CLOCKWORK MECHANISM COMPLETING A DRIVE DEVICE FOR TURNING ONE ORGAN BY ANOTHER

Description

[0001] The present invention relates to a clockwork mechanism comprising at least two organs and a device for driving one of said organs in rotation by the other comprising a male element carried by one of said organs and a female element carried by the other of said organs and arranged to cooperate with said male element.

[0002] Such a drive device is used for example to transmit torque from a ratchet to a barrel shaft, the male element being a square provided on the barrel shaft and the female element being a correspondingly shaped square hole, with the necessary clearance for assembly, cut into the ratchet plate and into which the square of the barrel shaft fits.

[0003] Using a square to transmit force between two components presents several drawbacks. In particular, a square has sharp edges, which can damage the interface between the two components, as contact occurs between edges and surfaces. Furthermore, the stresses associated with this edge-to-surface contact are concentrated at the interface. Consequently, when the torques at this interface are significant—for example, in the case of a mainspring barrel and ratchet wheel being wound during the winding of a timepiece to power it—the risk of breaking the barrel at the ratchet wheel is very high when the barrel is subjected to torsional stress from the ratchet. This risk is further increased when the diameter of the mainspring barrel is reduced.Furthermore, with a square assembly, the contact pressure at the interface between the two parts is significant, so it is not possible to use parts made of a fragile material, such as silicon or ceramic.

[0004] Furthermore, the square joint requires a lot of play, which leads to significant inaccuracies, detrimental in certain applications. This is why those skilled in the art avoid using a square joint to connect two components between which a torque must be transmitted.

[0005] In addition, a square male element requires quarter turns to index the female element, which will cause additional wear as one of the parts has to be rotated relative to the other until the assembly position is found.

[0006] The document discloses a coupling of a barrel arbor with a ratchet. The coupling consists of a male element with flats and a corresponding female element.

[0007] The present invention aims to remedy these drawbacks by proposing a device for rotating one part of a watch mechanism by another part, thereby improving the mechanical strength of the part subjected to torsion by the other part, in order to increase the torque transmitted before breaking.

[0008] The present invention also aims to provide a device for driving a component of a watch mechanism in rotation by another component which, in addition to increasing the torque transmitted before breaking, reduces the contact pressure at the interface in order to guarantee the integrity of the components.

[0009] For this purpose, the present invention relates to a clockwork mechanism according to claim 1.

[0010] The clock mechanism according to the present invention comprises at least two organs and a device for driving one of said organs in rotation by the other comprising a male element carried by one of said organs and a female element carried by the other of said organs and arranged to cooperate with said male element.

[0011] According to the invention, the male element has, in cross-section, a shape defining overall a first outer circle of outer diameter D and center C and comprising at least one hollow, symmetrical with respect to an axis passing through the center C of the outer circle, and directed towards the center C so as to be tangent to a second inscribed inner circle of center C and inscribed diameter d such that the difference between the outer diameter D and the inscribed diameter d is greater than or equal to 8% and strictly less than 20% of the outer diameter D.

[0012] Furthermore, according to the invention, the female element has, in cross-section, the same shape as that of the male element arranged to receive and cooperate with said male element in order to transmit a couple from one to the other of said organs.

[0013] The shape presented by the male and female elements according to the invention allows more torque to be transmitted from one organ to the other before breaking than a square.

[0014] In the context of the present invention, the hollow is circular and has a radius defining a pointing equal to the sum of the radius of the inner inscribed circle and the radius of the circular hollow, said pointing being less than 300% of the radius of the inner inscribed circle.

[0015] This shape presented by the male and female elements according to the invention also makes it possible to minimize the contact pressure at the interface of the organs, and thus to be able to use fragile materials for their construction.

[0016] The present invention also relates to a timepiece comprising a mechanism as defined above.

[0017] The present invention also relates to a watchmaking device comprising a mechanism as defined above.

[0018] Other features and advantages of the present invention will become apparent from the following detailed description of several embodiments of the invention, given by way of non-limiting examples, and made with reference to the accompanying drawings in which: there figure 1 is an isometric view of a ratchet mounted on a barrel arbor according to a first embodiment of the invention; the figure 2 is an isometric view of one end of a single barrel shaft, showing a male element according to a first variant of the first embodiment; the figure 3is a top view of the ratchet alone, showing a female element according to the first variant corresponding to the figure 2 ; there figure 4 is a top view of the male element of the figure 2 ; THE figures 5 to 7 are top views representing other variants of the first embodiment of the male and female elements of the invention; the figure 8 is a top view of a ratchet mounted on a barrel arbor according to a second embodiment of the invention not covered by the claims; and the figure 9 is an enlarged top view of the male and female elements of the figure 8 .

[0019] With reference to figures 1 to 3The present invention relates to a clockwork mechanism comprising at least two organs 1, 2 and a device for driving one of said organs in rotation by the other comprising a male element carried by one of said organs and a female element carried by the other of said organs and arranged to cooperate with said male element, one of said organs 1, 2 driving the other organ in rotation.

[0020] In the following description, organ 1 is a shaft or rod defining a longitudinal axis and carrying at its end the male element 1a and organ 2 has a hollowed-out imprint constituting the female element 2a into which the male element 1a is inserted to ensure torque transmission.

[0021] Part 1 is, for example, a barrel arbor, part 2 being a ratchet arranged to be mounted on the end of the barrel arbor, as shown in the figure 1, in order to transmit torque to the barrel arbor, via the winding stem operated by a user, allowing the winding of the timepiece.

[0022] It is quite clear that the male element can be carried by the led organ, the female element being provided on the leading organ, or conversely the male element can be carried by the leading organ, the female element then being provided on the led organ.

[0023] With reference to figures 4, 5 And 9 , the male element 1a is cut and shaped at the end of the organ 1 so that, in cross-section, it has a shape defining overall an outer circle 4 of outer diameter D and center C, its outer contour being partially coincident with said outer circle 4, and comprising, opening at its outer periphery, at least one hollow 6 corresponding to a first embodiment according to the Figures 4 and 5, or at least one dish 6 corresponding to a second embodiment according to the figure 9 , symmetrical with respect to an axis 8 passing through the center C of the outer circle 4.

[0024] According to the first embodiment, as shown in the figures 1 to 7 , the hollow 6 is circular in shape, with radius R, and center C' located outside the outer circle 4.

[0025] The hollow 6 is directed towards the center C so as to be tangent to an inscribed inner circle 10 of center C, concentric with the outer circle 4, and of inscribed diameter d such that the difference between the outer diameter D and the inscribed diameter d is greater than or equal to 8% and less than 20% of the outer diameter D.

[0026] Said hollow 6 is concave and directed towards the center C, towards the interior of the male element 1a, so as to present a vertex 6a defining said inscribed inner circle 10, said vertex 6a of hollow 6 being defined as the point of hollow 6 which is tangent to the inscribed inner circle 10.

[0027] Preferably, the difference between the outside diameter D and the inscribed diameter d is between 10% and 19% of the outside diameter D, and more preferably between 12% and 19% of the outside diameter D, and more specifically between 13% and 15% of the outside diameter D in the case of a flat.

[0028] The outside diameter D preferably corresponds to the diameter of the shaft 1, which can be on the order of 1 mm for a barrel shaft.

[0029] According to the first embodiment, and when the hollow 6 is circular in shape, its radius R defines a point P equal to the sum of the radius of the inscribed inner circle 10 and the radius R of the circular hollow 6. In a particularly advantageous way, said point P may be less than 300%, and preferably less than 200%, of the radius of the inscribed inner circle 10.

[0030] Preferably, said point P is less than 150% of the radius of the inscribed inner circle 10.

[0031] Advantageously, the circular hollow 6 can have a radius R chosen so that the center C' of said circular hollow 6 lies between the inner inscribed circle 10 and the outer circle 4, as shown in the figure 7 .

[0032] Advantageously, in either the first or second embodiment, the cross-sectional shape of the male element 1a comprises at least two identical hollows 6 arranged around the inner inscribed circle 10 sufficiently close to each other to form a convex radial protrusion 12, connecting them to each other by their opposite edges. This protrusion 12 extends outward from the male element 1a along an axis 14 passing through the center C of the outer circle 4, the protrusion 12 being symmetrical with respect to this axis 14. The protrusion 12 has a vertex 12a coinciding with an arc of the outer circle 4. This means that, depending on the width of the protrusion 12, its vertex 12a coincides with a more or less large arc of the outer circle 4, differing by only one point.In this way, the apex 12a of the protrusion 12 does not include a sharp edge, the presence of which is not recommended for the reasons stated above. The precision of the machining tools traditionally used in watchmaking is such that angular sectors α can be produced, typically by turning, with greater precision than edges. Thus, a protrusion 12 with an apex 12a coinciding with an arc of the outer circle 4 is particularly advantageous in terms of manufacturing and machining precision. The same applies to the corresponding protrusion 18 of the female element 2a.

[0033] Preferably, the arc of a circle, defined by the angular sector α (cf. figure 5) corresponding to the width of the protrusions 12 is such that the angle α is between 5° and 340°, preferably greater than or equal to 10°, even more preferably greater than or equal to 15°, preferably greater than or equal to 20°, depending on the number of protrusions and hollows or flats. Typically, for a configuration with six protrusions and six hollows as shown on the figures 5 to 7 The angle α is between 10° and 50°, and between 20° and 40° for a configuration with four protrusions and four flats as shown on the figure 9 .

[0034] According to the invention, the imprint carved in organ 2 constituting the female element 2a has, in cross-section, the same shape as that of the male element 1a defined above, arranged to receive and cooperate with said male element 1a in order to transmit a couple from one to the other of said organs 1 and 2.

[0035] To this end, the female element 2a comprises alternating recesses 16 and protrusions 18 contiguous on both sides to one of these recesses 16, the recesses 16 having the same shape as the recesses 6 described above and the protrusions 18 having the same shape as the protrusions 12 described above, so that the female element 2a conforms to the contours of the male element 1a over its entire cross-section, said male element 1a fitting or interlocking perfectly into the female element 2a. Only the dimensions of the female element 2a are adapted to provide just the necessary clearance for mounting the male element 1a within the female element 2a.

[0036] In the context of the present invention, the cross-section of the male element 1a includes at least one protrusion 12. The shape and dimensions of the cross-section of the female element 2a are advantageously chosen to ensure a tighter fit between the male element 1a and the female element 2a at the arc-shaped portions of the protrusions 12 and 18. Indeed, the machining of these portions is very precise, and a tight fit at this point promotes good concentricity of the male element 1a and the female element 2a. This results in improved torque transmission. This is particularly advantageous when component 1 is a barrel shaft and component 2 is a ratchet, and even more so when such components are used in a series arrangement of barrels.

[0037] More play can typically be allowed between the male elements 1a and female elements 2a at other portions of the contour of said elements 1a, 2a, particularly at portions including flats such as the flats 6, whose machining is generally less precise, as illustrated in the figure 9 .

[0038] Advantageously, the male element 1a and the female element 2a comprise at least three hollows or flats 6, 16 alternating with at least three protrusions 12, 18 respectively, regularly distributed around their respective inner inscribed circles. Here, only the inner inscribed circle 10 of the male element 1a is shown. Preferably, the male element 1a and the female element 2a comprise between four and eight hollows or flats 6, 16 regularly distributed around their respective inner inscribed circles, and preferably at least five hollows 6, 16 and five protrusions 12, 18. According to a particularly preferred variant of the first embodiment, the male element 1a and the female element 2a comprise six hollows 6, 16 alternating with six protrusions 12, 18, regularly distributed around their respective inner inscribed circles, as shown in the figures 1 to 7According to a particularly preferred variant of the second embodiment, the male element 1a and the female element 2a comprise four flats 6, 16 alternating with four protuberances 12, 18, regularly distributed around their respective inner inscribed circle, as shown on the figures 8 and 9 .

[0039] Outside the scope defined by the invention, the male element and its corresponding female element may respectively have a cross-sectional shape comprising at least one hollow and at least one flat area. Similarly, on the same shape, the hollows may differ from one another, provided they comply with the conditions of the inscribed circle.

[0040] On the shaft 1, the protrusions 12 form longitudinal edges 20 connected to the surface of the shaft body 1, and the hollows or flats 6 are connected to the surface of the shaft body by shoulders 22, as shown in the figure 2The shoulders 22 act as stops to lock the component 2 mounted on the component 1 in position.

[0041] THE figures 5 to 7 represent different variants of the first embodiment of the invention, obtained by varying the difference between the external diameter D and the inscribed diameter d as well as the pointing, the male and female elements having six hollows 6 alternating with six protrusions 12, regularly distributed around the inner inscribed circle 10.

[0042] The angle β (cf. figure 5 ) between the tangent passing through the point of connection of a hollow 6 and the adjacent protuberance 12 and the axis of symmetry 14 of said adjacent protuberance 12 is greater than 22° and preferably greater than 25°.

[0043] In the variant of Figures 5 And 7 The difference between the outer diameter D and the inscribed diameter d is 18%, and in the variant of the figure 6, the difference between the outer diameter D and the inscribed diameter d is 14%.

[0044] In the variant of Figures 5 And 6 , the point P is less than 200% of the radius of the inscribed circle 10.

[0045] In the variant of the figure 7 , the point P is less than 150% of the radius of the inscribed circle 10. More specifically, the point P of the variant of the figure 7 , for which the center C' of the circular hollow 6 located between the inner inscribed circle 10 and the outer circle 4, is on the order of 120% of the radius of the inner inscribed circle 10.

[0046] The torque transmitted before breakage of a barrel shaft with a diameter D of 1 mm and the contact pressure at the interface of the barrel shaft and the ratchet, respectively having the male and female elements corresponding to the figures 5 to 7 .

[0047] For comparison, measurements were also taken with male / female elements of complementary square shape of equivalent dimensions.

[0048] The torque transmitted before breakage of the barrel shaft for the male / female elements of the present invention is greater than that obtained with the comparative square-shaped male / female elements.

[0049] The male / female elements of the present invention therefore make it possible to increase the strength of the organ carrying the male element compared to a square assembly traditionally used in watchmaking.

[0050] Furthermore, the contact pressure for the male / female elements of the present invention is lower than that obtained with comparative square-shaped male / female elements.

[0051] The male / female elements of the present invention thus make it possible to reduce the contact pressure at the interface of components 1 and 2 compared to a square assembly traditionally used in watchmaking. Wear at the interface of components 1 and 2 is therefore reduced.

[0052] Furthermore, the variant of the figure 6 which has a difference between the outer diameter D and the inscribed diameter d that is less than that of Figures 5 And 7 allows for a higher torque transmitted before breakage than that obtained with the variants of Figures 5 And 7 .

[0053] Furthermore, the variant of the figure 7 allows for a contact pressure lower than that obtained with the variant of the figure 5 .

[0054] Consequently, a decrease in the difference between the outside diameter D and the inscribed diameter d allows the transmitted torque to be increased before breakage and a decrease in the point P allows the contact pressure to be reduced, which makes it possible to adapt the shape of the male / female elements if it is desired to make the components 1 and 2 out of soft or brittle materials, such as brass, silicon or a ceramic, instead of the steel traditionally used for square assemblies.

[0055] Furthermore, when the number of hollows or flats / protuberances is chosen to be at least five, the indexing of organs 1 and 2, for example the indexing of the ratchet in relation to the barrel arbor, will be easier than with a square assembly.

[0056] Finally, the identical cross-sectional shapes of the male and female elements improve the guidance between them, for example, compared to a conventional coupling using a shaft and a ratchet with a square hole. Square couplings result in significant play, whereas with the present invention, the clearances are reduced, for example, by improving the flatness of the ratchet on the shaft.

Claims

1. Timepiece mechanism comprising at least two members, namely an arbor (1) and a ratchet (2), as well as a device for rotationally driving one of said members (1, 2) by the other comprising a male element (1a) borne by said arbor (1) and a female element (2a) borne by said ratchet (2) and arranged to cooperate with said male element (1a), said timepiece mechanism being characterised in that the male element (1a) has, in cross-section, a shape defining, overall, an outer circle (4) with an outer diameter D and centre C and comprising at least two troughs (6), each of said troughs (6): - being circular; - being symmetrical with respect to an axis (8) passing through the centre C of the outer circle (4); - being directed towards the centre C so as to be tangential to an inner inscribed circle (10) with a centre C and an inscribed diameter d such that the difference between the outer diameter D and the inscribed diameter d is greater than or equal to 8% and less than 20% of the outer diameter D; and - having a radius (R) defining a profile radius (P) equal to the sum of the radius of the inner inscribed circle (10) and the radius (R) of the circular trough (6), said profile radius (P) being less than 300%, preferably less than 200%, of the radius of the inner inscribed circle (10); said at least two troughs (6) being arranged around the inner inscribed circle (10) to form therebetween a protuberance (12) connecting them to each other, said protuberance (12) having a tip (12a) coincident with an arc of the outer circle (4), and the female element (2a) having, in cross-section, the same shape as that of the male element (1a), arranged to receive and cooperate with said male element (1a) in order to transmit torque from one of said members (1, 2) to the other.

2. Timepiece mechanism as claimed in claim 1, characterised in that the difference between the outer diameter D and the inscribed diameter d is between 10% and 19% of the outer diameter D.

3. Timepiece mechanism as claimed in claim 2, characterised in that the difference between the outer diameter D and the inscribed diameter d is between 12% and 19% of the outer diameter D.

4. Timepiece mechanism as claimed in any one of the preceding claims, characterised in that said profile radius (P) is less than 150% of the radius of the inner inscribed circle (10).

5. Timepiece mechanism as claimed in any one of the preceding claims, characterised in that the circular trough (6) has a centre (C') located between the inner inscribed circle (10) and the outer circle (4).

6. Timepiece mechanism as claimed in any one of the preceding claims, characterised in that the male element (1a) and the female element (2a) comprise at least three troughs (6, 16) distributed evenly around their inner inscribed circle (10).

7. Timepiece mechanism as claimed in any one of the preceding claims, characterised in that the male element (1a) and the female element (2a) comprise between four and eight troughs (6, 16) distributed evenly around their inner inscribed circle (10), and preferably six troughs (6, 16) distributed evenly around their inner inscribed circle (10).

8. Timepiece comprising a mechanism as claimed in any one of claims 1 to 7.

9. Item of timepiece equipment comprising a mechanism as claimed in any one of claims 1 to 7.