GB1576227A

GB1576227A - Method of manufacturing a component part of a clock or watch movement

Info

Publication number: GB1576227A
Application number: GB3197477A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-29
Filing date: 1977-07-29
Publication date: 1980-10-01
Also published as: FR2360112A1; JPS5337064A; DD131206A5; DE2733810A1

Description

(54) METHOD OF MANUFACTURING COMPONENT PART OF A CLOCK OR WATCH MOVEMENT (71) I, GEORGES DUCOMMUN, a Swiss citizen of St. Niklaus 91, 4532 Feldbrunnen, Switzerland, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a method of manufacturing, by die-casting (pressuremolding) from aluminium metal, a component of a clock or watch movement.

This invention further relates to a part for a clock or watch movement, obtained by such method.

It is known that conventional methods of manufacturing component parts such as base-plates and bridges for watches by milling, facing and die-cutting of pieces of yellow brass are time-consuming and expensive, as they require intensive work. This is evident from Swiss Patent 90989 granted on October 1st 1921 to Fabriques des Montres Zenith, in which a watch movement is described wherein at least a part of the supporting elements are of pressure-molded (die-cast) metal.

However, die-cast metal is not suited for use in clock and watch movements for the reason that its surface properties, i.e. (finish, mechanical stability, accuracy of dimensions and weight) are unsatisfactory. Furthermore, in Swiss Patent 464 804 granted on October 31st, 1968 to Fabrique d'Horlogerie Chs. Tissot & fils SA, a movement is described which consists to a large extent of parts made from injection-molded synthetic plastics material. However, watches made in this manner have also not lived up to expectations because the plastics material does not meet with the requirements made on such parts, in particular when used in watch movements, with respect to accuracy of dimensions and resistance to mechanical stress. Precision and quality watches can not be manufactured satisfactorily by this known method.

The use of brass has its own drawbacks, especially in machining it, in which case its inhomogenous structure is unsatisfactory, especially when shaping and cutting a part, and also in finishing treatment because of its tendency to become distorted and subject to internal stresses. Therefore, other materials were sought for the manufacture of the base plate and the bridges of the watch movement. For example, a movement has been developed the supporting plates of which consist of anodically oxidized aluminum metal, as described in Swiss Patent 316 843 granted on December 15, 1956 to Baumgartner Fieres S.A..Watch movements made of aluminum parts have not been wholly satisfactory, however, because the machining of aluminum is as expensive as that of brass and this treatment tends to weaken or even destroy the protective aluminum oxide layer which always covers such parts. Although the use of brass as a working material for the base plate and the bridges of watch movements has its drawbacks and the clock industry has sought for and used other materials and methods, by far the greatest part of mechanical watches still contain base plates and bridges made of brass, and this in spite of the often considerable drawbacks mentioned hereinbefore.

A first object of the present invention is to provide a component part of the initially described type for clock or watch movements which part does not have any of the afore-mentioned drawbacks of the known conventional base-plates and bridges and which is simple and cheap to manufacture.

A second object of the invention is to provide a method for the manufacture of this clock or watch part.

Furthermore, the invention solves the problem of making a watch part that can be manufactured in finished form with a mini mum of manufacturing steps, so that it can be produced readily and cheaply.

Also, the component part must be made in such a manner as to meet with all requirements as to quality of finish, accuracy of dimensions and mechanical resistance necessary for using the same in manufacturing a quality watch.

Moreover, the component part should have a surface hardness and resistance to wear, at least in the portions which cooperate with relating parts, with the object of making the use of rubies or sapphires or the like elements superfluous.

The method of manufacturing this component part should be simple, cheap and safe. It should produce, with as few operations as possible, a watch part that preferably does not require complicated aftertreatment of individual portions thereof, and should permit the use of long-life robust tools. Furthermore, it should be suitable for performance by any watchmaker without difficulties, affording high-quality watch parts the surface finish, precision and mechanical stability of which meet a high standard.

According to one aspect of the invention there is provided a method of manufacturing a component part of a clock or watch movement, which part has at least one recess or projection or both destined to be contacted by another part of said clock or watch movement in the assembled state and comprising; pressure molding said part from aluminum metal with slightly less depth or width or both depth and width than the final dimensions of said recess or with slightly greater height or breadth or both height and breadth of the final dimensions of said projection; pressure-aftertreating said part with a finishing tool in a single linear working movement, which tool is arranged to increase said recess in depth or in width or in both depth and width, or decrease said projection in height or in breadth or in both height and breadth, or simultaneously increase said recess and decrease said projection in the respective manner stated, thereby giving said part its exact dimensions for assembly in said clock or watch movement; coating said part with a layer of an aluminium oxide compound by carrying out the pressure molding and pressure-aftertreating steps at sufficient temperature and length of time to oxidize said part; degreasing and etching the outer surface of said covering layer; and aftertreating the part obtained thereafter at an elevated temperature for several hours with water in the liquid or gaseous phase until the outer part of said layer of aluminium oxide compound has been converted to boehmite (AlO(OH)).

Preferably, the excess dimensioning of such recess and/or projection amounts to from 5/100th mm to 1/lOth mm.

In a preferred mode of carrying out the method according to the invention in practice, the method steps are carried out at such temperature and at such length that the resulting component part of pressuremolded aluminium is covered with a layer of aluminium-oxygen compound having a thickness of from 1 to 10 microns.

Advantageously, the temperature and duration of the aftertreating step is so chosen that the thickness of the boehmite layer is from 0.5 to 2 microns.

The aftertreatment step can be carried out with boiling deionized water or with water-vapour having a temperature of from 100 to 1500C. It is preferably carried out for a duration of from fifteen to twenty hours.

According to a further aspect of the invention there is provided a component part of a clock or watch movement which part has at least one recess or projection or both for contact by another part of said clock or watch movement in the assembled state, said component part comprising an at least partly pressure hardened aluminium pressure molded part having an at least one micron thick aluminium oxide compound first layer and a second layer of boehmite (ALO(OH)) Preferably the first layer consists of Al203.

The covering aluminium-oxygen compound layer has preferably a thickness of from 1 to 10 microns, and the boehmite part of the aluminium-oxygen compound layer has a preferred thickness of from 0.2 to 2 microns; and has a microhardness of from 500 to 650 units on the Vickers scale.

In the component part according to the invention, portions thereof being pressurehardened are preferably parts designed to be subject to mechanical stresses when the said component part is in place in the assembled clock or watch movement.

An appropriately shaped component part according to the invention can serve as the lever of the escapement, which lever is free from rubies.

A decisive advantage of the preferred method of manufacturing component parts according to the invention resides in the simplicity and small number of method steps involved.

The tool which is used in the finishing step which precedes the oxidizing treatment preferably has punching parts and stamping parts by means of which the holes and recesses or projecting surfaces which are subject to stress are reworked in the crude component part to achieve the required surface finish and the exact dirnensions and at the same time to harden the material in the reworked portions of the component part.

The component parts according to the invention can be assembled optionally in combination with other parts produced by earlier, conventional methods, whereby a fully operational, highly satisfactory clock or watch movement of particularly inexpensive manufacture is obtained, which can be very light and of flat, thin profile.

Preferably, rotating parts, i.e. wheels, are made of hard synthetic polymeric material while all supporting parts are preferably made from aluminium.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a sectional view of a first embodiment of a component part and a reworking tool applied thereto, Figure 2 shows a sectional view of part of a base-plate or bridge, Figure 3 shows in partially sectional view the left hand portion of a watch movement, containing component parts according to the invention, Figure 4 shows a partially sectional view of the right hand portion of the watch movement shown in Figure 3, and Figure 5 shows a top view of several component parts of the watch movement shown in Figures 3 and 4.

When die-casting (pressure molding) a component part 1 from pure aluminium care is taken that as far as possible all portions of the component part which are not due to be submitted to a special stress in the watch, i.e. stress caused by supporting other movement parts, e.g. pivoting wheel hubs and the like, are given their exact final dimensions and shape at this first stage, so that they need not be reworked. All other portions of the component part being manufactured are formed during die-casting with excess material giving them higher protrusions or less deep recesses or narrower holes than are consonant with the exact final dimensions required. This makes it possible to depress such portions with the aid of a linearly moved finishing or reworking tool, parts 2, 3, 4, 6 and 9 of which are shown in Figure 1.

Due to the reworking treatment, these portions of the component part are given greater hardness relative to the other portions of the component part manufactured, while giving such portions at the same time their final exact heights, depths and/or widths.

The component part 1 which is shown in Figure 1 is a base plate which is inserted in the aforesaid reworking tool which is preferably part of a press. The tool comprises a lower tool casing half 2 provided with firmly inset pegs 3 having shoulders 5 which pegs serve to receive and position the base plate 1. Base plate 1 is exactly positioned with respect to its location and to its relative height on the tool base part 2 by the engagement of pegs 3 of the tool in openings 3b which are provided in collar element la protruding on the upper side of base plate 1, as well as by the abutment of the underside of collar element la on shoulders 5 of pegs 3.

The thickness of collar element la of base plate 1 is precisely determined by slight compression of the material between the precisely finished shoulders 5 of pegs 3, and the equally precisely finished surface portions of the upper tool casing half 4 which are at a determined distance above the shoulders 5. Moreover, those surface portions of base plate 1 which abut against the precisely finished tool faces are given a finish the quality of which corresponds to that of the tool.

In the upper tool casing half 4 there is mounted rigidly a stamp 6, the lower portion 6a of which is surrounded by an annular shoulder 6b and serves to trim an opening 7 in base plate 1 giving it its final exact width.

Here again, the thickness of annular rim 1b about opening 7 of the base plate 1, which thickness is measured between the shoulder 6b of stamp 6 and the zone of lower casing half 2 located directly below shoulder 6b, is precisely determined by slight compression of material in this region, whereby a desired surface quality and the exact height under the face of stamp 6 (shoulder 6b) can be achieved simultaneously. The slightly raised collar element 8 underneath stamp 6 is of limited radial diameter taken in the plane of the face of base plate 1 in this region, so that stamp 6 does not have to deform more material than is absolutely necessary.

Finally, a trimming pin 9 rigidly mounted in upper casing half 4 serves to trim a hole 9a, perforating the entire thickness of base plate 1, trimming taking place along an upper portion of the length of hole 9a.

Other stamps can be provided in the upper or in the lower casing halves of the reworking tool to serve for punching holes of final exact dimensions in the portions of the crude component part having unperforated material.

An embodiment of a component part having such perforation is shown in Figure 2. Cavities 10 and 11 are formed on opposite sides of the crude base plate 1 during the first method step, leaving a thin wall portion 12 therebetween which wall portion is then perforated by a punching stamp (not shown) of a reworking tool.

The production of a component part according to the invention is on the whole very simple and comprises only two shaping work steps, i.e. die-casting (pressuremolding) and thereafter finishing the crude part with a reworking tool which does the whole reworking in a single linear back and- forth movement. This means considerable saving in time and expense compared with the conventional methods for manufacture of base plates and bridges presently requiring up to forty individual working steps.

The thus manufactured component part 1 which does not require any further mechanical treatment and which is covered with the usual layer of an aluminum-oxygen compound which protects it against damage, is then given a special treatment which imparts to those portions which must have special resistance to strains an additional surface hardness so that the resistance of the component part is further enhanced.This treatment converts an outermost part of the aluminum-oxygen compound layer to boehmite (AlO(OH)) and comprises degreasing and etching the last-mentioned layer and then bringing it into contact with boiling deionized water or with water vapour having a temperature of about 100 to 1500C. On the one hand, this strengthens the aluminum-oxide layer naturally present on aluminum surfaces in contact with the air and, on the other hand, forms the abovementioned cover layer of boehmite on top of the bulk of the aluminum oxide (Al203) layer. Initially, the boehmite layer grows very rapidly, and final layer thicknesses of between 0.5 to 2 microns can be obtained within 15 to 20 hours.The layer of boehmite has an exceptional micro-hardness of 450 to 700 units on the Vickers scale, i.e. much greater than the Vickers hardness of a ruby or sapphire and of several times the resistance to abrasion of these jewels. In this manner, supporting faces are given a surface hardness which renders the use of jewels as bearings superfluous.

It has been found that those portions of the component parts according to the invention which undergo wear due to abrasion are covered by a boehmite layer of 0.2 to 0.5 microns which can be achieved by an oxidation-treatment of less than 15 hours.

The watch movement shown in Figures 3 and 4 comprises a conventional barrel 31 made of brass, the arbor 32 of which is supported in the base plate 33 and in a barrel bridge 34 and carries the ratchet wheel 35 made of synthetic resin plastics material. Figure 3 further shows a large arc wheel 36 a small arc wheel 37 and a second-hand wheel 38, all of which are made of synthetic resin plastics material and each of which is mounted on a steel shaft provided with a pinion. The second-hand wheel 38 is coupled to the second-hand 40, which latter is also made of synthetic resin plastics material, via the second-hand shaft 39. The second-hand wheel 38 drives the escape wheel 41 which in turn drives the balance via lever 42 and roller 13.

The escapement is of especially simple structure in that the one-piece lever 42 bears no rubies or steel pins; it is generally planar, except for the bent-out guard pin 15. Likewise, the roller 13 is planar, except for the inserted impulse stone 16, The escape wheel 41 and the lever 42 may be made of anodized aluminum. The balance shaft 17 is axially secured at both ends by anodized aluminum plates 18 and 19, respectively, whereof at least plate 18 is arranged to be somewhat elastically flexible so that it serves as a shock absorber. All shafts are directly pivoted in bearing bores of base plate 33 and in the bridges shown in these Figures. Base plate 33 and the bridges shown are made of anodized aluminum.The bearings are given the necessary high surface resistance by the pressure working and oxidizing treatment described above, which resistance corresponds to that of rubies, so that these bearings suffer practically no abrasion. The escape wheel 41 and lever 42 may also of course be treated by said oxidizing technique subsequent to pressure working to form the parts as heretofore described.

The wheels and shafts which are directly driven by the barrel in Figure 3 are preferably all made of synthetic resin plastics material (only the hour-hand wheel 20 and the hour-hand tube 21 are thus depicted).

Due to this use of very light-weight movable parts, especially of a light-weight escape wheel and lever, only a slight torque is needed. Therefore, the barrel can be made relatively low and consequently the whole watch movement has a low profile.

This is also due to the fact that the simple, flat lever extends substantially in the plane of the escape wheel, so that the assembled escapement is of reduced height.

The invention offers several decisive advantages over the presently known method of manufacturing component parts by making it possible to produce them of high quality in a much less expensive and simpler manner. Moreover, this permits the manufacture of quality and precision watches on a large scale and without use of expensive jewel bearings or bushes. These advantages cannot be attained solely by use of aluminum as material for component parts. It is necessary to treat the aluminum by the method according to the invention because otherwise its surface hardness and mechanical resistance would be insufficient for component parts of watches.

WHAT WE CLAIM IS: 1. A method of manufacturing a component part of a clock or watch movement, which part has at least one recess or projection or both destined to be contacted by another part of said clock or watch movement in the assembled state and comprising:

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. and- forth movement. This means considerable saving in time and expense compared with the conventional methods for manufacture of base plates and bridges presently requiring up to forty individual working steps. The thus manufactured component part 1 which does not require any further mechanical treatment and which is covered with the usual layer of an aluminum-oxygen compound which protects it against damage, is then given a special treatment which imparts to those portions which must have special resistance to strains an additional surface hardness so that the resistance of the component part is further enhanced.This treatment converts an outermost part of the aluminum-oxygen compound layer to boehmite (AlO(OH)) and comprises degreasing and etching the last-mentioned layer and then bringing it into contact with boiling deionized water or with water vapour having a temperature of about 100 to 1500C. On the one hand, this strengthens the aluminum-oxide layer naturally present on aluminum surfaces in contact with the air and, on the other hand, forms the abovementioned cover layer of boehmite on top of the bulk of the aluminum oxide (Al203) layer. Initially, the boehmite layer grows very rapidly, and final layer thicknesses of between 0.5 to 2 microns can be obtained within 15 to 20 hours.The layer of boehmite has an exceptional micro-hardness of 450 to 700 units on the Vickers scale, i.e. much greater than the Vickers hardness of a ruby or sapphire and of several times the resistance to abrasion of these jewels. In this manner, supporting faces are given a surface hardness which renders the use of jewels as bearings superfluous. It has been found that those portions of the component parts according to the invention which undergo wear due to abrasion are covered by a boehmite layer of 0.2 to 0.5 microns which can be achieved by an oxidation-treatment of less than 15 hours. The watch movement shown in Figures 3 and 4 comprises a conventional barrel 31 made of brass, the arbor 32 of which is supported in the base plate 33 and in a barrel bridge 34 and carries the ratchet wheel 35 made of synthetic resin plastics material. Figure 3 further shows a large arc wheel 36 a small arc wheel 37 and a second-hand wheel 38, all of which are made of synthetic resin plastics material and each of which is mounted on a steel shaft provided with a pinion. The second-hand wheel 38 is coupled to the second-hand 40, which latter is also made of synthetic resin plastics material, via the second-hand shaft 39. The second-hand wheel 38 drives the escape wheel 41 which in turn drives the balance via lever 42 and roller 13. The escapement is of especially simple structure in that the one-piece lever 42 bears no rubies or steel pins; it is generally planar, except for the bent-out guard pin 15. Likewise, the roller 13 is planar, except for the inserted impulse stone 16, The escape wheel 41 and the lever 42 may be made of anodized aluminum. The balance shaft 17 is axially secured at both ends by anodized aluminum plates 18 and 19, respectively, whereof at least plate 18 is arranged to be somewhat elastically flexible so that it serves as a shock absorber. All shafts are directly pivoted in bearing bores of base plate 33 and in the bridges shown in these Figures. Base plate 33 and the bridges shown are made of anodized aluminum.The bearings are given the necessary high surface resistance by the pressure working and oxidizing treatment described above, which resistance corresponds to that of rubies, so that these bearings suffer practically no abrasion. The escape wheel 41 and lever 42 may also of course be treated by said oxidizing technique subsequent to pressure working to form the parts as heretofore described. The wheels and shafts which are directly driven by the barrel in Figure 3 are preferably all made of synthetic resin plastics material (only the hour-hand wheel 20 and the hour-hand tube 21 are thus depicted). Due to this use of very light-weight movable parts, especially of a light-weight escape wheel and lever, only a slight torque is needed. Therefore, the barrel can be made relatively low and consequently the whole watch movement has a low profile. This is also due to the fact that the simple, flat lever extends substantially in the plane of the escape wheel, so that the assembled escapement is of reduced height. The invention offers several decisive advantages over the presently known method of manufacturing component parts by making it possible to produce them of high quality in a much less expensive and simpler manner. Moreover, this permits the manufacture of quality and precision watches on a large scale and without use of expensive jewel bearings or bushes. These advantages cannot be attained solely by use of aluminum as material for component parts. It is necessary to treat the aluminum by the method according to the invention because otherwise its surface hardness and mechanical resistance would be insufficient for component parts of watches. WHAT WE CLAIM IS:

1. A method of manufacturing a component part of a clock or watch movement, which part has at least one recess or projection or both destined to be contacted by another part of said clock or watch movement in the assembled state and comprising:

(a) pressure molding said part from aluminium metal with slightly less depth or width or both depth and width than the final dimensions of said recess or with slightly greater height or breadth or both height and breadth of the final dimensions of said projection; (b) pressure-aftertreating said part with a finishing tool in a single linear working movement, which tool is arranged to increase said recess in depth or in width or in both depth and width, or decrease said projection in height or in breadth or in both height and breadth, or simultaneously increase said recess and decrease said projection in the respective manner stated, thereby giving said part its exact dimensions for assembly in said clock or watch movement;; (c) coating said part with a layer of an aluminium oxide compound by carrying out steps (a) and (b) at sufficient temperature and length of time to oxidize said part; (d) degreasing and etching the outer surface of said covering layer; and (e) aftertreating the part obtained from step (d) at an elevated temperature for several hours with water in the liquid or gaseous phase until the outer part of said layer of aluminium oxide compound has been converted into boehmite (AlO(OH)).

2. A method as claimed in Claim 1, wherein said layer of aluminium oxide compound has a thickness of from 1 to 10 microns.

3. A method as claimed in Claim 1 or 2, wherein said recess is undersized and/or said projection is oversized by 5/100th mm to 1/lOth mm.

4. A method as claimed in Claim 2, wherein the temperature and duration of step (e) is so chosen that the thickness of the boehmite layer is from 0.2 to 2 microns.

5. A method as claimed in Claim 4, wherein step (e) is carried out with boiling deionized water.

6. A method as claimed in Claim 4, wherein step (e) is carried out with water vapour having a temperature of from 100 to 150 C.

7. A method as claimed in Claim 5, wherein step (e) is carried out during a duration of from fifteen to twenty hours.

8. A component part of a clock or watch movement which part has at least one recess or projection or both for contact by another part of said clock or watch movement in the assembled state, said component part comprising an at least partly pressure hardened aluminium pressure molded part having an at least one micron thick aluminium oxide compound first layer and a second layer of boehmite (AlO(OH)).

9. A component part as claimed in Claim 8, wherein said first layer is Al203.

10. A component part as claimed in Claim 9, wherein said first layer has a thickness of from 1 to 10 microns.

11. A component as claimed in Claim 10, wherein said second layer has a thickness of from 0.5 to 2 microns.

12. A component as claimed in Claim 11, wherein said second layer has a microhardness of from 500 to 650 units on the Vickers scale.

13. A component part as claimed in Claim 8, wherein said component part is designed to be subjected to mechanical stresses when mounted in place in said clock or watch movement.

14. A component part as claimed in Claim 8, comprising a ruby free escapement lever.

15. A method of manufacturing a component part of a clock or watch movement substantially as hereinbefore described with reference to the accompanying drawings.

16. A component part of a clock or watch movement substantially as hereinbefore described with reference to the accompanying drawings.