GB2060353A - Jewellery chains - Google Patents

Abstract

Jewellery chain are thickened by electroforming to obtain fattened chain links thereof such that the distance between interlinked pivoting points of each chain link of the chain are reduced to make the chain denser in construction. The increased thickness of the chain enhances the range of subsequent processes such as pressing, swaging and the like, which may be applied to the chain, so making it possible to produce a wide range of chain designs. An apparatus particularly suitable for the electroforming process is disclosed. <IMAGE>

Description

SPECIFICATION Jewlery chains by electroforming The invention relates to jewelry chains.

The many kinds of jewelry chains used for necklaces and other purposes can be roughly classified into machine-made and hand-made chains. The machine-made chains are continuously produced, being formed and linked from a wire or a strip by an automatic chain making machine designed and adjusted specifically as required, while the handmade chains are made generally by linking the links by hand one by one although some constituents of the links are made by automatic machines. In this connection it should be noted that hand-made links are more common in precious metal chains while machine-made links are more common in brass which is to be used for costume jewelry.

The machine-made chains can be made in quantities and thus economically though they naturally have their own technical limits in design and style, unlike the hand-made chains. One of the most difficult chains to make by machine is of a very dense construction which gets more difficult to make if the chain is finer. It is partly because a considerably sufficient space is required in the chain link in order to perform the process of interlinking chain links mechanically without trouble with a mechanical accuracy which is presently possible.

The only method known at present for making a chain of dense construction almost like a solid metal cord automatically and continuously to some extent is a process that is generally known as "swaging" in the trade. This involves continuously passing the chain made by machine between pressing dies with grooves of an appropriate section to compress the chain strongly to a desired form and then making a slight gap between the chain links, which have bit into each other, by repeatedly bending it by means, such as forcing the chain to pass between a plurality of rolls after softening its material by means such as annealing, and thus giving the chain a minimum flexibility necessary to its use for necklaces and the like.

The above described swaging process can be applied to many kinds of the machine-made chains.

However, if the joints of the chain links are not soldered, the chains are weak and easily broken since the joints of the chain links are apt to be opened with a slightly excessive bending power applied. Therefore, chains of higher quality of finer size must be soldered more strongly than usual before swaging.

The reason why extra strength is required is because the chain will break during the application thereto of such strong compression and deformation including the subsequent softening process unless it is very strong.

It is however technically very difficult to perform soldering on these chains automatically and continuously and still get the strength needed for breakage-free swaging. The present level of the art is that it is still not possible to avoid the production of a considerable quantity of defective chains during these swaging and softening processes.

Jewelry chains are generally required to be supple and capable of being smoothly bent. Since the flexibility of swaged chains is an accumulation of a limited freedom of each link acquired from a slight gap between the chain links compressed and deformed to bite into each other, the more links a chain has in a unit length, in other words, the shorter the distance between the interlinking points the more flexible is the chain, other factors being the same. Therefore, a chain to be swaged generally should have the distance between its interlinking points as short as possible. However, in the case of the machine-made chains the extent to which this distance can be reduced is limited for the reason already described.For instance, in the case of a fine cable as indicated in Fig. 24(a) of the accompanying drawings, or curb chain (tess than 1 millimeter in wire diameter), around 2.5 times the wire diameter is understood as the shortest such distance possible.

Though it still may be shortened in the case of thicker chains, it is theoretically obvious that it cannot be shortened to less than twice the wire diameter. Furthermore, this distance may stretch considerably in the swaging process, depending on the structure of the chain and how it is compressed, though there is little possibility of its being shortened.

Design and variety are the most important factors ofjewelry chains as merchandise. Therefore, machine-made chains too are subjected to various subsequent processes mechanically, automatically and continuously, in order to diversify the designs which can be produced,thoughthey are also used in their original designs as made by chain making machines. For example, attempts have been made to cut with a diamond tool or grind with a grinding wheel continuously along the sides of the chain so that regularly shaped flat surfaces thus created are displayed along the sides, to put a pattern on each link, to modify them continuously by pressing with appropriate dies, to twist them, orto use a combination of such processes to create from an original, machine-made chain products of greater decorative value and more diversified design.Even the swaging process may be included in this category as one of these subsequent processes. However, all these processes are limited to making the chain lighter or thinner by removing a part of material or letting it stretch along the length of the chain. There is no method yet known as far as the machine-made chains are concerned for positively thickening the chain continuously and uniformly to introduce enough chain material for further modifying processes.

According to the invention there is provided a jewelry chain thickened by electroforming, wherein an initial jewelry chain formed of interlinked chain links is thickened by electroforming to fatten the chain links, such that a distance between interlinked pivoting points of the chain links become smaller in relation to thickness of said chain link thus produced, thereby to make the chain of a denser construction.

The invention is thus directed to thickening chain links interlinked with one anotherto form a chain, the thickening being carried out uniformly and to any thickness by means of electroforming. The thick ening of the chain links by means of electroforming reduces the distance between interlinked pivoting points of the chain links, thereby to make the chain denser in construction per a unit length, and the thickening of the chain links can serve as a preliminary step before subsequent steps such as cutting, filing, stamping, pressing and swaging, thereby to obtain chains of novel and sophisticated design.

It has been found that the fattening of the chain links by electrochemical forming increases the tensile strength of the chain considerably and produces a jewelry chain of better flexibility by making the interlinked pivoting points of the chain links closer to one another, and further provides an advantage for subsequent processes especially in case of subsequent swaging processes. Furthermore, when a chain is fattened by the electrochemical forming process to a weight at least twice that which it had before the fattening even a chain of which links are not soldered has a strength almost possible to achieve with a chain of which the links are soldered beforehand, thus providing making it possible to eliminate the soldering process.If the chain is nevertheless soldered beforehand, strength of the chain is again increased by electroforming to about twice its value before electroforming.

Referring to Fig. 24(a), the distance (Ji) between interlinking points of the original chain links 1 is usually around 3d1 (d1 is an original diameter of the wire of which the chain links consist) and cannot be less than 2.5d1 by mechanical methods as mentioned already. In order words, it is impossible to get a chain of such a dense construction that/1 is less than 2.5d1 while after the same chain 1 is fattened about five times in weight per length, 12 (the new distance between interlinking points) becomes 2d2 or less (d2 is the new wire diameter in the average) constituting a chain of very dense construction compared with its thickness, impossible to make mechanically, because the wire diameter of the fattened links becomes on average \/5d1 = 2.236d1, while the inside diameter of the links becomes even shorter due to some metal deposition.

Also, the distance between interlinking points of a chain tends to be stretched by the links deforming and biting into each other longitudinally when the chain is subjected to pressure from the side by being pressed or swaged, whereby not only do the links lose much of their freedom of movement but also the number of links per unit length is descreased, both of which work against the flexibility of the chain to be obtained. However, if this distance between interlinking points of chain links is shortened to the minimum compared with its thickness and the interlinking space in the chain links is filled enough, as indicated in the case of the fattening extension Fig.

24(a) to 24(d), such a chain not only has more links per unit length compared with its thickness but also does not stretch, having no such space to fill, both working favourablyforthe flexibility of the chain to be obtained.

It is an advantage of the method of the invention that the visible outer parts of a chain are thickened relatively more than the invisible overlapped parts at interlinked points. Another advantage is that a chain can be fattened to a desired thickness and the extent of fattening is precisely adjustable by controlling the electric current and the processing time used for electroforming.

If a chain being thickened is moved during the electroforming process, the interlinked pivoting points at which it is relatively difficult to achieve electrodeposition are also thickened sufficiently so that the distance between the interlinked pivoting points is shortened, and further such deposition filling the spaces of the chain links limits the spaces available to allow the chain to extend in the interlinking direction, thereby making the chain less deformable and affording a considerable advantage for subsequent processes such as pressing and swaging.

The thickening of chain links by electrochemical forming according to the method of the invention tends to greatly increase the strength of a chain. This tendency is displayed conspicuously until the chain is thickened to double its original weight and after that quickly approaches a ceiling. This tendency also is utilized as fattening a chain. Through this thickening by electroforming the joints of the chain links are strengthened irrespective to whether they are closed by soldering, eliminating in some cases the soldering process in the manufacture of chain. Further, this strengthening of the joints of the chain links together with the shortening effect on the distances between the interlinked pivoting points of the chain serves to reduce the risk of breakages and production of defective products during subsequent processes such as pressing and swaging.

Thus, the electroforming process of the present invention is not only effective as a preliminary strengthening step before such subsequent processes but also by itself makes it possible to manufacture chains of many styles and considerable decorative value.

In other words, while chains made by automatic chain making machines are naturally limited in their design and variety, this invention makes it possible to produce low-cost chains by automatic chain making machines which chains are then thickened by electrochemical forming to a desired extent and modified into chains of many styles and kinds.

It is another object of this invention to provide an apparatus for carrying out the above stated thickening by electrochemical forming on decorative chains.

Generally, long chains are plated by various methods which can be roughly divided into the following three modes: The chains are (1 ) bundled together for plating: (2) framed for plating; and (3) allowed to pass continuously through a tank.

The modes (1) and (2) are suitable for a thin plating such as an ordinary decorative plating, but not suitable for electrochemical forming over a long period of time for obtaining a uniform thickening on a chain, because such methods tend to result in uneven parts. In the mode (3), the chains are allowed to pass continuously through a plating tank in the same manner as in plating a wire material. This method is suitable for production of the same kind of product in large quantities such as in the case of wire materials but not very suitable for production ofvar- ied kinds of products in rather small quantities such as in the case vith decorative chains.

According to an aspect of the present invention, therefore, there is provided an apparatus for thickening a jewelry chain by electroforming, comprising an electroforming tank provided with anodes which are disposed within said tank; turntable cathode bars disposed above the surface of an electroforming bath contained in said electroforming tank; nonconductive weight bars disposed within said electroforming bath and kept in parallel with said cathode bars, said turnable cathode bars and said weight bars being arranged to have a long jewelry chain material, or a long material line formed by connecting jewelry chain materials to each other, put around them in a multiple loop shape; and grooves, protrusions or spacers which are provided on said turnable cathode bars and also on said weight bars for separating one loop of said jewelry chain material from another loop thereof, a thickening electroforming process thus being arranged to be carried out on said jewelry chain material by rotating said turnable cathode bars.

Thus, in use of the apparatus of the invention, a long chain or chains interconnected into a long line (the latter as referred to hereinafter as a long chain) is wound in many suspended loops around rotating cathode bars positioned over the surface of an electroforming bath within an electroforming tank the inside of which is provided also with anodes. The long chain is immersed in this electroforming bath while the loops of it are continuously forwarded in loops one after another to obtain a desired thickening effect. In carrying out this feeding operation, loops of the long chain are prevented from becoming uneven by the non-conductive weight bars which are horizontally hung to rest on the lower ends of the loops so that the chain can be prevented from slipping of the cathode as the rotation of the cathode bars tends to cause the length of the chain loops to become uneven.Further, the spacing means such as grooves or protrusions ensures constant intervals between these loops longitudinally of the cathode bars and the weight bars. The chain is hung in a hooked manner within the grooves or between the protrusions so that the spacing distance between one loop and another of the chain is kept the same to keep the chain moving on the same path during the rotation of the cathode bars for attaining a uniform thickening effect.

Since the electroforming process is carried out by continuously forwarding the loops of a long chain in a given direction in an endless manner or by continuously supplying the loops of a long chain from a coil and taking out the loops to another coil, or by reversing the rotation of the loops at given intervals or at every given length of time, the whole chain including the upper ends of the loops which are above the surface of the solution can be uniformly subjected to the electroforming process for exactly the same length of time. Further, since the chain is stretched by the weight bars the chain never slips off the cathode bars and there is no irregularity in the electric current.Besides, bending of the chain which takes place when it passes the cathode bars or the weight bars gives suppleness to the interlinked parts of the chain to prevent it not only from stiffening but also from having a bending tendency in a specific direction.

The use of the weight bars also serves to make uniform the thickening effect on the chain so that the chain can be prevented from being bent and kept in the normal direction even when the chain becomes shorter in an advanced stage of the thickening process.

Since a rack for hanging the long chain down into the bath is not required, electroforming can be applied with 100 per cent efficiency without unnecessary deposition. Further, it is advantageous to carry out the thickening process by endlessly connecting both ends of the long chain or supplying the chain from a spool on one end and taking out the finished chain from the other end automatically and continuously and thus apply the electroformingto the whole length of the chain.

It is also advantageous to make the turning cathode bars square in cross-section so as to effectively avoid the chain so fattened lacking flexibility and slipping. It is advantageous to have an elastic member such as a coil spring, a rubber ring, or the like located between long chains such that the distance between the turning bar and the weight bar can change elastically. This arrangement effectively serves to maintain a constant tension of the long chain even while the distance between interlinking points becomes shorter as the electroforming process progresses.

In the accompanying drawings: Figs 1(a), (b), (c) and (d) are front and side views showing a chain material for a jewelry chain of a very simple style usually called a cable chain, successive figures showing successive states of its fattening by electroforming; Fig. 2 is an illustration of an electroforming apparatus; Fig. 3 is a graph showing fattening or thickening carried out in accordance with the present invention in relation to the strength of the chains subjected to the processes; Fig. 4 is a front view of another electroforming apparatus; Fig. 5 is a side view showing the apparatus of Fig.

4; Fig. 6-19 are illustrations of various jewelry chains; Figs. 20-23 are photographs of the chains corresponding to Figs. 6-19; Figs. 24(a) and (b} are illustrations of a jewelery chain before and after thickening by electroforming.

A cable chain 2 brazed or unbrazed which consists of ring shaped wire links or chain links, each link having an inner diameter! which is about 3 times the diameter d of the wire as shown in Fig. 1(a), was subjected to an electroforming process by an apparatus as shown in Fig. 2. The apparatus of Fig. 2 comprises an electroforming tank 3 containing a plating bath, a fixed anode 4, and a hooking rod 5 which serves as a cathode and also serves to hook the chain 2.The electroforming process was carried out under the following conditions: Compositk:- o.-. plating bath: 60 gll of H2SO4 and 290 g/l of CuSO4 Temperature: 28 C Current density: 1.5-2 Aids2 The products obtained by the electroforming process were as shown in Fig. 1(b), 1 (c) and 1(d).

Table 1 shows the results of the electroforming processes carried out on 50 cm of a cable chain material which was made of red brass wire (85 Cu - 15 Zn) measuring 0.65 mm in wire diameter and prepared without brazing the joining of the links thereof.

Table 2 shows the results of the same processes carried out for a chain material which was of the same kind but was brazed.

Table i. When a chain material not brazed was used Multi Weight plied, Strength Rate of Increase of Wire dia., No. g times kg* increase strength average a 5.07 1.00 1.7 1.0 0 1 b 10.20 2.01 8.0 4.7 6.3 1.42 c 15.35 3.03 10.0 5.9 8.3 1.73 d 25.30 4.99 12.0 7.1 10.3 2.24 Table2 When a brazed chain material was used.

Multi- Weight plied, Strength Rate of Increase of Wire dia, No. g times kg* increase strength average a 5.15 1.00 9.0 1.0 0 1 b 10.30 2.00 18.0 2.0 9 1.42 c 15.50 3.01 22.0 2.4 13 1.73 d 25.60 4.97 23.0 2.6 14 2.24 Note: Asterisk indicates a tensile strength.

The relation of weight increase to increase in strength is as shown in Fig. 3, which indicates that the strength increases very sharply until the weight doubles and the rate of increase in strength tails off thereafter.

When the unbrazed chain was thickened by electroforming to double its weight, the chain not brazed being so fattened obtained almost the same strength as the brazed chain. When the brazed chain was subjected to the electroforming process, the strength of the chain was almost doubled when the chain had been fattened to double its weight. Further, the fattening at each interlinking portion of the chain stopped when the sectional area had been increased up to more than double.

Referring to Fig. 4 and 5, an electroforming tank 12 is provided with anodes 11 made of copper plates enclosed in titanium cases which are disposed on two inner sides of the tank 12. A pair of turning cathode bars 13 having cross-sectional shape of 30 mm square are detachably mounted on the electroforming tank 12 above the middle part of the tank.

The cathode bars 13 are provided with vinyl chloride collars 14 and are spaced at equal intervals. A pair of non-conductive weight bars 15 are provided which are made of vinyl chloride pipes each measuring 20 mm in diameter with an iron core inserted therein as weight. The weight bars 15 are also provided with collars 14 which are made of vinyl chloride and are equally spaced. On the bearing parts at both ends of the weight bars 15, there are provided guide pipes 16 which are made of vinyl chloride and rise perpen dicularly to the weight bars. A guide rod 17 which is attached to the electroforming tank 12 is slidably inserted in each of the guide pipes via a spring 18 provided within the pipe. The guide rods 17 are thus arranged to lift up the weight bars 15 somewhat against the force of the spring 18.

Each of the cathode bars 13 is arranged to be rotatable by a motor 22 by means of a joint 19, a sprocket wheel 20 and a chain 21 which are disposed outside of the electroforming tank 12.

A reference numerat 23 indicates a liquid surface of an electroforming bath, and 24 indicates a long chain which is put around a first pair of a cathode bar 13, and a weight bar 15, to form a loop going from one end to the other in the leftward direction and then, at the other end, is continuously put around a second pair of cathode bar 132 and a weight bar 152 to form a similar loop going from one end to the other end thereof. The long chain is then again put around the first pair of the cathode bar 13, and the weight bar 151. In this matter, the long chain is placed endlessly around the pairs of cathode bars and weight bars.

A simple fattening process can be effectively attained by the use of, for example, an ordinary electroforming bath which is mainly composed of cop per sulphate. In cases where it is desired to impart a granular surface to the chain, the use of a cyanide bath which is composed of, for example, 80 g/l of cuprous cyanide, 7 to 10 g/l of free cyanide and 10 gil of Rochelle salt to carry out electroforming over a period of one hour at 60"C is effective. Normally, the electroforming process is carried out over a period of from 1 to 3 hours or thereabout.

However, in the practice of the invention, no particular restrictions are put on the conditions of the electroforming bath. When a long chain material to be processed is made of brass or red brass, the use of a copper sulphate bath (cut04 + H2504) gives a highly mailedDle electroformed layer. In that case, the bath requires no additive.In an experiment, for example, an electroforming bath composed of 290 gll of CuS04 and 90 gll of H2SO4was used and electroforming was carried out at a temperature of 30"C and a current density of 4 A/dm2 to obtain an even and smooth thickening effect at a rate of 1.2 to 1.3 glampere - hour up to a considerable thickness.

It should also be noted that normal preliminary treatments such as degreasing, activating and so on and subsequent processes as rinsing and neutralizing should be performed before and after this electroforming process of a long chain.

The invention will now be further explained in relation to various jewelry chains.

A basic process diagram is represented as follows:

Cn - f - I Ex 5--,0 > Pm Pm Pm Pm Pm In the above process diagram, ( - - - -} after I N;I eE53 indicates that the process ofExcan be repeated without limit. The definition af Pm, Cn, Ex and Ay is as below: Pm:; products produced as the result.

Cn: indicates an optionally original chain including all automatic machine-made and hand-made chains.

n indicates its type and kind (for example, like indicated C, to show a cable chain of a standard dimension).

Ex: indicates a thickening process by means of electroforming, x indicates a degree of the thickening. (For example, E,.5 may indicate a chain to be thickened until it weights 2.5 times heavierthan before per unit length).

Ay: indicates any process to affect design and style of a chain link except the thickening process mentioned above. y indicates kind and combination, degree and sequence thereof. (For example, supposing that A, represents grinding and A4 pressing, A4*, would represent grinding after pressing).The process of Ay includes, interalia: continuous or intermittent pressing and swaging, engraving, patterning, deforming, or cutting in part by means of a press, rolls, rotary swaging machine or the like; overall or part grinding by means of a grinding stone; overall or part cutting or patterning by means of a cutter including a diamond tool; twisting; addition orjoining entirely or partly of a part by means of brazing, caulking, etc; braiding of a plurality of chains; the connection of other parts of metal, plastics, glass or the like at regular intervals.

The details of the example processes are described below.

Example 1 A process corresponding to Cn < Ex~Pm is the simplest process of the basic process diagram in which the electroforming process is carried out on a cable chain as shown in Fig. (a) as an original chain and, as the result, chain products as shown in Fig.

1(b), (c) and (d) are produced.

Example 2: In a similar process to Example 1,the electroforming process is carried out on a double cable chain as shown in Fig. 6 A and B, and Fig. 20A as an original chain, thereby obtaining chain products as shown in Fig. 7 A and B, and Fig. 20B.

Example 3: In a process corresponding to Cn~Ex Ay Pm of the basic process diagram, the electroforming pro cess is carried out on a cable chain as shown in Fig. 8 and Fig. 21A as an original to obtain fattened cable chains as shown in Fig. 9 and Fig. 218 and the fat tened cable chains then swaged to a square shape to obtain chain products as shown in Fig. 10A and B, and Fig. 21 C.

Example 4: The chain products obtained in the Example 3 are further swaged to a round shape to obtain chain products as shown in Fig. 11A and B, and Fig. 218.

Example 5: In a similar process to Example 3, the electroform ing process is carried out on a Barley corn chain as shown in Fig. 12A and B, and Fig. 22A as an original chain to obtain fattened Barley corn chains as shown in Fig. 13 A and B, and Fig. 22B and the fattened Barley corn chains then swaged to obtain chain pro ducts as shown in Fig. 14 A and B, and Fig. 22C.

Example 6: The chain products of the Example 5 as shown in Fig. A and B, Fig. 22C are further subjected to a cutting by means of a diamond tool to obtain chain products as shown in Fig. 15A and B, and Fig. 22D.

Example 7: This process corresponds to Cn~Ay DEx~Ay )Pm of the basic process diagram.

In the process, S-curb chains as shown in Fig. 1 6A and B, and Fig. 23A are swaged to a square shape to obtain modified S-curb chains as shown in Fig. 17A, B and C and Fig. 23B and these modified S-curb k chains are then subjected to the electroforming pro cessto obtain chain products as shown in Fig. 18A, B and C, and Fig. 23C.

Example 8: The chain products of Example 7 as shown in Fig.

18A, Band C, and Fig. 23C are further swaged to a round shape to obtain chain products as shown in Fig. 19A, B and C and Fig. 23D.

Claims (17)

1. A jewelry chain thickened by electroforming wherein an initial jewelry chain formed of interlinked chain lines is thickened by electroforming to fatten the chain links, such that a distance between inter linked pivoting points of the chain links becomes smaller in relation to thickness of said chain link thus produced, thereby to make the chain of a denser construction.

2. Ajewelry chain as claimed in claim 1 wherein the initial jerdcIE-Y r::ra in is subjected to brazing at the butt joint portions o each chain link, and the brazed chain is thickened by electroforming, thereby increasing the strength thereof.

3. A jewelry chain as claimed in claim 1, wherein the initial jewelry chain is not subjected to brazing at the butt joint portions of each chain link, and the unbrazed chain is thickened by electroforming.

4. Ajewelry chain as claimed in any preceding claim, which is subjected to at least one subsequent process selected from pressing, swaging and the like.

5. Ajewelry chain thickened by electroforming wherein in each chain link of a jewelry chain, an overlapping portion of a chain link formed by chain links interlinked one another is thickened to a first thickness and other portion of said chain link except interlinking portion is thickened to a second thickness greater than the said first thickness, such that the distance between interlinked pivoting points of each chain link becomes smaller in relation to the thickness of the chain link thus produced, thereby making the chain denser in construction.

6. A jewelry chain according to claim 5, which is obtained by processes comprising a thickeneing process carried out by electroforming.

7. A jewelry chain according to claim 5 or 6, wherein the joint of each of the links is brazed.

8. Ajewelry chain according to claim 5 or6, wherein the joint of each of the links is not brazed.

9. A jewelry chain as claimed in any one of claims 5 to 8, wherein the thickened chain is subjected to at least one subsequent process selected from pressing, swaging and the like.

10. A jewelry chain as claimed in any preceding claim wherein the jewelry chain is cut and combined with other parts, or electroplated, for use as a neck lace, bracelet or the like.

11. A jewelry chain substantially as herein described with reference to the accompanying drawings.

12. A jewelry chain substantially as herein described with reference to any one of the Examples.

13. An apparatus forthickening a jewelry chain by electroforming, comprising an electroforming tank provided with anodes which are disposed within said tank; turnable cathode bars disposed above the surface of an electroforming bath contained in said electroforming tank; nonconductive weight bars disposed within said electroforming bath and kept in parallel with said cathode bars, said turntable cathode bars and said weight bars being arranged to have a long jewelry chain material, or a long material line formed by connecting jewelry chain materials to each other, put around them in a multuple loop shape; and grooves, protrusions or spacers which are provided on said turnable cathode bars and also on said weight bars for separating one loop of said jewelry chain material from another loop thereof, a thickening electro-forming process thus being arranged to be carried out on said jewelry chain material by rotating said turnable cathode bars.

14. An apparatus according to claim 13, wherein said turnable cathode bars are of a square sectional shape.

15. An apparatus according to claim 13 or 14, wherein said jewelry chain material is formed by connecting jewelry chain materials to each other through elastic members interposed in between them to cancel out, by elongation of said elastic members, the decrease of distance between the connecting points of said jewelry chain material which takes place as said electroforming process proceeds.

16. An apparatus according to claim 13, wherein the distance between said turnable cathode bars and said weight bars is arranged to shorten in response to the decrease which takes place in the distance between the connecting points of said jewelry chain material as said electroforming process proceeds.

17. An apparatus for thickening a jewelry chain substantially as herein described with reference to Figs. 4 and 5 of the accompanying drawings.