Flexible timepiece guidance

Abstract

A device for elastic guidance in rotation for a timepiece mechanism allows rotation of one element relative to another element about an axis of rotation Z defining an axial direction. The device includes construction blades that each includes an assembly fixing part having a body and a functional part extending from the body as far as one end. The assembly fixing part and the functional part are separated by at least one slot in at least two extensions which are elastically connected and extend in a radial direction transverse to the axial direction. The device also includes anchorage zones which are disposed at opposite axial ends of the flexible guidance device, and configured to be fixed to the elements.

Claims

1. A device for elastic guidance in rotation for a timepiece mechanism allowing rotation of one element relative to another element about an axis of rotation Z defining an axial direction, the device comprising: construction blades, each construction blade comprises an assembly fixing part comprising a body and a functional part extending from the body as far as one end, the assembly fixing part and the functional part being separated by at least one slot in at least two extensions which are elastically connected and extend in a radial direction transverse to the axial direction, the device comprising furthermore anchorage zones which are disposed at opposite axial ends of the flexible guidance device, and configured to be fixed to said elements, wherein the assembly fixing part of each of the construction blades comprises a cavity or an assembly recess and an assembly extension which intersect and which fit together in a radial direction in order to be locked together.

2. The device according to claim 1, wherein the body represents a central part of the device encompassing an axis of rotation of the device.

3. The device according to claim 1, wherein one of the construction blades includes a slot forming the assembly cavity, the functional part of the other blade being inserted in the slot until the body of the latter abuts against the body of the former.

4. The device according to claim 1, wherein the construction blades are made of a material based on silicon, nickel, nickel-phosphorus or an amorphous metal.

5. The device according to claim 1, wherein each construction blade is formed by deposition or etching processes in an essentially bi-dimensional process.

6. The device according to claim 1, wherein the construction blades are manufactured according to an electroforming process of the silicon on insulator SOI type or according to a LIGA process.

7. The device according to claim 1, wherein each construction blade comprises a functional part which extends in a radial direction on both sides of the body, this body forming a central part for rotation relative to the ends of the blades.

8. The device according to claim 1, wherein the ends of the blades are free.

9. The device according to claim 1, wherein it is configured as a spring and support for an oscillator or an element pivoting about the axis of rotation Z, without requiring another pivot or support for the pivoting element.

10. The device according to claim 1, wherein each of the construction blades comprises only one functional part which extends from the assembly fixing part, forming a V configuration.

11. The device according to claim 1, wherein the construction blades include a plurality of slots spaced in the axial direction in order to form a plurality of functional extensions which have elastic portions.

12. The device according to claim 1, wherein each construction blade forms a monolithic structure.

13. The device according to claim 1, wherein it is formed from two construction blades.

14. The device according to claim 1, wherein the construction blades are formed from a wafer of monocrystalline silicon.

15. The device according to claim 14, wherein said wafer comprises two layers of equal or different thicknesses, welded or glued together, the construction blade having parts with a thickness corresponding to the thickness of one of the layers and parts with a thickness corresponding to the thickness of the two layers.

16. A watch movement comprising: a device for elastic guidance in rotation for a timepiece mechanism allowing rotation of one element relative to another element about an axis of rotation Z defining an axial direction, comprising construction blades, each construction blade comprises an assembly fixing part comprising a body and a functional part extending from the body as far as one end, the assembly fixing part and the functional part being separated by at least one slot in at least two extensions which are elastically connected and extend in a radial direction transverse to the axial direction, the device comprising furthermore anchorage zones which are disposed at opposite axial ends of the flexible guidance device, and configured to be fixed to said elements, wherein the assembly fixing part of each of the construction blades comprises a cavity or an assembly recess and an assembly extension which intersect and which fit together in a radial direction in order to be locked together.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other aims and advantageous aspects of the invention will appear upon reading the claims and also the detailed description of embodiments hereafter, and annexed drawings, in which:

(2) FIG. 1A is a schematic perspective view of a device for elastic guidance in rotation for a timepiece mechanism, according to an embodiment of the invention;

(3) FIG. 1B is a view of the embodiment of FIG. 1A in the course of assembly;

(4) FIG. 1C is a schematic drawing illustrating a function of the guidance device in a mechanism;

(5) FIGS. 2A, 2B are schematic exploded perspective views of a device for elastic guidance in rotation for a timepiece mechanism, according to a second embodiment of the invention;

(6) FIG. 2C is a perspective view of the assembled device of FIG. 2A;

(7) FIG. 3 is a schematic perspective view of a device for elastic guidance in rotation for a timepiece mechanism, according to a third embodiment of the invention;

(8) FIG. 4A is an exploded perspective view of a device for elastic guidance in rotation for a timepiece mechanism, according to a fourth embodiment of the invention;

(9) FIGS. 4B and 4C are perspective views of the fourth embodiment in neutral and pivoted positions respectively.

(10) Referring to the Figures, a device for elastic guidance in rotation 2 comprises construction blades 4a, 4b configured to be assembled and fixed together in order to form the device for elastic guidance in rotation. Each construction blade includes at least one slot 12 separating the construction blade into at least two parts which are coupled elastically and moveable. The device for elastic guidance allows rotation about an axis of rotation Z, of an element 1 (for example a balance wheel or the pallets) relative to another element 3 (for example a frame), the elements fixed to the device for elastic guidance at the anchorage zones 9, 11 respectively. The anchorage zones 9, 11 are disposed at opposite axial ends of the device for flexible guidance, the axial direction being defined by the axis of rotation Z.

(11) The construction blades 4a, 4b comprise an assembly fixing part 6, and a functional part 10 extending from the assembly fixing part as far as a free end 8, the assembly fixing part 6 and the functional part 10 being separated by at least one slot 12 in at least two extensions 17 which are elastically connected and extend in a radial direction X, Y transverse to the axial direction Z.

(12) The device can have construction blades with functional parts on both sides of the assembly fixing part 6 as illustrated in FIGS. 1A and 1B, or with a functional part extending only on one side of the assembly fixing part 6 as illustrated in FIGS. 2A to 2C. The assembly fixing part 6 can form a body 13 which in certain embodiments or variants represents the central part of the device encompassing the axis of rotation Z of the device.

(13) In the Figures, the axial direction is represented by the axis Z which is parallel to the axis of rotation of the device for elastic guidance in rotation. The radial direction is illustrated by the axes X and Y situated in a plane orthogonal to the orthogonal direction Z. In flexible guidance applications, having great rigidity in the axial direction and great flexibility in rotation is sought.

(14) The assembly fixing part comprises a body 13a, 13b, the body 13b of at least one of the construction blades 4b including a cavity or an assembly recess 14, configured for insertion in a radial direction of one part of the other construction blade 4a so that, in the assembly fixing part 6, the construction blades 4a, 4b intersect. This intersection of the assembly fixing parts of the two construction blades 4a, 4b is very advantageous since it makes it possible to manufacture the construction blades independently in an optimum manner in order to define the thicknesses of the blade whilst having, once assembled, a device for elastic guidance in rotation with great rigidity in the axial direction Z. In fact, each construction blade 4a, 4b can be formed by known processes of deposition or etching, for example through a photolithographic mask, of silicon or of other materials in an essentially bi-dimensional process. A bi-dimensional process makes it possible to obtain precise thicknesses over the length of the blade and shapes represented by various thicknesses over the length of the blade which are easy to manufacture with great precision via masks defined by simple photolithographic processes. The direction of increase or reduction of the blades can be effected solely according to an elastic displacement direction Tx, Ty orthogonal to the radial direction X, Y, such a process being simple, economical and allowing easy control of the thicknesses in order to obtain blades which are rigid in the axial direction Z but have elasticity which is precise and well controlled with a uniform, robust structure.

(15) According to an advantageous embodiment of the invention, the construction blades are formed from a sheet cut out in a block of material, in particular a crystalline material, the sheet being commonly termed wafer. The block of material can in fact be a block of monocrystalline silicon or a block of another material used in the wafers for integrated circuits or micromechanics industry. Etching of the construction blades is effected in a direction orthogonal to the main plane of the wafer (which is parallel to the cut surface of the wafer). The construction blades are orientated such that the axis of rotation of the flexible guidance, which extends in the axial direction Z, is parallel to the main plane of the construction blades. The properties and elastic characteristics of the construction blades in their elastic displacement direction Tx, Ty are consequently dependent upon the thicknesses in the direction orthogonal to the main plane, these thicknesses being able to be well controlled in economic manufacturing processes.

(16) In one embodiment, the wafer can comprise two layers of equal or different thicknesses, welded or glued together, this making it possible, in an etching process, to obtain precise thicknesses corresponding to the thicknesses of one or other of the layers. In fact, the interface between the two layers defines a threshold which makes it possible to stop precisely the reduction of material at the level of the interface during the etching process. The precision in formation of the thicknesses is an advantage for controlling well the elastic properties and the resistance of the construction blades. In this embodiment, it is possible to manufacture, economically and with precision, construction blades with two levels, having parts with a thickness corresponding to the thickness of one or other of the layers and parts with a thickness corresponding to the thickness of the two layers.

(17) The construction blades can also comprise sacrificial structures which assist assembly.

(18) In the embodiment illustrated in FIGS. 1B and 1A, one of the construction blades 4b includes a slot 14 forming the assembly cavity, the functional part 10 of the other blade 4a being inserted in the slot 14 until the body 13a of the latter abuts against the body 13b of the construction blade 4b. In the illustrated variant, each construction blade 4a, 4b comprises a functional part 10 which extends in a radial direction on both sides of the body 13a, 13b, this body forming a central part of rotation relative to the ends 8 of the blades. In this embodiment, the ends 8 of the blades are free. However, in some variants, the ends 8 can be fixed to a balance wheel or to a frame or to another structure.

(19) The body 13a, 13b is fixed in the anchorage zones 9, 11 on both sides of the slot 12 to two elements, one being moveable relative to the other. For example, one of the anchorage zones 9 can be fixed to a frame, and the other of the anchorage zones to an element which pivots relative to the frame. In this embodiment, the device can serve as spring and support for an oscillator or element pivoting about the axis of rotation Z, without requiring another pivot or support for the pivoting element. The device can however be used in other configurations, for example the central body 13 can be fixed to two moveable elements at the anchorage zones 9, 11, the ends 8 of the blades being coupled to a frame.

(20) Referring to the embodiment illustrated in FIGS. 2A to 2C, the construction blades 4a, 4b each comprise only one functional extension part 10 which extends from the assembly fixing part 6 forming a V configuration. The axial ends 9, 11 of the assembly fixing part 6 can be coupled to elements or structures which are moveable relative to each other. The assembly fixing part 6 of each of the construction blades 4a, 4b comprises an assembly cavity 14 and an assembly extension 15 which intersect and which fit together in order to be locked together. The two construction blades can be locked together by a welding or soldering process, by an adhesive, or by a clamp or other means of mechanical clipping. The construction blades 4a, 4b can include a plurality of slots 12 spaced in the axial direction Z, as illustrated in FIG. 2C, FIG. 3 and FIGS. 4A to 4C in order to form a plurality of functional extension parts having elastic parts 16. This makes it possible to increase the amplitude of the angle of elastic rotation between the anchor zones 9, 11.

(21) The construction blades can have complex shapes whilst being easy to manufacture with precision, by varying the thickness in the etching, respectively deposition, direction (direction T), for example as illustrated in FIGS. 2A to 2C with a functional part comprising elastic portions 16 and a rigid portion 18 interposed between the elastic portions and also a radial slot 12 or several radial slots 12. Another example is illustrated in FIGS. 4A to 4C where the blades comprise elastic portions 16 which extend essentially over the entire length of the blade and are connected at their ends 8 to rigid portions 18, the rigid portions extending from the ends 8 to the pivot axis Z. The elastic portions have thinner walls than the walls of the rigid portions.

(22) The elasticity in the direction of rotation (direction T) of the construction blades can be controlled by varying the length of the rigid portions 18, respectively the length of the elastic portions 16, and also by varying the number of radial extensions, respectively of slots, stacked in the axial direction. This likewise makes it possible to control the distribution of the masses and finally not only the spring constant but likewise the resonance frequencies, in particular of the first order of the elastic system.

(23) One advantage of the invention is that the construction blades can be manufactured as structured pieces and in two levels: a first level which can be very fine, for example of the order of 10 m in order to fashion the flexible blades, and a thicker level, for example of the order of magnitude of 400 m, making it possible to produce rigid mountings, this giving essentially a planar part structured at two levels with slots. The assembly of two blades by intersection and fitting together is also very simple to effect.

(24) Flexible guidance according to the invention can be used for various applications, for example as guidance of the pallets in a watch, or as guidance of the balance wheel in a watch, the balance wheel no longer having a pivoting frictional axis nor a spiral, these two elements being replaced by the flexible guidance.

REFERENCE LIST

(25) 1 element (e.g. balance wheel) 2 device for elastic guidance in rotation 3 element (e.g. frame) 4a, 4b construction blades 6 assembly fixing part 13 body 14 cavity/assembly recess 15 assembly extension 8 free end 10 functional part 17 radial extension 16 elastic portion 18 rigid portion 12 radial slot 9, 11 anchorage zones Z axial direction/axis of rotation X, Y radial directions X-Y radial plane Z-X, Z-Y axial plane Tx, Ty directions of elastic displacement