GB2194913A

GB2194913A - Notching gemstones

Info

Publication number: GB2194913A
Application number: GB08719469A
Authority: GB
Inventors: Efraim Nativ
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-08-21
Filing date: 1987-08-18
Publication date: 1988-03-23
Anticipated expiration: 2007-08-18
Also published as: GB8719469D0; IL79787A; GB2194913B; IL79787A0

Abstract

A gem holder for fixedly holding a plurality of gemstones 2 during notching by means of a laser comprises a plurality of relatively flat strips 14, each having a plurality of datum notches 18 cut across at least one of its longitudinal edges, and a base plate 10, at least the upper surface of which is provided with at least one set of substantially parallel slots in which the strips are insertable to be securely held therein. With the strips inserted into the slots of the base plate, the datum notches of the strips define a plurality of substantially parallel columns 20. The gem holder is used with notching apparatus comprising a laser device adapted to produce a focussed beam, and means for producing a controlled relative movement between the gem holder and the laser beam along at least two different axes. <IMAGE>

Description

SPECIFICATION A method and arrangement for notching gemstones The present invention relates to a method for notching gemstones, more particularly of diamonds, in preparation for cleaving. The invention also relates to a gemstone holder for fixedly holding a plurality of gemstones during notching operations. It further relates to an arrangement for notching such gemstones.

Rough diamonds, unless they happen to be exceptionally pure,, that is, free of flaws and blemishes, are split into smaller stones, in which process the flawed parts are eliminated and the stone given a basic shape in accordance with the final type and size of the brilliant as envisaged by the designer.

While preliminary cuts, such as the halving of the original octahedral crystals into two pyramidae ones, can be performed by sawing, the major steps of shaping prior to grinding, including the above-mentioned removal of flawed sections, is done by the so-cal led cleaving process which uses the quality of crystallized solids of splitting along definite planes.

Cleaving is induced by inserting a special tool-the cleavers knife-into a notch in the stone prepared for this purpose and applying a sharp blow to the back of this knife. If the notch is of the proper shape, if it is located at the proper spot and, most important of all, if it has the proper angular orientation with respect to some reference plane, for instance the plane of base of the octahedral crystal, the stone will indeed split exactly as desired.

Non-compliance with any of these conditions, especially the third one, will invariably result if not in a total shattered stone, then at least in a blank that is much smaller than that originally planned and, thus, in a cut stone of much lower value.

From the above it is quite obvious that the cleaves job is a most responsible one. Indeed, it takes at least one year to train a cleaver, and another year of practical experience before he is permitted to handle more valuable stones. Yet the most crucial and also the most time-consuming task of the cleaver is not the actual cleaving, using knife and mallet, but the preparation of the notches ("kerfs").

To this day, notching is carried out by mounting a sharp diamond fragment on one holder and the stone to be notched on another holder, gripping one holder in one hand and the other holder in the other hand, applying the respective ends of the holders against abutment pins on a special block for steadiness and leverage, and rubbing the sharp diamond fragment against the diamond to be cleaved, until a notch of the required depth is gouged out. An ink mark, previously applied by the designer of the stone (which is more often than not the cleaver himself) helps the cleaver to position the notch properly.

It is thus not surprising that, during a full working day, a first-rate cleaver can handle no more than about 100 stones. As cleavers, being highly skilled experts, demand and obtain salaries commensurate with their skills, it is obvious that cleaving as practised today constitutes a very expensive stage in the processing of diamonds, quite apart from the fact that good cleavers are hard to find.

It is one of the objects of the present invention to propose a remedy for the above-described state of affairs and to provide a method for notching gemstones that no longer requires the skill, knowhow and experience of a trained cleaver and can be taught to a person within hours; that, instead of the tedious, manual gouging method, uses a laser beam for notching and thus achieves the daily conventional notching output of the cleaver within half an hours, and results in more accurate cleaving than is possible with conventional notching and greatly reduces scrap and other cleavage losses.

This the invention achieves by providing a method for notching gemstones, comprising the steps of: providing a laser device producing a focusable beam; providing a gemstone holder adapted to fixedly hold a plurality of gem stones arranged in a plurality of substantially parallel columns defined by datum notches provided in members of said holder; providing means adapted to produce a relative movement between said holder and said laser beam along at least two different axes; marking the desired location, on each of said gemstones, of the notch, using a suitable marking substance; fixedly attaching the marked gemstones to said holder in such a way that, in each of said plurality of columns, said markings are substantially aligned with the datum notches of said members; switching on said laser beam;; activating said means to produce a relative movement between said gem holder and said beam along a first axis, whereby, in at least one notching run, said beam produces notches in the gemstones aligned with the datum notches of the first one of said columns; activating said means to produce a relative movement between said gem holder and said beam along a second axis, whereby, in an indexing run, said beam is positioned in front, and brought into alignment with the datum notches of, a second column; repeating said notching runs in alternation with said indexing runs until the gemstones in the entire plurality of columns are notched, and removing the notched gemstones from said gem holder.

The invention also provides a gem holder for fixedly holding a plurality of gemstones during the notching thereof, comprising: a plurality of relatively flat strips, each having a plurality of datum notches cut across at least one of- its longitudinal edges, and a base plate at least the upper surface of which is provided with at least one set of substantially parallel slots into which said strips are insertable to be securely held therein, wherein, with said strips inserted into the slots of said base plate, the datum notches of said strips define a plurality of substantially parallel columns.

There is further provided an arrangement for notching gemstones comprising: a gem holder for fixedly holding a plurality of gemstones during the notching thereof; a laser device adapted to produce a focused beam; means adapted to produce a relative movement between said gem holder and said laser beam along at least two different axes, and control means for controlling said laser beam and said means for producing said relative movement.

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood, With specific reference now to the figures in detail, it is stressed that the particuiars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention.In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

-In the drawings: Fig. 1 is a greatly magnified front elevation of a sawed and notched rough diamond; Fig. 2 represents the diamond of Fig. 1 as seen from the side of its base; Fig. 3 is a perspective view of the base plate of the gem holder according to the invention; Fig. 4 is a perspective view of the flat strip of the gem holder of Fig. 3; Fig. 5 is a top view of the fully assembled gem holder; Fig. 6 shows, in greatly enlarged perspective view of two rough diamonds as attached to the strip, prior to notching; Fig. 7 is a schematic view of a first embodiment of the notching arrangement according to the invention; Fig. 8 is a similar view of a second embodiment of the notching arrangement, and Fig. 9 shows a variant of the gem holder, in which the flat strips are parallel with respect to the longitudinal faces of the base plate.

Referring now to the drawings, there is seen in Fig. 1 the somewhat idealized shape of an already notched, rough diamond 2, the lower half of the originally octahedral shape having been sawed off prior to notching (dash-dotted portion), having a four-sided pyramid with a square base 4, seen to better advantage in the bottom view of Fig. 2. The notch 6 has a substantially V-like cross section and is of a depth of 1. 5-2 mm. Most important for clean, control led cleaving is the angle that the plane, normal to the plane of projection of Fig.

1 and passing through the bottom line of the notch 6, includes with the base 4 of the pyramidal stone. This angle must be 55" (to be accurate, 54"44', which is half the dihedral angle of the octahedron). The flaw to be removed, or the size and shape of the cut diamond.

The device which holds the gemstones during the notching operation and which automatically ensures adherence to the above angle condition will be described in the following.

The gem holder according to the invention, illustrated in Figs. 3-5, consists of a fairly massive rectangular base plate 10, typically about 200 mm long, 60 mm wide and 25 mm high, in which there are provided a plurality of relatively narrow slots 12 in a specific example, ten. These slots are slanting across the width of the base plate 10 at an angle of 35 , measured from the longitudinal plate edge in a counterclockwise direction. The slots 12 are strictly parallel, their width is, e. g., about 2 mm and the distance between slots is, e.g., 5 mm.

Into these slots 12 fit slidingly flat strips 14, typically 30 mm wide. Across the upper edges 16 of the strips 14 there are cut a plurality-about ten-equidistant datum notches 18, hereinafter, for short notches, which include with the major surfaces of the strip an angle of 55 , all in such a way that when the strips 14 are inserted into the slots (see Fig. 5), the notches 18 now aligned, wil 1 form equidistant columns or arrays 20 that include with the longitudinal faces of the base plate an angle of 90". The "pitch" P of the column 20 is, e.g., 8-9 mm. The first notch 18 of the first strip 14, as well as the last notch 18 of the last strip 14 (counting from left to right) will of course form ';columns" of a single notch only. The datum notches 18 are basically of the same shape and size as the cleaving notches 6 to be provided in the gemstones 2.

To define the position of the strips 14 in their slots 12 (in order to maintain their alignment), there is provided an abutment or stop rail 22 attached to one of the longitudinal faces of the base plate 10, and the end faces 24 of the strips 14 are bevelled (35").

It is advantageous to cut the notches 18, column by column, with the aid of the same laser beam arrangement (to be explained in detail further below) which is also used to notch the gemstones 2, and to consecutively number the strips (i. e., 1, 2, 3 n, see Fig. 4) so that each strip 14 will always be mounted in the same slot 12.

For notches located on the other side of the stone (see dash-dotted notch 6' in Fig. 2), strips 14, that is, slots 12, instead of slanting from lower left to upper right as in Fig. 3 must slant from lower right to upper left, in other words, must include with the longitudinal base-plate face an angle of 145", as measured in the counterclockwise sense. This calls for a second base plate, although a second, counterslanting set of slots 12 could be superposed on the first set. In any case, a new set of notches 18 has to be prepared, possibly on the second edge 16 of the strips 14.

The mounting of the gemstones 2 (of which, by way of example, three are shown in Fig. 5) is best understood from the enlarged perpsective view of Fig. 6, in which for clarity, only one strip 14 is shown.

The gemstones 2, which the designer (or cleaver) has provided with a chinese-ink marking 26, are atttached to the strip 14 by means of an adhesive tape 28 which is sticky on both of its surfaces, in such a manner that 1) the marking 26 is aligned with the notch 18, and 2) the upper edge 8 of the base 4 of the stone (see Fig. 2) is flush with the edge 16 of the strip 14. The importance of the latter will be explained further below.

Having ten strips 14, each with ten datum notches 18, the gem holder has thus a capacity of 100 diamonds. However, with smaller stones, or by using a base plate 10 in which the distance between the slots 12 is larger, it is possible to attach diamonds also to the other side of each strip 14, thus increasing capacity to 200.

It has already been mentioned, the time-consuming rubbing and gouging action of the diamond splinter has been replaced by the disintegrating action of a focusable laser beam. As the cutting action of the beam is limited to a very short distance above and below the actual focal point is crucial. If the latter is above the edge 8, no cutting action will take place.

If the focal point of the laser beam is too deep inside the gemstone, the latter is liable to crack. Hence the above-mentioned condition 2) concerning the attachment of the diamonds to the strips 14. If all the edges 16 of the strips 14 lie in a plane parallel to the base plate 10 (which they do, due to the manufacturing process of the gem holder) and if the upper edges 8 of all stones, big and small, are flush with these edges 16, then the focal point of the laser, set at a distance of, say, 1.5 mm below the plane containing all the edges 16, will be at the same depth relative to the edges 8 of all diamonds, big or small, and the notch 6 cut will be of identical depth in all stones.

The relative movement between beam and stones required to produce the notch can be obtained in several ways, to be discussed in conjunction with different embodiments of the notching arrangement provided by the invention.

A preferred embodiment of the arrangement is shown in Fig. 7 and comprises a laser 30 producing a beam 32 which, via a deflecting mirror 34, falls onto a lens system 36 that focuses it to a fi ne point 38 lying in a plane located slightly below the collective plane of the edges 16 of the strips 14 which, for sake of clarity, have been indicated only by the slanting, dashed lines 14 across the base plate 10. Equally indicated schematically are the "columns" 20 (see Fig. 5) representing the aligned datum notches 18 in the strip edges 16, in front of each of which notch there is attached a diamond to be notched (see Fig. 6).

To cover the entire gem holder, two different movements are required: one, in which, in succession, each stone in a particular column 20 has to be brought under the cutting beam for notching, a movement to be called "notching run", and another one in which, after completion of the notching run along one column 20, the next col umn 20 has to be aligned with the beam, ready for the next notching run. This movement shall be called "indexing run".

In the embodiment of Fig. 7, the laser beam 32 and its focal point 38 are stationary, and both the indexing run (double arrow A) and the notching run (double arrow B) are carried out by the base plate 10 which for this purpose is attached to an xy-table 40. The xdrive 42 and the y-drive 44 of the table 40 are connected to, and controlled by, a programmable microprocessor 46, which also controls the shutter 48 of the laser 30.

Due to the extreme hardness of the diamond, notching can not be performed in one single sweep of the laser beam. In fact, each notching run is repeated for up to twenty times to obtain a clean notch 6. This is of course programmed into the microprocessor 46, who is also cognizant of the fact that the notching runs are at first rather short (1, 2, 3 notches per column 20), grow larger towards the middle of the base plate 10 and taper off again towards the last columns. Thus no time is wasted on superfluous excursions, which is very important in view of the fact that each notching run along any particular column has to be repeated up to twenty times.

Many plants are today equipped with com puterized laser engravers, in which a scanner 50 (Fig. 8) consisting of two microprocessorcontrolled mirrors 52, 54 can deflect the focusable beam 32 to move for a limited distance in any direction or combination of directions, for instance, in order to engrave letters or numbers in hard materials.

Such a device can be used also in conjunction with the gem holder according to the invention by performing the notching runs, while the indexing runs are taken care of by the xdrive of a mechanical table.

A variant of the gem holder is shown in Fig.

9, where, as can be seen, the strips 14 are held in slots that are parallel with respect to the longitudinal extent of the base plate, and the "columns" 20 are slanted at an angle of 55". Such a holder can be used in conjunction with the scanner 50 in the arrangement of Fig.

8. Here, the slanter notching run (along columns 20 in Fig. 9) is realized by the computerized compound motion of the two mirrors 52, 54, while the indexing runs are again performed by the x-movement of the table 40.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A method for notching gemstones, comprising the steps of: providing a laser device producing a focusable beam; providing a gemstone holder adapted to fixedly hold a plurality of gem stones arranged in a plurality of substantially parallel columns defined by datum notches provided in members of said holder; providing means adapted to produce a relative movement between said holder and said laser beam along at least two different axes; marking the desired location, on each of said gemstones, of the notch, using a suitable marking substance; fixedly attaching the marked gemstones to said holder in such a way that, in each of said plurality of columns, said markings are substantially aligned with the datum notches of said members; switching on said laser beam;; activating said means to produce a relative movement between said gem holder and said beam along a first axis, whereby, in at least one notching run, said beam produces notches in the gemstones aligned with the datum notches of the first one of said columns; activating said means to produce a relative movement between said gem holder and said beam along a second axis, whereby, in an indexing run, said beam is positioned in front, and brought into alignment with the datum notches of, a second column; repeating said notching runs in alternation with said indexing runs until the gemstones in the entire plurality of columns are notched, and removing the notched gemstones from said gem holder.

2. A gem holder for fixedly holding a plurality of gemstones during the notching thereof, comprising: a plurality of relatively flat strips, each having a plurality of datum notches cut across at least one of its longitudinal edges, and a base plate at least the upper surface of which is provided with at least one set of substantially parallel slots into which said strips are insertable to be securely held therein, wherein, with said strips inserted into the slots of said base plate, the datum notches of said strips define a plurality of substantially parallel col umns.

3. The gem holder as claimed in claim 2, wherein said base plate is substantially rectangular, having longitudinal front and rear faces and transversal end faces.

4. The gem holder as claimed in claim 2, wherein said slots in said base plate include with the longitudinal faces thereof an angle substantially equal to 35", as measured in the counterclockwise sense.

5. The arrangement as claimed in claim 2, wherein said slots in said base plate include with the longitudinal faces thereof an angle substantially equal to 145", as measured in the counterclockwise sense.

6. The gem holder as claimed in claim 2, wherein said datum notches cut across the edges of said flat strips are equally spaced and, when said strips are inserted into said slots, include with the longitudinal faces of said base plate an angle substantially equal to 900.

7. The gem holder as claimed in claim 2, wherein said slots in said base plate are parallel to the longitudinal edges thereof and, when said flat strips are inserted into said slots, said datum notches include with said longitudinal faces an angle substantially equal to 55".

8. The gem holder as claimed in claim 2, further comprising at least one abutment rail attached to a longitudinal face of said base late in order to delimit and define the longitu dinal position of said flat strips inside said base-plate slots.

9. An arra#ngement for notching gemstones comprising: a gem holder for fixedly holding a plurality of gemstones during the notching thereof; a laser device adapted to produce a focused beam; means adapted to produce a relative movement between said gem holder and said laser beam along at least two different axes, and control means for controlling said laser beam and said means for producing said relative movement.

10. The arrangement as claimed in claim 9, wherein said control means is a programmable microprocessor.

11. The arrangement as claimed in claim 9, wherein said means to produce a relative movement comprises a mechanical table control lably drivable along at least one axis.

12. The arrangement as claimed in claim 9, wherein said means to produce a relative movement comprises a control lable, mirrorequipped scanner adapted to progressively deflect the beam produced by said laser device along at least one axis.

13. A method for notching gemstones substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

14. A gem holder substantially as hereinbefore described with reference to and as illustrated in Figure 5 of the accompanying drawings.

15. A gem holder substantially as hereinbefore described with reference to and as illustrated in Figure 9 of the accompanying drawings.

16. An arrangement for notching gemstones substantially as hereinbefore described with reference to and as illustrated in Figure 7 of the accompanying drawings.

17. An arrangement for notching gemstones substantially as hereinbefore described with reference to and as illustrated in Figure 8 of the accompanying drawings.