NZ548598A - Decorative stone - Google Patents

Abstract

A method of applying an inlaid design to the curved surface of a stone including: providing a stone with at least one recess; and in situ casting of the material of the inlaid design, where the at least one recess includes a means for retaining the material when cast. A decorative stone item with an in situ cast inlay in a curved surface where the recess includes a means for retaining the cast inlaid material is also disclosed.

Description

5485 9 8 Patents Form No. 5 *10052164495* Patents Act 1953 COMPLETE SPECIFICATION DECORATIVE STONE I, Hamish Simon Rae, of 32b Oram Avenue, New Brighton, Christchurch, and a New Zealand citizen, 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 the following statement: 548598 C2324.002 II DECORATIVE STONE TECHNICAL FIELD The invention relates to a method of preparing a decorative stone item with an inlaid surface. In particular, the invention relates to stone jewellery with an inlaid design of metal.

BACKGROUND ART Stone can be transformed into a decorative item by applying a design to its surface. Designs may be applied as a surface coating, etching or inlay. When applying a design as an 15 inlay a number of problems arise.

Firstly, creating a recess for the inlay that is both deep enough to receive the pre-formed inlay and exact enough to reproduce the intended design is problematic. This problem is 20 particularly acute where the design is complex, requiring several recesses of predetermined shape and orientation relative to each other to be made.

Secondly, when applying an inlay to a curved surface it is 25 difficult to provide a recess that corresponds to the desired two dimensional surface design.

Thirdly, it is necessary to affix the pre-formed inlay in the recess. Known methods may use resins or adhesives in 30 combination with the pre-formed inlay. Certain inlay materials, particularly precious metals are resistant to adhesion, and are therefore difficult to securely affix in the recess. 2 C2324.002 II In addition to these problems the inlay must be pre-formed. Where the material of the inlay is a metal the pre-forming may be by electro-forming, casting or manual forming. Electro-5 forming is limited in the detail of the shapes that can be formed. Casting requires the creation of a sacrificial model. Manual forming is costly and time consuming.

Due to the limitations of the known methods, applying an 10 inlaid design to a stone surface, especially if it is an intricate or complex design, is very costly and time consuming.

It is an object of the invention to provide an improved method 15 of preparing a decorative stone item with an inlaid surface or at least to provide a useful choice.

DISCLOSURE OF INVENTION In a first aspect the invention provides a method of applying an inlaid design to the curved surface of a stone including the step: • Providing a stone with at least one recess; and • In situ casting of the material of the inlaid design, where the at least one recess includes a means for retaining the material when cast.

Preferably, the method of applying an inlaid design includes the step: 3 Intellectual Property Office ot N.2. 2 9 NOV 2007 RECEIVED C2324.002 II • Filling at least one recess in the surface of the stone with a fluidizable substance.

Preferably, the means for retaining is provided by means selected from the group consisting of: the walls of the recess being undercut; holes at an angle to the surface of the walls or floor of the recess.

Preferably, the in situ casting includes the step of: • Connecting the filling of a recess to a tree of a fluidizable substance.

Preferably, the inlaid design includes a plurality of components and the in situ casting includes the step of: • Inter-connecting multiple recesses in the surface of the stone with a bridge of fluidizable substance.

Preferably, the providing a stone with at least one recess is by a method including the step: • Blasting with a blasting medium through a stencil.

More preferably, the stencil is formed by a method including the steps: • Covering a surface of the stone with a masking material; and • Cutting an inlay design in the masking material. 4 C2324.002 II Preferably, the stone is selected from the group consisting of stones that can be maintained at temperatures above 750 °C for greater than eight hours without loss of structural integrity. More preferably, the stone is selected from the group 5 consisting of: greywacke.

Preferably, the material of the inlaid design is a metal. More preferably, the material is a precious metal. Most preferably, the material is a precious metal selected from the 10 group consisting of: gold, silver.

Preferably, the stone is a pebble.

Preferably, the in situ casting is by a modified form of 15 investment casting.

Preferably, the investment casting excludes quenching of the heated mould.

In a second aspect the invention provides a decorative stone item with an insitu cast inlay in a curved surface where the recess accommodating the inlay includes a means for retaining the cast inlay material.

Preferably, the means for retaining is provided by means selected from the group consisting of: the walls of the recess being undercut; holes at an angle to the surface of the walls or floor of the recess.

Preferably, the stone is selected from the group consisting of stones that can be maintained at temperatures above 750 °C for 2 s NOV 2007 C2324.002 II greater than eight hours without loss of structural integrity. More preferably, the stone is selected from the group consisting of: greywacke.

Preferably, the stone is a pebble.

Preferably, the material of the inlay is a metal. More preferably, the material is a precious metal. Most preferably, the material is a precious metal selected from the 10 group consisting of: gold, silver.

In the context of this description it will be understood that the following terms and phrases have the meanings provided: "fluidizable substance" means a substance that will be transformed, e.g. by combustion, to one or more fluid components on heating without leaving a residue, e.g. wax. "in situ casting" means shape molten material in a mould that 20 retains the cast shape. "investment casting" means a technique for making small, accurate castings using a plaster mould formed around a pattern of fluidizable substance which is removed by heating. "means for retaining" means a correspondence between the shape of the recess and the shape of the cast inlay that causes the inlay to be retained in the recess once the cast inlay has solidified. "ornament" means a decorative item, including jewellery. ®34U6aoj f C2324.002 II "recess" means a space set back in the surface of a stone having an open face, walls and a floor. "stencil" means a thin sheet of material with a design cut out 5 of it used to form the cut design in the surface below.

In the context of this description it will be understood that the open face of the recess corresponds to the design of the inlay or one component of that design.

Exemplary embodiments of the invention will now be described in detail with reference to the Figures of the accompanying drawings pages.

BRIEF DESCRIPTION OF FIGURES Figure 1 a photograph of a stencil (enlarged, right) with the design to be inlaid cut out of the masking material.

Figure 2 a photograph of multiple recesses formed by blasting with a blasting medium through the stencil of Figure 1 and undercut to provide means for retaining (enlarged image, arrow) accompanied by schematic representations of the cross-section of a recess before (left) and after (right) 25 undercutting.

Figure 3 a photograph of a decorative stone with an in situ cast inlay of a multi-component design where the recesses accommodating the inlay include a means for retaining the cast 30 inlay material (enlarged, left). 7 C2324.002 II DETAILED DESCRIPTION A decorative stone item with an inlaid surface is prepared by a combination of providing a recess including a means for 5 retaining the cast inlay material and in situ casting of the inlay material.

The method is particularly applicable when using stone that does not undergo degradation, i.e. cracking or fragmenting, 10 when subjected to high temperature for prolonged periods of time, and inlay material that is resistant to adhesion.

The method is most advantageously applied to the manufacture of small decorative stone items such as jewellery, including 15 pendants, cufflinks, etc., where the surface of the stone is curved.

EXAMPLE The first step of preparing a decorative stone item with an inlaid surface is to apply a stencil to the surface of the stone. Typically the stone will be a naturally occurring greywacke pebble.

An image corresponding to the design of the inlaid surface is cut out of masking material to provide the stencil ' (Figure 1). Although this can be done by cutting the film prior to the application to the surface of the stone it is preferably done afterward. This avoids the distortion of the image when the 30 pre-cut stencil is applied to the curved surface of a stone.

A suitable material for use as a masking material is butynol membrane. The membrane can be affixed to the stone surface Intellectual Property Office of M.z. 2 9 NOV 2007 R EC EIVE[ C2324.002 II using contact adhesive. The design to be inlaid can be cut out of the membrane using a scalpel. However, the use of a laser cutting device provides the additional advantage of the cut portion of the masking material being vapourised. Thus 5 the painstaking removal by hand of the cut out sections of intricate, multi-component designs, can be avoided.

Provided that the masking material of the stencil is firmly adhered to the surface of the stone it is then possible to blast the surface of the stone and create a recess corresponding to the design of the inlaid surface. When working greywacke and using butynol membrane, blasting may be done with a blasting medium such as garnet sand. Other combinations of stone, masking material, and blasting medium 15 may be used.

The blasting may be done at an angle so as to provide a recess with undercut walls. Firm adherence of the masking film to the surface of the stone allows for complex and detailed 20 designs. Alternatively a recess may be provided and the undercut walls formed separately using diamond burrs or drills (Figure 2, arrow).

Where undercut walls are not desirable, or simply as an 25 alternative means of retaining the cast inlay material in the recess, holes may be drilled at an angle into the walls or floor of the recess. These holes allow for the formation of toggles which serve to retain the cast inlay material in the recess.

It will be appreciated that the requirement for undercut walls or the drilling of holes may be unnecessary if the means for retaining the cast inlay material in the recess is provided by 9 C2324.002 II the cast inlay material corresponding to an element of a design that covers a substantial portion of a convex surface. In this case the shape of the recess as a whole provides the means for retaining.

Following removal of the stencil a stone with at least one recess in the surface corresponding in shape to the design of the inlay is provided (Figure 2). Once undercut, the recesses can then be filled with wax and inlayed with metal using a 10 modified investment casting process. In the modified investment casting process the stone is passed through the investment casting process.

In this modified investment casting process the stone is 15 required to maintain its integrity at temperatures above 7 50 °C for upwards of eight hours. Greywacke is a selection of stone that is both soft enough for recesses to be formed in the surface of the stone by blasting and robust enough to maintain its integrity in the modified investment casting 20 process.

Where the design comprises multiple components and multiple recesses are used, the filled recesses are inter-connected with a bridge wax. A limb of wax is then used to connect the 25 inter-connected filled recesses to a tree of fluidizable substance.

The tree bearing stones is then processed by investment casting. Although individual stones could be processed by 30 investment casting without the requirement for a tree, the use of a tree allows for in situ casting of the inlay material in multiple stones.

C2324.002 II Investment casting is a process by which the fluidizable substance is replaced by molten inlay material. In the modified investment casting this is achieved by encasing the tree bearing stones and then heating the encased tree so that 5 the fluidizable substance is vaporized, combusted or melted so that it exits the passages and recesses defined by the tree and stones without leaving a residue.

Molten inlay material, such as a precious metal, is then 10 poured into the casing to fill the recesses of the stones. Care should be taken at this stage. Rapidly cooling the casing, e.g. by quenching, may cause the stones to fracture, particularly in the region ■ of the undercut walls of the recesses.

Allowing the casing to cool gradually and then removing it gently, e.g. by water blasting, will prevent damage to the stone if this is a problem and provide a tree bearing stones where the fluidizable substance has been replaced by the inlay 20 material e.g. precious metal.

The stone bearing tree is effectively pruned to provide 1 individual stones with in situ cast inlay material. The inlay is sanded to provide a flush surface, and polished to provide 25 the desired finish. This finishing is also used to remove any raised bridging sections used to inter-connect the components of a complex design. A decorative stone is provided (Figure 3) .

At this stage further detail may be added to the design of the inlay by engraving the inlay material. The stone might also be oiled or dyed to produce further desired effects. 11 C2324.002 II Although the invention has been described by way of exemplary embodiments it should be appreciated that variations and modifications may be made with out departing from the scope of the invention. Furthermore where known equivalents exist to 5 specific features, such equivalents are incorporated as if specifically referred to in this specification.

INDUSTRIAL APPLICABILITY The invention provides an improved method for the production of decorative stone items with an inlaid surface. Multiples of the decorative stone items may be prepared by the method of the invention. 12 C2324.002 II

Claims (5)

1) A method of applying an inlaid design to the curved surface of a stone including the step: • Providing a stone with at least one recess; and • In situ casting of the material of the inlaid design, where the at least one recess includes a means for retaining the material when cast.

2} The method according to claim 1 including the step: 15 • Filling at least one recess in the surface of the stone with a fluidizable substance.

3) The method according to claim 1 or 2 where the means 20 for retaining is provided by means selected from the group consisting of: the walls of the recess being undercut; holes at an angle to the surface of the walls or floor of the recess. 25 4) The method according to any one of claims 1 to 3 where the in situ casting includes the step of:

• Connecting the filling of a recess to a tree of a fluidizable substance. 30

5) The method according to any one of claims 1 to 4 where the inlaid design includes a plurality of components and the in situ casting includes the step of: 13 intellectual Property Office ot Ni.z. 2 9 f*0V 2007 R F f! P I \/ c n C2324.002 II • Inter-connecting multiple recesses in the surface of the stone with a bridge of fluidizable substance. The method according to any one of claims 1 to 5 where the providing a stone with at least one recess is by a method including the step: • Blasting with a blasting medium through a stencil. The method according to claim 6 where the stencil is formed by a method including the steps: • Covering a surface of the stone with a masking material; and • Cutting an inlay design in the masking material. The method according to any one of claims 1 to 7 where the stone is selected from the group consisting of stones that can be maintained at temperatures above 750 °C for greater than eight hours without loss of structural integrity. The method according to claim 8 where the stone is selected from the group consisting of: greywacke. The method according to any one of claims 1 to 9 where the material of the inlaid design is a metal. The method according to claim 10 where the material is a precious metal. 14 u 3 AUG 2006 RECfif Vlii C2324.002 II The method according to claim 11 where the material is a precious metal selected from the group consisting of: gold, silver. The method according to any one of claims 1 to 12 where the stone is a pebble. The" method according to any one of claims 1 to 13 where the in situ casting is by a modified form of investment casting. The method according to claim 14 where the investment casting excludes quenching of the heated mould. A decorative stone item with an in situ cast inlay in a curved surface where the recess accommodating the inlay includes a means for retaining the cast inlay material. The decorative stone item according to claim 16 where the means for retaining is provided by means selected from the group consisting of: the walls of the recess being undercut; holes at an angle to the surface of the walls or floor of the recess. The decorative stone item according to claim 16 or 17 where the stone is selected from the group consisting of stones that can be maintained at temperatures above 750 °C for greater than eight hours without loss of structural integrity. Office of N.Z. 2 9 NOV 2007 15 C2324.002 II The decorative stone item according to any one of claims 16 to 18 where the stone is selected from the group consisting of: greywacke. The decorative stone item according to any one of claims 16 to 19 where the stone is a pebble. The decorative stone item according to any one of claims 16 to 20 where the material is a metal. The decorative stone item according to any one of claims 16 to 21 where the material is a precious metal. The decorative stone item according to any one of claims 16 to 22 where the material is a precious metal selected from the group consisting of: gold, silver. By his attorneys ?'■' LOwndes Associates Intellectual Property Office of n.Z. 29 NOV 2007 RECEIVED 16