Rope Chain With Novel Link

This invention relates to a new design for the wire forming the link members of rope chain.

Jewelry rope chain has been known for many decades, both in a hand-made and machine made forms, with machine made forms of these chains generally being limited to less expensive chains, where less precision in the joining of the links of chains is required. However, regardless of the method used to assemble the individual links into the rope chain, the cost of precious metals and their alloys, such as 14 Karat gold and the like used to make the chain is a large component of the final cost of the finished rope chain.

While assembly costs can be decreased by manufacturing rope chain in countries with low labor costs and by introducing labor saving tools and machines, the jewelry manufacturer can do little about the cost of gold, platinum, and other precious metal, which are almost identical around the world. Therefore, there is a strong need for the manufacture of rope chain designs which, while preserving the same look (and also width of chain) as conventional chain designs, in fact, use substantially less precious metal per unit length.

In order to gain a better understanding of the solution to the objective of saving precious metals in making rope chain, it is instructive to review the basics of rope chain manufacture. All rope chains are assembled from a large number of annular link members with gaps. Such a typical link 10 is shown in FIGS. 1-3. Traditionally, these links have been either solid 10 (FIGS. 2a or 2b) or hollow 10a (FIG. 3) and either having a generally rectangular or circular cross-sections FIG. 2a or FIG. 2b. By arranging series of these rings with their gaps G alternately facing up and down, e.g. as described in Benhamou, et al. U.S. Pat. No. 4,651,517 the rope chain is gradually built up, held in place with a forming wire 12, and soldered at points S to form the rope chain shown in FIG. 4.

In these prior art chains, the individual links 10 are chosen so that the central opening Di in the ring 10 has a diameter slightly greater than three times greater than the widest portion of the link wire Dw, for example, 3.4 times greater. Arranged in this way, four links would make up the basic, repeating, series of links used to form the chain.

U.S. Pat. No. 4,651,517 to Benhamou, et al. discusses the prior art rope chains in great detail, and discloses an improvement over the traditional prior art method in saving precious metal for an equivalent length and width of finished rope chain whereby instead of using a series of four repeating rings arranged as shown in FIGS. 5a-5d therein, a series of 6, 8 or more even number of links, each having a larger internal diameter compared to the ring cross-sections of the prior art chains are used to save material as shown in FIGS. 8a-8g therein. Additionally U.S. Pat. No. 4,996,835 to Rozenwasser and S.I.L.O. patent DM014648 illustrate rope chains wherein the links are non-circular in shape, in order to save precious metal.

These prior art rope chains utilize links in which the wire cross-sections thereof are basically circular, or rectangular with rounded corners. Although the shapes of the prior art links achieve the goal of allowing the manufacturer to save precious metal, for a given width and length of chain, their use generally results in increased labor costs since a greater number of links must be assembled to make a rope chain having the same length and width. Moreover, as the number of links per unit length increases, the chains may become more difficult to assemble.

It has also been known in the prior art of making flat chains to use precious metal wire having a triangular cross-section, with one corner of the triangle defining the outermost perimeter of each link member. The applicant himself has previously made rope chains with wire having a triangular cross-section, with one corner of the triangle defining the outermost perimeter of the wire once formed into the individual link members. Although material is saved, rope chains assembled from such wire have a somewhat corrugated appearance and feel sharp to the touch. Thus rope chains made from triangular link wire formed into link members with one corner of the wire defining the outer perimeter of the link members are not as desirable as prior art chains made of "smoother" link wire from the standpoint of appearance and feel of the finished rope chain. There is accordingly a need for rope chain which is formed in a way to save material, but which can be assembled without using a greater number of links per unit length, and which also results in a smooth, tight, and non-corrugated appearance.

The instant invention achieves the desired goal of both reducing the quantity of precious metal, without increasing the number of links required to assemble a rope chain of a given width (outside diameter) and length, by modifying only the shape of the cross-section of the wire used to form the individual links. The overall geometry of the link shape itself can remain as in the prior art, e.g. circular, as shown in FIG. 1, oval, as shown in Rozenwasser (see FIGS. 11-13, 17a-f and 20 therein), hexagonal, S.I.L.O. (See FIG. 4 therein), or other non-annular forms of links.

The wire cross-section of the links of this invention is formed so that the weight (or volume) of precious metal material nearest the outer perimeter in the outer peripheral volume, is greater than the weight (or volume) of the precious metal material near the inner perimeter in the inner peripheral volume. The inner peripheral volume of the wire, for definitional purposes, is formed on the interior side of a phantom bisecting surface drawn midway between the outermost perimeter of the wire and the innermost perimeter of the wire. The outer peripheral volume of the wire, for definitional purposes herein, is formed on the exterior side of a phantom bisecting surface drawn midway between the outermost perimeter and the innermost perimeter of the wire.

The cross-sectional configurations of the link wire forming the individual links may have a variety of cross-sections including those depicted in FIGS. 6a-6m. In order to clearly understand the benefits conferred by this invention, it should be noted that the modifications here to be explained are directed only to modifications in the wire cross-section forming the link, and not to the overall link shape itself. Thus the term "overall link shape", as used herein, refers to the finished link shape with a gap formed therein, as depicted in e.g. FIGS. 1-3, and the term "wire cross-section" or "link wire cross-section" refers to the cross-section of the wire which is later formed into a partially closed finished link member of annular or non-annular configuration having a gap between opposed ends, with the gap being slightly larger than the maximum width of the wire. Typical wire cross-sections of this invention are depicted in FIGS. 6a-6m.

By using link wire having a cross-section shown in FIGS. 6a-6m, the total number of individual links for a given rope chain link assembly can remain unchanged, but the quantity of precious metal will be substantially less than a similarly rope chain assembled from prior art square or circular cross-section link wire. Each of the link wire cross-sections of FIGS. 6a-6m are shown with phantom circles drawn in dotted lines in their backgrounds. Viewing FIG. 5, which is a plan view of one possible overall link shape into which the link wire of this invention can be formed, the outwardly most projecting portion of the link wire Y defines the outermost perimeter of the link and the inwardly most projecting portion X defines the innermost perimeter of the link.

The precious metal material savings realized by using link wires having the cross-sections shown in FIGS. 6a-6m are substantial. For example, for the wire having an "inverted triangle" cross-section, such as that shown in FIG. 6f, the material saving compared to a link made of link wire having a circular wire cross-section of the equivalent girth is approximately 36%. Even greater weight savings are achieved by using link wire having a "T"-shaped cross-section, such as that shown in FIG. 6c, where a 46% weight savings can be attained over a link made of round wire. These figures are even higher when these link wire cross-sections are compared to link wire having a square cross-section. For example, the "inverted" triangle link wire cross-section of FIG. 6f achieves a net weight savings per link of 50% and the "T"-shaped link wire cross-section of FIG. 6c saves approximately 58% material. The calculations for these two shapes are set forth below in the detailed description.

FIG. 1 is plan view of an annular link of the prior art;

FIGS. 2a and 2b are cross-sections of two typical prior art solid wires forming the annular link of FIG. 1, each taken along the line 2--2;

FIG. 3 is a cross-section of a prior art hollow wire forming the annular link of FIG. 1;

FIG. 4 is a side elevation showing a section of rope chain of the prior art in the process of being assembled with the forming wire not yet removed;

FIG. 5 is a plan view of one of the possible link shapes into which the link wire of the instant invention can be formed;

FIGS. 6a-6m show cross-sections of a number of possible embodiments of the link wire of the invention;

FIG. 7 is a plan view of one of the possible link shapes into which the link wire of the present invention can be formed, showing the mid-plane; and

FIG. 8 is a cross-sectional view of a "T"-shaped link through 7--7 in FIG. 7.

FIGS. 1-4 of the prior art have been described above and need no further discussion.

One of the possible overall link shapes into which the link wire of this invention can be formed is shown in FIG. 5 and is designated by the number 20. The ratio of the inner overall link diameter Di to the major wire diameter (Dw, the distance between points X and Y in FIGS. 6a-6m) can be chosen to be 3:1 or greater. Alternately, the link shapes can be made elongate to have a longer major axis and shorter minor axis with the major axis defining the thickness of the rope chain, e.g. as depicted in S.I.L.O. DM 014,648 or Rozenwasser, U.S. Pat. No. 4,996,835.

As is clear from FIGS. 5 and 6a-6m of the invention, the majority of the weight of wire 20 lies within the outer peripheral volume M-Y of the wire, as opposed to the inner peripheral volume M-X of the wire once the wire is formed into the individual link members.

This arrangement is also clearly shown with regards to FIGS. 7 and 8, which are respectively a top plan view of a circular link members, and a cross-sectional view of it showing a wire having a "T"-shaped cross section. (Such as that shown in FIG. 6c). With such an arrangement, the majority of the weight of precious materials of the link member 30 will lie in the outer peripheral volume 31 of the link member and the balance of precious material of the link member will lie in the inner peripheral volume 32 of the link member, the outer and inner peripheral volumes 31 and 32 being separated by a phantom bisecting surface 33 drawn at a point "M" midway between the outermost perimeter 34 ("Y" in FIGS. 5 and 6) and innermost perimeter 35 ("X" in FIGS. 5 and 6) of the link member 30. The thickness of each link member 30 is defined by the maximum width 36 of the link wire along a line perpendicular to the outer periphery 34 and inner periphery 35 of the link wire. The phantom bisecting surface 33 may be circular in its path, as in the case of an annular link member, may follow a hexagonal course, as in the case of a hexagonal link member, or may follow an oval course, as in the case of a oval link member. The cross-section of the link wire usually, but not always, is symmetrical along a plane 37 drawn perpendicular to and drawn bisecting the phantom surface 33 drawn midway between said outer and inner peripheral volumes M-Y and M-X, respectively.

As previously discussed, the amount of precious metal saved by using link wire having cross-sections of the shapes shown in FIGS. 6a-6m will be substantial when compared to links made from round or square link wire. These precious metal savings are all accompanied without the need to use a greater number of links per unit length of finished rope chain. Thus, precious metal can be saved without labor costs being increased.

As an example of the weight savings over the prior art equivalently shaped link elements having a square or circular cross-section, the following examples are set forth:

Comparing the cross-sectional surface area of an "inverted triangle" cross-section wire (shown in FIG. 6f), to a square cross-section wire having sides of length=2d, and a cross-sectional area equal to 2 d.multidot.2 d=4 a.sup.2, the weight savings are approximately as follows: ##EQU1##

Comparing the cross-sectional surface area of the "inverted triangle" to the surface area of a circle with a radius=1d, the savings are also substantial: ##EQU2##

For a T-shaped cross-section (FIG. 6c) where the top of the "T" is 2d wide and 0.4d thick and the bottom arm of the "T" is 1.6d long and 0.55d wide, the weight savings are even greater: ##EQU3##

A further benefit is that unlike the prior art hollow wire, (which link wire is difficult and costly to produce) the various link wires of the cross-sections shown herein are easily manufactured and the links made from these solid link wires are easily assembled.

The outer diameter or width of a rope chain is determined by the widest portion of the link Do which straddles the gap G in the overall link member 10. (See FIG. 5). The inner diameter Di of the link member 10 determines the ratio of the major wire diameter Dw to the inner diameter Di of the overall link member 10. In addition to the ease of forming link wire having a circular cross-section or a rectangular cross-section with rounded corners, links made from such wire members, give the finished rope chain a smooth, tight, and non-corrugated appearance.

The inventor has found by using link member of link wire cross-section with the majority of the weight of precious material lying in the outer peripheral volume of the link member, the finished rope chain of the instant invention will have a smooth, tight, and non-corrugated appearance much as the prior art rope chains, yet using far less precious material. This goal is achieved since the desired ratio of major wire diameter Dw to link member inner diameter Di is unchanged, and thus the number of link members per unit length of chain is not increased, all while the weight of precious metal per link is decreased.

The drawings and the foregoing description are not intended to represent the only form of the invention in regard to the details of its construction and manner of operation. In fact, it will be evident to one skilled in the art that modifications and variations may be made without departing from the spirit and scope of the invention. Changes in form and in the proportion of the wire cross-section are contemplated as circumstances may suggest or render expedient; and although specific terms have been employed, they are intended in a generic and descriptive sense only and not for the purpose of limitation, the scope of the invention being delineated in the following claims: