Device for controlling at least two electronic and/or mechanical functions of a portable object

A device for controlling at least two electronic and/or mechanical functions of a portable object of small dimensions includes a control stem that is axially movable between at least a first and a second position. The control stem is provided at a first end with an actuation member, and is provided towards a second end with a position indexing plate arranged to cooperate with an elastic member in order to match each of the first and second positions of the control stem with one of the mechanical or electronic functions.

This application claims priority from European Patent Application No. 16202471.5 filed on Dec. 6, 2016, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention concerns a device for controlling at least two electronic and/or mechanical functions for a portable object of small dimensions. More precisely, the invention concerns such a device comprising a control stem provided with a mechanical position indexing device which makes it possible to match each electronic or mechanical function with a distinct position of the control stem.

BACKGROUND OF THE INVENTION

The present invention concerns the field of control stems which are fitted to portable objects of small dimensions, such as timepieces, and which are arranged to control one or more electronic and/or mechanical functions of such objects.

In a very simplified manner, control stems of this type comprise a cylindrical portion whose length is substantially greater than its diameter, and at one end of which, located outside the portable object, is fixed a crown enabling a user to actuate the control stem and to adjust the electronic or mechanical function or functions. In the case where these stems control several functions, each given function must be able to be matched with a determined position of the control stem.

An example of such a control stem is illustrated inFIG. 22, annexed to this patent application. Designated as a whole by the general reference numeral200, this control stem includes a cylindrical portion202which finishes with an actuation crown204at its end located outside the portable object (not represented) which is fitted with an actuation crown204. Towards its end opposite actuation crown204, cylindrical portion202of control stem200is provided with a cam path206formed of three successive annular grooves208a,208band208cseparated from each other by two flanges210aand210bof substantially rounded profiles. The dimensions of annular grooves208a-208care adapted to those of the elastic arms212of a spring214, for example, a U-shaped spring, which projects, for example, into annular groove208aof path cam206. It is understood that, in order to make elastic arms212of spring214move from annular groove208ainto annular groove208b, the user must exert on control stem200a traction force greater than the force necessary for elastic arms212to move apart and slide over flange210abefore closing again on annular groove208b. Conversely, if it is desired to move elastic arms212of spring214from annular groove208binto annular groove208a, a thrust force must be exerted on control stem200sufficient to enable elastic arms212to deform and cross flange210aand drop into annular groove208a. The same applies to the transition of elastic arms212of spring214from annular groove208binto annular groove208cand vice versa.

Thus, through cooperation between the elastic arms of a spring and a cam path which is integral with the cylindrical portion of a control stem, it is advantageously possible to define, for example, three stable positions of the control stem which each correspond to the adjustment of a given function. The drawback of this solution lies, however, in the fact that, in order to machine the cam path in the cylindrical portion of the control stem, the diameter of the cylindrical portion of the control stem must be relatively large, which makes the use of such a control stem quite difficult, or even impossible, especially in the field of wristwatches where it is not desired to machine large diameter holes in the case middle, in particular due to the thickness of the case middle.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the aforementioned problems, in addition to others, by providing a device for controlling at least two electronic and/or mechanical functions, comprising a stem whose diameter is sufficiently small for it to be usable notably in the field of horology.

To this end, the present invention concerns a device for controlling at least two electronic and/or mechanical functions of a portable object of small dimensions, this device comprising a control stem axially movable between at least a first and a second position, this control stem being provided, at a first end, with an actuation member, and being provided, towards a second end, with a position indexing plate arranged to cooperate with an elastic member in order to match each of the first and second positions of the control stem with one of the mechanical or electronic functions.

According to other features of the invention which form the subject of the dependent claims:the indexing plate extends substantially in a horizontal plane;the elastic member includes two elastic arms which cooperate with two identical cam paths provided in the position indexing plate to define the first and second position of the control stem;the two cam paths define one unstable position and one stable position of the control stem, or the two cam paths define a first and a second stable position of the control stem;in the case where the two cam paths define a first stable position and a second stable position of the control stem, the cam paths include a first recess separated from a second recess by a peak, the first and second recesses defining the first and second stable positions of the control stem, the elastic arms of the elastic member passing from the first recess to the second recess and vice versa by crossing the peak;in the case where the two cam paths define one stable position and one unstable position of the control stem, the cam paths include a recess which defines the stable position and which the elastic arms of the elastic member leave to engage on a ramp profile which moves the elastic arms away from their rest position and which defines the unstable position of the control stem;the position indexing plate is housed inside a groove provided in the control stem;the position indexing plate is integral with the control stem, or the position indexing plate is removably coupled to the control stem;in the case where the position indexing plate is removably coupled to the control stem, the coupling between the position indexing plate and the control stem is an elastic coupling arranged to prevent the uncoupling of the position indexing plate and the control stem in normal conditions of use.

As a result of these features, the present invention provides a device for controlling at least two electronic or mechanical functions whose dimensions are restricted, which makes it possible to install such a control device inside a portable object of small dimensions, such as in particular a wristwatch. In fact, the mechanical structure for indexing the position of the control stem is shifted from the actual control stem to a position indexing plate which is machined separately from the control stem. This plate is relatively thin and also extends in a substantially horizontal plane, whereas, when the mechanical, position indexing structure is arranged on the control stem, it necessarily increases the diameter of the control stem and therefore the height of the case middle of the portable object, so that the portable object is thicker, which is sought to be avoided, particularly in the field of timepieces.

Further, in the control device according to the invention, friction is virtually eliminated to limit wear to the maximum extent possible and ensure the greatest possible longevity of the control device. Further, the less friction there is, the easier it is to operate the control stem, in particular in the unstable pushed-in position. In order to minimize this friction, it is particularly important to note that none of the electrical contacts produced in the control device according to the invention are achieved by friction. The electrical contacts are all achieved by the abutment of one part against another. There is therefore much less wear than in the case of parts which rub against each other. The same is true of the position indexing plate, whose upward travel is limited by the limiting spring with which the position indexing plate, and therefore the control stem, is not, however, in contact in normal operating conditions. Here too, no friction is observed.

Finally, the fact that the control stem and the indexing plate are not inseparably mounted ensures the disassemblability of the control device, which is advantageous particularly in the case where the timepiece equipped with the control device according to the invention has a certain price.

It will also be noted that the electrical contacts produced in the control device according to the invention are all of the galvanic type, which means that in the absence of electrical contact, the control device has zero electricity consumption.

DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

The present invention proceeds from the general inventive idea which consists in transferring a position indexing mechanism for a stem controlling at least two electronic and/or mechanical functions of a portable object of small dimensions, such as a timepiece, from this control stem to a plate machined separately from said control stem. By doing so, it is possible to reduce the diameter of the control stem and thus concomitantly to reduce the thickness of the case middle of the portable object, such as a timepiece. This result is achieved as a result of the fact that, instead of being structured straight onto the control stem, the indexing mechanism, which typically takes the form of two cam paths cooperating with an elastic member, is made in a thin plate which forms a separate part from the control stem and which is mechanically coupled to the latter. As the control stem is without its indexing mechanism, its diameter can be reduced, and the small thickness of the position indexing plate of the invention does not result in any significant increase in the dimensions of the control stem of the invention.

In all that follows, the back-to-front direction is a rectilinear direction which extends horizontally along longitudinal axis of symmetry X-X of the control stem from the external actuation crown towards the interior of the portable object equipped with the control device, parallel to a plane in which a back of the portable object extends. Thus, the control stem will be pushed from back to front, and will be pulled from front to back. Further, the vertical direction is a direction that extends perpendicularly to the plane in which the control stem extends.

FIG. 1is a perspective view, in an unassembled state, of a device for controlling at least one electronic function of a portable object of small dimensions, such as a wristwatch. Designated as a whole by the general reference number1, this control device includes (seeFIG. 2) a lower frame2, made for example of an injected plastic material or of a non-magnetic metallic material such as brass. This lower frame2serves as a cradle for a control stem4preferably of elongated and substantially cylindrical shape, provided with a longitudinal axis of symmetry X-X (seeFIG. 3). This control stem4is arranged to slide from front to back and from back to front along its longitudinal axis of symmetry X-X and/or to rotate about said same axis of longitudinal symmetry X-X in the clockwise and anticlockwise direction.

At a rear end6, which will be located outside the portable object once the latter is equipped with a control device1, control stem4will receive an actuation crown8(seeFIG. 18).

At a front end10, which will be located inside control device1once the latter is assembled, control stem4has, for example, a square section12and receives in succession a magnetic assembly14and a smooth bearing16.

Magnetic assembly14includes a bipolar or multipolar magnetized ring18and a support ring20, on which magnetized ring18is fixed, typically by adhesive bonding (seeFIG. 4). Support ring20is a component of generally cylindrical shape. As seen inFIG. 5, support ring20has, from back to front, a first section22ahaving a first external diameter D1on which is engaged magnetized ring18, and a second section22bhaving a second external diameter D2greater than first external diameter D1and which delimits a shoulder24against which magnetized ring18abuts. The first section22aof support ring20is pierced with a square hole26which is adapted in shape and size to square section12of control stem4and forms with control stem4a sliding pinion type system. In other words, support ring20and magnetized ring18remain immobile when control stem4is made to slide axially. However, control stem4drives support ring20and magnetized ring18in rotation when control stem4is rotated. It is clear from the foregoing that magnetized ring18, carried by support ring20, is not in contact with control stem4which makes it possible to protect it in the event of shocks applied to the portable object equipped with a control device1.

Smooth bearing16defines (seeFIG. 5) a cylindrical housing28whose first internal diameter D3is very slightly greater than the diameter of the circle in which is inscribed square section12of control stem4, to allow control stem4to slide axially and/or to rotate inside this cylindrical housing28. Smooth bearing16thus ensures perfect axial guiding of control stem4.

It is noted that the square hole26provided in first section22aof support ring20is extended towards the front of control device1by an annular hole30whose second internal diameter D4is fitted onto third external diameter D5of smooth bearing16. Support ring20is thus fitted for free rotation on smooth bearing16and moves into axial abutment against smooth bearing16, which ensures the perfect axial alignment of these two components and makes it possible to correct any problems of concentricity that may be caused by a sliding pinion type coupling.

It is observed that, for axial immobilization thereof, smooth bearing16is provided on its outer surface with a circular collar32which projects into a first groove34aand into a second groove34b, respectively arranged in lower frame2(seeFIG. 2) and in an upper frame36(seeFIG. 6), arranged to cover lower frame2and, for example, made of an injected plastic material or of a non-magnetic metallic material, such as brass. These two lower and upper frames2and36will be described in detail below.

It is important to note that the magnetic assembly14and smooth bearing16described above are indicated purely for illustrative purposes. Indeed, smooth bearing16, for example made of steel or brass, is arranged to prevent control stem4, for example made of steel, rubbing against lower and upper frames2and36, and causing wear of the plastic material of which these two lower and upper frames2and36are typically made. However, in a simplified embodiment, it is possible to envisage not using such a smooth bearing16and arranging for control stem4to be directly carried by lower frame2.

Likewise, magnetized ring18, and support ring20on which magnetized ring18is fixed, are intended for the case where rotation of control stem4is detected by a local variation in the magnetic field induced by the pivoting of magnetized ring18. It is, however, entirely possible to envisage replacing magnetic assembly14, for example with a sliding pinion which, according to its position, will for example control the winding of a mainspring or the time-setting of a watch equipped with control device1.

It is also important to note that the example of control stem4provided on one part of its length with a square section is given purely for illustrative purposes. Indeed, in order to drive magnetic assembly14in rotation, control stem4may have any type of section other than a circular section, for example triangular or oval.

Lower frame2and upper frame36, the combined assembly of which defines the external geometry of control device1, are for example, of generally parallelepiped shape. Lower frame2forms a cradle which receives control stem4(seeFIG. 2). To this end, lower frame2includes, towards the front, a first receiving surface38of semicircular profile, which serves as a seat for smooth bearing16and in which is provided the first groove34awhich receives circular collar32. Both axial and rotational immobilization of smooth bearing1are thus ensured.

Lower frame2further includes, towards the back, a second receiving surface40, whose semicircular profile is centred on longitudinal axis of symmetry X-X of control stem4, but whose diameter is greater than that of control stem4. It is important to understand that control stem4only rests on second receiving surface40at the stage when the assembled control device1is tested prior to being integrated in the portable object. At this assembly stage, control stem4is inserted into control device1for test purposes and extends horizontally, supported and axially guided by smooth bearing16at its front end10and via second receiving surface40at its rear end6. However, once control device1is integrated in the portable object, control stem4passes through a hole42provided in case middle48of the portable object in which it is guided and supported (seeFIG. 19) and which is delimited downwardly by a bottom case49.

Third and fourth clearance surfaces44aand46aof semicircular profile are also provided in lower frame2and complementary clearance surfaces44band46b(seeFIG. 6) are provided in upper frame36for receiving magnetic assembly14, formed of magnetized ring18and of its support ring20. It will be noted that magnetized ring18and its support ring20are not in contact with third and fourth clearance surfaces44aand46aand complementary clearance surfaces44band46bwhen control device1is assembled and mounted in the portable object. It is also noted that third clearance surface44aand its corresponding complementary clearance surface44bare delimited by a circular collar50for axially locking magnetic assembly14.

As visible inFIG. 3, behind square section12, control stem4has a cylindrical section52whose diameter is comprised between the diameter of the circle in which is inscribed square section12of control stem4and the primitive diameter of a rear section54of said control stem4, at the end of which is fixed actuation crown8. This cylindrical section52of reduced diameter forms a groove56inside which is placed a position indexing plate58for control stem4(seeFIGS. 7A and 7B). To this end, position indexing plate58has a curved portion60which follows the profile of reduced diameter cylindrical section52and which allows position indexing plate58to extend substantially horizontally. Position indexing plate58may be, for example, obtained by stamping a thin, electrically conductive metal sheet. However, it is also possible to envisage making position indexing plate58, for example, by moulding a hard plastic material loaded with conductive particles. The engagement of position indexing plate58in groove56ensures the coupling in translation, from front to back and from back to front, between control stem4and position indexing plate58. However, as will become clearer below, position indexing plate58is free with respect to control stem4in a vertical direction z perpendicular to the longitudinal axis of symmetry X-X of control stem4.

As visible inFIG. 7A, position indexing plate58is a substantially flat and generally U-shaped part. This position indexing plate58includes two substantially rectilinear guide arms62which extend parallel to each other and which are connected to each other by curved portion60. These two guide arms62are axially guided, for example, against two studs64arranged in lower frame2. Guided by its two guide arms62, position indexing plate58slides along a rim68arranged in upper frame36and whose perimeter corresponds to that of position indexing plate58(seeFIG. 6). Position indexing plate58also includes two fingers66a,66bwhich extend vertically downwards on either side of the two guide arms62.

In sliding along rim68, position indexing plate58has the function of ensuring the translational guiding of control stem4from front to back and from back to front. Fingers66a,66b, are intended, in particular, to prevent position indexing plate58from bracing when the latter moves in translation.

Two apertures70exhibiting an approximately rectangular contour are provided in guide arms62of position indexing plate58. These two apertures70extend symmetrically on either side of longitudinal axis of symmetry X-X of control stem4. The sides of the two apertures70closest to longitudinal axis of symmetry X-X of control stem4have a cam path72of substantially sinusoidal shape, formed of a first and a second recess74a,74bseparated by a peak76.

The two apertures70provided in guide arms62are intended to receive the two ends78of a positioning spring80(seeFIG. 8). This positioning spring80is generally U-shaped with two arbors82which extend in a horizontal plane and which are connected to each other by a base84. At their free end, the two arbors82are extended by two substantially rectilinear arms86which stand upright. Positioning spring80is intended to be mounted in control device1through the bottom of lower frame2, so that ends78of arms86project into apertures70of position indexing plate58. It will be seen below that the cooperation between position indexing plate58and positioning spring80makes it possible to index the position of control stem4between an unstable pushed-in position T0and two stable positions T1and T2.

It was mentioned above that position indexing plate58is coupled in translation to control stem4, but that it is free with respect to control stem4in the vertical direction z. It is thus necessary to take steps to prevent position indexing plate58disengaging from control stem4in normal conditions of use, for example under the effect of gravity. To this end (seeFIG. 9), a spring88for limiting the displacement of position indexing plate58in vertical direction z is placed above and at a short distance from position indexing plate58. Displacement limiting spring88is captive between lower frame2and upper frame36of control device1, but is not, in normal conditions of use, in contact with position indexing plate58, which prevents parasitic friction forces being exerted on control stem4, which would make the latter difficult to operate and cause problems of wear. Displacement limiting spring88is, however, sufficiently close to position indexing plate58to prevent the latter being inadvertently uncoupled from control stem4.

Displacement limiting spring88includes a substantially rectilinear central portion90from the ends of which extend two pairs of elastic arms92and94. These elastic arms92and94extend on either side of central portion90of displacement limiting spring88, upwardly away from the horizontal plane in which central portion90extends. As these elastic arms92and94are compressed when upper frame36is joined to lower frame2, they impart elasticity to displacement limiting spring88along vertical direction z. Between the pairs of elastic arms92and94there is also provided one pair, and preferably two pairs, of stiff lugs96which extend perpendicularly downwards on either side of central portion90of displacement limiting spring88. These stiff lugs96which move into abutment on lower frame2when upper frame36is placed on lower frame2, ensure that a minimum space is provided between position indexing plate58and displacement limiting spring88in normal operating conditions of control device1.

Displacement limiting spring88guarantees the disassemblability of control device1. Indeed, in the absence of displacement limiting spring88, position indexing plate58would have to be made integral with control stem4and, consequently, control stem4could no longer be dismantled. If control stem4cannot be dismantled, the movement of the timepiece equipped with control device1cannot be dismantled either, which is not conceivable, particularly in the case of an expensive timepiece. Thus, when control device1, formed by joining lower and upper frames2and36, is mounted inside the portable object and control stem4is inserted into control device1from outside the portable object, control stem4slightly lifts position indexing plate58against the elastic force of displacement limiting spring88. If control stem4continues to be pushed forwards, there comes a moment when position indexing plate58drops into groove56under the effect of gravity. Control stem4and position indexing plate58are then coupled in translation.

A disassembly plate98is provided to allow disassembly of control stem4(seeFIG. 10). This disassembly plate98is generally H-shaped and includes a straight segment100which extends parallel to longitudinal axis of symmetry X-X of control stem4and to which a first and a second crosspiece?102and104are attached. The first crosspiece102is also provided at its two free ends with two lugs106folded up substantially at right angles. Disassembly plate98is received inside a housing108provided in lower frame2and located underneath control stem4. This housing108communicates with the outside of control device1via a hole110which opens into a lower face112of control device1(seeFIG. 11). By inserting a pointed tool into hole110, a thrust force can be exerted on disassembly plate98which, via its two lugs106, in turn pushes position indexing plate58against the elastic force of displacement limiting spring88. It is then sufficient to exert a slight traction on control stem4in order to extract the latter from control device1.

From its stable rest position T1, control stem4can be pushed forwards into an unstable position T0or pulled out into a stable position T2. These three positions T0, T1and T2of control stem4are indexed by cooperation between position indexing plate58and positioning spring80. More precisely (seeFIG. 12A), the stable rest position T1corresponds to the position in which ends78of arms86of positioning spring80project into first recesses74aof the two apertures70provided in guide arms62of position indexing plate58. From this stable rest position T1, control stem4can be pushed forwards into an unstable position T0(seeFIG. 12B). During this displacement, ends78of arms86of positioning spring80leave first recesses74aand follow a first ramp profile114which gradually moves away from longitudinal axis of symmetry X-X of control stem4along a first steep slope α (seeFIG. 7B). To force ends78of arms86of positioning spring80to leave first recesses74aand to engage on first ramp profile114by moving away from each other, the user must therefore overcome a significant resistance force.

When they reach a transition point116, ends78of arms86engage on a second ramp profile118which extends first ramp profile114with a second slope β lower than first slope α of first ramp profile114. At the instant that ends78of arms86of positioning spring80cross transition point116and engage on second ramp profile118, the force required from the user to continue moving control stem4drops sharply and the user feels a click indicating the transition of control stem4between position T1and position T0. As they follow second ramp profile118, arms86of positioning spring80continue to move slightly away from their rest position and tend to try to move towards each other again under the effect of their elastic return force opposing the thrust force exerted by the user on control stem4. As soon as the user releases pressure on control stem4, arms86of positioning spring80will spontaneously return down first ramp profile114and their ends78will lodge again inside first recesses74aof the two apertures70provided in guide arms62of position indexing plate58. Control stem4is thus automatically returned from its unstable position T0to its first stable position T1.

First and second contact springs120aand120bare arranged compressed inside a first and a second cavity122aand122bprovided in lower frame2. These first and second contact springs120aand120bcould be helical contact springs, strip-springs or other springs. The two cavities122a,122bpreferably, but not necessarily, extend horizontally. Because the two contact springs120a,120bare installed in the compressed state, their positioning precision is dependent on the manufacturing tolerance of lower frame2. The manufacturing precision of lower frame2is higher than the manufacturing precision of these two first and second contact springs120a,120b. Consequently, the precision of detection of position T0of control stem4is high.

As visible inFIGS. 13 and 15, one of the ends of first and second contact springs120a,120bis bent to form two contact lugs124which will move into abutment on two corresponding first contact pads126provided at the surface of a flexible printed circuit sheet128. The moment that ends78of arms86of positioning spring80engage on second ramp profile118of the two apertures70provided in position indexing plate58coincides with the moment that fingers66a,66bof position indexing plate58come into contact with first and second contact springs120a,120b. Since this position indexing plate58is electrically conductive, when fingers66a,66bcome into contact with first and second contact springs120a,120b, the electric current passes through position indexing plate58and closure of the electrical contact between first and second contact springs120a,120bis detected.

First and second contact springs120a,120bare of the same length. However, preferably, one of the first and second cavities122a,122bwill be longer than the other, in particular to take account of tolerance problems (the difference in length between the two cavities122a,122bis several tenths of a millimetre). Thus, when control stem4is pushed forwards into position T0, finger66aof position indexing plate58, which is lined up with first contact spring120ahoused inside the first, longest cavity122a, will come into contact with and start to compress first contact spring120a. Control stem4will continue to move forward and second finger66bof position indexing plate58will come into contact with second contact spring120bhoused inside the second, shortest cavity122b. At that moment, position indexing plate58will be in contact with first and second contact springs120a,120band the electric current will flow through position indexing plate58, which allows the closure of the electrical contact between the first two contact springs120a,120bto be detected. It is noted that fingers66a,66bof position indexing plate58move into abutment contact with first and second contact springs120a,120b. There is thus no friction or wear when control stem4is pushed forwards into position T0and closes the circuit between first and second contact springs120a,120b. It is also noted that, the difference in length of first and second cavities122aand122bensures that closure of the electrical contact and entry of the corresponding command into the portable object equipped with control device1occur only after a click is felt.

When the two fingers66a,66bof position indexing plate58are in contact with first and second contact springs120a,120b, first contact spring120ahoused inside first, longest cavity122ais in a compressed state. Consequently, when the user releases pressure on control stem4, this first contact spring120arelaxes and forces control stem4to return from its unstable pushed-in position T0to its first stable position T1. The first and second contact springs120a,120bthus act simultaneously as electrical contact parts and elastic return means for control stem4in its first stable position T1.

From first stable position T1, it is possible to pull control stem4backwards into a second stable position T2(seeFIG. 12C). During this movement, ends78of arms86of positioning spring80will elastically deform to pass from first recesses74ato second recesses74b, crossing peaks76of the two apertures70provided in guide arms62of position indexing plate58. When control stem4reaches its second stable position T2, the two fingers66a,66bof position indexing plate58move into abutment against third and fourth contact springs130a130b(seeFIG. 13), which are housed inside third and fourth cavities132a,132bprovided in lower frame2. These third and fourth contact springs130a,130bcould be helical contact springs, strip-springs or other springs. Third and fourth cavities132a,132bpreferably extend vertically for reasons of space in control device1. Since position indexing plate58is electrically conductive, when fingers66a,66bcome into contact with third and fourth contact springs130a,130b, the electric current flows through position indexing plate58and closure of electrical contact T2between these contact springs130a,130bis detected.

It will be noted that, in the case of stable position T2, fingers66a,66bof position indexing plate58also come into abutment contact with third and fourth contact springs130a,130b, thereby avoiding any risk of wear from friction. Further, third and fourth contact springs130a,130bare capable of bending when fingers66a,66bof position indexing plate58collide therewith, and therefore of absorbing any lack of precision in the positioning of position indexing plate58.

Preferably, but not necessarily, third and fourth contact springs130a,130bare arranged to work in flexion. Indeed, with contact springs130a,130bwhose diameter is constant, fingers66a,66bof position indexing plate58come into contact with contact springs130a,130bover a large surface close to their points of attachment in lower frame2and upper frame36. The proximity of the contact surface to the attachment points of contact springs130a,130binduces shearing stresses in contact springs130a,130bwhich may lead to premature wear and breakage of the latter. To overcome this problem, contact springs130a,130bhave, preferably substantially at mid-height, an increase in diameter134which comes into contact with fingers66a,66bof position indexing plate58when control stem4is pulled into its stable position T2(seeFIGS. 14A and 14B). At their upper end, third and fourth contact springs130a,130bare guided in two holes136provided in upper frame36and come into contact with second contact pads138provided at the surface of flexible printed circuit sheet128. It is clear that, when control stem4is pulled backwards into its stable position T2, fingers66a,66bof positioning indexing plate58come into contact on a reduced surface with third and fourth contact springs130aand130bat their largest diameter134, which allows contact springs130a,130bto bend between their two points of attachment in lower frame2and upper frame36.

InFIG. 15, lower and upper frames2and36have been deliberately omitted to facilitate understanding of the drawing. As represented inFIG. 15, flexible printed circuit sheet128is fixed on a plate140located on the dial side of the portable object. It includes, in particular, of a cutout142adapted in shape and size to receive upper frame36. One portion144of flexible printed circuit sheet128remains free (seeFIG. 16). This free portion144of flexible printed circuit sheet128carries a plurality of electronic components146, in addition to third contact pads148, on which are fixed at least two inductive sensors150. An ‘inductive sensor’ means a sensor that transforms a magnetic field passing therethrough into electric voltage due to the phenomenon of induction defined by Lenz's law and Faraday's law. By way of example, this may be a Hall effect sensor or a magnetoresistance component of the AMR (anisotropic magnetoresistance), GMR (giant magnetoresistance) or TMR (tunneling magnetoresistance) type.The free portion144of flexible printed circuit sheet128is connected to the rest of flexible printed circuit sheet128by two strips152, which allow free portion144to be folded around the assembly of upper frame36and lower frame2, and then folded down against a lower surface112of lower frame2, so that inductive sensors150penetrate two housings156provided in lower surface112of lower frame2. Thus positioned inside their housings156, inductive sensors150are precisely located under magnetized ring18, which ensures reliable detection of the direction of rotation of control stem4. Once free portion144of flexible printed circuit sheet128has been folded down against lower frame2(seeFIG. 17A), the assembly is covered by a holding plate158, provided with one or two elastic fingers160, which press inductive sensors150against the bottom of their housings156(see FIG.17B). Holding plate158is fixed to plate140, for example by means of two screws162.

It goes without saying that the present invention is not limited to the embodiment that has just been described and that various simple modifications and variants can be envisaged by those skilled in the art without departing from the scope of the invention as defined by the annexed claims. In particular, the dimensions of the magnetized ring may be extended so that it corresponds to a hollow cylinder. It will be understood, in particular, that position indexing plate58may define only two distinct positions, namely two stable positions or one stable position and one unstable position, or it may define three or more distinct positions, namely at least three stable positions or at least two stable positions and one unstable position.

FIG. 20Aillustrates the case where position indexing plate58defines only two stable positions. In such case, two apertures70-1exhibiting an approximately rectangular contour are provided in guide arms62of position indexing plate58. These two apertures70-1extend symmetrically on either side of longitudinal axis of symmetry X-X of control stem4. The sides of the two apertures70-1closest to longitudinal axis of symmetry X-X of control stem4have a cam path72-1of substantially sinusoidal shape, formed of a first and a second recess74a-1,74b-1separated by a peak76-1. The two apertures70-1provided in guide arms62are intended to receive the two ends78of the arms of positioning spring80in order to index the position of control stem4between a first and a second stable position T1-1and T2-1.

More precisely, the first stable position T1-1corresponds to the position in which ends78of arms86of positioning spring80project into first recesses74a-1of the two apertures70-1provided in guide arms62of position indexing plate58. From this first stable position T1-1, control stem4can be pulled back into a second stable position T2-1. During this movement, ends78of arms86of positioning spring80will elastically deform to pass from first recesses74a-1to second recesses74b-1, crossing peaks76-1of the two apertures70-1provided in guide arms62of position indexing plate58.

FIG. 21Aillustrates the case where indexing plate58defines only one stable position T1-2and one unstable position T0-2. In such case, two apertures70-2exhibiting an approximately rectangular contour are provided in guide arms62of position indexing plate58. These two apertures70-2extend symmetrically on either side of longitudinal axis of symmetry X-X of control stem4. The sides of the two apertures70-2closest to longitudinal axis of symmetry X-X of control stem4have a cam path72-2formed of a recess74a-2followed by a ramp profile114-2which gradually moves away from longitudinal axis of symmetry X-X of control stem4on a first steep slope α-2. To force ends78of arms86of positioning spring80to leave recesses74a-2and to engage on first ramp profile114-2by moving away from each other, the user must therefore overcome a significant resistance force. When they reach a transition point116-2, ends78of arms86engage on a second ramp profile118-2which extends first ramp profile114-2with a second slope β-2lower than first slope α-2of first ramp profile114-2. At the instant that ends78of arms86of positioning spring80cross transition point116-2and engage on second ramp profile118-2, the force required from the user to continue moving control stem4drops sharply and the user feels a click indicating the transition of control stem4between its stable position T1-2and its unstable position T0-2. As they follow second ramp profile118-2, arms86of positioning spring80continue to move slightly away from their rest position and tend to try to move towards each other again under the effect of their elastic return force opposing the thrust force exerted by the user on control stem4. As soon as the user releases pressure on control stem4, arms86of positioning spring80will spontaneously move back down first ramp profile114-2and lodge again inside recesses74a-2of the two apertures70-2provided in guide arms62of position indexing plate58. Control stem4is thus automatically returned from its unstable position T0-2to its stable position T1-2.

NOMENCLATURE