EP1039355B1 - Process for manufacturing indicator organs and indicator organ manufactured accordingly - Google Patents

Description

The present invention relates to a method of series production of a display member for a timepiece and a display member manufactured according to this method.

The display organ definition should be taken here under its broadest acceptance. It may be a dial, a date disc or moving figurines showing, for example, moon phases, provided however that these supplies have a rugged profile and therefore not flat. In order to manufacture such pieces in series, it is therefore not only a question of cutting them out of a strip, but of forming them, before cutting, according to a profile suitable for their functions.

It is known to manufacture such supplies from a metal band. If you want to make a date disc, for example, we start by stamping the tape to give it the three levels required by the profile of the disc. The internal toothing is then cut, then the disc is detached from the band by peripheral cutting. The stamped discs are then nickel-plated and washed and then transferred in bulk to a station where paint is applied to one of their faces. The paint is dried, then the date digits are traced.

The method just described has several disadvantages. It will be mentioned first of all that during the bulk transport to the paint station, the discs may warp or become entangled in one another so that the teeth may be damaged. This can lead to a high rejection rate and this following a control that takes a lot of time. It will also be noted that the nickel-plating and washing operations that precede the transport are long and expensive. Then, during the painting operation, which is also also long and expensive, it is very difficult, given the dimensions of the discs, to prevent paint from being deposited on the toothing, this deposit being liable to brake the disc after its assembly and thus make its operation unsatisfactory. It should be noted that before decaling the numbers, it is necessary to orient the disc so that the inscriptions are affixed in a very precise manner with respect to the teeth of this disc, otherwise said inscriptions may not be centered relative to each other. at the box office through which they are read. It will be understood that this operation also takes time. Finally, in the case of a metal disk, it will be understood that it is necessary to grease it where it rubs on the plate, which is an additional operation also taking time.

It will be observed that many of the disadvantages mentioned above would disappear if the metal disk was replaced by a plastic disk and if the bulk transport of these disks could be avoided.

We have already proposed date discs made of plastic material. This is the case, for example, in the document CH 554 554 which describes a manufacturing process where the date indicator is made of a flat plastic ring to which is ultrasonically welded a metal ring having an internal toothing. This embodiment avoids the paint overflow problem mentioned above, since the flat plastic ring does not have to be painted. However, other disadvantages remain in addition to the newly created here to use a two-component part inevitably expensive to achieve.

The document CH 544 332 also discloses a method for manufacturing a date indicator made entirely of plastic material, Here is implemented the plastic injection technique. However, reading the document shows that we must take enormous precautions to inject a disk whose thickness is of the order of 0.3 mm, both for the choice of the material for the making of the mold. This therefore leads to an expensive piece to manufacture and even impossible to manufacture if the thickness of the disk was to reach 0.15 mm, as can be the case for the disk made by means of the method of the present invention. The document FR 1 044 497 proposes a plastic dial also obtained by molding.

1. a) on fournit une feuille en matière plastique conformée en bande, la largeur de cette bande présentant une dimension suffisante pour fabriquer au moins un organe d'affichage;
2. b) on déforme la feuille par thermoformage pour lui conférer un profil correspondant à celui que présente l'organe d'affichage une fois terminé; et
3. c) on sépare l'organe d'affichage de la bande par découpage, ce découpage correspondant au contour extérieur dudit organe d'affichage.

Thus, to avoid many of the drawbacks enumerated above, the present invention advantageously makes use of a method which, although known in itself, has never been used to make a display member intended for a timepiece . Also the method of series production of a display member, especially for a timepiece, is it characterized in this new invention in that it comprises the following succession of steps:

1. a) providing a strip-shaped plastic sheet, the width of said strip being of sufficient size to fabricate at least one display member;
2. b) the sheet is deformed by thermoforming to give it a profile corresponding to that presented by the display member when completed; and
3. c) the display member is separated from the strip by cutting, this cutting corresponding to the outer contour of said display member.

Even more advantageously, the method enumerated above is completed by introducing after step b) and before step c), a step d) which consists in making at least one cut in the inner part of the display member, and a step e) which consists in affixing indications on said display member. Finally to complete the whole, and for reasons that will appear later, we can proceed, after step c) a stack of display members in a store.

The present invention also relates to a display member executed according to the method described above, the following description applying especially to describe a date disc.

• la figure 1 montre en perspective un organe d'affichage, en l'occurrence un disque de quantième fabriqué selon le procédé de l'invention,
• la figure 2 est une coupe faite selon un rayon du disque de la figure 1,
• la figure 3 est une vue en plan d'un autre organe d'affichage, en l'occurrence un cadran fabriqué selon le procédé de l'invention,
• la figure 4 est une coupe diamétrale dans le cadran de la figure 3, ce cadran étant réalisé selon un premier mode d'exécution,
• la figure 5 est une coupe diamétrale dans le cadran de la figure 3, ce cadran étant réalisé selon un second mode d'exécution,
• la figure 6 est une coupe dans une platine d'une pièce d'horlogerie, cette platine supportant un disque de quantième fabriqué selon l'invention,
• la figure 7 montre une feuille de matière plastique introduite dans un outil conformé pour le thermoformage et avant cette opération,
• la figure 8 montre la feuille de matière plastique dans l'outil conformé pour le thermoformage et après cette opération,
• la figure 9 montre la feuille de matière plastique thermoformée et hors de l'outil ayant servi au thermoformage,
• la figure 10 est une vue en plan de la feuille après l'opération de thermoformage,
• la figure 11 montre en coupe l'opération de découpage de la partie intérieure de l'organe d'affichage,
• la figure 12 est une vue en plan de la bande de matière plastique après le découpage de la partie intérieure de l'organe d'affichage,
• la figure 13 montre en coupe l'opération de découpage et de séparation de l'organe d'affichage de la bande,
• la figure 14 est une vue partielle d'un magasin équipé d'un plot cylindrique sur lequel peuvent s'empiler les organes d'affichage sortant de l'opération montrée en figure 13, et
• la figure 15 est une vue en perspective d'un magasin apte à recevoir une grande quantité d'organes d'affichage terminés.

The advantages and the interest of the present invention will now be explained in detail by means of the description which follows and the drawings which illustrate it by way of non-limiting example and in which:

• the figure 1 shows in perspective a display member, in this case a date disk manufactured according to the method of the invention,
• the figure 2 is a cut made according to a radius of the disc of the figure 1 ,
• the figure 3 is a plan view of another display member, in this case a dial made according to the method of the invention,
• the figure 4 is a diametrical cut in the dial of the figure 3 , this dial being made according to a first embodiment,
• the figure 5 is a diametrical cut in the dial of the figure 3 , this dial being made according to a second embodiment,
• the figure 6 is a cut in a turntable of a timepiece, this turntable supporting a date disc manufactured according to the invention,
• the figure 7 shows a sheet of plastic material introduced into a tool shaped for thermoforming and before this operation,
• the figure 8 shows the plastic sheet in the shaped tool for thermoforming and after this operation,
• the figure 9 shows the sheet of thermoformed plastic material and out of the tool used for thermoforming,
• the figure 10 is a plan view of the sheet after the thermoforming operation,
• the figure 11 shows in section the cutting operation of the inner part of the display member,
• the figure 12 is a plan view of the plastic strip after cutting the inner portion of the display member,
• the figure 13 shows in section the cutting operation and separation of the display member of the strip,
• the figure 14 is a partial view of a magazine equipped with a cylindrical stud on which can be stacked the display members emerging from the operation shown in FIG. figure 13 , and
• the figure 15 is a perspective view of a store capable of receiving a large amount of finished display members.

To manufacture a display member such as, for example, a date disk as shown in FIG. Figures 1 and 2 , a dial as shown in Figures 3, 4 and 5 , or any model, one can use a metal sheet or injection of plastic as has been mentioned in the preamble of this document. In order to eliminate the disadvantages of such methods listed in the same preamble, the present invention proposes the use of thermoforming.

To do this and as shown in particular figure 10 a strip-shaped plastic film 3 is provided. The width A of this strip has a dimension sufficient to manufacture at least one display member. The plastic material used in this process must be chosen to lend itself to thermoforming, for example a material of the PET type. The color of this material will be chosen in such a way that there is no need to paint the object, so that inscriptions can be directly affixed to it at the end of the process.

The band 3 is equipped with pilot holes 5 perforated by a machine recalling a progressive stamp that will load successively all stages of manufacture. The pilot holes 5 thus make it possible to accurately center the band between the various molds, stamps or printing devices which appear one after the other in the progressive stamp.

First, the thermoforming operation is carried out. For this, band 3, as shown by Figures 7 and 8 , is introduced between two tools 4 and 6 which allow such an operation according to various methods which will be described below. The thermoforming operation gives the display member a profile B as shown in FIG. figure 8 . The tape comes out of the tools 4 and 6 with a rough, non-flat, B-shaped surface, as shown in FIG. figure 9 .

Finally, the cutting operation performed according to the external contour that one wishes to give to the display member and which separates the piece from the strip 3 is carried out. This cutting operation could be done according to the circle 20 with dashes. interrupted from figure 10 so that one would pick up after cutting a kind of plate composed of a first ring 10, a second ring 11 and a bottom 13. The cutting operation which separates the display member from the band 3 is shown in figure 13 where we see a date disk 1 separated from the band 3, this separation being done by means of a punch 25 and a matrix 26.

The display member described above is circular. Of course he could take other forms to manufacture for example figurines of any kind that can be found on a timepiece. This is actually a display member made according to the most general acceptance of the invention namely a display member from a strip of plastic material, then thermoformed, then cut from this strip . It will be seen later that other additional operations are necessary if one wants to manufacture more complex display organs such as, for example, a date disc or a dial.

As already mentioned, thermoforming is known per se. It is used for objects of medium or large size such as, for example, food containers or swimming pools. The interested reader will read with profit the prospectuses of the Company Adolf Illig, Heilbronn, Germany, specialist of the subject. However, it has never been proposed so far to manufacture in this way small objects, including display devices for timepieces. In the watch industry, in fact, this method has so far had an unfavorable prejudice because of the very thin plastic sheets that it uses. How dare indeed propose a date disc whose thickness of the teeth hardly exceeds 0.15 mm? (see the document cited above CH 554 554 which avoids plastic teeth by proposing a metal ring gear reported on a plastic indicator ring, because, said the document, the plastic teeth have insufficient strength). In contrast to all this, the Applicant of the present invention has found that very thin sheets result in very light display members and, therefore, the stresses on the teeth are greatly reduced. In addition, the material used for thermoforming is generally robust, less brittle in any case than that used for injection. In summary, the plastic display members made according to the present invention have provided surprising and unsuspected effects so much that it is envisaged to use them now on a very large scale.

There are several ways to thermoform a plastic sheet.

Thermoforming by air pressure is shown to Figures 7 and 8 . A portion of the sheet 3 to be thermoformed is taken between two tools 4 and 6. This portion is heated beforehand and then injected, in the direction of the arrow E of the air into a channel 21 which is part of the tool 4. The air pressure then forces the sheet 3 to be applied to the bottom of the tool 6, this tool being in the form of a mold whose bottom has the profile that is desired to give the piece. A channel 22 is provided to evacuate the air between the sheet and the bottom of the mold 6, and this in the direction of the arrow F.

Thermoforming by vacuum or suction of air is also shown to Figures 7 and 8 . After arranging and heating the sheet 3 between the tools 4 and 6, the air contained between the sheet and the bottom of the tool is drawn in the direction of the arrow F. This suction forces the sheet 3 to come apply to the bottom of the tool 6 which is presented as a mold whose bottom has the desired profile to give the piece. A channel 21 allows an air inlet into the tool 4 for this operation and this according to the arrow E.

It will be noted that the tools 4 and 6 shown here for the two thermoforming operations are very rudimentary and are only a rough sketch to explain the principle of this thermoforming.

There is yet another way to deform a sheet by thermoforming. This involves compressing the previously heated sheet between two complementary molds having the desired profile. This method is self-evident and has not been considered useful here.

It has already been mentioned above that the process described in its simplest sense must be completed by other operations if it is desired, for example, to manufacture a date disc or a dial.

Thus, if one wishes to produce the date disc 1 shown in figure 1 after the thermoforming operation, but before the cutting operation which separates the disc 1 from the band 3, it is necessary to proceed with at least one cut-out 7 in the inner part of the disc 1. This operation is shown in FIG. Figures 11 and 12 . The figure 11 shows the disk 1 taken between a punch 23 and a die 24, these tools making it possible to proceed to the inner cutout 7. After cutting the inner portion 7, the strip 3 is presented as shown in figure 12 . The teeth 16 of the disc are formed and it will be enough then to cut the disc (see figure 13 ) according to the contour 20 to obtain a disk independent of the band.

Similarly, if one wishes to produce the dial 2 shown in figure 3 after the thermoforming operation, but before the cutting operation that separates the dial 2 from the band 3, it is necessary to cut 7 in the inside of the dial 2.

As the disc 1 and the dial 2 are generally provided with graphic indications (dates, marks, etc.) it will be understood, without it being necessary to illustrate this operation, that these indications will be affixed to the band at least before the operation that separates the display member 1 or 2 from the band 3. These inscriptions consist for the disc 1 in indications of dates 8 ( figure 1 ) and for the dial 2 as a mark 27 ( figure 3 ). Note that for the dial 2, these indications could be hour digits. These indications are transferred onto the body by means of a printing device which forms part of the progressive stamp.

At the time of separation of the display member of the band 3, it can collect this organ in a tray where it falls in bulk. However, it has been indicated above why this means of transport or storage is not adequate. Thus, advantageously, after the cutting operation that separates the member of the band, can we stack these bodies on each other in a magazine 9. This magazine 9 is shown partially in figure 14 . On a plate 28 is erected a cylindrical stud 29 whose diameter is slightly smaller than the diameter of the inner cutout 7 that the display member 1 or 2 presents. When said member is separated from the band 3, it then falls according to the arrow M in the store that is arranged under him. Its cutout 7 is introduced into the cylindrical stud 29 and thus a large number of display members can stack on each other avoiding any entanglement.

The figure 15 shows a magazine 9 can receive a large amount of display organs. So far, mention has been made of a strip 3 made of plastic whose width A has a dimension sufficient to manufacture at least one display member (see FIG. figures 10 and 12 ). However, it is possible to imagine a bandwidth 3 sized to manufacture at the same time a plurality of display members facing one another. Shop 9 of the figure 15 shows that the plastic strip is large enough to manufacture five bodies facing each other, these five members being manufactured at the same time and each falling simultaneously on cylindrical studs 29 arranged in alignment perpendicular to the direction of travel of the strip. The figure 15 shows that after stacking enough members 1 on each of the pads 29, the magazine 9 advances one step under the progressive stamp, the organs 1 then starting to stack on the pads 30 and so on. Such storage is advantageous for all the reasons mentioned above. It will also be mentioned that it considerably reduces the time of manipulation and control of the good of organs as well as the storage volume. For example, if the store has 5 x 8 cylindrical studs 29 and each stud can carry 125 members 1, this store can enclose 5,000 display organs arranged in perfect order and even away from dust s' it is covered with a lid. Such an arrangement can reduce the storage volume of about two-thirds of that taken by the conventional system of bulk storage.

It has been said that the process described above makes it possible to manufacture very advantageously display devices for timepieces. Two of the most common display devices manufactured according to this method will now be described.

The display member 1 shown in perspective at the figure 1 and in section at the figure 2 is a date disc. This disc comprises a first ring 10 outside and cut the strip according to the contour 20. On this ring 10 are affixed indications 8 relating to the date, more precisely numbers ranging from 1 to 31. The disc 1 still has a second ring 11 attached to the first and arranged lower than that first as the figure 2 . This depressed disposition of the second ring 11 defines a space 12 able to receive a disc of the days of the week. The disc 1 finally has a third ring 13 attached to the second and disposed lower than the latter as is always clearly visible on the figure 2 . An internal toothing 16 is cut in the third ring 13 to drive the disc. The disc 1 is therefore in the form of stairs whose profile is made by thermoforming as seen above.

As mentioned above, the thickness of the disc 1 and therefore of its successive stairs 10, 11 and 13 and the toothing 14 is of the order of 0.15 mm. This produces a very light disc easily drivable by its teeth which has proved sufficiently strong despite its small thickness.

The figure 6 is a cut in a platinum 15 of a timepiece. This plate supports the disk 1 manufactured according to the invention. The figure 6 shows that the third ring 13 of the disc 1 rests on a net 14 presented by the plate 15. The disc 1 being made of plastic material, there is therefore no need, as would be the case if this disc was metal, grease where the ring 13 rubs on the net 14. The figure 6 still shows the space 12 reserved for the disc of the days of the week as well as the star 32 which drives the toothing 16 of the disc 1. It will also be observed that the successive rings 10, 11 and 13 form natural ribs 33 and 34 which stiffen the disk and force it to remain flat, so that the friction takes place only under the ring 13 thus minimizing the friction torque exerted on the disk.

The display member shown in plan at figure 3 and in section Figures 4 and 5 is a dial 2. This dial 2 is made of plastic and has a contour 17 cut from the band. This dial has an inner cutout 7 showing a central opening 18 from which emerge the axes supporting the needles. Droplets 19, forming hour markers, are raised from dial 2 and are made by thermoforming according to one of the methods described above. The cuts of Figures 4 and 5 show how the drops are made 19. The dial 2 can be curved as shown in FIG. figure 4 , this curved being also obtained by thermoforming, or flat as shown in the figure 5 . A mark 27 may be traced on the dial 2 according to the method explained above. The dial could carry other inscribed inscriptions such as hour marks or colors marking the drops 19 more pronounced.

Claims (11)

1. Mass manufacturing method for a display element (1, 2), in particular for a timepiece, is characterized in that it includes the following series of steps:

   a) a sheet of plastic material in a tape (3) is provided, the width (A) of said tape having sufficient size to manufacture at least one display element;

   b) the sheet is deformed by thermoforming to give it a profile (B) corresponding to that of the display element (1, 2) once finished; and

   c) the display element (1, 2) is separated from the tape (3) by cutting, this cutting corresponding to the outer contour of said display element.
2. Method according to claim 1, characterized in that the thermoforming is achieved by air pressure (E), said pressure forcing the sheet to press against the bottom of a mould (6) having the desired profile.
3. Method according to claim 1, characterized in that the thermoforming is achieved by air suction (F), said suction forcing the sheet to press against the bottom of a mould (6) having the desired profile.
4. Method according to claim 1, characterized in that the thermoforming is achieved by compression, the sheet being held between two complementary moulds having the desired profile.
5. Method according to any of claims 1 to 4, characterized in that after step b) and prior to step c):

   d) at least one cut-out portion (7) is made in the inner portion of the display element.
6. Method according to claim 5, characterized in that at least said cut-out portion (7) forms a toothing (16) able to assure the driving of said display element.
7. Method according to claim 5 or 6, characterized in that after step d) and prior to step c),

   e) indications (8, 27) are affixed to said display element.
8. Method according to any of the preceding claims, characterized in that, during step b), the sheet is also deformed in order to transfer relief markings (19) onto said display element.
9. Method according to any of the preceding claims, characterized in that after step c) the display elements are stacked in a magazine (9).
10. Method according to any of the preceding claims, characterized in that said display element is a date disc which thickness is of the order of 0.15 mm.
11. Method according to any of the preceding claims, characterized in that the plastic material is of the PET type.

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