• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for manufacturing a spring for a timepiece comprising at least one monolithic ribbon of metal glass comprising at least one curvature. This method is distinguished in that it comprises a step of shaping by plastic deformation of said monolithic ribbon to obtain at least a portion of said curvature. The present invention relates to a method of manufacturing a spring for a timepiece which comprises at least one monolithic ribbon of metal glass comprising at least one curvature.
    公开号:CH704391B1
    申请号:CH00793/12
    申请日:2010-12-09
    公开日:2016-01-29
    发明作者:Thomas Gyger；Vincent Von Niederhäusern
    申请人:Rolex Sa；
    IPC主号:
    专利说明:

    [0001] The present invention relates to a method of manufacturing a spring for watchmaking which comprises at least one monolithic strip of metallic glass comprising at least one curvature.
    [0002] Document EP 0 942 337 has already proposed a watch comprising a mainspring made of amorphous metal. In reality, only a blade formed from an amorphous metal laminate assembled with epoxy resin is described in this document. Alternatively, a blade assembly by spot welding the two ends and the inflection point of the free form of the spring has been proposed.
    [0003] The major problem with such a blade is the high risk of delamination of the laminate during its shaping and following the repeated windings and unwinds to which such a spring is subjected. This risk is all the more accentuated as the resin ages poorly and loses its properties.
    [0004] This solution does not make it possible to guarantee the functionality and the fatigue behavior of the spring. In addition, the modeling of the proposed theoretical shape of the spring does not take into account the behavior of a layered material.
    The use of several thin strips assembled is due to the difficulty of obtaining thick metallic glass blades, the known methods, developed in the 1970s for amorphous ribbons used for their magnetic properties, do not making it possible to manufacture ribbons up to about thirty microns by rapid quenching.
    [0006] The international application published under the number WO 2007/038882 describes a composite material composed of a substantially continuous amorphous matrix comprising graphite particles. This composite material is believed to be suitable for use in the manufacture of springs in particular, however, no indication is given as to the method of manufacture of such springs. In addition, the size of the particles dispersed in the matrix of the composite is of the same order of magnitude as the typical thickness of watch springs, which raises doubts about the use of such a composite for this application.
    US Pat. No. 5,772,803 relates to an object comprising a torsion spring obtainable by cooling at a speed below 500 ° C / s of a liquid metal alloy in order to obtain a solid amorphous metal alloy , then shaping of this alloy. The only shaping mentioned in this document is casting in a mold. It so happens that the casting of an alloy with high mechanical performance, in particular high elastic limit, produces ribbons which are fragile in bending in the dimensions necessary to make a barrel spring.
    [0008] French patent No. FR 1,553,876 relates to a device and a process for the manufacture of watch balance springs. The nature of the bands used for the manufacture of these balance springs is not indicated in this document. Given the age of the document, it can be assumed that this is a polycrystalline metal alloy for self-compensating Invar <®> type spiral springs, such as the Nivarox <®> alloy (FeNi base alloy).
    [0009] United States Patent No. US 3,624,883 relates to a method of manufacturing a spring wound in a spiral and fixed to a ferrule comprising the attachment of a tape to a ferrule and then driving the latter in rotation. and subjecting the assembly to heat treatment to fix the tape in its wound position. The nature of the tape is not indicated in this document. This patent claiming priority dated 1968, and taking into account the description, it is likely that the tape was made of polycrystalline metal alloy for spiral springs (hair spring) of the same type as that described in French patent n ° FR 1 553 876 cited above. It is known to those skilled in the art that the role and therefore the properties of the spiral spring are very different from that of the mainspring or barrel spring.
    [0010] The application of the aforementioned technique to metallic glasses is therefore not obvious because of the great differences existing between a crystalline metallic alloy and an amorphous metallic alloy called "metallic glass".
    As indicated in the “Background of the invention” part of the aforementioned international application No. WO 2007/038 882, solid metallic glasses are fragile and therefore their plastic deformation at room temperature is strongly discouraged.
    Likewise, in their article entitled "Deformation behavior of the Zr4i.2Ti13.8Cu12.5Ni10Be22.5bulk metallic glass over a wide range of strain-rates and temperatures", Acta Materialia 51, 3429-3443 (2003), the authors J. Lu et al. declare “In spite of their metallic bonding, all the metallic glasses discovered so far exhibit shear localization at room temperature, leading to catastrophic shear failure immediately following yield” (cf. p. 3430, 2 <è> <me> paragraph).
    [0013] The plastic deformation of an amorphous metal alloy is only possible by the creation of sliding bands. This deformation mechanism is totally different from that of crystalline metal alloys. Plastic deformation of an amorphous metal alloy is generally unwanted, as it results in rapid breakage of the stressed part.
    [0014] It is therefore clear to those skilled in the art that the elastic limit is a limit that should not be crossed, otherwise the material could be damaged. Therefore, for those skilled in the art, any plastic deformation of a solid metallic glass should be avoided.
    Another fundamental difference between a multiphase polycrystalline alloy such as Nivaflex <®> (basic high performance spring alloy CoNiCr) and an amorphous metal alloy is that, in order to be able to achieve its maximum mechanical properties, the Nivaflex <® alloy > must be hardened by work hardening and by phase precipitation during heat treatment. In the case of an amorphous metal alloy, its mechanical characteristics are obtained during solidification and its mechanical properties cannot be improved by plastic deformation and / or subsequent heat treatment. Thus, it is necessary to apply a heat treatment to the Nivaflex <®> barrel springs to obtain the desired mechanical properties, which is not the case for a metallic glass spring.
    Summary description of the invention
    The inventors discovered with surprise that it was possible to subject a plastic deformation to a metallic glass ribbon, and to use it industrially with its plastic deformation, in particular in the form of a spring loaded mechanically so repeated in the barrel of a watch movement.
    [0017] They then took advantage of this discovery in a method of manufacturing a spring for a timepiece according to claim 1.
    [0018] This process therefore makes it possible to manufacture functional watch springs in metallic glass, in particular barrel springs, on an industrial scale.
    The characteristics and advantages of the method which is the subject of the invention will become apparent from the following description, illustrated by various diagrams. Fig. 1 is a ductility / brittleness diagram as a function of the annealing conditions; fig. 2a is a diagram of fixing at different temperatures; fig. 2b is a diagram of the strain at break as a function of the annealing time at different temperatures; figs. 3a, 3b are diagrams corresponding to those of FIGS. 2a respectively 2b for another alloy; figs. 4a, 4b are diagrams corresponding to those of FIGS. 2a respectively 2b for another alloy; fig. 5a is a plan view of the free form of a spring; fig. 5b is a plan view of the free form of this same spring, the curvatures of which correspond to 60% of the theoretical free form; and fig. 6a, 6b represent the winding / unwinding curves of a barrel spring, part of which has been hot-shaped and the internal part has been shaped by plastic deformation, respectively of a barrel spring whose setting shaping was carried out entirely by plastic deformation (cold forming), with the torque in [mNm] as a function of the number of development turns.
    Detailed description of the invention
    For the implementation of the method according to the invention, using a metal alloy capable of forming by cooling an amorphous or essentially amorphous metal alloy, called "metallic glass", because of the excellent mechanical properties resulting from their particular structure .
    [0021] It is particularly advantageous to use metallic glasses whose mechanical properties are superior to those of the traditional polycrystalline alloys used in the prior art, such as, for example, the Nivaflex <®> alloy. Therefore, the invention presented below relates more particularly to metallic glasses whose elastic limit is greater than 2400 MPa.
    As examples of such amorphous metal alloys, mention may be made of alloys based on Ni, Co and / or Fe.
    During their research, the inventors have also found that to achieve a functional spring, that is to say guaranteeing a certain return torque and good reliability when used in a timepiece, the tape should preferably be made of an amorphous or substantially amorphous alloy with the thickness required to achieve the functional properties and to be initially ductile in flexure. Indeed, beyond a certain thickness, the tape can show a fragile behavior in bending, which would degrade the reliability of the spring.
    [0024] To obtain a high performance watch spring, such as a barrel spring, the thickness of the strip will advantageously be at least 50 μm, since thinner thicknesses do not allow sufficient return torque to be obtained. Likewise, the thickness will advantageously be at most 150 µm.
    According to an advantageous embodiment of the invention, both a low thickness and an amorphous character are obtained by hyperhardening, or by projecting the liquid metal alloy capable of forming the metal glass on a cold and moving substrate , such as a rotating cylinder, possibly a water cooled rotating cylinder.
    Such a projection can be carried out for example by implementing a method such as "planar flow casting" (in English "Planar flow casting"), "quenching on a wheel" (in English "Melt-spinning" ) and the “casting between rolls” (in English “Twin roll casting”).
    Preferably, the projection and cooling parameters are chosen so as to obtain a cooling rate of the liquid metal alloy greater than 10,000 ° C / s. Such a cooling rate, obtained by hyperquenching, in fact promotes ductility by the formation of “free volume” in the structure of the metallic glass.
    The cooling rates obtained by using a molding technique, such as for example the injection of the liquid metal alloy in a copper mold, are significantly lower and do not allow, for metal glasses with high elastic limit which we are aware of, to obtain both sufficient thickness and ductility for the proper function of a high performance watch spring.
    [0029] In addition, it is desirable that the projection be carried out so as to obtain a monolithic ribbon having a thickness between 50 and 150 μm, preferably between 50 and 120 μm, and more preferably between 50 and 100 μm. The metallic glass obtained under these conditions is then clearly different from the solid metallic glass ("Bulk metallic glass (BMG)", whose thickness is greater than 1 mm.
    In the case of the barrel spring, the spring cannot be used directly after casting in the form of a rectilinear strip, but must be shaped in order to be able to develop the desired torque, as described in document WO 2010/000 081 A1. It is therefore necessary to be able to shape the ribbon so that it takes a given free form, before the steps of stretching and winding in a barrel.
    As regards the shaping of the monolithic metallic glass ribbon, the plastic deformation is advantageously carried out at room temperature and in an ambient atmosphere. This plastic deformation must not degrade the mechanical properties of the tape, so as to allow its repeated mechanical stress, for example in a barrel.
    According to an advantageous embodiment of the invention, in addition to the curvature produced by plastic deformation, an additional curvature is produced by deforming the tape elastically, for example in a fitting, and by fixing the new shape obtained with a heat treatment at a temperature and for a period of time not leading to weakening of the spring. This additional curvature can in particular be achieved on the parts of the tape which are not curved by plastic deformation. The heat treatment can be carried out before or after the plastic deformation, advantageously before the plastic deformation, in particular if the heat treatment affects the plastically deformed zone.
    The appropriate temperature and duration of treatment (annealing) are chosen within a window of temperature and time in which the alloy of said metallic glass retains its ductile behavior in bending. This window thus corresponds in practice to a strain at break greater than 2%. These conditions make it possible to achieve the following objectives: i) extending the limit treatment time before embrittlement, ii) fixing the shape, iii) maintaining the mechanical properties obtained after manufacture of the tape (hardness and ductility) and iv) preventing crystallization.
    Example 1
    Ribbons of Ni53Nb20Zr8Ti10Co6Cu3 (elastic limit: 2600 MPa) were produced by "planar flow casting", which consists in forming a flow of liquid metal on a cooled wheel. 10 to 20 g of the alloy are placed in a dispensing nozzle heated to 1050 to 1150 ° C. The slot width of the nozzle is between 0.2 and 0.8 mm. The distance between the nozzle and the impeller is between 0.1 and 0.3 mm. The wheel on which the molten alloy is deposited is a copper alloy wheel and driven at a speed of 5 to 20 m / s. The pressure to force the molten alloy out through the nozzle is between 10 and 50 kPa. Table 1 below gives the characteristics of three ribbons obtained. 1 900 84 0.8 1.23 0.01 ductile 2 500 109 1.1 1.44 0.02 ductile 3 1700 81 0.8 1.37 0.02 ductile
    Table 1 - Characteristics of three ribbons used in Ni53Nb20Zr8Ti10Co6Cu3 alloy
    The thermal properties were measured by DSC (Differential Scanning Calorimetry) on Setaram Setsys Evolution 1700 at 10 ° C / min under Ar 20 ml / min:- Tg = 558 ° C ± 2 ° C- Tx = 606 ° C ± 1 ° C
    [0037] Tg and Tx are little influenced by the conditions for making the ribbons.
    To determine the fixing coefficient of the shape of the spring, a tape is wound in a ring of internal diameter D0et the diameter taken by the tape after the heat treatment in its free state, or "fixed" diameter Df, is measured. The fixing coefficient is calculated by the ratio between the diameter in the fully relaxed state, assumed to be equal to the internal diameter of the ring D0, and the diameter of curvature of the fixed tape Df.
    We carried out relaxation annealing of fixing of the form on ribbons 30 mm in length, wound inside aluminum rings with an internal diameter equal to 7.8 mm, which is close to typical curvature diameters of a barrel spring. A Logotherm <©> resistance furnace in ambient atmosphere was used. The rings are placed on thermostatted alumina pads in the center of the furnace to guarantee temperature uniformity and rapid heat transmission. The treatment time is counted from the moment the oven door is closed. One second before the end of the countdown, take the ring with a pair of pliers and very quickly soak it in about 2 liters of room temperature water.
    [0040] Once the ribbon has cooled, the diameter of curvature of the relaxed ribbon is measured with a caliper with an accuracy of 0.2 mm.
    To assess the ductile or fragile nature of the ribbon in bending, the ribbon is placed fixed between the two parallel surfaces of the caliper as in a 2-point bending test. Gap at break is noted by slowly bringing the two parallel surfaces of the caliper together.
    To determine the deformation at break of the ribbon or of the blade, it must be taken into account that the curvature of a blade folded at 180 ° between two parallel surfaces at a distance B from each other n ' is not of constant radius. It passes through a maximum located at the apex. The radius of curvature at the apex is related to the spacing by the following relation, and does not depend on the properties of the material or the dimensions of the tape:
    With:R: the radius of curvature at the apex;B: the distance between two parallel surfaces mentioned previously.
    [0043] The deformation at the apex is approximately expressed by:
    With:ε: the deformation at the apex;R: the radius of curvature at the apex;B: the distance between two parallel surfaces mentioned previously;e: the thickness of the tape.
    For a tape with an initial curvature K0 = 1 / R0 non-zero, the strain at the external fiber becomes:
    With:ε: the deformation at the apex;R: the radius of curvature at the apex;B: the distance between two parallel surfaces mentioned previously;e: the thickness of the tape;K0: the initial curvature.
    The maximum deformation before rupture is obtained εwith the separation at rupture Bret the initial curvature (0.5 D0) <–> <1>. When Br becomes equal to 2 e, the strain is limited to 1.
    The sample is considered fragile if the strain at break is less than 2% (without any prior plastic strain).
    [0047] FIG. 1 shows the mechanical behavior of Ni53Nb20Zr8Ti10Co6Cu3 alloy ribbons with a thickness of 81 microns at the various temperatures and annealing times to which they have been subjected. It can be seen that there is an annealing parameters window that does not weaken the ribbons. This window is large enough to allow for reproducible formatting. The time limit increases by decreasing the temperature. For annealing in a furnace, in the case of this alloy, it is necessary to be placed at more than 50 °, advantageously 100 ° C, below Tg in order to have a suitable time from the technological point of view, that is to say a duration of at least several minutes. With hot air heating followed by quenching, the technologically suitable processing time is shorter (less than a minute) and the temperature may be higher as a result.
    As the stress relaxation following the fixing of the form is not complete, the form after fixing treatment is expanded with respect to the form imposed during annealing. It was noticed that the fixation coefficients D0 / Df for a given temperature were aligned on a sigmoidal curve and that the curve could be modeled by equation (4), which is a model which has been used to describe some aspects of the relaxation of metallic glasses, in particular by Fan et al. (Acta Materialia 52 (2004) 667-674):
    Or:β and t0 are constants;Df: the diameter of the ribbon in the free state after treatment;D0: the internal diameter of the ring;t: the duration of the heat treatment.
    The relaxation of the curvature is faster for a thin ribbon than for a thick ribbon. It has been found that the evolution of the curvature does not depend on the imposed diameter, which makes it possible to have a single fixing coefficient D0 / Df for shaping a spring with variable curvature. The behaviors shown in fig. 2 (a) show that the higher the temperature, the faster the relaxation.
    The essentially amorphous nature of the raw and annealed ribbons was confirmed by X-ray diffraction. Two anneals were analyzed: the first in the ductile domain (430 ° C / 30 min) and the second in the brittle domain (530 ° C / 10 min). Thus, no crystalline phase is detected in any of the samples. However, it should be noted that this characterization technique would not allow the presence of nanocrystals to be detected with certainty, which is therefore not excluded. On the other hand, these nanocrystals can sometimes play a favorable role for the mechanical properties of metallic glasses.
    It emerges from FIGS. 1 and 2a that the higher the temperature, the more the ductile-brittle transition takes place at high fixing coefficients. Thus, for the Ni53Nb20Zr8Ti10Co6Cu3 alloy, only temperatures close to the glass transition allow the shape to be fixed at more than 95% without embrittlement.
    Example 2
    [0052] Figs. 3a, 3b respectively represent fixing and deformation at break curves for a tape 68 μm thick in an amorphous Ni60Ta40 alloy (at.%, Elastic limit: 2900 MPa), of which Tg = 740 ° C and Tx = 768 ° C. These curves resulting from tests at 520 ° and 570 ° C show that the fixing behavior is similar to that of the Ni53Nb20Zr8Ti10Co6Cu3 alloy and that at 520 ° C, embrittlement was not reached for the times tested (up to 30 minutes).
    Example 3
    [0053] Figs. 4a, 4b respectively represent the fixing and deformation at break curves for a 73 μm thick ribbon made of an Ni60Nb10Ta30 alloy (elastic limit: 2700 MPa), whose Tg = 721 ° C and Tx = 747 ° C. These curves also show that the behavior is comparable to that of the two previous alloys.
    The results reported on these various diagrams make it possible to make two observations:i) it is possible to bend a metallic glass ribbon by clamping below its glass transition temperature and ii) there is a range of temperature and processing time in which the alloy remains ductile.
    The sigmoid behavior of expansion and deformation at break as a function of the annealing time or duration, observed on the Ni53Nb20Zr8Ti10Co6Cu3 ribbons, is similar to that of the other alloys tested. This behavior has also been observed on Fe and / or Co-based alloys, some of which do not show a Tg or have a Tg> Tx. We can therefore assume that this behavior can be generalized to other alloys in metallic glasses, and is therefore not limited to Ni-based alloys and / or to those which show a Tg <Tx.
    As a general rule, an alloy must meet a necessary condition so that the shaping below Tg, respectively below Tx for an alloy does not show Tg or with Tg> Tx, is usable for a spring: the superposition of the "fixing" and "ductility" windows. In the cases presented, the time required to fix the shape is significantly less than the time limit which corresponds to the transition to a fragile state.
    [0057] It has already been mentioned that the fixing coefficient depends on the thickness of the tape but not on the imposed curvature. The inventors have verified that it is possible to obtain the theoretical free form of a barrel spring by using a single fixing coefficient by carrying out a copper fitting. A 0.3 mm thick slot has been electro-eroded in a 1.5 mm thick copper plate, with a profile corresponding to the desired free form of the spring but with the radii of curvature contracted to 60% to account for the expansion D0 / Df, while maintaining the length of the different segments of the free form at 100%.
    We put a metal glass ribbon in the slot of the fitting by subjecting it to an elastic deformation and we proceeded to the fixing treatment in an oven under ambient atmosphere between two ceramic pads thermostated at 430 ° C, for 3 min, followed by the quenching of the installation. This treatment corresponds to fixing at D0 / Df = 60% according to the charts obtained by ring fixing. The ribbon, once taken out of its installation, shows a free form corresponding almost perfectly to the desired free form. Figs. 5a, 5b respectively represent the desired free form and the free form with the curvatures contracted at 60% of the laying.
    According to another embodiment of the method, the spring is shaped not in an oven but by a jet of hot gas. A "Sylvania Heater SureHeat Jet 074 719" type device with an output of 8 kW is used to heat compressed air and project it against the backing containing the tape. The device can heat a gas (air, or an inert gas such as argon, nitrogen or helium) up to 700 ° C, the tape being inserted into the slot of the copper liner by elastic deformation as before.
    The copper fitting is placed perpendicularly facing the hot gas distribution tube. It could also be maintained with a certain inclination, for example 45 °. The fitting is mounted on a three-position linear guide system making it possible to i) place the copper fitting in the high position, out of reach of the gas jet ii) position it in the hot gas jet and iii) immediately dip it in a cooling liquid, such as water for example, at the end of the hot treatment.
    [0061] According to yet other embodiments of the method, the installation containing the tape is placed in a vacuum oven, or between two ceramic heating plates, these modes being given by way of non-limiting examples. The shaping can also be carried out in two or more heat treatment steps.
    [0062] So far, we have considered only the fact of fixing a desired shape to an initially substantially straight ribbon, that is to say without any other curvature than that resulting from the manufacture of the ribbon. The shape given corresponds precisely to the shape of the negative, respectively positive curvatures of a barrel spring around a point of inflection. However, the parts at both ends are wound inside circular recesses in the fixture necessitated by limitations due to the thickness of the slot becoming greater than the inter-coil space of the desired free form; they therefore cannot follow the desired shape over the entire length of the spring.
    [0063] With a ribbon of a crystalline alloy for springs commonly used, such as, for example, Nivaflex <®>, the desired shape could be obtained by cold plastic deformation. This is particularly the case for the inner end of the spring ("shell", "shell" step). It is in fact necessary to secure the spring to the barrel shaft: as the theoretical curve of the spring gives radii of curvature greater than that of the shaft, it becomes necessary to bind the curvature formed by the spring around it. the shaft, at theoretical curvature, by a cold deformation of the spring.
    However, this step cannot be transposed directly to metallic glass ribbons: as indicated above, plastic deformation of metallic glasses is strongly discouraged.
    It was surprisingly found that shaping of the tape by plastic deformation was possible, for the various alloys tested, without fragile breakage of the tape and without affecting the mechanical properties of the shaped tape. Such a tape can then be used as a spring, in particular as a high performance spring, more particularly as a barrel spring.
    This unexpected finding thus makes it possible to give the desired final shapes by cold plastic deformation, before or after a possible heat treatment for fixing. This shaping by plastic deformation can be limited to the shell (internal end, see below), but can also be carried out over a larger part of the spring, or even over the entire shape given to the spring.
    [0067] Note here that the squab (cutout at the inner end of the spring which allows it to be hooked to the lug of the barrel shaft bung) is cut by stamping in the traditional way. Other ways of attaching the spring to the barrel shaft can of course be used, such as welding.
    A sliding flange intended to be fixed to the outer end of the spring is made in a strip 110 μm thick of the same alloy as that of the ribbon, obtained by the same technique of "planar flow casting" and setting shaped by cold plastic deformation (see below) to give it the typical curvature of a sliding flange for a self-winding mainspring. The welding is done by resistance (spot) as usual. Other methods of fixing are of course also possible, such as laser welding for example.
    [0069] FIG. 6a shows the winding and unwinding characteristic of an 81 µm thick Ni53Nb20Zr8Ti10Co6Cu3 alloy spring formed by cold plastic deformation for the inner end (shell), then by heating by hot gas jet in a setting as described above, with conditions corresponding to a fixing coefficient of 60%. The spring gives a completely satisfactory behavior, allowing to reach the target torque and number of revolutions, and shows good behavior in fatigue.
    However, the spring measured in FIG. 6a comprises a shell formed by cold plastic deformation over a greater or lesser length (typically 40 mm in the case of FIG. 6a) with good reproducibility, and the barrel spring obtained shows good performance. The inventors therefore wanted to know whether the method of obtaining the curvature of the shell by plastic deformation was applicable to the entire spring.
    The shellfish technique consists in deforming the blade by hammering. The curvature is adjusted by two parameters: the step of movement of the tape between two hammer blows and the amplitude of the deformation, set by the angle of rotation of the hammer around its axis. It is necessary to adapt the parameters according to the alloy and the thickness of the tape.
    The shaping by cold plastic deformation is carried out in two stages: first, the outer end of the tape is introduced in order to apply a negative curvature according to the desired theoretical curvature up to the point of inflection . Then the inner end is introduced in order to apply a positive curvature according to the theoretical curvature.
    [0073] FIG. 6b shows the winding and unwinding characteristic of an 81 µm thick Ni53Nb20Zr8Ti10Co6Cu3 alloy spring formed by cold plastic deformation only. Despite the absence of fixing by heat treatment, the behavior of the spring is in all respects comparable to that of FIG. 6a.
    The shaping of ribbons of metallic glass alloys by plastic deformation is not limited to the sole alloy Ni53Nb20Zr8Ti10Co6Cu3. For example, the alloys of Figs. 3 and 4 can also be shaped by plastic deformation. Other basic amorphous Ni, Fe and / or Co alloys can also be shaped with at least one plastic deformation step, and can be subjected to a fixing heat treatment to obtain additional curvature.
    As can be seen in the above description, it is possible to give a curvature to a strip of amorphous metal alloy at temperatures much lower than Tg, respectively much lower than Tx for an alloy showing no Tg or with Tg> Tx, this for several families of amorphous alloys. The "fixing coefficient", that is to say the ratio between the imposed curvature and the curvature obtained after heat treatment, depends on the thickness of the tape but does not depend on the imposed curvature, thus making possible the setting. shape of a barrel spring with variable curvature. This coefficient also depends on the shaping medium used (oven, gas jet, etc.) and the characteristics of the equipment, since the temperature experienced directly by the tape is difficult to measure accurately.
    In addition, the fixing annealing must not make the ribbon brittle and it must therefore be done at a temperature and for a period below the point of weakness. According to our experience, several amorphous alloys based on Ni as mentioned here, but also based on Fe or Co, show sufficient resistance to annealing embrittlement to apply hot shaping to them.
    The above implies that for an alloy having a good shaping window, several treatments can lead to the same rate of fixing of the form. It is thus possible to choose the treatment conditions so as to maximize the performance of the spring, or even combine the treatments or combine them with one or more cold or hot plastic deformations.
    In the end, it is possible to fix the shape of ribbons made of various alloys, including Ni53Nb20Zr8Ti10Co6Cu3, by plastically deforming the spring near the inner end, or even over its entire length, by completing the shaping by heat treatment in an annealing window at a temperature below Tg and / or Tx, with an industrially applicable treatment time. The tapes remain ductile, do not lose their mechanical strength and retain their amorphous or essentially amorphous character.
    [0079] This process makes it possible to obtain, among other things, functional barrel springs with excellent characteristics.
    The method described above can also be applied to the shaping of springs other than the barrel spring, whether for components of the watch movement (spring of jumper, or sliding flange for barrel spring, for example) or watchmaking clothing, case, or even bracelet.
    权利要求:
    Claims (22)
    [1]
    1. A method of manufacturing a spring for a timepiece comprising at least one monolithic metallic glass ribbon comprising at least one curvature, characterized in that it comprises a step of shaping by plastic deformation of said monolithic ribbon in order to 'obtain at least part of said curvature.
    [2]
    2. Method according to claim 1, wherein the step of shaping by plastic deformation of the monolithic tape is preceded by a step of obtaining this tape which comprises the projection of a liquid metal alloy capable of forming a glass. metallic on a cooled and moving substrate.
    [3]
    3. The method of claim 2, wherein the obtaining of the monolithic metallic glass ribbon is effected by hyperquenching according to one of the methods called "planar flow casting", "wheel hardening" and "roller casting".
    [4]
    4. The method of claim 2 or 3, wherein the spraying is carried out so as to obtain a cooling rate of the liquid metal alloy greater than 10,000 ° C / s.
    [5]
    5. Method according to one of claims 2 to 4, wherein the projection is carried out so as to obtain a monolithic tape having a thickness between 50 and 150 µm.
    [6]
    6. Method according to one of claims 1 to 5, wherein the shaping step by plastic deformation is preceded or followed by a step of fixing at least part of the monolithic tape.
    [7]
    7. Method according to one of claims 1 to 5, wherein the shaping step by plastic deformation is preceded or followed by a step of fixing at least part of said curvature by heat treatment of the. 'at least part of said curvature.
    [8]
    8. The method of claim 7, wherein the fixing step is carried out by elastic deformation of said tape in a setting followed by fixing of the form by said heat treatment.
    [9]
    9. Method according to one of claims 7 and 8, wherein the heat treatment is carried out at a temperature and for a period corresponding to a breaking strain of the metallic glass greater than 2%.
    [10]
    10. The method of claim 9, wherein said heat treatment temperature is less than 50 ° C below the glass transition temperature Tg of said metallic glass or the crystallization temperature Tx for an alloy not showing Tg or where Tg> Tx.
    [11]
    11. The method of claim 10, wherein said heat treatment temperature is less than 100 ° C below the glass transition temperature Tg of said metallic glass or the crystallization temperature Tx for an alloy not showing Tg or where Tg> Tx.
    [12]
    12. Method according to one of claims 6 to 11, wherein the fixing step comprises a fixing coefficient of between 60% and 90%, preferably between 85 and 90%.
    [13]
    13. The method of claim 8, wherein the fitting used for shaping the spring comprises the profile of the spring corresponding substantially to the free shape desired for the spring with radii of curvature contracted as a function of a dependent fixing coefficient. the thickness and the alloy of said ribbon and the temperature and duration chosen for fixing, the length of the segments of said profile corresponding to the actual length of said free form.
    [14]
    14. Method according to one of claims 9 to 11, wherein the fixing step is carried out by an elastic deformation of said tape in a setting followed by fixing of the form by said heat treatment and in which the setting used for the shaping of the spring comprises the profile of the spring corresponding substantially to the free shape desired for the spring with radii of curvature contracted as a function of a fixing coefficient depending on the thickness and the alloy of said ribbon and on the temperature and duration chosen for fixing, the length of the segments of said profile corresponding to the actual length of said free form.
    [15]
    15. Method according to one of claims 13 to 14, wherein the fixing coefficient is between 60% and 90%, preferably between 85 and 90%.
    [16]
    16. Method according to one of the preceding claims, wherein said plastic deformation is carried out at room temperature.
    [17]
    17. Method according to one of the preceding claims, in which a metallic glass having an elastic limit of greater than 2400 MPa is used.
    [18]
    18. Method according to one of the preceding claims, wherein the spring is a barrel spring and the plastic deformation is applied at least to its internal part.
    [19]
    19. Method according to one of claims 1 to 18, wherein the entire spring is shaped by plastic deformation.
    [20]
    20. Method according to one of the preceding claims, in which the spring is a barrel spring comprising positive curvatures, respectively negative, on either side of a point of inflection.
    [21]
    21. Spring, in particular the barrel spring, obtained by implementing the method according to one of claims 1 to 20.
    [22]
    22. Timepiece comprising a spring according to claim 21.
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    同族专利:
    公开号 | 公开日
    US20120281510A1|2012-11-08|
    EP2510405A1|2012-10-17|
    EP2510405B1|2016-03-30|
    CN102713770A|2012-10-03|
    JP2013513781A|2013-04-22|
    CN102713770B|2015-11-25|
    US9104178B2|2015-08-11|
    JP5744050B2|2015-07-01|
    WO2011069273A1|2011-06-16|
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    法律状态:
    2016-12-15| PFA| Name/firm changed|Owner name: ROLEX S.A., CH Free format text: FORMER OWNER: ROLEX S.A., CH |
    优先权:
    申请号 | 申请日 | 专利标题
    EP09405221|2009-12-09|
    PCT/CH2010/000309|WO2011069273A1|2009-12-09|2010-12-09|Method for making a spring for a timepiece|
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