HK1028113B - Method for manufactureing a clockwork wheel and a clockwork wheel manufactured according to such method - Google Patents

Description

Method for manufacturing a timepiece gear and timepiece gear manufactured according to the method

Technical Field

The invention concerns a method for making a timepiece gear comprising a circular plate having a first series of teeth on its periphery and a second series of teeth arranged at right angles to the plate. The invention also relates to a timepiece gear manufactured according to such a method.

Background

Cold flow (cold flow) manufacturing of timepiece gears using steel suitable for press forming has been proposed. Thus, for the purpose of optimizing the manufacture and use of timepiece gears, the gear proposed by document CH-B-677168 comprises a gear on which is mounted a pinion, the assembly comprising a bearing which can be a groove housing a stub (studs) or a stub entering a groove. The turntable, pinion and bearing are formed in a single piece and are formed by forging and stamping a plastic stream, particularly steel containing a material suitable for cold flow.

The gear wheel referred to in this reference is, however, a simple gear train comprising, in a very conventional manner, a turntable, the periphery of which is formed with a greater or lesser number of teeth, and a pinion mounted on said turntable, this pinion having only a limited number of teeth (in this example 6) oriented in the same direction as the teeth on the turntable. It is not indicated or suggested in the above document that the disclosed method can also be used to make fine-structured adjustment (time-use) gears, i.e. gears in which the second tooth structure is a cross-tooth structure comprising a considerable number of teeth (smaller in size than the simple timepiece pinion mentioned in this cited document).

Disclosure of Invention

The object of the present invention is to form a time or date adjusting gear having a more complicated structure than a simple gear structure including only one rotating disc and one pinion.

To achieve this object, the method of the present invention comprises the steps of:

there is provided a strip suitable for press forming,

cutting a circular groove into the strip, the inner diameter of the circular groove defining a disc from which the gear is obtained, said disc remaining attached to the strip by means of a plurality of bridge portions,

applying a die having a plurality of openings formed therein in a circumferential arrangement and having a cylindrical flat surface against the other surface of the die to cause the steel to flow into the die openings to form a second series of teeth after the die and cylinder have been removed from the disc,

cutting a hole in the center of the disk, and

the machined gear is obtained by cutting a first series of teeth from a circular disc, thus separating said gear from said strip.

The invention also relates to a timepiece gear, namely an hour or date regulating gear, manufactured according to the above method.

The advantages and the significance of this method will be explained in more detail by referring to the following description part and the attached drawings which are given by way of non-limiting example only.

Drawings

Figure 1 is a cross-section of a timepiece movement using a timepiece gear manufactured according to the method of the invention,

figure 2 is a perspective view of a first embodiment of a timepiece gear manufactured by means of a method according to the invention,

figure 3 is a cross-sectional view of the gear of figure 2,

figure 4 is a perspective view of a second embodiment of a timepiece gear manufactured by means of a method according to the invention,

fig. 5 and 6, 7 and 8, 9 and 10, 11 and 12 respectively show a first, a second, a third and a fourth step in a method for manufacturing a timepiece gear according to the invention.

Detailed Description

The clockwork mechanism shown in fig. 1 is a time adjustment mechanism comprising: watch stem 20, watch stem 20 being able to slide into dial 21 and having two locking positions due to the push in and pull out of a watch stem spring 22. This watch stem comprises: a pinion 23, the pinion 23 meshing with the transverse teeth 5, 19 in the adjusting gear 1, 2, such an adjusting gear and the method for its manufacture forming the subject of the present invention. The adjusting gears 1, 2 include: a turntable 3, a first series of teeth 4 formed on the periphery of the turntable 3, and a second series of teeth 5, 19 arranged at right angles to the turntable 3. The setting gears 1, 2 are in engagement with a motion work (not shown) which is transmitted between one side of the hollow shaft gear 24 and the other side of the hour wheel 25. An hour wheel 25 is attached to the tube 26 and an hour wheel (not shown) is also fitted on the tube 26. Hollow shaft gear 24 supports a minute hand (not shown) and a minute wheel 26 friction-fitted thereto. Fig. 1 also shows a second gear 27 attached to the shaft 28, with a second hand (not shown) fitted to the shaft 28. When the adjustment dial 20 is rotated to the pulled-out position, the adjustment gears 1 and 2 are driven, and the minute hand and the hour hand are driven by the hand movement mechanism. During this operation, a relative slip is formed between the cannon pinion 26 and the hollow shaft gear 24, which is stopped by a transmission (not shown). It should also be mentioned that the adjusting gear 1, 2 comprises a central hole 17, through which hole 17 a stub shaft 29 attached to the turntable 21 passes. The adjusting gears 1 and 2 are freely coupled to the stub shaft 29. Finally, the travel mechanism bridge portion 30 covers the time adjustment mechanism.

The adjustment gears 1, 2 themselves and their manufacturing method will be described below.

Fig. 2 and 3 show a first exemplary embodiment of the adjusting gear 1. As already described, this adjusting gear comprises a circular disc 3, around the periphery of which a first series of teeth 4 is formed, and a second series of teeth 5, also called transverse toothing, arranged at right angles to the disc 3. This first embodiment features a second series of cylindrical teeth 5 as clearly shown in fig. 3. The top of each tooth 5 is circular, but may be planar, as will be seen below.

Fig. 4 shows a second embodiment of the adjusting gear 2. The only difference with respect to the first embodiment is that the transverse toothing has shaped teeth 19, the teeth 19 being cut in a conventional manner for this type of adjusting gear. The following returns to this second embodiment.

According to the two embodiments of the invention described above, the manufacturing method comprises a series of steps, which are shown in fig. 5-12.

A strip 6 suitable for press forming is provided. Such a strip is suitable, for example, for cold forming, with a width of 16 mm and a thickness of 0.3 mm. Three pilot holes are formed through the use of a progressively pressurized forging die which will successively undertake all manufacturing processing steps. These pilot holes allow the strip to be accurately centered between the various dies and punches and then follow each other in progressively pressurized forging dies.

The first step is shown in fig. 5-6. Here, a circular ring-shaped groove 7 is cut into the strip steel 6. The inner diameter of this annular groove 7 defines a disc 9, from which disc 9 the desired timepiece gear is obtained. As shown in fig. 5, the disc 9 remains attached to the strip 6 by means of a number of bridge portions 10, i.e. 4 bridge portions 10 as shown in the figure. The tools used for this operation are shown in figure 6, which also shows the strip 6 cut to form the annular grooves 7, the cutting to form the grooves being carried out along the section lines VI-VI in figure 5. The tool for cutting the groove comprises a die 32 having 4 penetrating ring segments 33 and a punch 35 having 4 corresponding segments interrupted by 4 bridge portions 36.

The second step is shown in fig. 7-8. After this operation, the disc 9 is formed with a second sequence of teeth 5 arranged at right angles to the disc, as shown in figure 7. In fig. 8, the tools for the second step are shown in a cross-section taken along the cross-section line VII-VII in fig. 7, which also shows the strip 6 after the flow, which is formed in the following manner. A mould 12 having a plurality of through-going openings 13 is applied to one surface 11 of the disc 9. The flat surface on the cylinder 16 is pressed against the other surface 14 in the disc 9, causing the steel suitable for stamping to flow into the opening 13 in the die 12.

Fig. 7 and 8 show, as in the following figures, a second series of cylindrical teeth 5. To achieve this, the die 12 has a plurality of penetrating cylindrical holes 13. However, the shape of such cylindrical teeth is not conventional, enabling a softer flow than would be obtained by slotting in a conventional manner. Thus, during the time adjustment, a more harmonious adjustment movement is formed, which is distinguished by a greater comfort as it is not scratched. It should also be noted that the plurality of teeth 5 discussed herein is meant to have a considerable number of stamped teeth, with nothing to do with the fewer teeth (5 or 6) that form the timepiece pinion. Thus, as mentioned above, due to this surprising and unexpected effect, the method described produces a large number of teeth, which moreover have a very small size. An example is provided where the second series of teeth 5 in the described adjusting gear comprises 16 teeth, the diameter of the cylindrical part of which does not exceed 0.2 mm.

The height of the teeth 5 can be controlled by the force of the cylinder pressing against the surface 14 on the disc 9. However, in some cases, this height is limited by the placement of the pins 18 within each of the holes 13 in the mold 12. Whatever the solution chosen, the purpose of cutting to form the annular groove 7 in the first step of the method is now understood. In fact, during the pressing, the material will not flow from the teeth 5 into each hole 13 in the die 12, but also in a transverse direction in the longitudinal direction of the strip 6. By forming an empty gap, i.e. the annular groove 7, around the disc 9, a space will thus be formed for excess material from this flow, and thus the formation of the teeth 5 can be more tightly controlled. In the example described, the thickness of the centre of the disc 9 after pressing varies from 0.3 to 0.28 mm.

The die 12 is not limited to the cylindrical openings 13 arranged in a circular manner in the die. In practice, these apertures may be holes shaped so as to form a second series of shaped teeth. These teeth will then be similar to the teeth indicated by reference numeral 19 in the figures. These teeth 19, which are also formed as a result of the material flow, have the same configuration as those teeth which are formed by cutting in a conventional manner.

The third step is shown in fig. 9-10. As shown in fig. 9, the disc 9 has a hole 17 cut at the center thereof. As can be seen in fig. 1, this hole 17 is used in order to mount the adjusting gears 1, 2 so that they rotate freely on the stub shafts 29 on the turntable 21. The tools used in connection with this operation are shown in section in fig. 10, which also shows the strip 6 after the holes have been cut, the cut forming taking place along the section line X-X in fig. 9. The cutting and shaping tool includes a die 40 having a through hole 41 and a punch 42 formed in a punch block 43. The holes 41 and punches 42 are sized to cut the holes 17 in the formed disc 19. The punch 43 has an annular opening 44 formed therein to allow room for the teeth to be formed during the cutting and forming operation.

The fourth step is shown in fig. 11-12. In this fourth and final step, the finished gear wheel 1 is removed. To achieve this, as can be seen in fig. 11, a first series of teeth 4 is cut into the disc 9, which cut naturally separates the gear from the strip 6. The tools used in connection with this operation are shown in section in fig. 12, also showing the strip 6 and the gear wheel 1 after this gear wheel has been cut, the cut forming being carried out along the section line XII-XII in fig. 11. The cutting and shaping tool comprises a die 50 in which teeth 51 that have to be reproduced in the gear are cut and shaped, and a punch 42 with corresponding teeth 53. As is clear from fig. 12, when the cut formation is completed, the gear 1 is formed with teeth 4 on the periphery thereof while being separated from the disc 9. Again as an example of the gear described above for the second step, 16 transverse teeth are included, and after the cutting described in the fourth step, 26 peripheral teeth 4 are included.

The method proposed here is ingenious in concept, since the transverse teeth 5, whether cylindrical or shaped, can conveniently replace the usual machining methods, which consist in machining a blank forming a regulating gear, then in a first cutting-forming operation of the teeth forming the periphery of the disc followed by a second cutting-forming operation of the transverse teeth. The method using material flow is therefore particularly inexpensive, since it saves the time required for manufacturing the adjustment gear.

As indicated previously, the method described is used to manufacture adjustment gears comprising peripheral toothing and transverse toothing on the same disk. As shown in fig. 1, the gear is used either in the time adjustment mechanism or in a date adjustment mechanism for a date indicator.

Claims (7)

1. A method of manufacturing a timepiece gear (1, 2) comprising a disc (3), the disc (3) having a first series of teeth (4) on its periphery and a second series of teeth (5, 19) arranged at right angles to the disc, the method comprising the steps of:

providing a strip (6) suitable for stamping,

a circular groove (7) is cut into the strip (6), the inner diameter (8) of which corresponds to a disc (9), from which disc (9) gears are obtained, said disc remaining attached to the strip by means of bridge sections (10),

applying a mould (12) on one surface (11) of the disc, the mould being formed with a plurality of openings (13) perforated in a circumferential arrangement, and pressing the other surface (14) of the mould with the flat surface (15) of the cylinder (16) to cause the steel to flow inside the openings of the mould, forming a second series of teeth (5, 19) after removal of the mould (12) and cylinder (16) from the disc,

cutting a hole (17) in the center of the disc, and

the machined gear wheels (1, 2) are obtained by cutting a first series of teeth (4) from the disc, thus separating the gear wheels from the strip.

2. A method according to claim 1, characterized in that the plurality of openings (13) arranged circumferentially in the die (12) are cylindrical holes in order to form a second series of cylindrical teeth (5).

3. Method according to claim 2, characterized in that each cylindrical hole is plugged with a needle (18), the depth of the hole defining the height of the teeth (5).

4. A method according to claim 1, characterized in that the plurality of openings (13) arranged circumferentially in the mould (12) are shaped openings for forming a second series of shaped teeth (19).

5. Timepiece gear (1, 2) manufactured according to the method of claim 1.

6. Timepiece gear according to claim 5, characterised in that it is constituted as a time adjustment gear.

7. Timepiece gear according to claim 5, characterised in that it constitutes a date adjustment gear.