Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/02—Shock-damping bearings
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/004—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor characterised by the material used
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/004—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor characterised by the material used
  • G04B31/016—Plastic bearings
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B31/00—Bearings; Point suspensions or counter-point suspensions; Pivot bearings; Single parts therefor
  • G04B31/06—Manufacture or mounting processes

Definitions

• the present invention relates to the field of anti-shock bearings (bearings with a shock-absorbing device) for a timepiece and their manufacturing processes.
• the invention relates to an anti-shock bearing intended to receive a pivot of the axis of the balance of a mechanical watch movement.
• Document CH 700 496 describes an anti-shock bearing constituted by monocrystalline silicon and comprising a central portion and elastic radial arms connecting this central portion to a peripheral annular portion.
• the central portion includes a flared hole in the form of a four-sided pyramid.
• a four-sided hole bottom is not optimal for the support of a pivot.
• this document provides an anisotropic wet etching. To do this, it is mentioned that the silicon substrate must be properly oriented to be able to machine this pyramidal hole. Then, to perform the machining of the remainder of the monolithic silicon part and in particular the elastic arms, this document proposes to use another machining technique, namely deep reactive ion etching (DRIE).
• DRIE deep reactive ion etching
• the present inventor has found that silicon does not allow the machining of a structure with walls substantially vertical and having a curvature by chemical etching in an acid bath.
• silicon does not allow the machining of a structure with walls substantially vertical and having a curvature by chemical etching in an acid bath.
• to obtain openings in a monocrystalline silicon wafer with vertical walls only specific orientations of the silicon crystal in this wafer are possible (not compatible with the orientation to obtain pyramidal holes).
• the possible directions for such vertical walls are limited and these vertical walls are formed only of flat surfaces.
• WO 2009/060074 discloses anti-shock bearings comprising a monolithic piece of silicon and a pierced stone associated therewith.
• This monolithic piece defines an elastic structure and a counter-pivot stone. It is made in a silicon wafer using the well-known methods of photolithography and etching.
• the monolithic parts may be made of silicon or of another preferably monocrystalline material that can be easily machined by photolithography and chemical etching techniques. No example other than silicon is given.
• silicon as mentioned above, if it is possible to obtain slots or openings with vertical walls, the designs are limited. In particular, all the designs shown in the figures of this document can not be obtained by a chemical etching of a silicon crystal wafer.
• the object of the present invention is to solve the problem of complex and expensive machining of monocrystalline crystal monobloc pieces, and to provide a shockproof bearing, formed by a one-piece piece defining an elastic structure and a central part in which a hole is machined. intended to receive a pivot of a rotating mobile, which can be machined industrially at relatively low cost while being of high quality.
• Another object of the invention is to provide a shockproof bearing of the type described above which has a blind hole whose shape is advantageous for ensuring proper centering of the axis of the rotating mobile pivoted in the blind hole and to minimize the friction.
• the invention also aims to provide a shockproof bearing that is aesthetic and has a particular recognizable appearance.
• the subject of the present invention is an anti-shock bearing for a timepiece comprising an elastic structure and a central part carried by this elastic structure, this central part having a blind hole intended to receive a pivot of a rotating mobile of the timepiece.
• the elastic structure and the central portion are formed by a single piece made of monocrystalline quartz and the blind hole has three oblique facets together defining a truncated or truncated trigonal pyramid.
• the one-piece piece is a perforated plate whose axis perpendicular to its two main faces is almost parallel to the optical axis of the single-crystal quartz.
• the present invention also relates to two main modes of implementation of a method of manufacturing a shockproof bearing whose elastic structure and a central part, carried by this elastic structure and having a blind hole, are made of monocrystalline quartz.
• the manufacturing method according to the invention makes it possible to obtain a high quality transparent shockproof bearing by a relatively inexpensive process which only requires machining in chemical baths.
• this method allows machining a blind hole for the bearing whose bottom is defined at least partially by a trigonal pyramid against which faces abuts the pivot of a rotating wheel.
• Such a hole blind allows to ensure a better centering of the rotating axis of the mobile and also to minimize friction.
• a transparent bearing also has a technical advantage in that it makes it possible to better check the presence of oil in the hole.
• FIG. 1 is a sectional view of an embodiment of an anti-shock bearing according to the invention.
• FIG. 2 is a top view of a monocrystalline quartz perforated disk forming the shock bearing of Figure 1;
• FIG. 3 is a schematic perspective view of a monocrystalline quartz crystal in which is cut a plate used to make the perforated disk of Figure 2;
• FIG. 4A is a section of a quartz plate covered on its two main faces with a mask selected to resist a quartz etching bath;
• FIG. 4B is a schematic section of the plate of Figure 4A after machining in a chemical bath provided for anisotropic attack of quartz;
• FIG. 5 is a plan view of a first variant of the blind hole obtained in the quartz plate machined according to the method of the invention.
• FIG. 6 is a plan view of a second variant of the blind hole obtained in the quartz plate machined according to the method of the invention
• FIG. 7 is a sectional view along the line VII-VII of FIG. 6, for a variant where it differs from that of FIG. 6 only in that the initial portion of the blind hole does not have a vertical wall; but has a steep slope; and
• FIGS. 8A and 8B are sections corresponding to FIGS. 4A and 4B with a thicker quartz plate and a larger diameter blind hole whose shape is similar to the blind hole shown in FIGS. 6 and 7.
• This shockproof bearing is arranged in a bridge or plate 4 of a timepiece and consists of a plate 6 of monocrystalline quartz (this plate defining a pellet or a disc) and a base 8 which has a housing for the wafer 6.
• This wafer comprises an elastic structure 10, formed by the substantially circular slots 12 machined in this wafer, and a central portion 14 carried by this elastic structure and having a blind hole 16 for receiving a pivot of a mobile rotating (not shown) of the watch movement.
• the substantially arcuate slots define between them spiral elastic arms connecting the central portion to the peripheral region of the wafer 6.
• This elastic structure and this central portion are formed by a single piece consisting of monocrystalline quartz.
• an elastic structure at the periphery of the central portion 14, the latter can undergo displacements in the plane of the wafer 6 and also, to a certain extent, vertically.
• a slot between the elastic structure 10 and the bottom of the housing of the base 8 is preferably provided.
• Bearing 2 defines a suspended shock bearing.
• the base includes an opening for the passage of the axis of a mobile rotating and serves as a stop in the event of an axial and / or violent vertical impact. Note that the stop may be arranged in various ways and that, in a variant, the wafer 6 is directly arranged in the bridge or plate 4 without intermediate element.
• the elastic structure may have many variations in the design in the plane of the wafer 6. It is sufficient that the central portion 14 is elastically connected to the peripheral portion of the base 8. However, the arrangement of spiral arms The nested type shown in FIG. 2 is advantageous because the length of the elastic arms is increased relative to a configuration with radial arms. To do this, the selection of a quartz wafer is remarkable because such a design can be obtained by a method of chemical etching in a bath, a process which will be explained later.
• the blind hole 16, machined in the lower face of the central portion 14, has three oblique facets 40A, 40B, 40C together defining at least partially a trigonal pyramid (see Figure 5).
• each of the three facets defines an angle of about 40 ° with the central axis Z of the blind hole, that is to say that the median line 42 of each of these facets defines an angle of about 40.degree. ° with the central axis of the blind hole.
• the bottom of the blind hole, especially when the diameter of the hole becomes larger, may still have other facets (see Figure 6).
• These different facets come from the chemical attack of quartz provided in the manufacturing process according to the invention described below.
• the blind hole also has a substantially vertical side wall in its initial part (see Figure 7).
• the three facets do not extend to the outer face of the one-piece piece where the blind hole opens and the side surface of the blind hole between the outer face and the three facets has one or more steeper slopes than that of these three facets.
• the slope or slopes defined by the lateral surface of the blind hole is / are less than twenty degrees (20 °) relative to the central axis of this blind hole.
• the wafer 6 made of monocrystalline quartz is selected so that the Z axis, perpendicular to its two main faces, is approximately the optical axis of the single-crystal quartz.
• Figure 3 shows schematically a quartz crystal 18 and a slice 6A which is cut in this crystal quartz to manufacture a plate in which is then machined the plate 6 according to the invention.
• a shockproof bearing of the type comprising an elastic structure and a central portion carried by this elastic structure and having a blind hole for receiving a pivot of a mobile turning of the timepiece, this elastic structure and this central portion being formed by a single piece, the following steps are provided:
• the speed at which the hole is formed along its central axis is less than the machining speed, according to the direction of this axis of the elastic structure so that it is possible to simultaneously obtain the blind hole and the elastic structure by a chemical attack only from the first face.
• the machined elastic structure has a design with curved slots and / or openings whose edges have at least partially curved lines; which makes it possible to optimize this elastic structure as explained previously.
• the normal to the two main faces of the quartz wafer has an angle of about two degrees (2 °) with the optical axis (birefringence axis) of the crystal structure of the single crystal quartz.
• the quartz etching bath contains in particular fluoridic acid (HF). It also contains ammonium fluoride (NH 4 F).
• a photosensitive layer 22, respectively 28 is deposited on a metal layer 20, respectively 26, for example a chromium-gold layer (Cr-Au). Each photosensitive layer is then selectively illuminated and developed to obtain apertures corresponding to the intended mask.
• the photosensitive layer 22 has openings 24A for the elastic structure and an opening 25 for the blind hole; while the photosensitive layer 28 only has openings 24B for the elastic structure 10.
• the wafer 6A is immersed in a chemical bath suitable for etching the metal layers 20 and 26 so as to define the two corresponding masks (same references as the metal layers) for the subsequent localized attack of the quartz.
• the wafer 6A provided with its two masks is immersed in a chemical bath selected to perform a strongly anisotropic etching of the monocrystalline quartz by favoring an attack substantially along the optical axis Z.
• a perforated wafer 6 is obtained with circular slots 12 with substantially vertical walls.
• a blind hole 16A whose bottom has inclined facets as explained above (the symmetrical V profile in the section of Figure 4B is schematic, since in a cross section, it does not cross generally two facets of the pyramid at the same inclination).
• the bottom of the hole is formed only by a trigonal pyramid.
• the wafer 6 has a thickness of about 200 microns and the diameter of the blind hole is 100 or 120 microns.
• this method comprises the following steps:
• step B) Formation of a first initial mask on the first face of the monocrystalline quartz wafer, this first initial mask being structured by photolithography so as to define on the first face the contour of the elastic structure but not the contour of the blind hole intended to receive the pivot of a rotating mobile;
• step E Final machining of the elastic structure and simultaneously machining of the blind hole, defined by the first final mask structured in step D), in the monocrystalline quartz wafer by introducing this wafer again into the chemical etching bath.
• FIGS. 8A and 8B A preferred variant of this second mode of implementation of the method of the invention is shown schematically in FIGS. 8A and 8B.
• it is provided, before step C), to form a second mask on the second face of the monocrystalline quartz wafer, this second mask being structured by photolithography so as to define the contour of the elastic structure on this second face.
• This variant allows an attack on both sides of the wafer 36A as shown in Figure 8A.
• FIG. 8A is shown schematically a section of a monocrystalline quartz plate 36A as it is after step C) of the method according to the variant described here and after illumination and development of the photosensitive layer 23 to obtain the opening 25A in this layer making it possible to make the hole 25 (FIG. 8B) in the initial mask 21 A so as to obtain the final mask 21.
• This final mask makes it possible to machine the blind hole 16B in the terminal phase of the machining the elastic structure 10 to obtain the perforated plate 36 shown in Figure 8B.
• the second mask 27 has been structured using the photosensitive layer 29. engrave the masks 21 A and 27, the photosensitive layers 23 and 29 are respectively structured by photolithography and then respectively have openings 24A and 24B corresponding to the elastic structure 10 provided.
• the wafer 36A is introduced into a chemical bath of anisotropic etching of the quartz for a first phase or period. After removing the wafer from the bath, the elastic structure is partially machined as shown in Figure 8A. Grooves 32 and 33 are obtained on both sides of the wafer 36A.
• the photosensitive layer 23, having served for the partial structuring of the first initial mask 21 A to define the elastic structure, is illuminated to produce a hole 25A in this photosensitive layer. corresponding to the blind hole provided ( Figure 8A). It should be noted that the development of the photosensitive layer 23 to obtain the hole 25A can take place before or after the step C).
• the structuring of the first mask is thus carried out here in two phases in a chemical etching bath selected to attack the metal layer deposited on the monocrystalline quartz wafer and forming this first mask.
• the second embodiment of the method according to the invention makes it possible to determine two different time periods for the machining of the elastic structure and the machining of the blind hole in an anisotropic etching bath of the monocrystalline quartz. This makes it possible to optimize the etching time for the elastic structure and for the blind hole.
• the monocrystalline quartz wafer has a thickness of 300 microns and the diameter of the blind hole is about 200 microns.
• the first phase or etching period of the elastic structure lasts for example about two hours (2h) and the second phase or etching period of this elastic structure and the blind hole also lasts example about two hours.
• the depth of the blind hole is for example between 100 and 150 microns.
• the blind hole 16B has in its initial part a substantially vertical wall 44.
• the pivot 50 of the axis of the mobile inserted in the blind hole is preferably configured so that the bearing points of this pivot against the bottom of the blind hole are located in areas 46 of the three facets of the main trigonal pyramid which present substantially an angle of 40 ° with the axis of rotation Z of the pivot 50.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Micromachines (AREA)
• Sliding-Contact Bearings (AREA)

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• 2012
  • 2012-12-07 JP JP2014545136A patent/JP5848461B2/ja active Active
  • 2012-12-07 US US14/364,550 patent/US9292005B2/en active Active
  • 2012-12-07 RU RU2014128595/28A patent/RU2603236C2/ru not_active IP Right Cessation
  • 2012-12-07 CH CH02729/12A patent/CH705861A2/fr not_active Application Discontinuation
  • 2012-12-07 WO PCT/EP2012/005050 patent/WO2013087173A1/fr active Application Filing
  • 2012-12-07 EP EP12806345.0A patent/EP2791739B1/de active Active
  • 2012-12-07 CN CN201280061202.6A patent/CN103988133B/zh active Active
• 2015
  • 2015-02-04 HK HK15101202.5A patent/HK1200927A1/xx unknown

Non-Patent Citations (1)

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