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
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/045—Oscillators acting by spring tension with oscillating blade springs

Definitions

• the present invention relates to a flexible pivot oscillator intended to serve as a time base in a watch mechanism.
• a flexible pivot oscillator is an oscillator whose balance wheel is guided in rotation by an arrangement of elastic parts and not by a physical axis of rotation sliding in bearings. In addition to its function of guiding rotation, the flexible pivot exerts a restoring torque on the balance like the hairspring of a balance-spring oscillator.
• a flexible-pivot oscillator does not produce sharp friction during operation. It therefore has a better quality factor.
• the present invention relates more particularly to a flexible pivot oscillator whose arrangement of elastic parts comprises separate cross blades. Such blades extend in parallel planes and in different directions to intersect without contact.
• Separate cross-blade oscillators are described for example in patent applications EP 2911012, EP 2998800, WO 2016/096677, WO 2017/055983 and WO 2018/109584.
• the properties of a separated cross-blade oscillator are characterized in particular by the precision of its frequency, its quality factor, its insensitivity to gravity, its insensitivity to temperature, its isochronism and its resistance to shocks.
• the present invention aims to provide a watch oscillator with separated crossed blades, at least some of the aforementioned properties of which can be excellent.
• the subject of the invention is a horological oscillator with a flexible pivot comprising a support, a balance wheel and first and second elastic blades arranged to guide the balance wheel in rotation relative to the support around a virtual axis of rotation and to exert on the balance a return torque, the first and second elastic strips extending in parallel planes and crossing each other without contact, the balance having a rim of generally symmetrical shape with respect to the virtual axis of rotation and being assembled between an upper part and a lower part, the upper part comprising an upper stage of the support and the first elastic blade, the lower part comprising a lower stage of the support and the second elastic blade.
• the invention makes it possible to dissociate the inertia of the oscillator, provided essentially by the balance wheel, from the stiffness of the elastic blades and to adjust the inertia and the stiffness separately.
• the inertia can be adjusted in an easy and known manner via the attached balance, as for a standard balance, and the elastic blades can be made to the desired stiffness, without constraint of sizing to obtain the good stiffness/inertia compromise usually sought in standard flexible pivot oscillators.
• the materials of the pendulum and of the upper and lower parts can be different and each optimized for the function to be fulfilled.
• the geometric and structural characteristics of the oscillator according to the invention contribute to improving several of its properties, including insensitivity to gravity and temperature and shock resistance.
• FIG. 1 is a perspective view of a clock oscillator according to a particular embodiment of the invention.
• FIG. 2 is a perspective view of the same oscillator but some parts of which have been removed to lighten the drawing, this oscillator being shown here associated with fixed central stops;
• FIG. 3 is a perspective view of a balance of this oscillator
• FIG. 4 is an axial sectional view of this oscillator.
• a horological oscillator with a flexible pivot for a timepiece such as a wristwatch, a pocket watch or a pendant watch, comprises a support 1, a balance 2 and a flexible pivot 3 connecting support 1 to balance wheel 2.
• Support 1 is intended to be mounted on a fixed or mobile frame of the timepiece.
• the flexible pivot 3 comprises first and second elastic strips 4, 5 which are identical but extend in parallel planes and in different directions to intersect without contact. In plan view from above, the crossing point of the blades 4, 5 coincides with the geometric center of the balance 2.
• the crossing of the blades 4, 5 defines a virtual axis of rotation A of the balance 2 with respect to the support 1, axis of rotation which is perpendicular to the plane of the oscillator and of the balance 2.
• the flexible pivot 3 thus serves to suspend the balance 2 from the support 1, to guiding the balance 2 in rotation with respect to the support 1 around the virtual axis of rotation A and exerting on the balance 2 an elastic return torque tending to bring it back to a position of equilibrium with respect to the support 1 (the position shown in Figures 1 and 2).
• the oscillator according to the invention is not monolithic but formed of a stack of parts comprising an upper part 6, a lower part 7 and, between the two, the balance wheel 2.
• the upper part 6 comprises an upper stage 8 of the support 1, the first elastic blade 4 and an upper arm 9 connected to the upper stage 8 of the support 1 by the first elastic blade 4.
• the lower part 7 comprises a lower stage 10 of the support 1, the second elastic blade 5 and a lower arm 11 connected to the lower stage 10 of the support 1 by the second elastic blade 5.
• each of the upper and lower parts 6, 7 is monolithic.
• the material of these parts 6, 7 is chosen for its good elastic properties and for its ability to be micro-machined.
• each of these parts 6, 7 is made of silicon by DRIE at a single level, a technique relatively simple to implement and which makes it possible to achieve high precision.
• the silicon parts 6, 7 can be coated with a reinforcing layer, for example a layer of silicon oxide, making it possible to improve their mechanical strength.
• a layer of silicon oxide can also have a thickness chosen to make the frequency of the oscillator insensitive to a variation in temperature (typically 30°C).
• the balance 2 comprises a rim 12 and a diametral arm 13 which, in the example shown, is interrupted in its central part.
• the balance 2 can be made, in part at least, in a dense material such as beryllium copper, gold, platinum, nickel silver or other dense metal or alloy. It can thus have a small diameter for a given moment of inertia. In this way, friction with the air is reduced, which increases the quality factor.
• the serge 12 of the balance 2 can carry traditional flyweights 12a making it possible to adjust the inertia.
• the upper and lower stages 8, 10 of the support 1 are superimposed while being separated by a spacer 14, for example metallic, and are assembled by pins 15.
• the pins 15 pass through the elastic ends 16 of the upper and lower stages. 8, 10 and pass through holes in spacer 14. Stages 8, 10 are thus secured only by elastic tightening of pins 15.
• the holes in spacer 14 through which pins 15 pass have a diameter slightly larger than that of the pins 15 so as not to constrain the elastic blades 4, 5, which would modify their stiffness and therefore the frequency of the oscillator.
• the spacer 14 is immobilized with respect to the stages 8, 10 by gluing, brazing or welding to the pins 15 and/or to at least one of the stages 8, 10.
• the upper arm 9, the diametral arm 13 and the lower arm 11 are superimposed.
• pins 17 pass through the elastic ends 18 of the upper and lower arms 9, 11 and pass through holes 19 of the diametral arm 13.
• the upper and lower arms 9, 11 are thus made integral only by elastic tightening of the pins 17.
• the holes 19 of the diametral arm 13 through which the pins 17 pass have a slightly larger diameter than that of the pins 17 so as not to constrain the elastic blades 4, 5.
• the diametral arm 13 is immobilized with respect to the arms 9, 11 by gluing, brazing or welding to the pins 17 and/or to at least one of the arms 9, 11.
• the assembly of the upper arm 9, of the rocker 2 (via its diametral arm 13) and bottom 11 forms a rigid oscillating assembly.
• Each elastic end 16, 18 of the upper and lower stages 8, 10 and of the upper and lower arms 9, 11 can be formed of elastic arms, preferably three in number, gripping the corresponding pin 15, 17.
• the contact between each elastic arm and the pin 15, 17 can be punctual, as shown, in order to ensure contact between the elastic ends 16, 18 and the pins 15, 17 at discrete points only. In this way, the alignment of the upper and lower parts 6, 7 can be very precise.
• the assembly of the upper and lower parts 6, 7 and of the rocker arm 2 makes it possible to have a real physical separation of the elastic blades 4, 5, obtained in an easier way than with a manufacturing monolithic.
• the pendulum 2 constitutes the inertial part of the oscillator, the inertia of the upper and lower arms 9, 11 being able to be neglected.
• the present invention dissociates the inertial part of the oscillator from the stiffness of the flexible pivot, which facilitates the adjustment of the frequency of the oscillator.
• the inertia and the unbalance of the balance 2, on the one hand, and the torque of the flexible pivot 3, on the other hand, can be measured and corrected easily independently of each other.
• the oscillator according to the invention comprises an upper stop member 20 and a lower stop member 21 mounted respectively on the upper face of the upper part 6 and on the lower face of the part lower 7.
• These organs of abutment 20, 21 are assembled by pins 22 which pass through the arms 9, 11, 13.
• a central stud 23 of the upper abutment member 20, centered on the virtual axis of rotation A, is engaged with play in a bore 24 of an upper stop 25 fixed relative to the support 1.
• a central stud 26 of the lower stop member 21, centered on the virtual axis of rotation A is engaged with play in a bore 27 of a lower stop 28 fixed relative to the support 1.
• the studs 23, 26 rotate in the bores 24, 27 without touching the wall of the latter.
• the studs 23, 26 do not constitute pivots guided in bearings but simple movable stops capable of coming into contact with the fixed stops 25, 28 in the event of an impact received by the watch.
• the studs 23, 26 can come to bear against the side wall of the bore 24, 27.
• one of the studs 23, 26 can come to rest against the bottom of the bore 24, 27 or more generally one of the abutment members 20, 21 can stop against the corresponding fixed abutment 25, 28.
• the cooperation between the stop members 20, 21 and the fixed stops 25, 28 protects the elastic strips 4, 5 by preventing them from deforming beyond their elastic limit during radial or axial shocks.
• the upper abutment member 20 and the lower abutment member 21 are typically made of a metallic material which may be the same or which may be different from the metallic material of the rocker arm 2.
• the pins 22 can be driven into the abutment members 20, 21 and in the diametral arm 13 of the pendulum 2 and pass through the upper and lower arms 9, 11 with clearance.
• the stud-bore arrangement could be reversed, in other words the fixed stops 25, 28 could comprise the studs and the stop members 20, 21 could comprise the bores.
• the balance 2 and more generally the entire rigid oscillating assembly 2, 9, 11, 20, 21 can have its center of mass located substantially in the median plane of the flexible pivot 3, between the parallel planes in which extend respectively the elastic strips 4, 5. This reduces the risk of tilting of the pendulum 2 during movements of the arms of the wearer, during shocks or under the effect of gravity, a tilting which would disturb the chronometry by deforming outside their plane of operation the elastic blades 4, 5 or even by causing the abutment members 20, 21 to rub against the fixed abutments 25, 28. Placing the balance wheel between the upper and lower parts 6, 7 also makes the frequency of the oscillator less sensitive to the temperature.
• the balance wheel 2 metallic, deforms differently from the arms 9, 11 made of silicon.
• the arrangement according to the invention makes it possible to prevent the upper and lower silicon parts 6, 7 from becoming curved and deforming the blades 4, 5 in torsion, thus modifying their stiffness.
• the balance 2 and its rim 12 have a generally symmetrical shape with respect to the virtual axis of rotation A, this so that thermal expansion of the balance 2 does not modify, or only slightly modifies, the position of its center of mass, avoiding thus increasing the variation in rate between the different positions of the watch at the nominal operating amplitude.
• the edge 12 is preferably annular to optimize the inertia to mass ratio of the balance 2 and consequently reduce the sensitivity of the frequency of the oscillator to the orientation with respect to gravity.
• an unbalance adjustment part 29 is mounted on the balance 2.
• This unbalance adjustment part 29 is mounted in the center of the balance 2, on the member upper stop 20, to modify the inertia of the rocker arm 2 as little as possible.
• This unbalance adjustment part 29 is held elastically by the central stud 23 of the upper stop member 20 which crosses, by deforming it elastically, a slot 30 of the part 29.
• the slot 30 is oriented along the axis of symmetry of the flexible pivot 3 passing between the junction points of the flexible pivot 3 to the support 1 in plan view from above.
• Pins 31 driven into the upper abutment member 20 and passing through the slot 30 guide the piece of adjustment of unbalance 29 in translation along the aforementioned axis of symmetry when part 29 is moved by the watchmaker to adjust the unbalance of balance wheel 2.
• the unbalance adjustment part 29 makes it possible to place the center of mass of the balance 2, more precisely the center of mass of the entire rigid oscillating assembly to which the pendulum 2 belongs, on the aforementioned axis of symmetry of the flexible pivot 3 at a position distinct from that of the virtual axis of rotation A, said position being chosen so as to minimize the dependence of the frequency of oscillation with respect to the orientation of gravity for a predetermined amplitude of oscillation.
• the adjusting weights 12a carried by the balance 2 can be used to compensate for the change in the inertia of the balance 2 caused by the unbalance adjustment.
• the balance wheel 2 can carry a part 33 or have a protrusion or a recess enabling it to achieve a certain imbalance from manufacture, the unbalance adjustment part 29 then serving as a fine adjustment element.
• the part 33 can be in an arc of a circle centered on the virtual axis of rotation A and can be pierced with openings 34 whose function is to allow an optical measurement (by laser diode) of the amplitude of balance wheel 2 as a function of time.
• the oscillator according to the invention may comprise a pin 35 of the conventional type.
• This pin 35 can be carried by the lower abutment member 21, as shown. It can alternatively be carried by the upper stop member 20 or by the upper and lower arms 9, 11.
• the mode of assembly of the balance 2 and the upper and lower parts 6, 7 by the pins 17 is independent of the shape of the balance 2 and of its rim 12 and of the order in which the parts 2, 6, 7 are stacked.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Micromachines (AREA)
• Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=71575136

Family Applications (2)

Family Applications Before (1)

Country Status (4)

Families Citing this family (1)

Family Cites Families (8)

• 2020
  • 2020-07-10 EP EP20185171.4A patent/EP3936946A1/de not_active Withdrawn
• 2021
  • 2021-07-07 WO PCT/IB2021/056070 patent/WO2022009102A1/fr unknown
  • 2021-07-07 CN CN202180043501.6A patent/CN115702396A/zh active Pending
  • 2021-07-07 JP JP2022579709A patent/JP2023532440A/ja active Pending
  • 2021-07-07 EP EP21737500.5A patent/EP4179391A1/de active Pending

Also Published As

Similar Documents

Legal Events