CA2988229A1 - In situ additive fabrication process for a coating on a turbine engine casing - Google Patents

Abstract

A method of in situ additive coating manufacturing comprising depositing on a inner surface of a turbomachine casing a filament of an abradable material along a predefined deposition path to create a three-dimensional scaffold of filaments forming an ordered network of channels therebetween a method in which a filament material deposition system is positioned at a position and a determined distance from the inner surface of the casing; a first layer of the coating is deposited over 360 °; a rotation of the filamentary material deposition system is performed at a first determined angle and the filamentary material deposition system is positioned at a position and a determined distance from the deposited layer; a second layer of the coating is deposited on the first layer of the coating, on a sector of the housing; a displacement is made of a determined angular difference corresponding to the first sector already covered then for the following sectors up to cover 360 °; and after rotating the filamentary material deposition system by a determined second angle, the process is resumed for subsequent layers until a desired coating thickness is achieved. Figure 7

Description

Process for the in situ additive manufacturing of a coating on a crankcase turbine engine Background of the invention The present invention relates to the general field of manufacture of parts made of polymer material, in particular thermosetting material, of parts metal alloy or ceramic alloy by additive manufacturing and she more particularly, but not exclusively, the manufacture of abradable coatings with acoustic functionalities, in particular for blower housing.
The control of noise pollution from aircraft around airports has become a public health issue. Standards and regulations of more and more severe are imposed on aircraft manufacturers and managers airports. Therefore, build a silent plane became over of the years a striking selling point. Currently, the noise generated by aircraft engines is mitigated by acoustic reaction coatings localized which can reduce the sound intensity of the engine on one or two octaves on the principle of Helmholtz resonators, these coatings presenting conventionally in the form of composite composite panels a rigid plate associated with a honeycomb core covered with a skin perforated and arranged at the level of the nacelle or propagation ducts upstream and downstream. However, in new generation engines (eg in turbofan engines), areas available for coatings acoustics are reduced considerably as in the UHBR technology (Ultra-High-Bypass-Ratio). In addition, these areas of casings in composite material are likely to have defects in shape that should be made up for by an additional machining operation before putting in place of the coating.
It is therefore important to propose new processes and / or new materials (including porous materials) to eliminate

2 or significantly reduce the level of product noise generated by aircraft engines especially in the take-off and landing phases and on a Frequency range wider than currently, including low frequencies while maintaining engine performance. This is the reason why we is now looking for new noise reduction technologies for reduce this nuisance and new treatment surfaces acoustically and this with minimal impact on the other functionalities of the engine as the specific fuel consumption that constitutes a significant business advantage.
However, within the aircraft engines, the noise from the fan is a first contributors to the noise nuisances favored by the increase of the dilution rate that these new generations of aircraft are looking for.
Moreover, it is now common and advantageous to resort to additive manufacturing processes in place of processes traditional foundry, forging or machining in the mass to achieve easily, quickly and cheaply complex three-dimensional parts. The aeronautics is particularly suitable for use of these processes. Among these, there may be mentioned, for example, the deposition process Wire Beam Deposition.
Object and summary of the invention The present invention aims to propose a method of formatting of a new abradable material, which also makes it possible to reduce significant the noise generated by aircraft turbojets and in particular that generated by the blower-OGV assembly. An object of the invention is also to to make up for the defects of form resulting from the composite nature of the substrate sure which this abradable material is intended to be deposited.
For this purpose, there is provided a method of manufacturing in situ coating depositing on an inner surface of a turbomachine casing a filament of an abradable material according to a predefined deposit path to to create a three-dimensional scaffold of filaments forming between them a

3 an ordered network of channels, the method being characterized by the steps following:
position a filament deposition system at the level of a longitudinal axis of said housing to a position and a determined distance relative to said inner surface of said housing, deposit a first layer of said coating on the 3600 of the circumference of said housing by a relative circumferential movement between said casing and said filamentary material deposition system, rotate said filament deposition system of a first determined angle and position said deposit system of filamentary material at said longitudinal axis of said housing to a position and a determined distance from said first layer said coating, deposit on a sector of said casing by a relative axial displacement between said housing and said filament deposition system, a second layer of said coating on said first layer of said coating, relative circumferential movement between said housing and said system for depositing filamentary material with a determined angular difference corresponding to the first sector already covered when the said second layer of coating, and repeat the deposition step on said crankcase area and the step of relative circumferential displacement according to said angular difference determined for the following sectors up to cover the 360 of the circumference of the casing, and after rotating said material deposition system filamentary of a determined second angle, repeat all the steps previous, with the exception of the first, for subsequent layers up to obtain a desired coating thickness.

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4 Thus, a porous microstructure with regular porosity is obtained and ordinate which ensures a significant absorption of acoustic waves by visco-thermal dissipation within the channels.
Preferably, prior to depositing said first layer said coating is deposited a layer of a play catching material to obtain a deposition surface of known geometry.
Advantageously, the filing of filamentary material is carried out by a plurality of ejection nozzles whose vertical positioning of each said ejection nozzles are independently adjustable.
According to the embodiment envisaged, said step of rotation of said filament deposition system is performed twice by successive rotation of 900, the first determined angle being equal to 900 or said step of rotation of said filament deposition system is performed as many times it There are definite directions of orientation of the different filaments. More particularly, said step of rotating said filament deposition system is performed six times by successive rotation of 30, the first determined angle being equal to 30.
Preferably, additional layers of said coating are added locally to account for non-axisymmetric geometry casing.
Advantageously, the filing of filamentary material is carried out by a plurality of ejection nozzles whose vertical positioning of each said ejection nozzles are independently adjustable.
Preferably, said casing is a turbomachine fan casing made of woven composite material.
The invention also relates to a material deposition system filament for the implementation of the aforementioned method and a coating abradable turbomachine wall obtained from the above method.
Brief description of the drawings

5 Other features and advantages of the present invention will emerge from the detailed description below, with reference to figures following, which are devoid of any limiting character and on which:
FIG. 1 schematically illustrates an architecture of aircraft turbomachine in which is implemented the method of in situ manufacture of coating according to the invention, FIG. 2 is a schematic view of a first example of a device for carrying out the process of the invention, FIG. 3 is a schematic view of a second example of a device for carrying out the process of the invention, FIG. 4 illustrates a filament deposition system used in the device of Figure 2, FIG. 5 is an exploded view of a three-dimensional scaffold of filaments cylindrical obtained by the system of Figure 4, FIGS. 6A to 6D are examples of ordered networks of channels obtained by the system of Figure 4, and - Figure 7 shows the different steps of the manufacturing process in if you coating according to the invention.
Detailed description of the invention Figure 1 shows very schematically an architecture of an aircraft turbomachine, in this case a turbofan engine, at the level of of which is implemented the method of manufacturing a coating made of material abradable to acoustic properties of the invention.
Conventionally, such a turbofan engine 10 has an axis longitudinal 12 and consists of a gas turbine engine 14 and a nacelle annular 16 centered on the axis 12 and arranged concentrically around the engine.
From upstream to downstream, depending on the flow direction of an air or gas flow passing through the turbojet, the engine 14 comprises an air inlet 18, a blower 20, a low-pressure compressor 22, a high-pressure compressor,

6 pressure 24, a combustion chamber 26, a high-pressure turbine 28 and a low-pressure turbine 30, each of these elements being arranged according to axis 12. The ejection of the gases produced by the engine is effected through a nozzle consisting of an annular central body 32 centered on the axis longitudinal 12, an annular primary cover 34 surrounding coaxially the central body to delimit with it an annular flow channel of the flux primary Fi, and an annular secondary cover 36 surrounding coaxially the primary cover to delimit with it an annular flow channel of the F2 secondary flow coaxial with the primary flow channel and in which are disposed of the straightening vanes 38 (in the exemplary embodiment illustrated, the nacelle 16 of the turbojet engine and the secondary hood 36 of the nozzle are a alone and even piece). The primary and secondary covers include the intermediate casings of turbines 28A and 30A surrounding the blades of turbine rotors and blower housing 20A surrounding the blades of fan rotor.
According to the invention, it is proposed to affix, by additive manufacturing, the inner walls of housings facing rotor blades, a coating with abradable and acoustic features in the form of a three-dimensional scaffold of filaments forming between them an ordered network of channels. Depending on the configuration envisaged, Interconnections between the channels may exist on a regular basis when the layering of the different layers of the coating intended to generate these different channels. This wall is preferably a wall of a turbomachine, such as an airplane turbojet, mounted on the periphery immediate moving blades, and more particularly the inner wall of the housing of 20A woven composite blower arranged on the periphery of the blades of blower. However, a deposit on the turbine casing (s) 28A, 30A may also be considered subject of course that the abradable material of type metal or ceramic then has properties adapted to the environment at very high temperature of the turbine.

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7 The advantage of the abradable functionality is to make the rotor-crankcase compatible with the deformations experienced by the blades rotation when these are subject to the sum of the efforts aerodynamic and centrifugal.
By abradable material is meant the ability of the material to dislocate (erode) in operation in contact with a room next to (low shear strength) and its resistance to wear as a result of the impacts of particles or foreign bodies that it is required to ingest in operation. A
such In addition, the material must retain or promote good properties aerodynamic, have resistance to oxidation and corrosion sufficient and a coefficient of thermal expansion of the same order as layer or substrate on which it is deposited, in the latter case the material woven composite forming the crankcase walls.
FIG. 2 illustrates a first example of a device enabling the production of such a coating with acoustic properties by continuous deposition of filaments of abradable material at a turbomachine inner wall such as a blower housing 20A.
This device comprises a housing support 40 intended to position the fan casing 20A so that its longitudinal axis 42 is parallel on the ground, thus favoring the deposition of the filamentary material by gravity (deposit vertical material down) on any point of the inner wall of casing. This support may for example consist of two rollers synchronized drive 40A, 40B for simultaneously driving the housing into rotation about its longitudinal axis, thus ensuring a degree of freedom in rotation along this longitudinal axis.
The device also comprises a mechanical assembly 44 provided with several joints and equipped at a free end 44A with a system of deposit of filamentary material 46 comprising at least one ejection nozzle 46A for which abradable material is ejected accurately. Typically, such a mechanical assembly is constituted at least by a 3 axis machine or, as illustrated by a robot with precision numerical axes

8 (positioning of the order of 5 microns) allowing via known software appropriate to order the printing according to a deposition path defined by the user. Thanks to this equipment, it is therefore possible to guarantee a deposit filaments in a determined three-dimensional space, controlling the print parameters such as the flow velocity of the material, the position and speed of movement of the mechanical assembly.
More specifically, this mechanical assembly 44 has a degree of freedom in translation along the longitudinal axis of the casing so as to reach any point of its inner wall to deposit the abradable material.
he also has a degree of freedom in vertical translation, so that the distance to the deposition area can be adjusted in real time.
Of Moreover, this degree of freedom makes it possible to adapt the deposit system to variations of diameter that can be observed between different architectures of turbojets. To do this, a distance sensor 48 integral or arranged at near the ejection nozzle 46A is provided in order to measure the distances enter this ejection nozzle and the housing or the abradable material. This sensor can in besides being used, via the use of appropriate known algorithms, for to permit a metrological control of the initial and final dimensional geometry who, in the particular case of a fan casing, is non-axisymmetric.
Optionally and depending on the nature of the material used, the device may also include a solidification module 50 for promoting and speed up solidification process of the deposited abradable material. This module can be formed by a device for emitting light waves (UV, infrared or other), by one or more fans blowing towards the abradable material or well by one or more heating resistors or by any other similar heating system, or even possibly by a device refrigerant according to the nature of the material used, these different devices up operate alone or in combination with each other.
Control and control of all the constituents of the device are provided by a management unit 51, typically a microcontroller or a microcomputer, which manages the deposition of abradable material =

9 in connection with the rotation of the fan case, the tolerancing final dimension according to the data obtained from the distance sensor 48 and when there is control of the solidification via the module 50.
FIG. 3 illustrates an alternative embodiment of the device (the unchanged elements bear the same references) in which the single nozzle ejection is replaced by a multi-nozzle system 52 to accelerate the deposition of the abradable material by a factor greater than the number of nozzles and having a plurality of ejection nozzles 54A ¨ 54E aligned with the axis of a workpiece rigid 56 which supports them and whose vertical positioning of each of these nozzles, measurable by an associated distance sensor 48A - 48E, is adjustable of independently to ensure optimum distance between each nozzle and the surface on which the filamentary material is deposited (taking into account the cylindrical shape of the fan casing). Note that the single sensor 48 could, using a post-processing of the data collected, also deduce this distance between each of the nozzles and the surface of the housing. Each nozzle is advantageously equipped with a circuit for regulating the pressure and the nozzle outlet temperature so as to control the geometries as well than the times and cycles of deposit.
The nozzles are preferably removable and separable from the piece of support 56 so that one can parameterize the number of nozzles and their geometry depending on the coating to be used. They can also be adjustable in height according to the angle defined by the Filament material deposition system with respect to the housing. In addition, each nozzle can be powered by different material sources, according to the type of coating desired.
The support piece 56 may have a pivot connection 58 through relative to the mechanical assembly 44 which supports it. The axis of this pivot is oriented vertically, that is to say parallel to that of the nozzles. So, in applying rotation to the support piece, it is possible to control the spacings between material deposition points, regardless of the direction of travel relative to the nozzles (axial or azimuth) relative to the fan casing 20A.

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The filament deposition system 46 is illustrated in such a way schematic in Figure 4. This filament deposition system aims to deposit in connection with the aforementioned pressure control circuit and temperature internal to the system, an abradable material by extrusion via the ejection nozzle 5 46A of shape and dimension first calibrated on the substrate 62 and then successively on the different superimposed layers created, up to obtaining the desired thickness. The filament deposition system follows a deposit track controlled by the management unit 51 to which it is joined ensuring control of the filament deposition system and controlling in all

10 point of the treated surface both the filament arrangement and the porosity of the necessary to guarantee the desired abradability.
The supply of abradable material is ensured from a screw to conical extrusion 64 for mixing several components to form a thixotropic fluid having the appearance of a paste. The conical extrusion screw allows to ensure adequate mixing of components and homogeneous (throughout the deposition operation), to obtain in fine a fluid material with high viscosity that will be deposited by the calibrated nozzle. During this operation, avoid the generation of air bubbles that form as much defect in the filament printed and it is therefore necessary to push the material very gradually.
We note that the change in the constitution of the deposited material may be realized simply by checking the various components introduced successively in the conical extrusion screw which has at least two inputs 64A, 64B
for the simultaneous introduction of both components. A heating lamp 66 mounted near the ejection nozzle 46A and acting as a module of solidification can be used to stabilize the deposited material and avoid the creep during the deposit.
Figure 5 illustrates in exploded perspective a small part of the three-dimensional scaffold 60 of filaments 100, 200, 300, advantageously cylindrical, abradable material allowing the realization of the coating under the shape of an ordered network of channels likely to confer properties acoustic wall 62 for receiving this coating.

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11 Indeed, the goal is to print, in the structure of the material abradable, specific patterns with dimensioned porosities allowing the passage or dissipation of aerodynamic fluctuations (see modifications) and / or acoustic waves. These reasons may consist of of the perforations smaller than 1.5 mm or grooves allowing in addition to improving aerodynamic margins. But, advantageously, these patterns consist of channels or micro channels forming an ordered network as shown by the different configurations of FIGS. 6A, 6B, 6C and 6D.

In FIG. 6A, the three-dimensional scaffolding of filaments 100, 200 consists of superimposed layers whose filaments of a given layer are oriented alternately at 0 or 900 without offset in the overlay filaments having the same direction.
In FIG. 6B, the three-dimensional scaffold of filaments 100, 200 consists of superimposed layers whose filaments of a given layer are alternately oriented at 0 or 90 and have an offset in the superposition of the filaments having the same direction.
In FIG. 6C, the three-dimensional scaffold of filaments 100, 200, 300, 400, 500, 600 consists of superimposed layers with orientation directions of the filaments Di offset by the same angular difference, typically 30, at each layer i (i between 1 and 6).
And in FIG. 6D, the three-dimensional scaffold of filaments 100, 200 consists of superimposed layers presenting, for each of the layers, both a 0-filament orientation and an orientation of filaments at 90, so as to form vertical perforations 700 of sections square between the filaments.
An impression on a crankcase with these different network configurations showed the feasibility of such filament deposition of abradable material according to the aforementioned method of additive manufacturing. Tests of mechanical behavior in compression and bending were also realized samples for a low-energy impact test or characterization of acoustic impedance at normal incidence. In particular, he at

12 a transmission of acoustic energy through scaffolding and an absorption of some of this acoustic energy by modification of aero-acoustic sources or absorption of sound waves propagators.
Figure 7 shows the different steps of the manufacturing process additive coating on a blower housing for a structure to mesh orthogonal lines such as that illustrated in Figure 6A obtained with the device of the FIG. 3, the fan casing 20A being positioned on its support of retention 40 mobile in rotation.
In a first step 1000, the filament deposition system 46 is positioned by a series of vertical and axial translations over the zoned deposition of material, at the axis 42 of the fan casing and at distance determined with respect to the inner surface of the fan casing, and the support multi-nozzle is oriented parallel to the axis 42 (position called 00). In a next step 1002, the fan casing is rotated causing so a deposit of matter in planes perpendicular to the axis 42, on the 360 of its circumference, with as many filaments of matter as number of nozzles.
At step 1004, the casing having returned to its initial position, the rotation of fan casing ends and the nozzle support piece 56 performs so a rotation of 90 corresponding to the direction of orientation of the filaments of the second layer of coating. In a step 1006, the deposit is made a first row of material filaments on a first sector of the casing by axial displacement of the filament deposition system 46, so that make a deposit at 90 relative to the filaments of materials previously circumferentially deposited around the axis 42. At the next step 1008, the Fan housing rotates corresponding to angular gap determined equal to the first sector already covered then it is made back to step 1006 to make deposits on the following sectors until they cover the crankcase circumference (test of step 1010). Steps 1000 to 1008 are then repeated until the desired material thickness is obtained (final test of step 1012).

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13 Note that if in the above description, the circumferential deposition is done through the rotation of the housing, it is understood that this deposit can also be realized by rotation of the filament deposition system. Similarly, if the sectoral deposit is made through axial displacement of the deposit system filament, it is understood that this deposit can also be made by a axial displacement of the housing. The important thing is that there is a displacement relative between the casing and the filament deposition system.
It will also be noted that if the process has been described with reference to multi-nozzle support, it is clear that it is also applicable to nozzle configuration Figure 2 provided that after each rotation, 3600 axial displacement of the filament deposition system by a determined step (step optional 1016) for, step by step, once all 360 rotations completed, cover the entire width of the housing.
In the manufacturing configuration of the coating having the structure to meshes inclined at regular angular gaps (every 30) such as illustrated in FIG. 6C, the rotation step 1004 is no longer 90 but only 30, so as to perform in the next step 1006 the deposition of the layer at 30 and no longer at 90. And once this second layer 200 deposited, a additional rotation of 30, ie 60, is carried out following the test of step 1014 to deposit the third layer 300 instead of a return to the position initial to 0 which is performed in this configuration only once filed the layer 600 corresponding to the last orientation direction of the filaments.
It should be noted that an additional layer can be added prior to the development of this three-dimensional scaffolding. Indeed, the fan case is a 3D composite woven case whose geometry three-dimensional model generally presents deviations (defects in shape) compared to the ideal calculated area, in particular because of the trend towards lobe formation related to the weaving process used (typically of type poly-flex). However, the catching up of these defects currently involves complex and expensive. It is therefore possible with the device to file a game-catching material (resin or other) to obtain a geometry =

14 known. The advantage of this preliminary step is to return to a surface of deposit controlled, precisely defined and responding to the constraints of forms necessary to ensure the good aerodynamic games of the engine zone.
It should also be noted that additional layers may be added locally to ensure the axisymmetry of the abradable surface.
In indeed, the fan casings often have a non-geometry axisymmetric.
The abradable material extruded by the calibrated nozzle or nozzles is advantageously a high viscosity thermosetting material which is devoid of solvent whose evaporation generates as it is known a strong withdrawal.
This material is preferably a resin with slow polymerization kinetics and Stable filament flow in the form of a mixture thixotropic which therefore has the advantage of a much lower shrinkage enter the impression on the substrate (just after extrusion of the material) and the structure final (once heated and complete polymerization).
An example of an abradable material used in the process of the invention is a material which is in pasty form and consists of three components namely a polymer base, for example an epoxy resin (presenting as blue modeling clay), a crosslinking agent or accelerator (posing as a white modeling dough) and a jelly translucent colored oil (eg, petrolatum). Components accelerator / base are distributed in a weight ratio from base to the accelerator between 1: 1 and 2: 1 and the petroleum jelly is present enter 5 and 15% by weight of the total weight of the material. The base may further include microspheres of hollow glasses of a determined diameter to ensure the porosity desired while allowing to increase the mechanical performance of scaffolding printed. The interest of the introduction of petroleum jelly resides in reducing the viscosity of the resin as well as the kinetics of reaction of the abradable, which makes its viscosity more stable during the printing and thus facilitates the flow of the material. (The viscosity is

15 directly related to the extrusion pressure needed to ensure speed adequate extrusion to maintain print quality).
By way of example, such a ratio of 2: 1 gives an abradable material including 0.7g of accelerator and 1.4g of base to which it is advisable to add 0.2g of petroleum jelly.
Thus the present invention allows a fast and stable printing to effectively reproduce high-performance acoustic structures controlled (roughness, appearance, open ratio) with a small size of filament (<250 microns in diameter) and low weight (improved porosity rate>
70%) particularly interesting in view of the strong constraints encountered in aeronautics.

Claims (10)

1.
In situ additive manufacturing process for coating consisting of deposit on an internal surface of a turbomachine casing (20A, 62) a filament (100, 200, 300, 400, 500, 600) of an abradable material according to a predefined deposition path to create a three-dimensional scaffold of filaments forming between them an ordered network (60) of channels, the method being characterized by the following steps:
position a filament deposition system (46) at a longitudinal axis (42) of said housing at a position and a distance determined with respect to said inner surface of said housing, deposit a first layer of said coating on the 360 ° of the circumference of said housing by a relative circumferential movement between said casing and said filament deposition system (46), rotating said filament deposition system (46) at a first determined angle and position said material deposition system filamentary (46) at said longitudinal axis of said housing at a position and a determined distance from said first layer of said coating, deposit on a sector of said casing by a relative axial displacement between said housing and said Nament material deposition system, a second layer of said coating on said first layer of said coating, relative circumferential movement between said housing and said filamentary material deposition system (46) of angular deviation determined, corresponding to the first sector already covered at the time of said second layer of coating, and repeat the deposition step on said crankcase area and the step of relative circumferential displacement according to said angular difference determined for the following sectors up to cover the 360 ° of the circumference of the carter, and after rotating said material deposition system filamentary of a determined second angle, repeat all the steps for the following layers until a thickness of desired coating. 2. Method of additive manufacturing in situ coating according to the claim 1, characterized in that prior to the deposit of said first layer of said coating, it is deposited a layer of a catch-up material play to obtain a deposition surface of known geometry. 3. Process of additive manufacturing in situ coating according to the claim 1 or claim 2, characterized in that said step of rotation of said filament deposition system is performed twice rotation successive 90 °, the first determined angle being equal to 90 °. 4. Process of additive manufacturing in situ coating according to the claim 1 or claim 2, characterized in that said step of rotation of said filament deposition system is performed as many times it There are definite directions of orientation of the different filaments. 5. Method of additive manufacturing in situ coating according to the claim 4, characterized in that said step of rotating said system of Filamentary deposition is performed six times by successive rotation of 30 °, the first determined angle being equal to 30 °. 6. In-situ additive manufacturing process of coating according to one any of claims 1 to 5, characterized in that layers additional coating is added locally to reflect a non-axisymmetric geometry of said housing. 7. Method of additive manufacturing in situ coating according to one any of claims 1 to 6, characterized in that the deposition of material filament is effected by a plurality of ejection nozzles (54A-54E) the vertical positioning of each of said ejection nozzles is adjustable from independently. 8. In-situ additive manufacturing process of coating according to one any of claims 1 to 7, characterized in that said housing is a turbomachine blower housing made of woven composite material. 9. Filament deposition system (46) for the implementation of the additive in situ manufacturing method of coating according to any one of the Claims 1 to 8. 10. Abradable wall coating of turbomachine obtained from the additive in situ manufacturing method of coating according to any one of the Claims 1 to 9.