Abstract:
A movement for a timepiece having a retrograde display member displaying at least one time division, includes a going train, elements for driving the display member including a wheel unit driven by the going train and carrying a first cam sharing the same axis of rotation. The movement also includes a rocker supporting a probe held against the edge of the first cam by deformable elastic elements undergoing a deformation of variable amplitude. This results in the application of a corresponding force on the rocker in proportion to the distance between the probe and the axis of rotation of the first cam. The movement also includes drive members to connect the rocker to a retrograde display member. A force-regulating device is interposed between the elastic elements and the rocker.

Description:
TECHNICAL FIELD 
     The present invention concerns a display module for timepiece movement designed to drive a retrograde display member displaying at least one time division, comprising a frame supporting drive means designed to drive the display member comprising a wheel, designed to be driven by a going train of the timepiece movement, and supporting a first cam sharing the same axis of rotation in reference to the frame. The display module also comprises a lever supporting a feeler-spindle arranged so as to bear against the periphery of the first cam under the effect of deformable elastic means undergoing a deformation of variable amplitude. This drives the application of a corresponding force on the lever, according to the distance separating the feeler-spindle from the axis of rotation of the first cam. The display module also comprises transmission means designed to connect the lever to the drive means of the retrograde display member. 
     The present invention also concerns a timepiece movement having the above characteristics as well as a timepiece comprising a movement of this type. 
     In the continuation of the text, the term “display module” designates the organs making it possible to drive an indicator organ, whether they are integrated directly on the plate of a clockwork movement or are effectively assembled in the form of a module likely to be attached to a preexisting basic movement. As a result, the term “frame” will designate the clockwork movement or an attached module bridge, without impact on the scope of the present invention, which is not limited to one or the other alternative. 
     BACKGROUND OF THE INVENTION 
     Many movements meeting the preceding definition are known in the prior art. As an example, patent CH 694 349, issued in the name of Franck Müller Watchland SA, describes of movement of this type designed to display both the minutes and hours in a retrograde manner. Each of the corresponding mechanisms comprises a lever with two arms connected by a bend, in the region of which the lever pivots in relation to the frame of the movement. The free end of a first arm supports a feeler-spindle arranged bearing against the periphery of a cam driven in rotation by the going train of the movement, while the free end of the second arm supports a rack arranged engaged with a going train of a display member. A long spring is connected to the frame by a first of its ends, while its second end is arranged so as to apply a force on the lever, to maintain the feeler-spindle in contact with the cam. 
     This type of construction presents certain drawbacks, in particular related to the application, to the going train of the movement, of a frictional force having a significant variation in amplitude between two extreme positions of the lever. Indeed, one sees, on one hand, that the axis of rotation of the lever is relatively remote from the feeler-spindle and, on the other hand, that the point of support of the spring on the lever is provided at the level of the feeler-spindle and is therefore also distanced from the axis of rotation of the lever. This results in a significant amplitude of the deformations of the spring between one and the other of the extreme positions of the lever, or a significant amplitude of the variation of the force this spring applies on the lever. The lever being arranged bearing on a cam, itself driven in rotation by the going train of the movement, the operation of the movement suffers a disturbance which may present non-negligible deviation values. 
     BRIEF SUMMARY OF THE INVENTION 
     The primary aim of the present invention is to overcome the drawbacks of the known mechanisms of the prior art, by proposing a movement for a timepiece with retrograde display in which the means for implementing the retrograde display almost do not disturb the operation of the movement at all. 
     To this end, the present invention more particularly concerns a movement for a timepiece of the type mentioned above, characterized by the fact that a force-regulating device is inserted between the elastic means and the lever. 
     Thanks to this characteristic, the operation of the movement has better precision. Moreover, this precision is maintained even in the case where the movement is adapted to the driving of a display member on a significant angular sector, in particular greater than 60 degrees, preferably greater than 120 degrees. 
     In one preferred embodiment, it is provided that the wheel is driven by a wheel frictionally mounted on a cylinder wheel tube, the lever comprising a rack having a toothing arranged engaged with a toothing of a pinion mounted free in rotation on the cylinder wheel tube and integral in rotation with an additional tube, the latter being designed to ensure the driving, at least indirectly, of a display member displaying hour information. 
     According to a first embodiment, one can provide that the force-regulating device comprises a second cam arranged integral with the lever and sharing an axis of rotation with this lever. In this case, the elastic means preferably comprise a long spring having a straight portion whereof one free end is arranged bearing against the periphery of the second cam. Thus, the application of the force on the lever is done in the form of a rotational torque applied directly to its axis of rotation due to the force undergone by the second cam. 
     According to a second embodiment, one can provide that the additional tube, designed to support the display member, is integral with an additional cam, having the same axis of rotation, and having a periphery of variable radius designed to cooperate with an additional feeler-spindle supported by an additional lever, the latter having a support surface arranged to cooperate with the elastic means. 
     In this case, the lever undergoes the force generated by the elastic means through its rack, the pinion and the additional cam, the periphery of which makes it possible to regulate the force effectively transmitted to the lever. 
     One may preferably provide that the periphery of the additional cam has a shape at least partially corresponding to a logarithmic curve portion. 
     Moreover, a runner may be supported by the additional feeler-spindle to ensure contact between the additional lever and the periphery of the additional cam with the least amount of friction possible. 
     Advantageously, a movement of this type can be implemented in a timepiece comprising a display member having a time size sweeping an angular sector having an angle greater than 120 degrees, such as an hour display over a sector of 270 degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the present invention will appear more clearly upon reading the detailed description of one preferred embodiment which follows, done in reference to the appended drawings provided as non-limiting examples and in which: 
         FIG. 1  illustrates a simplified top view of a detail of the timepiece movement according to a first variation of one preferred embodiment of the present invention, in a first configuration; 
         FIG. 2  illustrates a simplified top view similar to the view of  FIG. 1 , in a second configuration; 
         FIG. 3  illustrates a simplified transverse cross-sectional view of the movement from the preceding figures; 
         FIG. 4  illustrates a simplified top view of a detail of the timepiece movement according to a second variation of a preferred embodiment of the present invention, and 
         FIG. 5  illustrates a simplified transverse cross-sectional view of the movement of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a top view of a construction detail of the movement according to a first variation of one preferred embodiment of the present invention, more particularly of its mechanism for implementation of a retrograde display. This mechanism is presented in a first configuration in  FIG. 1 , and will be presented in a second, different configuration in  FIG. 2 . 
     The embodiment described, as a non-limiting illustration, concerns a drive mechanism of an hour hand  1  with a retrograde-type display, in particular relative to a graduated sector (not visible) extending over an angle of 270 degrees. 
     We have diagrammatically illustrated, in the figures, the implementation of the movement according to the invention in a timepiece comprising a case comprising in particular a middle  2 . The movement comprises a plate (not shown) on which the display module rests, and in a hole of which a setting stem  3  is mounted, better visible in  FIG. 3 . 
     The hour hand  1  is arranged at the center of the timepiece while being driven by a cylinder wheel (reference  4 ,  FIG. 3 ), the tube  5  of which supports an additional tube  6 , mounted free in rotation on the cylinder wheel. The cylinder wheel is driven conventionally by a going train (not visible) of the movement, the latter possibly being of the mechanical or electromechanical type without effect on the object of the present invention. 
     An hour wheel  7  is also frictionally mounted on the cylinder wheel tube  5 . A wheel unit  8  is arranged away from the hour wheel  7  and supports a control wheel  9  as well as a first cam  10 , the periphery of which has a spiral shape. The control wheel  9  and the first cam  10  are made integral in rotation, using a pin  11 , and share an axis of rotation  12  with the frame of the movement. The control wheel  9  has a peripheral toothing arranged engaged with the toothing of the hour wheel  7 , such that the first cam  10  is driven in rotation, in the counterclockwise direction in  FIG. 1 , by the movement of the hour wheel  7 . 
     The retrograde display mechanism also comprises a lever  20 , mounted in rotation on the frame of the movement, along an axis X located in the immediate vicinity of the periphery of the control wheel  9 . Going from its region pivotably mounted on the axis X, the lever  20  has two arms  21  and  22 . 
     The first arm  21  initially comprises two portions  23  and  24  moving away from each other before coming together to form a loop in the extension of which extends a feeler-spindle  25 . The free end  26  of the feeler-spindle, ending in a point, is arranged bearing against the periphery of the first cam  10 . 
     The second arm  22  has an elongated and curved shape, to go around the first cam  10 , ending with a rack  27 , arranged engaged with a pinion  28  integral with the additional tube  6 . 
     A second cam  30  is mounted in rotation on the axis X, while being integral with the lever  20 . This has a heart-shaped periphery, more precisely defined by a double curve, each of which corresponds to a logarithmic curve portion. 
     A long spring  31  is fixed to the frame of the movement, using a screw  32 , by a first end  33  wound in a ring shape, while its second end  34  has a flat surface  35  arranged bearing against the periphery of the second cam  30 . A pin  36 , integral with the frame, forms a counter-support to prevent the rotation of the spring in the counterclockwise direction. 
     One will note that it is important to ensure that friction between the flat surface  35  and the periphery of the second cam  30  is limited. Thus, one will be able, for example, to provide for using a material such as ruby or sapphire to produce an end attached on the long spring  31 . In the alternative, one may provide the end  34  with a support supporting a runner (as visible in  FIGS. 4 and 5 ) designed to ensure contact between the long spring  31  and the periphery of the cam  30 . 
     From an operational perspective, when the first cam  10  turns in the counterclockwise direction, it has a increasing radius in comparison with the position of the feeler-spindle  25 , driving a rotation of the lever  20  in the same direction. When the lever turns in relation to its axis X, the rack  27  causes a rotational movement of the additional tube  6 , in the clockwise direction, this being free to turn in relation to the cylinder wheel. Thus, the hour hand  1  evolves in comparison with the graduations which may extend over twelve hours, for example, between the initial and final positions of the hand, these positions being spaced apart at an angle of 270 degrees according to the present embodiment, for information. 
     At the same time, the second cam  30  also turns in the counterclockwise direction, slightly deforming the spring  31  as its radius increases in the contact region of the flat surface  35 . 
     The spring constant of the spring  31  is adjusted such that the contact of the point  26  of the feeler-spindle on the periphery of the first cam is guaranteed at all times, without, however, creating overly significant friction. 
     The feeler-sensor  25  thus has a progressive and continuous separation in reference to the axis of rotation  12  of the first cam  10 . We have illustrated small x&#39;s on the periphery of the first cam to show the positions corresponding respectively to each of the hours displayed by the hour hand  1  in comparison with the graduations. 
       FIG. 2  shows a view similar to  FIG. 1 , in a different configuration of the retrograde display mechanism, more precisely, a little less than twelve hours after the configuration of  FIG. 1 , the first cam  10  having made almost a full revolution in this interval. According to the illustrated embodiment, the hour hand  1  has undergone an angular movement in the vicinity of 270 degrees in the same time. 
     It appears in this figure that, while the tip  26  of the feeler-spindle  25  has undergone a movement of maximal amplitude, the second cam  30  has completed a rotation along an angle smaller than 90 degrees. Its radius between the positions of  FIG. 1  and  FIG. 2  having varied little, the spring  31  has a limited tension, sufficient, however, to exert pressure on the second cam  30 , aiming to return it to its position from  FIG. 1 , when the tip of the feeler-spindle passes the flank  40  of the periphery of the first cam  10 . Thus, this operation is similar to the return to zero of the hands indicating a time measured in a timepiece movement with chronograph function. 
     Unlike the mechanisms of the prior art, the tension variation of the spring between these two extreme positions of the feeler-spindle advantageously has a negligible impact on the operation of the going train. This particular characteristic also makes it possible to use a time size indication sector of greater angular amplitude than with the earlier mechanisms. 
     Moreover, the action of the spring on the lever, via the second cam  30 , makes it possible to obtain a slower return of the hour hand  1  to its initial position than in the timepieces according to the prior art, in which the spring acts directly on the lever. One can note that the theoretical return speed of the hand is constant throughout the duration of this movement due to the use of a logarithmic curve, which is not the case if the cam has a periphery whereof the shape is based on the Archimedes curve, in particular in the region of the locking position shown in  FIG. 1 , which is why the former is preferred. 
       FIG. 3  shows a simplified transverse cross-sectional view of a part of the movement which has just been described in relation to  FIGS. 1 and 2 . 
     It appears from this figure that the shared axes of rotation  12  and X are defined by the use of unique pivots for the corresponding pieces, namely, on one hand, the control wheel  9  and the first cam  10 , and on the other hand, the lever  20  and the second cam  30 . 
     Moreover, it appears from  FIG. 3  that the setting stem  3  supports, conventionally, a winding-pinion  41  arranged engaged with a crown-wheel  42  of the movement, to perform the winding of a barrel spring (not shown), as well as a sliding pinion  43  which can be brought to engage with an intermediate wheel  44 , itself engaged with the cylinder wheel  4  to perform the setting of the display members. 
     During time setting operations, the hour wheel  7  is driven simultaneously with the cylinder wheel  4  to cause the control wheel  9  and the first cam  10  to turn and, as a result, the additional tube  6  supporting the hour hand  1 . 
     One can note that from the position illustrated in  FIG. 1 , a counterclockwise rotation of the first cam  10  is not recommended due to the fact that the feeler-spindle  25  can be pushed against the flank  40  of the cam. In this case, the user must be able to feel a resistance and change the direction of rotation of the setting stem to perform the setting operation. If, despite everything, it were to insist on the wrong direction of rotation, the respective surfaces of the tip of the feeler-spindle and the flank of the cam are such that winding of the feeler-spindle along this is possible. 
       FIGS. 4 and 5  show, in simplified top and transverse cross-sectional views, respectively, a display module for clockwork movement according to a second variation of a preferred embodiment of the present invention. 
     The second variation is different from the first through a different arrangement of the elastic means making it possible to ensure a good quality of contact between the feeler-spindle  25  and the periphery of the first cam  10 , the force-regulating means applied to the lever being adapted as a result. 
     More precisely, the additional tube  6  supporting the pinion  28  is also integral with an additional cam  50  having a periphery of variable radius. The latter has, from its smallest radius to its largest radius, a shape corresponding to a logarithmic curve portion. Moreover, the regions having the smallest radius and largest radius are connected by a substantially radial flank  51 . 
     Moreover, the display module according to the second variation of embodiment also comprises an additional lever  52  mounted rotatingly on the frame of the movement, along an axis of rotation located away from the axis of rotation of the cylinder wheel  4 . 
     The additional lever  52  comprises a base  53  from which extends an arm  54 , the free end of which supports a feeler-spindle  55 , here realized in the form of a support  56  supporting a runner  57  designed to be arranged bearing against the periphery of the additional cam  50 . The implementation of a runner of this type makes it possible to reduce the friction resulting from the contact between the feeler-spindle  55  and the periphery of the additional cam  50 , when the latter is driven in rotation under the effect of the cooperation between the rack  27  and the pinion  28 . As already mentioned, the runner can be made in ruby or sapphire, as non-limiting information. 
     Moreover, the base  53  of the additional lever comprises a support surface  58  assuming the form of an edge. 
     A long spring  61  is fixed to the frame of the movement, using a screw  62 , by a first end  63  wound into a ring shape, while its second end  64 , free, is arranged bearing against the support surface  58  of the additional cam  50 . A screw  66 , integral with the frame, forms a counter-support to prevent the clockwise rotation of the spring, thereby making it possible to cause its deformation when the support surface  58  is driven in counterclockwise rotation, under the effect of the increase in the radius of the additional cam  50 . 
     The screw  66  is preferably an eccentric thanks to which the orientation of the long spring  61  can be adjusted with great precision. 
     From an operational point of view, when the first cam  10  turns counterclockwise, it has an increasing radius in comparison with the position of the feeler-spindle  25 , driving a rotation of the lever  20  in the same direction. When the lever turns in relation to its axis X, the rack  27  causes a rotational movement of the additional tube  6 , clockwise, this being free to turn in relation to the cylinder wheel. Thus, the hour hand  1  evolves in comparison with graduations which may, for example, extend over twelve hours between the initial and final positions of the hand. 
     At the same time, the additional cam  50  turns simultaneously in the clockwise direction, thereby having a radius increasing to the feeler-spindle  55  of the additional lever  52  which turns, because of this, in the counterclockwise direction. The rotation of the additional lever causes a progressive deformation of the spring  61  as the radius of the periphery of the additional cam increases. 
     Thanks to this structure, the lever  20  undergoes at all times, except during the brief retrograde movement, two antagonistic forces, namely a first force tending to cause it to turn counterclockwise and exerted by the periphery of the first cam  10 , and a second force tending to cause it to turn clockwise under the effect of the deformation of the spring  61 , generating a force transmitted to the lever  20  through the additional lever  52 , its feeler-spindle  55 , the periphery of the additional cam  50 , the pinion  28  and the rack  27 . 
     The force generated by the deformation of the spring  61  is regulated by the shape of the periphery of the additional cam  50 , which makes it possible to control the corresponding torque transmitted to the pinion  28 . In reference to the first variation of embodiment, one will note that the regulation is done here with better precision insofar as the additional cam  50  has an angle of rotation much larger than that of the second cam  30  between the two extreme positions of the display member  1 . Indeed, the present variation offers a reduction of the rotation of the lever  20  through the gear link between the rack  27  and the pinion  28  allowing the additional cam  50  to have a larger useful portion of its periphery than that of the second cam  30  of the first variation. 
     One can also see that this construction, due to the antagonistic forces it generates, presents the additional advantage of preventing the appearance of play at the level of the gear link provided between the pinion  28  and the rack  27 . 
     The spring constant of the spring  61  is adjusted such that the contact of the tip  26  of the feeler-spindle on the periphery of the first cam  10  is guaranteed at all times, without, however, creating overly significant friction. 
     We have also diagrammed the presence of a coupling  70  to provide the connection between the control wheel  9  and the first cam  10 , in complete safety, which makes it possible to offset the drawbacks previously mentioned in relation with time setting operations. 
     The preceding description corresponds to one preferred embodiment of the invention described non-limitingly. In particular, the shapes illustrated and described for the various component elements of the timepiece movement are not limiting. One may in particular use an Archimedean cam, for the second cam and for the additional cam, despite the drawbacks noted above, the principle of the invention remaining unchanged in this case. Likewise, the geometry illustrated and described for the lever is preferred because it presents a good comprise between its bulk and its equilibrium from an inertial perspective. The form of the lever in particular enables a near-alignment between the tip  26  of the sensor, the axis of rotation  12  of the first cam  10  and the region in which the rack  27  and the pinion  28  are engaged. Moreover, this geometry makes it possible to arrange the axis of rotation of the lever in the immediate vicinity of the cam while also having the possibility of applying the force of the spring near this same axis. Thus, it is possible to apply a significant return force on the lever, while also greatly limiting the amplitude of the deformations of the spring. However, one skilled in the art may choose a different lever geometry depending on his own needs. 
     As an example, one skilled in the art will not encounter any particular difficulties in adapting this teaching to his own needs, in particular to display time sizes other than the hour, without going outside the scope of the present invention.