CH705911A2 - Over-molded smooth bearing for clockwork of timepiece, has core made of plastic and injected into revolution cavity and comprising outer cage and inner cage that is contained in cavity, where core is injected between cages - Google Patents

Abstract

The bearing (1) has a core (5) made of plastic and injected into a revolution cavity (4), where the core has an outer cage (3). An inner cage (2) is contained in the cavity, and the core is injected between the inner- and outer cages. The core is delimited by an outer revolution surface (20) that comprises the inner cage and by an inner revolution surface (30) that comprises the outer cage. The outer revolution surface and/or the inner revolution surface comprise a groove (6) or a revolution shoulder to immobilize the core in a direction of the axis. An independent claim is also included for a method for manufacturing an over-molded smooth bearing.

Description

Field of the invention

The invention relates to a molded overmolded clock bearing.

The invention further relates to a watch movement comprising at least one such smooth bearing.

The invention also relates to a timepiece comprising at least one such smooth bearing.

The invention also relates to a method of manufacturing a molded overmolded clock bearing.

The invention relates to the field of watchmaking, and more particularly the field of guides and bearings.

Background of the invention

[0006] Two types of watch bearings are essentially known: - Ball bearings have a large number of components, and it is necessary to adjust their frolicking during assembly; - Smooth bearings are expensive to achieve due to the desired accuracy, their impact resistance is poor when they include a stone, frost adjustment is also necessary.

In one case as in the other, the components associated with these bearings must be made with a high level of accuracy.

The lubrication of the bearings is a difficult area that requires care, and maintenance in service.

Summary of the invention

The invention proposes to circumvent these problems of the prior art, providing bearings less expensive, reduced number of components, little sensitive to shocks, and not requiring special adjustment during their assembly.

For this purpose, the invention relates to an overmolded clock bearing, characterized in that it comprises a plastic core injected into a cavity of revolution that comprises an outer cage.

According to a feature of the invention, said sliding bearing further comprises at least one inner cage contained in said cavity, and said plastic core is injected between said inner race and said outer race.

According to a feature of the invention, said core is defined by an outer surface of revolution that includes said inner cage and an inner surface of revolution that includes said outer cage.

According to a feature of the invention, said outer surface of revolution and said inner surface of revolution are coaxial around a same axis of revolution.

According to a feature of the invention, said outer surface of revolution and / or said inner surface of revolution comprises at least one groove or a shoulder of revolution for the immobilization of said core in the direction of a common axis of revolution. to said outer surface of revolution and said inner surface of revolution.

According to one characteristic of the invention, the constituent plastics material of said core has a shrinkage coefficient of between 2.0% and 3.0% which determines the functional clearance of said plain bearing between said inner race and said race core. on the one hand, and between said outer cage and said core on the other.

According to a feature of the invention, said sliding bearing consists exclusively of said inner race, said core, and said outer cage.

According to a feature of the invention, in said cavity are positioned a plurality of inner cages having coaxial contact surfaces of revolution with each other and with said cavity around a same axis of revolution, said inner cages being threaded on. in one another and separated from said cavity for fa more external of them, and two by two for the others, each time by a plastic core injected into a chamber delimited by the internal volume of the cage the outermost, and by the external volume of the cage more internal fa.

The invention also relates to a watch movement comprising at least one such smooth bearing.

The invention also relates to a timepiece comprising at least one such smooth bearing.

The invention also relates to a method of manufacturing a molded overmolded sliding bearing, characterized in that the following steps are carried out: an outer cage is prepared which is intended to be incorporated in said fool bearing and which comprises a cavity of revolution about an axis of revolution; said cavity is used as an injection or pouring chamber; an injection or a casting of plastic material is carried out in said chamber in order to produce a core delimited by said cavity; the conditions of a thermal or crystalline shrinkage of said plastic material are provided to limit said shrinkage to a range of 2.0% to 3.0%; the complete withdrawal of said plastic material is awaited before using said plain bearing.

According to one characteristic of the invention, before carrying out said injection or said casting: a zone of injection or casting is defined around said cavity of revolution by the addition of closure surfaces connected to said cavity, and said injection or casting of plastic material is carried out in said chamber in order to produce a core delimited by said cavity and said closing surfaces; after complete removal of said plastic material, said closing surfaces are moved away.

According to a characteristic of the invention, before carrying out said injection or said casting, said inner cavity, which is intended to be incorporated in said sliding bearing, is inserted into said revolution cavity and coaxially to said outer cage along said axis of revolution; - Is defined said injection chamber or casting by an outer surface of revolution that includes said inner cage and an inner surface of revolution that includes said outer cage.

According to a characteristic of the invention, before carrying out said injection or said casting, said injection or casting chamber is delimited by an outer surface of revolution that comprises said inner race and by an inner surface of revolution that comprises said outer cage, and by the addition of closure surfaces connected to said cavity and to said inner cage respectively bordering said inner surface of revolution and said outer surface of revolution; and after complete removal of said plastic material, said closure surfaces are moved away.

Brief description of the drawings

Other features and advantages of the invention will appear on reading the detailed description which follows, with reference to the accompanying drawings in which: <tb> - fig. 1 <sep> shows, schematically and in section in a plane passing through an axis of revolution, a sliding bearing according to the invention, in a first embodiment with a plastic core molded in an outer cage, during the injection or casting of the plastic material constituting this core; <tb> - fig. 2 <sep> represents, similarly to FIG. 1, a second embodiment of the invention, with a plastic core molded between an inner cage and an outer cage during the injection or casting of the plastic material constituting the core; <tb> - fig. 3 <sep> represents, similarly to FIG. 2, a second embodiment of the invention, after removal of the plastic material constituting the plastic core; <tb> - fig. 4 <sep> represents, similarly to FIG. 3, a second embodiment of the invention, after removal of the plastic material constituting this plastic core, and in another embodiment; <tb> - fig. 5 <sep> represents, schematically, a top view and a section similar to the previous figures, of a sliding bearing according to the invention made without mold; <tb> - fig. 6 <sep> represents, schematically, a top view and two sections similar to FIGS. 1 to 4, a sliding bearing according to the invention made with a mold having injection or casting channels visible in the top view and one of the two sections: <tb> - fig. 7 <sep> represents, in the form of a block diagram, a timepiece comprising a movement comprising a sliding bearing according to the invention.

Detailed Description of the Preferred Embodiments

The invention relates to the field of watchmaking, and more particularly the field of guides and bearings.

The invention relates more particularly to a rolling bearing 1 overmoulded clock.

According to the invention, this sliding bearing 1 comprises a core 5 of plastic material injected into a cavity 4 of revolution that includes an outer cage 3. This first embodiment is visible in FIG. 1. After complete polymerization, the plastic material has a slight shrinkage, which is sufficient to ensure the functional clearance necessary for the smooth bearing to function properly. As the core 5 has a homothetic geometry to that of the cavity 4, the removal of the plastic being regular, the geometry of the core 5 is as good as that of the cavity 4. It is therefore necessary, for optimal operation, to ensure the very good circularity of the cavity 4, the respect of the dimension is however insignificant since the adjustment is done by the injection or casting process, preferably injection.

According to a preferred embodiment shown in FIGS. 2 to 6, in a second embodiment, the sliding bearing 1 further comprises an inner cage 2 contained in the cavity 4. And the plastic core 5 is then injected between the inner cage 2 and the outer cage 3.

Preferably, the core 5 is delimited by an outer surface of revolution 20 that includes the inner cage 2 and an inner surface of revolution 30 that includes the outer cage 3.

Preferably, this outer surface of revolution 20 and this inner surface of revolution 30 are coaxial around a same axis of revolution D.

Thus, in a preferred embodiment, the core 5 is entirely of revolution, with respect to its contact surfaces with the outer cage 3, and with the inner cage 2 when it exists.

Preferably and particularly advantageously, the outer surface of revolution 20 and / or said inner surface of revolution 30 comprises at least one groove 6 or a shoulder 7 of revolution for the immobilization of the core 5 in the direction of a axis of revolution D common to the outer surface of revolution 20 and to the inner surface of revolution 30.

And, if possible, both the outer surface of revolution 20 and the inner surface of revolution 30 each comprise at least one such groove 6 or such a shoulder 7 of revolution for the immobilization of the core (5) in the direction of the axis of revolution D, as visible in the figures.

In a particular embodiment shown in FIG. 4, the outer surface of revolution 20 and the inner surface of revolution 30 comprise, at least one groove, and the other at least one shoulder, or conversely, this at least one groove and the at least one shoulder being revolution and for the immobilization of the core 5 in the direction of the axis of revolution D.

The choice of plastic is important. Preferably, the constituent plastic material of the core 5 has a shrinkage coefficient of between 2.0% and 3.0% which determines the functional clearance of the sliding bearing 1 between the inner cage 2 and the core 5 on the one hand, and between the outer cage 3 and the core 5 on the other.

This thermal or crystalline shrinkage, depending on the material used, thus conditions the bearing clearance.

Figs. 3 and 4 illustrate the shrinkage R after complete polymerization of the plastic material. The axial and radial play of the bearing 1 is defined by the shrinkage rate and the geometry of the bearing. For example, in the case of FIG. 3, a shrinkage of 2.5% of the walls of 0.4 mm, corresponds to a frost of 0.010 mm which is perfectly suited to the usual horological applications. This frolic comes from the process itself, and is guaranteed from one room to another.

In a preferred application, the plain bearing 1 according to the invention consists exclusively of the inner cage 2, the core 5, and the outer cage 3.

The invention also relates to a watch movement 100 comprising at least one such smooth bearing 1.

The invention also relates to a timepiece 100 comprising at least one such smooth bearing and / or such a movement 10.

The invention also relates to a method of manufacturing a molded overmolded smooth bearing 1, characterized in that the following steps are carried out: an outer cage 3 is prepared which is intended to be incorporated in the sliding bearing 1 and which comprises a cavity 4 of revolution about an axis of revolution D; the cavity 4 is used as an injection or pouring chamber 40; - Injection or casting of plastic material in the chamber 40 to achieve a core 5 defined by the cavity 4; the conditions of a thermal or crystalline shrinkage of this plastic material are ensured in order to limit the shrinkage to a range of 2.0% to 3.0%; - the complete removal of the plastic material is expected before using the plain bearing 1.

According to a particular implementation, before performing the injection or casting, is defined around the cavity 4 of revolution, an injection chamber or casting 40, by the addition of closure surfaces 11,12 connected to the cavity 4, thus forming a mold, as visible in FIG. 6. And then the injection or casting of plastic is carried out in the chamber 40 to produce a core 5 delimited by the cavity 4 and these closing surfaces 11, 12. After complete removal of the plastic material, these surfaces are removed. closure.

According to a particular implementation, for obtaining a smooth bearing 1 to three components, before performing the injection or casting, is inserted into the cavity 4 of revolution, and coaxially to the outer cage 3 along the axis of revolution D, an inner race 2 which is intended to be incorporated in the sliding bearing 1. The injection or casting chamber 40 is defined by an outer surface of revolution 20 which the inner race 2 comprises and by an inner surface of revolution 30 that includes the outer cage 3.

In particular, before performing the injection or casting, the injection or casting chamber 40 is delimited by an outer surface of revolution 20 that includes the inner cage 2 and an inner surface of revolution 30. which comprises the outer cage 3, and the addition of closure surfaces associated with the cavity 4 and the inner cage 2 at the edge respectively of the inner surface of revolution 30 and the outer surface of revolution 20. And, after withdrawal complete with the plastic material, the closing surfaces are moved away.

Naturally, if the invention is described here in the preferred application, because the most economical, a single core, it is understood that it can very easily be extended to a trundle type of mobile rotating one in the others, for example pavements of minutes and hours and a guide chimney receiving these roads. The application to a simple plain bearing is therefore in no way restrictive, and the invention must be understood as being applicable to any type of guidance in axial pivoting. The limitation of axial stroke by the use of grooves or shoulders is very useful in the manufacture of indemovable complex mobiles.

Also, the invention also relates to any type of overmolded plain bearing 1 having an outer cage 3 with a cavity 4 of revolution about an axis of revolution D, in which cavity 4 are positioned a plurality of inner cages 2 comprising contact surfaces of revolution about the axis of revolution D. These contact surfaces of revolution are coaxial with each other and with the cavity 4, and the inner cages 2 are threaded one into the other. The inner cages 2 are separated, from the cavity 4 for the outermost of them, and two by two for the others, each time by a core 5 made of plastic material injected into a chamber delimited by the internal volume of the cage the outermost, and by the outer volume of the innermost cage. Preferably, the chambers, in which the plastic is injected to form the cores, are further delimited by closure surfaces, for example substantially perpendicular to the axis D.

FIG. 8 illustrates an example of such a bearing 1 having an outer cage 3, separated from an inner inner cage 2A by a first core 5A. The intermediate cage 2A is separated from an axial inner cage 2B by a second core 5B. In each case, the withdrawal R of the core 5A, 5B ensures the functional clearance between the cages separated by the core concerned.

Thanks to the invention, many features are improved over the bearings of the prior art.

No mounting by driving, welding, screwing, riveting, or the like is necessary.

In the preferred embodiment where one of the inner or outer cages has one of the grooves or a shoulder, the sliding bearing can be handled in one piece without loss of components.

This bearing has no problem of impact resistance, due to the manufacture of the plastic core.

The adjustment of the game is intrinsic since it comes from the removal of the plastic material during its final polymerization.

It overcomes the problems of tight fitting tolerances depending on narrow manufacturing tolerances, so it is possible to significantly reduce the functional play. Indeed, it is not required particular precision, in diameter or in the axial direction, of the outer cage, and, as the case of the inner cage, since the plastic material occupies all the available volume during its injection or its casting. The injection or the casting thus compensates for all the tolerances, and the frolics remain perfectly correct.

The decrease in the number of components reduces the cost.

The quality risk is also reduced because it avoids a tedious frolicking setting.

The partition, that is to say the height of the outer cage relative to the inner cage, is perfectly mastered and centered. The control and centering are given by the symmetrical shrinkage of the plastic, and, when executed with a mold and closing surfaces, by the bearing surface in the mold to align the two cages.

It is possible to prevent ovalization of the core, and therefore any decentering, by the use of several injection channels or casting, as shown in FIG. 6.

The preferred embodiment by injection ensures good control of the process and its perfect reproducibility. The injection allows the creation of the core, the adjustment of the frost during the withdrawal, and the assembly of the bearing, which is unmountable after injection, when one of the cages, inside or outside, has a groove or a shoulder limiting the movement in the axial direction.

Different plastics have tribological qualities well suited to this application. More particularly, the use of the POM is satisfactory. The plastic material used may be composite, and incorporate slip improving compounds such as lubricant, PTFE, "Delrin®", "Rilsan®", "Nylon®", or the like. Preferably, the plastic is chosen with a coefficient of friction of between 0.07 and 0.15. The use of materials with lower coefficients of friction is also possible, despite their higher cost.

The removal being done symmetrically, we obtain the respect of the sharing of the meshing between a bearing wheel thus produced and the mobile that meshes with it.

Depending on the appropriate choice of the plastic material used for the core, it is possible to avoid lubrication of the bearing.

Claims (17)

1. overmolded clock bearing (1), characterized in that it comprises a core (5) of plastic material injected into a cavity (4) of revolution that comprises an outer cage (3). 2. Bearing (1) according to claim 1, characterized in that it further comprises at least one inner cage (2) contained in said cavity (4), and in that said core (5) of plastic material is injected between said inner race (2) and said outer race (3). 3. Bearing (1) according to claim 2, characterized in that said core (5) is defined by an outer surface of revolution (20) that comprises said inner race (2) and by an inner surface of revolution (30) that comprises said outer cage (3). 4. Bearing (1) according to claim 3, characterized in that said outer surface of revolution (20) and said inner surface of revolution (30) are coaxial about a same axis of revolution (D). 5. Bearing (1) according to one of the preceding claims, characterized in that said core (5) is of revolution. 6. Bearing (1) according to claim 3, characterized in that said outer surface of revolution (20) and / or said inner surface of revolution (30) comprises at least one groove (6) or a shoulder (7) of revolution for immobilizing said core (5) in the direction of an axis of revolution (D) common to said outer surface of revolution (20) and said inner surface of revolution (30). 7. Plain bearing (1) according to claim 6, characterized in that said outer surface of revolution (20) and said inner surface of revolution (30) each comprise at least one groove or a shoulder of revolution for the immobilization of said core (5) in the direction of said axis of revolution. 8. Bearing (1) according to claim 6, characterized in that said outer surface of revolution (20) and said inner surface of revolution (30) comprise, at least one groove, and the other at least one shoulder, or conversely, said at least one groove and said at least one shoulder being of revolution and for the immobilization of said core (5) in the direction of said axis of revolution (D). 9. Bearing (1) according to one of the preceding claims, characterized in that the constituent plastic material of said core (5) has a withdrawal coefficient of between 2.0% and 3.0% which determines the functional clearance of said smooth bearing (1) between said inner race (2) and said core (5) on the one hand, and between said outer race (3) and said core (5) on the other hand. 10. Bearing (1) according to claim 2, characterized in that it consists exclusively of said inner cage (2), said core (5), and said outer cage (3). 11. overmoulded plain bearing (1) according to claim 2, characterized in that, in said cavity (4) are positioned a plurality of inner cages (2) having contact surfaces of revolution coaxial with each other and with said cavity (4). ) around a same axis of revolution (D), said inner cages (2) being threaded into one another and separated, said cavity (4) for the outermost of them, and two by two for the others, each time by a core (5) of plastic material injected into a chamber delimited by the internal volume of the outermost cage, and by the external volume of the innermost cage. 12. Watch movement (10) comprising at least one plain bearing (1) according to one of the preceding claims. 13. Timepiece (100) comprising at least one sliding bearing (1) according to one of claims 1 to 11. 14. A method of manufacturing a sliding bearing (1) overmoulded watch, characterized in that the following steps are carried out: an outer cage (3) is prepared which is intended to be incorporated in said smooth bearing (1) and which comprises a cavity (4) of revolution about an axis of revolution (D); said cavity (4) is used as an injection or pouring chamber (40); - Injection or casting of plastic material in said chamber (40) to achieve a core (5) defined by said cavity (4); the conditions of a thermal or crystalline shrinkage of said plastic material are provided to limit said shrinkage to a range of 2.0% to 3.0%; the complete withdrawal of said plastic material is awaited before using said plain bearing (1). 15. A method of manufacturing a sliding bearing (1) according to claim 14, characterized in that, prior to performing said injection or said casting: - around the said cavity (4) of revolution, an injection or casting chamber (40) is defined by the addition of closure surfaces (11; 12) connected to the said cavity (4), and in that than: said injection or casting of plastic material is carried out in said chamber (40) in order to produce a core (5) delimited by said cavity (4) and said closing surfaces; after complete removal of said plastic material, said closing surfaces are moved away. 16. A method of manufacturing a sliding bearing (1) according to claim 14 or 15, characterized in that before carrying out said injection or said casting, - In said cavity (4) is rotated, and coaxially to said outer cage (3) along said axis of revolution (D), an inner cage (2) which is intended to be incorporated in said sliding bearing (1); - Is defined said injection chamber or casting (40) by an outer surface of revolution (20) that includes said inner cage (2) and an inner surface of revolution (30) that includes said outer cage (3). 17. A method of manufacturing a sliding bearing (1) according to claim 16, characterized in that, before carrying out said injection or said casting, said injection or casting chamber (40) is delimited by an outer surface. revolution (20) that comprises said inner cage (2) and an inner surface of revolution (30) that comprises said outer cage (3), and by the addition of closure surfaces connected to said cavity (4) and to said inner cage (2) respectively bordering said inner surface of revolution (30) and said outer surface of revolution (20), and in that, after complete removal of said plastic material, said closing surfaces are moved away.