CH715828B1 - Watch movement fitted with two coaxial cannon wheels. - Google Patents

Abstract

The watch movement according to the invention comprises a first wheel (22) provided with a first barrel (24) and a second wheel provided with a second barrel, the two barrels being coaxial and arranged so that the first barrel is located at the less partially inside the second barrel. The first barrel has an outer diameter which is adjusted to the inner diameter of the second barrel so as to form an internal guide for the second barrel while allowing relative rotation between the two barrels. The first barrel has an outer cylindrical surface which is formed of a plurality of distinct elementary surfaces (42, 44) each having an angular opening α which is less than one hundred and twenty degrees, preferably less than sixty degrees, these distinct elementary surfaces being angularly separated by intermediate zones (43, 45), the radius of which at the central axis (38) of the two barrels is less than half of the said outer diameter of the first barrel.

Description

Technical area

The present invention relates to the field of watch movements of the mechanical type or of the electromechanical type. More particularly, the invention relates to two coaxial cannon wheels fitted to such a watch movement, one of the two cannons of which passes through the other internally.

Technology background

[0002] In mechanical or electromechanical watch movements, it is common for these to comprise two coaxial wheels each surmounted by a barrel with the barrel of a first of the two wheels passing through the barrel of the second of these two wheels. This situation generally arises when the analog display comprises two coaxial indicators, in particular two coaxial hands. By way of example, mention will be made of a roadway and an hour wheel carrying respectively at their free ends a minute hand and an hour hand. Such a situation also arises for a display having a '12 hour' hand and a '24 hour' hand arranged coaxially.

[0003] A known problem when a first barrel is threaded into a second barrel with the first barrel having an outside diameter which is adjusted to the inside diameter of the second barrel, so as to form an internal guide for the second barrel while allowing rotation of this second barrel relative to the first barrel and lubrication between the first and second barrels, comes from the fact that two surfaces located at a very short distance from each other and having a liquid between them, in particular a lubricating oil, tend to stick together, preventing relative rotation between the two barrels.

To remedy the aforementioned problem, the person skilled in the art generally produces a first barrel as shown in Figure 1, which shows a barrel wheel 2 formed by a wheel 4 surmounted by a barrel 6. It is expected that the free end of barrel 6 receives a needle once the watch movement is mounted. Barrel 6 therefore defines the first barrel mentioned above (the barrel having the smallest diameter, that is to say the inner barrel). Machining is carried out in the cylindrical wall of barrel 6 so as to obtain a circular groove 12 between two outer cylindrical surfaces 8 and 10. These two outer cylindrical surfaces are preferably located respectively at the base of the first barrel and on the side of its end. free in the upper region of the second barrel mentioned previously (not represented here, it is the barrel having the largest diameter, that is to say the outer barrel), so as to form a good guidance of the second barrel while limiting the outer surface of the first barrel located at a very short distance from the inner surface of this second barrel.

Summary of the invention

As part of the development leading to the present invention, it has been observed that the problem of sticking between the first and second barrels mentioned in the technological background sometimes remains despite the machining of a circular groove to form two outer cylindrical guide surfaces as shown in Figure 1. This observation concerns in particular barrels of relatively large diameter, for example when the watch movement has in addition to the hour hand and the minute hand a hand of the seconds and/or a 24-hour hand, all arranged coaxially.

It has also been observed that, in particular for questions of resistance to the mechanical stresses to which two coaxial barrels each carrying a needle can be subjected, the two outer cylindrical surfaces 8 and 10 of the barrel 6 of Figure 1 must each have a certain height. It follows that these two cylindrical guide surfaces cannot be reduced by reducing their height too much, for example by increasing the height of the intermediate circular groove 12. Thus, this solution which could come to the mind of a person skilled in profession is not well suited and would cause other reliability problems for the watch movement.

To remedy the aforementioned problems, the present invention provides a watch movement comprising a first wheel provided with a first barrel and a second wheel provided with a second barrel, the first and second barrels having the same central axis which defines the axis of rotation of the first and second wheels and being arranged so that the first barrel is located at least partially inside the second barrel, the first barrel having an outer diameter which is adjusted to the inner diameter of the second barrel so as to form an internal guide for the second barrel while allowing rotation of this second barrel relative to the first barrel. Then, the first barrel has an outer cylindrical surface, defining said outer diameter, which is formed of a plurality of distinct elementary surfaces each having an angular opening α which is less than one hundred and twenty degrees, these distinct elementary surfaces being angularly separated by intermediate zones whose radius at the axis of rotation of the first and second wheels is less than half of said outer diameter of the first barrel.

In a preferred variant, a first part of distinct elementary surfaces is distributed along a first median circle, passing axially through the middle of each of these distinct elementary surfaces, and a second part of distinct elementary surfaces is distributed along the along a second median circle passing axially through the middle of each of these separate elementary surfaces, the first and second median circles being located at different heights, in the axial direction of the first and second barrels, so as to leave an intermediate groove between the first part of distinct elementary surfaces and the second part of distinct elementary surfaces.

[0009] Thanks to the characteristics of the invention, it is possible to significantly reduce the outer cylindrical surface of the first barrel, while maintaining a certain height at the elementary surfaces to guide the second barrel, and also to no longer have two surfaces. cylindrical which are continuous over 360° and therefore closed on themselves. It follows from the characteristics of the invention that the risk of the first and second barrels adhering to each other, in particular when the watch movement is stationary, is greatly reduced relative to the embodiments of the prior art. Thus, during and after winding a watch movement according to the invention, there is little risk that the analog display will be blocked, in particular by a very thin film formed by a lubricating oil.

Brief description of figures

The invention will be described below in more detail using the accompanying drawings, given by way of non-limiting examples, in which: Figure 1 shows a cannon wheel of the prior art, for example a roadway, the cannon of which serves as a guide for another cannon wheel; Figure 2 is a section through a watch movement according to the invention; Figure 3 is a perspective view of the 12 o'clock wheel of the watch movement of Figure 2; and Figure 4 is a partial enlargement of Figure 2.

Detailed description of an embodiment of the invention

Will be described below, with the aid of Figures 2 to 4, an embodiment of a watch movement 20 according to the invention. This watch movement is provided with an analog display comprising four coaxial hands (not shown) carried respectively by a central axis and three coaxial barrels. The watch movement 20 comprises a first barrel wheel 23, formed by a first wheel 22 and a first barrel 24, and a second barrel wheel 27 formed by a second wheel 26 and a second barrel 28. These first and second barrels have a same central axis 38 which defines the axis of rotation of the first and second wheels and are arranged so that the first barrel 24 is located partially inside the second barrel 28, More precisely, the first barrel entirely crosses the second barrel, the first wheel being arranged below the second wheel while the '12 o'clock' hand carried by the first barrel is situated above the '24 hour' hand carried by the second barrel.

The first barrel 24 has an outer diameter D1 (D1=2-R1 where R1 is the outer radius of the first barrel 24) which is adjusted to the inner diameter D2 of the second barrel (D2=2·R2 where R2 is the radius inside the second barrel 28), so as to form an internal guide for the second barrel while allowing relative rotation between this second barrel and the first barrel. Preferably, lubrication is provided between the outer cylindrical surface of the first barrel and an inner cylindrical surface 40 of the second barrel, this inner cylindrical surface having the inner diameter D2.

The watch movement 20 further comprises a third wheel 30 provided with a third barrel 32, provided to carry a minute hand, and a central axis 34 which is provided to carry a second hand. The third cannon wheel 31 therefore here forms a roadway. The central axis 34 is guided in rotation by a fixed tube 36 which has for this purpose an internal annular projection at its upper end.

According to the invention, the outer cylindrical surface of the first barrel 24, defining the outer diameter D1, is formed of a plurality of elementary surfaces 42 and 44 which are distinct, this plurality of elementary surfaces each having an angular opening a , relative to the central axis 38, which is less than sixty degrees (α < 60°) and being angularly separated from each other by intermediate zones 43 and 45 whose radius at the axis of rotation 38 is less to the outer radius R1 of the first barrel. It will be noted that the radius of the intermediate zones 43 and 45 is not necessarily constant, but it remains less than the radius R1 on these intermediate zones. Indeed, as seen in Figure 3, the intermediate areas 43 and 45 are slightly concave because they are machined using a circular wheel in the outer wall of the barrel 24. However, these intermediate areas can also define cylindrical or flat surfaces. In the variant shown in Figure 3, the angular opening has elementary surfaces 42 and 44 is located in an angular range between thirty and forty degrees, or 30°<α<40°. In a general variant, provision is made for the elementary surfaces to have an angular opening which is less than one hundred and twenty degrees, that is to say α<120°.

[0015] According to a main variant, the elementary surfaces 42 are regularly distributed along a first median circle (not shown so as not to overload the drawing) passing axially through the middle of each of these elementary surfaces 42. Similarly, the elementary surfaces 44 are regularly distributed along a second median circle (also not shown so as not to overload the drawing) passing axially through the middle of each of these elementary surfaces 44.

In the advantageous variant shown in Figure 3, the elementary surfaces 42 correspond to a first half of the plurality of elementary surfaces constituting the outer cylindrical surface of the barrel 24, while the elementary surfaces 44 correspond to the second half of this plurality of elementary surfaces. The elementary surfaces 42 are respectively aligned axially with the elementary surfaces 44.

[0017] Preferably, the aforementioned first median circle is located, along the first barrel 24, on the side of the first wheel 22, so that the elementary surfaces 42 extend at the base of the second barrel 28, and the second aforementioned median circle is located, along the first barrel, on the side opposite the first wheel, so that the elementary surfaces 44 extend at a certain distance from the elementary surfaces 42. The lower elementary surfaces 42 are axially separated from the elementary surfaces upper 44 by intermediate zones 46. These intermediate zones 46 are formed by a circular groove whose radius R3 at the axis of rotation 38 is less than the outer radius R1 of the barrel 24.

It will be noted that the present invention can also be applied to the third barrel 32 which is located partially inside the first barrel 24 and which passes through this barrel 24. The barrel 32 has an outer diameter R4 which is adjusted to the diameter interior R5 of barrel 24 so as to form an internal guide for this barrel 24 while allowing rotation of the third barrel relative to the first barrel and, preferably, lubrication between the outer cylindrical surface 52 of the third barrel, which then consists of separate elementary surfaces as described above, and the inner cylindrical surface 50 of the barrel 24.

Claims (6)

1. Watch movement (20) comprising a first wheel (22) provided with a first barrel (24) and a second wheel (26) provided with a second barrel (28), the first and second barrels having the same central axis (38) which defines the axis of rotation of the first and second wheels and being arranged so that the first barrel is located at least partially inside the second barrel, the first barrel having an outer diameter D1 which is adjusted to the diameter interior D2 of the second barrel so as to form an internal guide for the second barrel while allowing rotation of this second barrel relative to the first barrel and lubrication between the first and second barrels, characterized in that the first barrel has a cylindrical surface exterior, defining said exterior diameter D1, which is formed of a plurality of distinct elementary surfaces (42, 44) each having an angular opening a which is less than one hundred and twenty degrees, that is to say α < 120°, these distinct elementary surfaces being angularly separated by intermediate zones (43, 45), the radius of which at the axis of rotation (38) of the first and second wheels is less than half of the said outer diameter D1 of the first barrel. 2. Timepiece movement according to claim 1, characterized in that a first part of distinct elementary surfaces (42) among the plurality of distinct elementary surfaces is distributed along a first median circle, passing axially through the middle of each of these distinct elementary surfaces, and a second part of distinct elementary surfaces (44) among the plurality of distinct elementary surfaces is distributed along a second median circle passing axially through the middle of each of these distinct elementary surfaces. 3. Timepiece movement according to claim 2, characterized in that the first part of distinct elementary surfaces (42) corresponds to a first half of the plurality of distinct elementary surfaces while the second part of distinct elementary surfaces (44) corresponds to the second half of this plurality of distinct elementary surfaces. 4. Timepiece movement according to claim 3 and in which said intermediate zones (43, 45) define first intermediate zones, characterized in that the distinct elementary surfaces of the first half of distinct elementary surfaces are separated from the distinct elementary surfaces of the second half of distinct elementary surfaces, two by two along the direction of said axis of rotation (38), by second intermediate zones (46), the first median circle being located, axially along the first barrel (24), on the side of the first wheel (22), relative to the second intermediate zones, so that the first half of distinct elementary surfaces (42) extends at the base of the second barrel (28), and the second median circle is located, axially along the first barrel, on the side opposite the first wheel, relative to the second intermediate zones, so that the second half of distinct elementary surfaces (44) extends at a distance from the first half of distinct elementary surfaces. 5. Timepiece movement according to one of the preceding claims, characterized in that said angular aperture α of each of the distinct elementary surfaces of the plurality of distinct elementary surfaces is less than sixty degrees, that is to say α <60° . 6. Watch movement according to one of the preceding claims, characterized in that said outer diameter D1 of the first barrel (24) is adjusted to said inner diameter D2 of the second barrel (28) so as to allow lubrication between the outer cylindrical surface of the first barrel and an inner cylindrical surface (40) of the second barrel having said inner diameter.