Patent Publication Number: US-9429916-B2

Title: Isochronous paraxial timepiece resonator

Description:
This application claims priority from European Patent Application No. 14186657.4 filed on Sep. 26, 2014, the entire disclosure of which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention concerns an equipped timepiece resonator for a watch movement, including one weight connected by a plurality of flexible strips to points of attachment of a fixed structure, formed by a plate of said movement or arranged to be secured to such a plate, said weight being arranged to be subjected to a torque and/or a stress. 
     The invention also concerns a timepiece movement including a plate that supports, directly or indirectly by means of a fixed structure, at least one such resonator. 
     The invention also concerns a watch including a movement of this type. 
     The invention concerns the field of timepiece oscillators, and more specifically oscillators with flexible guiding about virtual pivots. 
     BACKGROUND OF THE INVENTION 
     There are known flexible guide members, especially for the precise positioning of components. These guide members are known to have a nonlinear restoring force, with a nonlinearity defect on the order of one percent, which is equivalent to several hundreds of seconds per day. Although this design has great advantages, it therefore has the drawback of not being isochronous. 
     CH Patent Nos 509617 and 509618 in the name of OMEGA Louis Brant &amp; Frères disclose a resonator with a plurality of long sinuous elastic strips, with two parallel pierced plates, connected, at two diametrically opposite points on their periphery, to each other and to a frame, each plate being formed by several rings, or several zigzag arms, each connecting one of these connecting points to a central weight. These plates vibrate in phase opposition perpendicularly to their planes, and each has a generally circular shape. Depending on the case, each plate is formed of a series of concentric rings connected by attachment members offset by 90°, or each zigzag arm is formed of a series of elements in concentric arcs of a circle. 
     CH Patent No 481411 in the name of MOVADO describes a resonator with long flexible loop-shaped strips connecting a network of weights. 
     FR Patent Nos 1442041 and 1421123 in the name of Centre Electronique Horloger also describe systems similar to the above system. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to propose a resonator, notably a paraxial resonator, having one weight that is movable in two linear and orthogonal degrees of freedom, which is naturally more isochronous than the aforementioned resonators with flexible guide members. 
     To this end, the invention concerns an equipped timepiece resonator according to claim  1 . 
     The invention also concerns a timepiece movement including a plate that supports, directly or indirectly by means of a fixed structure, at least one such resonator. 
     The invention also concerns a watch including a movement of this type. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which: 
         FIG. 1  shows a schematic partial plan view of a fixed structure of a watch movement carrying a paraxial plane resonator according to the invention, including a weight suspended by four flexible strips forming long spiral arms, about a virtual pivot. 
         FIG. 2  shows a block diagram of a watch including a movement incorporating one such paraxial plane resonator. 
         FIG. 3  illustrates, in a similar manner to  FIG. 1 , a variant with two concentric weights, one inside the other, and wherein, on both sides of the outermost weight the long arms are spirally wound in opposite one-directions. 
         FIG. 4  illustrates, in a similar manner to  FIG. 3 , a variant with two concentric weights, one inside the other and wherein, on both sides of the outermost weight the long arms are spirally wound in the same one-direction. 
         FIG. 5  shows, in a similar manner to  FIG. 1 , a fixed structure of a watch movement carrying a paraxial plane resonator close to the invention, including a weight suspended by four flexible strips forming long arms with a sinuous profile on both sides of a radial line, about a virtual pivot. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention utilises, as flexible guide members, very long spiral arms, to prevent movements on a first axis X perturbing the restoring force on a second axis Y, orthogonal to first axis X, and vice versa. 
     To avoid angular stiffness that is too low, which is likely to cause parasitic rotations of the resonator weight or weights, the weight is concentrated as close as possible to the centre, to reduce inertia, and thus increase the natural frequency of rotation, which prevents any detrimental excitation. 
     Different variants, similar to various known balance spring embodiments, can improve the isochronism of such a resonator. 
     It is thus possible to vary, in a non-limiting manner:
         the number of turns of the spiral, including the fractional number of turns;   the spiral pitch, which may be non-constant, and vary along the spiral;   the thickness of the spiral, which may vary along the spiral, to make the resonator as isochronous as possible (perfectly quadratic potential energy on x and y, and thus proportional to x 2 +y 2 );   the number of spiral-shaped arms.       

     The Figures illustrate non-limiting example embodiments of the invention. 
     The invention concerns an equipped timepiece resonator  1 , for a watch movement  100 , including at least one weight  2  connected, by a plurality of flexible strips  3 ,  4 ,  5 ,  6 , to points of attachment  7 ,  8 ,  9 ,  10  of a fixed structure  11 , formed by a plate of a movement  100  or arranged to be secured to such a plate, said at least one weight  2  being arranged to be subjected to a torque and/or a stress, said resonator  1  being of the paraxial type here, i.e. the weight  2  is arranged to oscillate with at least two degrees of freedom in translation. 
     Preferably, this at least one weight  2  is only one weight  2 . 
     Preferably, flexible strips  3 ,  4 ,  5 ,  6  are arranged to maintain the oscillations of said at least one weight  2  about a virtual pivot ω. 
     In a particular variant, these flexible strips  3 ,  4 ,  5 ,  6  include long arms, each having a length at least two times greater than the shortest distance between weight  2  and attachment points  7 ,  8 ,  9 ,  10 . 
     According to the invention, each at least one weight  2  is arranged to oscillate with at least two degrees of freedom in translation. 
     More specifically, these long arms are all coplanar, and their developed length is greater than the circumference of weight  2  in the plane occupied by the arms. 
     In a specific embodiment shown in  FIGS. 1, 3 and 4 , each of these long arms is spirally wound around said at least one weight  2 . 
     More specifically, resonator  1  is of the paraxial type and includes, on the one hand, first flexible strips  4 ,  6  arranged to maintain the oscillations of said at least one weight  2  about a virtual pivot ω in a first direction X, and on the other hand, second flexible strips  3 ,  7 , arranged to maintain the oscillations of said at least one weight  2  about virtual pivot ω in a second direction Y orthogonal to first direction X. 
     In a particular preferred variant, each long arm forms a spiral of more than one turn. 
     In a particular variant, each long arm forms a spiral having an integer number of turns to which a half-turn is added. 
     In a particular variant, each long arm has a sinuous profile on either side of a radial line, derived from virtual pivot ω of weight  2 , and with no return-point. 
     In a particular variant, each long arm has a developed length greater than the largest circumference of weight  2 . 
     In a particular variant, first flexible strips  4 ,  6  are identical to each other and symmetrical with respect to virtual pivot ω in the absence of excitation of resonator  1 , and the second flexible strips  3 ,  7  are identical to each other and symmetrical with respect to virtual pivot ω in the absence of excitation of resonator  1 . 
     In a particular variant, first flexible strips  4 ,  6  and second flexible strips  3 ,  7  are all identical. 
     In a particular variant, there is an even number of first flexible strips  4 ,  6  and an even number of second flexible strips  3 ,  7 . 
     In a particular variant, there is an equal number of first flexible strips  4 ,  6  and second flexible strips  3 ,  7 . 
     In a particular variant, first flexible strips  4 ,  6  are coplanar with each other and second flexible strips  3 ,  7  are coplanar with each other. 
     In a particular variant, resonator  1  is plane, and flexible strips  4 ,  6  and second flexible strips  3 ,  7  are all coplanar with each other. 
     In a particular variant, the spiral pitch varies along the spiral for each of first flexible strips  4 ,  6  and second flexible strips  3 ,  7 . 
     In a particular variant, the thickness of the spiral varies along the spiral, for each of first flexible strips  4 ,  6  and second flexible strips  3 ,  7 . 
     In a particular variant, there is only one weight  2 . 
     More specifically, the centre of inertia of weight  2  coincides with virtual pivot ω in the absence of excitation of resonator  1 . 
     In a particular variant, as seen in  FIG. 3 , resonator  1  includes a plurality of weights  2 ,  20  concentric with each other about virtual pivot ω, each innermost weight being suspended from the next by first flexible strips  4 ,  6  and second flexible strips  3 ,  7 , and the outermost weight being suspended from structure  11  by first flexible strips  40 ,  60  and second flexible strips  30 ,  70 . 
     More specifically, as seen in  FIG. 3 , on both sides of at least one such weight  2 ,  20 , the long arms are spirally wound in opposite one-directions. 
     More specifically, as seen in  FIG. 3 , on both sides of at least one such weight  2 ,  20 , the long arms are spirally wound in the same one-direction. 
     A particular embodiment, seen in  FIG. 5 , of a paraxial plane resonator  1 , close to the invention, includes a weight  2  suspended by four flexible strips  3 ,  4 ,  5 ,  6  forming long arms each having a sinuous S-shaped profile, on both sides of a radial line, Y+, X+, Y−, X−, from a virtual pivot ω of weight  2 , with no return-point. 
     In a particular preferred variant, resonator  1  forms a one-piece component including structure  11 , weight  2  or weights  2 ,  20 , first flexible strips  4 ,  6  and second flexible strips  3 ,  7 . 
     In yet another variant, resonator  1  includes flexible strips arranged in superposition on several planes, notably on several parallel planes. In a specific embodiment, flexible upper strips in a first plane tend to impart a restoring torque in a first one-direction, and flexible lower strips, attached to the same weight in a second plane tend to impart a restoring torque in a second one-direction opposite to this first one-direction. 
     In a more highly-developed variant, resonator  1  also includes a shock-absorber device and torque limiting means, notably based on the relative support of the various arms on each other, or the different twists and turns forming the same arm, in the example of  FIG. 5 , on each other. 
     More specifically, resonator  1  is made of micromachinable material or silicon or silicon oxide or similar. An oxide layer can overcome the problem of thermal compensation. 
     Similarly, the resonator may be made of quartz or similar. 
     The invention also concerns a timepiece movement  100  including a plate that supports, directly, or indirectly by means of a fixed structure  11 , at least one resonator  1  of this type. 
     The invention also concerns a watch  200  including a movement  100  of this type. 
     Resonator  1  according to the invention allows the weight  2 , comprised therein, to adopt a trajectory of curvilinear translation, or, more particularly, of elliptical translation.