CH720150A2 - Watch pivot axis and method of manufacturing said watch pivot axis - Google Patents

Abstract

The present invention relates to a watch pivot axis (1) comprising at least one pivot (2) at at least one of its ends. Said pivot (2) is entirely made of an alloy based on CoNiCr without beryllium and comprising by weight at least 42% cobalt, between 20% and 30% nickel, between 10% and 18% chromium, between 2% and 5% molybdenum, between 2% and 5% tungsten, between 2% and 10% iron, between 0% and 3% titanium, between 0% and 2% aluminum, possible impurities each having a lower content or equal to 0.5%, the sum of the different elements being equal to 100% by weight. The present invention also relates to a method of manufacturing such a watch pivot axis (1) comprising: a) a step of manufacturing a blank of the watch pivot axis (1) comprising, at at least one end, at least one part consisting of said CoNiCr-based alloy and intended to constitute a pivot (2); and b) a final step consisting of force-free precision machining of at least the part made of said alloy of the blank obtained in step a) in order to obtain at least one finished pivot (2) entirely made of said alloy .

Description

Technical area

[0001] The present invention relates to a watch pivot axis comprising at least one pivot at at least one of its ends.

[0002] The present invention also relates to a watch movement and a timepiece comprising such a watch pivot axis.

[0003] The present invention also relates to a method of manufacturing such a watch pivot axis.

State of the art

[0004] Such watch pivot axes are used for the rotational mounting of watch components, such as balance wheels.

[0005] Traditionally, a watch pivot axis is made of steel from a hardenable steel bar. The manufacture of such a steel axis consists of carrying out precision turning operations to define different active surfaces (reach, shoulder, pivots etc.) then subjecting the turned axis to heat treatment operations including at least one quenching to improve the hardness of the axis and one or more tempers to improve its toughness. The heat treatment operations are followed by a rolling operation of the axis pivots, an operation which consists of polishing the pivots to bring them to the required dimensions. During this rolling operation, the hardness and roughness of the pivots are further improved via surface hardening. We thus obtain, at the end of the process, an axis having pivots with the required dimensions, hardness and roughness. It should be noted that rolling can hardly be carried out with materials whose hardness is greater than 600 HV.

[0006] The watch pivot axes, and in particular the precision axes such as the balance axes, conventionally used in mechanical watch movements, are made in grades of free-cutting steels which are generally martensitic carbon steels including lead and manganese sulphides to improve their machinability. A steel of this known type, designated 20 AP, is typically used for these applications. Lead-free alternatives such as Finemac grade are also used.

[0007] This type of material has the advantage of being easily machinable, in particular of being suitable for bar turning and has, after adequate quenching and tempering treatments, high mechanical properties which are very interesting for the production of axes. watchmaking pivots. These steels have in particular high wear resistance and hardness after heat treatment. Typically the hardness of the pivots of an axle made of 20 AP steel can reach a surface hardness exceeding 700 HV after heat treatment and rolling.

[0008] Although providing satisfactory mechanical properties for the watchmaking applications described above, this type of material has the disadvantage of being magnetic and of being able to disrupt the operation of a watch after being subjected to a magnetic field, and this in particular when this material is used for the production of a balance axis cooperating with a spiral balance made of ferromagnetic material. It should also be noted that these martensitic steels are also sensitive to corrosion.

[0009] To try to remedy these drawbacks, a solution has been proposed, consisting of using austenitic stainless steels which have the particularity of being non-magnetic, that is to say of the paramagnetic, diamagnetic or antiferromagnetic type, whose relative magnetic permeability is less than or equal to 1.01.

[0010] However, these austenitic steels have a crystallographic structure that does not allow them to be quenched and to achieve hardness and therefore wear resistance compatible with the requirements required for the production of watch pivot axes. One way to increase the hardness of these steels is work hardening, however this hardening operation does not make it possible to obtain hardnesses greater than 500 HV for this type of material. Consequently, in the context of parts requiring high resistance to wear by friction and having to have pivots presenting little or no risk of breakage or deformation, the use of this type of steel remains limited.

[0011] Another proposed solution consisted of depositing hard layers of materials such as amorphous carbon known under the English name “diamond like carbon” (DLC) on the pivot axes. However, we have noted significant risks of delamination of the hard layer and therefore the formation of debris which can circulate inside the watch movement and disrupt the functioning of the latter, which is not satisfactory.

Another approach has been considered to remedy the disadvantages of austenitic stainless steels, namely the surface hardening of these pivot axes by nitriding, carburizing or nitrocarburizing. However, these treatments are known to cause a significant loss of corrosion resistance due to the reaction of nitrogen and/or carbon with the chromium of the steel and the formation of chromium nitride and/or carbide. chromium causing a localized depletion of the chromium matrix, which is detrimental for the desired watchmaking application.

[0013] An additional chemical Ni deposition operation seems necessary in order to overcome these corrosion problems, which complicates and greatly increases the cost of the manufacturing process.

[0014] Other approaches still exist, such as those made from titanium alloys, hard metals, certain oxides or ceramics. However, the use of these materials does not make it possible to obtain satisfactory performances specific to watch pivot axes, other than amagnetism.

[0015] A final approach is proposed in patent application CH 716,669 which describes a method of manufacturing a balance shaft made of metallic glass comprising a step of manufacturing a blank made of metallic glass as well as a finishing step of the blank to obtain the balance shaft. The termination step can be preceded by a machining step. To obtain a balance shaft, this machining step must be followed by the finishing step which refers to finishing operations, such as surface treatment, grinding, rolling, laser or mechanical-chemical polishing, tribofinishing or polishing. bulk. Such termination steps have the disadvantage of being to the detriment of the geometric quality of the part (rounding of surfaces, loss of precision, etc.). Additionally, laser polishing involves the use of continuous laser or laser with pulse durations up to 100 ns. The laser attacks the part normal to the surface to be treated, and melts a part of said surface, the smoothing being done thanks to the interfacial tension, without removing any material. The disadvantage is that laser polishing is characterized by a distribution of roughness Ra linked to the formation of undulations giving a “mirage” effect.

[0016] The present invention aims to remedy these drawbacks by proposing a watch pivot axis made of a non-magnetic metal alloy, having mechanical properties compatible with the wear and shock resistance requirements required in the watchmaking field, limiting the sensitivity to magnetic fields, and presenting at least at the level of the pivots, an extremely low roughness Ra.

Disclosure of the invention

[0017] To this end, the present invention relates to a watch pivot axis comprising at least one pivot at at least one of its ends.

[0018] According to the invention, said pivot is entirely made of an alloy based on CoNiCr without beryllium and comprising by weight: – at least 42% cobalt – between 20% and 30% nickel – between 10% and 18% chromium – between 2% and 5% molybdenum – between 2% and 5% tungsten – between 2% and 10% iron – between 0% and 3% titanium – between 0% and 2% aluminum – impurities possible each having a content less than or equal to 0.5%, the sum of the different elements being equal to 100% by weight.

[0019] The present invention also relates to a method of manufacturing a watch pivot axis comprising at least one pivot at at least one of its ends, at least said pivot being made entirely of the CoNiCr-based alloy defined below. above, said method comprising: a) a step of manufacturing a blank of the watch pivot axis comprising, at at least one end, at least one part made of said alloy and intended to constitute a pivot; and b) a final step consisting of force-free precision machining of at least the part made of said alloy of the blank obtained in step a) in order to obtain at least one finished pivot made entirely of said alloy.

[0020] The watch pivot axis according to the invention is made of a non-magnetic material while having mechanical properties compatible with the wear and shock resistance requirements required in the watchmaking field.

[0021] In a particularly advantageous manner, the watch pivot axis is made entirely of said CoNiCr-based alloy.

[0022] Advantageously, said watch pivot axis is arranged to form a balance axis.

[0023] Thus, the surface hardness of the pivots of the watch pivot axis according to the invention is that of said CoNiCr-based alloy, reaching and even exceeding values of 750 HV.

[0024] Furthermore, said CoNiCr-based alloy is non-magnetic and resistant to corrosion. In addition it is beryllium-free so it is compatible with the most recent regulations.

[0025] As a result, all the performances of a current non-magnetic watch pivot axis are improved.

The present invention also relates to a watch movement and a timepiece comprising a watch pivot axis as defined above.

Brief description of the drawings

Other characteristics and advantages of the present invention will appear on reading the following detailed description of an embodiment of the invention, given by way of non-limiting example, and made with reference to the drawings appended in which: – Figure 1 is a schematic view of a pivot of a pivot axis according to the invention; and – Figure 2 is a schematic representation of the steps of a method according to the invention.

Modes of carrying out the invention

With reference to Figure 1, the present invention relates to a watch pivot axis 1 comprising at least one pivot 2 at at least one of its two ends. Conventionally, the pivot axis 1 comprises a pivot 2 at each of its ends, said pivots having a surface of revolution, and each being intended to pivot in a bearing, typically in an orifice of a stone or ruby.

The watch pivot axis 1 has a diameter less than or equal to 2 mm and the pivot 2 has an outer diameter less than or equal to 200 µm, preferably less than or equal to 100 µm, preferably less than or equal to 90 µm , and more preferably less than or equal to 70 μm.

[0030] Preferably, the watch pivot axis 1 is a balance axis, comprising a plurality of sections of different diameters, conventionally defining bearings and shoulders, such as a plate and a section for receiving the balance, arranged along a tigeron between two end portions defining the two pivots, only one end being represented here in Figure 1. Obviously, other types of watch pivot axes are conceivable such as for example mobile axes watchmakers, typically escapement pinions, barrel shafts or even anchor rods.

[0031] Parts of this type have diameters at the body level preferably less than 2 mm, and pivots with a diameter less than 0.2 mm preferably as described above, with a precision of a few microns.

The pivot axis may include functional elements linked to its use. For example, the axis may include teeth, a thread or a hook for fixing the spring in the case of a barrel shaft.

[0033] At least the pivots 2 constitute functional portions, providing a guiding function to ensure the pivoting of the axis 1 in its bearings.

[0034] In addition to the pivots 2, the functional portions treated according to the invention may also include other sections of the pivot axis 1, such as the tigerons, the plate and the section for receiving the balance. In the present description, the functional portions are defined as being the portions of the pivot axis for which in particular a certain roughness value Ra (for example Ra < 0.5 µm) is necessary to ensure the function of said portion, for example the guidance for the pivots or driving for the plate and the section to receive the balance wheel.

[0035] At least the functional portions comprising at least the pivot 2, and preferably the entire watch pivot axis 1, are entirely made of a multi-phase cobalt alloy based on beryllium-free CoNiCr and comprising by weight: minus 42% cobalt – between 20% and 30% nickel – between 10% and 18% chromium – between 2% and 5% molybdenum – between 2% and 5% tungsten – between 2% and 10% iron – between 0% and 3% titanium – between 0% and 2% aluminum – possible impurities each having a content less than or equal to 0.5%, the sum of the different elements being equal to 100% by weight.

[0036] This means that the pivot 2 is entirely made up of said alloy, and that the constituent material of at least the pivot 2, and preferably of the entire watch pivot axis 1, is said alloy, no other material being used.

Preferably, said alloy comprises between 42% and 45% cobalt.

Preferably, said alloy comprises between 21% and 26% nickel.

Preferably, said alloy comprises between 12% and 18% chromium.

Preferably, said alloy comprises between 3% and 4% molybdenum.

Preferably, said alloy comprises between 3% and 4% tungsten.

Preferably, said alloy comprises between 5 and 9% iron.

Preferably, said alloy comprises between 0% and 2% titanium.

Preferably, said alloy comprises between 0% and 1% aluminum.

The impurities may include one or more of the following elements: C, Si, Mn, P, and S.

The alloy used in the present invention does not include beryllium.

[0047] In a first embodiment, said alloy has the following composition in % by weight: Co=42%; Ni=26%; Cr=12%; Fe=9%; W=4%; Mo=4%; Ti=2%; Al=1%; Be=0.

[0048] In another preferred embodiment, said alloy has the following composition in % by weight: Co=45%; Ni=21%; Cr=18%; Fe=5%; W=4%; Mo=4%; Ti=1%; Be=0; impurities such as C<0.15; P<0.0015; S<0.0015; Si, Mn; Fe=the scale at 100.

The CoNiCr-based alloy used in the present invention is different from Phynox®.

[0050] In a particularly advantageous manner, such an alloy is non-magnetic so that the watch pivot axis according to the invention has the advantage of being non-magnetic in order to limit its sensitivity to magnetic fields.

[0051] In a particularly advantageous manner, the functional portions comprising the pivot 2, and preferably the entire watch pivot axis 1, according to the invention, present in the finished state, ready for use, a hardness of surface area greater than 750 HV, and preferably greater than or equal to 780 HV, and more preferably greater than or equal to 800 HV. Vickers hardness testing methods are defined in the following standards ASTM C1327 and ISO 6507.

[0052] According to the invention, the functional portions comprising the pivot 2, and preferably the entire watch pivot axis 1, have in the finished state, ready for use, a uniform roughness Ra less than or equal to 50 nm ± 20%, preferably less than or equal to 25 nm, preferably less than or equal to 20 nm, preferably less than or equal to 15 nm, and preferably less than or equal to 12 nm, more preferably less than or equal to 10 nm, and more preferably between 5 nm and 9 nm, terminals included. The roughness Ra is defined according to the ISO 4287 standard.

[0053] In addition to being non-magnetic, said CoNiCr-based alloy is resistant to corrosion.

[0054] Thus, in addition to being non-magnetic, the functional portions comprising at least the pivot 2, and preferably the watch pivot axis 1, according to the invention present all the satisfactory performances specific to watch pivot axes for which we seek, on the surface, a hardness greater than 700 HV in order to resist wear, a low coefficient of friction to limit lubrication, a smooth state (Ra < 0.5 µm) for friction and isochronism, a resistance to corrosion, and for which we are looking for a core with high rigidity, toughness and breaking strength Rm (high elastic limit).

[0055] The invention also relates to the method of manufacturing a watch pivot axis 1 comprising at least one pivot 2 at at least one of its ends, at least said pivot 2 being made entirely of the alloy based on CoNiCr as defined above. The method according to the invention advantageously comprises the following steps, described in relation to Figure 2: a) a step of manufacturing a blank of the watch pivot axis 1 comprising, at least one of its two ends, at minus a part consisting entirely of said CoNiCr-based alloy and intended to constitute a pivot; and b) a final step consisting of force-free precision finishing machining of at least the part made entirely of said alloy of the blank obtained in step a) in order to obtain at least one finished pivot made entirely of said alloy , which presents its final configuration, that is to say all the characteristics required for its use and its function as a pivot axis, in particular in terms of hardness, roughness, dimensions and geometry, and which does not therefore no longer requires any other subsequent processing steps, such as the traditional termination or finishing steps.

The beryllium-free CoNiCr-based material used in the present invention can be delivered for example in the form of strips 60 mm wide, with thicknesses available between 50 μm and 800 mm. The alloy may have undergone appropriate heat treatments to exhibit the desired high hardness, as defined above. The composition of the beryllium-free CoNiCr-based alloy of the strip supplied is identical to that of the alloy of the pivot axis obtained according to the process of the invention.

[0057] The axis blank produced during step a) can be produced for example by laser beam guided by a water jet or by electroerosion (for example wire EDM).

[0058] If necessary, the blanks manufactured during step a) are produced with dimensions provided for recovery.

[0059] After step a), the last step of the method of the invention is step b) which consists of precision finishing machining without force of the watch pivot axis, or at least of its part consisting entirely of said CoNiCr alloy intended to constitute a pivot. No subsequent finishing operations, such as rework, on another machine to finish the pivot pins are necessary. In the method of the invention, the pivot axis is obtained without interruption of the process by continuous processing, in a single step and on a single finishing machining machine once the axis blank has been produced. The method of the invention makes it possible to use a single finishing machining machine continuously, without requiring interrupting the process to use another machine to carry out any other finishing step.

[0060] In the present description, non-conventional machining is called force-free machining in which there is no mechanical action transmitted by direct contact and force between a tool and the part, unlike conventional machining where there is direct contact between the tool and the workpiece and in which significant cutting forces are involved. Force-free machining is therefore machining without direct contact between the part to be machined and a machining tool which would be likely to exert a force or stress on said part.

[0061] Advantageously, the force-free precision machining carried out during step b) is a force-free material removal process by femto laser turning, electrochemical turning (ECM), or a EDM turning (e.g. wire EDM).

[0062] The machining operations of this step are advantageously carried out by femto-second pulsed laser micromachining with a laser of wavelengths comprised for example between 200 nm and 2000 nm, preferably between 400 nm and 1000 nm, terminals included. The laser parameters can be for example: average power between 1 W and 100 W, energy per pulse between 20 µJ and 4000 µJ, frequency between 100 kHz and 1000 kHz, pulse duration between 100 fs and 2 ps. The femto laser allows material ablation without heat transfer to the rest of the material and not surface fusion which is used during laser polishing in traditional finishing operations.

[0063] The ECM (electrochemical machining) and EDM (electrical discharge machining) machining methods can also be used for the finishing step.

[0064] Thanks to precision machining without force, in particular by femto laser, the final step b) makes it possible to achieve surface states with a uniform roughness Ra preferably less than or equal to 500 nm. More particularly, by playing on the last depth of cut, on the rotation speed of the pivot axis and on the oscillation of the laser added to its primary movement relative to the axis blank, it is possible, to 'a particularly advantageous way of obtaining at the end of step b), at least one finished pivot made of CoNiCr-based alloy as defined above, said finished pivot having a uniform roughness Ra less than or equal to 50 nm ± 20%, preferably less than or equal to 25 nm, preferably less than or equal to 20 nm, preferably less than or equal to 15 nm, and preferably less than or equal to 12 nm, more preferably less than or equal to 10 nm , and more preferably between 5 nm and 9 nm, terminals included.

[0065] In particular, for force-free precision machining by femto laser, a spot with a diameter of less than or equal to 8 μm is preferably used, the laser beam attacking the rotating pivot axis radially. The angle of the beam cone is preferably less than 4° and more preferably less than 2°. Advantageously, the femto laser control system makes it possible to bring the axis blank extremely precisely to 1 or 2 µm from the final dimension, the last pass of the femto laser being planned to reach at the same time the desired Ra rating and roughness.

[0066] Furthermore, step b) is advantageously carried out under permanent blowing of air or nitrogen in order to evacuate the dust generated by the machining. A suction of this same dust is located opposite the blowing.

[0067] The pivots 2 obtained having such a roughness Ra, it is no longer necessary to provide, after step b) another finishing step, in particular a tribological finishing, such as rolling or tribofinishing.

[0068] Thus, in a particularly advantageous manner, the method according to the invention does not comprise, after step b), any termination or finishing step on another machine, in particular no tribological treatment step, such as rolling or a tribofinishing, since the pivot entirely made in the CoNiCr-based alloy as defined above, finished, obtained in step b) already has the required dimensions, hardness and roughness, which are traditionally obtained only after a rolling and/or tribofinishing operation.

[0069] In a preferred embodiment, the watch pivot axis 1 is made entirely of said CoNiCr-based alloy as defined above, said finished pivot axis comprising functional portions having a surface of revolution and comprising at least said pivot 2. In this case, the axis blank obtained in step a) corresponds to the functional configuration of the finished pivot axis 1, that is to say that the blank of axis obtained according to step a), with the exception of the parts intended to constitute the functional portions, has all the characteristics allowing it to ensure its function and required for its use as a pivot axis, in particular in terms of hardness, roughness, dimensions and geometry, and therefore no longer requires any other subsequent processing step to modify its functional configuration, with the exception of the parts intended to constitute the functional portions. Step b) is implemented at least on the parts intended to constitute said functional portions in order to obtain said finished pivot axis 1, said functional portions comprising the pivot 2 obtained according to step b) then presenting their functional configuration final, so that the entire axis has all the characteristics required for its use as a pivot axis, in particular in terms of hardness, roughness, dimensions and geometry, and therefore no longer requires any other subsequent processing step to modify its functional configuration, such as the traditional termination or finishing steps. In particular the functional portions comprising the finished pivot 2 have a roughness Ra less than or equal to 500 nm, uniform to ± 20%, preferably less than or equal to 100 nm, preferably less than or equal to 50 nm, preferably less than or equal to 25 nm, preferably less than or equal to 20 nm, preferably less than or equal to 15 nm, and preferably less than or equal to 12 nm, and more preferably strictly less than 10 nm, and more preferably less than or equal to 9 nm , and more preferably between 5 nm and 9 nm, terminals included.

[0070] The method according to the invention makes it possible to obtain a non-magnetic watch pivot axis having all the required mechanical properties, in particular a high elastic limit, very high hardness, very low roughness, in a simple and economical manner. Indeed, the method according to the invention makes it possible to avoid the rolling operations traditionally used, so that the number of operations necessary for the manufacture of the watch pivot axis is reduced, the production time being considerably reduced. In fact, the processing of the axis blank, once the blank has been made, requires only a single operation, and therefore a single tightening, to obtain a finished pivot axis. The last step of said process is a finishing machining step which makes it possible to obtain a finished axis with a certain roughness precision Ra, without requiring a subsequent finishing operation as such, such as a rework, on another machine for finish the pieces. The pivot axis is obtained without process interruption by continuous processing, in a single step and on a single machining machine from the blank. Thus, unlike traditional manufacturing processes, the process of the invention does not include any termination step in a finishing phase which means an interruption of the process after the machining step in order to position the part on another machine and carry out an operation different from machining.

Claims (16)

1. Watch pivot axis (1) comprising at least one pivot (2) at at least one of its ends, characterized in that said pivot (2) is entirely made of an alloy based on CoNiCr without beryllium and comprising by weight : – at least 42% cobalt – between 20% and 30% nickel – between 10% and 18% chromium – between 2% and 5% molybdenum – between 2% and 5% tungsten – between 2% and 10% iron – between 0% and 3% titanium – between 0% and 2% aluminum – possible impurities each having a content less than or equal to 0.5%, the sum of the different elements being equal to 100% by weight. 2. Watch pivot axis according to claim 1, characterized in that said alloy comprises between 42% and 45% cobalt. 3. Watch pivot axis according to one of the preceding claims, characterized in that said alloy comprises between 21% and 26% nickel. 4. Watch pivot axis according to one of the preceding claims, characterized in that said alloy comprises between 12% and 18% chromium. 5. Watch pivot axis according to one of the preceding claims, characterized in that at least the pivot (2) has a uniform roughness Ra less than or equal to 50 nm ± 20%, preferably less than or equal to 25 nm, preferably less than or equal to 20 nm, preferably less than or equal to 15 nm, and preferably less than or equal to 12 nm, more preferably less than or equal to 10 nm, and more preferably between 5 nm and 9 nm, limits included. 6. Watch pivot axis (1) according to one of the preceding claims, characterized in that it is entirely made of said alloy. 7. Watch pivot axis (1) according to one of the preceding claims, characterized in that at least the pivot (2) has a surface hardness greater than 750 HV, and preferably greater than or equal to 780 HV. 8. Watch pivot axis (1) according to one of the preceding claims, characterized in that it is arranged to form a balance axis. 9. Method for manufacturing a watch pivot axis (1) according to one of claims 1 to 8, said method comprising: a) a step of manufacturing a blank of the watch pivot axis (1) comprising, at at least one end, at least one part made of said CoNiCr-based alloy and intended to constitute a pivot (2); And b) a final step consisting of force-free precision machining of at least the part made of said alloy of the blank obtained in step a) in order to obtain at least one finished pivot (2) entirely made of said alloy. 10. Method according to claim 9, characterized in that step a) is carried out by means of a laser beam guided by a water jet or by electroerosion. 11. Method according to one of claims 9 to 10, characterized in that the force-free precision machining carried out during step b) is femto laser turning, electrochemical turning, or electroerosion turning. 12. Method according to one of claims 9 to 11, characterized in that at least the finished pivot (2) made entirely of said alloy obtained in step b) has a uniform roughness Ra less than or equal to 50 nm ± 20%, preferably less than or equal to 25 nm, preferably less than or equal to 20 nm, preferably less than or equal to 15 nm, and preferably less than or equal to 12 nm, more preferably less than or equal to 10 nm, and more preferably between 5 nm and 9 nm, terminals included. 13. Method according to one of claims 9 to 12, in which the watch pivot axis is made entirely of said alloy, said finished pivot axis (1) comprising functional portions having a surface of revolution and comprising at least said pivot, characterized in that the axis blank obtained in step a) corresponds to the functional configuration of the finished pivot axis (1), with the exception of the parts intended to constitute the functional portions and in this that step b) is implemented at least on the parts intended to constitute said functional portions in order to obtain said finished pivot axis (1). 14. Method according to one of claims 9 to 13, characterized in that it does not include, after step b), any finishing step, and in particular no tribological treatment step. 15. Watch movement comprising a watch pivot axis (1) according to one of claims 1 to 8. 16. Timepiece comprising a watch movement according to claim 15 or a watch pivot axis (1) according to one of claims 1 to 8.