Method for manufacturing a guide device with roller bodies for a medical mechanism

Abstract

The invention relates to a method for manufacturing a rolling bearing (100) for a medical guide device with roller bodies, comprising components, at least one component (20; 6, 2, 4, 5, 5') being made of titanium or of titanium alloy, the method comprising the steps of - using the component made of titanium or of titanium alloy; - carrying out a hardening treatment by diffusion of the machined component, so that the component comprises a superficial layer (21) having a hardness in the range of 900 Hv – 1100 Hv. The invention makes it possible to manufacture a medical guide device with roller bodies from a material that does not have a priori the properties necessary for these applications.

Description

Method for manufacturing a rolling body guide device for a medical mechanism technical field

[0001] The present invention relates to a method for manufacturing a rolling body guide device for watchmaking, medical, semiconductor, or ion-beam applications. It also relates to a watchmaking mechanism, a medical device, a device for the semiconductor industry, or ion-beam applications comprising such a rolling body guide device. State of the art

[0002] The term "rolling body guide device" refers to a device comprising (at least) a first element, (at least) a second element, and rolling bodies held between the first and second elements to facilitate the relative movement of the first element with respect to the second, or vice versa. A rolling body guide device in this context has a maximum static load coefficient C0 of 2000 N, a maximum dynamic load coefficient C of 2000 N, and rolling bodies with a maximum diameter of 1.6 mm.

[0003] In this context, the expression "rolling body" indicates any body that can roll, for example and without limitation, a ball or a roller, for example a cylindrical roller, conical roller, a needle, etc.

[0004] A rotary bearing is an example of a rolling body guide device. It generally comprises (at least) an outer ring (the first element), (at least) an inner ring (the second element, i (which generally comprises two parts fixed together) and rolling elements held between the outer and inner rings. A cage may, in some cases, be used to space the rolling elements between the rings.

[0005] Generally, the cage (also called the rolling element separator) is a single piece. The rolling elements located between the inner and outer rings of the bearing are typically held at a regular distance by the cage, which guides them and facilitates their rotation. The cage can also be composed of several independent segments. The cage can also perform functions in addition to maintaining the rolling elements' distance, for example, but not limited to, a locking function.

[0006] The number of contact points (e.g., in the case where the rolling bodies are balls) or contact lines (e.g., in the case where the rolling bodies are rollers) of the rolling bodies with the rings can vary depending on the type of bearing.

[0007] The surface on which rolling bodies roll is generally called the "rolling track". It supports the loads (axial and / or radial) applied to the rolling.

[0008] A linear bearing is another example of a rolling body guide device. It generally comprises a bushing (the first element), a shaft (the second element), and rolling bodies held between the bushing and the shaft. A linear bearing may include a cage that serves to hold the rolling bodies and allow their recirculation. In this case, the cage does not act as a rolling body separator. There is also a configuration in which the rolling bodies are inserted into a cage that functions as a rolling body separator. In this case, there is no rolling body recirculation.

[0009] A screw-to-screw is another example of a rolling body guide device. It generally comprises a nut (the first element), a screw (the second element) and rolling bodies held between the nut and the screw.

[0010] In general, rotary bearings are used to support and guide elements to be rotated, such as, but not limited to, gears, screws, shafts, etc.; linear bearings are used to guide elements that move linearly, such as, but not limited to, a shaft; ball screws are used to transform rotary motion into linear motion and vice versa, while minimizing friction (and maximizing efficiency).

[0011] In order to ensure the proper functioning of a rolling body guidance system and guarantee its lifespan, certain properties of its components are desired, including: - high precision of rolling body geometry (e.g. ISO Grade 3); - good mechanical properties, for example hardness and Young's modulus (especially for rolling bodies, for rolling areas on the paths of the rolling bodies of the first and / or second element); - geometric conformity of the rolling faces, both of the first element and the second element.

[0012] Titanium or a titanium alloy offers a combination of properties that are advantageous for a wide range of mechanical applications, in particular: - its relatively low density for dynamic applications; - its chemical stability for applications in contact with external environments; - its low magnetic permeability for applications in which a remanent magnetic field is detrimental.

[0013] In addition to these characteristics, the chemical biocompatibility of titanium or a titanium alloy makes it a suitable material for the medical field.

[0014] In this context, the term "titanium alloy" refers to an alloy (particularly a metal) that includes titanium and other chemical elements. Non-limiting examples of titanium alloys include a, a / o, P, o phase alloys, etc.

[0015] However, the low Young's modulus and / or limited hardness (e.g., compared to steel) of titanium or a titanium alloy do not allow its use for certain applications.

[0016] In the case of watch or medical bearings, titanium or a titanium alloy would be a material of choice for the aforementioned reasons, particularly its insensitivity to magnetism and its biocompatibility. Its low density is also an advantage that can prove crucial for certain applications.

[0017] Young's low modulus is not a hindrance to the use of titanium in watchmaking or medical rolling body guidance devices.

[0018] However, the very limited hardness that titanium can achieve is a limiting factor for its application in the field of rolling body guidance devices for watchmaking or medical applications.

[0019] These components are designed to withstand significant loads while maintaining a compact size. For example, the maximum diameter of the external element (outer ring or bushing) of a rolling body guide for a watch or medical mechanism is 28 mm. The materials used must therefore exhibit superior mechanical properties. The stresses at the contact point between the balls and bearing surfaces are extremely high, for example point stresses on the order of 4600 MPa in the watchmaking or medical field.

[0020] To ensure the proper functioning of the rolling body guide during use, a high surface hardness is required in the watchmaking and medical fields. The higher the hardness, the better the rolling body guide will be able to withstand significant loads and the stresses associated with daily use, thus extending its lifespan.

[0021] There is a wide variety of processes that give titanium significant surface hardness.

[0022] Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) deposition treatments allow the depositing of layers from a few nanometers to a few micrometers on the surfaces of titanium components.

[0023] These treatments, such as TiN / CrN / TiC / TiCN, etc., which are regularly used for cutting tool surfaces, have shown satisfactory results for a large number of applications. However, in the case of rolling body guidance devices for watchmaking and / or medical applications, the maximum deposition thickness, on the order of a few micrometers, does not allow for effective load transfer.

[0024] Furthermore, the sharp boundary between the deposit and the base layer generates a discontinuity that is unfavorable to charge transfer between the deposit and the base layer.

[0025] Diamond-like carbon (DLC) treatments are a sub-family of PVD treatments. They allow the deposition of a carbon layer with a thickness generally between 0.5 pm and 3 pm. adopting a partial diamond structure, the layer consists of a fraction of carbon in diamond form (sp3 hybridization state), a fraction of graphite / graphene (sp2 hybridization state), and may also contain a certain amount of hydrogen. The properties of the layer depend on the proportions between these three constituents.

[0026] DLC coatings present drawbacks for watchmaking and / or medical rolling body guidance devices, despite their high surface hardness. The thinness of the coating layer is insufficient to withstand the loads. Combined with variable (and often weak) adhesion of the coating to the surface, cases of layer fracture and delamination occur, rendering this treatment unsuitable.

[0027] A titanium or titanium alloy surface can be anodized to impart color. Anodizing titanium or a titanium alloy also alters the coefficient of friction and the surface topology of the base component. However, the properties of anodized titanium or titanium alloy coatings are insufficient to withstand the stresses of a rolling body guide device, such as a watch bearing.

[0028] Micro-arc oxidation also allows the creation of a dense surface layer on alloys with naturally dense passive oxide filaments. The alloy part is immersed in a basic bath, and an alternating electric current is applied. The resulting electric arcs oxidize the surface to a thickness of approximately 10 µm to 150 µm. Only the lower layer (about 65%) is dense; the outer surface is porous and must be removed.

[0029] The surface roughness induced by this treatment is detrimental to the freedom characteristics necessary for the proper functioning of a rolling body guidance device in watchmaking or medical applications. Furthermore, the dimensions of the components of rolling body guidance devices Watchmaking and / or medical applications are below the limits of achievement with this technique.

[0030] Structural hardening of titanium or a titanium alloy is also possible, but the hardness values ​​achieved by this treatment do not meet the requirements of watchmaking or medical rolling body guidance devices.

[0031] Electroplating processes allow the deposition of materials of various types. Hardened electroless nickel can achieve high hardness, but the risk of delamination during the treatment prevents its use in high-load applications.

[0032] In summary, it is not currently possible to manufacture rolling body guidance devices in materials (such as titanium or a titanium alloy) that do not a priori possess the properties necessary for the watchmaking or medical field.

[0033] Document FR2136037 concerns a hardening process for metal parts such as watch cases, machete handles, etc., which must meet aesthetic requirements due to their visible surfaces. The part is made of titanium and is first shaped and then exposed to high temperature (approximately 1100 °C or 1400 °C - 1500 °C) and low pressure to the diffusion of oxygen, nitrogen, hydrogen, or a mixture of these gases, and then rapidly cooled. The treatment is carried out at low pressures and for a limited time.

[0034] Document CH539128 is similar to document FR2136037.

[0035] Document EP1146136 concerns an ornament, such as an external ornamental part of a watch, which comprises a substrate made of stainless steel, titanium, or a titanium alloy. First, an external force is applied to create a deformed layer 2 m thick. at 100 |im. Then a hardened layer with a thickness of 5 .m to 50 .m is formed by diffusion of a carbon, nitrogen or oxygen atom at a temperature of 100 °C to 500 °C. A hard coating film such as TiC or TiN is deposited on the hardened layer.

[0036] The US2020199725 document describes a hardening process for achieving a surface hardness of 900 HV or more, which is sufficient to provide scratch resistance for components of watches, jewelry, eyeglasses and the like where visual appearance is important. Brief summary of the invention

[0037] One aim of the present invention is to propose a method for manufacturing a medical rolling body guidance device free from the limitations of known bearings.

[0038] Another objective of the invention is to propose a method for manufacturing a medical rolling body guidance device in a material that does not a priori have the properties necessary for a medical rolling body guidance device.

[0039] Another objective of the invention is to propose a method for manufacturing a medical rolling body guidance device that meets the requirements of watchmaking or medical rolling body guidance devices.

[0040] According to the invention, these goals are achieved in particular by means of a method for manufacturing such a rolling body guide device according to claim 1, and by means of a rolling body guide device according to claim 10.

[0041] The invention relates to a method for manufacturing a rolling body guide device for a medical mechanism, comprising components, these components comprising: - a first element, - a second element, - rolling bodies arranged between the first element and the second element, to facilitate the relative movement of the first element with respect to the second element or vice versa, at least one component being made of titanium or titanium alloy, the process comprising the steps of - to implement, for example by machining, the component in titanium or titanium alloy, - perform a diffusion hardening treatment of the machined component, so that the component includes a surface layer having a hardness in the range of 900 Hv - 1100 Hv.

[0042] According to the invention, a titanium or titanium alloy component of a medical rolling body guidance device is first machined (in its "soft" state, i.e. before hardening), and then it is hardened by diffusion.

[0043] The process therefore consists of implementing, for example machining, at least one component of the rolling body guidance device in a material that does not have the necessary properties for a medical rolling body guidance device, and then hardening it so that it has these necessary properties.

[0044] This does not preclude the possibility that, in one variation, the component may be reworked (or re-machined) after the hardening treatment. It is also possible that the hardening treatment may need to be repeated after this subsequent re-machining step, if necessary.

[0045] The use of titanium or a titanium alloy to make a medical rolling body guidance device is surprising, as its hardness is not sufficient for such devices.

[0046] Among all the known hardening processes for titanium or a titanium alloy, the applicant selected a specific type of hardening treatment, known in watchmaking, particularly for watch cases, but not for rolling body guide devices.

[0047] This specific type of hardening treatment was known to improve the aesthetic appearance of a watch case. Often, aesthetics are not important for a rolling body guide device, which generally remains hidden from the user of the part or device in which it is mounted. Therefore, the applicant had no incentive to try this type of known treatment.

[0048] Furthermore, medical rolling body guide devices are small compared to parts hardened with this type of known specific hardening treatment. For example, the maximum diameter of the external element (outer ring or bushing) of a rolling body guide device for a medical mechanism is 28 mm. Since small parts react differently to thermal cycles, for example by deforming, the applicant again had no incentive to try this type of known treatment.

[0049] This solution has the advantage over the prior art of obtaining for (at least) one component of the rolling body guidance device of which at least one component is made of titanium or titanium alloy, with a surface layer having a hardness in the range of 900 Hv - 1100 Hv, which makes it suitable for the medical field.

[0050] Furthermore, the Young's modulus of the treated component material, as well as its geometric dimensions, are not or only slightly affected by the diffusion hardening treatment, which only modifies its surface hardness, improving it.

[0051] The aesthetic appearance of the treated component is slightly altered compared to that of the untreated component (the color is a little darker and more matte). However, in medical rolling body guidance applications, this slight alteration is insignificant. If necessary, after the hardening treatment, a few micrometers of the surface layer can be removed, for example, by etching, to achieve an aesthetic appearance more similar to that of the untreated component.

[0052] It is essential to implement, for example by machining, first the component of the medical rolling body guidance device, and then to harden it, because otherwise during its machining the high risk of removing a large part of the surface layer (namely the hardened or treated layer) would not allow obtaining a quality rolling body guidance device, suitable for the medical field.

[0053] In one variant, the surface layer is defined between an external surface and an internal surface, the internal surface being adjacent to a base layer (i.e., an untreated layer) of the component, the process comprising the step of: - carry out a hardening treatment by (purely or predominantly) interstitial diffusion, so that the hardness of the surface layer decreases from the external surface to the internal surface. In this variant, the gradual decrease in hardness improves the transfer of load between the surface layer and the base layer.

[0054] In another, less preferred variant, diffusion is (purely or predominantly) substitutional.

[0055] According to the invention, the diffusion hardening treatment includes the step of immersing the part in a gas.

[0056] According to the invention, this gas comprises at least one atom selected from carbon, nitrogen, argon or oxygen.

[0057] According to the invention, the process includes the step of selecting a temperature to perform the hardening, for example a temperature substantially higher than the ambient temperature, for example a temperature in the range of 300°C - 1100°C, preferably between 500°C - 800°C.

[0058] In one variant, the process includes the step of temperature control during hardening, in order to allow diffusion while avoiding the growth of unwanted phases or compounds, such as, for example, carbides, nitrides or oxides.

[0059] According to the invention, the process includes the step of selecting a pressure to perform the hardening, for example a pressure greater than atmospheric pressure, for example a pressure that can reach several times atmospheric pressure.

[0060] According to the invention, the hardening treatment time is within the range of 1 h - 24h.

[0061] In one variant, the step of performing a diffusion hardening treatment of the machined component is a final step in the manufacturing process.

[0062] In one variant, the treated component has at least one larger dimension and / or mass compared to that of the desired final component, and the process includes, after the hardening treatment step, the following step: - cut out the treated component, in order to limit deformations due to the hardening treatment.

[0063] Indeed, the hardening process deforms the treated component. It is therefore advisable to treat a component that is at least one size and / or mass larger than the desired component, for example, at least twice as large, in order to limit its deformation during the treatment, and to cut it after the treatment to obtain the component with the desired shape, dimensions and / or mass.

[0064] In a rotary bearing, the clearance depends on the dimensions of the parts. The axial clearance of the bearing is very important because it defines the contact angle of the rolling elements.

[0065] This means that a rotary bearing (for example, a deep groove bearing) must be ground after the hardening treatment. Grinding a component treated with the hardening treatment according to the invention is not possible because the layer thickness is too thin.

[0066] In one embodiment, the guiding device is a rotary bearing; the process includes, after the hardening treatment step, the following step: - Adjustment of axial play in the rotary bearing during assembly of the guide device.

[0067] In one embodiment, the guiding device comprises a first inner ring (cone) and a second inner ring (core), the axial play being adjusted by pressing the first inner ring (cone) onto the second inner ring (core). The invention also relates to a rolling body guiding device for a watch or medical mechanism comprising (at least) a first element and (at least) a second element. Rolling bodies are arranged between the first and second elements to facilitate the relative movement of the first element with respect to the second element, or vice versa.

[0068] According to the invention, at least one component is made of titanium and / or titanium alloy and comprises a surface layer of treated titanium and / or treated titanium alloy, said surface layer having a hardness in the range of 900 Hv - 1100 Hv.

[0069] This hardness allows for efficient load recovery and meets the requirements of rolling body guidance devices in watchmaking or medical applications.

[0070] In one variant, the surface layer is defined between an external and an internal surface, the internal surface being adjacent to a base layer (i.e., an untreated layer) of the component, with the hardness of the surface layer decreasing from the external to the internal surface. In this variant, there is a continuity that facilitates load transfer between the surface and base layers.

[0071] In one variant, the surface layer 21 has a thickness within the range of 5.m - 50 |im. This thickness also allows sufficient load-bearing capacity for the watchmaking and / or medical fields.

[0072] In one variant, the components include a cage arranged to hold the rolling bodies.

[0073] In one variant, the rolling body guide device is a rotary bearing.

[0074] In one variant, the rolling body guide device is a linear bearing.

[0075] In one variant, the rolling body guide device is a ball screw.

[0076] The present invention also relates to an implantable medical device comprising the rolling body guidance device according to the invention. In one embodiment, the rolling body guidance device according to the invention is used to minimize friction loss and / or increase the lifespan of medical implants. Brief description of the figures

[0077] Examples of implementation of the invention are given in the description illustrated by the accompanying figures, in which: Figure 1 illustrates a perspective view of an example of a clockwork mechanism comprising a rotary bearing according to an embodiment of the invention. Figure 2 illustrates a top view of the clockwork mechanism of Figure 1. Figure 3 illustrates a cross-sectional view along plane BB of the clockwork mechanism of Figure 2. Figure 4 illustrates a top view of part of the bearing of the clockwork mechanism of Figure 1. Figure 5 illustrates a perspective view of the bearing in Figure 4. Figure 6 schematically illustrates the steps of the manufacturing process according to the invention. Figure 7 illustrates a cross-sectional view of a portion of a component of the rolling body guidance device according to the invention. Figure 8A illustrates a perspective view of a component of the rolling body guidance device before the diffusion hardening treatment of the process according to the invention. Figure 8B illustrates a perspective view of part of the rolling body guide device component after diffusion hardening treatment of the process according to the invention and after a cutting step. Figure 9A illustrates a cross-sectional view of a rolling body guide device in the form of a rotary bearing, to show an example of radial play. Figure 9B illustrates a cross-sectional view of the rolling body guide device of Figure 9A, in order to show an example of axial play. Figure 10 illustrates a cross-sectional view of a rolling body guide device in the form of a rotary bearing according to the invention, in order to show one embodiment of the axial play adjustment. Example(s) of an embodiment of the invention

[0078] In the following description provided as an example, for simplicity, we will refer to a unidirectional rotary bearing. The invention, however, is not limited to such a unidirectional bearing but also relates to other rolling body guidance devices, for example bidirectional rotary bearings, linear bearings or ball screws.

[0079] In the following description, provided as an example, for simplicity, we will refer to a bearing comprising an outer ring (one-piece), two inner rings fixed together, a cage, and... rolling elements held in the cage and arranged between the outer ring and the two inner rings. It should be understood, however, that the invention is not limited to such an embodiment, but also includes all rolling element guidance devices covered by the claims, including, for example, similar bearings but comprising more than two inner rings; bearings comprising (at least) two outer rings, one (one-piece) inner ring, a cage, and rolling elements held in the cage and arranged between the outer rings and the inner ring; bearings comprising (at least) two outer rings, (at least) two inner rings, a cage, and rolling elements held in the cage and arranged between the outer rings and the inner rings;or bearings comprising a one-piece inner ring, a one-piece outer ring, a cage and rolling elements held in the cage and arranged between the outer ring and the inner ring, cageless bearings, or linear bearings or screw bearings.

[0080] The invention has applications in the field of watchmaking. It also has applications in the medical field, particularly when the rolling body guidance device is used in a medical device implantable in a living body, for example a human body.

[0081] Figure 1 illustrates a perspective view of an example of a clockwork mechanism 101 comprising the bearing 100, here rotating, according to an embodiment of the invention. The clockwork mechanism 101 of Figure 1 comprises a wheel 200, cooperating (directly or indirectly) with an oscillating weight (not shown), and a pinion 400, cooperating (directly or indirectly) with a power source (not shown) of a clockwork movement, for example a mainspring barrel.

[0082] In the illustrated example, wheel 200 and pinion 400 are coaxial, that is, they rotate around the same axis of rotation A.

[0083] When wheel 200 rotates in a first direction of rotation around its center, bearing 100 transmits this rotation to pinion 400. When wheel 200 rotates in a second direction of rotation opposite to the first, bearing 100 does not transmit this rotation to pinion 400.

[0084] Figure 2 illustrates a top view of the clockwork mechanism of Figure 1. Figure 3 illustrates a cross-sectional view along plane BB of the clockwork mechanism of Figure 2.

[0085] The bearing 100 illustrated in Figure 3 comprises a cage 1, an outer ring 6, and two inner rings 2, 4, fixed together, for example, in a removable or non-removable manner. It also comprises rolling elements 5, for example, but not limited to, balls, held in the cage 1 and arranged between the outer ring 6 and the two inner rings 2, 4.

[0086] As can be seen in Figure 4, which illustrates a top view of a portion of the bearing 100 of the clockwork mechanism in Figure 1, the cage 1 comprises three segments 11, having the same shape and being regularly spaced from each other. However, the invention is not limited to a cage 1 comprising several segments 11, as it also applies to a single-piece cage 1. Nor is the invention limited to the number of segments 11 shown in Figure 4, because, in the case where the cage 1 comprises segments 11, a number of segments 11 other than three can be envisaged.

[0087] Each segment 11 in Figure 4 comprises two inclined planes 10, 10'. However, the invention is not limited to segments 11 each comprising two inclined planes 10, 10', as a single inclined plane 10 or 10' per segment / cage is sufficient. Nor is the invention limited to the presence of inclined planes within the cage.

[0088] In the example in Figure 4, the angles a of the inclined planes 10, 10' of each segment 11 are identical to each other and are identical to the same angles of the other segments 11. In a variant, the value of angle a is between 78° and 88°.

[0089] In another variant, one or more segments 11 each comprise inclined planes with a non-linear ramp. In one variant, this non-linear ramp is progressively decreasing so that as the rolling body ascends the inclined plane, the angle between the ramp and the line passing through the centers of the rolling body and the bearing is always the same. This type of ramp improves locking, particularly in small bearings.

[0090] Each segment 11, together with the inner rings 2, 4 and the outer ring 6, defines a space 15 intended to receive a rolling body 5, for example, but not limited to, a ball. In a preferred embodiment, the ball has three or four points of contact with the rings 2, 4, 6.

[0091] In the locking direction of rotation, when ring 6 is driven clockwise in Figure 4, balls 5, 5', and 10' move up the inclined plane 10 and 10' of each segment 11, respectively, until they become wedged between segment 11 and the inner ring 2 on one side and the outer ring 6 on the other. In this case, bearing 100 is in clutch mode, and the rotation of wheel 200, which is fixed to the outer ring 6, is transmitted via inner rings 2 and 4 to pinion 400.

[0092] As illustrated in Figure 5, in the opposite direction of rotation to that of blocking, which is the counterclockwise direction in Figure 4, the balls 5, 5' descend along the inclined plane 10, respectively 10' of each segment 11, until they are blocked by a stopping surface 12, respectively 12' of each segment 11. In this In this case, bearing 100 is in disengagement mode and the rotation of wheel 200 is not transmitted to pinion 400.

[0093] Each segment 11 in Figure 4 has a shape that creates a second space 16: this shape / space helps to hold the segment 11 in place during electrical discharge machining (EDM). However, this shape is not limiting, and its presence is not required. For example, when the segment is cut by stamping, each segment 11 will lack the shape that creates this second space 16.

[0094] Figure 6 schematically illustrates the steps of the manufacturing process according to the invention. This process includes the steps of - implement at least one component of the rolling body guidance system (step 1000), - perform a diffusion hardening treatment of the machined component, so that the component includes a surface layer having a hardness in the range of 900 Hv - 1100 Hv (step 2000).

[0095] According to the invention, a titanium or titanium alloy component of a watchmaking or medical rolling body guidance device is first machined (in its "soft" state, i.e. before hardening), and then it is hardened by diffusion.

[0096] The process therefore consists of implementing, for example machining, at least one component of the rolling body guidance device in a material that does not have the necessary properties for a watch or medical bearing, and then hardening it so that it has these necessary properties.

[0097] The hardness, ranging from 900 Hv to 1100 Hv, makes the rolling body guide device according to the invention suitable for the watchmaking and medical fields. Furthermore, the Young's modulus of the treated component material, as well as the geometric dimensions of the treated part, are not or only minimally affected by the diffusion hardening treatment.

[0098] It is essential to implement, for example by machining, first the component of the watchmaking or medical rolling body guide device (step 1000), and then to harden it (step 2000), because otherwise during its machining the high risk of removing the surface layer (namely the hardened or treated layer) would not allow obtaining a quality bearing, suitable for the watchmaking or medical field.

[0099] Figure 7 illustrates a cross-sectional view of a portion of a component 20 of the rolling body guide device according to the invention. This component 20 can be the outer ring 6, the inner ring 2, 4, a rolling body 5, 5' or possibly a cage.

[0100] Preferably, this component 20 is an inner ring 2, 4, as it is subjected to high stresses in a watch or medical bearing.

[0101] In one variant, the surface layer 21 is defined between an external surface 210 and an internal surface 212, the internal surface 212 being adjacent to a base layer 22 (i.e., an untreated layer) of the component. The proportions of layers 21 and 22 in Figure 7 do not necessarily correspond to the actual proportions.

[0102] In one variant, the process includes the step of: - carry out a hardening treatment by (purely or predominantly) interstitial diffusion, so that the hardness of the surface layer 21 decreases from the external surface 210 to the internal surface 212. In this variant, the progressive decrease in hardness improves the transfer of the load between the surface layer and the base layer.

[0103] In another, less preferred variant, diffusion is (purely or predominantly) substitutional.

[0104] In one variant, the surface layer has a thickness e, visible in figure 7, within the range 5.m - 50 |im. This thickness e also allows sufficient load transfer for the watchmaking and / or medical field.

[0105] According to the invention, the diffusion hardening treatment includes the step of immersing the part in a gas, for example a gas comprising at least one atom selected from carbon, nitrogen, argon or oxygen.

[0106] According to the invention, the process includes the step of selecting a temperature to perform the hardening, for example a temperature substantially higher than the ambient temperature, for example a temperature in the range of 500 °C - 800 °C.

[0107] In one variant, the process includes the step of temperature control during hardening, in order to allow diffusion while avoiding the growth of unwanted phases or compounds, such as carbides, nitrides or oxides.

[0108] According to the invention, the process includes the step of selecting a pressure to perform the hardening, for example a pressure greater than atmospheric pressure (for example it can reach several times atmospheric pressure).

[0109] According to the invention, the hardening treatment time is within the range of 1 h - 24h.

[0110] The holding time in a treatment chamber, under target pressure and temperature, defines the depth of the surface layer 21, for a given material.

[0111] In an unclaimed variant, the diffusion-hardened bearing component is made of stainless steel.

[0112] Figure 8A illustrates a perspective view of a component 20 of the rolling body guide device before the diffusion hardening treatment of the process according to the invention.

[0113] The hardening treatment according to the invention deforms the treated component 20. In particular, the hardening treatment can modify the shape, at least one dimension, and / or the mass of the treated component. In one embodiment, the hardening treatment modifies at least one dimension by up to 1% of its length. It is therefore desirable to treat a component 20 having at least one dimension and / or a mass greater than that of the desired final component, for example, at least twice as large, in order to limit its deformation during the treatment, and to cut it after the treatment to obtain the component having the desired shape, dimensions, and / or mass.For example, if we want to obtain a flat and thin treated component (namely, having at least one dimension less than one tenth of its other dimensions), in one embodiment, we will treat with the hardening treatment an initial thick component (namely, not thin), which we will then cut to obtain the desired thin component, so that the cutting surface is flat: the cutting surface not having been treated, it will not have any change in shape due to the treatment and will have the desired flatness.

[0114] In one variant, the treated component has at least one larger dimension and / or mass compared to that of the desired final component, and the process includes, after the hardening treatment step, the following step: - cut out the treated component, in order to limit deformations due to the hardening treatment.

[0115] Figure 8A illustrates a possible cutting line D of component 20, after processing.

[0116] Figure 8B illustrates a perspective view of part of the (final) component 20' of the rolling body guide device after the diffusion hardening treatment of the process according to the invention and after cutting along the cutting line D of Figure 8B.

[0117] The component 20' includes (at least) one untreated surface (the lower surface 23 in Figure 8B), but the cutting line D is chosen so that this untreated surface is non-functional in the guiding device.

[0118] Figure 9A illustrates a cross-sectional view of a rolling body guide device 100 in the form of a rotary bearing, to show an example of radial play JR, following the application of a radial force FR.

[0119] Figure 9B illustrates a cross-sectional view of the rolling body guide device 100 of Figure 9A, to show an example of axial play JA, following the submission of an axial force FA.

[0120] In a rotary bearing, the clearance depends on the dimensions of the parts. The axial clearance JA of the bearing is very important because it defines the contact angle of the rolling elements 5 with the ring(s).

[0121] This means that a rotary bearing (for example, a deep groove bearing) must be ground after the hardening treatment. Grinding a component treated with the hardening treatment according to the invention is not possible because the layer thickness is too thin. Grinding would remove at least part, if not all, of the treated layer. In one embodiment, the guiding device is a rotary bearing, and the process includes, after the hardening treatment step, the following step: - Adjustment of axial play in the rotary bearing during assembly of the guide device.

[0122] This prevents the treated layer from being removed when adjusting axial play.

[0123] In one embodiment, the guiding device comprises a first inner ring 4 (cone) and a second inner ring 2 (core), the axial play adjustment being achieved by driving the first inner ring (cone) 4 onto the second inner ring (core) 4.

[0124] Figure 10 illustrates a cross-sectional view of a rolling body guide device 100 in the form of a rotary bearing according to the invention, in order to show an embodiment of the adjustment of the axial play RJA, by pressing the first inner ring (cone) 4 onto the second inner ring (core) 4. Reference numbers and symbols used in the figures 1 Cage 2 First inner ring 4 Second inner ring 5 Rolling body 6 Outer ring 10, 10' Inclined plane 11 Cage segment 12, 12' Stopping surface 15, 15' First space 16 Second space 20, 20' Component 21 Surface layer 22 Base layer 23 Untreated surface 100 Bearing 101 Clockwork Mechanism 200 Wheel 210 External surface 212 Internal surface 400 Pinion 1000 Machining step 2000 Diffusion hardening treatment stage Axis of rotation D Cutting line e Surface layer thickness FA Axial force FR Radial force JA Axial Game JR Radial Game RJA Axial Play Adjustment

Claims

Demands 1. A method for manufacturing a rolling body guide device (100) for a medical mechanism, comprising components, these components comprising: - a first element (6), - a second element (2, 4), - rolling bodies (5, 5') arranged between the first element (6) and the second element (2, 4), to facilitate the relative movement of the first element (6) with respect to the second element (2, 4), at least one component (20; 6, 2, 4, 5, 5') being made of titanium or titanium alloy, the process comprising the steps of - implement the titanium or titanium alloy component; - to perform a diffusion hardening treatment on the machined component, the diffusion hardening treatment comprising a step of immersing the titanium or titanium alloy component (20; 6, 2, 4, 5, 5') in a gas, the gas comprising at least one atom selected from carbon, nitrogen, argon or oxygen, the process comprising the steps of: - selection of a temperature within the range of 500 °C - 800 °C, - selection of a pressure higher than atmospheric pressure, in which the hardening treatment time is within the range of 1 h - 24h, so that the component comprises a surface layer (21) having a hardness within the range of 900 Hv - 1100 Hv.

2. The method according to claim 1, the surface layer (21) being defined between an external surface (210) and an internal surface (212), the internal surface being adjacent to a base layer (22) of the component, the method comprising the step of: - perform an interstitial diffusion hardening treatment, in so that the hardness of the surface layer (21) decreases from the external surface (210) to the internal surface (212).

3. Method according to any one of claims 1 or 2, the surface layer (21) having a thickness (e) within the range 5.m - 50.m.

4. A process according to any one of claims 1 to 3, the treated component having at least one larger dimension and / or mass compared to that of the desired final component, the process comprising, after the hardening treatment step, the following step: - cut out the treated component, in order to limit deformations due to the hardening treatment.

5. A method according to any one of claims 1 to 4, the guiding device being a rotary bearing, the method comprising, after the hardening treatment step, the step of: - Adjustment of axial play in the guide device during assembly of the guide device.

6. Method according to claim 5, the rotary bearing comprising a first inner ring and a second inner ring, the axial clearance adjustment being achieved by driving the first inner ring onto the second inner ring.

7. Rolling body guide device (100) for a medical mechanism, manufactured using the method according to any one of claims 1 to 6, the device comprising at least the following components: - a first element (6), - a second element (2, 4), - rolling bodies (5, 5') arranged between the first element (6) and the second element (2, 4), to facilitate the relative movement of the first element (6) with respect to the second element (2, 4), in which at least one component (20; 6, 2, 4, 5, 5') is made of titanium and / or titanium alloy and includes a surface layer (21) of treated titanium and / or treated titanium alloy, said surface layer (21) having a hardness in the range of 900 Hv - 1100 Hv.

8. Device according to claim 7, the surface layer (21) being defined between an external surface (210) and an internal surface (212), the internal surface being adjacent to a base layer (22) of the component, the hardness of the surface layer (21) decreasing from the external surface to the internal surface.

9. Device according to any one of claims 7 or 8, the surface layer (21) having a thickness (e) within the range 5.m - 50.m.

10. Device according to any one of claims 7 to 9, the components include a cage arranged to hold the rolling bodies.

11. Device according to any one of claims 7 to 10, being a rotary bearing, a linear bearing or a screw-with-rods.

12. Implantable medical device, comprising the rolling body guide device (100) according to any one of claims 7 to 11.

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