GB2227402A

GB2227402A - Diamond gemstones

Info

Publication number: GB2227402A
Application number: GB8901711A
Authority: GB
Inventors: M Vainer Limited; Richard Louis Vainer; Martin Vainer
Original assignee: VAINER Ltd M
Current assignee: VAINER Ltd M
Priority date: 1989-01-26
Filing date: 1989-01-26
Publication date: 1990-08-01
Anticipated expiration: 2009-01-26
Also published as: GB2227402B; GB8901711D0

Abstract

A method of manufacturing a diamond of cabochon form wherein a diamond gemstone is polished on a radiussing machine to provide on at least a part thereof a smooth curved surface presenting no facets or facet edges. The machine comprises a skive plate 55 which is use rotates about on axis, that is itself rotated about an axis parallel thereto. The diamond is held by workpiece holder 51 which rotates about its longitudinal axis and is urged towards the skive plate 55. The holder 51 is supported on a carriage 54 which is movable to and from along a semi-circular track 58. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO GEMSTONES This invention relates to gemstones and in particular to diamond gemstones.

Rough diamonds in the form obtained from the mining industry fall into two main classes: those suitable only for industrial use (i.e. for incorporation in cutting and abrading tools and like articles) and those suitable for use as gemstones (i.e. as polished diamonds for incorporation in articles of jewellery). Each of these different classes is further divided into several categories of human endeavour specifically directed to the diamonds of that class. Such different categories include trading in the rough diamonds, manufacturing of the rough diamonds to a form suitable for their end use, manufacture of the final artcle incorporating the diamond(s), and trading in such final articles.All of these several categories are, to a very great extent, separate and distinct and it is almost unknown for, say, the manufacturing techniques employed in one of the said two main classes of diamonds to be adopted for diamonds in the other of said two main classes.

Moreover, in view of the hardness and distinctive grain structure of diamond, the manufacturing techniques adopted for other goods - even for non-diamond gemstones such as rubies, emeralds and the like - are usually wholly inapplicable to diamond gemstones.

A well-known form of polished non-diamond gemstone is the so-called "cabochon" which has a smooth, polished, curved surface presenting no facets or facet edges. This cabochon form can be produced without too much difficulty from nondiamond gemstone material but those persons concerned with diamond gemstones have generally accepted that such a form cannot be produced on a diamond gemstone.

According to one aspect of the present invention there is provided a diamond of cabochon form comprising a diamond gemstone polished to provide on at least a part thereof a smooth curved surface presenting no facets or facet edges.

Preferably said smooth curved surface extends over an area bounded by the circumference of the polished diamond gemstone.

Preferably the said curved surface is tangential to said circumference at all points along said circumference.

Advantageously said curved surface has the form of a parabola.

The said diamond cabochon may be incorporated in an article of jewellery, e.g. in a watch winder button.

According to another aspect of this invention there is provided a method of manufacturing a diamond of cabochon form wherein a diamond gemstone is polished to provide on at least a part thereof a smooth curved surface presenting no facets or facet edges.

Preferably said method comprises the steps of mounting the gemstone diamond by a collet (preferably a disposable collet) on the workpiece holder of a radiussing machine, and simultaneously (a) rotating the holder about a first axis extending longitudinally of the diamond, (b) moving the holder angularly to and fro about a second axis normal to the first axis, said second axis lying in or closely parallel to the surface of a skive plate having diamond abrasive thereon and in contact with the gemstone diamond, and (c) rotating the skive plate about a third axis which is not coaxial with the first said axis.

Optionally said skive plate may be mounted on means providing for rotation of the third axis about a fourth axis parallel to the third said axis. Said mounting means may comprise planetary gearing to provide a so-called orbital motion of the skive plate.

Said surface of the skive plate may be impregnayted and/or coated with said diamond abrasive.

Preferably the gemstone diamond is formed as a diamond cabochon to one side of an encompassing girdle and, to the other side is formed with a series of flat-faced facets, Advantageously said flat-faced facets include generally triangular facets meeting at a point substantially on the girdle axis but distal from the girdle itself. Said facets may be formed (e.g. by conventional gemstone diamond polishing techniques) either before or after cabochon forming of the gemstone diamond.

Alternatively the gemstone diamond may be formed as a diamond cabochon to each side of a girdle and such as to provide a substantially egg-shaped form.

By way of non-limiting example, embodiments of this invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a schematic side elevation showing various forms of a diamond cabochon of a first general shape, Figure 2 is a schematic side elevation showing various forms of a diamond cabochon of a second general shape, and Figure 3 is a schematic perspective view of a radiussing machine used in the production of the cabochon of Figs 1 and 2.

The illustrated cabochons of Figs 1 and 2 are each formed from a rough diamond of gemstone quality. The diamond, e.g. of generally octahedral shape is first sawn by a diamond cutting wheel, i.e. a thin metal wheel edge coated with diamond abrasive (bort), to produce one or more parts having a shape of generally tetrahedral form. The or each such tetrahedral part is then subjected to a "bruting" operation to round the corners of the generally square base of the tetrahedra until that base becomes substantially circular. This thus becomes the girdle 12 of the intended cabochon 10, 20 of Figs 1, 2. To form the intended cabochon 10 of Fig 1 the gemstone is then subjected to a polishing operation to form the multiplicity of facets 14 to one side of the girdle 12.These production steps of sawing, bruting and facet polishing are all well known in the conventional production of polished gemstone diamonds.

The partly-finished cabochon (i.e. just sawn and bruted for cabochon 20, or sawn, bruted and facet polished for cabochon 10) is then polished to final cabochon shape by the use of a radiussing machine 50 such as that of Fig 3. This machine comprises a generally cylindrical workpiece holder 51 having a disposble collet 52 mounted at one end adjacent a skive plate 55. The skive plate 55 is coated with a diamond abrasive powder and in use is rotated about an axis that is itself rotated about an axis parallel thereto, e.g. by a sun-and-planet gear wheel transmission. The workpiece holder 51 is urged longitudinally towards the skive plate 55 in a manner such that the pressure of engagement between the diamond, held by the holder's collet 52, can be adjustedl to a desired level.

A carriage 54 supports the workpiece holder 51 such that the holder can be rotated about its own longitudinal axis, e.g.

by a motor 56 and drive belt 57. The carriage 54 is itself rotatable (through 1800r along a horizontal track 58 of semi-circular shape having its own vertical axis lying substantially in the plane of the skive plate's abrasive surface.

In use, the diamond is rotated about its central axis by rotation of the workpiece holder 51 about its longitudinal axis, the diamond being urged with a predetermined force or pressure against the abrasive skive plate whilst the latter is rotated about its (planetary) axis. Simultaneously the carriage 54 is moved arcuately to and fro along the track 58 so that the projecting rough-diamond gemstone 10, 20 has its surface progressively polished by the skive plate 55 into the form of one of the part-spherical or part parabolic shapes 60 illustrated. It will be appreciated that the smooth, convexly curved surface 60 has no facets and, ideally, is formed to be contiguous with the girdle 12, i.e.

the girdle 12 is tangential to surface 60 at all points along the girdle's circumference. In effecting this surfacial continuity it is likely that the holding collet 52 may be ground away and be incapable of re-use.

It will be appreciated that the curved surface 60 may be provided before (rather than after) the polishing of the flat facets 14 of cabochon 10; that such flat facets can be omitted entirely - for example when that part of the cabochon is to be embedded in a jewellery article (e.g. a recessed winding or time-setting button of a watch); and that a corresponding curved surface can be formed to the opposite side of girdle 12 to form a somewhat egg-shaped cabochon 20 such as that of Fig 2. Other modifications of the present invention will be apparent to those skilled in this art, and all such modifications are to be deemed within the scope of the present invention.

Claims

1. A diamond of cabochon form comprising a diamond gemstone polished to provide on at least a part thereof a smooth curved surface presenting no facets or facet edges.

2. A diamond of cabochon form according to Claim 1, wherein said smooth curved surface extends over an area bounded by the circumference ' of the polished diamond gemstone.

3. A diamond of cabochon form according to Claim 1 or Claim 2, wherein the said curved surface is tangential to said circumference at all points along said circumference.

4. A diamond of cabochon form according to Claim 1 or Claim 2, wherein said curved surface has the form of a parabola.

5. A diamond cabochon according to any preceding Claim and incorporated in an article of jewellery.

6. A diamond cabochon according to any one of Claims 1 to 4 and incorporated in a watch winder button.

7. A diamond cabochon substantially as herein described with reference to and/or as illustrated in Fig 1 or Fig 2 of the accompanying drawing.

8. A method of manufacturing a diamond of cabochon form wherein a diamond gemstone is polished to provide on at least a part thereof a smooth curved surface presenting no facets or facet edges.

9. A method according to Claim 8 an comprising the steps of mounting the gemstone diamond by a collet on the workpiece holder of a radiussing machine, and simultaneously (a) rotating the holder about a first axis extending longitudinally of the diamond, (b) moving the holder angularly to and fro about a second axis normal to the first axis, said second axis lying in or closely parallel to the surface of a skive plate having diamond abrasive thereon and in contact with the gemstone diamond, and (c) rotating the skive plate about a third axis which is not coaxial with the first said axis.

10. A method according to Claim 9 wherein said collet is a disposable collet.

11. A method according to Claim 9 or Claim 10, wherein said skive plate is mounted on means providing for rotation of the third axis about a fourth axis parallel to the third said axis.

12. A method according to Claim 11, wherein said mounting means comprises planetary gearing to provide a so-called orbital motion of the skive plate.

13. A method according to any one of Claims 9 to 12, wherein said surface of the skive plate is impregnated and/or coated with said diamond abrasive.

14. A method according to any one of Claims 8 to 13, wherein the gemstone diamond is formed as a diamond cabochon to one side of an encompassing girdle and, to the other side is formed with a series of flat-faced facets.

15. A method according to Claim 14, wherein said flat-faced facets include generally triangular facets meeting at a point substantially on the girdle axis but distal from the girdle itself.

16. A method according to Claim 14 or Claim 15, wherein said facets are formed before cabochon forming of the gemstone diamond.

17. A method according to Claim 14 or Claim 15, wherein said facets are formed after cabochon forming of the gemstone diamond.

18. A method according to any one of Claims 14 to 17, wherein said facets are formed by conventional gemstone diamond polishing techniques.

19. A method of manufacturing a diamond of cabochon for#m according to Claim 7 and substantially as herein described.

19. A method according to any one of Claims 8 to 13, wherein the gemstone diamond is formed as a diamond cabochon to each side of a girdle and such as to provide a substantially egg-shaped form.

20. A method of manufacturing a diamond of cabochon form according to Claim 8 and substantially as herein described.

Amendments to the claims have been filed as follows 1. A diamond of cabochon form comprising a diamond gemstone polished to provide on at least a part thereof a smooth curved surface of substantially parabolic form presenting no facets or facet edges.

2. A diamond of cabochon form according to Claim 1, wherein said smooth curved surface extends over an area bounded by the circumference of the polished diamond gemstone.

4. A diamond cabochon according to any preceding Claim and incorporated in an article of jewellery.

5. A diamond cabochon according to any one of Claims 1 to 4 and incorporated in a watch winder button.

6. A diamond cabochon substantially as herein described with reference to and/or as illustrated in Fig 1 or Fig 2 of the accompanying drawing.

7. A method of manufacturing a diamond of cabochon form in which a diamond gemstone is polished by a radiussing machine to provide on at least a part thereof a smooth curved surface of substantially parabolic form presenting no facets or facet edges.

8. A method according to Claim 7 and comprising the steps of mounting the gemstone diamond by a collet on the workpiece holder of a radiussing machine, and simultaneously (a) rotating the holder about a first axis extending longitudinally of the diamond, (b) moving the holder angularly to and fro about a second axis normal to the first axis, said second axis lying in or closely parallel to the surface of a skive plate having diamond abrasive thereon and in contact with the gemstone diamond, and (c) rotating the skive plate about a third axis which is not coaxial with the first said axis.

9. A method according to Claim 8, wherein said collet is a disposable collet.

10. A method according to Claim 8 or Claim 9, wherein said skive plate is mounted on means providing for rotation of the third axis about a fourth axis parallel to the third said axis.

11. A method according to Claim 10, wherein said mounting means comprises planetary gearing to provide a so-called orbital motion of the skive plate.

12. A method according to any one of Claims 8 to 11, wherein said surface of the skive plate is impregnated and/or coated with said diamond abrasive.

13. A method according to any one of Claims 7 to 12, wherein the gemstone diamond is formed as a diamond cabochon of substantially parabolic form to one side of an encompassing girdle and, to the other side is formed with a series of flat-faced facets.

14. A method according to Claim 13, wherein said flat-faced facets include generally triangular facets meeting at a point substantially on the girdle axis but distal from the girdle itself.

15. A method according to Claim 13 or Claim 14, wherein said facets are formed before cabochon forming of the gemstone diamond on the radiussing machine.

16. A method according to Claim 13 or Claim 14, wherein said facets are formed after cabochon forming of the gemstone diamond on the radiussing machine.

17. A method according to any one of Claims 13 to 16, wherein said facets are formed by conventional gemstone diamond polishing techniques.

18. A method according to any one of Claims 7 to 12, wherein the gemstone diamond is formed as a diamond cabochon of substantially parabolic form to each side of a girdle and such as to provide a substantially egg-shaped form.