Knitted silver alloy fashion accessory and method of manufacture

Abstract

A knitted fiber fashion accessory and method of forming includes at least one silver alloy wire knitted in a three-dimensional structure where the silver alloy is a precipitation hardened silver alloy. The fashion accessory can include means for attaching the fashion accessory to a human body and/or a decorative element connected to the knitted fiber structure. The method includes providing a silver alloy wire having at least one alloying metal; knitting the silver alloy wire into a knitted fiber structure; and precipitation hardening the silver alloy wire to produce a precipitation hardened silver alloy wire. The precipitation hardening improves yield strength and causes a volume reduction that improves flexibility or suppleness.

Description

CLAIM OF PRIORITY

Benefit is claimed of U.S. Provisional Patent Application 60/538,480, filed Jan. 22, 2004, which is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to a knitted wire cable of sterling silver and a method of manufacturing the same for use as various fashion accessories. More particularly, the present invention relates to volumetric shrinkage of a knitted wire cable in the production of fashion accessories such as jewelry and the like.

BACKGROUND OF THE INVENTION

Silver can be a popular material choice for jewelry, and it is desirable to produce a silver chain for jewelry applications. Silver, however, has a relatively low breaking point, or relatively low yield strength (˜30 kpsi). Thus, typical silver chains include links having relatively substantial thickness. In addition, silver chain can be costly and difficult to fabricate, increasing the cost per unit length. Sterling silver has a slightly greater yield strength, but can be brittle and difficult to work into a desired shape. Chains, such as sterling silver chains, are used extensively in jewelry, such as bracelets and necklaces. Such sterling silver jewelry can be fragile, and can also have a relatively low breaking point, or relatively low yield strength (˜60 kpsi).

Precipitation hardening, also known as age hardening, can be used to harden a variety of metal alloys, but is generally considered ineffective for silver and silver alloys, such as sterling silver. Precipitation hardening typically involves a two-step heat treatment which results in enhancement of strength and hardness through formation of small uniformly dispersed particles of a second phase within a bulk metal matrix. The first step typically involves a solution heat treatment wherein an alloy is heated sufficient to form a single phase. The single phase is rapidly quenched in order to minimize formation of separate phase to form a metastable solid solution. The metastable solid is then subjected to a precipitation heat treatment step at a temperature below the first step and in which the two phases are stable. Small particles of a second phase begin to precipitate in the bulk metal matrix. The metal can then be cooled after a predetermined time. This basic process involves various additional considerations such as composition, temperatures, cooling rates, heat treatment times, i.e. transition phases and overaging, and the like.

In addition, precipitation hardening is distinct from other heat treatments used for hardening metals, such as formation of tempered martensite. For example, precipitation hardening occurs at lower temperatures and a large portion of the hardening effect occurs over time. In addition, precipitation hardening requires a number of conditions and properties of a given metal alloy to be met. As such, not all metal alloys are susceptible to precipitation hardening treatments. Numerous studies have investigated the hardening behavior of various metal alloys and are commonly represented and described in relationship to corresponding phase diagrams. For example, common criteria for precipitation hardening include an alloy composition where there is a significant, i.e. several percent, maximum solubility of one component of the alloy in another component. Further, this solubility limit can rapidly decrease with temperature reduction. Aluminum and copper alloys are the most common metal alloys which are treated using precipitation hardening. Copper-beryllium alloys are commonly precipitation hardened and formed into small springs. Other metal alloys are also known to be suitable for precipitation hardening such as titanium alloys, magnesium alloys, and some iron alloys.

For this and other reasons, the need remains for methods and materials which can improve the mechanical properties of silver and its alloys and which have improved resistance to wear and oxidation. In addition, suitable processes and materials continue to be sought for increasing available styles, mechanical properties, and appearance of silver-based jewelry.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1a is a perspective view illustrating an exemplary knitted fiber fashion accessory in accordance with an embodiment of the present invention.

FIG. 1b is a perspective view illustrating another exemplary knitted fiber fashion accessory in accordance with an embodiment of the present invention.

FIG. 2a is an enlarged, partial side view of an exemplary jacketed weave pattern of the fashion accessory of FIG. 1a in accordance with one embodiment of the present invention.

FIG. 2b is a photograph showing an enlarged, partial side view of an exemplary jacketed weave pattern of the fashion accessory of FIG. 1a in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made to exemplary embodiments and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features described herein, and additional applications of the principles of the invention as described herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. Further, before particular embodiments of the present invention are disclosed and described, it is to be understood that this invention is not limited to the particular process and materials disclosed herein as such may vary to some degree. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

Definitions

In describing and claiming the present invention, the following terminology will be used.

The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a silver alloy” includes reference to one or more of such alloys, “a wire” includes reference to one or more of such structures, and “heating” refers to one or more of such steps.

As used herein, “sterling silver” refers to a silver alloy having at least 92.5 wt % silver with the balance comprising any number of additional metals, e.g. typically primarily copper although other metals can be suitable for any given application.

As used herein, “fashion accessory” refers to any item which is wearable for purpose of aesthetics, fashion, practicality, or the like. Fashion accessories can include a wide variety of items such as, but not limited to, jewelry, clothing additions, i.e. trim, buttons, and the like, decorative coverings for items such as purses or bags, or any other known fashion accessories. Typically, the fashion accessories can include additional parts or elements in addition to the knitted fiber structure of the present invention. For example, clasps, pins, latches, decorative elements such as stones, bobs, gems, etc. can be incorporated into or attached to the knitted fiber structure to produce a commercial product.

As used herein, “amorphous” refers to a non-crystalline state of a material. Thus, an amorphous material can be entirely or at least substantially non-crystalline. Amorphous solids are typically produced by rapid cooling of a liquid material which does not allow individual atoms to form a crystalline lattice.

As used herein, “substrate” refers to a mass of material which can provide mechanical support and properties to a material.

As used herein, “woven” and “knitted” refers to any network of a single or multiple metal fibers or wires. Thus, woven, knitted, interlinked, braided, and other similar structures are considered within the scope of the present invention. A plurality of woven wires can be alternately overlapped. One or more wires can be knitted, usually by forming loops.

As used herein, “fibers” and “wires” may be used interchangeably and refer to any elongated length of metal. Such fibers can have any practical cross-section suitable for the intended use and may include, but is not limited to, circular, square, rectangular, flat (ribbon fibers), and the like.

As used herein, “suppleness” refers to the flexibility, pliability, and perceived softness of a knitted structure. It will be understood that this term is used herein in a qualitative manner which is relative to a non-precipitation hardened state of the material referred to having the same knitted structure and elemental composition.

As used herein, “kpsi” is a unit referring to thousands of pounds per square inch.

As used herein, “substantially free of” refers to the lack of meaningful quantities of an identified element or material in a composition. Particularly, elements that are identified as being “substantially free of” are either completely absent from the composition, or contain amounts which are small enough so as to have no measurable effect on the identified properties of the composition.

Concentrations, dimensions, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a size range of about 0.1 mm to about 20 mm should be interpreted to include not only the explicitly recited limits of 0.1 mm and about 20 mm, but also to include individual sizes such as 2.5 mm, 3 mm, 14.5 mm, and sub-ranges such as 1 mm to 5 mm, 2 mm to 10 mm, etc.

Flexible, Knitted, Silver Alloy Cable

In accordance with one aspect of the present invention, fashion accessories can be formed from a knitted flexible cable of silver alloy, such as sterling silver, and can have greater strength or breaking point than traditional chains, while having similar flexibility. The silver alloy wire can be knitted in a three-dimensional structure as described in more detail below. The fashion accessories can include jewelry, decorative coverings, clothing additions, or any other fashion accessory configuration. Non-limiting examples of jewelry can include chains, bracelets, necklaces, earrings, rings, keyrings, keychains, watches, pins, fobs, broaches, tassels, tiepins, cufflinks, pendants, etc. The jewelry can include a plurality of decorative elements, such as beads, gems, balls or spheres, strung together along the knit cable of the present invention. For example, the knit cable can extend through apertures or bores in the balls or spheres to connect the balls or spheres together.

As explained in greater detail below, the cable can be formed by one or more wires of a silver alloy, knitted together to form a cylindrical-shaped cable. Initially, the cable can be relatively stiff. The knitted cable can be age hardened, or precipitation hardened. Unexpectedly, the knitted cable, or wire(s) thereof, can experience a volumetric shrinkage that results in the knitted cable having greater flexibility, as well as greater strength.

Precipitation Hardened Silver Alloys

In accordance with one aspect of the present invention, a silver alloy can be precipitation hardened. A wide range of silver alloys can be suitable for use in the present invention which include at least one alloying metal. Non-limiting examples of suitable alloying metals may include copper, germanium, aluminum, magnesium, lead, antimony, beryllium, boron, and combinations thereof. In another aspect, the silver alloy can be a sterling silver, i.e. a silver-copper alloy. As such, sterling silver alloys of the present invention can include additional alloying metals such as, but not limited to, germanium, aluminum, magnesium, lead, antimony, beryllium, boron, and combinations thereof. Sterling silver alloys are particularly suited to applications in jewelry and the like since silver alloys having less silver require special marking and are not generally considered as valuable. However, other more mechanical fashion accessory applications such as clothing additions, coverings, supplemental reinforcement, and the like can benefit from the use of non-sterling silver alloys. Similarly, sterling silver including copper and at least one additional alloying metal can be used. The additional alloying metal such as, but not limited to, germanium, aluminum, magnesium, lead, antimony, beryllium, boron, and combinations thereof can be used. In one aspect, the silver content can be at least about 77 wt %. In some embodiments, sterling silver alloys having at least two additional alloying metals can provide desirable mechanical and aesthetic properties to the knitted fiber structures of the present invention.

One specific class of silver alloys which has shown particular benefit from the methods of the present invention includes silver alloys which consist essentially of silver, copper, germanium, and boron. In such silver-germanium alloys the germanium content can be from about 0.4 wt % to about 7 wt % and preferably from about 0.5 wt % to about 3 wt %. One specific example of a suitable silver-germanium alloy has a composition of about 92.5 wt % silver, 6.3 wt % copper, 1.2 wt % germanium, and with a small amount, e.g., 0.002 wt %, of boron as a grain enhancer. It is thought that the second phase which is precipitated during precipitation hardening includes germanium and copper. As discussed in more detail below, this combination of alloying metals exhibits particularly beneficial mechanical properties such as increased strength, improved flexibility, moderate volume reduction, and reduced oxidation, i.e. reduced tarnishing and fire-staining. A more detailed discussion of one class of suitable silver alloys can be found in U.S. Pat. No. 6,168,071, which is hereby incorporated by reference in its entirety.

The method of precipitation hardening in accordance with the present invention is explained in more detail below. However, the immediately following discussion includes properties and applications of the precipitation hardened silver alloys. It is known that traditional silver alloys are not subjected to and/or are not capable of precipitation hardening processes. However, precipitation hardenable silver alloys can have increased yield strengths, increased hardness, volume reduction, and the like which significantly improve the mechanical properties of these alloys. As a result, a number of applications and uses for such alloys become much more commercially valuable. For example, the precipitation hardened silver alloys of the present invention typically have a yield strength of from about 1.5 to about 2.5 times that of an untreated silver alloy having the same elemental composition, but can be made as a knitted structure softer and more supple than sterling silver. For example, the precipitation hardened Ag—Cu—Ge—B alloys described above have a yield strength about 1.75 to 2 times that of standard sterling silver (Ag-7.5Cu). Specifically, this precipitation hardened silver alloy has a yield strength of about 105 to 120 kpsi. As a useful point of reference, note that although not frequently used because of its softness, pure silver has a yield strength of about 30 kpsi. Similarly, standard sterling silver has a yield strength of about 60 kpsi.

Further, the precipitation hardened silver alloys of the present invention can have a greater hardness than that of an untreated silver alloy having the same elemental composition. Further, silver alloys containing small amounts (i.e. 0.5 to 3 wt %) of germanium experience a reduction in conductivity of almost half that of pure silver and standard sterling silver alloys.

One particularly interesting property of the precipitation hardened silver alloys of the present invention is a small degree of volume shrinkage during the hardening treatment. Specifically, the precipitation hardened silver alloys of the present invention can have a volumetric shrinkage of about 0.5% that of the silver alloy without precipitation hardening. The actual volumetric shrinkage can depend somewhat on the specific alloy composition; however, as a general matter, volumetric shrinkage from about 0.3% to about 0.7% can be achieved. Further, due to precipitation hardening, a knitted three-dimensional structure (described below) can be increased in flexibility through precipitation hardening in accordance with the present invention. This is at least partially due to the volume shrinkage during heat treatments. Thus, an improved structure can be formed which exhibits both high yield strengths and increased flexibility over the un-treated alloy.

Structures of Silver Alloy

The silver alloys of the present invention can be formed into a wide variety of knitted structures. It is known that silver alloys tend to not be suitable for typical knitting processes. Traditional silver alloys are too rigid or stiff to withstand the knitting process. However, it has now been recognized that some silver alloys can be knitted and precipitation hardened to achieve expanded options in forming jewelry and other fashion accessories. Suitable structures can include, but are not limited to, wires, rods, sheets, plates, coatings, and the like. In one embodiment of the present invention, the silver alloy can be formed into a wire. The wire can have any useful cross-section, e.g., circular, square, rectangular, and even flat, i.e. ribbon wire. Typically, the wire can have a maximum cross-sectional dimension of about 0.1 inches. In one aspect of the present invention, the wire can have a maximum cross-sectional diameter of from about 0.0008 to about 0.08 inches and preferably from about 0.001 inches to about 0.01 inches, although other dimensions can be used depending on the intended application. For example, wire having a diameter of approximately 0.005 inches has proven to have good strength, knittability, and appearance. The silver alloy wires can also have a substantially homogenous composition throughout the wire. This homogenous composition provides for ease of manufacture and eliminates any marking requirements for plated or layered materials.

In accordance with another aspect of the present invention, at least one silver alloy wire can be knitted to produce a knitted fiber structure. The knitted fiber structure can be a three-dimensional structure. Although the term three-dimensional is used, it is to be understood that many knit or weave patterns result in a nearly planar structure; however, such structures involve individual wires, or section of wire, which generally cross over one another in a repeating under-over pattern in three dimensions. Such knitting or weaving is well known in the art and can include any number of knit or weave patterns and products. Several non-limiting examples of three-dimensional knitted structures can include weave, braid, knitted, and knotted. Additionally, specific knit or weave patterns can include, but are not limited to, plain, twill, reverse plain, plain and twill dutch weave, interlocked loops, plain knit weave, and the like. The knitted fiber structure can be knitted as a single cable, jacket cable, multi-layered cable, interwoven braids or cables, knots, crochet-style patterns, or the like.

The knitted fiber structure can be accomplished using one or more knit heads with a plurality of needles that form loops with the wire. Thus, one or more wires can be drawn into the knit head; the needles can form loops or interlocking loops with the wire; and the knitted cable can exit the knit head. In the case of a jacket cable or multi-layered cable, a first cable or core can be knitted by a first knit head, and pulled through a second knit head that can knit a second cable or jacket about the core. As discussed in greater detail below, a sacrificial thread, such as a cotton thread, can be knit along with the wire, and subsequently removed, such as with sulfuric acid. The cotton thread(s) have been found to allow faster knit speeds and more needles.

FIGS. 2a and b illustrate a three-dimensional structure, indicated generally at 10, formed of one or more silver alloy wires 11 knitted to form the three-dimensional structure. The three-dimensional structure shown is an interlocked loop knit pattern formed in a jacket cable 12. In this embodiment, the jacket cable is a double-layered cable having an inner core knit structure 13 and an outer jacket knit structure 14. In forming this type of knitted structure, a four-needle knit head can be used. First, the inner core 13 can be formed by knitting a set of two wires (although this is not required). A cross-section (not shown) of the inner core would cut across four loops in double-wire for a total of sixteen wires. The outer jacket 14 can then be formed in a similar manner with a slightly larger knit diameter such that the two layers are distinct. A cross-section (not shown) of the outer jacket would cut across four loops and eight wire sections. Thus, a cross-section of the jacket cable 12 would cut across 24 wires. The jacket cable 12 illustrated can include a single silver alloy wire in each layer, if desired. The jacket cable 12 described above provides an aesthetically pleasing structure. The outer jacket 14 forms relatively large loops through which the inner core 13 can be viewed. The double wires of the inner core and the single wire of the outer jacket, and the loops formed in both, provide numerous surfaces at numerous angles which shine or reflect light to create a pleasing glittering structure.

Similarly, a sheet knitted structure of silver alloy wire can be produced. This knit pattern is a similar weave to that shown in FIGS. 2a and b, however, the structure is a sheet. This type of fashion accessory can be used in a variety of settings, such as purse coverings, sashes, vests, necklaces, and the like. A braid knitted structure can also be produced. This knitted structure is similar to the knit or weave pattern used in coaxial cables. Such knit or woven structures can have a variety of knit or weave patterns having any number of mesh sizes and opening sizes. In one aspect, the knit structure is relatively tight leaving small to substantially no spaces between adjacent wires. In another aspect, the knit structure can leave openings between adjacent wires sufficient to produce mesh sizes of from about 2 to about 500 mesh, depending on the intended application. For example, the mesh size can be a function of desired strength, aesthetics, sieving or filtering size, economics, or the like.

In yet another aspect, the knitted fiber structure can be formed into a structure such as a hollow tube or cable, non-hollow tube or cable, ribbon, sheet, and combinations thereof. Further, in an alternative embodiment, the knitted structure can be a composite or layered knit or woven structure, e.g., concentric layers of woven mesh such as a coaxial cable. In such embodiments, the layers may have the same or different knit or weave patterns. Alternatively, complex thicker three-dimensional structures can be knit or woven to produce a structure having significant width, length and height dimensions. Such structures can have a single knit pattern or multiple knit patterns. Additionally, the knit pattern can be ordered as described above or random such as in steel wool.

The knitted fiber structures of the present invention can include formation of long knitted cables of various thicknesses. Several non-limiting examples of suitable products that can benefit from such knitted fibers include replacement of chains in jewelry with knitted cables having comparable flexibility. The precipitation hardened silver alloys formed into a knitted structure can have a yield strength and tensile strength greater than a typical chain of the same dimensions.

In another aspect of the present invention, the knitted fiber structure can be substantially free of joints or welds. In accordance with one aspect, the structures of the present invention do not require joining methods such as welding, soldering, brazing, or other similar techniques. Specifically, the additional steps of joining separate sections of metal are not required in order to produce a useful structure. A knitted fiber structure can be formed merely by knitting a predetermined structure to produce a usable product. However, the knitted structures of the present invention can be joined to other structures in order to produce a final commercial product.

In yet another aspect of the present invention, the step of knitting further includes providing a sacrificial thread placed substantially parallel and adjacent to the silver alloy wire during knitting. The sacrificial thread can be formed of any suitable material which can be removed after the knitted structure is formed. For example, suitable materials for the sacrificial thread can include, but are certainly not limited to, cotton, polymer, readily soluble metal, or the like. One of the advantages of the sacrificial thread is to provide a spacer to control spacing in the knitted fiber structure. Thus, the thickness of the sacrificial thread can be used as one way to increase or decrease the volume of space between adjacent portions of the knitted wire. Typically, the sacrificial thread can have a diameter which is about the same as the wire, or a diameter of approximately 0.005 inches. In one aspect of the present invention, the sacrificial thread can have a diameter larger than, or less than, the diameter of the wire, such as from about 0.0008 to about 0.08 inches and preferably from about 0.001 inches to about 0.01 inches, although other dimensions can be used depending on the intended application. The dimensions of the sacrificial thread and silver alloy can be at least partially governed by the knitting machinery and the desired appearance of the final product.

Additionally, the sacrificial thread can act as a buffer to help reduce tension during knitting and smooth the knitting process. This has the added benefit of reducing breakage of the silver alloy wire during manipulation by the knitting machinery. It has been found that the use of a sacrificial thread increases knitting speed, and allows more needles to be used. Subsequent to knitting and formation of the knitted structure, the sacrificial thread can be removed. Removal of the sacrificial thread can be accomplished by any convenient process such as dissolving in acid, burning, or the like. For example, sulfuric acid can be used to remove a cotton thread.

The fashion accessories of the present invention can most often be configured as jewelry or other accessories meant to be worn by a person. Most often this requires that the knitted structure further include a means for attaching the fashion accessory to a human body. A number of mechanisms can be used to provide a means for attaching the fashion accessory to the human body. Attachment to the human body is intended to refer to direct attachment such as with an earring via a clasp, or pin and retainer mechanism, as well as clasps, latches or loops which allow for securing the item such as a necklace, bracelet, or the like to a person. For example, suitable means for attaching can include a latch, pin, looped configuration, finding such as a clasp, pin and backing, etc., or any other suitable mechanism. FIG. 1a illustrates a necklace fashion accessory 20 in accordance with the present invention. The necklace shown has a jacket knitted structure 12 as in FIGS. 2a and b. As shown in FIG. 1a, the necklace fashion accessory 20 includes the jacket knitted structure 12 formed in a loop 22 with a clasp 24 welded or soldered to the ends of the knitted structure. Additionally, the necklace includes a second jacket knitted structure 26 having bobs 28 at each end. Further, rings or beads 30 are placed as shown to maintain the desired shape and for a pleasant appearance. FIG. 1b illustrates a pair of earrings fashion accessories 40 in accordance with the present invention. The earrings have a jacket knitted structure 12 as in FIGS. 2a and b. As shown in FIG. 1b, each earrings fashion accessory 40 includes a pin 42 and a retainer mechanism 44.

As a practical matter, the knitted fiber structure of the present invention can further include one or more decorative elements connected thereto. Decorative elements such as bobs, balls, rings, precious stones, gems, settings, brooches, emblems, pendants, and any other decorative item can be connected to the knitted fiber structure for purpose of added value and/or consumer appeal.

Methods of Precipitation Hardening and Production

A method of forming a precipitation hardened silver alloy can include providing a silver alloy having at least one alloying metal such as those discussed previously. The silver alloys discussed herein can be formed into the structures discussed either before or after precipitation hardening. Generally, the silver alloys can be annealed at a relatively high temperature to produce a softened silver alloy which can then be cold worked into a desired shape. The method can further include cold working steps either before or after the precipitation hardening step. Preferably, cold working is performed prior to precipitation hardening in order to preserve the mechanical and flexible properties; however in some case it can be desirable to cold work the precipitation hardened metal alloy to produce a final commercial product. For example, the step of providing the silver alloy can include a forming step to achieve a given shape. A wire having a given cross-section can be formed using standard extrusion techniques or other wire drawing methods known to those skilled in the art. Frequently, such cold working can cause the silver alloy to become excessively hard. In such cases, one can reheat the silver at a high temperature to soften the metal. Many of the silver alloy wires of the present invention can require multiple passes through a wire drawing die to achieve a desired diameter. For example, a silver alloy wire having a 0.115 inch diameter can be cold-worked to a diameter of about 0.005 inches after many annealings and passes through wire drawing dies. Further, the degree of cold working and annealing can be adjusted to achieve a wire strength which can withstand the knitting process while also maintaining sufficient flexibility. This balance of flexibility and strength for allowing knitting can be identified based on experience and practice of the present invention.

Regardless of the shaping and cold working steps used, the silver alloy can be heated to a first annealing temperature sufficient to produce a substantially single phase solution. The step of heating to a first temperature can include heating to a temperature from about 500° C. to about 1000° C., although other temperatures may be suitable for a particular alloy composition. This first temperature can be maintained for a time sufficient to anneal and soften the silver alloy. The time necessary can depend on the temperature, however is generally from about 1 hour to about three hours. Frequently, due to overworking, the silver alloy can be re-annealed to soften the wire for continued working to produce a wire which is suitable in size and flexibility for knitting. For example, currently preferred annealing and softening temperatures can range from about 560° C. to about 580° C. for a time from about 40 to about 50 minutes.

The single phase solution can then be air cooled to produce a solution treated silver alloy. Alternatively, the single phase solution can be quenched. In this state, the silver alloy can contain substantially only a single phase, although trace amounts of a separate phase are common. Typically, this solid single phase is amorphous and metastable, i.e. thus often exhibiting poor mechanical properties. The solution treated silver alloy can then be heated a second time to a second temperature less than the first temperature. As a general guideline, the second temperature can vary from about 180° C. to about 500° C., and in some case from about 200° C. to about 300° C. and preferably about 232° C., although the specific temperatures can vary depending on the composition of the alloy. The second temperature can be any temperature sufficient to allow a second phase to precipitate to produce a precipitation hardened silver alloy. In an exemplary embodiment, the second temperature can be from about 250° C. to about 350° C. and preferably about 300° C. The second temperature can be maintained for from about 20 minutes to about 60 minutes and preferably about 30 minutes. Temperatures and times outside the above ranges can be used. Specifically, the precipitation hardening of the present invention is typically somewhat less sensitive to temperature and time than typical precipitation hardening heat treatments. For example, the silver alloys of the present invention are less susceptible to overaging during the precipitation heat treatment step than typical aluminum, copper, titanium and iron alloys. In one aspect, the steps of heating can be each performed in a non-oxidative environment.

Although not specifically required, it is most often preferred to cold work an annealed silver alloy wire into the desired diameter and stiffness. Subsequently, the cold worked silver alloy wire can be knitted into the three-dimensional structure. The knitted structure can then be precipitation hardened to produce a final precipitation hardened silver alloy knitted structure. The final precipitation hardening step can cause increased tensile strength of the alloy, as well as a volume reduction which beneficially increases the flexibility of the knitted structure.

Subsequent to precipitation hardening the silver alloy can be cooled and then further formed or incorporated into a final product. As mentioned previously, the silver alloys of the present invention frequently experience a reduction in volume during the precipitation hardening process. Therefore, the step of providing the silver alloy can include forming the silver alloy into a shape having initial dimensions calculated to produce a precipitation hardened silver alloy having predetermined final dimensions. Thus, in order to achieve a desired final shape, the volume reduction can be accounted for during shaping of the silver alloy prior to precipitation hardening. In this way, the three-dimensional structure can be knitted such that an increased suppleness of the knitted fiber structure is realized upon precipitation hardening. The specific degree of volume reduction can depend on a variety of factors such as treatment temperatures, treatment times, alloy composition, original dimensions and configurations, and the like. However, as a general guideline, the final dimensions of the precipitation hardened silver alloy are about 0.5% smaller than the initial dimensions of the untreated silver alloy.

The following example illustrates an exemplary embodiment of the invention. However, it is to be understood that the following is only exemplary or illustrative of the application of the principles of the present invention. Numerous modifications and alternative compositions, methods, and systems may be devised by those skilled in the art without departing from the spirit and scope of the present invention. The appended claims are intended to cover such modifications and arrangements. Thus, while the present invention has been described above with particularity, the following example provides further detail in connection with what is presently deemed to be a practical embodiment of the invention.

EXAMPLE

A soft, annealed sterling silver alloy having 92.5 wt % silver, 6.3 wt % copper, 1.2 wt % germanium, and 0.002 wt % boron was obtained. The silver alloy was heated to about 100° C. and extruded through a drawing die. The silver alloy was drawn through a draw plate several times to achieve the desired diameter. The resulting wire had a diameter of about 0.005 inches. One wire was knitted to produce a knitted cable having a diameter of about 0.08 inches. This woven cable was relatively stiff. This knitted cable was then placed in a furnace at 230° C. for about 2 hours to precipitation harden the structure. The knitted cable was then air cooled at room temperature. The knitted cable was then heated to about 300° C. in a furnace for about 30 minutes under hydrogen as a final cleaning heat treatment. The precipitation hardened knitted cable was then allowed to cool. The precipitation hardened knitted cable had a breaking weight of about 15-20 lbs. Further, the precipitation hardened woven cable had an increased flexibility. An untreated sterling silver chain having links of ˜0.05 inches in diameter and ˜0.05 inches in length (each link) had a breaking weight of about 7 lbs. In addition, the knitted cable had about 12% by volume of the sterling silver wire, and about 88% by volume of free space.

It is to be understood that the above-referenced arrangements are illustrative of the application for the principles of the present invention. Thus, while the present invention has been described above in connection with the exemplary embodiments of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications and alternative arrangements can be made without departing from the principles and concepts of the invention as set forth in the claims.

Claims

1. A knitted fiber fashion accessory, comprising at least one silver alloy wire knitted in a three-dimensional structure, said silver alloy being a precipitation hardened silver alloy.

2. The knitted fiber fashion accessory of claim 1, wherein said silver alloy is a sterling silver alloy including copper and at least one additional alloying metal.

3. The knitted fiber fashion accessory of claim 2, wherein said alloying metal is a member selected from the group consisting of germanium, aluminum, magnesium, lead, antimony, beryllium, boron, and combinations thereof.

4. The knitted fiber fashion accessory of claim 3, wherein said silver alloy consists essentially of silver, copper, germanium, and boron.

5. The knitted fiber fashion accessory of claim 4, wherein said silver alloy has a composition of about 92.5 wt % silver, 6.3 wt % copper, 1.2 wt % germanium, and 0.002 wt % boron.

6. The knitted fiber fashion accessory of claim 1, wherein said precipitation hardened silver alloy has a yield strength of from about 1.5 to about 2.5 times that of an untreated silver alloy having an identical elemental composition.

7. The knitted fiber fashion accessory of claim 1, wherein the knitted fiber fashion accessory is precipitation hardened after knitting into the three-dimensional structure such that volumetric shrinkage during precipitation hardening results in an increased flexibility of the three-dimensional structure.

8. The knitted fiber fashion accessory of claim 1, wherein said precipitation hardened silver alloy has a volumetric shrinkage of about 0.5% that of the silver alloy prior to precipitation hardening.

9. The knitted fiber fashion accessory of claim 1, wherein the silver alloy wire has a maximum cross-sectional dimension of about 0.1 inches.

10. The knitted fiber fashion accessory of claim 9, wherein the silver alloy wire has a maximum cross-sectional dimension of from about 0.001 to about 0.01 inches.

11. The knitted fiber fashion accessory of claim 1, wherein said three-dimensional structure is selected from the group consisting of weave, braid, knitted, and knotted.

12. The knitted fiber fashion accessory of claim 11, wherein said knitted fiber fashion accessory comprises a member selected from the group consisting of a hollow tube, non-hollow tube, ribbon, sheet, and combinations thereof.

13. The knitted fiber fashion accessory of claim 1, wherein said three-dimensional structure is substantially free of joints or welds.

14. The knitted fiber fashion accessory of claim 1, further comprising means for attaching the fashion accessory to a human body.

15. The knitted fiber fashion accessory of claim 1, further comprising a decorative element coupled to the three-dimensional structure.

16. A method of forming a knitted fiber fashion accessory, comprising steps of:

a) providing a silver alloy wire, said silver alloy wire having at least one alloying metal;

b) knitting said silver alloy wire into a knitted fiber structure; and

c) precipitation hardening the silver alloy wire to produce a precipitation hardened silver alloy wire.

17. The method of claim 16, wherein the step of precipitation hardening includes;

a) heating the silver alloy wire to a first temperature sufficient to produce a substantially single phase solution prior to the step of knitting;

b) cooling the single phase solution to produce a solution treated silver alloy; and

c) heating the solution treated silver alloy to a second temperature less than the first temperature subsequent to the step of knitting and cooling the solution treated silver alloy, such that a second phase is precipitated to form the precipitation hardened silver alloy wire.

18. The method of claim 16, wherein the step of knitting occurs prior to the step of precipitation hardening.

19. The method of claim 18, wherein the knitted fiber structure has initial dimensions calculated to produce a precipitation hardened structure having predetermined final dimensions.

20. The method of claim 19, wherein the predetermined final dimensions are about 0.5% smaller than the initial dimensions.

21. The method of claim 18, wherein the three-dimensional structure is knitted such that volumetric shrinkage during precipitation hardening results in an increased suppleness of the knitted fiber structure.

22. The method of claim 16, wherein said silver alloy is a sterling silver alloy including copper and at least one additional alloying metal.

23. The method of claim 22, wherein said silver alloy consists essentially of silver, copper, germanium, and boron.

24. The method of claim 16, wherein the step of knitting further includes providing a sacrificial thread placed substantially parallel and adjacent to the silver alloy wire during knitting.

25. The method of claim 24, wherein the sacrificial thread is removed subsequent to the step of knitting.

26. The method of claim 24, wherein the sacrificial thread is a cotton thread.

27. The method of claim 16, wherein said precipitation hardened silver alloy has a yield strength of from about 1.5 to about 2.5 times that of an untreated silver alloy having an identical elemental composition.

28. The method of claim 16, wherein said silver alloy wire is a single continuous wire which forms substantially all of the knitted fiber structure.

29. The method of claim 16, further comprising the step of coupling to the knitted fiber structure a means for attaching the fashion accessory to a human body.

30. The method of claim 16, further comprising the step of coupling a decorative element coupled to the knitted fiber structure.

31. A fashion accessory, comprising:

a) a knitted fiber structure, comprising at least one silver alloy wire knitted in a three-dimensional structure, said silver alloy being a precipitation hardened silver alloy comprising silver, copper, germanium, and boron;

b) means for attaching the fashion accessory to a human body, said means being operatively connected to the knitted fiber structure; and

c) a decorative element connected to the knitted fiber structure.

32. The fashion accessory of claim 31, wherein said means for attaching is a latch, pin, looped configuration, clasp, finding, or combination thereof.

33. The fashion accessory of claim 31, wherein said silver alloy is a sterling silver alloy including copper and at least one additional alloying metal.