FR2789924A1 - Metallic band for making watch hands or indicator pointers has rectangular recesses arranged along the length of the strip and positioning holes in pairs along the edges for precise positioning prior to indicator cutting - Google Patents

Abstract

Procedure for fabricating indicators involves use of a metallic strip with rectangular recesses along its center arranged to move along in a conveyor belt fashion. The recesses are polished and positioning holes in the edge of the strip ensure that the positioning is very precise as the indicators are cut using a diamond-nosed chisel. An Independent claim is made for a metallic strip (10) with two rows of positioning holes (12) on either edge. Matching pairs are aligned on either edge of the strip with an axis (14) running through their centers and perpendicular to the longitudinal axis (16) of the strip. Rectangular recesses (18) run along the length of the strip with width (I) less than the pitch between positioning holes (12). The difference between width and pitch leaves a raised strip between the recesses that serves as protection to the strip during subsequent handling operations.

Description

PROCESS FOR PRODUCING A METAL STRIP FOR

  THE MANUFACTURE OF NEEDLES AND STRIP THUS OBTAINED

  The present invention relates to the manufacture of indicator needles, in particular those which are used in watches. The invention relates, more particularly, to a process for producing a metal strip intended for the manufacture of needles as well as the strip obtained by this process. The manufacture of watch hands is generally made from a thin strip of metal, generally brass. This strip is firstly worked using a succession of cutting and stamping stamps which form the barrel for fixing the needle and cut its

io external form.

  In luxury watches, the needle is then fixed on a support to be machined by means of a diamond chisel. This operation obviously requires that the needle is perfectly positioned, which requires a

  important time. This results in a high cost.

  In order to reduce production costs, it is known to polish the needles by means of a grinding wheel. This operation is certainly shorter than diamond machining but also more messy. The surface obtained is, moreover,

  less uniform. The reflections are thus less clear.

  Costs can be further reduced by polishing the strip before cutting the needles using cloth wheels impregnated with polishing paste. However, subsequent operations will subject the strip to an environment liable to scratch the polished surface, in particular when it is wound between

  two successive stages. Waste is therefore important.

  The main object of the present invention is to allow the manufacture of needles having a perfectly polished upper surface at low cost.

  despite the operations to which they are subjected after polishing.

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  More specifically, the invention relates to a process for producing a metal strip intended for the manufacture of indicator needles, characterized in that it consists in: - providing a metal strip comprising, on the at least one of its edges, parallel to its longitudinal axis, a line of positioning holes regularly spaced apart by a distance defining a pitch, - then to be produced in one of the faces of the strip, using '' a diamond chisel, a plurality of rectangular clearances with polished surface, regularly spaced, each having a longitudinal axis an axis perpendicular to that of the band and separated from each other by a flange ensuring the protection of the polished surfaces during

  subsequent manipulations of the tape.

  The needles are then shaped and cut from the strip of

classic way.

  Advantageously, the metal strip has, on each of its two edges, a line of positioning holes, the holes of the two lines corresponding in pairs so that the holes of a pair lie on an axis perpendicular to the longitudinal axis of the strip. Each release then has as its longitudinal axis the axis corresponding to a pair of

  holes and has a width less than the pitch.

  The clearances are preferably carried out using a machine fitted with an automatic drive device using the holes in the strip for

  advance it step by step so as to position it opposite the chisel.

  Advantageously, the central portion of the metal strip is raised relative to its two edges by a height slightly greater than the depth of the clearances, so that the chisel does not have to be moved vertically to penetrate the material. Thus, machining the clearances requires only a horizontal movement of the chisel, which

  simplifies the machine and saves time.

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  The hands used in watches have very varied profiles, their upper face being able to be rounded or to present two inclined planes defining an edge. According to the methods currently used, the needle is profiled in the desired shape after being cut. This means that it must be resumed to carry out the machining and polishing operations. Thanks to the invention, these operations can be considerably simplified, by giving the bottom clearances, during their machining by the chisel, the

desired shape.

  o0 Thus, according to one embodiment of the invention, the chisel has a straight cutting edge, defining a flat relief bottom. According to another embodiment, the chisel has a curved cutting edge, defining a rounded and convex relief bottom. According to yet another embodiment, the method uses two chisels whose cutting edges are flat and inclined, together defining a bottom of

  clearance of prismatic convex shape, with a median edge.

  The present invention also relates to a metal strip intended for the manufacture of indicator needles, produced according to the above method and which comprises: - on its edges, two lines of positioning holes regularly spaced by a distance defining a pitch and corresponding in pairs so that the two holes of a pair lie on an axis perpendicular to the longitudinal axis of the strip, and a plurality of rectangular clearances with polished surface each having for longitudinal axis one of the axes corresponding to a pair of positioning holes and of width less than said pitch, so as to leave between them a flange ensuring the protection of the polished surfaces during subsequent manipulations of

the band.

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  Advantageously, the central portion of the metal strip is raised relative to its two edges which have the positioning holes of a height slightly greater than the depth of the clearances.

  Other characteristics of the invention will emerge from the description which follows

  follow, made with reference to the appended drawing, in which: - Figure 1 is a top view of a strip according to the invention, - Figures 2 and 3 show the strip of Figure 1 in respectively longitudinal sections along 11- 11 and transverse according to 111-111, - Figure 4 schematically shows the automatic machine for producing a strip according to the invention; - Figures 5 and 6 show sections equivalent to those of Figures 2 and 3 for an alternative embodiment of the strip according to the invention, and - Figures 7 and 8 are partial longitudinal sections, to scale

  enlarged, with a strip according to the invention.

  The metal strip 10 shown in Figures 1 to 3 is made of brass. It typically has a thickness of 0.1 to 0.3 mm, a width of 15 to 30 mm and a length of several meters. It is usually wound on a

coil.

  The strip 10 has, on its edges, two lines of positioning holes 12 regularly spaced by a distance defining a pitch p, which is typically between 2 and 4 mm. The holes 12 of each line correspond in pairs so that the two holes of a pair are

  on an axis 14 perpendicular to the longitudinal axis 16 of the strip 10.

  A plurality of recesses 18, of rectangular shape, are made in the face of the strip 10, over its entire part between the two lines of positioning holes 12. Their bottom 18a has a polished surface such as that obtained by removing a chips using a chisel

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  diamond. Each of these clearances has for longitudinal axis one of the axes 14 corresponding to a pair of positioning holes. They have a depth e of the order of 0.01 mm. Their width! is less than the pitch p, so as to leave between them highlights 20 which will thus ensure the protection of the polished surfaces 18a during subsequent manipulations of the strip. To obtain such a strip, one begins by cutting the positioning holes 12 by means of a stamp. The strip 10 is then placed on a machine, as schematically shown in FIG. 4, making it possible to make the clearances 18 with a polished surface by a planing operation using a chisel 22 whose cutting edge has a

  length corresponding to width! clearances.

  More specifically, the machine of FIG. 4 comprises a table 24 on which the strip 10 is periodically applied, in successive portions, by means of a tightening tool 26 pneumatically controlled by means not shown. An automatic drive device, schematically represented by a wheel 28 provided with pins 30 cooperating with the holes 12, is used to advance the strip 10 step by step to position it precisely under the chisel 22. The latter is mounted on a door tool 32 which control means (not shown) make it possible to move vertically to bring the chisel 22 into contact with the strip, then horizontally in a direction perpendicular to its longitudinal axis 16 in order to realize, by planing, the clearances 18 with separate polished bottom some

others by highlights 20.

  The strip can then be placed on a conventional cutting line allowing both to cut around the edges of the needles, to make various openings therein to later dispose of the material

  luminescent and form the cannons for their fixation.

  As a variant, the operations relating to the formation of the openings and the

  barrels can be carried out before planing.

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  In the embodiment shown in FIGS. 5 and 6, there is the strip 10, the positioning holes 12, the clearances 18 and the highlights 20. Unlike the embodiment in FIGS. 1 to 3, the central portion 10a of the metal strip is then raised, relative to its two edges 10b which have the positioning holes 12, of a height h slightly

  greater than the depth e of the clearances 18.

  Thanks to this particular configuration of the strip, the movement of the chisel 22 can be only linear, the vertical movements no longer being necessary. The working speed and the complexity of the machine can thus be very considerably reduced. As an indication, it is then possible

  to machine more than forty clearances per minute.

  It is well known that the hands play an important role in the final appearance of the watch. It has been observed, in particular, that the needles, the upper surface of which is curved or have faceting, generate reflections

  i greatly improving the aesthetics of the watch.

  In the current state of the art, the crowning and the faceting are obtained by a stamping operation making it possible to deform the needle, followed by a polishing operation. Alternatively, and to obtain a higher quality product, the crowning can be achieved by means of a curved diamond chisel, while the facets are made using two chisels, the

  needles being arranged, piece by piece, on a suitable support.

  The present invention makes it possible to obtain the same result at a lower cost by making the clearances 18 with an adapted chisel. Thus, to obtain a clearance whose bottom has a rounded surface, it is possible to use a

  chisel 34, the cutting edge of which is concave, as shown in FIG. 7.

  To obtain a clearance whose bottom has a faceted surface, it is possible to work with two chisels with flat and inclined edge 36, arranged one

  behind the other, as shown in Figure 8.

  These two solutions are particularly well suited to the mode of

  embodiment described with reference to FIGS. 5 and 6.

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  The strip and the process which have just been described can be the subject of

  many variants, without departing from the scope of the invention.

  Thus, it is possible to produce balanced second hands by reducing the thickness of the strip in the part opposite the counterweight. The table will then be adapted so that the strip presses as much in the thin area as in the thick area. The thinning of the strip can be done before the planing operation, by milling, by scrolling the strip

under the strawberry.

  For certain applications, it is necessary for the thickness of the needle to be as small as possible, while having a relatively long barrel. By performing the barrel formation and then the planing operation, it is possible

  to obtain the expected result without having to repeat the needles one by one.

  However, this requires several chisel passes, as it is difficult

  remove more than 0.01 mm per pass.

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Claims (9)

  1. A method of producing a metal strip intended for the manufacture of indicator needles, characterized in that it consists of: - providing a metal strip (10) comprising, on at least one, from its edges, parallel to its longitudinal axis (16), a line of positioning holes (12) regularly spaced by a distance defining a pitch (p), - then to be made in one of the faces of the strip, using a diamond chisel (22), a plurality of rectangular clearances (18) with polished surface, regularly spaced, each having a longitudinal axis an axis (14) perpendicular to that (16) of the strip and separated the each other by a flange (20) providing protection   polished surfaces during subsequent handling of the strip.   2. Method according to claim 1, characterized in that: the metal strip comprises, on each of its two edges, a line of positioning holes (12), the holes of the two lines corresponding in pairs so that the holes of a pair are on an axis (14) perpendicular to the longitudinal axis (16) of the strip, and - each clearance (18) has for longitudinal axis the axis (14) corresponding to a pair of holes and has a width (I) less than said step (p).   3. Method according to one of claims 1 and 2, characterized in that   said clearances (18) are made using a machine provided with an automatic drive device (28) using the holes (12) of the strip to advance it step by step so as to position it in look of the chisel.   4. Method according to one of claims 1 to 3, characterized in that the   central portion (10a) of the strip is raised, relative to its two 9 2789924   edges (lOb), of a height (h) slightly greater than the depth (e) clearances.   5. Method according to one of claims 1 to 4, characterized in that the   chisel (22) has a straight cutting edge, defining a flat relief bottom.   6. Method according to one of claims 1 to 4, characterized in that the   chisel (34) has a curved cutting edge, defining a bottom of rounded and convex clearance.   7. Method according to one of claims 1 to 4, characterized in that it   uses two chisels (36) whose cutting edges are flat and inclined, together defining a prismatic relief base   convex, with a substantially median edge.   8. Metal strip (10) intended for the manufacture of indicator needles, characterized in that it comprises: - on its edges, two lines of positioning holes (12) regularly spaced by a distance defining a pitch (p ) and corresponding in pairs so that the two holes of a pair are on an axis (14) perpendicular to the longitudinal axis (16) of the strip, and - a plurality of rectangular clearances (18) with polished surface each having a longitudinal axis one of the axes (14) corresponding to a pair of positioning holes and of width (I) less than said pitch, so as to leave between them a flange (20) ensuring the protection of the polished surfaces during of   subsequent handling of the tape.   9. A strip according to claim 8, characterized in that its central portion (10a) is raised, with respect to its two edges (10b) which include the positioning holes, by a height (h) slightly   greater than the depth (e) of the clearances (18).