WO1995017112A1

WO1995017112A1 - Finger rings

Info

Publication number: WO1995017112A1
Application number: PCT/GB1994/002707
Authority: WO
Inventors: Francis Victor Jenks; Stanley Robert Green
Original assignee: Birmingham Manufacturing Jewellers Limited
Priority date: 1993-12-21
Filing date: 1994-12-12
Publication date: 1995-06-29
Also published as: AU1197095A; GB9326109D0; ZA949969B

Abstract

A finger ring is made by a method involving the steps of drawing precious metal through a die (8) and winding the length directly onto a former (10), to produce a helix (4). Individual ring-shaped pieces are then cut from the helix and the ends of each piece are secured together, either directly or through the intermediary of a head, without any significant quantity of heat being input to the metal subsequent to the drawing operation. In this way superior strength characteristics are obtained, rendering the ring less liable to damage by undesired deformation.

Description

Title: Finger rings

Description of Invention

Finger rings of precious metal (e.g. silver or gold) are conventionally cast in a desired size and shape, or individually sized after casting. Casting of precious materials such as gold produces a relatively open crystalline structure which requires considerable attention to be paid to polishing and finishing.

Alternatively wire may be drawn through a die, subsequent to which conventionally the wire is annealed prior to being loosely coiled for transportation. Subsequently selected lengths of wire are formed into shape.

Difficulties are encountered in attempting to satisfy the market which exists for less expensive rings of precious metal. For example, simply reducing the quantity of metal within the ring (i.e. reducing the cross sectional area) reduces the strength of the ring, making it prone to collapse under load, and making it look skimpy. Attempting to give the appearance of having a greater metal content by flattening the cross section of the ring reduces the strength further.

According to this invention there is provided a finger ring comprising a shank afforded by a length of metal having been drawn through a die and subsequently formed into a circle, the metal not being subjected to any significant heat treatment operation subsequent to being drawn.

By drawing the metal through a die causing a predetermined amount of deformation it is possible to obtain metal, particularly precious metal, which has a much higher density crystalline structure, and which may be afforded with a very highly polished surface finish by virtue of the drawing process, and thus the requirement for extensive polishing subsequent to production is eliminated.

By omitting any subsequent heat treatment operation (such as annealing) the strength of the shank when coiled into a ring is significantly greater than a ring manufactured by a conventional technique. This allows a ring to be produced which is stronger (i.e. better able to resist compressive deformation) than a ring of similar cross section which is manufactured by the conventional techniques specified above. Additionally or alternatively the cross section of the ring may be flattened somewhat from the strength-advantageous circular cross section without unduly weakening the ring.

Preferably the metal is drawn from the die onto a rotating former, such as a mandrel, having a diameter required for use.

By drawing the metal through the die direct onto a rotating former, which conveniently rotates on an axis extending generally at right angles to the direction in which metal is drawn from the die, a shank may be provided which is a desired diameter, allowing the shank to be cut or cropped from a coil wound onto the former.

However if desired the metal may be drawn into lengths, for loose coiling into bundles, or onto a former having a diameter other than required for final use, being shaped into final form, either by being wound around a mandrel or being shaped on a former by hand, subsequently.

In addition to having a dense, highly polished surface finish, the strength of the ring (capability of resisting deformation) is high, specifically significantly higher than rings produced from cast metal or metal having been subjected subsequent to drawing to an annealing operation.

Where the ring is to be utilised as a plain finger ring (i.e. unadorned by a head) the shank may be removed from the coil by a simple cut, the shank subtending an angle of a little under 360°, allowing the ends of the shank to be secured together prior to finishing.

Alternatively where the shank is to be utilised in conjunction with the head, carrying perhaps precious or semi-precious stones, the shank may be removed from the coil by cropping out a section, subtending for example an angle between 120° and 30° at the centre of rotation of the former.

In this manner, a head of a single design and size may be secured to shanks covering a range of finger sizes.

Preferably the head of the ring is provided with marking, such as hall marking. In this manner distortion of the shank as may occur on the application of such marking thereto may be avoided. Alternatively such marking may be applied to an end portion of the shank located beneath the head, where such distortion is not readily visible.

The shank may be drawn through a die so as to be of solid cross section, or may be of hollow cross section. Thus, the shank may be afforded by folding of a strip of metal as it is drawn through a die so as to provide a continuous, convex exterior surface and an internal, hollow concave surface.

According to this invention there is also provided a method of making a finger ring involving the steps: a) drawing a length of metal through a die; b) forming from said length a plurality of ring shanks, each subtending an angle of greater than 240°, and c) securing the ends of the shank together, there being no significant degree of heat input to the metal between the drawing step and the securing step.

The ends of the shank may be secured directly together, or may be secured together through the intermediary of a head, which might be set with precious or semi-precious stones. In the former case, conveniently the shank subtends an angle of 355° to 360°, in the latter case conveniently the shank subtends an angle of between 240° and 330°.

According to this invention there is also provided a method of forming a finger ring of a specific diameter in which a length of wire is drawn through a die onto a mandrel, the diameter of the mandrel being said specific diameter or marginally smaller than said specific diameter, without subsequent annealing of the wire.

Alternatively the wire may be drawn onto a tapered mandrel, and rings formed thereby may subsequently be sized.

According to this invention there is also provided a helix of precious or semi-precious wire, e.g. gold, having a diameter lying within the normal range of a finger ring. There will now be given a detailed description, to be read with reference to the accompanying drawings, of a finger ring which is a preferred embodiment of this invention, having been selected for the purposes of illustrating the invention by way of example, the method by which the finger ring having been made also being illustrative of certain aspects of the invention. In the accompanying drawings:

Figure 1 illustrates the production of a coil from which a plurality of finger ring shanks are produced;

Figure 2 is a view illustrating the securement of a head to the shank in the manufacture of the ring;

Figures 3 and 4 illustrate different cross sections of shank, as examples which may be utilised in the performance of the invention; and

Figures 5 and 6 show the results of the strength testing of rings manufactured in accordance with this invention, compared with rings manufactured by conventional processes.

Figure 1 illustrates the preparation of a coil 4 of precious metal such as gold, involving drawing of continuous length of metal through the aperture 6 of a die 8, and winding the drawn metal onto a mandrel 10 mounted for rotation about a longitudinal axis L/A extending generally at right angles to the direction in which metal is drawn through the die 6. As the metal is wound onto the mandrel 10, the mandrel or the die is moved in the longitudinal direction.

On completion of winding of a coil onto the mandrel 10, the coil is cut to provide a plurality of shank portions 12, each shank portion conveniently subtending an angle of about 300° (see Figure 2), removed material being returned for reprocessing. Used in conjunction with the shank 12 is a head 14, onto which the shank 12 may be clipped, prior to being permanently secured prior to be being finished. Conveniently the head 14 comprises, on an underside thereof a plate 16, to which hall marking may be applied, to avoid damage being caused to the high quality surface finish afforded to the shank 12 by virtue of it having been drawn through the die 8. Alternatively hall marking may be applied to an end portion of the shank beneath the head, conveniently such end portion being turned away from the centre of the ring to avoid intrusion against the wearer.

Conveniently the shank is secured to the head 14 by a point-solder technique such as that known as "aquaflame", in which a very small flame of hydrogen is burned in the presence of oxygen to produce a very localised melting of the solder.

However if desired other, heatless techniques may be used. The clearance between the inner ends of the shank 12 and the head 14 may be such as to permit a number of shanks 12 of differing diameters to be utilised with one design of head 14, allowing for the production of economies of manufacture.

The shank 12 may be drawn of solid cross section, such as is illustrated in Figures 3 and 4, or may be drawn in hollow cross section.

Figures 5 and 6 show the strength testing of rings manufactured in accordance with this invention, compared with rings manufactured by conventional techniques. All rings were of the same size, being generally D-shape in cross-section, specifically having a base dimension of 0.040" (1mm) and a height of 0.024" (0.6mm). In Figure 5, the traces are as follows:

Trace A - a cast ring having an integral setting, and subsequently annealed.

Trace B - a cast ring having an integral setting, without being annealed.

Trace C - a wire ring drawn through a die and wound onto a rotating mandrel, subsequently annealed and welded to the setting.

Trace D - a wire ring manufactured in accordance with the invention, wire of 0.045" (1.1mm) diameter being drawn down into D-shape in cross-section, having a base (chordal) dimension of 0.040" (1mm) and a height of 0.024" (0.6mm). The experiment was repeated with a second group of rings, the results being shown in Figure 6.

As will be seen, the elastic limit for the rings Dl and D2 appears to occur at a force of approximately 18N, with a compressive displacement of 0.75mm. Conversely, the elastic limit for the rings A and B occurs at a force of approximately UN, and the rings CI and C2 at approximately 8N.

The strain produced on stressing the rings within the elastic limit would be largely relaxed on removal of the load, that is the ring would spring back to its original diameter, or very close thereto. Any deformation which occurs after the elastic limit has been reached, is to be considered as plastic deformation, and hence permanent. Notwithstanding, the strength of the rings Dl and D2 can be seen to be significantly higher than the rings A, B and C significantly subsequent to the passing of the elastic limit. Thus, damage which is caused to the rings D on compressive load beyond the elastic limit will be less than that which is incurred by the rings A, B and C, allowing rectification of damage to be carried out more readily.

It is understood that the benefits of the present invention reside in the improve crystalline structure which is obtained when the precious metal is drawn through the die, such improved crystalline structure conventionally being destroyed or impaired by the processes subsequently carried out (such as annealing, or soldering with a high heat input) conveniently used in the manufacture of rings. It is believed that the benefits of the invention are obtained by the avoidance of any significant degree of heat input into the metal after it has been drawn through the die, advantageously with a reduction in cross-sectional area of the wire of at least 25%, preferably at least 35%, and advantageously in the range 40% to 50%, and preferably (but not necessarily) by winding the drawn metal onto a mandrel, preferably one representing the final desired diameter, without any significant delay in time.

Claims

1. A finger ring comprising a shank afforded by a length of metal having been drawn through a die and formed into a circle, the metal not being subjected to any significant heat treatment operation subsequent to being drawn.

2. A method of making a finger ring involving the steps: a) drawing a length of metal through a die; b) forming from said length a plurality of ring shanks, each subtending an angle of greater than 240°, and c) securing the ends of the shank together, there being no significant degree of heat input to the metal between steps a) and c).

3. The invention according to one of Claims 1 and 2 wherein the ends of the shank are secured together directly, and preferably the shank subtends an angle of between 355° and 360°.

4. The invention according to one of Claims 1 and 2 wherein the ends of the shank are secured together through the intermediary of a head, and preferably the shank subtends an angle of between 240°and 330°.

5. The invention according to any one of the preceding claims wherein the drawing operation involves a reduction in the cross-sectional area of the wire of at least 25%, preferably between 40% and 50%.

6. The invention according to any one of the preceding claims wherein the shank if D-shape in cross-section.

7. The invention according to any one of the preceding claims wherein the interior of the shank is hollow.

8. The invention according to any one of the preceding claims wherein the metal is drawn through a die and wound directly onto a mandrel having a diameter appropriate to the intended final diameter of the ring.

9. The invention according to any one of the preceding claims wherein the wire is drawn through the die onto a mandrel extending at right angles to the direction in which wire is drawn through the die, the die and the mandrel being mounted for relative orthogonal movement.

10. Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.