DRIVE ORGAN FOR CLOCK

Description

Technical field

[0001] The present invention relates to the field of watchmaking. It relates, more particularly, to a watch movement comprising a compact driving member. State of the art

[0002] Currently, the most commonly used driving force in mechanical timepieces is the barrel. Typically, a barrel comprises a hollow drum comprising a cylindrical wall closed on one side by a base made in one piece with it, and on the other side by a cover, in order to form a housing for a spiral spring. The outer end of the spiral spring is connected by a fixed or sliding flange to the cylindrical wall of the drum, and the inner end of the spring is connected to a bung associated with a barrel arbor. The outer wall of the drum is typically provided with teeth in order to drive a going train, and the arbor is secured to a ratchet wheel, which is used for winding the spring. It is also known to drive the going train via the arbor and to wind the spring via the drum.Furthermore, smooth drums, without teeth, are known, which drive the finishing gear by means of a chain and a spindle system.

[0003] The conventional barrel mentioned above is mounted on the frame by its center, namely directly or indirectly via the shaft. This arrangement is relatively bulky, and requires a certain height between the frame elements located on either side of the barrel to ensure that the barrel does not come into contact with neighboring components.

[0004] Solutions to this problem have already been proposed in the prior art. For example, patent CH26510 omits the drum cover, the housing for the spring being delimited on one side by the bottom of the drum, and on the other side by a frame element of the movement, in particular the plate.

[0005] An even more compact solution has been proposed in document CH 46863. The driving member of this document proposes a drum also closed on one side by a frame element, in which the shaft came from a piece with a wheel which is located entirely in the thickness of this frame element, in a recess provided in the latter.

[0006] The drums of all the embodiments mentioned above are supported by their center, which requires that the drum has a bottom secured to its side wall. Document CH 334702 discloses several variants of barrels in which the drum consists of a ring guided at its peripheral wall by means of three pairs of rollers distributed around the periphery of the drum. This drum has neither cover nor bottom, and the housing for the mainspring is defined on its lower and upper faces by bridges of the movement frame.

[0007] Although the barrels revealed in this latest document result in a significant reduction in height compared to a conventional barrel, the use of pairs of rollers located around the drum increases the diameter of the barrel, and increases the complexity of the driving organ. Furthermore, the rollers are rotating, and therefore require rotation axes. There are therefore four axes (the shaft and those of the three pairs of rollers) which must be well aligned when mounting the barrel bridge on the plate, which makes its assembly somewhat difficult.

[0008] Finally, document FR 2229087 discloses a driving member in which the drum is supported radially by a recess made in the bottom of the housing, this bottom serving as a frame element. The drum is open on both sides, and the housing thus defined to house the spring is closed on the one hand by the bottom and on the other hand by the toothed wheel. This arrangement is even simpler and more compact than those mentioned above, but the toothed wheel is supported on both sides. The compactness of the driving member as well as its simplicity can therefore be further improved.

[0009] An aim of the invention is therefore to propose a watch movement comprising a driving member in which the aforementioned defects are at least partially overcome. Disclosure of the invention

[0010] More specifically, the invention relates to a watch movement for a timepiece, comprising a driving member which comprises a mainspring such as a spiral spring, and a drum delimiting an outer wall of a housing housing said mainspring. The outer end of the mainspring is connected to the drum, which is arranged to pivot about an axis of rotation. Furthermore, the drum has the shape of a toothed annular crown.

[0011] The drive member further comprises a toothed wheel, which can for example serve as a ratchet wheel, secured to a plug to which an inner end of said drive spring is connected.

[0012] One face of said housing is intended to be defined by a fixed element of said timepiece against which said drum is intended to be mounted, such as a frame element, a back, or a crystal.

[0013] According to the invention, said bung and said toothed wheel are made in one piece. This construction results in a significant reduction in space requirement compared to the barrels of the prior art. The combination of a toothed wheel made in one piece with the bung (and therefore compact) with a drum formed by a toothed annular crown and therefore lacking not only a cover but also a base, allows for a very slim construction. The separate bung is thus made superfluous, which reduces the number of parts. Furthermore, the fact that the toothed wheel and the bung are manufactured in one piece allows the wheel to be brought closer to the drum, without having to leave space to compensate for the tolerances required when using two separate parts secured to each other.

[0014] Furthermore, the drum is supported by a ball bearing. The friction experienced by the drum during its rotations can therefore be minimized, while keeping the thickness of the driving member to a minimum. The ball bearing can be bidirectional or unidirectional. This latter possibility allows the drum to function as a ratchet, without requiring any pawl, in the case where the driving member is wound up by the drum.

[0015] More particularly, said ball bearing comprises a first groove located on the outer wall of said drum and a second groove opposite said first groove, said second groove being located on the inner wall of an outer ring arranged to be fixed to said fixed element, the grooves thus defining an annular cavity. A plurality of balls are housed in this annular cavity. A compact construction is thus provided.

[0016] Advantageously, said drum and said motor spring can come in one piece, which reduces the number of parts of the motor unit and facilitates its assembly.

[0017] Advantageously, said watch movement comprises said fixed element.

[0018] Advantageously, said toothed wheel may be pivotally mounted on a fixed shaft extending from the fixed element or the barrel bridge.

[0019] Advantageously, said fixed element may be a frame element of a watch movement of said timepiece such as a plate or a bridge, or a glass that a timepiece comprises on the back side or dial side, or a back that said timepiece comprises.

[0020] In the case where the fixed element is a glass of the timepiece, said barrel bridge may be integrated into a frame element or a back that said timepiece comprises. Brief description of the drawings

[0021] Other details of the invention will appear more clearly on reading the following description, given with reference to the appended drawings in which: There figure 1 is a sectional view of a first variant of a motor member not forming the subject of the invention; The figure 2 is an enlarged view of the left half of the figure 1 ; There figure 3 is a perspective view of the motor organ of the figure 1 ; There figure 4 represents the barrel bridge in perspective, seen from both sides; The Figure 5 represents the drum in perspective, seen from both sides; The figure 6 represents a part of the frame element on which the driving member of the figure 1 is mounted; The figure 7 represents the cogwheel of the first variant in perspective, seen from both sides; The figure 8 is a sectional view of a second variant of a motor member not forming the subject of the invention; The figure 9is an enlarged view of the left half of the figure 7 ; There figure 10 is an exploded view of said second variant of a motor member; The figure 11 is a perspective view of a variant of the drum and mainspring; The figure 12 is a cutaway perspective view of a variant of a motor member according to the invention; The figure 13 is an enlarged view of a detail of the figure 12 ; There figure 14 is a plan view of the variant of the figure 12 ; There figure 15 is a perspective view of yet another variant of a motor member not forming the subject of the invention; and The figure 16 is a sectional view of the variant of the figure 15 . Embodiments of the invention

[0022] THE figures 1 to 7represent a first variant of a driving member 1 not forming the subject of the invention, which has been provided by way of example. The driving member 1 is mounted on a fixed element 3 of a timepiece in which the driving member is implemented. This fixed element 3 may be a plate or a bridge, or a back on which the driving member 1 is directly or indirectly mounted.

[0023] The driving member comprises a drum 5 having peripheral teeth 6. This drum 5 is devoid of cover and bottom, and defines a cylindrical housing in which a driving spring 7 is arranged. The latter is of conventional spiral shape, and is connected at its outer end to the inner wall of the drum 5, and at its inner end to a bung 9. The latter comes in one piece with a toothed wheel 11 which serves as a ratchet wheel in the illustrated embodiment, but which can also be used for driving the cogs, the drum 5 serving as a ratchet in such a case. The toothed wheel 11 extends superimposed on the spring 7, and serves as a barrel cover, but the bung may be made of a separate part secured to the toothed wheel 11. The bung 9 is pivoted around a fixed shaft 13, and is held on the latter by means of a screw 15 or similar which bears against the fixed shaft 13. As best seen in the figure 7the plug 9 comprises a hook 9a for connection with the inner end of the mainspring 7 formed directly in the plug 9, for example by means of wire EDM or sinking. Alternatively, it can be produced by conventional broaching or milling.

[0024] The toothed wheel 11 acts as a cover for the barrel, which is not rotationally fixed to the drum 5, as known for example in document CH 28684.

[0025] On its side opposite the toothed wheel 11, the barrel is closed by a surface of the fixed element 3. The drum 5 as such is devoid of a bottom and a cover, and is only a simple toothed ring.

[0026] The drum 5 is positioned axially and radially by guide elements 17 distributed around the periphery of the drum 5. As best seen in the figures 3 And 4, these guide elements 17 are, in the variant shown, studs, made here in the form of stones, driven into a barrel bridge 19, and which abut against a shoulder 21 provided on the drum 5. An advantage of using stones, such as rubies, for the studs is the low coefficient of friction of this material, but other materials are possible. For example, the studs 17 can be made of hard metal, polymer or ceramic, and, in the case of metal, can be made of the same material as the barrel bridge 19. Alternatively, the studs can be replaced by a continuous or discontinuous surface of the barrel bridge 19, or by ball bearings. The studs 17 extend from the barrel bridge 19 in a direction parallel to the axis of rotation of the drum 5, and do not extend radially beyond the peripheral toothing 6 of the drum 5.In fact, the guide elements 17 are inscribed in the diameter of the drum 5, which reduces the space requirement in the plane of the drum 5 compared to the aforementioned document CH 334702.

[0027] In principle, the drum 5 can simply abut against the surface of the fixed element 3 and slide on the latter during its pivoting. However, in order to reduce friction, the drum 5 has guide stones 23 driven into corresponding housings and extending in the direction of the fixed part 3. These guide stones reduce the contact surface between the drum 5 and the fixed part 3 as well as the coefficient of friction.

[0028] The barrel bridge 19 also includes a winding pawl 25 which cooperates in a known manner with the teeth of the toothed wheel 11. Furthermore, the lower face of the barrel bridge 19 includes a recess 27 which serves to allow a wheel of the finishing train (not illustrated) to mesh with the peripheral teeth 6 of the drum 5.

[0029] The barrel bridge 19 is fixed to the fixed element 3 by means of screws 29 engaged in threaded tubes 31, which extend projecting from the upper face of the fixed element 3. These tubes 31 serve as centering studs for the barrel bridge 19, and ensure its positioning on the fixed element 3. Alternatively, the bridge can be fixed to the fixed element 3 by means of other fixing methods such as clipping, riveting or gluing.

[0030] THE figures 8 to 10illustrate a second variant of a motor member 1 not forming the subject of the invention. This variant differs from that of figures 1 to 7 mainly in that its construction is the reverse of that of the latter.

[0031] In this variant, the fixed element 3 is a crystal, which can be located either on the dial side or on the back side, and delimits the housing of the mainspring 7 on one of its sides. The barrel bridge 19 can be a separate element, secured to the plate or the back, or can come in one piece with one of the latter. The term "bridge" used rather means a functional part of the structure of the driving member 1 which can be part of another element such as a plate or a back

[0032] The barrel bridge 19 of this variant comprises a hollow 20 in its bottom, in which the toothed wheel 11 is located, which is pivoted around a fixed shaft 13 which said bridge 19 comprises. The axial positioning of the toothed wheel 11 is ensured on one side by a stop 33, and on the other side by the crystal 3.

[0033] The drum 5 is superimposed on the toothed wheel 11, and is guided in rotation and axially by guide elements 17 similar to those of the first variant, and which also extend from the barrel bridge 19 in the direction of the fixed element 3 in a direction parallel to the axis of rotation of the drum 5. As for the other variant, the guide elements 17 cooperate with the shoulder 21 located on the drum 5 in order to ensure the positioning of the latter.

[0034] The guide elements 17 are located in blind holes 35 which are deeper than necessary to receive the guide elements 17 in order to allow the watchmaker to adjust the height of the latter as required. Alternatively, the blind holes 35 may have a sufficient depth to receive the guide elements 17 to the bottom of the holes 35.

[0035] On the other face of the drum 5, the latter is simply guided by the fixed element 3 against which the drum 5 abuts. Nevertheless, it is possible to envisage providing guide stones 23 in the drum which extend in the direction of the ice 3 in a manner similar to the variant of figures 1 to 7 .

[0036] The assembly of this variant is carried out in the following order: mounting the toothed wheel 11 on the fixed axle 13; mounting the drum 5 superimposed on the toothed wheel 11; mounting the motor spring 7 in the drum 5 and hooking it onto the plug 9 of the toothed wheel 11; mounting the glass.

[0037] In a variant not shown, the axial positioning of the toothed wheel 11 can be ensured not by the glass 3, but by the drum 5 which can serve as an axial stop.

[0038] There figure 11illustrates a variant of the drum 5 and the mainspring 7 which can be implemented in connection with all the aforementioned embodiments. The drum 5 as well as the mainspring 7 form a single-piece assembly. The inner end of the mainspring 7 also comprises a ferrule 7a allowing a kinematic connection with the toothed wheel 11, but this ferrule 7a can of course be omitted. In the example illustrated, the ferrule comprises a polygonal opening, but other known shapes are also possible. A mainspring 7 of this type can be made of metal, or of a silicon-based material (for example amorphous, monocrystalline or polycrystalline silicon, its mono- or polycrystalline oxide, carbide or nitride), alumina, polymer, a composite or the like.

[0039] Since the construction of the illustrated motor member 1 includes numerous contact surfaces between moving parts, it could be advantageous to provide fine polishing or diamond plating of the contact surfaces, or to carry out a surface treatment such as DLC (diamond-like carbon) deposition, nanostructuring, teflon plating, electroplating or ion implantation on one or more surfaces intended to undergo friction.

[0040] THE figures 12 to 14 illustrate a variant of a motor member 1 according to the invention. In this variant, the toothed wheel 11 is supported on a fixed shaft 13 in a similar manner to the variant of figures 1 to 3 , and the housing for the mainspring is defined on its two faces by the toothed wheel 11 as well as a fixed element 3 of the timepiece, such as a frame element.

[0041] However, the drum 5 is held in its axial and radial positions by means of a ball bearing 37. This ball bearing 37 consists of a first groove 38a provided on the outer wall of the drum 5, and a second groove 38b formed in the inner face of an outer ring 39. The two grooves 38a, 38b are opposite each other in order to define a cavity, and balls (not illustrated) take place in this cavity in a generally known manner.

[0042] In the illustrated variant, the first groove 38a is formed by a first beveled surface 5a provided on the outer face of the drum 5, which is adjacent to a second beveled surface 41a with which an inner ring 41 is provided. The latter is driven, glued, welded or otherwise secured to the outer face of the drum 5, but it is also possible to form the first groove 38a directly in the body of the drum 5, which would therefore be in one piece.

[0043] The outer ring 39 is held in place by a bridge 19 as well as screws 43, which hold it against a shoulder 45 provided on the fixed element 3 to which it is thus fixed.

[0044] The drum 5 is thus suspended by the ball bearing 37, and does not come into contact with either the fixed element 3 or the toothed wheel 11. Consequently, and unlike the other variants described above, no additional guide member is necessary. The friction experienced by the drum during its pivoting can thus be reduced to a minimum value. Furthermore, this variant has an exceptionally thin thickness.

[0045] THE figures 12 to 14 also illustrate the arrangement of the gears with the toothed wheel 11 and with the drum 5. A return 47 is clearly seen which is in the same plane as the toothed wheel 11 and meshes with the latter, as well as another return 49 which is in the same plane as the teeth 6 of the drum 5 and also meshes with it. The returns 47, 49 therefore pass on either side of the outer ring 39.

[0046] This arrangement still presents further possibilities for other construction variants. Firstly, the same considerations with respect to the configuration of the mainspring 7 set out above (one-piece spring with the drum 5, conventional spring, etc.) also apply here. It is also possible to wind the motor member by its drum 5 and to use the toothed wheel 11 as a power take-off for the movement.

[0047] In the latter case, if the ball bearing 37 is of the unidirectional type, the driving member can be wound up by the drum 5 without requiring any pawl, thus reducing the number of components used in the construction. Furthermore, this arrangement eliminates over-tensioning when winding the mainspring 7 by the dead angle of a unidirectional bearing.

[0048] THE figures 15 to 16illustrate an additional variant of a motor member 1 not forming the subject of the invention. This variant differs from that of the figures 1 to 7 mainly in that the drum 5 is positioned radially by guide elements carried or made of the same material as the fixed element 3, and axially on the one hand by the fixed element 3, on the other hand by the toothed wheel 11.

[0049] More precisely, the fixed element 3 comprises a hollow 22 in which the drum 5 is placed. The side wall 22a of this hollow 22 forms a guide element making it possible to position the drum 5 radially and to limit the position of the drum 5 axially in a first direction. Other forms of guide elements are also possible, such as for example studs integral with the fixed element 3 which take place in a circular groove provided in the lower face of the drum 5 or vice versa, or a system of one or more circular grooves or rails distributed between the fixed element 3 and the drum 5, which interact for the same purpose.

[0050] In the illustrated variant, the drum 5 simply abuts against the surface of the fixed element 3 and slides on the latter during its pivoting. However, it is also possible to provide guide members 17 such as stones on the drum 5 or on the fixed element 3, or to arrange a ball bearing in the underside of the drum 5 in order to reduce friction.

[0051] In the direction opposite to the axial stop defined by the hollow 22 of the fixed element 3, the axial displacement of the drum 5 is limited by the toothed wheel 11. The latter is supported on a fixed shaft 13 in a similar manner to the variant of figures 1 to 3, and said toothed wheel 11 has an external diameter large enough to cover or overlap, at least partially, an area of ​​the drum 5. This at least partial covering makes it possible to define a second axial stop for the drum 5 in the direction opposite to the axial stop previously defined by the hollow of the fixed element 3. In other words, the drum 5 is held sandwiched between the fixed element 3 and the toothed wheel 11.

[0052] Advantageously, this variant offers a reduced number of parts and eliminates the need for a barrel bridge.

[0053] Although the invention has been described in connection with particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention as defined by the claims.

Claims

1. A timepiece movement for a timepiece, comprising a driving member comprising : - a mainspring (7); - a drum (5) delimiting an outer wall of a housing accommodating said mainspring (7), an outer end of said mainspring (7) being connected to said drum (5), said drum (5) being arranged to pivot about an axis of rotation and having the shape of a toothed annular crown; - a toothed wheel (11) integral with a core (9) to which an inner end of said mainspring (7) is connected; wherein an open face of said housing is intended to be closed by being positioned facing a fixed element (3) of the timepiece against which said drum (5) is intended to be mounted, characterized in that said core (9) and said gear wheel (11) are monobloc, and in that said drum (5) is supported by a ball bearing (37) comprising a first groove (38a) located on the outer wall of said drum and a second groove (38b) facing said first groove (38a), said second groove (38b) being located on the inner wall of an outer ring (39) arranged to be fixed to said fixed element (3), a plurality of balls being housed in the cavity formed by said grooves (38a, 38b).

2. Timepiece movement (1) according to claim 1, wherein said drum (5) and said mainspring (7) are monobloc.

3. Timepiece movement according to one of claims 1 or 2, wherein said gearwheel (11) is pivotally mounted on a fixed shaft (13) extending from one of the fixed element (3) or barrel bridge (19).

4. Timepiece movement according to one of claims 1 to 3, wherein said fixed element (3) is a frame element of said movement.

5. Timepiece comprising a timepiece movement according to one of claims 1 to 4.

6. Timepiece according to claim 5 wherein said fixed element is a glass (3) comprised by said timepiece or a back cover comprised by said timepiece.