Patent Publication Number: US-8118480-B2

Title: Driving and transmitting element for an escapement, roller table and escapement equipped with them, and timepiece including them

Description:
The present invention relates to horological movements, and more particularly to escapements. In particular, it aims at a driving and transmitting element, on the one hand for driving the escapement anchor turning together with the roller table driven onto the balance staff, and on the other hand for transmitting to the roller table an impulse coming from the anchor. It also aims at a roller table including such a driving and transmitting element. It further aims at an escapement provided with such a driving and transmitting element and/or with such a roller table. It finally aims at a timepiece including such a driving and transmitting element and/or such a roller table and/or such an escapement. 
     Conventionally, a lever escapement includes a simple or double roller table driven onto the balance staff. A roller pin is driven into the underside of the roller table; when a double roller table is present, it is driven into the underside of the large roller table. The roller pin is a part that generally consists of ruby or garnet and has the shape of an ellipse, crescent, or triangle which when installed cooperates with the anchor fork. 
     In the work of a conventional escapement, the balance staff turns in a direction and rotates the roller table. The roller pin driven into the roller table rotates with it and cooperates with one of the horns of the fork in order to set the anchor in rotary motion about the anchor axis. While the anchor is rotating, one of its pallets liberates a tooth of the escape wheel that starts rotating. While being liberated, this same tooth imparts to the anchor an impulse via the same pallet. The anchor fork while still in contact with the roller pin imparts its impulse to said roller pin. This then transmits its impulse to the roller table, which in its turn transmits the impulse to the balance staff onto which it is driven. The same functions happen in the reverse order while the balance staff rotates in the other direction. 
     Thus, the roller pin has a twofold function: on the one hand it rotates together with the roller table making the anchor rotate so as to liberate the escape wheel, and on the other hand it transmits an impulse from the anchor to the roller table. It thus has a function of rotary drive and a function of energy transmission. 
     For several years now, numerous parts of horological movements are made of silicon-based material offering a very good coefficient of friction without the need for lubrification. The escape wheel and the anchor are among the parts made of silicon-based material. It is desirable that the element driving the anchor be made of a silicon-based material as well, so that a full kinematic chain would become available that consists of silicon-based material and has the same coefficient of friction everywhere. 
     It is not possible, however, to make a conventional roller pin of silicon-based material. In fact, such materials are brittle, that is, lack a plastic domain and will thus not allow a pin of silicon-based material to be driven into a metal plate. 
     It is an aim of the present invention to propose a driving and transmitting element for an escapement that could fill the functions of rotating the anchor and of transmitting energy from the anchor to the roller table and to the balance staff when the escapement is in operation, and that could be made of a material on the basis of silicon or any other brittle material. 
     According to a first aspect, the invention relates to a driving and transmitting element for an escapement in a timepiece, said escapement including an escape wheel, an anchor and at least one roller table driven onto a balance staff, said driving and transmitting element being intended on the one hand to rotate said anchor when it rotates together with said roller table, and on the other hand to transmit an impulse from said anchor to said roller table. Said driving and transmitting element includes elastic clamping means adapted to operate within a clamping plane and intended while working to be arranged in such a way that said clamping plane be substantially perpendicular to said balance staff and include means of interaction extending from said clamping means and intended to interact with said anchor in order to drive it. 
     Particular embodiments of the driving and transmitting element are described herein. According to one of them, the elastic clamping means are a split ring, and the means of interaction are a stud radially extending from said ring. 
     According to a second aspect, the invention relates to a roller table for a lever escapement, said roller table including a central hole intended to be traversed by a balance staff in order to fasten said roller table rigidly to said balance staff. Said roller table includes a driving and transmitting element according to the first aspect of the invention, and holding means in order to maintain the angular position of said driving and transmitting element. 
     According to a particular embodiment, said roller table additionally includes a rim extending around said central hole. 
     According to a third aspect, the invention relates to a lever escapement of the type including an escape wheel, an anchor and at least one roller table that includes a driving and transmitting element according to the first aspect and/or a roller table according to the second aspect. 
     According to a fourth aspect, the invention relates to a timepiece and notably a watch including a driving and transmitting element according to the first aspect and/or a roller table according to the second aspect and/or a lever escapement according to the third aspect. 
    
    
     
       The invention will be understood more readily when reading the following detailed description of particular embodiments furnished by way of illustration but in no way limiting, while referring to the annexed drawings where: 
         FIGS. 1 and 2  represent a first embodiment and a second embodiment of the driving and transmitting element in perspective views according to the first aspect of the invention; 
         FIG. 3  represents a perspective view of a first embodiment of a roller table of an escapement having installed on it a driving and transmitting element according to the first embodiment, and shows a first embodiment of the holding means; 
         FIG. 4  represents a perspective view of a second embodiment of a roller table of an escapement having installed on it a driving and transmitting element according to the second embodiment, and shows a second embodiment of the holding means; 
         FIGS. 5 and 6  illustrate two working positions of an escapement seen from the front that show the cooperation of the escapement anchor with the roller table and with the driving and transmitting element of  FIG. 3 ; 
         FIG. 7  schematically represents a watch provided with an escapement including the roller table and the driving and transmitting element of  FIG. 3 . 
     
    
    
     Referring first of all to  FIG. 1 , a first embodiment of a driving and transmitting element  10  is represented that has elastic clamping means and means of interaction. The elastic clamping means are in the shape of a ring  20  having an axis  100 , an inner face  22  and an outer face  32 , and a slot  30  opening it. A stud  40  extends radially from said outer face  32  and diametrically opposite to slot  30 . In the example illustrated, slot  30  is axial. It could be slanting. Slot  30  imparts elasticity to ring  20 . Stud  40  and slot  30  define a first direction  11  of the driving and transmitting element  10  which together with the axis  100  of ring  20  forms a plane of symmetry for the driving and transmitting element  10 . The plane of ring  20  that is perpendicular to axis  100  defines an elastic clamping plane. The inner face  22  of ring  20  includes two segments  26  next to the slot  30  and a segment  28  diametrically opposite to slot  30 . It also includes two recessed segments  24 , each of them situated between one of the segments  26  next to and the segment  28  opposite to the slot. The two recessed segments  24  are separated from axis  100  by a radius slightly larger than the common radius of the other three segments  26 ,  26 ,  28 . 
     Stud  40  has a shape that widens from its end in contact with the outer surface  32  of ring  20  toward its free end. In the example illustrated, stud  40  has an substantially triangular profile, its free end having an end face  46  substantially plane and perpendicular to the first direction  11 . Stud  40  has two lateral faces  44  linking the end face  46  with the outer face  32  of ring  20 . The junction between each of the lateral faces  44  and the end face  46  consists of an edge  48  that preferably is slightly rounded. 
     A second embodiment of a driving and transmitting element  50  is represented in  FIG. 2 . It differs from the first embodiment of the driving and transmitting element  10  in that stud  40  is provided with a through hole  54  that extends along a second direction  12  cutting the clamping plane of ring  20 . The second direction  12  preferably is parallel to axis  100  of ring  20 . The through hole  54  preferably is located in the vicinity of the free end of stud  40 . 
     Stud  40  of the driving and transmitting element  50  according to the second embodiment may have lateral faces  42  that are recessed in a way similar to that of stud  40  of the driving and transmitting element  10  according to the first embodiment. This provides a shape that is generally the same in the driving and transmitting elements  10 ,  50  according to the two embodiments. It will thus be possible to implement common production steps for the two embodiments of the driving and transmitting elements  10 ,  50  while providing for an additional production step with which to realize the through hole  54  for the driving and transmitting element  50  according to the second embodiment. 
     In a way that is common to the two embodiments just described, the driving and transmitting elements  10 ,  50  are made of a material that has no plastic domain, for instance a silicon-based material. In the examples illustrated in  FIGS. 1 and 2 , ring  20  and stud  40  held by it consist of a single piece. 
       FIG. 3  illustrates a roller table  60  according to a first embodiment that is provided with a driving and transmitting element  10  according to the first embodiment. In known ways, roller table  60  has a central hole  62  by which when in the working position it is driven onto a balance staff  2  so that a rigid fastening of said roller table  60  to said balance staff  2  is produced. Ring  20  of the driving and transmitting element  10  is installed on roller table  60  around balance staff  2 . In the figure, balance staff  2  is shown in broken lines in order to avoid that part of the ring  20  is hidden. Ring  20  is held in place by virtue of a slot  30  that is present so that an elastic clamping of balance staff  2  can be guaranteed in operation, and a potential sliding of ring  20  in the axial direction  100  can be avoided. Since the inner face  22  of ring  20  has two recessed segments  24 , then the contact between this inner face  22  and balance staff  2  is established only over the three segments that are not recessed, that is, the two segments  26  next to slot  30  and the segment  28  diametrically opposite to slot  30 . Such an arrangement with three contact regions serves to improve the elastic clamping action of ring  20  on the balance staff. 
       FIG. 4  illustrates a roller table  70  according to a second embodiment that is provided with a driving and transmitting element  50  according to the second embodiment. Similarly to roller table  60  according to the first embodiment, roller table  70  includes a central hole  72  by which it is driven onto the balance staff (not represented) when in the working position. In addition, roller table  70  includes an annular rim  74  that extends around the central hole  72  following a direction perpendicular to the plane of roller table  70 . Rim  74  serves to increase the contact area between roller table  70  and the balance staff. Rim  74  also has a function of support for the driving and transmitting element  50 . In fact, ring  20  of the driving and transmitting element  50  is installed on roller table  70  around rim  74 . It is held in place by virtue of slot  30  securing its elastic clamping action while avoiding a potential sliding of ring  20  in the axial direction  100 . Here again, the contact between the inner face  22  of ring  20  and the rim  74  occurs only along the three segments  26 ,  26 ,  28  that are not recessed. Such an arrangement with three contact regions serves to improve the elastic clamping of rim  74  by ring  20 . 
     The angular position of the driving and transmitting elements  10 ,  50  is maintained by holding means  4 ,  4 ,  6  of roller tables  60 ,  70 . 
     A first implementation of the holding means is illustrated in  FIG. 3  relating to a roller table  60  according to the first embodiment and a driving and transmitting element  10  according to the first embodiment. Said holding means consist of two pegs  4 ,  4  fastened at the face of roller table  60  that receives the driving and transmitting element  10 . Pegs  4 ,  4  are arranged on the face of roller table  60  in such a way that stud  40  is immobilized between them when ring  20  in the working position has been placed around balance staff  2 . The lateral faces  42  of stud  40  are recessed in the region of contact with the two pegs  4 ,  4  so that said pegs  4 ,  4  will not interfere with the cooperation of the free end of stud  40  with the anchor while the escapement works, which will be described further down while referring to  FIGS. 5 and 6 . This first implementation of the holding means is compatible as well with a roller table  70  according to the second embodiment, even though such a variant has not been represented in the figures for the sake of simplicity. In this case ring  20  in its working position would be immobilized by pegs  4 ,  4  against the rim  74  of roller table  70 . 
     A second implementation of the holding means that is particularly adapted to the driving and transmitting element  50  according to the second embodiment is illustrated in  FIG. 4  relating to a roller table  70  according to the second embodiment. Said holding means consist of a single peg  6  fastened to the face of roller table  70  receiving the driving and transmitting element  50 . Peg  6  is arranged in such a way on the face of roller table  70  that stud  40  will be immobilized by insertion of this peg  6  into the through hole  54  when ring  20  in its working position has been placed around rim  74  of roller table  70 . The diameter of peg  6  is adjusted to the diameter of the through hole  54  in such a way that peg  6  will not constrain stud  40  of the driving and transmitting element  50 . This implementation of the holding means is again compatible with a roller table  60  according to the first embodiment, even though such a variant has not been represented in the figures for the sake of simplicity. In this case ring  20  in its working position would be immobilized by peg  6 , directly against balance staff  2 . 
     In a manner that is common to the two embodiments of roller tables  60 ,  70  just described, roller tables  60 ,  70  preferably are made of metal, for example steel or nickel. Roller tables  60  and  70  as well as pegs  4 ,  4 ,  6  preferably are realized in monoblock fashion. More preferably yet, pegs  4 ,  4 ,  6  are obtained by galvanic growth using a process known under the name of LIGA. 
       FIGS. 5 and 6  illustrate two configurations of an operating escapement according to a third aspect of the invention. They show a lever escapement  80  which in known manner comprises an escape wheel  82  provided with teeth  822  and an anchor  84  capable of rotating about an anchor axis  806 . The oscillatory motion of anchor  84  about anchor axis  806  is limited by two stops  802 ,  804 . In known manner, anchor  84  includes a dart that is not represented in order to simplify the figure, and a fork  840  held by a lever  842 . Fork  840  of anchor  84  includes two horns  844 ,  846 , while the other end of anchor  84  includes two pallets  848 . 
     In addition, escapement  80  includes a roller table  60  according to the first embodiment driven onto a balance staff  2  and provided with a driving and transmitting element  10  according to the first embodiment that includes a ring  20  and a stud  40  immobilized on roller table  60  by two pegs  4 ,  4  as described while referring to  FIG. 3 . 
       FIGS. 5 and 6  are seen in section along the plane of contact between roller table  60  and the driving and transmitting element  10 . Thus, roller table  60  is represented in broken lines allowing a simplification of the figures. 
     In  FIG. 5 , balance staff  2  rotates in the direction indicated by arrow  200 . Roller table  60  driven onto balance staff  2  rotates in the same direction. The driving and transmitting element  10  that has been immobilized on roller table  60  by means of pegs  4 ,  4  rotates with it until encountering one  844  of the horns  844 ,  846  of fork  840  and causing it to rotate, which produces a rotation of anchor  84  about anchor axis  806 . In its rotation, one  848  of the pallets of anchor  84  liberates tooth  822 , which allows the escape wheel  82  to rotate. While being liberated, tooth  822  transmits an impulse coming from the escape wheel  82  to anchor  84 , which via the driving and transmitting element  10  transmits it to the roller table  60  and to the balance staff  2  onto which said roller table  60  is driven. 
     In  FIG. 6 , balance staff  2  rotates in the direction indicated by arrow  300  while stud  40  cooperates with the other horn  846  of fork  840 . A movement results that is comparable to that just described while referring to  FIG. 5 . 
     In both cases, the cooperation between stud  40  and each of the horns  844 ,  846  of fork  840  is realized via the edges  48  of stud  40 . The contact between edges  48  and horns  844 ,  846  is improved when they are slightly rounded. 
     When escapement  80  is functioning, stud  40  of the driving and transmitting element  10  advantageously fills the classical functions of roller pin of a conventional escapement. 
       FIG. 7  illustrates in a schematic manner a timepiece  90 , typically a watch, that is provided with an escapement  80  such as just described while referring to  FIGS. 5 and 6  and including an escape wheel  82 , an anchor  84 , a roller table  60 , and a driving and transmitting element  10 . 
     While not shown in  FIGS. 5 ,  6 ,  7 , the escapement  80  and timepiece  90  according to the invention could include a roller table  60  according to the first embodiment and provided with a driving and transmitting element  50  according to the second embodiment, or also a roller table  70  according to the second embodiment and provided with a driving and transmitting element  10  according to the first embodiment, or even a roller table  70  according to the second embodiment and provided with a driving and transmitting element  50  according to the second embodiment. 
     It is understood that the invention is not limited to the embodiments that have been illustrated in the figures but covers variant embodiments within the capacity of one skilled in the arts. For example, the end face  46  of stud  40  of the driving and transmitting element could be concave or convex, instead of plane. For example, the elastic clamping means could have a form different from that of a split ring, and clamping could be realized over two rather than three points.