Escapement wheel, tool for manufacturing an escapement wheel and method for manufacturing an escapement wheel

Abstract

The invention relates to a method for manufacturing an escapement wheel (10), comprising the steps of: - making an escapement wheel blank comprising a hub (11) connected to a rim (12) by radial arms (13), and teeth (14) regularly distributed around the periphery of the rim (12), - simultaneously machining a cross-section reduction of the free end of each tooth (14) by a cutting tool (20) aligned coaxially with the escapement wheel blank.

Description

Technical Field

[0001] This invention belongs to the field of watches, especially the field of mechanical watch movements.

[0002] More specifically, the present invention relates to an escapement wheel, a tool for manufacturing an escapement wheel, and a method for manufacturing an escapement wheel. Background Technology

[0003] The escape wheel is well-known in the watchmaking industry. It is designed to be connected to the mainspring, which provides energy to the escape wheel in order to maintain the oscillation of the balance wheel via the escape fork.

[0004] More specifically, the escape wheel includes a plurality of teeth distributed around a periphery of a rim, which is connected to a hub by radial branches. The escape fork includes escape fork pads designed to engage with these teeth of the escape wheel.

[0005] This fit generates friction, and for many years people have been trying to minimize its intensity in order to increase the lifespan of the escape wheel and the accuracy of time measurement.

[0006] The most common solution is to create a bevel at the end of each tooth of the escape wheel to reduce the contact surface between these teeth and the escape fork. This arrangement is combined with lubrication of the ends of these teeth.

[0007] While these solutions are satisfactory, the manufacture of the escapement mechanism presents some challenges. In particular, the bevel of each tooth is individually made through specific machining processes.

[0008] Besides being relatively slow, this manufacturing method also presents the problem of ensuring the tight tolerances required for watch applications. Summary of the Invention

[0009] The present invention addresses the aforementioned drawbacks by proposing a solution that allows for easy and rapid acquisition of an escape wheel, while ensuring the required size of the escape wheel is met.

[0010] Therefore, the present invention relates to a method for manufacturing an escapement wheel, the method comprising the following steps:

[0011] - A blank escape wheel is fabricated, which is designed to be driven to rotate about an axis of rotation and includes a hub connected to a rim by radial arms and teeth regularly distributed around the rim.

[0012] - The cross-sectional area of ​​the free end of each tooth is simultaneously machined using a cutting tool that is coaxially aligned with the escape wheel blank.

[0013] The term "coaxial" means that the axis of rotation of the cutting tool is the same as the axis of rotation of the escape wheel blank.

[0014] This feature allows for material removal at the free ends of these teeth to be performed in a single cutting operation, which ensures compliance with the escapement wheel's dimensional requirements while reducing the complexity of the escapement wheel and its manufacturing time.

[0015] In certain embodiments, the invention may further include one or more of the following features, which may be used individually or in any technically feasible combination.

[0016] In a particular embodiment, the reduced cross-section portion is formed by a reduced end portion including a bevel.

[0017] In a particular embodiment, the machined reduced cross-section portion includes a reduced end portion having a slew surface orthogonal to the plane of the escape wheel blank.

[0018] In a particular embodiment, the reduced cross-section portion is formed by a reduced end portion including a flat surface that is substantially parallel to the plane in which the escape wheel blank is located.

[0019] In a particular embodiment, the step of fabricating the escapement wheel blank is performed by the LIGA method.

[0020] In a particular embodiment, the machining step is performed by milling.

[0021] In a particular embodiment, the processing steps include the following series of operations:

[0022] - Position the cutting tool so that its axis of rotation is the same as the axis of rotation of the escape wheel blank;

[0023] - Guide the cutting tool to translate toward the escape wheel blank in a direction coaxial with the axis of rotation of the escape wheel blank, and remove a portion of the end of each tooth of the escape wheel blank in a single cutting operation to produce a reduced end portion;

[0024] - Remove the tool.

[0025] According to another aspect, the invention also relates to a cutting tool, for example, for implementing the method for manufacturing an escapement wheel as described above, the cutting tool comprising a generally cylindrical body intended to be driven to rotate about a rotation axis and including at least one cutting tooth at one end thereof, the cutting tooth having a cutting edge extending in a diametrical plane of the body, the cutting edge having a portion adapted to generate at least one revolution-shaped surface on the part to be machined, the axis of rotation of the revolution-shaped surface being coaxial with the rotation axis of the tool.

[0026] More precisely, the cutting edge is adapted to remove a portion of the free end of each tooth of the escape wheel blank to produce a reduced end portion.

[0027] In certain embodiments, the invention may further include one or more of the following features, which may be used individually or in any technically feasible combination.

[0028] In a particular embodiment, the cutting edge includes a portion called an "inclined portion" that forms an obtuse or acute angle with the axis of rotation of the tool.

[0029] In a particular embodiment, the cutting edge includes a portion referred to as a "straight section" that is parallel to the axis of rotation of the tool.

[0030] In a particular embodiment, the cutting edge includes a portion called a "right-angle portion" that forms a right angle with the axis.

[0031] In a particular embodiment, the cutting edge has a profile suitable for generating functional or decorative structures on the machined surface.

[0032] According to another aspect, the invention can relate to an escapement wheel, for example, an escapement wheel obtained by implementing the method for manufacturing an escapement wheel as described above, the escapement wheel comprising a hub connected to a rim by radial arms and teeth regularly distributed on the periphery of the rim, each tooth comprising a reduced end portion connected to the rim by a central portion. The reduced end portion of each tooth comprises a thickness reduced relative to the thickness of the central portion and comprises a surface of revolution, the surface of revolution of each tooth sharing the same axis of revolution.

[0033] Advantageously, the axis of rotation is the same as the axis of rotation of the escape wheel.

[0034] In certain embodiments, the invention may further include one or more of the following features, which may be used individually or in any technically feasible combination.

[0035] In a particular embodiment, the reduced end portion of each tooth includes a ramp, which is arranged in such a way that they have inclined surfaces that each form a part of the same truncated cone.

[0036] In a particular embodiment, the reduced end portion of each tooth includes an end face that defines the impact plane of the tooth, the end face having a rectangular trapezoidal shape.

[0037] In a particular embodiment, the reduced end portion of each tooth includes a flat surface substantially parallel to the plane in which the escape wheel lies, the flat surface being connected to the ramp.

[0038] In a particular embodiment, the reduced end portion of each tooth includes a gyratory surface and a flat surface substantially parallel to the plane of the escape wheel, the gyratory surfaces being arranged in such a way that they each form part of the same gyratory cylinder.

[0039] In certain embodiments, the rotary and / or flat surfaces of these teeth may have surface states that produce oleophobic or oleophilic effects. Attached Figure Description

[0040] Other features and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings:

[0041] - Figure 1 A perspective view of an escapement wheel according to an exemplary embodiment of the present invention is shown, along with a detailed view of one tooth of the escapement wheel;

[0042] - Figure 2 It shows Figure 1 Detailed view of the escape wheel;

[0043] - Figure 3 A detailed view of one tooth of an escapement wheel according to another exemplary embodiment is shown;

[0044] - Figure 4 A detailed view of one tooth of an escapement wheel according to yet another exemplary embodiment is shown;

[0045] - Figure 5 A perspective view of a cutting tool according to the invention, intended for forming an escapement wheel, is shown;

[0046] - Figure 6 It shows Figure 5 The bottom view of the tool. Detailed Implementation

[0047] Figure 1 An escape wheel 10 according to the invention is shown, which conventionally includes a hub 11 connected to a rim 12 via a radial arm 13, and a plurality of teeth 14 regularly distributed around the periphery of the rim 12 and extending in a direction orthogonal to the axis of rotation of the escape wheel 10.

[0048] In this document, a plane P (not shown in the figure) is defined in which the escape wheel 10 is disposed, which is perpendicular to the axis of rotation of the escape wheel 10. Furthermore, the term "thickness" as used elsewhere in this document refers to a dimensional dimension considered in relation to a direction parallel to the axis of rotation of the escape wheel 10.

[0049] like Figure 1As shown in the detailed view, each tooth 14 includes a reduced end portion 140 connected to the rim 12 via an intermediate portion 120. Advantageously, the reduced end portion 140 of each tooth 14 includes a thickness reduced relative to the thickness of the intermediate portion 120.

[0050] Each tooth 14 includes an end face 141 at the free end of a reduced end portion 140, the end face 141 defining an impact plane of the tooth 14. Those skilled in the art will recognize the concept of an "impact plane" for defining a surface intended to contact the pallet fork bearings of the escapement fork in order to transfer stress to the pallet fork bearings.

[0051] Furthermore, the reduced end portion 140 of each tooth 14 includes a rotary surface 142, which is arranged such that all rotary surfaces 142 of each tooth 14 share the same axis of rotation. This axis of rotation is advantageously the same as the axis of rotation of the escape wheel 10, such as... Figure 2 As shown.

[0052] In particular, Figure 1 and 2 In the exemplary embodiment shown, the rotary surface 142 of each tooth 14 forms an inclined surface 143, which is arranged in such a way that they have inclined surfaces that each form part of the same frustum, the axis of rotation of which is the same as the axis of rotation of the escapement wheel. Clearly, the term "frustum" as used herein refers to a virtual geometry in which the inclined surfaces are located, and its purpose is solely to define the arrangement of the inclined surfaces 143.

[0053] like Figure 1 As precisely shown in the detailed view, in addition to the rotary surface 142, the reduced end portion 140 of each tooth 14 may also include a flat surface 144 substantially parallel to the plane P. More precisely, the flat surface 144 is connected to the rotary surface 142 on one hand by a curved edge forming an arc, the center of which coincides with the axis of rotation of the escape wheel 10, and on the other hand by an edge opposite to the curved edge and perpendicular to the orthoradial direction of the tooth 14.

[0054] As an alternative to ramp 143, in Figure 3 In the exemplary embodiment shown in the detailed view, the rotary surfaces 142 can be arranged in such a way that they each form part of the same rotary cylinder whose axis of rotation is the same as the axis of rotation of the escape wheel 10.

[0055] In other words, with Figure 1 and 2 In contrast to the exemplary embodiment shown, the rotary surface 142 is orthogonal to the plane P, rather than inclined.

[0056] exist Figure 4 In another exemplary embodiment of the invention shown, each reduced end portion 140 includes only a single rotary surface 142 formed by the inclined surface 143. Therefore, the reduced end portion 140 no longer includes a flat surface 144 substantially parallel to plane P.

[0057] All the teeth 14 have inclined surfaces 143 that form part of the same frustum, the axis of rotation of which is the same as the axis of rotation of the escape wheel.

[0058] The inclined surface of each ramp 143 intersects with the end face 141, giving the end face 141 a right-angled trapezoidal shape. Therefore, it can be understood that the thickness of the free end of each tooth 14 is thus variable.

[0059] Advantageously, the rotary surface 142 and / or flat surface 144 of the tooth 14 can have a surface state that produces an oleophobic or oleophilic effect.

[0060] According to another aspect, the present invention relates to a cutting tool 20 for (machine) an escapement wheel blank to obtain an escapement wheel 10 as described above.

[0061] The cutting tool 20 is in the form of a milling cutter designed to be driven to rotate. For example... Figure 5 As shown, in an exemplary embodiment of the invention, the cutting tool 20 includes a generally cylindrical body 21, which includes a first end and a second end opposite to the first end. The body 21 is intended to be fixed to a tool carrier by means of the first end. The body 21 of the cutting tool 20 extends along a longitudinal axis that is the same as its axis of rotation.

[0062] The body 21 of the cutting tool 20 carries at least one cutting tooth 22 at its second end, which extends beyond the second end.

[0063] exist Figure 5 and 6 In the exemplary embodiment shown, the tool includes two cutting teeth 22, each having a cutting edge 220 extending in the diametrical plane of the body 21 of the cutting tool 20.

[0064] To be precise, especially as Figure 6 As shown, the two cutting teeth 22 are diametrically opposed and are respectively arranged on both sides of the diametrical plane of the body 21 of the cutting tool 20. In other words, the two cutting teeth 22 are identical and arranged in a centrally symmetrical manner relative to each other, with their axes being the same as the rotation axis of the cutting tool 20.

[0065] Each cutting tooth 22 has a cutting edge 220 that is capable of generating a rotary surface on the workpiece, the axis of rotation of which is coaxial with the axis of rotation of the tool.

[0066] More precisely, the portion referred to as the “tilted portion” 221 forms an obtuse or acute angle with the axis of rotation of the tool.

[0067] Figure 5 The cutting edge 220 is shown in particular, with its inclined portion 221 inclined toward the body 21 of the cutting tool 20. In other words, the distance between the inclined portions 221 of the two cutting edges 220 and each other increases as these cutting edges move away from the second end of the body 21 of the cutting tool 20.

[0068] This feature enables material removal to be performed on the teeth 14 of the escape wheel 10 blank during processing, in order to generate a rotary surface 142, which has the characteristics described above and as follows: Figure 1 and Figure 4 The shape of the inclined plane 143 is shown in the detailed view. During this material removal, the body 21 of the cutting tool 20 is arranged coaxially with the escape wheel blank, as described in more detail below.

[0069] Optionally, the cutting edge 220 may include a portion (not shown) parallel to the axis of rotation of the tool, referred to as a “straight section”. This straight section is advantageously suited to form a rotary surface 142 on each tooth 14 of the escape wheel during machining by the rotation of the cutting tool 20 about its axis of rotation, all rotary surfaces 142 representing a portion of the same cylinder.

[0070] In addition to the inclined portion 221 or the straight portion, the cutting edge 220 may also include a portion called a "right-angle portion" 222 that forms a right angle with the axis of rotation of the cutting tool 20. The right-angle portion 222 is advantageously located at the end of each cutting tooth 22 and is further away from the axis of rotation of the tool than the inclined portion 221 or the straight portion.

[0071] Advantageously, the right-angle portion 222 allows for the formation of a flat surface 144 of the reduced end portion 140 described above.

[0072] Furthermore, the inclined portion 221 or the straight portion and / or the right-angled portion 222 may have a profile that is adapted to produce functional or decorative structures on the rotary surface 142 and / or the flat surface 144 of the teeth 14 of the escape wheel 10.

[0073] The profile can specifically include a series of peaks and troughs.

[0074] The term "functional structure" here refers to a surface state that allows the processed surface to have oleophobic or oleophilic effects.

[0075] In a manner known to those skilled in the art, the cutting tooth 22 may include a relief angle and be made of any suitable material, such as polycrystalline cubic boron nitride, single-crystal or polycrystalline diamond, or hard metal, or a composite material having a metal matrix, such as tungsten-cobalt carbide or tungsten-nickel carbide, on which a suitable coating is deposited, such as a coating made of polycrystalline diamond, a coating made of “DLC” (diamond-like carbon), a coating made of titanium nitride, a coating made of titanium carbide, etc.

[0076] According to another aspect, the present invention also relates to a method for manufacturing the escapement wheel as described above.

[0077] The manufacturing method includes an initial step of manufacturing an escape wheel blank, which includes a rim 12, a hub 11 connected to the rim 12 by a radial arm 13, and a plurality of teeth 14 regularly distributed on the periphery of the rim 12.

[0078] After this step, the escape wheel blank is consistent with a conventional escape wheel, that is, an escape wheel of the prior art. Furthermore, during this initial step, the escape wheel blank can be obtained by any method known to those skilled in the art—for example, by punching and sawing.

[0079] However, for the reasons discussed in detail below, it is advantageous to obtain the escapement blank by the LIGA method.

[0080] The next step involves machining a reduced cross-sectional portion at the free end of each tooth 14 using a cutting tool 20, which is coaxially aligned with the escape wheel blank as described above, to obtain a reduced end portion 140 for each tooth 14. Thus, after implementing this method, the escape wheel 10 as described above is obtained.

[0081] Here, the term "coaxially aligned" means that the axis of rotation of the tool and the axis of rotation of the escape wheel blank are the same. Therefore, the reduced cross-section corresponds to the reduced thickness of the tooth 14 of the escape wheel blank.

[0082] The processing step can be performed in such a way that the processed cross-sectional reduction portion includes a reduced end portion 140 having the shape of a rotary surface 142 forming a bevel 143.

[0083] Alternatively, the processing step can be performed in such a way that the processed cross-sectional reduction portion includes a reduced end portion 140 having a shape of a revolution-shaped surface 142 orthogonal to plane P.

[0084] Alternatively, the processing step can be performed in such a way that the processed cross-section reduction portion includes a reduced end portion 140, which is formed by a flat surface 144 substantially parallel to plane P, in which the escape wheel is located.

[0085] In another exemplary embodiment of the method, the processing step may be performed in such a way that the processed cross-sectional reduction portion includes a reduced end portion 140 formed only by the inclined surface 143.

[0086] This machining step is advantageously performed by milling, and it includes the following series of operations:

[0087] - Position the cutting tool 20 so that the axis of rotation of the cutting tool 20 is the same as the axis of rotation of the escape wheel blank;

[0088] - In a single cutting operation, the guide cutting tool 20 is translated toward the escape wheel blank in a direction coaxial with the rotation axis of the escape wheel blank, and a portion of the end of each tooth 14 of the escape wheel blank is removed in order to reduce the thickness of the component; this operation can obtain a reduced end portion of each tooth 14.

[0089] - Remove cutting tool 20.

[0090] The reduced end portion obtained after the cutting operation, through the specific positioning of the cutting tool 20 relative to the escape wheel blank, is identical for all teeth 14 of the escape wheel on the one hand, and is obtained in a single machining operation on the other.

[0091] Advantageously, if the escape wheel blank is obtained by the LIGA method, it is made from a plurality of additional escape wheel blanks precisely distributed on a substrate. The substrate includes optical guide marks precisely arranged relative to the escape wheel blanks and adapted for reading by an optical sensor to indicate the precise position of each blank to the cutting tool 20. Therefore, by performing this optically, the operation of positioning the cutting tool 20 can be performed quickly and precisely for each escape wheel blank to be machined.

[0092] In addition, alternatively or additionally, during the operation of guiding the cutting or removing tool 20, the method may include an optical verification operation of the position of the cutting tool relative to the escapement wheel blank being machined or to be machined, so as to correct the position of the cutting tool 20 if necessary.

Claims

1. A method for manufacturing an escapement wheel (10), characterized in that, The method includes the following steps: An escape wheel blank is made, the escape wheel blank including a hub (11) connected to a rim (12) by a radial arm (13), and teeth (14) regularly distributed around the periphery of the rim (12). The cross-sectional area of ​​the free end of each tooth (14) is simultaneously machined by a cutting tool (20) that is coaxially aligned with the escape wheel blank. The processing steps include the following series of operations: Position the cutting tool (20) so that the axis of rotation of the cutting tool (20) is the same as the axis of rotation of the escape wheel blank; The cutting tool (20) is guided to translate toward the escape wheel blank in a direction coaxial with the rotation axis of the escape wheel blank, and a portion of the end of each tooth (14) of the escape wheel blank is removed in a single cutting operation to reduce the thickness of the end and create a reduced end portion (140). Remove the cutting tool.

2. The method according to claim 1, wherein, The reduced cross-section portion is formed by a reduced end portion (140) including a slope (143).

3. The method according to claim 1, wherein, The machined reduced cross-section portion includes a reduced end portion (140) having a slew surface (142) that is orthogonal to the plane containing the escape wheel blank.

4. The method according to claim 2 or 3, wherein, The reduced cross-section portion is formed by a reduced end portion (140) including a flat surface (144) parallel to the plane of the escape wheel blank.

5. The method according to any one of claims 1 to 3, wherein, The process of fabricating the escapement wheel blank is performed using the LIGA method.

6. The method according to any one of claims 1 to 3, wherein, The machining steps are performed by milling.

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