Assembly devices, methods, bracelets and watches

Abstract

The present invention relates to an assembly device, a method for obtaining an assembly device, a bracelet, and a wristwatch. An assembly device (10) for pivotably mounting at least two parts of a wristwatch comprises a first part (1) and a pin (P) having means (7) for mechanically connecting to a second part (2). The first part (1) has a first friction surface (4), and the pin (P) has a second friction surface (5). The first friction surface (4) and the second friction surface (5) come into contact with each other during pivoting motion. One of the friction surfaces (4, 5) has a surface hardness higher than that of silica and / or feldspar. The other of the friction surfaces (4, 5) has a surface hardness lower than that of silica and / or feldspar. In this way, the effects of wear and elongation can be significantly reduced.

Description

[Technical Field]

[0001] [Special statement] The present invention relates to an assembly device, a method for obtaining an assembly device, a bracelet, and a wristwatch.

[0002] Watch bracelets (wristbands), especially those made of metal, are equipped with articulated bracelet links. Two adjacent bracelet links are pivotally (rotatably) attached to each other by bracelet pins, resulting in the formation of multiple articulated joints (connections).

[0003] When worn, the joints will wear down over time, causing the bracelet to stretch. This stretching may include an increase in length and / or a loss of tension ("slack"). These deteriorations can make the bracelet uncomfortable to wear and significantly alter its appearance.

[0004] Deterioration of bracelet joints can be caused by numerous factors, one of which is abrasive dust particles. These particles get into the joints during daily use of bracelet watches. These particles are naturally occurring in the environment and originate from natural processes such as rock erosion, as well as human activities such as mining and construction. Many abrasive particles are composed of silica and / or feldspar, which are the most abundant minerals in the Earth's crust.

[0005] It is well known in the prior art that bracelet links made of hard materials or surface-hardened metals reduce the deterioration of their appearance over time by increasing the scratch resistance of the component. There is little information available on the normal wear of bracelet joints and their impact on the wearer's comfort and aesthetics.

[0006] European Patent Application Publication No. 2 057 914 A1 proposes special materials whose suitability for mutual friction is confirmed. Wear is minimized by placing a high-hardness bearing between the hinge pin and the groove of the link. European Patent Application Publication No. 0 243 315 A1 proposes placing an intermediary component in the form of a bearing made of ruby ​​or a similar material between the hinge pin and the link to reduce wear at the joint of the strap. This solution requires an additional element for fixing the bearing, as well as an additional step for assembling the link. Japanese Patent Publication No. 2003-038218A describes a stainless steel hinge pin for a watch band, the surface of which is hardened by the diffusion of nonmetallic chemical elements such as carbon and / or nitrogen. An additional layer of nitrides, carbides, or oxides of group 4, 5, and 6 elements may be deposited on the upper surface. European Patent Application Publication No. 1 136 012 A1 describes the construction of a metal watch strap with articulated links designed to reduce normal wear of the links by avoiding metal-to-metal friction between the hinge pin and the links. To this end, a plastic insert is introduced into the central link to reduce friction and metal-to-metal contact. Utility Model Registration No. 3 058 276 U describes an optimized hinge pin shape for driving into the links of a hinged link strap to increase retention force (tear force) by optimizing the external shape of the hinge pin end. U.S. Patent No. 3 837 163 A describes a hinged link watch band made of composite materials, comprising a metal matrix with carbide, nitride or hard oxide particles made by powder metallurgy. The aim is to create a visible mirror-finished metallic, glossy, scratch-resistant and corrosion-resistant outer surface. European Patent No. 2 440 085 B1 describes a method for constructing a strap connection of an articulated link to avoid fracture of hard and brittle materials such as ceramics or sintered hard metals. The solution is an optimized hinge pin that avoids pin-link contact in the area of ​​highest stress.

[0007] The object of the present invention is to provide, in particular, an assembly device for watch components in which the effects of wear and / or elongation are reduced without the addition of additional elements, a method for obtaining the further-advanced assembly device, and a further-advanced bracelet and watch.

[0008] An assembly device for pivotably mounting at least two components of a wristwatch plays a role in solving the problem. The assembly device comprises a first component and at least one pin having means for mechanically connecting to a second component. The first component has a first friction surface, and the pin has a second friction surface. The first and second friction surfaces come into contact with each other during pivoting motion. According to the present invention, one of the friction surfaces has a surface hardness higher than that of silica and / or feldspar. The other friction surface has a surface hardness lower than that of silica and / or feldspar.

[0009] In other words, one of the friction surfaces is "harder" compared to typical abrasive contaminants found on watch components, while the other friction surface is "softer" compared to these particles. Experiments have shown that this configuration surprisingly significantly reduces wear on assembly devices, such as at bracelet joints. As a result, stretching and tearing of watch bracelets are reduced.

[0010] It is generally known that hardened or at least surface-hardened materials are inherently more resistant to wear. Surprisingly, the inventors have found that hardening only one component in tribological pair formation—for example, only one of the pins or links—is sufficient to dramatically reduce wear on both components of the bracelet joint. For example, the use of hardened pins can reduce link wear even if the links are not hardened. This wear reduction effect may be achieved by the fact that fine particles of silica and feldspar, which exist naturally as dust, are embedded in the softer side of the tribological pair.

[0011] In addition, the configuration of the present invention makes it possible to construct thinner bracelets. No additional elements such as spacers or sleeves are required on the shafts or pins of the joints, and at the same time, the components are kept to a sufficient thickness for good mechanical resistance. The fact that no additional elements are required further makes assembly easier and faster. Another advantage is that components with lower hardness are relatively easy to manufacture, machine, and assemble. "Component" can refer to one of two parts of a pivotal assembly that pivots relative to each other. For example, a first part or link and a pin are components.

[0012] For example, the first friction surface has a surface hardness higher than that of silica and / or feldspar, and the second friction surface has a surface hardness lower than that of silica and / or feldspar. Alternatively, the second friction surface has a surface hardness higher than that of silica and / or feldspar, and the first friction surface has a surface hardness lower than that of silica and / or feldspar. The hardness of silica and / or feldspar is typically higher than 500HV0.025, e.g., higher than 600HV0.025, and / or less than 800HV0.025, or e.g., less than 700HV0.025. The hardness of silica and / or feldspar is typically higher than Mohs hardness 5.5 and / or lower than Mohs hardness 6.5. In particular, the hardness of silica and / or feldspar is higher than Knoop hardness 500 and / or lower than Knoop hardness 800. The relationship between the surface hardness of the pin and the first component or link described in the claims must be satisfied using at least one of the hardness measurement methods described above. In particular, this relationship should be satisfied regardless of the measurement method used.

[0013] The surface hardness of each friction surface is defined relative to the hardness of silica and / or feldspar. The material hardness (e.g., bulk hardness or core hardness) of each component in the region below the first and / or second friction surface may be the same as the surface hardness, or it may be different from the surface hardness, for example, lower than the surface hardness. For example, the first and / or second friction surface may be subjected to surface hardening treatment. In this case, only a specified thickness of hardening treatment is performed so that the surface hardness of each is typically higher than the material hardness below the surface. In principle, since only the surfaces are in contact with each other, the hardness below the surface is irrelevant to the present invention. However, in order to achieve the desired durability, the hardened region should not be too thin so that the effect of the present invention is not affected by minute surface damage such as scratches.

[0014] A pin (also called a hinge pin or shaft) is a long, elongated member that serves to connect two parts. In particular, the longitudinal or central axis of the pin acts as the pivot axis for the pivotal motion of the two parts. Specifically, pins are solid and / or one-piece members. For example, a pin may be implemented as a screw or a bolt.

[0015] In particular, the assembly device is specialized for watch bracelets. Specifically, the first component is one of the two components of the watch. Specifically, the second component is the other of the two components of the watch. For example, each of the first and second components can be one of the bracelet links, the watch case, and the clasp.

[0016] The assembly device serves to pivotably mount at least two components of the watch. Thus, the device serves to connect the two components so that they can rotate relative to each other.

[0017] The pin is suitable for mechanical connection to a second part. For example, the pin has a contour or shape that conforms to or corresponds to the contour or shape of the second part, particularly the contour or shape of an opening in the second part, as a means for mechanical connection. Thus, the pin can be inserted into the opening for mechanical connection. In particular, the mechanical connection is a shape fit and / or pressure fit connection in which at least one degree of freedom is restricted.

[0018] The first and second friction surfaces are configured to contact and / or guide each other during rotational relative motion. These surfaces generate friction by rubbing against each other. Each friction surface plays a role in guiding the other friction surface to pivot. In this way, each part contributes to holding, or at least holding, the other part during pivotal motion. For example, radial holding or guiding may be intended. Thus, one part holds the other part such that relative radial movement of the two parts is prevented while relative rotation is possible.

[0019] The first friction surface and the second friction surface are in contact with each other at least at a point, along a line, or across a surface. When the two parts pivot relative to each other, the first and second friction surfaces slide against each other and rub against each other at least at a point, along a line, or across a surface.

[0020] In one configuration, the assembly device comprises two pins configured to be coaxially positioned at different locations along the longitudinal direction on the same axis. In other words, the pins are divided into two distinct pins having the same axis of rotation. Thus, the first and second components are connected by two coaxially positioned pins.

[0021] In one embodiment, the pin has means for being fixed to the inside of a second component, particularly an opening in the second component. In particular, the means for being mechanically connected to the second component is configured as means for being fixed to the inside of a second component, particularly an opening in the second component. For example, the means may have a cylindrical or corrugated shape for interference fit. In particular, the pin has a portion with a non-cylindrical cross-section. This makes it easy to prevent the pin from rotating relative to the second component about its central axis. The opening in the second component may be cylindrical or non-cylindrical.

[0022] In other words, the pin is configured to be immovably fixed to the second part. In particular, the pin is configured to be inserted into an opening in the second part, such as a through hole or a blind hole, and to be fixed in this position. The pin can be fixed by interference fit with the opening in the second part. Thus, the pin can have an outer dimension, such as an outer diameter or outer width, that is slightly larger than the corresponding inner dimension of the opening, for example, several micrometers larger. As a result, lateral elastic stress is generated in both the end hole and the pin when it is driven in. Thus, the strength of the assembly is increased by these lateral stresses. The pin can have a non-circular cross-section at least one or both ends. For example, the pin can have a knurled, hexagonal, or triangular outer shape.

[0023] In one configuration, the pin is driven into the opening. A press is typically used to insert or drive the pin into the opening. As another example, the pin may be threaded into the opening.

[0024] When press fitting is established, an important parameter is the interference amount, which is defined as the surface adhesion between the pin and the opening. The interference amount is approximately determined by the depth of insertion during assembly and the difference between the diameter of the opening (hole) and the diameter of the pin. The greater the difference, the greater the holding force will be at the same insertion depth. However, there are two limits: (1) when exceeding a certain stress, the elastic limit will be reached and the material will yield, and (2) there is a possibility that the material of the pin will peel while entering the opening. To avoid this last phenomenon, the pin material can have a higher hardness than the material forming the opening.

[0025] The selection of materials for the production of the pin and the opening, as well as the mechanical properties associated with the materials, are often determined by the type of construction and / or the need for mechanical stability of the pin during driving. The mechanical strength of the pin must be sufficient to prevent the pin from deforming under the insertion force. This embodiment serves to ensure a defined friction surface pair. In this way, wear is reduced in an improved manner.

[0026] For press fit assemblies, using pins with non-circular outer shapes at both ends, especially pins with knurls, has industrial advantages compared to smooth pins. Specifically, it is possible to more appropriately manage the dimensional tolerances of the components, and as a result, more appropriately manage the interference amount.

[0027] As another example, it is not excluded that the pin can be movably connected to the second part, for example pivotally connected. For example, the pin may be movably connected to the opening of the second part. In one configuration, the pin can rotate with respect to the first and second parts.

[0028] In one embodiment, the first component comprises an opening with an inner circumferential surface that provides a first friction surface. In one embodiment, the pin comprises an outer circumferential surface that provides a second friction surface.

[0029] The first component may have an opening into which a pin can be positioned. The opening may have at least a partially circular cross-section. In particular, the opening has a circular cross-section. The pin may have at least a partially circular cross-section. In particular, the pin has a circular cross-section. At least a portion of the outer circumferential surface of the pin can serve as a second friction surface. At least a portion of the inner circumferential surface of the opening of the first component can serve as a first friction surface. Thus, the first component and the pin can cooperate to form a hinge.

[0030] In particular, the second friction surface is provided on the contact portion of the pin. The contact portion may be the shaft portion of the pin. Thus, the shaft portion of the pin is configured to contact the first friction surface. In particular, in this configuration, the openings of the first component and the second component are aligned in a straight line to form a passage for receiving the pin.

[0031] In certain embodiments, the pin comprises a screw head at a first end and a threaded portion at a second end. In particular, the threaded end serves as a means for a firm mechanical connection to a second part.

[0032] The second end portion is opposite to the first end portion. In particular, each end portion is an axial end portion. In this embodiment, the pin is configured as a screw that can be screwed into the second part. In particular, the pin further comprises a central portion configured to be axially positioned between the two end portions.

[0033] In one embodiment, the pin comprises a central portion, a first end portion, and a second end portion. The first and second end portions are designed to be mechanically connected to, in particular, fixed to, a second component.

[0034] The end portion and the central portion are different parts along the axial direction of the pin. In this embodiment, the pin is connected to the second component on both sides. Thus, this mechanical connection is particularly stable and permanent. The bending load on the pin is minimized. Thus, wear is reduced in an improved manner. In a further embodiment, the first component is configured as a sleeve positioned and arranged around at least a portion of the pin.

[0035] In this embodiment, pivoting motion occurs between the pin and the sleeve. In particular, the sleeve is fixed to a second component, for example, by press fitting. The second component may form a link of a bracelet. The first component can be configured to be invisible or barely visible in the finished bracelet. The sleeve can be fixed so as not to move axially on the pin. Therefore, the sleeve cannot be removed from the pin. In this embodiment, the surface areas of the first and second friction surfaces are maximized. As a result, the frictional force is minimized, and wear is reduced in an improved manner.

[0036] In particular, the opening of the sleeve has a circular cross-section. Thus, the sleeve surrounds the pin. Specifically, the inner diameter of the sleeve is slightly larger than or approximately the same as the outer diameter of the pin. Thus, the surface area of ​​the friction surface is further increased while simultaneously ensuring good pivotal movement. The outer shape of the sleeve can be selected depending on the second component or its opening, and whether it is mechanically connected to or fixed to the second component. In one configuration, the sleeve has an annular cross-section.

[0037] In one embodiment, the first component is a bracelet link, and / or the second component is a bracelet link. A bracelet link is one of several components that make up a bracelet. In one embodiment, the assembly device serves to pivotally mount two bracelet links to each other.

[0038] The first and second parts may be similar or identical. The first and second parts may be individual links of the bracelet, particularly adjacent links. Alternatively, the first and second parts may be of different designs. For example, different parts may be used alternately to form the bracelet. One of the first and second parts may be a bracelet link, and the other of the first and second parts may be a connecting element that is at least partially visible or not visible in the worn bracelet.

[0039] In one configuration, the pins are supplied separately from each component. As a result, for example, two components are attached to each other by the pins. In another configuration, the pins are part of a second component. As a result, the second component is attached to the first component using the pins of the second component. The pins can be attached to the remainder of the second component by shape fit (positive) connection, pressure fit (friction / non-positive) connection, and / or by integral bonding such as laser welding. The pins may also be manufactured integrally with the remainder of the second component.

[0040] In one embodiment, the first or second component is a watch case. A watch case is a container that houses the movement of a watch. The watch case protects the movement of the watch from dust, moisture, and shock. In one embodiment, the assembly device serves to pivotally attach the bracelet links to the watch case. For example, one of the first and second components may be the bracelet links, and the other of the first and second components may be the watch case. In this case, the assembly device forms a joint between the watch case and the bracelet.

[0041] In one embodiment, the first or second component is a bracelet clasp. The bracelet clasp serves to open and close (fasten) the bracelet. In one embodiment, the assembly device serves to pivotally attach the bracelet links to the clasp. For example, one of the first and second components may be a bracelet link, and the other of the first and second components may be a clasp. In this case, the assembly device forms a joint between the clasp and the bracelet. In one embodiment, the assembly device further comprises a second component.

[0042] In one embodiment, one of the friction surfaces having a surface hardness higher than that of silica and / or feldspar has a surface hardness of at least 800 HV 0.025, preferably at least 900 HV 0.025, and more preferably at least 1000 HV 0.025. Thus, the hard part of the joint has a surface hardness higher than that of the silica and feldspar particles. In this way, the abrasive particles are deposited on the soft part to form a protective layer, thereby limiting its wear. Since the surface of the hard part is harder than the abrasive particles, it wears no or very little.

[0043] In particular, one of the friction surfaces having a surface hardness higher than silica and / or feldspar has a maximum surface hardness of 3100 HV 0.025, and especially a maximum of 1,500 HV 0.025. All hardness values ​​refer to HV 0.025 unless otherwise specified.

[0044] In one embodiment, the other friction surface having a lower surface hardness than silica and / or feldspar has a surface hardness of at most 500 HV 0.025, preferably at most 350 HV 0.025, more preferably at most 320 HV 0.025 or 300 HV 0.025, and / or at least 120 HV 0.025, preferably at least 250 HV 0.025. In this way, it is possible to embed abrasive fine particles of silica and feldspar having hardness in the range of 500 to 800 HV 0.025.

[0045] Particulate matter is understood to be particles with a small diameter of approximately 0.1 to 100 μm. Analysis of contaminants extracted from several bracelet watches worn for extended periods showed that the particles were typically d 50 This indicates a particle size of 30 ± 10 μm. The particle size is measured by laser diffraction in accordance with ISO 13320:2020. The particles observed by SEM have a somewhat angular shape.

[0046] In one embodiment, the second friction surface of the pin has a surface hardness higher than that of silica and / or feldspar. The higher the surface hardness of the pin, the better the mechanical properties of the pin relative to the first and / or second parts of the assembly device. The pin, being the component subjected to the highest load, is thus made of the harder of the two materials. In this case, assembly by press fitting is simpler. Furthermore, the manufacture of the pin is often simpler compared to the first and / or second parts, which have more complex shapes. As an alternative example, the first friction surface of the first component has a surface hardness higher than that of silica and / or feldspar.

[0047] According to the present invention, the combination of materials forming the assembly is selected, as described above, primarily considering the surface hardness of the materials compared to the hardness of silica and feldspar. Among the materials that satisfy the above hardness characteristics, those skilled in the art will be able to freely select the properties of the materials (e.g., metals and / or composites) according to well known manufacturing and / or functional criteria (e.g., molding, machining, toughness, strength, assembly method, etc.). In one configuration, the material forming the first friction surface and / or the material forming the second friction surface are hardened surfaces.

[0048] In one embodiment, the material forming one of the friction surfaces having a hardness higher than that of silica and / or feldspar (the material whose surface hardness is higher than that of silica or feldspar) is a surface-hardened metal or alloy, preferably surface-hardened titanium or titanium alloy, or a surface-hardened steel, preferably surface-hardened austenitic steel. The material whose surface hardness is higher than that of silica or feldspar may be a metal or alloy. This material may be whole-hardened or surface-hardened. Preferred surface hardening methods are thermal diffusion, ion implantation, and oxidative heat treatment. Preferably, a material with a surface hardness of 800 to 1500 HV 0.025 is selected. Examples of such materials are metallic glass (nickel-based, iron-based, cobalt-based, or niobium-based), surface-hardened titanium alloy, high-entropy alloy, metal matrix composite (MMC), surface-hardened stainless steel, surface-hardened nickel-free stainless steel, and surface-hardened Group IV alloy.

[0049] Materials with a surface hardness higher than silica or feldspar are at least one material selected from the group consisting of stabilized ceramics; metallic glass; high-entropy alloys; metal matrix composites; surface-hardened stainless steel; surface-hardened titanium and titanium alloys; and surface-hardened Group 4 alloys, or may include such materials. Preferably, the material is nickel-based, iron-based, cobalt-based and niobium-based metallic glass; surface-hardened high-nitrogen austenitic stainless steel of types P558, P2000 and Biodur® (a substantially nickel- and cobalt-free high-strength stainless steel produced by the electroslag remelting method, which is non-magnetic and substantially free of ferrite phases, and consists of the following components: C (max): 0.08%, P (max): 0.03%, Si (max): 0.75%, Ni (nominal): 0.1%, Mn (max): 21% The following can be selected: 0.00–24.00%, S (maximum) 0.01%, Cr (nominal) 19.00–23.00%, Co (nominal) 0.1%, Mo (nominal) 0.50–1.50%, Cu (nominal) 0.25%, N (nominal) 0.9%, and the remainder Fe (nominal); surface-hardened type 316L and 904L austenitic steel; surface-hardened grade 2 titanium alloy, grade 5 titanium alloy, near-β titanium alloy, β titanium alloy; surface-hardened binary and ternary alloys of group 4 metals. More preferably, the material can be selected from the group consisting of surface-hardened austenitic stainless steels of types 316L and 904L; surface-hardened Grade 2 and Grade 5 titanium alloys by thermal diffusion of oxygen or by thermal nitriding and nitrogen diffusion; and surface-hardened binary and ternary alloys of Ti, Zr, and Hf by thermal oxidation. A suitable surface hardening method for titanium and titanium alloys by thermal nitriding and nitrogen diffusion is disclosed in International Publication No. 2017 202 728 A1. A suitable surface hardening method for titanium and titanium alloys by thermal diffusion of oxygen is disclosed in International Publication No. 2017 207 794 A1. A suitable surface hardening method for iron alloys by thermal diffusion of carbon and / or nitrogen is disclosed in International Publication No. 2011 009 463 A1.A suitable ternary alloy and a method for treating its thermochemical surface hardening are disclosed in the concurrently pending European Patent Application No. 23171553.3.

[0050] Since the important parameter is surface hardness, hardening only the surface is sufficient, rather than the entire component. Therefore, hardening the entire component (whole hardening treatment) is not essential. This saves energy and costs.

[0051] In addition, hardening or surface hardening treatments make it possible to use the same material for two components of an assembly, such as pins and links, or the same type of material suitable for overall and / or surface hardening, of a similar color. In this way, the electrochemical potential between the joining elements is kept low, thus reducing electrochemical corrosion in contaminated environments. Another advantage is that the aesthetic appearance of the outer surface of the bracelet is preserved when the pins are visible. Furthermore, while pins that are whole or surface hardened can be attached to links made of unhardened material by driving the pins into them, this is difficult, if not impossible, if the pins are in the same metallurgical state as the links. In addition, hardening or surface hardening treatments make it possible to manufacture bracelets with drive-in pins where all parts are made of titanium or titanium alloy, taking advantage of the low density and hypoallergenic properties of this material.

[0052] In one configuration, the pin is hardened by a surface hardening treatment, particularly by at least one thermochemical treatment. For example, nitriding, carburizing, and / or carbonitriding can be used for stainless steel, and / or diffusion of at least one element selected from oxygen, nitrogen, and carbon can be used for titanium alloys. The surface hardening treatment of the pin reduces wear on the pin and the openings or holes of the first and / or second parts, and allows the knurled pin to be driven into parts with a hardness similar to that of the pin's core.

[0053] In particular, thermochemical treatment can be carried out in accordance with the method disclosed in International Publication No. 2011 / 009463 A1 for steel or iron, and the contents of this patent document are incorporated into this application by reference. The method comprises activating a passive iron or non-ferrous metal article, which includes the steps of heating the article to a first temperature, heating at least one compound containing nitrogen and carbon (hereinafter referred to as an N / C-compound) to a second temperature to provide one or more gas species, and contacting the article with the gas species, wherein the N / C-compound contains at least four atoms. Preferably, the method is used to activate the article prior to subsequent carburizing, nitriding, or carbonitriding. Generally, the N / C-compound used in the activation method can be selected from compounds having carbon-nitrogen single, double, or triple bonds. Preferably, the N / C-compound is liquid or solid at ambient temperature (25°C) and atmospheric pressure (1 bar). This facilitates the handling of the N / C compound and the introduction of the compound into the heating device used in the method. The gas species generated from the N / C compound during heating may be decomposition products of the compound or the N / C compound itself in gaseous form. The gas species is usually transported to the article by diffusion and / or convection gas transport and brought into contact with the article. Preferably, the first and second temperatures are less than 500°C. This prevents the formation of nitrides or carbides. This is particularly important for stainless steels and similar alloys where corrosion resistance may be lost if nitrides or carbides are formed. The first and second temperatures may be the same. For example, an article of austenitic stainless steel AISI 316 can be carbonitrided by flowing argon gas over initially solid urea in a tubular furnace while heating from room temperature to 440°C for no more than 45 minutes. The initially solid urea is placed at the inlet of the tubular furnace. Once the temperature reaches 440°C, the material is cooled to room temperature in argon gas (Ar) within 10 minutes. The total thickness of the hardened zone (region) is approximately 10 μm.As another example, austenitic stainless steel AISI 316 articles can also be carburized and nitrided by flowing hydrogen gas over initially solid urea in a tubular furnace while heating from room temperature to 490°C in 45 minutes or less. The initially solid urea is placed at the inlet of the tubular furnace. Once 490°C is reached, the article is cooled to room temperature in argon gas (Ar) in 10 minutes or less. The total thickness of the hardened zone is approximately 22 μm. The surface microhardness is higher than 1500 HV (measured with a 25 g load). The hardness of the untreated stainless steel was 200-300 HV.

[0054] For surface hardening treatment of titanium, for example, the method disclosed in International Publication No. 2017 / 207794 A1 can be used. The contents of this document are incorporated into this application by reference. This method consists of the following steps:

[0055] — Steps of providing components of a titanium alloy, — The component is made at least 10 -5 A step of placing a bar in a reactive atmosphere containing a gas species that provides carbon at partial pressure, wherein the gas species that provides carbon contains carbon and oxygen, and the reactive atmosphere does not contain any chemical species that contain hydrogen. — The step of heating the components in an inert atmosphere or a reactive atmosphere to a melting temperature TD of at least 800°C, — Contains solid solution carbon and oxygen and has a composition of TiO X C 1-X The steps include: providing the constituent elements with a diffusion zone having a unique phase of the carbo-oxide compound (x is a number in the range of 0.01 to 0.99), maintaining the constituent elements in a reactive atmosphere in TD for a reaction time of at least 30 minutes; — A step of cooling the components from TD to ambient temperature and Includes.

[0056] The component is made of a titanium alloy, and any titanium alloy containing pure titanium can be used. The component may be made of a Group 4 metal, and any Group 4 metal is suitable for the method. The Group 4 metal can be selected from the list of titanium, titanium alloys, zirconium, and zirconium alloys. The component may consist of a titanium alloy or a Group 4 metal, or may contain other materials. For example, the component may have a core of another material, polymer, glass, ceramic, or another metal, and an outer layer of a titanium alloy.

[0057] For example, a sample of Grade 5 titanium is processed in a furnace. The furnace is emptied and backfilled twice with argon gas, and a continuous gas flow consisting of 20 ml / min of Ar and 30 ml / min of CO (60% CO) is supplied. The sample is heated to 1000 °C at a rate of 20 °C / min in this same gas mixture and held at this temperature for 20 hours once this temperature is reached. Cooling is carried out at 50 °C / min in the process gas flow. As a result, titanium carbo-oxidation occurs. A mixed-type intrusive compound TiO x C 1-x as well as a mixed-type intrusive solid solution (the "diffusion zone") based on carbon and oxygen is formed. The hardness of TiO x C 1-x is 1416 HV0.025. The case hardening depth is approximately 80 μm. The core has transformed into an α / β structure, that is, simultaneous hardening of the core and the surface has occurred.

[0058] As another example, a sample of Grade 2 titanium is processed in a furnace. The furnace is emptied and backfilled twice with argon gas, and a continuous gas flow consisting of 10 ml / min of Ar, 30 ml / min of CO2, and 20 ml / min of CO is supplied (p CO = 0.33 atm and p CO2(0.50 atm). The sample is heated in this same gas mixture at a rate of 20°C / min to 1000°C, and once this temperature is reached, it is held at that temperature for 20 hours. Cooling is performed in the process gas stream at 50°C / min. Oxidation of titanium occurs due to the supplied gas. A layer of titanium oxide is formed with a thickness of approximately 25 μm, and a diffusion layer of oxygen in solid solution is formed in titanium (below the oxide layer), with a thickness of approximately 100 μm. For the nitriding treatment of titanium, the method described in International Publication No. 2017 / 202728 A1 (incorporated in this application by reference) can be used. This method is

[0059] a) A step of heating the workpiece to the initial nitriding treatment temperature; b) The step of subjecting the workpiece to hot isostatic pressing (HIP) conditions, under high pressure in a nitrogen-containing gas, to a nitriding temperature of 1 or more for a predetermined time, in order to convert the titanium metal surface layer into a first layer portion made of ceramic titanium nitride and a second layer portion having a nitrogen gradient in the titanium metal, and c) In order to further strengthen the titanium metal below the first ceramic nitride layer formed in step b), the workpiece is quenched in a nitrogen-containing gas under high pressure under hot isostatic pressing (HIP) conditions as the first step of hardening heat treatment. Includes.

[0060] A workpiece containing commercial pure titanium (grade 2) in the form of a thin-walled tube (t=1.0 mm) is placed in a hot isostatic pressurizer. Nitrogen gas N2 is supplied to the chamber of the pressurizer. During step a), the gas temperature is raised until the workpiece temperature reaches 960°C. Simultaneously, the gas pressure is increased to 170 MPa. In step b), the same temperature and gas pressure are maintained for 2 hours. Since this temperature has already exceeded the "β transformation point" temperature, the temperature increase in step b) is not necessary for this titanium alloy. In step c), the following gas cooling rates are used: Between 960°C and 900°C, the flow rate is 600K / min. Between 900 and 800°C, the rate is 2460K / min. Between 800 and 700°C, the flow rate is 1440K / min. Between 700 and 600°C, the flow rate is 1020 K / min, and Between 600 and 500°C, the flow rate is 600K / min. The material to be processed is quenched by cooling it with nitrogen gas according to the procedure.

[0061] The gas temperature is measured using a thermocouple. In this case, no aging treatment is performed. In step e), the workpiece is cooled to room temperature. Steps a), b), and c) are all performed in a hot isostatic pressurizer under nitrogen gas at a maximum pressure of 170 MPa.

[0062] In one embodiment, the surface hardening treatment can be carried out by thermal diffusion of at least one nonmetallic element, preferably selected from the group of oxygen, carbon, and nitrogen for titanium and titanium alloys, and from the group of nitrogen and carbon for austenitic stainless steel. The heat treatment is typically carried out at high temperatures and in a controlled atmosphere containing oxygen, nitrogen, and / or a gas containing carbon, nitrogen, and oxygen, as described, for example, in International Publication No. 2017 207 794 A1 for titanium and titanium alloys, and in International Publication No. 2011 009 463 A1 for austenitic stainless steel.

[0063] Another example of heat treatment can be carried out by ion implantation at low to medium vacuum, as described, for example, in International Publication No. 2010 063 928 A1 of a patent application. In a vacuum chamber, an ion source, such as an electron cyclotron resonance (ECR), generates an ion beam of a desired chemical element. Once ionized, the chemical element collides with the target component and is implanted into its surface, resulting in simultaneous heating of the surface, which in turn promotes ion diffusion.

[0064] The hardened layer can have a hardness exceeding 800 HV at a depth of at least 5 μm, preferably 10 μm, with a preferred range of 10 to 80 μm. Sufficient layer thickness is necessary because finishing operations such as polishing, sandblasting, or brushing may be performed after the surface hardening treatment.

[0065] In one embodiment, the material forming the other of the friction surfaces (the material having a lower surface hardness than silica and / or feldspar), which has a lower hardness than silica and / or feldspar, is an unhardened or at least surface-unhardened metal or alloy, preferably an unhardened or at least surface-unhardened titanium or titanium alloy, or an unhardened or at least surface-unhardened steel, preferably an unhardened or at least surface-unhardened austenitic steel, or a metal matrix composite, or a noble metal alloy containing Au, Ag, Pd or Pt.

[0066] Unhardened means that the material has not been intentionally hardened. Unhardened surface means that the material has not been intentionally surface-hardened. In particular, the material is not hardened at all (unhardened). Therefore, wear reduction is achieved while keeping manufacturing effort low. Whole hardened means that the components have been hardened so that the hardness increases throughout the entire component. In particular, the resulting hardness is substantially constant throughout the entire component.

[0067] Materials having a surface hardness lower than silica and / or feldspar may be metals or alloys. These materials may be overall hardened by, for example, quenching or precipitation, or surface hardened. Preferred surface hardening treatments are thermal diffusion, ion implantation, and thermal oxidation. However, the surface hardness will not exceed that of silica and feldspar. Preferably, materials having a surface hardness of 120 to 500 HV 0.025 are selected. Examples of the above materials include stainless steel, 904L stainless steel, nickel-free stainless steel, titanium and titanium alloys, preferably β-titanium alloys, near-β-titanium alloys, Grade 2 and Grade 5 titanium alloys, metal matrix composites, aluminum alloys containing TiAl, metallic glasses (zirconium-based, titanium-based, copper-based, platinum-based, or palladium-based), precious metal alloys (alloys based on gold, platinum, or palladium), magnesium alloys, and alloys derived from Group 4 of the periodic table. The material may be at least one material selected from the group consisting of metal matrix composites (MMC); metallic glass; precious metal alloys; magnesium alloys; aluminum alloys; copper alloys; and binary and ternary alloys of group IVB. Preferably, the material is selected from the group consisting of metallic glass based on zirconium, titanium, palladium, and copper; austenitic stainless steel; nickel-free austenitic stainless steel; titanium alloys of β-titanium, near-β-titanium, grade 2 titanium, and grade 5 titanium; aluminum alloys; CuAl-type copper alloys; precious metal alloys of silver, gold, platinum, and palladium; and binary and ternary alloys of group IV metals such as titanium, zirconium, and hafnium. More preferably, the material can be selected from the group consisting of P558, P2000, and Biodur® high nitrogen austenitic stainless steels; 316L and 904L type austenitic stainless steels; TiAl type aluminum alloys; β-titanium, near-β-titanium, Grade 2 titanium, and Grade 5 titanium titanium alloys; precious metal alloys of silver, gold, platinum, and palladium; and binary and ternary alloys of titanium, zirconium, and hafnium.

[0068] In the case of bracelets where the links are made of metal or alloy, the joint pins are specifically made of the same metal or alloy as the links, but with a different surface hardness. For example, links made of Grade 5 titanium and pins made of surface-hardened Grade 5 titanium are selected.

[0069] The above-mentioned unhardened material can be combined with surface-hardened titanium alloy or stainless steel pins. Thus, the present invention makes it possible to manufacture a bracelet in which all parts are made of titanium or titanium alloy using surface-hardened links or pins, without incurring the titanium-to-titanium friction that is conventionally known to cause high wear due to bonding, in order to utilize this low-density material.

[0070] In one configuration, the pin and the first component, and / or the pin and the second component, are made of the same material. Different surface hardnesses can be achieved through post-treatment, such as hardening. For example, both components can be made of titanium, titanium alloy, or austenitic steel.

[0071] Further aspects of the present invention are assembly devices, and more particularly, methods for obtaining assembly devices according to the present invention. The method includes treatment of a friction surface selected from heat treatment, thermochemical treatment, ion implantation treatment and mechanical cold working. In particular, only the surface is treated to achieve a hardening treatment such that the bulk material beneath the surface is not hardened or is not hardened to a significant extent. All the features, embodiments and advantages of the assembly devices described first can also be applied to the method, and vice versa. In particular, friction surfaces having a surface hardness higher than that of silica and / or feldspar are treated as described.

[0072] In one embodiment, the treatment is selected from nitriding, carburizing, or carbonitriding heat treatment for surface hardening of steel, and / or heat treatment using at least one element selected from oxygen, nitrogen, and carbon for surface hardening of titanium alloys.

[0073] A further aspect of the present invention is a bracelet comprising at least one assembly device according to the present invention, the bracelet being particularly a wristwatch bracelet.

[0074] A further aspect of the present invention is a wristwatch comprising a bracelet having at least one assembly device according to the present invention. In one embodiment, the wristwatch comprises a bracelet, and the assembly device is part of the bracelet. All the features, embodiments, and advantages of the assembly device and method described above can also be applied to the bracelet and the wristwatch, and vice versa.

[0075] Hereafter, illustrative implementations of the present invention will be described in more detail with reference to the drawings. Unless otherwise indicated, the features of the illustrative implementations can be combined individually or in combination with the objects described in the claims. The scope of protection described in the claims is not limited to the illustrative implementations. [Brief explanation of the drawing]

[0076] [Figure 1] A diagram showing the hardness profile of the sample. [Figure 2] A diagram showing the hardness profile of another sample. [Figure 3] A graph comparing wear volume. [Figure 4] A diagram showing an optical microscope image of a worn disk. [Figure 5] A diagram illustrating the protective effect in general terms. [Figure 6] A diagram showing the assembly device according to the present invention. [Figure 7] A diagram showing a part of a watch bracelet according to the present invention. [Figure 8] A diagram showing a cross-section of a rotatable mounting device according to the present invention. [Figure 9] A diagram showing the pins of the assembly device according to the present invention. [Figure 10] A figure showing a further assembly device according to the present invention.

[0077] [experiment] The experiment was conducted using the materials shown in Table 1. [Table 1]

[0078] 904L steel is a corrosion-resistant super austenitic steel that conforms to the standard AISI 904L (1.4539) standard, with high content of Mo and Cu in addition to Ni and Cr.

[0079] The formula is X1NiCrMoCu25-20-5. Other notations include SS2562 (Sweden), UNS N08904 (USA), and AFNOR Z2NCDU25-20 (France). Nivaflex 45 / 18 (registered trademark) is a non-magnetic Co-Ni-Cr alloy. The alloy contains 42-48% Co, 15-25% Ni, 16-22% Cr, and 2-6% Mo, W, and Fe respectively, as well as trace amounts of Ti, Mn, and Si. The amount of C is less than 0.15 wt%. Grade 5 titanium is a titanium alloy compliant with ASTM B348 containing 6 wt% Al and 4 wt% V. Silica nanoparticles are d 50 =30μm and d 90 These are commercial-grade silica particles (SiO2) with a particle size of 62 μm. The particle size distribution is measured by laser diffraction according to ISO 13320:2020. These particles are available from Sibelco under the product name Sibelco Sepasil B 5 / 63.

[0080] Annealing subjects a component to heat treatment throughout its entirety, resulting in uniform hardness across the entire component. Typically, hardness decreases with annealing. Therefore, the hardness is lower than that of a component of the same material that has been hardened or surface-hardened. <Experiment 1>

[0081] Figure 1 shows the hardness profile obtained by Vickers hardness test of a surface-hardened control sample made of 904L steel. Figure 2 shows the hardness profile obtained by Vickers hardness test 5 of a surface-hardened control sample made of surface-hardened Grade 5 titanium. The Grade 5 titanium components were surface-hardened by thermal diffusion of oxygen in a controlled atmosphere. The 904L steel components were surface-hardened by thermal diffusion of carbon in a controlled atmosphere of a carbon-containing gas mixture.

[0082] In both cases, the horizontal axis represents the depth D in μm from the surface of each control sample where the measurement was taken. Therefore, HS represents the hardness value near the surface, and HB represents the bulk hardness of the inner portion of the control sample. The vertical axis represents the hardness. In Figure 1, the hardness shown is Vickers hardness HV0.025, measured with a load of 0.025 kgf (kilogram-force) using a hardness tester compliant with ISO 6507-1, 2nd edition, 1997. In Figure 2, the hardness shown is instrumented Vickers hardness HVIT, measured by nanoindentation compliant with ISO 14577-1, 1st edition, 2002, Metallic materials - Instrumented indentation hardness tests and material parameters - Part 1: Test methods.

[0083] The hardness profile of 904L steel was measured using a microhardness tester (in accordance with ISO 6507-1, 2nd edition, 1997) with a load of 0.025 kgf. For surface-hardened Grade 5 titanium, the hardness profile was measured by nanoindentation in accordance with ISO 14577. The thickness of the hardened layer can be measured using a metallographic cross section in which the layer can be visualized under an optical microscope. On the other hand, it may be necessary to measure the hardness profile in parallel and determine the correspondence between the depth at which the hardened layer can be identified by optical contrast and the hardness according to the profile at that depth.

[0084] The drawing shows a hardness gradient from the surface to the bulk. Hardness is higher on and near the surface, and lower in the bulk. The effect of surface hardening extends from approximately 30 μm for steel to approximately 50 μm for titanium. Beyond this depth, the hardness is the same as that of the untreated material.

[0085] The thickness of the hardened layer can be defined as the depth to which its hardness reaches a certain value higher than the core hardness of the sample. According to this definition, for example, the thickness of the surface hardened layer of Grade 5 titanium is 8 μm to 12 μm for a hardness of 800 HV. For hardened 904L steel, it is 15 μm to 18 μm for the same hardness. <Experiment 2>

[0086] This experiment concerns the friction and wear properties of the materials used. A friction and wear tester is a device that allows two materials to rub against each other in a controlled manner. The friction and wear tester used can also be called a pin-on-disk friction and wear tester. This tester has an arm to which a hemispherical pin made of one of the test materials is attached, which presses a disc made of the second material with a predetermined force. The disc is made to move linearly under the pin with an amplitude adjusted to mimic the movement of a watch with a bracelet being worn. In the test performed, the amount of wear is measured using a confocal microscope. The confocal microscope allows for accurate imaging of the shape of the wear marks on the pin and the disc, respectively. The amount of wear is then determined by measuring the amount of material that peels off and forms wear marks during the test. Surface-hardened pins made from 904L steel and Grade 5 titanium were prepared as control samples in Experiment 1.

[0087] Figure 3 shows the results of a test under contaminated conditions in a friction and wear testing machine. This test is intended to replicate the actual conditions under which a watch bracelet is worn. The test was performed in ambient air containing an additive called a "synthetic contaminant." The additive consists of an abrasive in the form of silica powder and an organic oil, as described in European Patent Application Publication No. 2 057 914 A1.

[0088] The average wear volume of pin P (black) and disc Di (white) over two tests is shown on the vertical axis in cubic micrometers on a logarithmic scale. The tested material pairs are shown on the horizontal axis as A, B, C, and D. The pin material is stated first, followed by the disc material (pin / disk). A is Nivaflex cobalt alloy with an unhardened surface / 904L steel with an unhardened surface; B is Grade 5 titanium with an unhardened surface / Grade 5 titanium with an unhardened surface; C is Grade 5 titanium with a hardened surface / Grade 5 titanium with an unhardened surface; D is Grade 904L steel with a hardened surface / 904L steel with an unhardened surface.

[0089] A corresponds to prior art and is shown as a reference embodiment. This reference embodiment demonstrates wear of pins and discs due to friction between a disc made of unhardened 904L steel and pins made of Nivaflex-type cobalt superalloy, which are standard material conditions in the field of watch bracelets. The 904L steel components have a hardness in the range of 150-250 HV0.025, and the Nivaflex components have a hardness in the range of 350-500 HV0.025.

[0090] B is another reference embodiment, showing wear of a pin and a disk due to friction between a disk with an unhardened surface of Grade 5 titanium and a pin with an unhardened surface of Grade 5 titanium. Both components of this tribological pair have a hardness in the range of 250–350 HV0.025.

[0091] C is an embodiment of the present invention, showing wear of a pin and a disc due to friction between a disc made of unhardened Grade 5 titanium and a pin made of Grade 5 titanium that has been surface-hardened by thermal diffusion of oxygen atoms. The disc has a hardness in the range of 250 to 350 HV 0.025, and the pin has a surface hardness of over 900 HV 0.025.

[0092] D is another embodiment of the present invention, showing wear of a pin and a disc due to friction between a disc made of 904L steel with an unhardened surface and a pin made of 904L steel that has been surface-hardened by the thermal diffusion of carbon atoms. The disc has a hardness in the range of 150 to 300 HV 0.025, and the pin has a surface hardness greater than 900 HV 0.025.

[0093] The remarkable wear reduction effect in the tribological pairs of the present invention using surface-hardened pins, as shown in C and D, is significant. The difference compared to the reference embodiment of Nivaflex / 904L and unhardened Grade 5 Titanium / unhardened Grade 5 Titanium, as shown in A and B of Figure 3, is nearly two orders of magnitude. In particular, the wear of the “soft” discs (unhardened 904L and unhardened Grade 5 Titanium) is reduced when rubbed against surface-hardened materials in the presence of synthetic contaminants.

[0094] Figure 4 shows a microscopic image of a worn disc. Additional analyses were performed to better understand the reduction in wear of soft components (disks of 904L with an unhardened surface and Grade 5 titanium with an unhardened surface) when rubbed against components with a surface hardened surface. The images in Figure 4 show the wear patterns of a Grade 5 titanium disc with an unhardened surface when rubbed against a Grade 5 titanium pin with a surface hardened surface (Figures 4A and 4C; according to the present invention) and against a pin with an unhardened surface (Figures 4B and 4D; comparative example). These images present another example showing the difference in wear volume when the same disc without surface hardening is rubbed against a pin with a surface hardened surface or a pin with an unhardened surface. It is clearly observed that the disc wears more (the wear spots are larger) when the pin is not surface hardened.

[0095] Scanning electron microscopy analysis of the abraded surfaces shown in Figures 4C and 4D reveals why less abrasion is observed on the disk when using surface-hardened pins compared to when using unhardened pins. In the lower images 4C and 4D, the letter S indicates silica microparticles incorporated into the softer, unhardened disk. It is clearly observed that in the case of surface-hardened pins, a significantly larger amount of silica microparticles are incorporated into the softer counterpart, i.e., the disk, compared to the case of unhardened pins.

[0096] Comparing these two figures, it is clear that the silica contained in the synthetic contaminant behaves differently in each case. When both components are not surface-hardened (Figures 4B and 4D; comparative examples), silica penetrates both the disc and the pin because these two parts have lower hardness than the silica contained in the abrasive (the disc and the pin made of unhardened Grade 5 titanium have a hardness of 250-350 HV 0.025, while the silica powder has a hardness of 500-800 HV). Each time the pin passes over the disc, the material is peeled off on either side, causing significant wear.

[0097] On the other hand, when the pins are surface-hardened (Figures 4A and 4C; according to the present invention), the abrasive particles penetrate the disc but do not penetrate the pins, which have a surface hardness higher than 900HV0.025. Due to their higher hardness, the pins will cut (by abrasion) the silica that has penetrated the disc without being damaged. The inventors also note that there is no "digging" of the disc, as observed in tests using pins with unhardened surfaces (Figure 4D; comparative example). In the configuration according to the present invention, the presence of silica appears to protect the disc from wear.

[0098] Tests using friction and wear testing machines have shown that by surface hardening one of the two components (e.g., a pin), silica acts as a boundary between the two components, protecting the softer component (e.g., a disk or link).

[0099] Figure 5 schematically illustrates the protective effect of silica microparticles against wear in articulated links (rotatable fixtures). P represents a pin, 1 represents a first component, such as a bracelet link, and S represents silica microparticles. The silica microparticles S are incorporated into the softer link body 1, protecting the link body from abrasive wear caused by the microparticles.

[0100] The presence of silica at the boundary between the pin and the link restricts contact, thus minimizing or avoiding link wear. Since the pin is harder than the silica, it is either undamaged or only slightly damaged, and even appears to "polish" the silica. This mechanism is made possible by the fact that one of the two components is harder than the abrasive. <Experiment 3>

[0101] When pins made of unhardened Grade 5 titanium are driven into openings (holes) in unhardened Grade 5 titanium links, the surface will delaminate during this process because the two components have similar hardness. This delamination can significantly reduce the strength of the assembly.

[0102] This problem can be solved if, for example, the pins are surface-hardened, creating a difference in hardness between them and the links. Therefore, if the pins are surface-hardened, assembly can be carried out by driving the pins into components of the same material that have not been surface-hardened. This opens up new possibilities for assembling components of the same material, especially for Grade 5 titanium, the most commonly used titanium alloy, which is difficult to create a significant difference in hardness between an unhardened surface and a fully hardened surface.

[0103] Table 2 below shows the results of a pinning test in which surface-hardened or non-hardened pins were driven into a second part with a non-hardened surface. OK means high assembly reliability, and NOK means low assembly reliability.

[0104] [Table 2]

[0105] Figure 6 schematically shows an assembly device 10 for pivotably mounting two watch components 1 and 2 according to the present invention. The assembly device 10 comprises a first component 1 and a pin P. One side of the pin P, which is the upper side in this embodiment, is rotatably connected to the first component 1. The other, lower side of the pin P is mechanically connected to a second component, which may or may not be part of the assembly device. For this purpose, the pin P has means 7 on its lower side for mechanically connecting to the second component 2. The mechanical connection can generally be one that limits the degree of freedom in the direction along the pin, but allows the pin itself to rotate around the pivot axis. However, in particular, the pin P is configured to be firmly mounted or fixed inside an opening 21 in the second component 2. The opening 21 may be, for example, a blind hole.

[0106] For example, pin P may have a substantially circular cross-section. Pin P may also have a non-circular cross-section in one of its end regions. For example, pin P may have a corrugated surface. Alternatively, pin P may further have a circular cross-section in the end region to achieve a press-fit or bond connection with a second part 2.

[0107] The pin P has a second friction surface 5, particularly in its upper region which has a substantially circular cross-section. The first part 1 has a corresponding first friction surface 4. The first friction surface 4 and the second friction surface 5 are configured to guide each other to pivot during relative rotation between the first part 1 and the pin. The first friction surface 4 of the first part 1 is provided by the inner side of an opening 11, which is typically configured as a blind hole.

[0108] The first friction surface 4 and the second friction surface 5 are configured such that one of the friction surfaces, for example the second friction surface 5 of pin P, has a surface hardness higher than that of silica and / or feldspar, and the other friction surface, for example the friction surface 4 of the first part 1, has a surface hardness lower than that of silica and / or feldspar.

[0109] Specifically, the first friction surface 4 contains the first material A, and the second friction surface 5 contains the second material B. One of the first and second materials A and B has a surface hardness H1, and the other of the first and second materials A and B has a surface hardness H2. Specifically, H1 < Hm < H2, where Hm is the hardness of silica and / or feldspar. In particular, Hm is the hardness of fine particles of silica and / or feldspar.

[0110] FIG. 7 shows a possible use of the present invention in the form of a part of a bracelet for a wristwatch shown as being in the process of assembly. The bracelet includes several bracelet links M1, M2, M3 that are pivotally attached or articulated to each other. Additional bracelet links and / or other wristwatch parts, such as a wristwatch case and / or a bracelet clasp that may be pivotally attached to the left and / or right side, etc., are omitted for clarity. Each bracelet link M1, M2, M3 includes a first outer link part M1a, M2a, M3a, a second outer link part M1b, M2b, M3b, and a central link part M1c, M2c, M3c between the respective outer link parts. In particular, all parts of the bracelet links M1, M2, M3 are firmly attached to each other, and as a result, each bracelet link M1, M2, M3 forms a rigid body unit.

[0111] The first and second outer link parts M1a, M2a, M3a, M1b, M2b, M3b each have an opening for accommodating a part of a pin. In particular, the opening has a circular cross-section. The opening may be configured as a pocket hole. As another example, one of the openings of the outer link parts M1a, M2a, M3a, M1b, M2b, M3b may be configured as a threaded hole and / or a through hole so as to be able to receive a screw for a so-called extension link. The openings of the first and second outer link parts of each bracelet link M1, M2, M3 are aligned in a straight line so as to be able to accommodate two end regions of a straight pin or a screw therein.

[0112] Each of the central link components M1c, M2c, and M3c has an opening 11 for accommodating the central portion of the pin. In particular, the opening 11 is a through hole capable of holding the central portion of the pin within it.

[0113] The watch bracelet shown in Figure 7 comprises several assembly devices according to the present invention. As indicated in parentheses, bracelet link M1 corresponds to the first component 1, and bracelet link M2 corresponds to the second component 2. Since bracelet links M1 and M2 overlap, the parentheses also overlap. The first component 1 has a first friction surface inside the opening or through hole of the central link component M1c. The second component 2 holds both ends of a pin, particularly in a fastening manner, using its first and second outer link components M2a and M2b. The pin has a second friction surface 5 on its central circumferential surface.

[0114] In addition to the above, with respect to the pin located between M2 and M3, bracelet link M2 also corresponds to a first component, and bracelet link M3 corresponds to a second component. The first component 1 has a first friction surface inside the opening or through hole of its central link component M2c. The second component 2 holds both ends of the pin using its first and second outer link components M3a and M3b. This can be repeated several times in a watch bracelet. Most of the opening 11 and pin P are hidden inside the structure, but the opening 11 of bracelet link M3 and pin P of bracelet link M1 can be seen at the outermost part of the bracelet portion in the figure.

[0115] Figure 8 shows a cross-section of the rotatable fixture according to the present invention, particularly in the plane indicated by line L in Figure 7. It can be seen that the pin P is mechanically connected to the second part 2, specifically, using, for example, the first outer link part M3a and the second outer link part M3b of the bracelet link M3 shown in Figure 7. The pin P has means 7 for mechanical connection to the second part 2 at its end portions, i.e., the first end portion 43 and the second end portion 44. The pin P may be able to rotate freely inside the opening of the second part 2. However, in particular, the pin P is fixed inside the opening in a manner that locks its rotation. This is usually accomplished by driving the pin P into the opening to provide a press-fit and / or shape-fit mounting. In an alternative example, the pin P can be bonded inside the opening of the second part 2 by welding, brazing, or adhesive. In a further alternative example, the rotation of the pin P may be locked by another element such as a screw.

[0116] The central portion 41 of the pin P passes through an opening, or through hole, in the first component 1, for example, in the central link component M2c of the bracelet link M2. The outer circumferential surface of the central portion 41 forms the second friction surface 5 of the pin. The inner circumferential surface of the through hole forms the first friction surface 4 of the first component 1. When the first component 1 and the second component 2 rotate relative to each other, the friction surfaces 4 and 5 contact and guide each other.

[0117] Figure 9 shows another embodiment of the pin P configured as a screw nail. In this case, the pin P is screwed into the second part rather than driven in. The pin P has a screw head 40 at a first end portion 43 shown on the left. At the opposite second end portion 44 shown on the right, the pin has a threaded portion 42 as a means 7 for mechanically securing it to the inside of an opening in the second part. Around the central portion 41, the first part 1 is arranged and configured in the shape of a sleeve 6. The inner circumferential surface of the sleeve 6, which is particularly annular, serves as a first friction surface 4 for pivotally guiding the pin P. The outer circumferential surface of the pin P serves as a second friction surface 5.

[0118] The first end portion 43 of the pin may have a sleeveless portion between the screw head 40 and the sleeve 6 when viewed axially. This portion may be configured to be mechanically connected, for example, fixed, to an opening in another part, such as a second part, or may have means for mechanical connection. For example, this portion of the pin P can be attached to the second part by press fitting or using additional components.

[0119] Figure 10 shows an assembly device 10 similar to the assembly device 10 described above, with reference to Figure 6. Only the differences from the configuration in Figure 6 will be described below. The assembly device 10 in Figure 10 has two pins P configured to be coaxially arranged at different axial positions on the pivot axis. A portion of a second part 2 is positioned between the two pins P. In this case as well, the second part 2 may or may not be part of the assembly device 10.

[0120] Each pin P has a side that is rotatably connected to the first component, i.e., the upper side of the upper pin P and the lower side of the lower pin P, and the opposite side of each is mechanically connected to the second component 2. List of Reference Codes Part 1 Part 2 First friction surface 4 Second friction surface 5 Sleeve 6 means 7 Assembly device 10 Opening 11 Opening 21 Screw head 40 central part 41 Threaded part 42 First end portion 43 Second end portion 44 Pin P Bracelet links M1, M2, M3 First outer link parts M1a, M2a, M3a Second outer link parts M1b, M2b, M3b Center link parts M1c, M2c, M3c Depth D Surface hardness HS Bulk hardness HB Disc Di Silica microparticles S line L

[0121] Materials that have a surface hardness higher than silica or feldspar and can be made into metals or alloys are particularly subjected to surface hardening treatment. Surface hardening treatment makes the material particularly wear-resistant.

[0122] The use of surface hardening treatment offers further advantages. Standard materials can be used for bracelet components such as shafts and links. Standard manufacturing and assembly methods, such as pinning, can be used. These methods, associated with surface hardening treatment, have been shown to be well-suited for reducing wear on critical attached components of watches.

[0123] The materials that can be used are hypoallergenic and corrosion-resistant. Surface hardening treatment is possible even for materials that are not necessarily suitable for bulk hardening. Therefore, a wider range of materials can be used. In particular, the surface hardening materials are titanium alloys or austenitic stainless steels.

[0124] Surface-hardened materials are easier to prepare, in contrast to ceramics and bulk-hardened materials, for example, because they can be machined while the material surface is still in an unhardened state before the surface hardening process. Machining unhardened metal components saves time and money. In addition, it is sufficient to reduce the number of components to be surface-hardened, thereby minimizing manufacturing costs.

[0125] The present invention allows for the manufacture of articulated assemblies with a minimum number of components. Sleeves or inserts are not required. Maximizing the cross-section of the shaft ensures mechanical resistance and minimizes the profile of the bracelet. Assembly is easily performed by, for example, driving the shaft into each hole of the link.

[0126] The use of titanium alloys and austenitic stainless steels is advantageous because they can be surface-hardened while simultaneously retaining high bulk toughness compared to ceramics and similar brittle materials.

[0127] In one configuration, the same material can be used for both parts, with one being surface-hardened and the other unhardened. The bulk hardness of titanium alloys and austenitic stainless steels is lower than that of silica and / or feldspar, allowing for the incorporation of fine particles that reduce tribological wear. This reduction is achieved by surface-hardening only one of the friction surfaces, typically the axle, which can be manufactured from the same material.

[0128] Hardening the first friction surface of the pin instead of the second friction surface simultaneously reduces tribological wear at the joint and scratch formation on the outer surface of the links, which is advantageous because it maintains the aesthetic appearance of the bracelet by reducing scratch formation. In addition, using the same material for both friction surfaces makes it possible to achieve a similar color between the surface-hardened components and the components with unhardened surfaces.

[0129] The use of surface hardening treatment improves pin insertion performance compared to bulk hardening treatment. This is because the risk of brittle pin fracture is reduced, thus increasing process reliability. In other words, surface hardening treatment results in a type of composite material component having a relatively soft metal core with high toughness to reduce tribological wear, and a hard, ceramic-like surface that has high adhesion to the soft core.

[0130] For at least one or both of the articulated components, it is not necessary to use brittle and rigid bulk material or brittle and hardened bulk material. Additional sleeves and / or inserts are not required to reduce the risk of fracture of rigid and brittle components. Thus, the technical burden is reduced and manufacturing becomes easier.

Claims

1. An assembly device (10) for pivotably mounting at least two components of a wristwatch, the assembly device (10) comprising a first component (1) and at least one pin (P) having means (7) for mechanically connecting to a second component (2), wherein the first component (1) has a first friction surface (4) and the pin (P) has a second friction surface (5), and the first friction surface (4) and the second friction surface (5) come into contact with each other during pivotal movement. One of the friction surfaces (4 or 5) has a surface hardness higher than that of silica and / or feldspar, and the other of the friction surfaces (5 or 4) has a surface hardness lower than that of silica and / or feldspar. An assembly device characterized in that the material forming one of the friction surfaces (4, 5), which has a surface hardness higher than that of silica and / or feldspar, is a surface-hardened metal or alloy.

2. The assembly device (10) according to claim 1, characterized in that the pin (P) has means (7) for fixing inside the opening (21) of the second component (2).

3. The assembly device (10) according to any one of claims 1 to 2, characterized in that the first component (1) comprises at least one opening (11) having an inner circumferential surface that provides a first friction surface (4), and / or the pin (P) comprises an outer circumferential surface that provides a second friction surface (5).

4. The assembly device (10) according to any one of claims 1 to 3, characterized in that the pin (P) has a screw head (40) at a first end portion (43) and a threaded portion (42) at a second end portion (44).

5. The assembly device (10) according to any one of claims 1 to 4, characterized in that the pin (P) comprises a central portion (41), a first end portion (43), and a second end portion (44), the first end portion (43) and the second end portion (44) are designed to be mechanically connected to a second component (2).

6. The assembly device (10) according to any one of claims 1 to 5, characterized in that the first component (1) is configured as a sleeve (6) arranged around a portion of the pin (P).

7. The assembly device (10) according to any one of claims 1 to 6, characterized in that the first component (1) and / or the second component (2) are bracelet links (M1, M2, M3).

8. The assembly device (10) according to any one of claims 1 to 7, characterized in that the first component (1) or the second component (2) is a watch case.

9. The assembly device (10) according to any one of claims 1 to 8, characterized in that the first component (1) or the second component (2) is a bracelet clasp.

10. The assembly device (10) further comprises a second component (2), as described in any one of claims 1 to 9.

11. The assembly device (10) according to any one of claims 1 to 10, characterized in that one of the friction surfaces (4, 5), which has a surface hardness higher than that of silica and / or feldspar, has a surface hardness of at least 800 HV 0.025, preferably at least 900 HV 0.025, and more preferably at least 1000 HV 0.

025.

12. The assembly device (10) according to any one of claims 1 to 11, characterized in that the other of the friction surfaces (4, 5), which has a surface hardness lower than that of silica and / or feldspar, has a surface hardness of at most 500 HV 0.025, preferably at most 350 HV 0.025, more preferably at most 320 HV 0.025, and at least 120 HV 0.025, preferably at least 250 HV 0.

025.

13. The assembly device (10) according to any one of claims 1 to 12, characterized in that the second friction surface (5) of the pin (P) has a surface hardness higher than that of silica and / or feldspar.

14. The assembly device (10) according to any one of claims 1 to 13, characterized in that the surface-hardened metal or alloy is surface-hardened titanium or titanium alloy, or surface-hardened steel, preferably surface-hardened austenitic steel.

15. The assembly device (10) according to any one of claims 1 to 14, characterized in that the material forming the other of the friction surfaces (4, 5), which has a surface hardness lower than that of silica and / or feldspar, is a metal or alloy with an unhardened surface, preferably titanium or a titanium alloy with an unhardened surface, or steel with an unhardened surface, preferably austenitic steel with an unhardened surface, or a noble metal alloy of a metal selected from the group Ag, Au, Pt and Pd.

16. A method for obtaining an assembly device (10) according to any one of claims 1 to 15, comprising treatment of the friction surfaces (4, 5) selected from heat treatment, thermochemical treatment, ion implantation treatment and mechanical cold working.

17. The method according to claim 16, characterized in that the treatment is selected from nitriding, carburizing, or carbonitriding heat treatment for surface hardening of steel, and a heat treatment using at least one element selected from oxygen, nitrogen, and carbon for surface hardening of titanium alloy.

18. A bracelet comprising at least one assembly device (10) according to any one of claims 1 to 15.

19. A wristwatch comprising at least one assembly device (10) according to any one of claims 1 to 15.

20. The wristwatch according to claim 19, characterized in that the wristwatch comprises a bracelet, and the assembly device (10) is part of the bracelet.

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