CH718798A2 - Escape wheel, tool for manufacturing an escape wheel and method of manufacturing an escape wheel. - Google Patents

Abstract

The invention relates to a method of manufacturing an escape wheel (10) comprising the steps of: producing an escape 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), simultaneous machining of a reduction in section of the free end of each tooth (14), by a tool shot coaxially aligned with the escape wheel blank. The invention also relates to such an escape wheel and to a cutting tool for implementing such a manufacturing method.

Description

Technical field of the invention

The invention relates to the field of watchmaking, and in particular mechanical watch movements.

More particularly, the invention relates to an escape wheel, a tool for manufacturing an escape wheel and a method of manufacturing an escape wheel.

Technology background

[0003] An escape wheel is well known in the field of watchmaking and is intended to be connected to a mainspring which supplies it with energy in order to maintain the oscillations of a balance wheel by means of a anchor.

[0004] More specifically, the escape wheel has teeth distributed around the periphery of a rim connected to a hub by radial branches. The anchor comprises pallets intended to cooperate with the teeth of the escape wheel.

[0005] This cooperation generates friction, the intensity of which has been sought for years to minimize in order to increase the life of the escape wheel and the precision of time measurement.

[0006] The most common solutions are the generation of a bevel at the end of each tooth of the escape wheel in order to reduce the contact surface between said teeth and the lifts. This arrangement is coupled with the lubrication of the end of said teeth.

[0007] Although these solutions are satisfactory, the manufacture of the exhaust poses some difficulties. In particular, the bevel of each tooth is made individually, by special machining.

[0008] In addition to being relatively slow, this manufacturing method generates problems of guaranteeing the tight tolerances required by the watchmaking application.

Summary of the invention

The invention solves the aforementioned drawbacks by proposing a solution making it possible to easily and quickly obtain an escape wheel whose compliance with the dimensional requirements is guaranteed.

To this end, the present invention relates to a method of manufacturing an escape wheel comprising steps of: production of an escape wheel blank intended to be driven in rotation about an axis of rotation, and comprising a hub connected to a rim by radial arms, and teeth regularly distributed around the periphery of the rim, simultaneous machining of a reduction in section of the free end of each tooth, by a cutting tool aligned coaxially with the escape wheel blank.

[0011] The term "coaxial" means that the axis of rotation of the cutting tool coincides with the axis of rotation of the blank of the escape wheel.

[0012] Thanks to this characteristic, the removal of material at the free end of the teeth is carried out in a single cutting operation, which makes it possible to ensure compliance with the dimensional requirements of the escape wheel while reducing the complexity and manufacturing time of said escape wheel.

[0013] In particular embodiments, the invention may further comprise one or more of the following characteristics, taken in isolation or in any technically possible combination.

[0014] In particular embodiments, the section reduction is formed by a thinned end portion comprising a bevel.

[0015] In particular embodiments, the machined section reduction comprises a thinned end portion in the shape of a surface of revolution orthogonal to a plane in which the escape wheel blank is inscribed.

[0016] In particular embodiments, the section reduction is formed by a thinned end portion comprising a flat surface substantially parallel to a plane in which the escape wheel blank is inscribed.

[0017] In particular embodiments, the step of producing the blank of an escape wheel is carried out by the LIGA method.

[0018] In particular modes of implementation, the machining step is carried out by milling.

[0019] In particular modes of implementation, the machining step comprises the successive operations of: positioning the cutting tool so that its axis of rotation coincides with the axis of rotation of the escape wheel blank; guiding the cutting tool in translation towards the escape wheel blank in a direction coaxial with the axis of rotation of the escape wheel blank, and cutting off part of the end of each tooth of the escape wheel blank so as to generate a thinned end portion, in a single cutting operation; tool clearance.

According to another aspect, the present invention also relates to a cutting tool, for example for the implementation of a method of manufacturing an escape wheel as described above, comprising a substantially cylindrical body intended to be driven in rotation about an axis of rotation and comprising at one of its ends at least one cutting tooth having a cutting edge extending in a diametral plane of the body, said cutting edge having a portion adapted to generating, on a workpiece, at least one surface of revolution whose axis of revolution is coaxial with the axis of rotation of the tool.

[0021] More specifically, the cutting edge is adapted to cut out part of a free end of each tooth of an escape wheel blank, so as to generate a thinned end portion.

[0022] In particular embodiments, the invention may also comprise one or more of the following characteristics, taken in isolation or in all technically possible combinations.

[0023] In particular embodiments, the cutting edge comprises a so-called "inclined portion" forming an obtuse or acute angle with the axis of rotation of the tool.

[0024] In particular embodiments, the cutting edge comprises a so-called “straight portion” portion parallel with the axis of rotation of the tool.

[0025] In particular embodiments, the cutting edge comprises a so-called “straight portion” portion forming a right angle with said axis.

[0026] In particular embodiments, the cutting edge has a profile adapted to generate a functional or decorative structuring of the machined surface.

According to yet another aspect, the present invention relates to an escape wheel, for example obtained by implementing the process for manufacturing an escape wheel as described above, comprising a hub connected to a rim by radial arms and teeth regularly distributed over the periphery of the rim, each of the teeth comprising a thinned end portion connected to the rim by an intermediate portion. The thinned end portion of each of the teeth has a reduced thickness compared to the thickness of the intermediate portion and has a surface of revolution, the surfaces of revolution of each of the teeth sharing the same axis of revolution.

[0028] Advantageously, the axis of revolution coincides with the axis of rotation of the escape wheel.

In particular embodiments, the invention may further comprise one or more of the following characteristics, taken in isolation or in all technically possible combinations.

In particular embodiments, the thinned end portion of each tooth comprises a bevel, the bevels being arranged such that they have inclined curvilinear surfaces respectively materializing portions of the same truncated cone.

[0031] In particular embodiments, the thinned end portion of each tooth comprises an end surface defining an impulse plane of the tooth, said end surface having the shape of a rectangular trapezium.

In particular embodiments, the thinned end portion of each tooth comprises a flat surface substantially parallel to a plane in which the escape wheel is inscribed, said flat surface being connected to the bevel.

In particular embodiments, the thinned end portion of each tooth comprises a surface of revolution and a flat surface substantially parallel to a plane in which the escape wheel is inscribed, the surfaces of revolution being arranged such that they respectively materialize portions of the same cylinder of revolution.

[0034] In particular embodiments, the surfaces of revolution and/or the flat surfaces of the teeth may have a surface state producing a lipophobic or lipophilic effect.

Brief description of figures

Other characteristics and advantages of the invention will appear on reading the following detailed description given by way of non-limiting example, with reference to the appended drawings in which: FIG. 1 represents a perspective view of an escape wheel according to an exemplary embodiment of the invention and a detail view of a tooth of this escape wheel; FIG. 2 represents a detail view of the escape wheel of FIG. 1; FIG. 3 represents a detail view of a tooth of an escape wheel according to another exemplary embodiment; FIG. 4 represents a detail view of a tooth of an escape wheel according to yet another exemplary embodiment; FIG. 5 represents a perspective view of a cutting tool intended for the production of an escape wheel according to the present invention; Figure 6 shows a bottom view of the tool of Figure 5.

Detailed description of the invention

[0036] Figure 1 shows an escape wheel 10 according to the present invention, conventionally comprising a hub 11 connected to a rim 12 by radial arms 13, and teeth 14 distributed regularly around the periphery of the rim 12 and extending in directions orthoradial with respect to an axis of rotation of the escape wheel 10.

In the present text, a plane P (not shown in the figures) is defined in which the escapement wheel 10 is inscribed, the plane P being perpendicular to the axis of rotation of said escapement wheel 10. Furthermore, the term "thickness" used in the rest of the text refers to a dimension considered in a direction parallel to the axis of rotation of the escape wheel 10.

As shown in the detail view of Figure 1, each of the teeth 14 has a thinned end portion 140 connected to the rim 12 by an intermediate portion 120. Advantageously, the thinned end portion 140 of each of the teeth 14 has a reduced thickness compared to the thickness of the intermediate portion 120.

[0039] Each tooth 14 comprises an end surface 141 at the free end of the thinned end portion 140, said end surface 141 defining an impulse plane of the tooth 14. 'Impulse' is known to those skilled in the art to define a surface intended to come into contact with a pallet of an anchor in order to transmit forces to it.

In addition, the thinned end portion 140 of each of the teeth 14 has a surface of revolution 142 arranged so that all of the surfaces of revolution 142 of each of the teeth 14 share the same axis of revolution. The axis of revolution advantageously coincides with the axis of rotation of the escape wheel 10, as illustrated by FIG.

In particular, in the embodiment shown in Figures 1 and 2, the surface of revolution 142 of each tooth 14 forms a bevel 143, the bevels 143 being arranged such that they have curved curved surfaces materializing respectively portions of the same truncated cone, the axis of revolution of which coincides with the axis of rotation of the wheel. It is obvious that reference is made here by the mention of a truncated cone to a virtual geometric figure in which the inclined curvilinear surfaces are inscribed, the sole purpose of which is to specify the arrangement of the bevels 143.

As precisely shown in the detail view of Figure 1, the thinned end portion 140 of each tooth 14 may comprise, in addition to the surface of revolution 142, a flat surface 144 substantially parallel to the plane P. More precisely, the flat surface 144 is connected on the one hand to the surface of revolution 142 by a curvilinear edge materializing an arc of a circle whose center coincides with the axis of rotation of the escape wheel 10, and on the other hand, at the end surface 141, by an edge perpendicular to the orthoradial direction of the tooth 14, opposite to the curvilinear edge.

[0043] Alternatively to the bevels 143, in an exemplary embodiment shown in the detail view of Figure 3, the surfaces of revolution 142 can be arranged such that they respectively materialize portions of the same cylinder of revolution whose the axis of revolution coincides with the axis of rotation of the escape wheel 10.

In other words, the surface of revolution 142 is orthogonal to the plane P and not inclined, unlike the embodiment shown in Figures 1 and 2.

In yet another exemplary embodiment of the invention shown in Figure 4, each thinned end portion 140 has only one surface of revolution 142 formed by a bevel 143. Said thinned end portions 140 do not therefore have more flat surface 144 substantially parallel to the plane P.

The bevels 143 of the set of teeth 14 have inclined curvilinear surfaces materializing respectively portions of the same truncated cone whose axis of revolution coincides with the axis of rotation of the wheel.

The inclined curvilinear surface of each bevel 143 intersects with the end surface 141, so that the latter has the shape of a rectangular trapezium. It is therefore understood here that the thickness of the free end of each tooth 14 is then variable.

Advantageously, the surfaces of revolution 142 and/or the flat surfaces 144 of the teeth 14 may have a surface condition producing a lipophobic or lipophilic effect.

According to another aspect, the present invention relates to a cutting tool 20 for machining an escape wheel blank to obtain an escape wheel 10 as described above.

The cutting tool 20 is in the form of a cutter intended to be driven in rotation. As shown in Figure 5 in an embodiment of the invention, the cutting tool 20 comprises a substantially cylindrical body 21 comprising a first end by which it is intended to be fixed to a tool holder, and a second end opposite the first end. The body 21 of the cutting tool 20 extends along a longitudinal axis coinciding with its axis of rotation.

The body 21 of the cutting tool 20 carries at its second end at least one cutting tooth 22, the latter extending beyond said second end.

In the embodiment shown in Figures 5 and 6, the tool has two cutting teeth 22, each of which has a cutting edge 220 extending in a diametral plane of the body 21 of the cutting tool. cup 20.

Specifically, as shown in particular in Figure 6, the two cutting teeth 22 are diametrically opposed and are arranged one and the other respectively on either side of a diametral plane of the body 21 of the cutting tool 20. In other words, the two cutting teeth 22 are identical and are arranged relative to each other according to a central symmetry whose axis coincides with the axis of rotation of the cutting tool 20.

The cutting edge 220 of each cutting tooth 22 has a portion adapted to generate, on a workpiece, a surface of revolution whose axis of revolution is coaxial with the axis of rotation of the tool. .

More specifically, said portion is called "inclined portion" 221 and forms an obtuse or acute angle with the axis of rotation of the tool.

[0056] Figure 5, in particular, illustrates cutting edges 220 whose inclined portion 221 is inclined towards the body 21 of the cutting tool 20. In other words, the distance separating the inclined portions 221 of the two cutting edges 220 from each other increases as the edges move away from the second end of the body 21 of the cutting tool 20.

This characteristic makes it possible to be able to perform, during machining, a removal of material on the teeth 14 of an escapement wheel blank 10 one in order to generate a surface of revolution 142 in the shape of a bevel 143 as previously described and as illustrated in the detail views of Figure 1 and Figure 4. During this removal of material, the body 21 of the cutting tool 20 is arranged coaxially to the escape wheel blank as described in more detail below.

Alternatively, the cutting edge 220 may comprise a so-called "straight portion" portion parallel with the axis of rotation of the tool, not shown in the figures. The straight portion is advantageously adapted to generate on each of the teeth 14 of the escapement wheel, during machining, by the rotation of the cutting tool 20 around its axis of rotation, a surface of revolution 142, all of the surfaces of revolution 142 being representative of a portion of the same cylinder.

The cutting edge 220 may comprise, in addition to the inclined portion 221 or the straight portion, a so-called "straight portion" portion 222 forming a right angle with the axis of rotation of the cutting tool 20. The straight portion 222 is advantageously arranged at the end of each cutting tooth 22, and is farther from the axis of rotation of the tool than is the inclined portion 221 or the straight portion 222.

[0060] Advantageously, the straight portion 222 allows the realization of the flat surface 144 of the thinned end portion 140 described previously.

In addition, the inclined portion 221 or the rectilinear portion, and/or the straight portion 222, can have a profile adapted to generate a functional or decorative structuring of the surfaces of revolution 142 and/or on the flat surfaces 144 of the teeth. 14 of the escape wheel 10.

The profile may in particular comprise a succession of peaks and valleys.

[0063] The terms "functional structuring" here refer to a surface condition allowing the machined surfaces to exhibit a lipophobic or lipophilic effect.

[0064] In a manner known per se to those skilled in the art, the cutting teeth 22 may comprise clearance angles and are made of any suitable material, such as polycrystalline cubic boron nitride, monocrystalline or polycrystalline diamond, or a hard metal, or a composite with a metal matrix, for example tungsten carbide-cobalt or tungsten carbide-nickel, on which is for example deposited a suitable coating, such as a polycrystalline diamond coating, in "DLC" ( for „Diamondlike carbon“), titanium nitride, titanium carbide, etc.

The present invention also relates, according to another aspect, to a method of manufacturing an escape wheel as described previously.

[0066] This manufacturing method comprises a preliminary step of producing an escape wheel blank comprising a rim 12, a hub 11 connected to the rim 12 by radial arms 13 and teeth 14 regularly distributed over the periphery of the the serge 12.

[0067] At the end of this step, the escape wheel blank conforms to a conventional escape wheel, that is to say an escape wheel of the state of the art. Furthermore, during this preliminary step, it is possible to obtain an escape wheel blank by any method known to those skilled in the art, for example by cutting and cutting.

However, it is advantageous to obtain an escape wheel blank by the LIGA process for reasons discussed in detail below.

The next step consists of a step of machining, simultaneously, a reduction in section of the free end of each tooth 14, by a cutting tool 20 as described above and aligned coaxially with the escapement wheel blank, so as to obtain for each of the teeth 14, a thinned end portion 140 Thus, at the end of the implementation of the method, an escapement wheel 10 as described previously is obtained

[0070] 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 coincident. Also, the section reduction corresponds to a reduction in the thickness of the teeth 14 of the escape wheel blank

The machining step can be carried out such that the machined section reduction comprises a thinned end portion 140 in the shape of a surface of revolution 142 forming a bevel 143.

Alternatively, the machining step can be carried out such that the machined section reduction includes a thinned end portion 140 in the shape of a surface of revolution 142 orthogonal to the plane P.

[0073] In addition, the machining step can be carried out such that the machined section reduction comprises a thinned end portion 140 formed by a flat surface 144 substantially parallel to the plane P in which the wheel is inscribed. 'exhaust.

In another example of implementation of the method, the machining step can be carried out such that the machined section reduction comprises a thinned end portion 140 formed only by a bevel 143.

The machining step is advantageously carried out by milling, and it includes the successive operations of: positioning of the cutting tool 20 so that its axis of rotation coincides with the axis of rotation of the escape wheel blank; guiding the cutting tool 20 in translation towards the escape wheel blank in a direction coaxial with the axis of rotation of the escape wheel blank, and cutting off part of the end of the each tooth 14 of the escape wheel blank so as to reduce the thickness of said part, in a single cutting operation; this operation makes it possible to obtain the thinned end portions of each tooth 14; cutting tool clearance 20.

[0076] Thanks to the particular positioning of the cutting tool 20 with respect to the escapement wheel blank, the thinned end portions obtained following the cutting operation, on the one hand, are identical for the all of the teeth 14 of said escape wheel, and on the other hand, are obtained in a single machining operation.

Advantageously, if the escape wheel blank is obtained by a LIGA process, it is made from among a plurality of other escape wheel blanks distributed precisely on a substrate. Said substrate comprises optical markers arranged precisely with respect to the escape wheel blanks and adapted to be read by optical sensors so as to indicate the precise position of each of said blanks to the cutting tool 20. Thus, by being made optically, the operation of positioning the cutting tool 20 can be carried out quickly and precisely for each of the escape wheel blanks to be machined.

Furthermore, alternatively or in addition, during the operations of guiding the cutting or cutting tool 20, the method may comprise an operation of optical verification of the position of the cutting tool with respect to the escape wheel blank to be machined or machined, in order to correct the position of the cutting tool 20 if necessary.

Claims (18)

1. Method for manufacturing an escape wheel (10) characterized in that it comprises steps of: – production of an escape 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) , – machining, simultaneously, of a reduction in section of the free end of each tooth (14), by a cutting tool (20) aligned coaxially with the escape wheel blank. 2. Method according to claim 1, in which the section reduction is formed by a thinned end portion (140) comprising a bevel (143). 3. Method according to claim 1, in which the machined section reduction comprises a thinned end portion (140) in the shape of a surface of revolution (142) orthogonal to a plane in which the wheel blank is inscribed. exhaust. 4. Method according to one of claims 2 or 3, wherein the section reduction is formed by a thinned end portion (140) having a flat surface (144) substantially parallel to a plane in which the blank is inscribed. escape wheel. 5. Method according to one of claims 1 to 4, in which the step of producing the blank of an escape wheel is carried out by the LIGA method. 6. Method according to one of claims 1 to 5, wherein the machining step is performed by milling. 7. Method according to one of claims 1 to 6, in which the machining step comprises the successive operations of: – positioning of the cutting tool (20) so that its axis of rotation coincides with the axis of rotation of the escape wheel blank; – guiding the cutting tool (20) in translation towards the escape wheel blank in a direction coaxial with the axis of rotation of the escape wheel blank, and cutting out part of the the end of each tooth (14) of the escape wheel blank so as to generate a thinned end portion (140), in a single cutting operation; – release of the tool. 8. Cutting tool (20) for implementing a method of manufacturing an escapement wheel (10) according to one of claims 1 to 7, characterized in that it comprises a body (21 ) substantially cylindrical intended to be driven in rotation and comprising at one of its ends at least one cutting tooth (22) having a cutting edge (220) extending in a diametral plane of the body (21), said edge cutting tool (220) having a portion adapted to generate, on a workpiece, at least one surface of revolution (142) whose axis of revolution is coaxial with the axis of rotation of the tool. 9. Cutting tool (20) according to claim 8, in which the cutting edge (220) comprises a so-called “inclined portion” portion (221) forming an obtuse or acute angle with the axis of rotation of the tool . 10. Cutting tool (20) according to claim 8, in which the cutting edge (220) comprises a so-called “straight portion” portion parallel with the axis of rotation of the tool. 11. Cutting tool (20) according to one of claims 9 or 10, wherein the cutting edge (220) comprises a so-called “straight portion” portion (222) forming a right angle with said axis. 12. Cutting tool (20) according to one of claims 8 to 11, wherein the cutting edge (220) has a profile adapted to generate a functional or decorative structuring of the machined surface. 13. Escapement wheel (10) obtained by implementing a method for manufacturing an escapement wheel (10) according to one of claims 1 to 7, comprising a hub (11) connected to a serge (12) by radial arms (13) and teeth (14) regularly distributed over the periphery of the serge (12), each of the teeth (14) comprising a thinned end portion (140) connected to the serge ( 12) by an intermediate portion (120), said escapement wheel (10) being characterized in that the thinned end portion (140) of each of the teeth (14) has a reduced thickness compared to the thickness of the intermediate portion (120) and comprises a surface of revolution (142), the surfaces of revolution (142) of each of the teeth (14) sharing the same axis of revolution. 14. Escape wheel (10) according to claim 12, wherein the thinned end portion (140) of each tooth (14) has a bevel (143), the bevels (143) being arranged such that they have inclined curvilinear surfaces materializing respectively portions of the same truncated cone. 15. Escapement wheel (10) according to claim 14, in which the tapered end portion (140) of each tooth (14) comprises an end surface (141) defining an impulse plane of the tooth, said end surface (141) having a shape of a rectangular trapezoid. 16. Escape wheel (10) according to claim 14, in which the thinned end portion (140) of each tooth (14) comprises a flat surface (144) substantially parallel to a plane in which the escape wheel is inscribed. exhaust (10), said planar surface (144) being connected to the bevel (143). 17. Escape wheel (10) according to claim 13, in which the tapered end portion (140) of each tooth (14) has a surface of revolution (142) and a flat surface (144) substantially parallel to a plane in which the escape wheel (10) is inscribed, the surfaces of revolution (142) being arranged in such a way that they respectively materialize portions of the same cylinder of revolution. 18. Escapement wheel (10) according to one of claims 16 or 17, in which the surfaces of revolution (142) and/or the flat surfaces (144) of the teeth (14) may have a surface finish producing a lipophobic or lipophilic effect.