patrix profile forming a relief, extend over the entire peripheral surface and axial length of the turbine blade shell, and are 13763 drad as filed