Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F1/00—Springs
  • F16F1/02—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant
  • F16F1/024—Covers or coatings therefor
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B1/00—Driving mechanisms
  • G04B1/10—Driving mechanisms with mainspring
  • G04B1/14—Mainsprings; Bridles therefor
  • G04B1/145—Composition and manufacture of the springs

Definitions

• the present invention relates to the watch industry in general and, in particular, the cylinder springs fitted mechanical watches. It relates more particularly barrels with a large energy storage capacity, and the process for increasing this capacity.
• the barrel spring is housed in a barrel drum which, when armed, transmits a torque that causes the movement of the watch.
• the mainspring is the motor of the mechanical watch and functions as an energy accumulator that the user of the watch recharges when he turns the crown of the winding stem.
• the barrel spring is a rectangular section blade made of steel or in an alloy based on cobalt, nickel and / or chromium. It could also be made of silicon. Ductile and of very high mechanical resistance, it must resist corrosion and very strong stresses without breaking. The unwinding of the blade produces the energy necessary for the operation of the watch. Its shape evolved to a form recognized in S returned (see Figure 1 and "Clockwork Theory" by CA Reymondin et al., Published by the Federation of Technical Schools, Switzerland, 1998). This particular shape makes it possible to produce a relatively constant torque irrespective of the state of arming of the spring. The maximum energy is stored by the spring when the proportion between the area occupied by the latter, when it is armed, and that which remains free in the drum, is about 50%.
• Watch manufacturers have always sought to increase the energy storage capacity of the barrel springs and, thus, the power reserve of mechanical watches, without increasing the volume, that is to say clutter, barrels. Efforts have mainly been directed towards the reduction of energy losses, particularly due to friction. Thus it has been proposed to coat the barrel spring with a lubricating layer, for example in DLC ("Diamond-Like Carbon”), to limit internal friction. Such a layer had a typical thickness of a few tens of nanometers.
• DLC Diamond-Like Carbon
• the international application WO 2007/000271 A1 describes more generally a silicon part, such as a spiral mounted in a watch movement, all or part of the surface is coated with a thick amorphous material.
• This thick amorphous deposit is at least partially coated with a coating chosen for its tribological properties, such as DLC.
• An object of the present invention is to provide a cylinder spring having an increased energy storage capacity compared to devices of the prior art.
• Another object of the invention consists in the production of a mainspring having an increased energy storage capacity without having recourse to an upper volume of the drum barrel. Yet another object of the invention is the realization of a barrel spring having a better wear resistance.
• Yet another object of the invention is the presentation of a method for producing a cylinder spring with improved performance.
• the rigidity of the barrel springs In order to increase the energy storage capacity of the barrel springs, it is proposed to increase the rigidity by ionic implantations. In addition, it is proposed to coat the barrel springs with a hard layer in order to increase their resistance to wear.
• the hard coating layer is a DLC layer. If the hard layer is deposited on a surface having an ion implantation according to the present invention, the rigidity of the mainspring and thus its energy storage capacity can be further increased.
• the increase in rigidity resulting from ion implantation substantially increases the energy storage capacity of the mainspring according to the invention or in other words to increase the energy it is able to store without requiring additional volume.
• the life of the mainspring is also substantially increased by the hard layer deposited on its surface.
• FIG. 1 shows an example of a barrel spring unrolled from its drum
• FIG. 2 illustrates a barrel spring having implanted ions and a coating of a hard layer
• FIG. 3 schematically shows a DLC deposit equipment.
• the authors of the present invention have discovered that it was possible to increase the energy storage capacity of a barrel spring by increasing its rigidity. This can be increased by the ion implantation over all or part of the length and / or section of the surface of the mainspring.
• the rigidity can be further increased by the deposition of a hard layer on all or part of its surface.
• ion implantation refers to a deposit or in other words an ion penetration of, for example, Ti, Mo, Yb, Cr, Mn, C, N, Ar, O or B, under the surface of the mainspring.
• the implantation can be carried out on certain faces and / or on part of the length of the mainspring and to a well controlled variable depth.
• the mainspring can be made of steel, and more particularly of stainless steel, or of an alloy, such as cobalt, nickel, chromium, Nivaflex, phosphorous bronze, copper, beryllium , brass or a special alloy.
• Nivaflex is preferable because it is 100% stainless, non-magnetic, indefatigable, and has a very high coefficient of elasticity.
• the ion implantation is done at low temperature, and preferably at a temperature below 200 0 C, by bombarding the respective surfaces of the mainspring by means of accelerated ions with an energy of about 1 to
• the implantation doses may vary from 10 15 to 10 18 at / cm 2 .
• the accelerated ions penetrate the respective surfaces of the spring to a depth of 1 to 2000 nm. The exact depth depends on several factors, such as the type of ion, their energy, the type of spring material, the temperature of the mainspring, the presence of channels and the irradiation defects.
• the ion implantation and penetration of ions / atoms under the surface is achieved using different types of stimulation, including bombardment of accelerated ions and its path inside materials. Their diffusion is stimulated by the temperature or "ion beam mixing" for a diffusion and mixing of the atoms at the interface, stimulated by bombardment of the "third" ions ("nock in surface atoms inside of spring").
• the rigidity of the surface of the mainspring to a certain depth of the material used for its realization can advantageously be increased, and then becomes greater than that of the base material.
• the stiffness of the spring can be increased by one factor 2 to 5 by ion implantation generating internal stresses in the penetration zone of implanted or diffused ions, as well as residual stress by the change of its microstructure (amorphization). This microstructure change penetrated beneath the implanted zone, also inducing an increase in local hardness and rigidity with deep evanescence. Since ion implantation is a well controllable process, it does not result in a change in the dimensions of the mainspring, such as its thickness.
• the bending stiffness of the mainspring according to the invention varies approximately as six times the product of the relative stiffness of the zones modified by the implantation depth of the ions. For maximum efficiency, it is recommended to perform ion implantation throughout the length of the spring and all surfaces. However, implantation on part of the surface is also possible. The ion implantation at different depths by bombardment with ions having a different energy therefore makes it possible to achieve more constant spring-barrel spring torques in time.
• FIG. 2 illustrates a barrel spring 4 having a surface 8.
• ions 9 are implanted under the surface 8, as described above.
• a hard layer In order to maximize the rigidity of the barrel spring 4, a hard layer
• FIG. 2 represents ions 9 implanted under the entire surface 8 of the mainspring spring 4, whereas the hard layer 10 is only deposited on a part of said surface.
• the zone of evanescence 11 of hardness and rigidity below the implanted zone is also represented in FIG. 2.
• the material of the deposited layer 10 must not only have a rigidity significantly greater than that of the base material used to make the barrel spring 4, but also have the proper mechanical properties to allow it to withstand the stresses applied to the mainspring 4. Concerning the deposition of the hard layer 10, it is recommended that it be carried out at a temperature below 100 ° C. and, if possible, at a temperature below 80 ° C. so as not to modify the intrinsic qualities of the spring 4.
• the preferred deposition material is DLC.
• the DLC layer 10 has an interface with a stiffness gradient between it and the surface
• the deposition of the DLC layers of different thickness over the barrel spring length makes it possible to achieve barrel spring running torques more constant over time.
• the DLC has, in addition, the advantage of being amorphous, perfectly inert, non-magnetic and hydrophobic and has, in known manner, tribological properties. In addition, it has very low temperature elastic drifts and negligible aging effects.
• a thickness of a few nanometers is sufficient, whereas to achieve the present invention it is necessary to deposit a greater thickness of
• the deposition process must be performed at low temperature to avoid modifying the properties of the base material.
• Figure 3 schematically shows equipment to satisfy this condition. It uses an improved principle of the PVD method ("Physical Vapor Deposition") called VAD ("Vacuum Arc Deposition" according to the English terminology).
• the equipment shown schematically in FIG. 3 illustrates this principle and comprises a source 3 for emitting carbon ions and the mainspring
• the source 3 comprises a cathode 31 made of graphite and an anode 32.
• An electric field of typically 20 kV is applied between the anode and the cathode, thus constituting a kind of charged capacitor.
• the emission of carbon ions is triggered by a low frequency signal (about 10 Hz).
• the ion implantation functions in a manner similar to the pulsed ion bombardment described above.
• the essential difference between these two processes is that the ions are accelerated and have a much higher energy during their implantation.
• Ti titanium
• This layer of Ti can be deposited using the equipment
• the titanium layer smooths the surface of the mainspring 4 and thus reduce the risk of development of microcracks in the deposited layer.
• the DLC is, for its properties, the preferred deposition material, it is possible to envisage the use of other hard materials, such as crystalline diamond, titanium carbide or nitride, etc.
• the material used should, however, be compressive.
• the ion implantation and the deposition of a hard layer increase the bending stiffness of the mainspring and have the consequence of increasing the torque applied to the movement of the associated mechanical watch.

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• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Springs (AREA)

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• 2008
  • 2008-04-24 EP EP08735379A patent/EP2243056A1/de not_active Withdrawn
  • 2008-04-24 WO PCT/EP2008/003316 patent/WO2009043391A1/fr not_active Ceased

Non-Patent Citations (1)

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