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
  • G04B17/32—Component parts or constructional details, e.g. collet, stud, virole or piton
  • G04B17/34—Component parts or constructional details, e.g. collet, stud, virole or piton for fastening the hairspring onto the balance
  • G04B17/345—Details of the spiral roll
• • 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
  • G04B43/00—Protecting clockworks by shields or other means against external influences, e.g. magnetic fields
  • G04B43/002—Component shock protection arrangements

Definitions

• the present invention relates to a spiral-ferrule assembly for a watch movement, more specifically a spiral whose inner end is attached to a ferrule, ferrule which can be driven on the axis of a balance to form the movement control device .
• the patent CH 500 523 describes a ferrule having on its periphery three stops against which the inner turn of the spring can come to bear in case of radial shock to limit the deformation of the spiral. These three stops are equidistant from the center of the balance shaft. One of these stops is necessarily closer to the inner coil than the other two. This arrangement can cause problems in that the nearest stop may be touched by the inner turn during normal operation of the movement, which can disrupt said operation, especially if the amplitude of oscillations of the pendulum is large, and / or that the farthest abutment may be too far away to, in the event of an impact, serve as a support for the inner coil before its elastic limit is exceeded.
• the present invention aims to remedy the aforementioned drawbacks of the state of the art and proposes for this purpose a spiral-ferrule assembly according to claim 1 attached, that is to say a spiral-ferrule assembly comprising a ferrule and a spiral attached by its inner end to the ferrule, the ferrule being adapted to be mounted on an axis, the outer contour of the ferrule defining abutments against which the inner coil of the spiral can come to rest during an impact before the limit elastic band of the inner coil is exceeded, characterized in that said stops are located at respective distances from the center of the axis which are increasing in the direction of the hairspring going from the inside to the outside from the junction point of the hairspring to the hoop.
• This spiral-ferrule assembly is defined in the appended dependent claims 2 to 13.
• the present invention also proposes a clockwork movement comprising this spiral-ferrule assembly.
• a spiral-ferrule assembly for a watch movement according to a first embodiment of the invention comprises a ferrule 1 intended to be mounted on a balance shaft 2 and a spiral 3 attached by its end.
• the spiral 3 is partially shown, only its inner turn being visible.
• the ferrule 1 comprises three elastic arms 4 arranged in a triangle.
• the elastic arms 4 define an equilateral triangular central opening 5 whose diameter of the inscribed circle is slightly smaller than the diameter of a cylindrical or slightly conical bearing surface 6 of the axis 2, so that the axis 2 can be driven into the ferrule 1, hunting which elastically deforms the arms 4 to the outside. Due to its triangular shape, the outline of the opening 5 defines three discrete contact points 7 with the axis 2.
• the width L of each arm 4 is variable, in the manner of the elastic arms of the ferrule according to EP 1 637 940, to make more homogeneous the distribution of the stresses exerted in this arm 4 by the axis 2.
• the point 8 joining the hairspring 3 and the collar 1 is defined by one, 9c, of the three zones 9a, 9b and 9c of junction between the arms 4.
• the inner end of the spiral 3 is integral with the axis 2 and thus follows the oscillating movements of the balance.
• the outer end of the hairspring 3, not shown, is fixed by a pin to a fixed part of the movement, typically the rooster, in a known manner.
• the ferrule 1 is preferably formed integrally with the spiral 3.
• the spiral-ferrule assembly 1, 3 is typically made of a brittle material, that is to say of a material that can not deform plastically , such as a material based on silicon, glass, quartz or diamond.
• a suitable manufacturing method for the spiral-ferrule assembly 1, 3 is the deep reactive ion etching (DRIE) ionic etching method.
• the spiral-ferrule assembly 1, 3 may however, alternatively, be made of a ductile material, such as a metal material.
• discrete portions 10a, 10b and 10c of the outer contour of the ferrule 1 constitute abutments against which the inner coil of the spiral 3 can come to bear during an impact suffered by the movement.
• These stops 10a, 10b and 10c are defined by the zones 9a, 9b and 9c of junction between the elastic arms 4 and are thus arranged in a substantially regular angular distribution.
• These abutments 10a, 10b and 10c are located, respectively, at distances Ra, Rb and Rc from the center O of the axis 2 in the plane of the ferrule 1, and more precisely have an arcuate shape with a center O and of Ra, Rb and Rc respectively.
• the distances or radii Ra, Rb and Rc are chosen sufficiently small so that the hairspring 3 is not obstructed by the abutments 10a, 10b and 10c during normal oscillations of the pendulum and sufficiently large to, in the event of impact suffered by the movement, allow the inner coil of the spiral 3 to come to bear against one or more stops 10a, 10b and 10c before the elastic limit of this inner coil, at any point of this turn including at the junction point 8, exceeded ( Figure 2).
• the inner turn is in abutment against one or more abutments 10a, 10b and 10c under the effect of a shock, each of the other turns can come to bear against the turn which precedes it.
• the risk of damage to the hairspring 3 by breaking, in cases where the hairspring 3 is made of a brittle material, or by permanent deformation, in cases where the hairspring 3 is made of a ductile material, are thus reduced.
• the distances or radii Ra, Rb and Rc grow in the winding direction of the spiral 3 going from the inside to the outside from the junction point 8 of the spiral 3 to the ferrule 1, this to take account because the radius of the inner turn of the spiral 3, like that of all the other turns, increases in this direction D.
• the stop 10a closest to the junction point 8 in the direction D is at a distance Ra from center O which is smaller than the distance Rb separating the next stop 10b from the center O, which is smaller than the distance Rc separating the next stop 10c from the center O.
• the distance R8 separating the point 8 of junction between the hairspring 3 and the ferrule 1 of the center O is it typically greater than or equal to the distance Ra and less than the distances Rb and Rc.
• the distances Ra, Rb and Rc are determined by defining a certain number of radial forces F oriented towards the center O, by calculating, for example by the finite element method, the maximum elastic deformation that the inner turn can undergo under the effect of each of the radial forces F, and choosing distances Ra, Rb and Rc sufficiently large so that this maximum elastic deformation can not be reached, or at least not exceeded, and sufficiently small so that the spiral 3 does not touch the stops 10a, 10b and 10c during normal operation. Deformation of the inner coil of the spiral 3 in each of the points 3a,
• 3b and 3c located opposite the abutments 10a, 10b and 10c respectively, in a configuration where this point bears against the corresponding abutment 10a, 10b or 10c under the effect of a radial force F applied at this point, is thus a percentage, less than or equal to 100%, of the maximum elastic deformation can undergo the inner turn at this point, which confers a safety factor (ratio between the maximum elastic deformation and the elastic deformation when the inner coil bears against a stop 10a, 10b or 10c) greater than or equal to 1.
• the above percentage is preferably substantially the same for all abutments 10a, 10b and 10c.
• this percentage is about 50% (safety factor of about 2), while the percentage of deformation of the inner coil in normal operation of the hairspring relative to the maximum elastic deformation this inner turn is about 25%, this for a spiral pitch 3 of about 93 microns and a thickness or width of spiral turns 3 of about 30 microns.
• the distances Ra, Rb and Rc are equal to the same percentage, respectively, of the rays r, rb and corresponding rc of the inner turn at rest, that is to say distances between the points 3a, 3b, 3c and the center O.
• This percentage is for example equal to about 90%, for a step of the spiral 3 of about 93 microns and a thickness or width of the coils of the spiral 3 of about 30 microns.
• the safety factors for the abutments 10a, 10b and 10c may be the same or may less be close to each other.
• the shell 1 can therefore reliably protect the hairspring 3 in the event of a radial impact, whatever the direction of said impact, without disturbing the normal operation of the balance-spring balance device, even if the amplitude of the oscillations of the balance is big.
• FIG. 3 shows another embodiment of the invention, in which the ferrule 1 comprises, in addition to the abutments 10a, 10b, 10c defined by the zones 9a, 9b, 9c of junction between the arms 4, stops 10d, 10e. , 10f defined by elements 11 protruding radially from the outer side of the arms 4 in the zone center of the arms 4 in contact with the axis 2.
• the stops 10a, 10b, 10c 1 the abutments 10d, 10e, 10f are in a center circle of the center of the center of the axis 2.
• the opening 5 of the ferrule 1 in which the axis 2 is driven may have a shape other than triangular, such as another polygonal shape, regular or not, defined by a number of elastic arms greater than three.
• the ferrule could be in the form of a split ring having radial projections defining the stops.
• the abutments could be contiguous rather than discrete, and more particularly a large continuous portion of the outer contour of the ferrule could serve as a stop.
• the outer contour would then have a shape similar to that of the inner coil, that is to say a radius increasing in the direction D of winding of the spiral going from the inside to the outside from the point of junction between the spiral and the ferrule.
• the outer contour could in this case be defined by a frame surrounding elastic arms, or could be the outline of a ferrule "full", without lights of elasticity.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Springs (AREA)
• Toys (AREA)
• Gripping On Spindles (AREA)

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• 2006
  • 2006-05-17 EP EP06010169A patent/EP1857891A1/de not_active Withdrawn
• 2007
  • 2007-04-26 EP EP07734401.8A patent/EP2018601B1/de active Active
  • 2007-04-26 US US12/085,663 patent/US7758237B2/en active Active
  • 2007-04-26 WO PCT/IB2007/001083 patent/WO2007132306A2/fr not_active Ceased
  • 2007-04-26 JP JP2009510564A patent/JP5235869B2/ja active Active
  • 2007-04-26 CN CN2007800031968A patent/CN101375218B/zh active Active

Non-Patent Citations (1)

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