GB2231835A

GB2231835A - Cleaving gemstones

Info

Publication number: GB2231835A
Application number: GB9011303A
Authority: GB
Inventors: Marcel Biron
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-05-25
Filing date: 1990-05-21
Publication date: 1990-11-28
Also published as: AU5581790A; IL94434A0; GB8912050D0; CN1048000A; GB9011303D0

Abstract

Apparatus for cleaving gemstones (30) employs a vice (10) with jaw members (11, 12) biased apart with a spring. A liquid container (24) open at the top is disposed between the jaw members (11, 12). A microscope (20) permits examination of gemstones (30) on an illuminated carrier (14) in order to select a cleavage plane for each gemstone (30) which will at least partly eliminate a flaw. A cutting implement (19) receives a selected gemstone (30') with a cutting blade or blades (58, 59) orientated along the cleavage plane and clamps the gemstone (30'). The cutting implement (19) is raisable and lowerable and is partly immersed in the liquid in the container (24). A piston and cylinder unit (7) then closes the jaw members (11, 12) to squeeze the container (24) and sever the gemstone (30). The severed pieces of gemstone (30) then collect in the container (24). <IMAGE>

Description

A METHOD OF, AND APPARATUS FOR CLEAVING GEMSTONES The present invention relates to a method of, and apparatus for, cleaving or splitting gemstones particularly diamonds.

Natural rough diamonds often contain internal flaws such as inclusions or cracks which reduce their intrinsic value. It is known to eliminate such flaws by shearing or cleaving the diamonds along a cleavage plane containing the flaw or flaws. In conventional techniques, a small accurately-sited groove is made in the surface of the diamond with another diamond implement. A cutting tool is then placed in the groove and a sharp blow is given to the knife with a wooden mallet to split the diamond to eliminate or reduce the effect of the flaw. This operation is highly skilled and can take up to five minutes.

There is a need for an improved method of and apparatus for cleaving gemstones. More particularly, there is a need for a faster treatment.

In one aspect the invention provides a method of cleaving a gemstone, such as a diamond containing, a flaw along a plane to eliminate or mitigate the effect of the flaw, said method comprising subjecting a gemstone to visual examination with a microscope or other magnifying means to identify a flaw and a desired cleaving plane, positioning and clamping the gemstone in a cutting implement having at least one cutting blade such that the blade is orientated in registry with the cleaving plane, introducing at least part of the cutting implement and the gemstone into a flexible container preferably containing fluid and subjecting the container and the implement to force to effect splitting of the gemstone along the cleaving plane.

The invention also provides apparatus for carrying out the aforesaid method, the apparatus comprising a cutting implement with at least one cutting blade for clamping a gemstone with the blade orientated in registry with a desired cleaving plane, a microscope or other magnifying means for facilitating the identification of the desired cleaving plane and the positioning of the gemstone in the cutting implement, a flexible container, preferably containing fluid, for receiving at least part of the implement and the gemstone and force applying means for subjecting the container and the implement to force to split the gemstone along the cleaving plane.

The container may be a plastics envelope or bag.

Another form of container is a simple tube e.g. of p.v.c.

closed at one end and containing liquid, e.g. water. The splitting of the gemstone or diamond in the flexible fluid filled container is most beneficial and inter alia prevents dispersal and even loss of the smaller pieces of the gemstone after splitting occurs. The container can then act to collect and store the pieces resulting from severing several gemstones.

The cutting implement which also clamps or holds the gemstone can take the form of a conventional set of side cutters. Preferably, the cutting implement is mounted to means which can move the cutting implement into and out from the container.

The force applying means can take the form of a pair of relatively movable platens operated by the hydraulic or pneumatic force. The force applying means can be a vice with jaw members moved with a piston- and- cylinder unit.

It is desirable to bias the platens or jaw members apart with a spring opposing the closure force of the piston and cylinder unit. It is desirable to also provide a resilient force to the cutting implement to clamp the gemstone. In a simple form a spring or elastic band can be provided on the arms of the conventional side cutters. A piston and cylinder unit can be used to open the side cutters and this is useful when the gemstone is being positioned in the correct orientation.

In order to facilitate the visual inspection of diamonds with the microscope or magnifying means a transparent or translucent carrier such as a sheet of perspex is preferably provided on which the gemstones are laid. A light source can then illuminate the carrier from beneath.

The method and apparatus of the invention enable fast accurate splitting of gemstones and typically up to ten severing operations can be carried out per minute by a skilled operator.

The invention may be understood more readily and various other aspects and features of the invention may become apparent, from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing which is a schematic perspective representation of apparatus constructed in accordance with the invention.

As shown in the drawing, apparatus employs a vice 10 with relatively movable jaw members 11, 12. Conveniently, the jaw member 11 is fixed while the jaw member 12 is movable towards and away from the fixed jaw member 11.

The fixed jaw member 11 may be may be rigidly connected to a base support such as a bench or table top. The jaw member 12 is adapted to be moved towards the jaw member 11 with a piston- and- cylinder unit 7 which incorporates a spring which tends to hold the jaws 11,12 apart automatically unless the unit 7 is actuated. The jaw members 11, 12 have replaceable wooden blocks 8 on their working faces. A sensing device 52 is composed of an adjustable screw-threaded rod 53 on a block mounted to the jaw member 12 and a contact switch 54 on the jaw member 11. The switch 54 may provide a pneumatic or electric impulse when a sensor thereof is engaged with the rod 53. As the jaw members 11, 12 move together under the force of the unit 7 the sensing device 52 thus serves to provide a signal to halt the motion so that the spring then moves the jaw members apart.

A translucent carrier 14, conveniently in the form of a sheet of perspex, is adjustably mounted on the fixed jaw member 11. A piston-and-cylinder unit 25 is mounted on the jaw member 11 and has its piston rod coupled to the carrier 14. The unit 25 serves to displace the carrier 14 along the jaw member 11. The carrier 14 is provided with a slot 13 which receives a pin 45 on the jaw member 11 to guide the carrier 14 during its displacement.

A flexible tube 24 is closed at its lower end and open at the top. The tube 24 is, made from resilient rubber or plastics material, contains liquid, conveniently water, and is intended to be held between the jaw members 11, 12 for the purpose described hereinafter.

A light source 9, such as a halogen lamp is mounted in a poisition to illuminate the carrier 14 from below.

A microscope 20 with a stand 22 is supported on the base. The microscope 20 is disposed to view the carrier 14 and a knob 21 serves to adjust the height of the microscope 20. Separate controls (not shown) can adjust the focus of the microscope (20) and allow the microscope (20) to swing about an upstanding axis on the stand 22.

A support structure 26 is mounted to the jaw member 12 in association with an assembly 23 with a pair of parallel guide members 16 which is superimposed over the jaw members 11, 12. Between the guide members 16, there is a mounting block 17 which can be raised and lowered in relation to the jaw members 11, 12. A piston-andcylinder unit 18 is mounted on an upper wall 15 joining the guide members 16. The unit 18 has a piston rod extending through the wall 15 and connected to the block 17. The unit 18 serves to raise and lower the block 17 through a pre- determined distance. The assembly 23 is adjustably mounted to the structure 26 and a screwthreaded mechanism 33 on the structure 26 connects to the assembly 23. A rotatable knob 28 serves to operate the mechanism 33 to adjust the height of the assembly 23.

The unit 18 thus serves to move the block 17 rapidly between upper and lower positions relative to the guide member 16 and the mechanism 33, operated by turning the knob 28, enables the operator to adjust the height of the overall assembly 23.

The block 17 serves to carry one arm 48 of a cutting implement 19 here in the form of a pair of side cutters.

The arms 48, 49 of the implement 19 are biased with a spring 42, such as an elastic band, to hold the cutting blades 58, 59 together. Another piston -and-cylinder unit 50 usable to open the blades 58,59 has a piston rod which is connected with a coupling fork 46 to the other arm 49 of the cutting implement 19. The cylinder of the unit 50 is mounted with a bracket 47 on the jaw member 12. The fork 46 acts as a lost-motion linkage or coupling to permit the blades 58, 59 to close solely under the force of the spring 42.

During use, diamonds 30 are placed onto the carrier 14 which is illuminated by the light source 9 and the carrier 14 can be adjusted with the unit 25. An operator can then inspect the diamonds with the microscope 20. A skilled operator can identify flaws in the diamonds and decide how they are to be cut to eliminate such flaws. A selected diamond 30' is then picked up and transferred between the blades 58, 59 of the implement 19 which are opened by operating the unit 50. To achieve this a small rod or dowel (not shown) having a deposit of contact adhesive at one end or vacuum tweezers can be used. The piston and cylinder unit 50 which operates on the implement 19 is advantageous in freeing the operator's hands from the task of opening the blades 58, 59 to accept the diamond 30'. The carrier 14 is moved away with the unit 25 when the diamond 30' is being transferred.The selected diamond 30' is carefully placed into the correct orientation relative to the cutting edges of the blades 58, 59 of the implement 19 still whilst viewed by the microscope 20 and the unit 50 is de-actuated to release the blades 58,59. Once positioned the blades 58, 59 tend to hold the diamond 30' by virtue of the resilient biasing of the spring 42. The implement 19 represents both a means for clamping the selected diamond 30 and cutting means with at least one blade or the like for severing the diamond and can be replaced by analogous equipment again raised and lowered with the block 17. The unit 18 is next operated to extend and cause the block 17 supporting the implement 19 to be lowered to bring the blades 58, 59 of the implement 19 with the diamond 30' into the upper portion of the tube 21.Once the diamond 30' held by the blades 58,59 of the implement 19 is in place the vice jaw member 12 is moved towards the jaw member 11 by operating the unit 17 to squeeze the tube 21 and press on the blades 58, 59 of the implement 19 in the tube 24 to sever the diamond 30'.

The force is removed when the sensing device 52 is activated to allow the spring to move the jaw member 12 away from the jaw member 11. The tube 21 and the liquid therein provide a damping medium and prevents the pieces of cut diamond from being scattered and lost. The block 17 is then raised with the unit 18 for the next diamond and the carrier 14 is moved back with the unit 25. The sequence can then be repeated a number of times before the tube 24 is removed to recover the cut diamonds. In case of need the assembly 23 can be adjusted with the knob 28 from time to time.

In general, the selected diamond 30' and the blades 58, 59 of the cutting implement 19 need only be immersed to a depth of around 2cm and the vice jaw member 12 need only move by a relatively small amount, say up to 6mm, to achieve the necessary pressure on the blades 58,59. The pressure produced by the vice 10 can be varied and controlled to suit the size of the diamond to be cut and 3 a range of 2000-10,000 lbs per square inch (13788 x 10 4 6894 x 10 Pa) is envisaged.

The various piston-and-cylinder units 25, 7, 50, 18 and the vacuum tweezers can be controlled and/or operated by compressed air and conveniently the sequence of operations is controlled by pneumatic valves.

Conveniently, the apparatus is mounted on a portable trolley with a compressor and foot-controls for operating the units 7, 18 50.

Safety guards or screens (not shown) can be employed to partly enclose the working site when severing takes place.

Claims

CLAIMS:

1 A method of cleaving a gemstone, such as a diamond, containing a flaw along a plane to eliminate or mitigate the effect of the flaw; said method comprising subjecting a gemstone to visual examination with a microscope or other magnifying means to identify a flaw and a desired cleaving plane, positioning and clamping the gemstone in a cutting implement having at least one cutting blade such that the blade is orientated in registry with the cleaving plane, introducing at least part of the cutting implement and the gemstone into a flexible container and subjecting the container and the implement to force to effect splitting of the gemstone along the cleaving plane.

2 A method according to claim 1 wherein the cutting implement is raised and lowered in relation to the container and the force is applied to the exterior of the container.

3 A method according to claim 1 or 2, wherein a plurality of gemstones are placed on an illuminated carrier for the visual examination and a selected gemstone is then transferred to the cutting implement for clamping.

4 A method according to any one of claims 1 to 3, wherein the said at least one cutting blade of the cutting implement is biased with a spring to clamp the gemstone and force is applied to the implement to cause the blade to adopt an unclamped position to accept the gemstone.

5 A method according to any one of claims 1 to 4 and further comprising controlling the force applied to the container at the implement with adjustable means.

6 A method according to any one of claims 1 to 5, wherein the force is applied to the container and the implement by squeezing the container between relatively moving platens.

7 A method substantially as described with reference to, and as illustrated in the accompanying drawing.

8 An apparatus for cleaving a gemstone, such as a diamond, containing a flaw along a plane to eliminate or mitigate the effect of the flaw; said apparatus comprising a cutting implement with at least one cutting blade for clamping a gemstone with the blade orientated in registry with a desired cleaving plane, a microscope or other magnifying means for facilitating the identification of the desired cleaving plane and the positioning of the gemstone in relation to the cutting implement, a flexible container for receiving at least part of the implement and the clamped gemstone and means for applying force to the container and the implement to split the gemstone along the cleaving plane.

9 An apparatus according to claim 8 wherein the flexible container contains liquid.

10 An apparatus according to claim 8 or 9, wherein the container is a tube closed at one end.

11 An apparatus according to claim 8, 9 or 10 wherein the force applying means includes relatively movable platens for squeezing the container therebetween.

12 An apparatus according to claim 8, 9 or 10 wherein the force applying means comprises a vice with relatively movable jaw members.

13 An apparatus according to claim 11 or 12 wherein the platens or jaw members are moved relatively by a pistonand-cylinder-unit.

14 An apparatus according to claim 13 and further comprising adjustable means for sensing the relative position of the platens or jaw members and for controlling the operation of the piston and cylinder unit.

15 An apparatus according to any one of claims 11 to 14 and further comprising means for biasing the platens or jaw members apart.

16 An apparatus according to any one of claims 8 to 15 and further comprising a transparent or translucent carrier for receiving gemstones for visual inspection with the microscope or magnifying means and a light source for illuminating the carrier.

17 An apparatus according to claim 16 when appended to any one of claims 11 to 15 wherein the carrier is adjustably mounted to one of the platens or jaw members.

18 An apparatus according to any one of claims 8 to 17 and further comprising means for mounting the cutting implement for raising and lowering in relation to the container.

19 An apparatus according to claim 18 wherein the cutting implement has a pair of pivotable cutting blades joined to arms and spring means biases the arms together to clamp the blades together.

20 An apparatus according to claim 19 wherein there is further provided a piston-and-cylinder unit for moving the blades of the cutting implement apart.

21 An apparatus according to any one of claims 18 to 20 wherein said mounting means including a piston-andcylinder unit.

22 An apparatus according to any one of claims 18 to 21 wherein the mounting means is an assembly itself adjustable in height in relation to a support structure.

23. Apparatus substantially as described with reference to, and as illustrated in, the accompanying drawing.