Abstract:
A method of forming an article such as a jewellery ring or bangle comprising: providing a first substantially annular-sectioned element and a second substantially annular-sectioned element, an outer diameter of the first element being less than an inner diameter of the second element; forming a circumferential groove in one of the first and second elements by a process of rolling; positioning the first and second elements together with the second element positioned circumferentially around the first element; and expanding the first element such that the circumferential groove in the one element receives therein the other of the said elements.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to articles of jewellery and to a method of formation thereof. In particular but not exclusively the invention relates to articles of jewellery comprising two or more precious metals, further particularly but not exclusively two or more rings or bands of precious metal joined to form a single ring or band. 
       BACKGROUND 
       [0002]    It is known to form a ring or the like from two or more precious metals each in the form of a circular ring element or band to be worn around a finger. The two ring elements may be stacked on top of one another in a side by side arrangement along a common axis, and joined together by soldering or brazing. Alternatively the ring elements may be joined such that one ring element (an outer ring element) surrounds the other ring element (an inner or basal ring element), i.e. one is positioned radially outward of the other. 
         [0003]    In the latter case, the ring is typically fabricated by forming a groove in a radially outer surface of the basal ring element by machining on a lathe. The outer ring element is machined to the required axial length and diameter, and is then placed around the basal ring element. The basal ring element is then expanded by stretching to increase its diameter to the final required finger size. The basal ring element is expanded sufficiently to trap the outer ring element in the groove formed in the basal ring element, but care must be taken not to cause fracture of the ring element by expanding by too great an amount. 
         [0004]    Bands of larger diameter to be worn around a wrist, such as bangles, comprising two different precious metals may be made in a similar manner to the rings described above. 
         [0005]    It is an aim of the present invention to address disadvantages associated with the prior art. 
       SUMMARY OF THE INVENTION 
       [0006]    Embodiments of the invention may be understood with reference to the appended claims. 
         [0007]    Aspects of the present invention provide an article and a method. 
         [0008]    In one aspect of the invention for which protection is sought there is provided a method of forming an article comprising:
       providing a first substantially annular-sectioned element and a second substantially annular-sectioned element, an outer diameter of the first element being less than an inner diameter of the second element;   forming a circumferential groove in one of the first and second elements by a process of rolling;   positioning the first and second elements together with the second element positioned circumferentially around the first element; and   expanding the first element such that the circumferential groove in the one element receives therein the other of the said elements.       
 
         [0013]    By annular-sectioned is meant that the element has a transverse cross-section substantially in the form of an annulus. By transverse is meant substantially perpendicular to a longitudinal axis of the article, which may for example be a longitudinal axis of symmetry, for example in the case of an element in the form of a tube or toroid. One or more of the annular-sectioned elements may by toroidal in shape. A longitudinal cross-section through a portion of an element may therefore be substantially circular. By longitudinal cross-section is meant a cross-section as viewed substantially perpendicular to the longitudinal axis. Alternatively a longitudinal cross-section of a portion of one or more elements may by substantially lenticular, substantially truncated lenticular, substantially elliptical, substantially truncated elliptical, substantially square, substantially rectangular or any other suitable shape. An inner or outer radial surface of the article may be arranged to be court. That is, an inner or outer radial surface of the article may be arranged to be curved in an axial direction, for example about a generally circular axis in a transverse plane. In the case of an article in the form or a ring for wearing on a finger, forming an inner radial surface of the ring to be court has the advantage of improving an ease with which the article may be slid onto the finger in some embodiments. 
         [0014]    The substantially annular-sectioned element may comprise a frustrated cone. Optionally, the substantially annular-sectioned element is in the form of a substantially frusto-conical element. 
         [0015]    By rolling is meant that pressure is applied to a surface of the element by a roller, the pressure being applied by relative rolling motion between the element and the roller. The pressure may be applied in a direction generally substantially perpendicular to the longitudinal axis and/or normal to the surface of the element. In some embodiments the element itself may be rotated; in some alternative embodiments the roller may be rotated. 
         [0016]    It is to be understood that forming the groove in one of the annular-sectioned elements by rolling has the advantage that loss of material due to cutting does not occur. Furthermore, the cost of providing a cutting tool and replacing worn cutting tools may be eliminated by use of a rolling operation. 
         [0017]    Furthermore, in some embodiments a depth of the groove may be controlled by rolling to within a greater tolerance than other methods of forming a groove, such as by cutting, for example using a lathe. In some embodiments, a groove of more shallow and more precise depth may be formed in one of the annular-sectioned elements, allowing the other annular-sectioned element to be of reduced thickness relative to known structures. In some embodiments, the annular-sectioned element to be received in the groove of the other element may be formed by rolling of an annular-sectioned element between rollers. The rollers may be disposed to grip radially inner and outer surfaces at a given circumferential location. The element may be rolled to form an annular-sectioned element of relatively low thickness. This feature has the advantage that substantially annular-sectioned elements may be formed having a thickness that is lower than that of substantially annular-sectioned elements formed using alternative techniques for thinning an annular-sectioned element such as cutting of a tube, for example by turning on a lathe, as in known structures. 
         [0018]    In known methods of fabricating double ring structures, the groove is cut in a first ring element to be deeper than is required in methods according to the present invention, and a second ring element of greater thickness employed due to limitations in the minimum thickness of ring element that may be produced by cutting. A mismatch in outer diameters of the first and second ring elements following expansion of the inner ring element to trap the outer ring element inevitably results, requiring a post finishing operation in which trimming of the outer surface of the ring article takes place to substantially eliminate a step in outer diameter of the article due to the difference in outer diameters of the elements. This further finishing operation results in increased cost of manufacture and wastage of material due to trimming. Furthermore, since a radial thickness of the second ring element is relative large this can result in increased cost of manufacture. 
         [0019]    Some embodiments of the present invention have the advantage that double ring structures having one or more substantially annular-sectioned elements inset in another substantially annular-sectioned element may be produced with the inset element or elements being of lower thickness that in known structures; this enables a reduction in the amount of material required to form the one or more inset elements. Furthermore, a requirement for post-finishing cutting of the annular-sectioned elements may be reduced or substantially eliminated in some embodiments. 
         [0020]    Some embodiments of the present invention permit an article comprising at least two substantially annular-sectioned elements to be formed with one substantially annular-sectioned element inset in the other without any requirement for cutting of the substantially annular-sectioned elements such as turning on a lathe or the like. In some embodiments, substantially the only cutting operation involved in fabricating the article may be cutting of substantially flat discs from a sheet of material and forming an aperture in the discs, to form washer-shaped elements which are subsequently coned to form tube or tube-like elements of substantially annular-section. It is to be understood that, subsequently, cutting of decorative markings may be made in the article if required. However, cutting is not necessarily required in order to provide an article according to an embodiment of the invention for the reasons stated above. 
         [0021]    It is to be understood that the annular-sectioned article may be a jewellery item such as a band or ring, or bangle or the like. 
         [0022]    The groove may be formed to any required depth. In some embodiments the groove is formed to a depth of from around 0.1 mm to around 0.5 mm. Smaller depths may be useful in some embodiments, such as 0.05 mm. Similarly, in some embodiments greater depths may be useful such as 0.7 mm, 1.0 mm or any other required depth. In some embodiments, in order to form a jewellery ring article to be worn around a finger, an inner diameter of the first element may be around 9 mm and an outer diameter may be around 16 mm or less. An axial length of the element may be around 6 mm, optionally around 7 mm, 8 mm or any desired length. 
         [0023]    It is to be understood that the inner diameter of the first element may be arranged to be smaller than a smallest required inner diameter of the finished article. Accordingly, the first element may be expanded to the required diameter. Since forming a groove in an annular-sectioned element such as the first element by rolling may result in expansion of the diameter of the annular-sectioned element, in some embodiments the first annular-sectioned element may be arranged to have the required inner diameter following rolling to form the groove. Alternatively, in some embodiments the diameter of the first annular-sectioned element may be expanded by rolling in which a groove is not formed, for example by rolling between substantially flat roller elements not having a raised portion to form a groove. Subsequently, a rolling operation may be performed to form a groove in the first annular-sectioned element such that a final inner diameter of the first element following rolling to form the groove is substantially equal to the required inner diameter of the final article. 
         [0024]    In some embodiments, forming a groove having a depth of substantially 0.5 mm in an annular-sectioned element having an inner diameter of 9 mm results in expansion of the inner diameter to substantially 10 mm. 
         [0025]    In some embodiments, in order to form a jewellery bangle article to be worn around a wrist, an inner diameter of the first element may be around  16  mm and an outer diameter may be around 22 mm or less. An axial length of the element may be around 6 mm, optionally around 7 mm, 8 mm or any desired length. 
         [0026]    The method may comprise forming the circumferential groove in a radially outer surface of the first substantially annular-sectioned element. 
         [0027]    Alternatively, the method may comprise forming the circumferential groove in a radially inner surface of the second annular-sectioned element. 
         [0028]    In some embodiments a circumferential groove may be formed in an inner radial surface and an outer radial surface of the first substantially annular-sectioned element. The second element may be received in the groove formed in the outer radial surface when the first element is expanded. A third substantially annular-sectioned element may be received in the groove formed in the inner radial surface of the first element when a diameter of the third element is expanded. 
         [0029]    In some alternative embodiments a circumferential groove may be formed in an inner radial surface and an outer radial surface of the second substantially annular-sectioned element. The first element may be received in the groove formed in the inner radial surface when the first element is expanded. A third substantially annular-sectioned element may be received in the groove formed in the outer radial surface of the second element when a diameter of the second element, optionally together with the first element, is expanded. 
         [0030]    It is to be understood that in some embodiments one annular-sectioned element may be said to become trapped in the groove formed in the other annular-sectioned element when the circumferential groove in the one element receives therein the other of the said elements. By the term trap is meant that the annular-sectioned element is prevented from moving beyond a sidewall of the groove by interference between the first and second annular-sectioned elements. 
         [0031]    In the case that the groove is formed at a location spaced apart from opposite edges of one of the substantially annular-sectioned elements, referred to herein as a double sided groove, separation of the first and second substantially annular-sectioned elements by axial translation relative to one another may be substantially prevented by interference. In the case that the groove is formed at one axial end of the element, having one side that is open, the groove may be referred to as a single sided groove. A stepped edge to the element may thereby be provided. Movement of the substantially annular-sectioned elements relative to one another may be substantially prevented in one axial direction by interference between the annular-sectioned element received in the groove and the sidewall of the groove. 
         [0032]    However, in such embodiments movement of the second element in the opposite direction, away from the first element, may be permitted in some embodiments unless the second element is expanded sufficiently to prevent separation of the first and second elements by a friction fit or other means. It is to be understood that the first or second elements may be provided with formations such as ridges, bumps or the like in or over a surface in contact with the other element, to provide increased grip between the respective elements to resist separation. Other arrangements for resisting separation may be useful in some embodiments such as diffusion bonding, a mechanical fixing element such as a screw element, an intermediate joining medium such as a solder or brazing material, or any other suitable arrangement. 
         [0033]    Optionally, forming the circumferential groove in an element by rolling comprises constraining axial expansion of the element in a longitudinal direction during rolling. 
         [0034]    It is to be understood that plastic deformation of the annular-sectioned element typically occurs during rolling of the annular-sectioned element to form the groove. By constraining axial expansion parallel to the longitudinal axis of the annular-sectioned element, an outer diameter of the annular-sectioned element may tend to increase in some embodiments as a depth of the groove formed in the annular-sectioned element increases due to plastic deformation of the element and flow of material from under a roller means or the like used to form the groove. This feature has the advantage that in some embodiments a starting thickness of the annular element may be reduced for a given required groove depth relative to embodiments in which lateral expansion is not constrained during rolling. This in turn allows a reduction in the amount of material required in order to form an article comprising first and second annular-sectioned elements in which one annular-sectioned element is provided in a groove formed in a circumferential surface of the other. 
         [0035]    It is to be understood that by axial expansion is meant expansion in a direction parallel to the longitudinal axis of the substantially annular-sectioned element. It is to be understood that a dimension of the annular element in a direction parallel to the longitudinal axis may be referred to herein as a length of the annular element. In the case that the annular-sectioned element is in the form or a tube, the longitudinal axis may be referred to as a cylinder axis. 
         [0036]    The method may comprise constraining lateral expansion of the annular-sectioned element during rolling by trapping between clamp members at least a portion of the annular-sectioned element during rolling. 
         [0037]    The method may comprise trapping between clamp members the substantially annular-sectioned element across substantially the whole of each axially opposed side of the element. 
         [0038]    This feature has the advantage that axial expansion is prevented across substantially the entire radial thickness of the element. 
         [0039]    The method may comprise forming the circumferential groove in one substantially annular-sectioned element to have an axial length that is sufficiently large to trap the other substantially annular-sectioned element in the groove when the first element is expanded in diameter. 
         [0040]    The method may comprise expanding the first substantially annular-sectioned element by stretching. 
         [0041]    The method may comprise expanding the first substantially annular-sectioned element by rolling. 
         [0042]    The method may comprise joining the first and second substantially annular-sectioned elements by fusing. 
         [0043]    The method may comprise joining the first and second elements by fusing substantially in the absence of an intermediate joining medium. 
         [0044]    By joining medium is meant a material arranged to bond to the first and second elements to substantially permanently bond the first and second elements together such as a solder, a brazing material or the like. 
         [0045]    It is to be understood that, when two materials are fused together, diffusion of material from at least one material to the other typically takes place, forming a bond between the materials. 
         [0046]    The performing of a fusing operation has particular advantages when a substantially annular-sectioned element of relatively low radial thickness is received into the circumferential groove formed in the other element. By fusing the elements, joining of the elements typically takes place over substantially the whole of the areas of the elements that face one another. Accordingly, if further fabrication steps are applied such as cutting the element received in the groove to pattern the element, islands or similar otherwise fragile regions of the element formed as a result of cutting typically remain adhered to the element in which the groove is formed. In the case of joining methods other than fusing such as soldering or brazing, gaps between areas in contact with intermediate joining material such as solder may exist, resulting in decohering of the islands or regions that are otherwise fragile. 
         [0047]    Optionally, the first and second substantially annular-sectioned elements are of a diameter in the range from substantially 5 mm to substantially 300 mm. 
         [0048]    Further optionally the article is arranged to be worn around one selected from amongst a finger and a wrist. 
         [0049]    The method may comprise forming the first substantially annular-sectioned element from a first material and the second substantially annular-sectioned element from a second material. 
         [0050]    Optionally the first and second materials are the same material. 
         [0051]    Alternatively the first and second materials may be different respective materials. 
         [0052]    The first and second materials may each comprise a precious metal. The first and second materials may comprise gold, silver, platinum or palladium. 
         [0053]    Optionally the step of positioning the second substantially annular-sectioned element around the first element comprises positioning a plurality of substantially annular-sectioned elements around the first element. 
         [0054]    Optionally, forming a circumferential groove in one of the first and second elements comprises forming a plurality of circumferential grooves in the element. 
         [0055]    The method may comprise providing an annular element in each of the plurality of grooves in said one of the elements. 
         [0056]    The method may comprise forming one or more of the annular-sectioned elements by cutting from a tube. 
         [0057]    Alternatively or in addition the method may comprise forming one or more of the annular elements by pressing a blank from a sheet, the blank being formed in the shape of an annulus, subsequently forming a tube element from the blank. 
         [0058]    Optionally, forming the tube element from the blank comprises forming the tube element by coning. 
         [0059]    In a further aspect of the invention for which protection is sought there is provided an article formed by a method according to another aspect. 
         [0060]    The article may comprise a jewellery ring suitable for being worn on a finger. 
         [0061]    The article may comprise a jewellery bangle suitable for being worn around a wrist. 
         [0062]    In an aspect of the invention for which protection is sought there is provided a method of forming an article comprising
       providing a first annular element comprising a substantially flat disc having an aperture formed therein;   forming a groove in a surface of the annular element;   placing a second element in the groove formed in the first element; and coning the first element to form a tube element comprising the first and second elements.       
 
         [0066]    The method may comprise subjecting the tube element to a drawing operation. 
         [0067]    Optionally, the groove may be provided in the form of an endless loop around an axis of rotation the first annular element. 
         [0068]    The may comprise forming the second element to be of a shape corresponding substantially to the groove, the second element being arranged to fit at least partially within the groove. 
         [0069]    Optionally, the second element is in the form of a substantially endless loop. 
         [0070]    Optionally, the first and second annular elements are substantially circular. 
         [0071]    In one aspect of the invention for which protection is sought there is provided a method of forming a substantially annular article comprising:
       providing a first annular element;   forming a circumferential groove in the first annular element by means of a roller in a rolling process;   providing a second annular element having an inner diameter that is greater than an outer diameter of the first element;   positioning the second annular element around the first annular element; and   expanding the first annular element with the second annular element positioned therearound until a diameter of the first annular element has increased sufficiently to trap the second annular element in the circumferential groove of the first element.       
 
         [0077]    In a further aspect of the invention for which protection is sought there is provided apparatus for forming a groove in an annular element comprising:
       element support means for supporting a substantially annular-sectioned element;   roller means supported by roller support means, the roller means being rotatable relative to the roller support means about a roller axis;   means for applying pressure between the roller means and an annular-sectioned element supported by the support means; and   means operable to allow relative movement between the annular-sectioned element and the roller support means such that the roller means is caused to roll around the annular-sectioned element in contact therewith to form a groove in the annular-sectioned element.       
 
         [0082]    It is to be understood that in some embodiments the roller support means may remain substantially stationary whilst the element support means permits the annular-sectioned element to rotate relative to the roller support means whilst the groove is being formed. In some alternative embodiments the element support means may hold the annular element substantially stationary whilst the roller support means is caused to rotate about the annular element, whilst the groove is being formed. In some embodiments the element support means may be configured to cause rotation of the annular element and in addition the roller support means may be configured to rotate about the annular element to form a groove in the annular element. 
         [0083]    The apparatus may further comprise means for constraining axial expansion of the annular-sectioned element in a direction parallel to a longitudinal axis thereof whilst the roller means is rolling therearound to form the groove. 
         [0084]    It is to be understood that plastic deformation of the annular-sectioned element typically occurs during rolling of the element to form the groove. By constraining axial expansion of the annular-sectioned element, an outer diameter of the annular-sectioned element will tend to increase in some embodiments as a depth of the groove formed in the element increases. This feature has the advantage that a starting thickness of the element may be reduced for a given required groove depth relative to embodiments in which axial expansion is not constrained during rolling. This in turn allows a reduction in the amount of material required in order to form an article. In some embodiments, post-rolling finishing of the annular-sectioned element to trim unsightly deformation of opposite axial edges of the annular-sectioned element due to axial expansion during rolling may be rendered unnecessary due to the fact that axial expansion has been constrained. 
         [0085]    By constraining is meant that axial expansion is substantially prevented or at least reduced relative to rolling in which axial expansion is substantially unconstrained. 
         [0086]    Optionally the means for constraining lateral expansion comprises clamping means having first and second clamp portions arranged to be positioned on opposite sides of the annular-sectioned element. 
         [0087]    It is to be understood that one or both of the clamp portions may be provided by a portion of a component of the apparatus such as a portion of a base, a housing or other portion of the apparatus. Alternatively, separate clamp portions in the form of clamp elements may be provided. 
         [0088]    It is to be understood that the annular-sectioned element may be provided in the form of a tube element having a tube length. The annular-sectioned element may comprise a ring element. The ring element may comprise a relatively short tube element. By relatively short is meant that an axial length of the tube element in a direction parallel to a cylinder axis thereof may be less than a radius of the tube element, optionally less than or substantially equal to substantially 50% of a radius of the tube element, optionally less than or substantially equal to substantially 40% of a radius of the tube element, further optionally less than or substantially equal to substantially 30% of a radius of the tube element, still further optionally less than or substantially equal to substantially 20% of a radius of the tube element. The length of the tube element may be greater than or equal to substantially 5% of the radius of the tube element. 
         [0089]    Further optionally, the means for supporting the annular-sectioned element comprises a shaft member around which the annular-sectioned element may be positioned. 
         [0090]    It is to be understood that the first and second clamp portions may be arranged to be coupled to the shaft member, optionally with the shaft member passing therethrough. 
         [0091]    The apparatus may comprise roller support means for supporting the roller means for rotation about the roller axis. 
         [0092]    The apparatus may be configured to cause the roller support means to describe a substantially circular path about the annular-sectioned element, in use. 
         [0093]    Optionally, the element support means is configured to support the annular-sectioned element in a substantially fixed position, in use. 
         [0094]    The apparatus may comprise means for rotating the annular-sectioned element relative to the roller support means. 
         [0095]    Optionally, the element support means is configured to cause rotation of the annular-sectioned element relative to the roller support means. 
         [0096]    The apparatus may be operable to cause translation of the roller support means towards and away from the element support means whereby pressure may be applied between the roller means and an annular-sectioned element supported by the element support means. 
         [0097]    The apparatus may comprise at least one powered actuator, the apparatus being configured automatically to cause relative movement between the substantially annular-sectioned element and the roller support means by means of the powered actuator such that the roller means is caused to roll around the substantially annular-sectioned element in contact therewith to form the groove in the element. 
         [0098]    In an aspect of the invention for which protection is sought there is provided a method of forming a groove in a substantially annular-sectioned element comprising:
       supporting the annular element by means of element support means;   applying pressure between roller means supported by roller support means and the annular element; and   causing relative movement between the annular element and the roller support means such that the roller means is caused to roll around the annular element in contact therewith to form a groove in the annular element, the roller means being caused to rotate relative to the roller support means about a roller axis.       
 
         [0102]    In one aspect of the invention for which protection is sought there is provided a method of forming an article comprising:
       providing a first substantially cylindrical element;   forming a circumferential groove in a radially outer surface of the first cylindrical element by a process of rolling;   providing a second substantially cylindrical element having an inner diameter that is greater than an outer diameter of the first element;   positioning the second annular element around the first annular element; and   expanding a diameter of the first annular element with the second annular element positioned therearound.       
 
         [0108]    The article may be substantially ring-shaped. 
         [0109]    In one aspect of the invention for which protection is sought there is provided a method of forming a substantially annular article comprising:
       providing a first annular element;   forming a circumferential groove in the first annular element by rolling;   providing a second annular element having an inner diameter that is greater than an outer diameter of the first element;   positioning the second annular element around the first annular element; and   expanding the first annular element with the second annular element positioned therearound until a diameter of the first annular element has increased sufficiently to trap the second annular element in the circumferential groove of the first annular element.       
 
         [0115]    In one aspect of the invention for which protection is sought there is provided a method of forming a substantially annular article comprising:
       providing a first annular element;   providing a second annular element having an inner diameter that is greater than an outer diameter of the first element;   positioning the second annular element around the first annular element; and   rolling the first annular element with the second annular element positioned therearound until a diameter of the first annular element has increased sufficiently to trap the second annular element in the circumferential groove of the first element.       
 
         [0120]    The use of rolling to increase the diameter of the first annular element and trap the second has the advantage that an article such as a double ring may be formed more quickly and/or with less damage compared with alternative methods of forming an article such as by stretching without rolling or by crimping. 
         [0121]    Furthermore, a more uniform expansion of the first annular element may be enabled by the rolling process compared with other expansion methods. In addition, in some embodiments rolling of the first annular element causes rolling of the second annular element also, with a corresponding reduction in thickness of the second annular element. This can enable double rings to be produced in which the second annular element is thinner than in known double rings. This can reduce the amount of precious metal required to form the second annular element, and therefore reduce the cost of the double ring, in some embodiments. 
         [0122]    Some embodiments of the present invention have the advantage that a second annular element of reduced thickness (in a radial direction) may be employed. This is because the groove may be formed to a more precise depth and in some embodiments a more shallow depth by rolling compared to cutting. Thus, the first annular member may be formed to be thinner than prior art members because it is not required to support as deep a groove. The second annular element may be formed to have a thickness lower than that of known articles since the groove may be made to a more precise depth, eliminating the requirement to finish the article by trimming a thickness of the second element (typically by turning and cutting in a lathe) so that it does not stand proud of the first element, following expansion of the first element. 
         [0123]    The ability to employ a second annular element (and/or a first annular element) of reduced thickness has the advantage that the amount of precious metal required to be used to form the article may be reduced, reducing in turn a cost of materials required to form each article. 
         [0124]    The annular element may be an element having a substantially annular section. The annular element may be in the form a ring such as a short section of tube. The annular element may be formed by coning a substantially flat disc with an aperture formed therein, the disc being in the shape of an annulus. 
         [0125]    Advantageously the method comprises forming a circumferential groove in a radially outer surface of the first element prior to positioning the second element around the first element. 
         [0126]    Further advantageously the method comprises forming the circumferential groove by rolling. 
         [0127]    This feature has the advantage that loss of material due to turning and cutting the first annular element may be avoided. This reduces wastage of valuable material, which is typically recycled. By avoiding cutting, the step of recycling may be avoided. Use of cutting equipment may also be avoided. 
         [0128]    The method may comprise forming the circumferential groove to have a length parallel to a cylinder axis of the first element that is sufficiently large to trap the second annular element in the groove when the first annular element is subsequently rolled. 
         [0129]    It is to be understood that in some embodiments when the first element is expanded by rolling to trap the second element, the groove shrinks in length parallel to the longitudinal axis of the element to trap the second element. The second element may be arranged to be trapped by an interference fit within the groove. Other arrangements are also useful. 
         [0130]    The annular article may be arranged to be worn around one selected from amongst a finger or wrist. 
         [0131]    Optionally, the first annular elementis of an inside diameter in the range from substantially 10 mm to substantially 25 mm, optionally in the range from around 14 mm to around 22 mm. This size range is found to be suitable for manufacturing rings to be worn on fingers. Thus, the annular elements may be ring elements for forming a ring to be worn on a digit of a person, such as a finger or thumb. Such rings typically have an inside diameter in the size range from 13.370 mm (inside circumference 42 mm) to 23.877 mm (inside circumference 75 mm). Other sizes are also useful. 
         [0132]    Alternatively the first annular element may have an inside diameter in the range from around 70 to 75 mm. This size range is found to be suitable for manufacturing bangles to be worn around a wrist. 
         [0133]    The bangles may have an inside diameter in the range from 54mm (inside diameter 169.7 mm) to 75 mm (inside diameter 235.7 mm). 
         [0134]    The method may comprise forming the first annular element from a first material and the second annular element from a second material. 
         [0135]    The first and second materials may be substantially the same material. 
         [0136]    The first and second materials may be different respective materials. 
         [0137]    For example, the first and second materials may comprise different elements, or comprise alloys of different respective compositions. 
         [0138]    The first and second materials may comprise a precious metal. 
         [0139]    For example, the first and second materials may comprise gold, silver or platinum. 
         [0140]    Other materials and other non-precious metals and combinations thereof may also be useful. 
         [0141]    The precious metal may be a coloured gold such as a white gold, a yellow gold or a red gold. Other types of gold may also be useful. It is to be understood that coloured gold may be formed by alloying gold with silver and/or copper in various proportions to produce white, yellow, green and/or red golds. In some embodiments intermetallic compounds, producing blue and purple golds, as well as other colours, may be employed. The production of coloured golds is well understood by persons skilled in the art. 
         [0142]    It is to be understood that the first and second annular elements may be formed from respective different precious metals. For example the first element may be formed from yellow gold and the second element may be formed from white gold or red gold. Other arrangements are also useful. 
         [0143]    The step of positioning a second annular element around the first annular element may comprise positioning a plurality of annular elements around the first annular element. 
         [0144]    Optionally the step of forming a circumferential groove comprises forming a plurality of circumferential grooves in the first element. 
         [0145]    Optionally the method may comprise providing an annular element in each of the plurality of grooves in the first element. 
         [0146]    The method may comprise forming one or more of the annular elements by cutting from a tube. 
         [0147]    The method may comprise forming one or more of the annular elements by pressing a blank from a sheet, the blank being formed in the shape of an annulus, subsequently forming a tube element from the blank. 
         [0148]    Optionally, forming the tube element from the blank comprises forming the tube element by coning. 
         [0149]    Thus, optionally, the blank may be subject to one or more coning operations whereby the blank is ‘coned’ to form a slug in the form of a relatively short length of tube. The coning operation involves forcing the blank through a die in order to deform the blank into a cone shape (a frusto-conical shape). The slug may then be subjected to one or more drawing operations in a die until the slug is of a substantially uniform wall thickness and substantially constant diameter along a length thereof. 
         [0150]    Thus, the one or more drawing operations will typically ensure that sides of the slug are substantially parallel and of substantially constant thickness along a length of the slug. 
         [0151]    It is to be understood that the coning operation effectively twists the sheet of material from which the blank is formed by substantially 90 degrees, to form a relatively short length of tube. 
         [0152]    Forming the slug in this manner has the advantage that a jewellery maker is not required to keep substantial lengths of tube of precious metal in stock, with tubes of different size for different article diameters. 
         [0153]    In a further aspect of the invention for which protection is sought there is provided an article formed by a method according to any preceding aspect. 
         [0154]    In a still further aspect of the invention for which protection is sought there is provided a method of forming an article comprising:
       providing a first annular element substantially in the shape of a substantially flat washer or annulus;   forming a groove in a surface of the annular element;   placing a second element in the groove formed in the first element; and coning the first element to form a substantially cylindrical slug comprising the first and second elements.       
 
         [0158]    The substantially cylindrical slug may be in the form of a right cylinder having a substantially constant inner diameter. Alternatively the slug may be frusto-conical in shape, having an inner diameter that decreases in a direction parallel to a longitudinal axis thereof. 
         [0159]    The method may comprise subjecting the slug to a drawing operation. 
         [0160]    Optionally, the groove is provided in the form of an endless loop around an axis of the first annular element. 
         [0161]    The method may comprise forming the second element to be of a shape corresponding substantially to the groove, the second element being arranged to fit at least partially within the groove. 
         [0162]    The method may comprise joining the first and second elements, for example by means of soldering or brazing, to retain the second element within the groove. In some embodiments the first and second elements may be joined by fusing. That is, the elements may be joined without the use of an intermediate joining medium or material such as a solder. The fusing process may involve heating of the first and second joining elements to a temperature at which interdiffusion of material from one element to the other, optionally from each element to the other, may occur. 
         [0163]    The second element may therefore be combined with the first element on a substantially flat surface of the blank pre-coning. Some embodiments of the invention have the advantage that a rolling operation to increase a diameter of the first element may be eliminated since the coning operation (and optionally the drawing operation in addition) may be sufficient to cause the first and second elements to be of a snug fit together. 
         [0164]    Optionally, the second element is in the form of a substantially endless loop. 
         [0165]    Alternatively the second element may be discontinuous. The second element may be formed by joining ends of a length of material to form a substantially continuous, endless element. 
         [0166]    The second element may be oriented radially rather than circumferentially in some embodiments. For example the second element may be provided with a longitudinal axis thereof substantially parallel to a radial direction, for example in the manner of a spoke of a wheel. 
         [0167]    A plurality of second elements may be provided. 
         [0168]    The first and second annular elements may be substantially circular. 
         [0169]    As noted above, in an alternative embodiment the second annular elements may be non-circular. The second annular elements may be substantially linear. Other arrangements are also useful. 
         [0170]    The first and second elements may be formed from a similar or different metal. The second element may be formed to have a corrugated profile. Other arrangements are also useful. 
         [0171]    In a further aspect of the invention for which protection is sought there is provided an article formed by a method according to a preceding aspect. 
         [0172]    The article may be an article of jewellery, optionally a finger ring, a wrist band, a bracelet or a bangle or like article. 
         [0173]    Within the scope of this application it is envisaged that the various aspects, embodiments, examples and alternatives, and in particular the individual features thereof, set out in the preceding paragraphs, in the claims and/or in the following description and drawings, may be taken independently or in any combination. For example features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
         [0174]    For the avoidance of doubt, it is to be understood that features described with respect to one aspect of the invention may be included within any other aspect of the invention, alone or in appropriate combination with one or more other features. 
         [0175]    Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0176]    One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which: 
           [0177]      FIG. 1  illustrates a process of forming a double ring according to an embodiment of the present invention; 
           [0178]      FIG. 2  illustrates a structure of a double ring according to an embodiment of the present invention (a) before and (b) after rolling of inner and outer ring elements to form a single double ring; 
           [0179]      FIG. 3  shows first and second ring elements according to an embodiment of the present invention in (a) plan view, (b) front view and (c) perspective view; 
           [0180]      FIG. 4  shows a triple ring according to an embodiment of the present invention; 
           [0181]      FIG. 5  shows a cross-sectional view of (a) a double ring structure and (b) a triple ring structure according to an embodiment of the present invention, and (c) a process of forming a single sided groove in a ring element for forming a double or triple ring structure according to an embodiment of the present invention; 
           [0182]      FIG. 6  shows a cross-sectional view of a double ring structure in which an inner ring element is inset in a double sided groove formed in an inner radial surface of an outer ring element; 
           [0183]      FIG. 7  shows a cross-sectional view of a double ring structure in which an inner ring element is inset in a single sided groove formed in an inner radial surface of an outer ring element; 
           [0184]      FIG. 8  is a schematic view of apparatus according to an embodiment of the present invention for forming a groove in a ring element; 
           [0185]      FIG. 9  is an enlarged view of the apparatus of  FIG. 8  showing the manner in which a ring element is gripped; 
           [0186]      FIG. 10  illustrates a process of forming a double ring according to a further embodiment of the invention; 
           [0187]      FIG. 11  illustrates (a) a blank assembly formed from first and second blanks, and (b) the assembly following coning to form a tube element; and 
           [0188]      FIG. 12  illustrates (a) a tube element formed by a method according to an embodiment of the present invention, (b) a blank assembly according to an embodiment of the invention having a second blank element of substantially spiral form inset in a first blank element in the form of a substantially flat disc, and (c) a tube element formed by coning the blank assembly shown in (b). 
       
    
    
     DETAILED DESCRIPTION 
       [0189]    Some embodiments of the present invention are directed to providing an article of jewellery comprising two or more ring elements that are combined in a single article. 
         [0190]      FIG. 1  shows part of a process of forming an article according to one embodiment of the invention in the form of a double ring  140  shown in  FIG. 2( b ) . In the present embodiment illustrated the article  140  is a finger ring, in particular a finger ring of the ‘double ring’ type in which two ring elements are combined to form a single article  140 . Double rings are typically formed such that each ring element is formed from a different precious metal, for example a yellow gold and a red gold, a white gold and a red gold, or any desired combination of red, yellow and white gold. In some embodiments of the present invention other precious metals may be used in addition or instead, such as platinum or silver or any other suitable metal. 
         [0191]    In the present embodiment an annular blank of material  100  ( FIG. 1( a ) ) is first formed by pressing from a sheet of material. The blank  100  may be described as being substantially in the shape of a ‘washer’. In other words, the annular blank  100  is in the form of a substantially flat, circular disc with a circular hole therethrough. In the present example the circular hole through the disc (which may also be described as an aperture) has a geometric centre substantially coincident with that of the disc. That is, the disc and aperture or hole therein are substantially coaxial. 
         [0192]    The material may be any suitable material but in the present embodiment the material is a precious metal. The metal may be any suitable precious metal such as gold, silver, platinum, a coloured gold in the form of an alloy of gold with silver and/or copper such as white gold, yellow gold or red gold, or any suitable metal. 
         [0193]    It is to be understood that gold of different colours such as white, yellow or red gold is typically produced by alloying gold with one or more of silver or copper. A reddish coloured gold may be formed by alloying with copper, whilst a whitish gold may be formed by alloying with silver. Mixtures of gold, copper and silver may be employed depending on the colour or shade of colour required. 
         [0194]    After forming the blank  100 , the blank  100  is coned in a coning operation whereby the sheet of metal from which the blank is formed is rotated or twisted through substantially  90  degrees from the substantially flat initial shape shown in  FIG. 1( a )  through a cone-like shape (frusto-conical shape) shown in  FIG. 1( b )  through to a slug  120  having a substantially tubular shape as shown in  FIG. 1( c ) . 
         [0195]    The process of starting from a sheet, producing a washer and then forming a short section of tube by a series of coning processes (which involve drawing of the blank  100  by means of a die) may be referred to as the Klink process in some embodiments. The short section of tube produced is referred to herein as a ‘slug’ but may also be referred to as a ‘do-nut’ or ‘donut’. It is to be understood that one or more annealing processes may be performed between coning and drawing operations to relieve mechanical stress due for example to work hardening. An annealing process may be performed at any stage of the process of fabricating an article, as required. 
         [0196]    The slug may then be subject to a drawing process in which the slug is drawn by means of a die to ensure that the wall of the slug is of substantially uniform thickness and substantially constant diameter along a length thereof. The resulting structure may be referred to as a ring element  120 R as shown in  FIG. 1( c ) . 
         [0197]    The ring element  120 R is then placed between first and second rollers R 1 , R 2  as shown in  FIG. 1( d ) . Roller R 1  has a ridge portion R 1   r  formed around a peripheral surface thereof shaped to form a recess of groove  125  in the outer circumferential surface of the ring element  120 R when the ring element  120 R is placed between the rollers R 1 , R 2 . The second roller R 2  is substantially flat around the peripheral surface. The ring element  120 R is ‘rolled’ between the rollers R 1 , R 2  which are urged together under pressure until the recess  125  is sufficiently deep to receive a second ring element  130 R ( FIG. 1( e )  and  FIG. 2 ) therein such that a radially outer surface of the second ring element  130 R is substantially flush with a radially outer surface of the first ring element  120 R. The ring element  120 R may be subject to an annealing treatment before, during and/or after rolling to form the recess or groove  125 . 
         [0198]    It is to be understood that in some embodiments the first roller R 1  may have two or more ridge portions R 1   r  thereby to form a corresponding two or more recesses  125  in the ring element  120 R. 
         [0199]    In some embodiments, in addition or instead the second roller R 2  may have one or more ridge portions formed in the radially outer surface facing the radially inner circumferential surface of the ring element  120 R so as to form a groove in the radially inner surface of the ring element  120 R. 
         [0200]    After forming the recess  125  in the first ring element  120 R, the second ring element  130 R is formed in a similar manner to the first  120 R and presented to the first ring element  120 R. The second ring element  130 R has an internal diameter greater than an outer diameter of the first ring element  120 R, allowing the first ring element  120 R to be positioned concentrically with respect to the second ring element  130 R. 
         [0201]    The second ring element  130 R is of a length L parallel to a cylinder axis thereof that is sufficiently small to fit within the recess  125  formed in the first ring element  120 R. As noted above, in the present example a thickness t of the second ring element  130 R is substantially equal to the depth d of the recess or groove  125  formed in the ring element  120 R. In some alternative embodiments the second ring element  130 R may be of a thickness t greater than the depth d of the recess  125  formed in the first ring element. In some further alternative embodiments the second ring element  130 R may be of a thickness t lower than the depth d of the recess  125  formed in the first ring element. 
         [0202]      FIG. 3  illustrates the second ring element  130 R being offered to the first ring element  120 R.  FIG. 3( a )  shows a view from above whilst  FIG. 3( b )  shows a front view, parallel to a cylinder axis CA of the ring elements  120 R,  130 R.  FIG. 3( c )  is a 3D view of the configuration shown in  FIG. 3( a ) . 
         [0203]    It can be seen that in the present embodiment the second ring element  130 R is arranged to have an inside diameter that is sufficiently large to allow it to fit over the first ring element  120 R. The inside diameter of the second ring element  130 R may be substantially the same as an outer diameter of the first ring element  120 R in some embodiments, provided the second ring element  130 R may be slid or otherwise provided around the first ring element  120 R. 
         [0204]    In the present embodiment, the first and second ring elements  120 R,  130 R are then placed between a further pair of rollers, third and fourth rollers R 3 , R 4  as shown in  FIG. 1( e )  such that the second ring element  130 R is held securely within the recess  125  formed in the first ring element  120 R. The first and second ring elements  120 R,  130 R are then rolled between the rollers R 3 , R 4 , pressure being applied by the rollers to cause the first ring element  120 R to increase in diameter. 
         [0205]    In the present embodiment roller R 3  has a diameter of around 100 mm whilst roller R 4  has a diameter of around 8 mm. Other sizes and relative sizes are also useful. 
         [0206]    It is to be understood that the second ring element  130 R may also increase in diameter during rolling between the rollers R 3 , R 4  in some embodiments, in addition to the first ring element  120 R. However in such a case the first ring element  120 R is arranged to increase in diameter at a faster rate than the second ring element  130 R such that the first ring element  120 R expands to capture the second ring element  130 R snugly within the recess  125  around substantially the entire diameter of the first ring element  120 R. The second ring element  130 R is thereby constrained such that it cannot become detached from the first ring element  120 R. It is to be understood that the groove  125  formed in the first ring element  120 R may contract in length parallel to the cylinder axis CA thereof during the rolling process, gripping the second ring element  130 R and preventing relative movement once the fabrication process is complete. It is to be understood that a thickness of the first ring element  120 R in a radial direction will reduce as a consequence of the rolling process, which results in an increase in circumference of the ring element  120 R. The ring element  120 R is therefore formed initially to have a radial thickness that is greater than the intended thickness at the end of the rolling operation. 
         [0207]    It is to be understood that deforming the first and second ring elements  120 R,  130 R by rolling facilitates the formation of an article for which little or no further processing is required in respect of the addition of the second ring element  130 R to the first  120 R. That is, an outer diameter of second ring element  130 R may become substantially the same as the outer diameter of the first ring element  120 R. As such, trimming of the second ring element  130 R by cutting in a lathe or other means is not required in some embodiments. For example, in the prior art example described above, stretching of the first ring element without rolling is performed until the second ring element becomes securely embedded in the groove formed in the first ring element  120 R by cutting. The second ring element  130 R may therefore not increase in diameter at all, or at least not by any significant amount. It is therefore important to ensure that a depth of the groove formed in the first ring element will correspond substantially to the thickness of the second ring element when the first ring element has been stretched to grip the second ring element. This is not an easy task to achieve, and trimming of the second ring element to reduce the radial thickness thereof is typically required. In contrast, rolling of the first and second ring elements  120 R,  130 R together may be arranged to have the effect that the first and second elements  120 R,  130 R have substantially the same outer diameter at the end of the rolling process, eliminating the need to trim either of the elements  120 R,  130 R. 
         [0208]    Furthermore, because both the first and second ring elements  120 R,  130 R will typically experience some increase in circumference and therefore reduction in radial thickness as a consequence of the rolling process, some embodiments of the present invention allow the second ring element  130 R to be formed to have a lower thickness than would otherwise be achievable reliably and reproducibly using known techniques. By way of example, in some embodiments of the present invention the first and second ring elements  120 R,  130 R may be arranged to increase in diameter by at least a factor of from around 1.5 to around 2 or 3, as required. Larger or smaller increases in diameter may be useful in addition or instead in some embodiments. 
         [0209]    It is to be understood that the first and second ring elements  120 R,  130 R may be subject to an annealing treatment before, during and/or after the rolling operation in order to ensure adequate softness of the ring elements  120 R,  130 R during rolling and any subsequent processing. 
         [0210]    In some alternative embodiments, the first and second ring elements  120 R,  130 R are formed using the process described above with respect to  FIG. 1( a ) to ( c )  and a groove formed in the outer circumferential surface of the first ring element  120 R as described with respect to  FIG. 1( d ) . Subsequently, the first ring element  120 R is stretched to trap the second ring element  130 R in the circumferential groove  125  formed in the first ring element  120 R. 
         [0211]    It is to be understood that the second ring element  130 R may be held within the groove  125  formed in the first ring element  120 R without any further joining processes being required in some embodiments, such as soldering. Alternatively, the first and second ring elements  120 R,  130 R may be joined by soldering or brazing. Alternatively, the first and second ring elements  120 R,  130 R may be joined by fusing the elements together. The article  140  may be heated to allow interdiffusion of metal between the elements  120 R,  130 R to form a bond between them. In the case of an article  140  having ring elements  120 R,  130 R formed from gold or silver, the article  140  may be heated to a temperature of around  600 C to  700 C for a sufficient period of time to cause fusion, for example a period of around  30   s,    60   s,    120   s  or any other suitable period of time. It is to be understood that the use of diffusion bonding processes not requiring the addition of an intermediate material to join the elements  120 R,  130 R has the advantage of simplifying manufacture and/or reducing cost. Furthermore, in some embodiments a requirement to undertake a post-joining finishing operation, for example so as to remove excess intermediate material such as excess solder or other joining material, may be eliminated in some embodiments. 
         [0212]    The article  140  formed by combining the first and second ring elements  120 R,  130 R as illustrated in  FIG. 1  to  FIG. 3  may be referred as a ‘double ring’ structure. As noted above, a triple ring structure may be formed by combing a third ring element with the first and second ring elements.  FIG. 4  illustrates an example of a triple ring structure  240  in which a first ring element  220 R has second and third ring elements  231  R,  232 R provided in respective recesses  225  formed in the first ring element  220 R. Other arrangements are also useful. 
         [0213]    It is to be understood that in some embodiments the groove or recess  225  may be formed at an edge of the first ring element  220 R such that a side edge  230 Re of the second ring element  230 R at a first end  220 R 1  of the first ring element is visible when the first and second ring elements  220 R,  230 R are combined. Examples of such structures are illustrated schematically in  FIG. 5 . Such a groove  225  may be referred to as a ‘single sided’ groove in contrast to the ‘double sided’ groove  225  of the embodiments of  FIGS. 1 to 4 . 
         [0214]      FIG. 5( a )  is a cross-sectional view of a portion of a double ring structure according to an embodiment of the present invention in which a single sided groove or recess  225  is formed along or around one free edge of the first ring element  220 R prior to expansion of the first ring element  220 R. The second ring element  230 R has been inserted into the groove  225  by sliding from free end  220 R 1  of the first ring element  220 R. The second ring element  230 R was formed such that an inner diameter of the second ring element  230 R was sufficiently large to allow the element  230 R to be placed in the groove  225  such that a side edge  230 Re on one side thereof is in abutment with shoulder or sidewall  225 S of the recess  225 . The opposite side edge  230 Re is exposed and substantially flush with side edge  220 Re of the first ring element  220 R. It is to be understood that the first ring element  220 R has been caused to expand in diameter with the second ring element  230 R so held, causing a friction fit to be established between the second ring element  230 R and the first ring element  220 R. It is to be understood that the friction fit may in some embodiments be formed to be sufficiently constraining of movement of the second ring element  230 R to prevent separation of the first and second ring elements  220 R,  230 R in normal use. That is, the diameter of the first ring element  220 R may be cause to expand so as to cause sufficient radial pressure to be exerted between the first and second ring elements  220 R,  230 R such that separation of the first and second ring elements  220 R,  230 R does not occur in normal use. 
         [0215]    In some embodiments, complementary interengaging formations may be provided on radially facing surfaces of the first and second ring elements  220 R,  230 R such that separation of the first and second ring elements  220 R,  230 R is resisted, and substantially prevented in normal use. In addition or instead, in some embodiments one or both surfaces may be roughened so as to increase resistance of the elements  220 R,  230 R to separation. 
         [0216]    In some embodiments, the first and second ring elements  220 R,  230 R may be bonded together in order to reduce the risk of separation of the ring elements  220 R. The elements may be bonded by means of a diffusion bonding process, for example by annealing at a sufficiently high temperature to allow interdiffusion of material from one ring element to the other, optionally from each ring element  220 R,  230 R to the other  230 R,  220 R. In some alternative embodiments an intermediate joining material may be employed such as a solder material. 
         [0217]      FIG. 5( b )  is a cross-sectional view of a portion of a triple ring structure  1240  according to a further embodiment of the present invention. Like features of the embodiment of  FIG. 5( b )  to those of the embodiment of  FIG. 5( a )  are shown with like reference signs prefixed incremented by  1000 . In the embodiment of  FIG. 5( b )  a groove or recess  1225  has been formed along or around opposite free edges of the first ring element  1220 R. Second and third ring elements  1231 R,  1232 R have been provided in the respective recesses  1225  and the diameter of the first ring element  1220 R subsequently expanded to trap the second and third ring elements  1231 R,  1232 R in the respective recesses 12 . It is to be understood that in some embodiments the first, second and third ring elements  1220 R,  1231 R,  1232 R may each be of a different respective composition. In some embodiments the ring elements  1220 R,  3 ,  1232 R may be of different respective coloured metals. The ring elements  1220 R,  1231  R,  1232 R may have different respective amounts of one or more of the elements gold, silver and copper. One ring element may be formed from a red gold, one formed from a yellow gold and one formed from a white gold in some embodiments. 
         [0218]      FIG. 5( c )  illustrates a method of forming a single sided groove in the first ring element  1220 R. It can be seen that the first ring element  1220 R is rolled between first and second rollers R 1 , R 2 , roller R 1  having a ridge portion R 1  r at one end thereof for forming the single sided groove  1225 . Roller R 1  is caused to rotated about roller axis R 1 A whilst roller R 2  is caused to rotate about roller axis R 2 A. 
         [0219]    It is to be understood that the relative lengths of the first and second and any further ring elements may be of any required values. In some embodiments the second ring element provided in the groove may be approximately 50% of the length of the first element although any other suitable value may be employed such as 90%, 80%, 70%, 60%, 40%, 30%, 20%, 10% or any other suitable value. 
         [0220]    In some embodiments, a recess or groove may be formed in the second ring element  130 R on a radially inner, circumferential surface instead of the radially outer circumferential surface of the first ring element  120 R as per the embodiments of  FIG. 1  to  FIG. 5 . This may be accomplished by reversing the relative positions and optionally the relative sizes of the first and second rollers R 1 , R 2  in  FIG. 1( d )  to form the groove on the radially inner surface of the second ring element  130 R. The first ring element  120 R may then be placed on an inside of the second ring element  130 R and the first and second ring elements  120 R,  130 R rolled to reduce the difference in diameter between the first and second ring elements  120 R,  130 R. The diameter of the first ring element  120 R is increased at a rate greater than the first  130 R to cause the second ring element  120 R to expand to sit within the groove formed in the second ring element  130 R. Alternatively, the first ring element  120 R may be expanded by stretching to cause the first ring element  120 R to be received within the groove formed in the second ring element  130 R. 
         [0221]      FIG. 6  illustrates a double ring structure  1340  according to a further embodiment of the present invention. Like features of the embodiment of  FIG. 6  to those of the embodiment of  FIG. 5  are shown with like reference signs incremented by  100 . In the embodiment of  FIG. 6  a groove  1325  has been formed in a radially inner surface  1330 Ri of second ring element  1330 R. A first ring element  1320 R of complementary shape to the groove  1325  has been expanded by stretching to substantially fill the groove  1325 . A fusion bonding process has then been performed in which the structure  1340  is heated to cause fusion of the first and second ring elements  1320 R,  1330 R together. 
         [0222]      FIG. 7  illustrates a double ring structure  1440  according to a further embodiment of the present invention. Like features of the embodiment of  FIG. 7  to those of the embodiment of  FIG. 6  are shown with like reference signs incremented by  100 . In the embodiment of  FIG. 7  a groove  1425  has been formed in a radially inner surface  1430 Ri of second ring element  1430 R. A first ring element  1420 R of complementary shape to the groove  1425  has been expanded by stretching to substantially fill the groove  1425 . A fusion bonding process has then been performed in which the structure  1440  is heated to cause fusion of the first and second ring elements  1420 R,  1430 R together. 
         [0223]    It is to be understood that, in some embodiments, prior to performing the fusion bonding process, axial pressure may be applied to the structures  140  described herein in order to reduce or substantially eliminate any gap between the first and second ring elements  120 R,  130 R. This has the advantage that an improved bond may be formed between the between the first and second ring elements  120 R,  130 R. Application of axial pressure may be performed in a stamping, crimping or ‘squashing’ operation, with force being applied to compress the structure  140  parallel to the longitudinal axis thereof. 
         [0224]    It is to be understood that, in some embodiments, expansion of a first ring element according to an embodiment of the invention (such as element  120 R,  220 R and so forth) may be performed by stretching of the first ring element  220 R rather than rolling of the first, second and optionally one or more further ring elements together in a rolling operation. The stretching operation may be performed using known ring stretching devices. For example in some embodiments a ring stretching device may be provided in the form of a known split shaft arrangement in which a hollow split shaft is provided that is arranged to allow an expansion member such as a tapered rod to be driven axially at least partially through the split shaft, causing radial expansion of the split shaft in a known manner. By placing the first ring element  220 R around the split shaft with the second ring element  230 R around the first  220 R, the first ring element  220 R may be expanded to trap the second ring element  230 R within the groove  225  when the tapered rod is driven through the split shaft, or to trap a first ring element  1320 R in a groove  1325  formed in the second ring element  1330 R. 
         [0225]      FIG. 8  and  FIG. 9  illustrate an apparatus  460  according to an embodiment of the present invention for forming a groove  425  in a ring element  420 R by means of a rolling process. The apparatus  460  has a base portion  462  having a threaded shaft portion  462 S having a longitudinal or cylinder axis A. The shaft portion  462 S projects from the base portion  462  in a direction substantially normal to a basal face  462 F of the base portion  462 . In the embodiment illustrated in  FIG. 6  the shaft portion  462 S is shown projecting substantially vertically upwards. Other orientations of the shaft portion  462 S may be useful in some embodiments. In some embodiments the shaft portion  462 S may instead be mounted in a substantially horizontal orientation. 
         [0226]    The shaft portion  462 S is arranged to receive first and second bearing portions  462 B 1 ,  462 B 2  thereon. The bearing portions  462 B 1 ,  462 B 2  have threaded bores corresponding to the external thread of the shaft portion  462 S. A diameter D of the shaft portion  462 S is arranged to allow insertion of the shaft portion  462  through the ring element  420 R. 
         [0227]    In use, the first bearing portion  462 B 1  is screwed to the threaded shaft portion  462 S such that it is substantially in abutment with the basal face  462 F of the base portion  462 . One or more washers may be provided between the base portion and first bearing portion  462 B 1  in some embodiments. The ring element  420 R is then passed over the shaft portion  462 S and into abutment with the first bearing portion  462 B 1 . The second bearing portion  462 B 2  is subsequently screwed to the threaded shaft portion  462 S such that the ring element  420 R is trapped between the first and second bearing portions  462 B 1 ,  462 B 2 . The ring element  420 R is held firmly between the first and second bearing portions  462 B 1 ,  462 B 2  substantially without deforming the ring element  420 R due to the pressure applied by the bearing portions  462 B 1 ,  462 B 2  thereto. 
         [0228]    The apparatus  460  also has a roller element  465 R mounted for rotation about an axle  465 A that is supported at opposed ends thereof in a recess  465 CR provided in a carriage portion  465 C. In the present embodiment the axle  465 A is oriented substantially parallel to the shaft portion  462 S. 
         [0229]    The carriage portion  465 C is coupled to and supported by a carriage support portion  465 CS that is configured for rotary movement about the base portion  462 , about an axis substantially coincident with the longitudinal axis A of the shaft portion  462 S. The carriage support portion  465 CS has a handle portion  466  that projects radially outwardly from the carriage support portion  465 C, allowing an increased moment to be applied to cause rotation of the carriage support portion  465 CS, and thereby the carriage portion  465 C, about the base portion  462 . 
         [0230]    The carriage support portion  462 CS is configured to be movable with respect to the carriage portion  465 C radially towards and away from the shaft portion  462 S by means of a screw adjuster  465 CA, allowing the roller element  465 R to be moved in a corresponding manner towards and away from the ring element  420 R mounted between the bearing portions  462 B 1 ,  462 B 2 . The axial position of the ring element  420 R may be adjusted by adjusting the axial positions of the bearing portions  462 B 1 ,  462 B 2 . In the present embodiment the screw adjuster  465 CA is configured to actuate a wormscrew mechanism in order to cause movement of the carriage portion  465 C relative to the carriage support portion  465 CS. 
         [0231]    The roller element  465 R has a circumferential ridge portion  465 RR disposed centrally with respect to a circumferential face  465 RF of the element  465 R. In the present embodiment the roller element  465  has a length LRL that is similar to that of the length LR of the ring element  420 R. The length LRL of the roller element  465  and the diameters of the first and second bearing portions  462 B 1 ,  462 B 2  are sized to allow the roller element  465 R to be positioned between the first and second bearing portions  462 B 1 ,  462 B 2  and in relatively close proximity thereto with the circumferential ridge portion  465 RR in abutment with a radially outer surface of the ring element  420 R. This has the advantage that correct positioning of the roller element  465 R with respect to the ring element  420 R may be made in a more reliable and convenient manner, reducing the risk that a groove or recess  425  formed in the radially outer surface of the ring element  420 R is formed at an undesirable location with respect to a length LR of the ring element  420 R. In the present embodiment, the circumferential ridge portion  465 RR of the roller element  460 R is located substantially centrally between opposed major faces of the roller element  460 R, so that a groove or recess  425  is formed substantially equidistant between opposed edges  420 Re of the ring element  420 R. Other positions of the ridge portion  465 RR may be useful in some embodiments, such as substantially at one axial end of the circumferential face  465 R. In some embodiments a roller element  465 R may be provided with a plurality of ridge portions. A roller element  465 R provided with a plurality of ridge portions  465 RR may be used to form a plurality of grooves  425  in a ring element  120 R,  130 R enabling two or more ring elements to be joined to that ring element. 
         [0232]    In use, the ring element  420 R is positioned between the first and second bearing portions  462 B 1 ,  462 B 2  and held securely therebetween. The position of the carriage portion  465 C relative to the carriage support portion  465 CS (and therefore the ring element  420 R) is then adjusted by means of the screw adjuster  465 CA to cause the roller element  465 R to move towards the ring element  420 R until the circumferential face  465 RF of the roller element  465 R is in abutment with the radially outer circumferential face  420 RF of the ring element  420 R. In this position, lateral radial faces  465 RL of the roller element  465 R directly face opposed faces  462 B 1  L,  462 B 2 L of the first and second bearing portions  462 B 1 ,  462 B 2  respectively. In the embodiment shown in  FIG. 6  and  FIG. 7 , a gap between the lateral radial faces  465 RL of the roller element  465 R and opposed faces  462 B 1 L,  462 B 2 L of the first and second bearing portions  462 B 1 ,  462 B 2  is approximately 0.1 mm although other values are also useful in some embodiments. 
         [0233]    In the embodiment illustrated in  FIG. 6  and  FIG. 7  the roller element  465 R has a diameter of 25 mm and a length LRL of substantially 7 mm although other values may be useful in some alternative embodiments. A length LRR of the ridge portion  465 RR of the roller element  465 R is substantially 3 mm in the present embodiment, with the ridge portion  465 RR being provided substantially midway between lateral faces  465 RL of the roller element  465 R. Again, other lengths and relative positions of the ridge portion  465 RR may be useful in some embodiments. A plurality of ridge portions  465 RR may be provided in some embodiments. 
         [0234]    The ridge portion  465 RR is arranged to protrude a radial distance HR of 2 mm beyond the portion of the circumferential face  465 RF either side of the ridge portion  465 RR. Other values are also useful in some embodiments. 
         [0235]    The first and second bearing portions  462 B 1 ,  462 B 2  are each of diameter 50 mm in the present embodiment, in which the ring element  420 R is formed to be suitable for wearing around a finger. The ring element  420 R shown in  FIG. 6  and  FIG. 7  (not to scale) has an inner diameter of 9 mm and an outer diameter of 16 mm although in some embodiments other values may be useful. In the case of the formation of a bangle to be worn around a wrist, the inside diameter of the element  420 R may be around 16 mm and the outer diameter may be around 22 mm. Again, other sizes may be useful in some embodiments. The diameters of the first and second bearing portions  462 B 1 ,  462 B 2  may be selected accordingly. 
         [0236]    It is to be understood that other values are useful in some embodiments. In particular, it is to be understood that the relative diameters of the roller element  465 R and first and second bearing portions  462 B 1 ,  462 B 2  may be of any suitable diameter to enable gripping therebetween of a ring element  420 R of the required size and the forming of one or more grooves  425  therein by means of the roller element  465 R. 
         [0237]    In some embodiments, during rolling of the ring element  420 R to form the groove therein the ring element  420 R may expand in diameter due to displacement of material during rolling. Accordingly, lateral movement of the ring element  420 R may occur due to pressure applied by the roller element  465 R since the ring element  420 R may remain gripped between and in contact with the shaft portion  462 S and roller element  465 R during the rolling operation. Accordingly, the first and second bearing portions  462 B 1 ,  462 B 2  may be sized to accommodate such movement during groove formation. In use the roller element  465 R is urged against the ring element  420 R with sufficient pressure to cause grooving when the roller element  465 R rolls around the ring element  420 R. The carriage support portion  465 CS is then caused to rotate about the base portion  462  by manipulation of the handle portion  466 , causing the roller element  465 R to travel in a corresponding manner around the ring element  420 R. The roller element  465 R rotates about axle  465 A as the roller element  465 R describes a circular path about the axis A as the carriage support portion  465 CS is caused to rotate about the base portion  462 . By controlling the amount of pressure between the roller element  465 R and ring element  420 R, a groove  425  of suitable depth may be formed in the ring element  420 R. 
         [0238]    In some methods of use, the amount of pressure between the roller element  465 R and the ring element  420 R is increased in steps, with the roller element  465 R typically being caused to describe one or more revolutions of the base portion  462  between respective increases in the amount of pressure applied, until a groove  425  of sufficient depth is formed in the ring element  420 R. In some alternative embodiments the amount of pressure between the roller element  465 R and ring element  420 R may be increased in a substantially continuous, gradual manner as the roller element  465 R revolves around the ring element  420 R. Other arrangements may be useful in some embodiments. 
         [0239]    As will be apparent from the above description, the apparatus  460  shown in  FIG. 8  is a manually operated apparatus. It is to be understood that in some alternative embodiments one or more actuators such as one or more electric motors may be provided for causing rotation of the carriage support portion  465 CS about the base portion  462 . Similarly, in some embodiments translation of the roller element  465 R towards and away from the ring element  420 R may be driven by means of one or more actuators, such as one or more electric motors. For example, in some embodiments one or more motors may be provided for driving screw adjuster  465 CA. 
         [0240]    In some embodiments the roller element  465 R may itself be arranged to be driven by one or more actuators such as an electric motor, in addition to or instead of the carriage support portion  465 CS. In some embodiments, the ring element  420 R may be rotated with respect to the base portion  462  instead of the carriage support portion  465 CS, the carriage support remaining in a substantially fixed position relative to the base portion  462 . For example, in some embodiments the ring element  420 R may be rotated by rotation of the shaft portion  462 S. In some embodiments the first and second bearing portions  462 B 1 ,  462 B 2  may be arranged for rotation about the shaft portion  462 S thereby to cause rotation of the ring element  420 R relative to the base portion  462 , the bearing portions  462 B 1 ,  462 B 2  not being tapped and screwed to the shaft portion  462 S. Accordingly in some embodiments the first and second bearing portions  462 B 1 ,  462 B 2  may be arranged to be rotate about the shaft portion  462 S with the ring element  420 R gripped therebetween, thereby causing rotation of the ring element  420 R and facilitating formation of the groove  425 . 
         [0241]    It is to be understood that the apparatus  460  illustrated in  FIG. 6  and variations thereof described herein may have a number of advantages. For example, it is noted that the first and second bearing portions  462 B 1 ,  462 B 2  are arranged to abut the side edges  420 Re of the ring element  420 R and constrain axial expansion of the ring element  420 R in the direction of cylinder axis A. This feature has the advantage that the amount of post-fabrication finishing of the ring element  420 R that may be required may be reduced relative to embodiments in which such expansion is not constrained. The present inventors have found that the side edges  420 Re of the ring element  420 R can develop unsightly markings such as steps unless lateral expansion is constrained across substantially the entire radial thickness of the side edges  420 Re, as in the illustrated embodiment of  FIG. 8 . 
         [0242]    Furthermore, the radial thickness of the ring element  420 R before the groove  425  is formed therein may be reduced in some embodiments. This may be at least in part because the prevention of axial expansion of the ring element  420 R in a direction parallel to the cylinder axis A may reduce the amount by which the radial thickness of the ring element  420 R in the region of the groove  425  decreases during the process of forming the groove  425 . 
         [0243]    It is to be understood that forming the roller element  465 R to have a length LRL corresponding substantially to the length LR of the ring element  420 R, and causing the circumferential face  465 C of the roller element  465 R to be extend substantially from one bearing element  462 B 1  to the other  462 B 2  during rolling such that axial movement of the roller element  465 R in a direction parallel to axis A is constrained, has the advantage that a precision with which a groove may be formed at a required location between opposed circumferential edges of a ring element  420 R may be enhanced. 
         [0244]      FIG. 10  illustrates a method of fabricating an article according to a further embodiment of the present invention. In the embodiment shown the article is also in the form of a double ring. 
         [0245]    In the embodiment of  FIG. 10 , a first blank  300  is formed by pressing from a sheet of precious metal. The blank  300  is substantially in the form of a washer-shaped element. That is, the blank  300  is in the form of a substantially circular disc  300  with a substantially circular aperture  302  formed therein substantially coaxial with a rotational centre of the disc  300 . In some embodiments the blank  300  is formed by a one or two-step pressing operation. In a one-step operation, a disc  300  is pressed from a sheet of material and, substantially simultaneously, a second disc, coaxial with the first disc  300 , is pressed from the first disc  300  to form the aperture  300 A in the first disc  300 . In a two-step operation, a disc  300  not having an aperture  300 A therein is pressed from the sheet. Subsequently, the aperture  300 A is formed in the disc  300  by pressing a second disc therefrom, substantially coaxial therewith. 
         [0246]    It is to be understood that other methods of forming the blank  300  may be useful in some embodiments, such as by drilling, casting or any other suitable method. 
         [0247]    After forming the blank  300 , a substantially circular groove or recess  325  is formed in the blank  300  substantially coaxial with a centre of rotation thereof. In the present embodiment the groove  325  is also formed by pressing. Other methods of forming the groove  325  are also useful, for example by cutting, e.g. by means of a lathe, by rolling or any other suitable means for forming a groove. In the present embodiment the groove  325  is in the form of a substantially flat bottomed, parallel-sided channel which may also be described as having a shape in the form of a substantially square U-shaped channel. 
         [0248]    Once the groove  325  has been formed, a second blank  330  is inserted into the groove  325  to form a blank assembly  300 A as shown in  FIG. 10( a ) . The second blank  330  is shaped and sized in a complementary manner to the groove  325  such that a radial width w of the groove is greater than or substantially equal to the radial width of the second blank  330 . In the present embodiment, the second blank  330  is soldered to the first blank  300  to retain the second blank  330  in the groove formed in the first blank  300 . In some alternative embodiments the second blank  330  may be joined to the first blank  300  by means of a fusion process without the use of an intermediate joining material such as a solder or brazing material. 
         [0249]    The assembly  300 A is then subject to a coning operation in a similar manner to the blank  100  illustrated in  FIG. 1 . The assembly  300 A is thus transformed through an intermediate frusto-conical shaped structure as shown in  FIG. 10( b )  to a substantially tubular structure  300 T as shown in  FIG. 10( c ) . The tubular structure  300 T may be considered to be composed of a first ring element  320 R (formed from blank  300 ) having a second ring element  330 R (formed from second blank  330 ) embedded in an outer circumferential surface thereof. The tubular structure  300 T is then subject to a drawing operation in which the structure is drawn to ensure that a wall thickness and a diameter of the structure is substantially uniform along a length LR thereof. 
         [0250]    It is to be understood that in the embodiments described herein, the grooves  125 ,  225 ,  325  and second elements  130 R,  231  R,  232 R,  330 R may be formed to be of any desirable shape. Thus the second ring elements may have a corrugated shape, a helical or other curved shape, or any other suitable shape. 
         [0251]      FIG. 11( a )  shows an example of a blank assembly  500 A according to a further embodiment of the present invention. Like features of the embodiment of  FIG. 11  to those of the embodiment of  FIG. 10  are shown with like reference signs incremented by  200 . In the embodiment of  FIG. 10( a )  a second blank  530  in the form of a substantially flat, corrugated or zig-zag shaped element has been formed and inserted into a correspondingly shaped recess formed in a major face of a first blank  500 . The first and second blanks have been fused together by heating to a sufficiently high temperature for a sufficiently long period.  FIG. 10( b )  shows the assembly  400 A following the coning operation to form tubular structure  400 T in the form of a double ring  500 T having first and second ring elements  420 R,  430 R, the second ring element  430 R being inset in the first  420 R. 
         [0252]      FIG. 12( a )  shows a tubular structure  600 T in the form of a double ring according to a further embodiment of the present invention. Like features of the embodiment of  FIG. 12( a )  to those of the embodiment of  FIG. 11  are shown with like reference signs incremented by  100 . The tubular structure  600 T has been formed by coning a blank assembly to form a structure in which the second ring element  630 R is of a meandering form in a circumferential direction, being curved or softly zig-zag shaped rather than relatively sharply zig-zag shaped as in the embodiment of  FIG. 11 . 
         [0253]      FIG. 12( b )  shows a blank assembly  700 A according to an embodiment of the invention and  FIG. 10( c )  shows a tubular structure  700 T formed by coning the assembly  700 A. Like features of the embodiment of  FIG. 12( b ) and ( c )  to those of the embodiment of  FIG. 10  are shown with like reference signs incremented by  400 . 
         [0254]    The blank assembly  700 A includes a first blank  700  and a second blank  730 . The first blank  700  is also in the form of an open annular disc, i.e. a disc having a substantially circular, concentric aperture formed therein. 
         [0255]    It is to be understood that in some alternative embodiments the aperture may not be concentric with the centre of rotation of the disc forming the first blank  700 . 
         [0256]    In the embodiment of  FIG. 12( b )  a spiral-shaped groove or channel  725  has been formed in a major face of the first blank  700 , substantially coaxial with a centre of circular symmetry of the first blank  700  prior to groove formation. A second blank  730  in the form of a spiral-shaped element  730  of corresponding, complementary shape to channel  725  has been fused into the channel  725 . 
         [0257]      FIG. 12( c )  shows the blank assembly  700 A following the coning operation to form the tubular structure  700 T. It can be seen that the spiral-shaped second blank  730  has deformed to form a substantially helical-shaped element  730 . The second blank  730  may be described as a ring element  730  since it has a substantially circular form when viewed along a cylinder axis of the tubular structure  600 T. 
         [0258]    It is to be understood that, in respect of any of the embodiments of  FIGS. 10 to 12 , the dimensions of the channel (such as channel  725 ) and second blank (such as second blank  730 ) may be varied along a length thereof so as to obtain a second element  730 , following the coning operation, that has a desired shape and appearance. In other words, the radial width RW and depth of the channel  725  and second blank  730  may be varied to compensate for distortion of the channel  625  and second blank  630  during the coning operation. 
         [0259]    For example, the radial width RW and depth as a function of radial coordinate (R,  0 ), such as radial width RW of the channel  725  and second blank  730 , and depth of the channel  725  and second blank  730 , may be varied to compensate for distortion during the coning operation. 
         [0260]    It is to be understood that computational methods may be employed to calculate the required radial width RW and depth of the channel  725  and second blank  730  for forming the blank assembly  700 A based on data describing the required form of the final tubular structure  700 T. Finite element methods or the like may be employed in order to perform this calculation. 
         [0261]    In the embodiment shown in  FIG. 10 , instead of a single second ring element  330 R that is in addition to the first ring element  320 R, two or more second ring elements may be provided. In some alternative embodiments one or more letters, indicia or other elements may be embedded in corresponding grooves or recesses formed in the first blank  300 . The elements may be shaped such that following the coning operation (and/or a subsequent drawing operation if required) the elements have a desired shape. Thus, the elements as inserted into the grooves or recesses may be of a shape (and optionally a thickness) that is distorted relative to the final desired shape (and optionally thickness) such that following the coning operation and/or drawing operation the elements have the desired visual appearance and thickness. 
         [0262]    It is to be understood that a trimming and/or polishing operation may be performed following the coning or drawing operation, to reduce a thickness of the second ring element  130 R,  231  R,  232 R,  330 R if desired. 
         [0263]    Some embodiments of the present invention provide a method of forming an article such as a finger ring, bracelet, bangle or other wrist or arm-worn article that enables the article to be formed with a reduced amount of wastage and/or a reduced amount of starting material. 
         [0264]    Some embodiments enable a ring or bracelet or bangle or the like to be formed having a required size with each of the ring elements fitting sufficiently tightly whilst avoiding distortion or breakage. 
         [0265]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. 
         [0266]    Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0267]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.