GB1599438A

GB1599438A - Laser welding process and apparatus for the links of a metallic chain

Info

Publication number: GB1599438A
Application number: GB16738/78A
Authority: GB
Original assignee: Alcyon Equipment SA
Current assignee: Alcyon Equipment SA
Priority date: 1977-05-05
Filing date: 1978-04-27
Publication date: 1981-10-07
Also published as: CH620616A5; DE2819877A1; FR2389447B1; FR2389447A1; IT7822873A0; IT1095622B

Abstract

As the chain moves along, each link passes in succession onto the welding station where the welding zone (5) is cleared from the adjacent link by a positioning jig (7), onto which zone is focused a laser beam (2), the emission of which is triggered by a presence detector (8). The welding is carried out without addition of material in a very reproducable manner, this method applying particularly well to the welding of links of gold chains and of jewellery. <IMAGE>

Description

,54) LASER WELDING PROCESS AND APPARATUS FOR THE LINKS OF A METALLIC CHAIN (71) We, ALCYON EQUIPMENT S.A., a company organized under Swiss laws of Chemin de la Roche 1, 1020 Renens, Switzerland, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: - This invention concerns a welding process for the links of a metallic chain in which each link of the assembled chain may receive a laser beam directed towards the abutting surfaces in the wire forming the link, thereby realizing completion of said link by fusion of the two abuting portions thereof. Such a process is referred to hereinafter as "closing" the link.

Methods are already known intended to obtain the closing of a chain link on itself by means of brazing or welding. Such methods imply the addition of material and an increase in temperature along the chain, particularly in the welding zone.

In the case of chains for which the surface finish of the links is of importance from an aesthetic viewpoint, such closing methods require that each chain link be separately retouched after closing thereof, this bringing about additional manufacturing expenses. Moreover, the cost of the additional material may be considerable factor in the costs of the entire closing operation.

A further difficulty appears insofar as the non-reproducibility of welds or brazings effected by known closing methods is such that the chain formed by links closed by such methods shows points of varying resistance, so that ihe breaking strength differs considerably from the average for well closed links. This situation thus further necessitates an inspection operation following closing of the chain links thereby once again increasing manufacturing costs.

This invention has as one object a process which avoids these difficulties and is characterised by a method of welding together abutting portions of links in an assembled chain comprising the steps of moving the chain past a fixed point, displacing the chain links so that when the abutting portions of said links arrive at said fixed point they are unobstructed by adjacent links, sensing the arrival of the links having unobstructed abutting portions at said fixed point and directing a laser beam toward the abuting portions at the fixed point, of sufficient intensity to effect welding together of said abuting portions.

The present invention also provides an apparatus for carrying out the above method comprising: a laser welding unit arranged to direct its beam into a fixed point, a chain feeding mechanism arranged to move a chain through an area including said fixed point, a chain link positioning jig located within said area provided with first and second through passages adapted to the gauge and type of chain to be treated, said passages being at a predetermined angle to each other or rotated relative to one another around the longitudinal axis whereby the chain in traversing said passages has its links displaced relative to one another, thereby to expose the abutting portions of a link, and sensing means adjacent said intersection arranged to sense the presence of a link having its abutting portions exposed thereby to trigger the laser welding unit.

Moreover, the mechanism or positioning jig of a preferred embodiment of the present invention permits presentation of the abutment of each link in a fixed position relative to the welding optics with a tolerance such that the laser beam, for which the energy is maintained within predetermined limits, effects weld of which the tearing strength is highly reproducible from one link to the next.

The preferred arrangement further includes detection means intended to discriminate automatically links on which the welding operation has not been effected by reason of failure to supply the necessary energy by the laser beam.

Finally, the method and the apparatus for its application permit realization of chain link welds of which the surface quality may avoid the necessity of retouching operations.

For a better understanding of the invention, reference will be made to the attached drawings in which Figure 1 is a functional schematic diagram of a welding arrangement applying the invention.

Figures 2, 3, 4 and 5 show specific particularities by which the invention may be applied to the welding of links of a gourmette-type chain.

Figures 6, 7 and 8 concern the welding of a simple chain.

Figures 9, 10 and 11 relates to the welding of a venetian-type chain.

According to figure 1, the welding arrangement is formed from a source 1 emitting a laser beam 2 through an energymeasuring instrument 3 and welding optics 4 intended to concentrate the laser beam 2 onto the region 5 to be welded, of the links of a chain 6. Each link is automatically brought into a fixed welding position by a positioning jig 7 with which is associated a detector 8 which senses and signals the instant at which the abutment in the link coincides with the spatial position where the weld may be realized. Chain 6 is fed continuously tnrough jig 7 by drive mechanism 9 associated with tension regulating mechanism 10, all of these foregoing elements being mounted on a base 11. The energy of the laser beam 2 is measured at each pulse by instrument 3, the latter being connected to a master electronic control 12 in a manner to regulate the energy delivered by energy supplier 13 to the laser source 1.

The master electronic control 12 controls further functions within the process including triggering the laser beam 2 when detector 8 establishes that a link abutment is in a spatial position at the fixed point wihch permits its closing by welding, the drive mechanism 9 and the tension regulator 10, the triggering of an audio-visual alarm 14 and/or stopping the process system should the laser emission fail or should there be any failure in the movement of the chain 6.

A large number of chain types are knonw, each type comprising links having their own specific geometry with an abutmnet located always at the same place for each of the links of a predetermined chain.

Such location may however be different for different chains even when of the same type according to the method utilized for forming, linking together and closing the links, starting from the base material thereof. The operation of closing a link by simultaneous fusion of the two portions of the link adjacent the abutment thereof without addition of material and by means of a laser beam requires that the zone where the welding occurs be at a fixed position such that no opaque body inter- rupt the laser beam. Such interruption may occur in all cases where the link geometry and the method according to which links are formed results in concealment of the abutment by an adjacent link when the chain is linearly tensioned.

Thus arises the requirement to apply a position jig 7 adapted to the type, to the gauge and to the dimensions of each chain in a manner to assure the disengagement of the abutment in the link to be welded from the portion of an immediately neighbourhing link which may conceal it when the chain is leanerly tensioned.

This disengagement is obtained in the positioning jig 7 through bringing about a relative displacement between the link located at the fixed point and the following link or preceding link according to the situation. Such relative displacement is obtained by modifying at the fixed point the path direction in which the chain moves or in effecting twisting of the chain at this point, or without changing the general direction of movement in effecting a path dislocation as for example by a stair step within the jig at the fixed point. The solution adopted wil depends, of course, on the type of the chain and may combine various of the methods mentioned hereinabove. Positioning jig 7 may thus provide two separated passages which meet at the fixed point where their arrangement relative to one another brings about the desired change in the direction of the movement and accordingly the relative displacement of the links. Thus the passages may meet at a predetermined angle, may be rotated relative to one another around the longitudinal axis, or may have their axes indifferent planes in order to realize the desired discontinuity.

Figures 2 to 11 show the problems posed by various types of chains and the pigs associated with these types in order to resolve such problems, by enabling the feeding of the welding point by continuous passage of the links of the chain properly.

displaced relative to one another.

Figure 2 shows a chain of the gourmettetype having links 15 with their abutting surfaces 16 hidden by the following link 17.

Figure 3 shows for this type of chain the feeding principle by which chain 6 is drawn through Jig 7 specific to this type of chain. Chain 6 passes through feed mechanism 9 which places it under tension, then through a tension control means 10, jig 7 and finally drive mechanism 18.

Figure 4 shows the principle of the jig 7 specific to the gourmette-type chain of figure 2 in order to disengage the abutting surfaces 16 of the link to be welded 15 from neighbouring link 17. In this sectional plan chain 6 enters pasage 19 having a rectangular section where it is guided in an upright position and at the exit of which it passes around shoulder 20 where it undergoes a twisting of 90" and a change in path direction of 90" before entering a second passage 21 of identical section to the preceding but rotated 90" about its longitudinal axis whereby chain 6 exits in a horizontal position. Link 15 for which abutment 16 has been disengaged from the following link 17 is shown in a position such that abutment 16 coincides with the spatial position of a fixed target point suitable for laser welding.

Figure 5 shows a perspective of the jig 7 specific to the gourmette-type chain. Jig 7 compirses passage 19 intended to guide chain 6 in an upright position and to bring it to the rounded shoulder 20 where it undergoes a twisting of 90" enabled by cut-outs 22 and 23 and a path deviation of 90" to arrive at passage 21 in which it runs flat. Jig 7 compirses a further cutout 24 so that the laser beam may be unobstructed and concentrated at the fixed point 5, the position which the abutment in a chain link will occupy when it has been disengaged from the following link.

It will be noted on figure 5 that the longitudinal axes of the two passages 19 and 21 are not necessarily in the same plane and there results therefrom a jump or discontinuity at the intersection thereof, this helping to complete the other arrangements.

Figure 6 shows a simple chain having links 15 with their abutting surfaces 16 hidden bv the following link 17, two successive links occuping respectively positions in planes perpendicular to one another for a tensioned chain.

Figure 7 shows for this type of chain the principle of the feeding and tensioning mechanism in conjunction with jig 7 specific of this type of chain. Chain 6 passes through feed mechanism 9 which tensions it, then from a tension controlling device 10 to jig 7 and finally to the drive means 18.

Figure 8 shows the principle to be employed for a jig specific to the simple type of chain in order to disengage the following link 17 from the gap 16 of the link to be welded 15. Chain 6 enters a pasage 19 where it is guided flat relative to a predetermined plane parallel to every other link and at the exit of which it passes between jaw 25 which are spring urged so as to center and position the link to be welded 15 in a manner such that angle 26 is less than 90" in order to obtain disengagement of abutment 16 from the following link 17. Abutment 16 is thus brought into coincidence with the fixed point where laser welding may take place.

Chain 6 thereafter enters passage 21 where it continues to be flat guided in the sense defined above. The two passages 19 and 21 are of rectangular section and provided at their bases or on their two opposed sides with a guidance slot which maintains the links in a fixed plane.

The construction of a simple chain in two alternate series of links alternately parallel to two planes separated by 90" foresees a double operation in which all links situated in the same plane, are welded during a first pass and there follows a second pass, either with the same welding apparatus or by means of a second welding apparatus coupled with the first, so as to weld all links situated in a plane perpendicular to the first.

Figure 9 shows a chain of the so-called venetian-type having links 15 with their abtument 16 situated in one corner, and therefore at least partially hidden by the following link 17.

Figure 10 shows the principle of a feeding device for this type of chain, chain 6 being pushed through jig 7 by the feed device 9 and thence through a tension controlling mechanism 10 drawn by an exiting drive mechanism 18.

Figure 11 shows the principle employed in jig 7 as used with the venetian chain for which the links have their abutment in one corner. It is necessary that abutment 16 of link 15 upon entering the welding zone be uncovered by preceding link 17 thereby to enable laser beam welding. The chain enters passage 19 having a squared cross-section intended for direct guidance of every other link. The links to be welded pass thereafter over a discontinuity in the form of a jump or stair step 27 intended to disengage preceding link 17 from abutment 16 of the link to be welded 15. The chain then enters a second passage 21 of the same section as the first, provided at its entry with a supporting jaw 25 spring urged and intended to retain the chain which in this case is pushed through jig 7 in a fashion such that the zone surround in.g abutment 16 where the welding is to take place is no longer in contact with the preceding link 17. Passage 21 where the chain continues to be guided in the same manner as in the first passage 19 is at an angle of less than 90" relative to the first passage 19, this being desirable in addition to the discontinuity 27 for proper disengagement of abutment 16.

The arrangement of the venetian chain in two alternating series of similar links but arranged at 90" relative to one another obliges welding of all links belonging to one series during the first pass through a jig 7 such as shown hereinabove, then during a second pass welding all links of the second series either by the same welding apparatus or through a second apparatus coupled to the first.

Not all chains require tools quite so complex as those hereinbefore described for laser welding especially where the link abutments are not hidden by other links.

Nevertheless some guidance will always be necessary to assure that each gap to be closed occupies a precise spatial position during the welding operation, and the apparatus of the present invention will therefore also be useful in the welding of these chains.

Finally, chains formed by links of different forms from those hereinbefore defined or by multiple links may be positioned for laser beam welding of the links in a tool comprising at least one of the hereinbefore described characterisics.

Owing to the excellent reproducibility of the welds obtained by the hereinbefore described method and apparatus in respect of their mechanical resistance and their aesthetic aspect, the method, the apparatus and the chains obtained thereby may find a utilization especially attractive in the domain of fine jewellery manufacture.

WHAT WE CLAIM IS: 1. A method of welding together abutting portions of links in an assembled chain comprising the steps of: - moving the chain past a fixed point, displacing the chain links so that when the abutting portions of said links arrive at said fixed point they are unobstructed by adjacent links; sensing the arrival of the links having unobstructed abutting portions at said fixed point and directing a laser beam toward the abutting portions at the fixed point, of sufficient intensity to effect welding together of said abutting portions.

2. Apparatus for carrying out the method of claim 1 comprising: a laser welding unit arranged to direct its beam into a fixed point, a chain feeding mechanism arranged to move a chain through an area including said fixed point, a chain link positioning jig located within said area provided with first and second through passages adapted to the gauge and type of chain to be treated, said passages being at a predetermined angle to each other or rotated relative to one another around the longitudinal axis whereby the chain in traversing said passages has its links displaced relative to one another, thereby to expose the abutting portions of a link, and sensing means adjacent said intersection arranged to sense the presence of a link having its abutting portions exposed thereby to trigger the laser welding unit.

3. A chain having its links welded in accordance with the method of claim 1, 4. The utilisation in jewellery of chain having its links welded in accordance with the method of claim 1.

5. A method in accordance with claim 1 characterized in that the link displacement is effected at least partially through changing direction of the chain feed path.

6. A method in accordance with claim 5 characterized in that the link displacement is effected at least partially through provision of a stepped portion in the chain feed path.

7. A method according with claim 5 characterized in that the link displacement is effected at least partially by rotation of the chain through a predetermined angle about its longitudnal axis.

8. A method in accordance with claim 7 wherein the chain is a "gourmette" characterized in that the directional change and the rotation angle are each 90".

9. A method in accordance with claim 5 wherein the chain is a simple chain characterized in that the directional change is less than 90".

10. A method in accordance with claims 5 and 6 wherein the chain is a " venetian " chain characterized in that the directional change is less than 90 .

11. Apparatus in accordance with claim 2 characterized in that the jig provides passages of rectangular cross section adapted to the gauge of a "gourmette" chain, the predetermined angle being 90" and the second passage being rotated 90" about its longitudinal axis relative to the first passage.

12. Apparatus in accordance with claim 11 characterized in that a step is provided at the intersection af the passages.

13. Apparatus in accordance with claim 2 characterized in that the jig provides rectangular passages slotted at the bottom so as to be adapted to the gauge of a simple chain and at an angle such that the change of direction of the chain from the first to second passage is less than 90".

14. Apparatus in accordance with claim 13 characterized in that the jig is provided with biased gripping means thereby to maintain the position of a link whose abutting portions are exposed.

15. Apparatus in accordance with claim 2 characterized in that the jig provides squared passages adapted to the gauge of a "venetian" chain arranged at an angle such that the change of direction of the chain from the first to the second passage

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. obliges welding of all links belonging to one series during the first pass through a jig 7 such as shown hereinabove, then during a second pass welding all links of the second series either by the same welding apparatus or through a second apparatus coupled to the first. Not all chains require tools quite so complex as those hereinbefore described for laser welding especially where the link abutments are not hidden by other links. Nevertheless some guidance will always be necessary to assure that each gap to be closed occupies a precise spatial position during the welding operation, and the apparatus of the present invention will therefore also be useful in the welding of these chains. Finally, chains formed by links of different forms from those hereinbefore defined or by multiple links may be positioned for laser beam welding of the links in a tool comprising at least one of the hereinbefore described characterisics. Owing to the excellent reproducibility of the welds obtained by the hereinbefore described method and apparatus in respect of their mechanical resistance and their aesthetic aspect, the method, the apparatus and the chains obtained thereby may find a utilization especially attractive in the domain of fine jewellery manufacture. WHAT WE CLAIM IS:

1. A method of welding together abutting portions of links in an assembled chain comprising the steps of: - moving the chain past a fixed point, displacing the chain links so that when the abutting portions of said links arrive at said fixed point they are unobstructed by adjacent links; sensing the arrival of the links having unobstructed abutting portions at said fixed point and directing a laser beam toward the abutting portions at the fixed point, of sufficient intensity to effect welding together of said abutting portions.

3. A chain having its links welded in accordance with the method of claim 1,

4. The utilisation in jewellery of chain having its links welded in accordance with the method of claim 1.

is less than 90".

16. Apparatus in accordance with claim 15 characterized in that a step is provided at the intersection of the passages.

17. Apparatus in accordance with claim 2 characterized in that the chain feeding mechanism pulls the chain.

18. Apparatus in accordance with claim 2 characterized in that the chain feeding mechanism pushes the chain.

19. A chain in accordance with claim 3 comprising a "gourmette" chain.

20. A chain in accordance with claim 3 comprising a simple chain.

21. A chain in accordance with claim 3 comprising a "venetian" chain.

22. A method of welding together abutting portions of links in an assembled chain, substantially as herein described with reference to Figure 1, or Figure 1 with either Figures 2, 3, 4, and 5 or Figures 6, 7, and 8 or Figures 9, 10 and 11.

23. An apparatus for welding together abuting portions of links in an assembled chain, substantially as herein described with reference to Figure 1, or Figure 1 with either Figures 2, 3, 4, and 5 or Figures 6, 7, and 8 or Figures 9, 10 and 11.

24. A chain when made by the method of claim 22 or on the apparatus of claim 23.