US3242664A - Watch case - Google Patents

Description

March 29, 1966 M. LEDERREY 3,242,664

WATCH CASE Filed NOV. 8, 1961 2 Sheets-Sheet 1 I/VVEN'roR March 29, 1966 LEDERREY 3,242,664

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United States Patent 3,242,664 WATCH CASE Marc Lederrey, Granges, Soleure, Switzerland, assignor to Schlup & Cie S.A., Berne, Switzerland, a joint-stock company Filed Nov. 8, 1961, Ser. No. 150,962 12 Claims. (Cl. 58-88) This invention relates to watch cases and in particular to wrist-watch cases having an attractive appearance.

The finest watch cases known in the art are made of gold and they are sometimes even furnished with enamel. These known watch cases are however very expensive and they have, moreover, to be carried with utmost care. Therefore, they would immediately be damaged, if they were carried in everyday life for manual labor or sport.

The only way hitherto known in the art for obtaining a watch case resistant to strong conditions of wear was to make it of steel and in particular of stainless steel. However, if such a watch case is repeatedly submitted to frictional engagement with hard objects, its finely polished outer surface portions exposed to contacts with foreign objects will soon be scratched and the watch case will nevertheless suffer substantial damage.

It is therefore an object of the invention to provide a watch case with an outer area reinforced in such a manner that it will not be damaged by impacts or frictional engagements with hard foreign objects.

It is also an object of the invention to provide a watch case with a reinforced outer area resistant to the oxidizing agents of the atmosphere.

Another object of the invention is to provide a watch case with a protecting outer area having a very attractive and durable appearance.

Still another object of the invention is to provide a watch case with an outer protecting and ornamental area (zone, portion or piece) consisting of a material containing a metal carbide being harder than topaz, such as tungsten or titanium carbide.

Metal carbides such as tungsten or titanium carbides are well known for their particularly high hardness and they have accordingly been used hitherto for tools on an important scale. Till now, nobody has, however, imagined that workpieces of common use could be manufactured on a commercial scale with such a material. This is probably due to the fact that a material containing a tungsten or titanium carbide cannot be effectively machined after it has been sintered by normal means. Diamond is indeed the only material by means of which particles can be removed from a workpiece made of a sintered tungsten or titanium carbide powder and even with a grinding wheel loaded with diamond powder, the amount of material which can be removed from such a workpiece during a reasonably long period is extremely Furthermore such a machining operation would involve too strong a wear of the grinding wheel. By means of electric sparks produced in a cell like those used for electrolytic polishing a noticeable amount of material can be removed from a workpiece consisting of a sintered tungsten or titanium carbide, but this method is very slow and can therefore only be resorted to with the manufacture of tools, the high cost of which will be compensated by the great number of workpieces it will be possible to manufacture by means of these tools.

To form a piece of a material containing tungsten or titanium carbide, an intimate mixture is first prepared, for instance in a ball mill, with a powder of the metal carbide and a powder of a bonding metal such as for instance cobalt, the particles of both powders there-by having very small sizes. This mixture is then submitted to a preliminary sintering so as to form a solid block which can however still be machined easily for instance by means of a diamond tool. Pieces having a shape similar to that of the workpieces which are to be manufactured are then cut from said block and introduced into a furnace to carry out the final sintering thereof. During the last operation a shrinkage of about 20% by volume can be observed. After this operation the pieces obtained receive their final hardness. Because of the important shrinkage observed, it did not appear very easy to form workpieces of hard metal with exact sizes by the method described. For the same reason it was also considered that workpieces of tungsten or titanium carbide formed by sintering should have the same overall cross-section to prevent the shrinkage from being accompanied by a distortion. The above mentioned reasons are probably those which till now kept manufacturers from making tungsten or titanium carbide workpieces of common use on a commercial scale and in particular from making watch cases of a sintered hard metal. Watch cases must of course have exact inner sizes and their cross-section varies between wide limits because of the wrist-band attaching lugs which have to be made integral with the case.

In spite of all the existing very strong prejudices against the idea of manufacturing watch cases of hard metal carbides, it has now been observed that these pieces, through their substantially varying crossasection, can be made on a commercial scale without great difficulties and with a quite satisfactory precision. To avoid distortions in sintering, the pieces are laid on a crucible, for instance of graphite, and a small weight is set thereupon.

The invention will now be described in detail with reference to the accompanying drawings which constitute a diagrammataic'al showing of three embodiments of the invention, which are however only disclosed by way of example.

In the drawings:

FIG. 1 is a perspective view of the first embodiment,

FIG. 2 is a part sectional view on a larger scale of the watch case represented in FIG. 1,

FIG. 3 is a bottom view of a piece of said watch case,

FIG. 4 is a side view partly in section of the watch case piece represented in FIG. 3,

FIG. 5 is a perspective view analogous to that of FIG. 1 showing the second embodiment,

FIG. 6 is a part sectional view on a larger scale of this second embodiment, and

FIG. 7 is a perspective view of the third embodiment.

The watch case of the first embodiment comprises an outer piece 1 of hard metal consisting of sintered tungsten carbide powder. This piece 1 is represented separately in FIGS. 3 and 4. As shown in FIGS. 1 and 2 this outer piece 1 constitutes the upper portion of the watch case, i.e. the portion which is particularly exposed to wear by coming in contact with foreign bodies. The watch case outer piece 1 is provided with a polished upper inner flat annular surface portion 2 surrounding the watch glass 3. Piece 1 also comprises a polished upper outer conical surface portion 4 adjacent surface portion 2 and extending downward therefrom. The two surface portions 2 and 4 constitute the upper metallic surface of the watch case and therefore the most important part of the visible outer portion thereof. Piece 1 further comprises an outer side surface extending downward from the periphery of surface portion 4, in a direction substantially parallel to the watch case axis. It can be noticed in FIG. 1 that this side surface comprises two portions each extending on one of the longer sides of the watch case and having substantially the same overall width. FIG. 1 also shows that said side portions not only extend over the watch case part adapted to receive the watch movement but also along projections 5 which serve as wrist-band attaching lugs. As viewed in FIG. 3 piece 1 comprises two pairs of lugs 5 extending in diametrically opposed directions from the annular central portion of said piece. A half cylindrical recess 6 is formed in one of the longer side portions of piece 1 to serve as a lodging for the Winding and hand setting member 7. The inner surface of piece 1 comp-rises three cylindrical bearing surfaces 8 which are separated from one another by two fiat shoulders 9. Piece 1 finally comprises two web sections 10 each extending over the two lugs of one of said pairs and connecting these two lugs to one another. As shown in FIG. 1 the upper surfaces of web sections 10 form part of the conical upper surface portion of piece 1. As more precisely explained hereinafter these web sections 10 are intended for preventing a distortion of piece 1 during sintering.

To manufacture the Watch case upper piece 1, a preliminary sintered block of tungsten carbide is first prepared as explained above. A piece having a shape similar to that of FIG. 1 is then cut out of that block by the usual techniques. This cutting ope-ration can be carried out by means of a diamond tool without excessive wear of said tool, because the preliminary sintered block has not yet received its final hardness. The shape of the piece cut out of said block has to be calculated with respect to that of piece 1 while considering the shrinkage of about by volume, which the preliminary sintered piece will be subjected to during the final sintering operation. To avoid a distortion of this piece during the final sintering operation, it is recommended to lay said piece on a crucible having a conical surface and preferably made of graphite, the conical surface of the crucible thereby having the same opening angle as the conical surface portion 4 of piece 1. Moreover, the work piece will have to be pressed on said crucible by means of a weight set on the thick portions of piece 1 represented in FIG. 3. After the sintering operation the piece obtained will only have to be submitted to a usual polishing operation of its upper surface comprising portions 2 and 4. This polishing operation can be carried out without any difliculty because of the simple geometrical form of portions 2 and 4.

To enable attaching a wrist-band to the watch case according to the invention, blind holes 23 are provided by means of a usual machine well known to those skilled in the art in the inner face of lugs 5, before piece 1 has been finally sintered. Conventional bars 11 can then be mounted on piece 1 in the same manner as with the known watch cases.

To manufacture a watertight watch case comprising a screwed bottom section, it is not advisable to make the whole case-band of hard sintered metal, since it would not be practical to provide screwthreads in such a piece. The watch case represented in FIGS. 1 and 2 therefore comprises an inner metal ring preferably made of stainless steel 12. A flange 13 adapted to receive the glass 3, a shoulder 14 serving as an abutting stop for the dial 15, a second shoulder 16 similarly serving as abutting stop for the base-plate of the watch movement 17, grooves 18 adapted for receiving latches (not shown) provided for fixing the watch movement 17 within ring 12, a recess 19 adapted for receiving an outer cylindrical portion of the watch case bottom 20, and an abutment 21 adapted for receiving a gasket 22 provided for ensuring a watertight seal between ring 12 and bottom 20, are provided in the inner surface of ring 12. Cylindrical bearing surface portions corresponding to the surface portions 8 of piece 1 and flat shoulders corresponding to shoulders 9 of piece 1 are machined on the outer surface of ring 12.

The outer protecting and ornamental piece 1 and the metal ring 12, adapted for receiving and supporting the glass 3, the watch movement 17 and the bottom 20, are rigidly fixed to one another, piece 1 thereby extending above and around ring 12. To perform fixing piece 1 and 12 to one another, the latter could be set with force fit into the former. To compensate the unavoidable manufacturing imprecisions, in particular to piece 1, it is however more advisable to glue said two pieces into one another, for instance by means of the glue on sale under the trademark Araldite. The glue layer extending between the corresponding cylindrical bearing surface portions and the corresponding shoulders of both pieces 1 and 12 will thereby not only ensure the fixing of said pieces to one another but also automatically compensate for the manufacturing imprecisions thereof.

FIG. 2 shows that the glass 3 is formed with a lower bulged surface and with an upper flat surface. To obtain a watertight seal between glass 3 and ring 12, a downwardly extending rim portion of glass 3 is pressed in a radial direction against a cylindrical surface portion of ring 12 by means of a strengthening ring, as usual. The depth of flange 13 is thereby chosen in such a manner that the flat upper glass surface will be located somewhat below the inner upper fiat surface portion 2 of piece 1, when the glass 3 and the piece 1 will have been set in place on to ring 12. Piece 1 will thus not only protect the watch case metal sections, but also the glass of this watch case.

In addition to the fact that the inner metal ring 12 can be manufactured very easily, for instance on an automatic lathe, this ring has also the advantage to provide a resilient cushion for piece 1, thereby avoiding a break of said piece upon a strong impact.

The watch case according to the second embodiment (FIGS. 5 and 6) differs from that of the first embodiment by the fact that the outer area of the watch case is here protected by means of hard metal elements having another shape than in the first embodiment. The watch case represented in FIGS. 5 and 6 comprises an annular piece 24 preferably made of stainless steel and having only its upper surface portions covered and protected by thin plates 25 and 26 of a sintered tungsten carbide. The annular piece 24 is provided with two pairs of lugs 27, 28 projecting in two diametrically opposed directions from said annular piece and integrally made therewith. As in the first embodiment lugs 27, 28 permit attaching a wrist-band 29 to the watch. To permit fixing the hard metal plates to piece 24 and lugs 27, 28, the upper surface of the annular piece 24- is fiat and the upper surface of each lug comprises a first fiat portion located in the same plane as said flat upper surface of piece 24, and a second portion inclined downward with respect to said first portion. Moreover, the second portions of the two lugs of the same pair are located in the same plane. Plate 25 comprises an annular portion 25a and two diametrically opposed ears 25b projecting from said annular portion. This piece 25 has the same overall thickness, so that manufacturing plate 25 does not present any difiiculty. The sizes of piece 25 are calculated so that said piece will entirely cover the upper surface of the annular portion of piece 24 as well as said first flat upper surface portions of lugs 27 and 28. Two plates 26 are further fixed over the inclined upper surface portions of lugs 27, 28, respectively. Plates 26 can furthermore be so arranged that they can be set at the side of plate 25, while avoiding any apparent joint therebetween. Plates 25 and 26 are preferably fixed to their supports 24, 27, 28 by soldering. Since plates 26 also have the same overall thickness, they can be manufactured by sintering without any difficulty.

As in the first embodiment, the stainless steel support 24, 27, 23 of the hard metal plates 25, 26 constitutes a resilient cushion preventing said plates from breaking upon impact. Since plates 25 and 26 have the same overall thickness, their upper visible surfaces can be polished together, before soldering these plates on piece 24. After the soldering operation, which can be carried out under a controlled atmosphere by passing the pieces through a furnace, on a continuously driven endless band, the watch case described only requires a short finishing operation to burnish their polished surfaces.

Instead of providing the watch case only with an outer reinforced area consisting of a hard metal carbide, it could obviously also be made entirely of said metal carbide as shown in FIG. 7. In this third embodiment the watch case comprises a massive piece 30 of sintered metal carbide having a substantially rectangular shape. Piece 30 is provided with a central circular lodging adapted for accommodating a watch movement therewithin. Two recesses 31 are also provided in the two shorter sides of piece 30 to enable attaching a wrist-band 32 to that piece. A bore (not shown) is finally provided across a longer side portion of piece 30, to ensure the passage of the winding and hand setting stem carrying member 33. The upper visible surface of piece 30 is fiat. This surface portion has sizes which are substantially greater than those of the glass 34 secured to piece 30. The upper surface of piece 30 can be polished in the usual manner, by means of a grinding wheel loaded with a finely divided diamond powder. Markings 35, extending in a radial direction with respect to the central circular opening of piece 30 and corresponding to the horal divisions of the dial, are provided in the upper surface of piece 30. These markings can be engraved with a pointed diamond tool before the final sintering operation. The two longer side surface portions of piece 30 are also fiat, so that they can easily be polished after the final sintering operation.

The cost price of the watch cases according to the invention is obviously higher than that of the stainless steel watch cases known in the art. This price is however substantially lower than that of gold watch cases.

The hardness of the material obtained by sintering a tungsten carbide powder is about 9 in the Mohs scale. Said material is thus harder than topaz, which is about 8 in the Mohs scale. Sintered tungsten carbide can even be as hard as Carborundum, which has a hardness of about 9.5 in said scale. A piece made of sintered tungsten carbide will therefore not be scratched by the usual materials. Only diamond and, in some instances, Carborundum are able to scratch such a piece. Moreover, tungsten carbide has the advantage to resist the oxidizing action of the corrosive agents of the atmosphere.

The improved watch case according to the invention has thus the advantage to keep its original appearance during a period which is practical-1y non-limited, even if it is carried under the most extensive conditions. Its polished outer surfaces will always show the same brightness and it will never be damaged by scratches.

The watch cases according to the invention can also be given new shapes comprising large polished visible surface portions.

The color of the material consisting of sintered tungsten carbide is darker than that of steel, thus giving the watch case according to the invention an original ornamental appearance.

Instead of using tungsten carbide to form the outer area of the watch case according to the invention, other metal carbides being about as hard as tungsten carbide, such as for instance titanium carbide, could obviously also be used.

Although some embodiments of the invention have been described in detail with reference to the accompanying drawings, various changes in the shape, sizes and arrangement of parts will appear obvious to those skilled in the art within the scope of the appended claims.

I claim:

1. A watch case having an exposed outer area containing a metal carbide and being harder than topaz.

2. A watch case as defined in claim 1, wherein said metal carbide is selected from the group consisting of sintered tungsten carbide powder and sintered titanium carbide powder.

3. A watch case having an exposed asymmetrical outer '6 surface portion, said surface portion being formed of a metal carbide harder than topaz.

4. A watch case as defined in claim 3, including a metal ring, a watch movement received therein and a transparent piece supported over said movement, wherein said surface portion surrounds said transparent piece and comprises a metal carbide cover member fixed above said ring and having wrist band attaching lugs integrally formed therewith.

5. A watch case as defined in claim 4, wherein said metal carbide cover member has a conical upper face.

6. A Watch case as defined in claim 5, wherein said metal carbide is selected from the group consisting of sintered titanium carbide powder and sintered tungsten carbide powder.

7. A watch case as defined in claim 3, wherein said watch case includes a transparent piece having a flat upper surface, and wherein said exposed asymmetrical outer surface portion comprises an outer metal carbide member having an upper portion adjacent said transparent piece flat upper surface and extending thereabove.

8. A watch case comprising a steel housing member adapted to receive a watch movement therein, said housing member having an upper surface portion, said housing member having an exposed metal carbide covering over said upper surface portion, said metal carbide covering being secured to said upper surface portion.

9. A watch case as defined in claim 8, wherein said metal carbide covering is secured to said upper surface portion by an adhesive.

10. A watch case as defined in claim 8, including a watch movement received in said housing member, and wherein said metal carbide covering comprises a polished upper inner fiat annular surface portion surrounding at least a portion of said movement, a polished upper outer conical surface portion extending downward from said flat annular surface portion, an outer side surface portion extending downward from the periphery of said conical surface portion, two pairs of wrist-band attaching lugs projecting from said outer side surface portion in two diametrically opposed directions and two web sections each extending above the whole length of the two lugs of one of said pairs and rigidly connecting these two lugs to one another, each of said web sections having an upper surface portion forming part of said polished upper outer conical surface portion.

11. A watch case as defined in claim 8, wherein said housing member has at least one outer cylindrical bearing surface and a shoulder adjacent to said bearing surface and extending perpendicular thereto; wherein said metal carbide covering has at least one inner cylindrical bearing surface and a shoulder adjacent and perpendicular thereto corresponding to said bearing surface and said shoulder of said housing member, and wherein said covering is rigidly fixed to said housing member by means of glue interposed between said cylindrical bearing surfaces and said shoulders.

12. A watch case as defined in claim 8, wherein said housing member is stainless steel .and includes a flat upper surface, two pairs of outwardly projecting wrist-band attaching lugs, each lug having a first flat upper surface extending in the same plane as the first mentioned'upper surface, and a second fiat upper surface inclined downward with respect to the first mentioned fiat upper surface, the second surface of the two lugs of each of said pairs being located in the same plane and wherein said metal carbide covering comprises a first thin plate made of metal carbide harder than topaz and including an annular portion and two diametrically opposed ears, said first thin plate being rigidly fixed onto housing member with said annular portion and said ears of said first thin plate thereby exactly covering the first mentioned fiat upper surface, and said first fiat upper surface of each of said lugs, and two plates made of a metal carbide harder 7 8 than topaz, each having the same thickness as said first 2,875,574 3/1959 Dinstman 58-90 plate and being rigidly fixed to said second upper snrfaces 3,097,897 7/1963 Taylor 29182.8 X of the two lugs of one of said palrs, each of said two FO E N S plates thereby being in contact With one of said ears.

5 447,373 3/1948 Canada.

References Cited by the Examiner 265,253 2/ 1950 Switzerland. UNITED STATES PATENTS 282,143 7/1952 Switzerland.

1,541,217 6/1925 Herbermann 5891 LEO SMILOW, Primary Examiner 2,120,562 6/1938 Laise 75 -221 X 2,147,329 2/1939 Willey 75 221 X 10 JOSEPH I-STRIZAK,Exammer- 2,462,839 3/ 1949 Brown 5890 X GERALD F. BAKER, Assistant Examiner.

Claims (1)

1. A WATCH CASE HAVING AN EXPOSED OUTER AREA CONTAINING A METAL CARBIDE AND BEING HARDER THAN TOPAZ.

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