BE379017A - - Google Patents

Description

       

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  Improvements to the processes and apparatus used for welding and improvements to welded products
The present invention relates generally to electric welding and more particularly to a method and to an improved apparatus for the continuous welding or for the intermittent welding of metallic objects and especially for the welding of objects. tubular in shape.

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   Electric welding has developed rapidly in recent years. Although welding methods and welding apparatus have been devised and used for continuous welding or for intermittent welding of materials such as tube-shaped objects, they have, to date, had certain drawbacks. .



   In the first place, it should be noted that most industrial installations have been constructed in such a way that they operate by means of a current supplied by fixed or movable contacts applied to different parts of the surface of the tubes. To ensure proper operation of this type of apparatus, it was necessary to subject the material to a preliminary cleaning such as immersion in an acid, or mechanical treatment of the surface., Either at the location of the joint, either in the vicinity of the edges, or also in the place of the joint and in the vicinity of the edges so as to ensure not only a clean weld, but also suitable conditions of contact for the arrival of the current necessary for the welding .



   The present invention relates to a welding process which does not depend on any preliminary cleaning or any special treatment of the sheets or other materials to be welded.



   This constitutes a marked advantage in this branch of industry because it results in the elimination of expensive handling and pre-treatment.



   If we consider that the simple mechanical handling of materials of the kind in question, to the exclusion of any treatment, represents

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 an expense of about six francs per tonne, it is seen that the advantages of the present process are in direct proportion to the reduction in the number of manipulations.



   Immersion in acid, blowing with sand, or mechanical treatment of the surface in the vicinity of the edges add to the costs an additional expense of nineteen to thirty-two francs per ton.



   Industrial welding processes are distinguished by the different types of welding obtained, among which we can cite spot welding and continuous welding. Although welds of these types are successfully employed in industry for certain applications, the materials characterized by these welds cannot be used for all purposes, either because of the comparative mechanical brittleness of the welds. hard, or because of the lack of uniformity of said welds. One of the objects of the present invention is a welding process characterized by producing a continuous weld through the entire thickness of the material and exhibiting uniform characteristics over the entire length of the joint.



   Difficulties have also been encountered in industrial plants in handling materials of considerable thickness. Although some industrial processes can be adapted to the welding of materials whose thickness is perhaps six millimeters, they have not been industrially applicable to materials having a thickness significantly more.

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 big. The method and the apparatus which form the object of the present invention can be used effectively for materials of the maximum thickness generally encountered in industrial products such as those which it is desired to obtain by welding.



   The present method and the apparatus which is the object of the present invention can for example efficiently weld materials having a thickness of twenty-five millimeters at a speed of about nine to fifteen meters per minute. This is given simply by way of example and without this implying a limitation because the construction of the machine and the variable current supply make it possible, between certain limits, to obtain different welding speeds in a satisfactory manner. - health with different thicknesses of materials.



     Until now, a technical difficulty has been encountered when it is desired to produce substantially straight tubular objects, that is to say non-bent objects. To the knowledge of the Applicant, it has been impossible to produce, by means of known methods, an object sufficiently straight not to require a subsequent straightening to rid it of curvatures. It seems that this is due to two main factors. One factor was the relatively large area of the final object which was subjected to appreciable heating and the other was the relatively low rate at which the end-to-end heating occurs. .

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   In accordance with the present invention, a weld can be carried out under conditions such that the heat is concentrated almost entirely on the joint so that the greater tendency to expand affects too small a percentage of the total metal present to prevent it. - remove the latter, in a very appreciable way, from / to its initial alignment, the welding being carried out / part determined at a speed such that one can achieve substantially uniform temperature conditions along the joint as regards their effect on the shape of the object.



   The present process and the present apparatus can, from an industrial point of view, be characterized by the following points:
1 - Complete absence of prior cleaning or prior treatment of the material;
2 - Continuity or uniformity of the weld across the entire thickness and length of the joint;
3 Efficient welding of materials regardless of their thickness, within certain limits;
4 - Obtaining of objects substantially free from bending or from deformation due to the welding temperature.



   Advantageous results are obtained in the directions just indicated by supplying current by induction instead of supplying current by contact.



   In the contact welding process in which mechanical or electrical contact is necessarily established between the materials to be welded

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 and a suitable conductor, there is a very appreciable and variable loss of current during the performance of the seam weld. This is true whether the contacts move with the material or not, because different contacts are applied to parts of the surface having different conductivities and because the individual contacts themselves, when they can occur. move with matter, are separated from each other.



   This necessarily results in different temperature conditions at different times and at different points, which leads to an irregularity or an absence of uniformity in the nature of the weld. In addition to the undesirable results which have just been indicated, all contact welding processes, whatever the nature of the contacts, have the disadvantage that, owing to the resistance normally greater on the path between the contacts. contact elements (path on which the seal is placed and that of the return path through the tube, a large part of the energy supplied is wasted in heating the rear part of the tube.



   In practice, this quantity varies inversely with the diameter of the tube being welded so that the total energy losses in the return path and the loss between the tube and the contacts taken together represent a very important part. - bearing if not the most important part of the energy supplied. These disadvantages are added to the fact that, in an industrial apparatus of the type that has been built up to now and which depends on

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 the use of a lead. of current by means of one or more contacts, it was not possible to weld in a continuous way tubes whose wall thickness was not greater, if it was, than from five to six millimeters.



   By bringing the heating current by induction, as has been said above, the drawbacks and the difficulties encountered so far, with regard to contact soldering devices or for resistance soldering proper said, either by short arc welding = clear, which will be discussed later, are avoided.



   The present invention, although not limited to the method according to which the edges of the pieces to be welded are placed against each other and an electric current is passed from one piece to another, which method is referred to in this memory by the expression "short arc welding xx is particularly appropriate to this process although it can be considered as a combination of short arc welding xxxxxxxx and resistance welding proper, at different successive points along the entire length of the material to be welded as said material moves in a continuous motion as will be described later in more detail.



   Short arc or flash welding, which is characterized by the formation of a relatively short flame extending substantially uniformly over a considerable portion of the length of a workpiece, is the best tending process to be obtained. quickly a uniform state of the edges.

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   An arc proper tends to concentrate its action on one or on relatively small points and has the drawback of burning the part to be welded at these points. On the other hand, welding by short arc or flash tends to eliminate all the irregularities of the surface by a rapid equalizing action and results in the achievement of a substantially uniform state of the edges. This makes it possible to employ short arc welding without careful preliminary treatment or cleaning of the edges of the material. On the other hand, if such a material having irregular edges were subjected to the resistance welding proper, there would obviously be resistance without uniformity at different points along the length which would generally prevent the production of a uniform joint. .



  Short arc or flash arc welding also consumes half of the electrical energy expended by the resistance welding itself or allows the welding to be carried out at double speed for the same current consumption.



   Arc, short or flash welding is characterized by the fact that it heats the points rich in carbon. It therefore allows the welding of plates of non-uniform width and the welding of plates are the carbon content is not uniform.



   In short arc or flash welding as it has hitherto been carried out, current of extremely considerable intensity at low voltage was required which was brought into the workpiece by 1! one side of the joint and that we leave

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 knows how to flow on the opposite side through extremely thick contacts which were applied with relatively high pressure to the surface of the metal.



   It will also be noted that any contact welding process, whatever the construction or organization of the contacts and whatever the material used, liquid or solid, is characterized by a very considerable current which penetrates into the contacts and by a current flowing out of the contact to penetrate the material, an enormous amount of heat being dissipated as it passes through the thick water-cooled contacts from the metal in the vicinity of the gasket. All these drawbacks have heretofore necessarily limited the application of contact welding to currents of relatively low intensity and have, therefore, limited the thickness of the material which could be successfully welded by said method.



   In the use of an induction welding apparatus, on the contrary, the only limit to the intensity of the currents which can be applied in the material for the bouder is that determined by the capacity of the material. device itself.



   In the accompanying drawing, certain preferred embodiments of the present invention have been shown, by way of example only.
Figure 1 is a view, partly in elevation and partly in section, of one embodiment of the present invention;

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FIG. 2 is a plan of the apparatus shown in FIG. 1;
Figure 3 is an end view of the apparatus shown in Figs. 1 and 2, some parts being deleted for clarity;
Figure 4 is a cross section along IV-IV of fig. 1, some parts being shown in elevation;
Figure 5 shows in section the details of a preferred form of construction of forming rolls;

   
FIG. 5a is a view similar to FIG. 5, but showing the parts in the locked position;
Figure 6 is a side elevation
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 fijàa n of the preferred form of execution dnεùàk A tzxzs- Fte1a;
Figure 7 shows, on a larger scale, the details of a modified embodiment of the present invention, whereby the nearly molten material is confined to the exact point where the joint closes;
Figure 8 is a side elevational view of another form of apparatus constructed in accordance with the present invention;
Figure 9 is a vertical cross section, along IX-IX of fig. 8, seen in the direction of the arrows;

   
FIG. 10 is a cross section along X-X of FIG. 8 seen in the direction of the arrows; Figure ll is a cross section

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 according to XI-XI of fig. 8, seen in the direction of the arrows;
FIG. 12 is a section showing certain details taken along XII-XII of FIG. 8, said section being viewed in the direction of the arrows;
FIG. 13 is a plan of part of the apparatus shown in FIG. 8;
FIG. 14 is a horizontal section along XIV-XIv of FIG. 8, seen in the direction of the arrows;
FIG. 15 is a transverse vertical section on a larger scale, along XV-XV of FIG. 8;
FIG. 16 is a partial longitudinal section, on a larger scale, of a pipe which is being welded;

   
FIG. 17 is a detail view along XVII-XVII of FIG. 16;
Figure 18 is a section, on a larger scale, of one of the windings;
Figure 19 is a perspective view, partially broken away, of a modified embodiment of the present invention;
Fig. 20 is a schematic view which shows the repellency effect which occurs as a result of the use of an inner coil;
FIG. 21 is a detail view showing another embodiment of internal winding;

   
Figure 22 shows a third embodiment of an internal winding, the sections

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 being in greater number;
Figure 23 is a cross section, on a larger scale, through the assembly / of an inner core and the inner coil, taken XXIII-XXIII of fig.1;
Figure 23a is a plan of part of one of the protective elements of the inner core and winding assembly;
Figure 24 is a plan of the underside of one of the protective elements of the inner core and winding assembly;
Fig. 25 shows details of one embodiment of the mechanism for leveling the joint;

   
Figure 26 is a plan of one embodiment of the drive mechanism;
FIG. 27 is a detail section on XXVII-XXVII of FIG. 26;
Figure 28 is analogous to fig. 25 and shows a different embodiment of the present invention;
Figure 29 is a vertical section of a slightly modified form of the inner core and winding assembly ,,
FIG. 30 is a cross section along XXX-XXX of FIG. 29;
Fig. 31 is a plan of a roller guide part / strip duxxxxxx shown in Figs. 29 and 30;

   
FIG. 32, finally, is a section showing in detail one of the roller casings shown in FIG. 29

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While induction soldering can, in accordance with the present invention, be achieved by use of internal cores - or)
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 external and / by the use (m '.t, $,' ,, ', .n, j of windings, the characteristic results which one obtains from the different types of machines are entirely different.

   Under the temperature conditions to which the material must be subjected while it is being raised to the temperature at which the weld is effected, there is evidently a tendency for the molten material and (or) the gaseous material to flow. ,
It has been found that the flow thus produced can be electrically controlled so as to produce at least a main stream of molten metal, vapors and impurities to the exterior, so that the seal is properly free of any. foreign matter, that the impurities are transported to the outside of the object to be manufactured and that a clean seal is ensured. This object is achieved, in accordance with the present invention,

   by using an inner winding constituting a conductor for the current and by using the material which is welded as a movable secondary for this winding so that when the metal of the seal is heated to the point of fusion, xxxxxxxxxx and vaporized under the influence of the temperature reached, a magnetic repulsion occurs between the inner winding acting as one of the conductors and the metal vapor of the gasket acting as the other conductor. from an industrial point of view, this results in a marked advantage over welding devices built and

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 and used until now ,.



   These different characteristics will be discussed in detail in the following, in order to provide a clearer and more complete explanation of the present invention. For this purpose, first examine Figures 1 to 7 and Figures 21 to 24 of the accompanying drawing.



   In the preferred embodiment of the present invention, the welding is carried out entirely inside or between two sets of knurls. In order to produce these two sets of knurls, two main frames designated by 2 and by 3 are used. , in what follows, will be called housings. The two housings are generally the same construction) the details of one of the housings being shown in fig. 4.

   This figure shows that the housing, preferably constructed of steel, is of a special construction designed to withstand the enormous stresses to which it is subjected. is submitted, and that it is organized, so as to. present a series of openings 4- intended to receive knurls, these openings facing the axis of the casing. Between these openings there are supports 5 of any suitable construction to cooperate with the ends of the shafts 6 which rotate within said openings.



   Around each of these shafts is an eccentric sleeve 7. All these sleeves which have, in general, the same construction, except the two which cooperate with the shafts 6 arranged in the upper part of the housing, on either side of the axis of symmetry of said casing, comprised bevel gears 8 fixed to one of the ends

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 mites of said sleeves and forming, preferably, integral with them, the other end of these sleeves bearing bevel gears 9 preferably mounted on the back of removable collars screwed in place on the aforementioned sleeves; suitable wedges 10 prevent accidental detachment of said pinions.

   As seen in fig. 4, these pinions mesh with each other, so that the rotation of one of the sleeves ensures the corresponding rotation of all the sleeves.



   This rotation can be obtained by mounting inside each of the housings a shaft 11 carrying at its end turned towards the inside a bevel gear 12 meshing with the pinion of one of the sleeves 7, said shaft 11 carrying at its outer end a helical wheel 13.



  With the latter, cooperates an endless screw 14 which can be turned in any desired way, for example by means of a handwheel 15.



   This flywheel may be provided with teeth or notches 16 capable of engaging with a fixed pawl, a rack or any other retaining member 17 which prevents accidental movement from a fixed position and adjusted in advance.



  The organization described shows that the rotation of the flywheel 15 causes a corresponding simultaneous rotation of all the sleeves 7 in one direction or the other.



   On each of these sleeves is mounted a shaping wheel 18, all the wheels being of similar general construction. Except the two knobs at the top of each of the

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   / glazed 'casings / on either side of the axis of symmetry, said wheels are provided with teeth 19 and 20 on each of their faces, (the two upper wheels only having teeth at one of the = faces) thanks to which all the knurls can mesh with each other, as do the corresponding sleeves.



   Due to this organization, the rotation of one of the shaping wheels causes the corresponding and simultaneous rotation of all the wheels. This rotation can be caused by a control shaft 21 mounted in each of the housings, preferably opposite the adjustment shaft 11, said shaft 21 being mounted in suitable supports. Each of the control shafts carries at its end facing inwardly a control pinion 22 meshing with the teeth of one of the shaping wheels.

       at its other end, the control shaft can be provided with a helical wheel 23 capable of being controlled by means of a worm 24, from any suitable source of energy, such as than an electric motor, not shown. it is of course understood that the worms of- ':

   24 of each of the two housings can be controlled either from a common shaft or from separate shafts, as desired. however, in most cases the shaping wheels are operated at substantially equal speeds, making separate controls unnecessary. '
Construction of cogwheels 19
20 and 22 allow a certain relative radial displacement

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 tif between said gears, this relative displacement being sufficient to allow the simultaneous adjustment of all the shaping wheels, by moving towards or away from the axis of the casing, thanks to the rotation of the eccentric sleeves 7, as has been said upper.

   The machine thus formed comprises, in each of its casings, five shaping wheels capable of simultaneously rotating in the same direction and capable of being adjusted simultaneously by moving towards or away from the axis of the casing, which enables them to receive objects of different diameters, this organization making it possible to vary at will the degree of pressure applied to the material as well as the final diameter of said objects.



   The sleeves 7 and the shaping wheels 18, which are located in the upper part of each of the housings and on either side of the line of symmetry, do not differ from the point of view of their construction from the other corresponding parts only by the fact that their neighboring ends can be separated from each other and may not mesh with each other, as is clearly shown in Figure 4. This organization creates a space S which, during the operation of the apparatus, interrupts the continuity of the conduc- / circuit while a tor which constitutes the mischief continuous circuit which would be established if all the sleeves and all the modules 1 meshed at this point. This interruption of the circuit is particularly important, as will be seen below.

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   In the foregoing only one of the housings has been described in detail, but it is clear that the housings can both be of a generally similar construction and that they can be adapted to function in the same way. way. The description of this housing will suffice.



   Between the housings 2 and 3 there is a frame or frame 25 ', the details of which are shown in FIG. 6, said frame comprising rollers 26 in any desired number which serve both as holding members for the article to be manufactured and as pressure members. The frame 25 is constructed in such a way that the passage that the rollers 26 dare can be widened or reduced by contraction or expansion of said frame. This adjustment may be achieved by the use of a split or resilient frame, such as that shown in FIG. 6 and by mounting a rod 27 provided with two xxx threads in opposite directions, which engage with the respective parts of the frame.

   Thanks to this construction, the rotation of the rod 27 - in a certain direction brings the rollers 26 closer to each other, while the rotation in the opposite direction; -: separates them from each other,
Although the split or resilient frame which has just been described is effective in making small adjustments of the retaining rollers 26, arrangements must be made to be able to adjust, between greater limits, said rollers when the diameter of the objects to be welded changes in a significant way.

   The construction shown in FIG. 6 allows to realize

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 this adjustment by the block removal of the retaining rollers 26 as well as of the bearings 26 'on which they are mounted and by the interposition of wedges of an appropriate thickness or of a spacing member between the sole of the bearings and the bases 25 'provided for these bearings on said frame, by interposing wedges or spacers of uniform thickness behind each of the bearings, the desired spacing can be maintained between all the retaining rollers .



   At the top of the housings 2 and 3 / -or carcass is placed a laminated iron cylinder head which extends continuously through said / into housings, / a plane situated between the shaping wheels upper 18 of the corresponding housings.



  / With this cylinder head cooperates a pole piece 29 which, preferably, is also laminated and which is provided with a central opening of a diameter a little larger than the maximum diameter of the material - / With tem to be welded in the apparatus. At this central opening of the pole piece 29 'cooperate individual pole pieces 30 which all protrude towards the real axis of passage between the shaping knobs of the housing 2 as can be seen clearly in FIG. 1.

   It has been found that very advantageous results are obtained by constructing the individual pole pieces so that they act to produce a magnetic circuit which penetrates sharply into the area bounded by the outer periphery of the rollers in such a manner. - swimming 18 due casings 2.



   Such a construction and such an arrangement

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   Management of organs are desirable, as will be indicated in the following. Fig. 3, however, shows that these individual pole pieces 30 constitute a substantially continuous magnetic circuit which cooperates closely with the exterior of the material M worked in the apparatus.



  When you want to use. the apparatus for materials of relatively short length, the applicant preferably uses a second pole piece 31 similar to the pole piece 29 but arranged on the side of the inlet of the housing 3. This pole piece has, in a similar way, a central opening of a diameter greater than the maximum diameter of the material to be worked and it carries an internal covering laminated 32 so that said tibia piece of directly receiving the material M without / - polar can come in contact with it.



   Due to the well known fact that the magnetic flux, when it enters the lamellae in a direction perpendicular to their surface produces harmful heating, the Applicant preferably provides, in the cylinder head 28 (and in the alignment of the parts poles 29 and 31), a series of plugs 33 characterized by lamellae arranged and organized so that the magnetic flux passes continuously through the magnetic circuit formed, always entering and leaving, in all slats / by the edge.



   When the apparatus is constructed for its application of relatively long parts or for continuous welding operations, the pole piece 31 and the parts can be completely omitted.

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 those who cooperate with it. In this case, the yoke 28 can be extended rearwardly in the form of a laminated metal beam 34, disposed in cantilever and suitably supported by struts 35 supported on the casing 3, this beam 34 having a suitable construction to achieve the desired extension of the magnetic circuit constituted by the yoke 28 / said extension in laminated metal descending to a central core 36 and forming a body therewith.



   It clearly follows from the above that the Expressions "continuous welding" and "intermittent welding" used above, do not define different characteristic operations but that these expressions refer to the relationships of these operations with the material treated. The word "intermittent" as used in this specification refers to the working of objects of limited length, while the word "continuous" refers to the welding of objects longer than the pipes found on the market.



   When the pole piece 31 is to be used, the beam 34 is constructed entirely taking into account the mechanical load that it must withstand and not by considering the constitution of a magnetic circuit. In this case, the connector plates 37 may be of a non-magnetic material so that a closed magnetic circuit does not form between the beam and the interior assembly 36 the details of which are shown in Fig. 23. Said assembly then comprises in

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 / further interior, a pole piece / 39 located approximately in the plane of the ends of the individual pole pieces 30.

   In this construction, the magnetic circuit passes successively through the pole piece 39, through the individual pole pieces
30, by the pole pieces 29, by the carcass
28, by the pole pieces 31, by the coatings 32, by the inner pole piece 38 and by the core of the winding. As seen in fig ,,, l, this circuit comprises two air gaps each of sufficient dimensions to receive the material to be welded.



   But, when it is desired to carry out the continuous welding, which does not depend on the use of the pole pieces 31, 32 and 38, these pieces can be completely omitted and a magnetic circuit can be established directly at the input. of the apparatus, between the beam 34 and the interior assembly, by a construction such as that mentioned above.

   This arrangement improves the operating conditions in that it constitutes a magnetic circuit having only one air gap, that which necessarily exists between the individual outer pole pieces 30 and the inner pole pieces. :; 39. A coil 40, co-operating with and carried by the inner assembly, which coil may be provided with suitable conductors not shown, may extend rearwardly through the assembly and be connected. to a suitable source of electric current, not shown.

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  The current, however, comes from a low voltage source of sufficient power for the induction welding contemplated here.



   Thanks to the Gustation described, a curved piece of material M substantially in the shape of a tube can be brought into the apparatus, above the interior assembly and below the beam 34, in the path of the knurls so- housing 3. These knurls act in some cases to force the tube to take uniform dimensions or to bring the opposing edges of the material to the desired distance or in the immediate vicinity of each other. while preferably preventing said edges from coming into contact with each other. The material then passes through the passage between the adjustment rollers 26 which can be adjusted so as to maintain the suitable distance between the edges.



  During this time the material moved over part of the coil 40.



   As it continues to move, the material passes over the remaining part of the winding 40 as well as over the inner pole piece 39 and enters the plane of the axes of the casing shaping wheels 2. These The rollers act to continue to deform the material and to bring the edges into firm contact with the pressure conditions necessary to achieve the desired weld.



   -In practice, the spacing of the organs can be such, for example, that the edges come into contact with each other at a point between

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 the rollers 26 and the plane of the axes of the shaping wheels of the casing 2. On first contact with the edges, assuming that the winding 40 is energized, a short-circuit is established in the material M which constitutes a mobile secondary.



  This results in a very short arc which tends to move or extend rearwardly a very appreciable distance along the joint. The conditions tending to strike this short arc having been created, it is kept uniform in space / displacement whatever / the duration and for the duration of the displacement of the material, towards the having, through the machine.



    / backwards Between the actual point of contact / and the point from which the short arc does not occur extends an area which can be designated by the expression "short arc area" while that between the point where the first contact occurs and the plane which encloses the axes of the shaping wheels of the casing 2 exists what could be called the "resistance heating zone" zone in which the edges, heated at soldering temperature, are in intimate contact. By the appropriate adjustment of the rollers 26 the short arc zone and the actual distance between it and the resistance heating zone can be varied.

   The separation between the edges in the short arc zone leads to a greater drop in potential and therefore a greater expenditure of energy in the joint itself than in the case of resistance welding. ordinary.



   The greater the interval between the edges provided that the arc is not extinguished, the greater the

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 the drop in potential across the gap is great and the greater is the fraction that this drop in potential represents compared to the total electro-motive force created in a revolution of the mobile secondary. This being the case, the interval consumes an all the greater fraction of the total energy consumed per revolution of the secondary and the power losses through the return circuit formed by the metal represent an even smaller fraction of l total energy consumed as long as the diameter of the pipe in question is not greater than 60 to 90 centimeters.



   This being admitted, it is clear to those skilled in the art that so, to say, all of the current flowing through the pipe represents current actually consumed for the weld, with the potential drop across the gap acting as a re-factor. control for the trality of the current. This is completely different from the old resistance soldering process known as "contact soldering" in which the flow of current through the return circuit is not directly limited by the drop in potential which occurs across the joint and in which the current in the return circuit can reach enormous values which represent entirely permanent losses.



   It is obvious that if the shaping wheels were in continuous contact with each other all around the pipe, they would also constitute a part of the secondary and, for this reason, they would also be subjected to harmful heating. sible. This warm-up would not only be

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 harmful from the point of view of the installation itself but also from the point of view of the enormous losses that this heating would represent.



     The existence of a winding within the material to be welded is extremely desirable not only from the point of view of the operation of the welding apparatus but also from the point of view of construction. The characteristics relating to the weld will be examined first with reference to Fig / 20 of the accompanying drawing. This figure shows the material M with its neighboring edges m and m 'slightly apart, this figure representing conditions such as those which exist in the area mentioned above. In this zone the heating is such that it brings the temperature of the material to a point where a part of said material is vaporized.

   This vaporized metal acts as a secondary conductor which is; away from the coil 40 which constitutes a primary conductor and in which the current passes in the direction opposite to that of the current induced in the vapor.



   This being the case, a magnetic repulsion takes place between the two conductors. Due to the fact that the conductor formed by the winding is not free to move, the vapor V is pushed back outwards in the way that a shown in Fig. 20 to an extent which is determined by repellency, the latter having. has been found in practice to be large enough to effectively rid the heated seal of all foreign matter so that when

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 the edges are then brought into contact with each other, there is nothing to prevent the formation of a substantially perfect joint.



   This discharge of the steam to the outside has the clear advantage of completely freeing the edges, which must be assembled to form the seal, of all impurities, whereby when said edges are finally brought into contact. with each other to form the seal, the latter contains only pure metal. This obviously contributes in a very substantial way to the production of a weld which is not only more perfect, but which is also more substantially uniform throughout. The further advantage of this is that a zone is formed before the final closing / short arc closing of the joint, since an operation characterized by keeping the edges in continuous contact necessarily prevents the production of repellency. outward repulsion which produces an effective cleaning effect.

   It does not seem that it has been proposed, until now, to mount a coil inside a pipe and to use the characteristic action of this coil to clean the joint and to remove impurities. . It is clear that this effect could not be obtained in an apparatus which would only use an internal core, since a core simply constitutes an organ carrying flux while a winding constitutes an organ exerting a dynamic function. , that is, an organ which xxxxx produces a real flow. The intensity of repulsion increases with

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 an extreme speed when the two 'conductors are brought together and this intensity decreases when the conductors are separated from each other.

   When there is any appreciable distance between the two conductors there is a space (air and metal) of dimensions such that it can receive a significant part of the magnetic flux of the primary conductor and (or) of / are secondary conductor, so that the energy transmission and the repulsion effect are considerably reduced.

   It follows clearly that the immediate vicinity of the primary and the secondary is of capital importance for the supply of a large amount of energy and that two conditions are desirable for obtaining an effective cleaning of the joint. One of these conditions is the formation and maintenance of a large area in which the edges of the material are sufficiently apart to allow the formation and repulsion of vapors and the other condition is the maintenance of a sufficiently small distance between the two conductors so that there is no appreciable or sufficient passage for the losses of magnetic flux.



    Another distinct advantage results from the hand- / short-arcing of this area and the vaporization of part of the metal from the edges neighboring the object to be welded. Those skilled in the art know that the volume of gases generated when the metal is vaporized is about a thousand times greater than the original volume of the metal so vaporized. This volume of; continuously discharged gas, as has been said / overflowing even up to a certain point above

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   the other side of the seal causes a non-oxidizing atmosphere to be maintained so that the formation of oxides and their subsequent inclusion in the seal is prevented.



   In addition, if the vapors moving at high speed could move inward they would condense as they came in contact with the inner coil and the core and solidify on these organs, causing , the formation of a harmful deposit on said assembly.



  By means of the present invention this effect is almost completely avoided so that the need to clean the interior of the assembly is not often present.



   From the point of view of construction, it can be seen that the internal winding occupies a space which cannot be used for other purposes. If the winding were placed outside the pipe, a larger gap would be required between the roll housings and a corresponding increase in the dimensions of the apparatus would result and, consequently, disadvantages and disadvantages. difficulties in the operation of said apparatus. Some of these drawbacks would result directly from the increased difficulty of maintaining the edges of the tube at the desired spacing so that the zones and resistance can be set accurately / shortly.



   If desired, the internal assembly can be provided with rollers 44 and 45, the pins 46 and 47 of which are slightly offset from each other, as seen in FIG. there, where we

  <Desc / Clms Page number 30>

 may provide other equivalent organs capable of being adjusted to increase or decrease the total space they occupy. These rollers preferably act substantially in the plane of the axes of the shaping wheels 18 and are arranged so that the roller 44 lies directly below the joint and tends to produce a smooth internal surface of the material to be welded.

   In practice, it is preferable to construct these rollers of a non-magnetic material, such as non-magnetic steel, although satisfactory results have been obtained with rollers of ordinary gray cast iron.



   Although there is not an abrupt interruption of heating when the material having / the plane of a heated seal has protruded from the pole pieces 30 and 39, there is a marked drop in this plane of the heat generated in. the pipe, The heat losses by conduction and radiation being continuous, it is obvious that if the distance between the.-point where the metal has its maximum temperature and the point where the solder is heated is too great, the temperature may fall into such proportions that a satisfactory weld cannot be produced.

   By extending the individual pole pieces 30 as shown in the drawing and more particularly in Figure 1, these two points can be brought together in such a way that the desired temperature conditions can be maintained during xx the actual final closure. of the seal. This arrangement of the organs that allows the use of an in-

  <Desc / Clms Page number 31>

 Inner bearing constitutes a considerable advantage of the present invention from the point of view of operation, although this construction is not necessary for the execution of the welds.



   From a practical point of view, it has been found that the arrangement of the members in a welding apparatus, such as that which has just been described, allows the execution of a joint having quite desirable characters. By suitably adjusting the moment of application of the pressure and the value of this pressure, taking into account the duration of the heating (in the case where the heating has been limited so to speak entirely at the edge of the material to be welded ) a joint characterized by a very desirable texture can be produced, the ordinary welding operation, due to the way in which the material has been heated, allows a significant heat trans- mission by conduction through a significant portion of the tube surface.



  It is of course well known that heat causes grain to increase. However, any portion of material heated above the critical temperature has a grain of larger dimensions than the portion which has only been heated to approximately that temperature. The part which has only been heated to approximately the critical temperature has only a grain of a more desirable structure than that of other parts of the same material.



   Due to the extreme rapidity of the heating which is achieved in accordance with the present invention and due to the fact that the short arc xxxxxx limits the action of heat to the extreme edges im-

  <Desc / Clms Page number 32>

 immediately before the actual application of the pressure, the latter may be high enough to expel virtually all the metal which has been heated above the critical temperature, thereby bringing the zones of tran- sition of the material characterized by the fine grain produced by heating to the critical temperature.



  A seal produced in accordance with the present invention, which seal is free of impurities and in which the transition zones are brought closer to each other at the location of the seal, has a higher grain even than the grain of the other parts. of the part to be welded, said joint having for this reason a greater resistance.



   Due to the fact that one takes into account, for the moment, Implication of the pressure and / of the moment and for the value of this pressure, of the way in which the heating was carried out, one can submit the seal, at the moment where o it leaves the shaping rollers 18, by the action of a cooling agent.



  This can be achieved by means of a water pipe w which preferably takes the shape of an arched shoe and which is placed above the joint, said water pipe @ having any desired number of discharge openings. The quantity of water must be regulated in the machine so as not to cool the material at the point of the seal, to a much lower temperature, or even to a temperature lower than the critical temperature, thanks to to which we immediately stop the growth of the grain which gives rise to a real refining.



  -

  <Desc / Clms Page number 33>

 
It is obvious that by means of suitable analyzes it can easily be seen whether the quantity of agent should be increased or decreased.: Refrigerant:.



   The division of the heating zone into an edge weld zone and into a resistance weld zone proper is very desirable, not only for the reasons given above including the fact that the gap determines the strength. - centage of energy supplied to the joint, but also for the reason that a much more powerful and more concentrated heating effect can be obtained (short arc welding for a determined consumption of the energy qu 'it is not possible to obtain by resistance welding proper. Therefore, the shaping wheels in the housing 3 are not generally adjusted to bring the edges of the material to be welded into contact with each other. the other while said material passes through the housings.

   If the edges are in contact or if they are crushed by these knurls they can then separate very slightly for a considerable distance.



  If the edges remained in contact continuously from the passage through the first knurls to the passage through the second knurls, the energy consumption would be about three times and the weld produced would generally not be as satisfactory.



   Due to the different conditions which prevail in the different zones, the Applicant has observed that extremely satisfactory results are obtained by constructing the internal winding in the manner shown more particularly on the figure.

  <Desc / Clms Page number 34>

 / the winding fig.21 on which it has been clearly shown / retort being constituted ,,; by two patties 48 and
49, part 48 having a length generally comparable to that of the short arc zone xxxxxxxx and part 49 being of a length generally compatible with that of the resistance zone.

   Although due to the low voltage of the current used it is not difficult to achieve the desired isolation between the different elements of the winding, the Applicant prefers to wind these different elements so that the neighboring ends of the elements 48 and 49 have the same potential which allows them to be connected to a common conductor 50, while the more distant ends of these winding elements may or may not be connected in the same way to a second common conductor 51.



   One of the advantages of a split winding is that you can vary the amount of energy supplied to each of the different elements, this amount of energy supplied having some relation to the difference between the elements. besoihs the short arc welding xxxxxxx and the resistance welding proper, In other words the split construction allows to put under a slightly different voltage the winding 48 corresponding to the short arc welding and the winding 49 corresponding to the resistance welding proper. Although this organization is not essential for the operation of the appliance, it makes it possible to adjust heating conditions which cannot be achieved.

  <Desc / Clms Page number 35>

 in another way.



   In fig. 22 there is shown yet another embodiment of the winding, the latter being divided into a number of parts or elements
52,53, 54 and 55, much larger. Although in fig. oncn'ait shown that four elements it is clear that the number of these elements can be increased at will so as to make each of the elements act on a relatively smaller area of the material to be welded. Thanks to this division of the winding into elements, each of the elements exerting its full heating effect over a determined unit of length of the material, it is possible to heat the extreme parts of the material to a temperature appreciably lower than the parts. medians.



  For this purpose, it may be desirable in some cases to make the end members 52 and 55 a shorter length than that of the middle members 53 and 54 so that the ends of the material can be maintained at the desired temperature. .



   To further reduce the waste formed by the ends of the pipes, it is possible, if desired, to actually weld the material before it is subjected to a finishing operation. It is known to those skilled in the art that the material which is generally used in the manufacture of tubes ends at both ends with shrunken parts. When the material is welded prior to finishing, the joint can be made at a shorter distance from the end of the material and when the tube is subsequently finished waste is reduced to a minimum.

   It is obvious that the weld pushed as far as possible

  <Desc / Clms Page number 36>

 is of great importance because the waste can reach an appreciable percentage and the advantages of electric welding can be almost completely offset by these losses.



   If we refer more particularly to FIG. 23, it is seen that the whole of the inner winding and of the core presents a special construction with regard to the means used to enclose and protect the active members of this assembly. Due to the intense heat which develops in the seal, it is essential to provide means intended to protect the winding or the winding elements against the action of this heat. This can be achieved by means of an envelope which takes the form of a series of elements 57, which extend in part or completely around the assembly and which are far enough apart from each other so that they do not constitute a circuit conductor closed One of these elements, designated by 58,

   can be placed
 EMI36.1
 / present directly below the weld line and / eg, at certain intervals along its length, protrusions 59 capable of coming into contact with the underside of the material, in the vicinity of one of the edges of said material, protrusions which can prevent any further contact of said edge with the elements of the casing.,
These support points (or protrusions) are preferably inclined in one or the other direction,

   so that they do not constitute shoulders on which foreign matter can gather and their ends 60 are or-

  <Desc / Clms Page number 37>

 arranged so as to have gradually inclined parts over which the material can move during the welding operation.



   It is clear that such support points cannot be considered for the opposite edge of the material as these support points would cause a short circuit directly through the joint. The rigidity inherent in the material is, however, such that by keeping one of the edges away from one of said elements, the desired result is obtained.



   In fig. 24 one of the elements / (it, in the present case is xxxxx the element located directly below the joint, that is to say element 58, has been shown in detail, said element being overturned and partially torn off to give a better understanding of the construction To the lower surface of this element are fixed two water-circulating refrigeration tubes 61, welded or otherwise held in place to ensuring efficient heat transmission between said tubes and said element All water circulating refrigerant tubes have the general shape of a hairpin so that cooling water can pass from the end one of the elements at the end of another element.

   This is made possible by the fact that suitable inlet 62 and outlet 63 ports can be connected to a source of cold water.



   The construction of each of the shaping wheels is preferably such that the rim or working part 64 of said wheels can be easily removed without the need for disassembly.

  <Desc / Clms Page number 38>

 machines. This can be achieved by constructing rims in substantially semi-circular shaped elements. Each half-rim can be held in position by means of a screw 65 serving both for tightening and for blocking said screw having a portion 66 threaded in a direction to engage with the rim element. anda portion 67 threaded in the opposite direction to engage the main body of the wheel.

   The middle part has a larger diameter and is provided at its periphery with teeth 69. capable of engaging with a special tool.
70 that can be introduced 4 through an opening
71 made in the periphery of the rim. This opening can be closed normally during the welding operation by a plug 72, a locking pin 70 'being introduced to replace the tool 70 to prevent unscrewing of the components.



   Thanks to this construction, it is possible at will to remove any rim element and replace it with a new rim element. This not only makes it possible to quickly replace worn rim components but also to replace them with other rims having different outer diameters.



   In fig. 7 shows an embodiment slightly different from the present invention in which the members which correspond to the members already described are designated by the same reference numbers assigned an index (′).



   One shows in this figure, in elevation 'seen by the end, a cylinder head 28' and a shaping wheel
18 'arranged on each side of the cylinder head. Line

  <Desc / Clms Page number 39>

 a-b crosses the center of the passage between the knurls and is in the median plane of the cylinder head 28t. Note that the shaping wheel 18 'shown to the right in said figure is shaped so that it stops at an appreciable distance from one side of the line ab, while the shaping wheel 18 ', on the other side, is shown with an extension 73 which goes beyond said line ab and which therefore extends above the line which forms the joint.

   This arrangement cooperates with the inner roller 44 'to form a closed passage where the pressure is applied at the time of welding, whereby the amount of plastic material which can be expelled by pressure is regulated. in a definite way.



   This closed passage makes it possible to apply much greater pressures and, thanks to this fact, to achieve a better seal in all conditions. The greater pressure tends to subject the hot metal to some work and gives the resulting joint a grain of fine structure.

   It is understood that this wheel of varied shape is only used in the casing 2 ', on the side of the outlet of the apparatus.
In fig. An embodiment of a mechanism is shown which can be used if desired to scrape and completely remove excess molten metal thrown outwardly from the joint but still adhering to neighboring edges. of the joint This mechanism, as shown, comprises a support member 74 in which is mounted a series of blocks 75 intended to scrape and remove.

  <Desc / Clms Page number 40>

 clean the manufactured object, these blocks preferably being of an abrasive material resistant to high temperature, such as "carborundum" or the like.

   The length of the support member 74 can vary at will and the terminal blocks 76, in the case where the support has a sufficient length to extend from the shaping wheel 18 of the housing 3 to the end. shaping wheel 16 of the casing 2, can receive a shape such that they are placed in the immediate vicinity of the peripheries of said wheels.



   As the material moves under the blocks 75 these act to remove any lateral deposit of molten metal which has been expelled, the removal occurring as quickly as the forcing of said metal out of the joint under the influence of magnetic repulsion. to lamella it was alluded above
The member 74 can 'be supported by an arm 77 pivotally mounted at 78 on a suitable consale 79 applied to the anterior part of the casing /. - The other end of this arm is connected by a connecting rod 80 to a lever elbow 81 pivotally mounted at 82. This elbow lever has a groove 83 in which engages a finger 84 fixed to the connecting rod 80 whereby, when one oscil is made.



   1st the angled lever 81 counterclockwise, said connecting rod 80 can be moved through a line which unites finger 84, pivot 82 and pivot 85 serving to articulate connecting rod 80 on lever 77. In this posi- tion, the components are blocked and prevented from disengaging.

  <Desc / Clms Page number 41>

 accidentally place.



   As it is preferable to mount the member serving to scrape and clean the seal so that it exerts an elastic pressure, the angled lever 81 is provided with an extension 86 having a curved seat 87 which carries a pad. elastic 88, with which cooperates a spring blade 89 which can be clamped and held in position by a fishplate 90 into which the threaded ends of the stirrups 91 penetrate.

   When the nuts of these calipers are loosened, the elastic bearing 88 can move in one direction or the other so as to carry out the corresponding adjustment µ the leaf spring 89 and consequently to ensure the effectiveness of its action. on the mechanism intended to scrape and clean the seal
Due to the extremely high temperature in this location, the blocks of abrasive material would be quickly eroded or worn away if the marl which had formed part of the abrasive material were allowed to always come into contact with the hot metal:

     To overcome this drawback, a support 92 can be provided to which can be fitted a suitable mechanism, not shown, intended to cause the member which scrapes and cleans said joint to oscillate in a direction transverse to the plane of the joint, whereby parts Continuously new blocks of abrasive material are brought into operation.



   The preferred embodiment of the present invention which is shown and the embodiment which will now be described show an assembly.

  <Desc / Clms Page number 42>

 internal winding comprising both a winding and a core. This embodiment is preferred in most cases because of the better magnetic circuit provided by the inner core.

   In the case of fairly wide pipes; for example of a diameter of 0.60 meter: or more, one can, if desired, eliminate the internal net core because the free space which presents pipes of such a large diameter, has a sufficiently reluctance great for the passage of magnetic flux.
 EMI42.1
 The a6n.srt: rúoion which comes from tred6ctite is also recommended when using alternating current. It is quite obvious, however, that currents exhibiting any periodic variations, whether alternating current or a pulsating current in the same direction) can be used if desired.

   However, in all the cases where a pulsating current is used, the core and the yoke necessarily have a section greater than that which is necessary for an alternating current of the same frequency.



   We will now refer to FIGS. 8 to 18 to describe another embodiment of the present invention. In this embodiment, the welding apparatus comprises a base 93 of any desired construction on which are mounted supports or housings 94, 95 and 96 carrying wheels.

   These supports are designated respectively in what follows by the expressions “supports for the knurls intended to effect the preliminary closing”; "supports for the knobs intended to adjust
 EMI42.2
 the short arc BBtxiH # 'He and he supports the knurls

  <Desc / Clms Page number 43>

 intended to complete welding or closing "
The support 94 of the pre-closing rollers carries a series of rolls 97 mounted on shafts 98 forming a certain angle between them and which are supported by suitable bearings 99 provided in the support or housing containing the rolls. These rolls cooperate with a lower roll 100 suitably attached to a shaft 101 which extends transversely through the housing.

   The opposite sides of the housing are constructed so as to leave some space at their upper ends as can be seen clearly in fig. 9; said sides can be moved closer or further apart by an adjustment screw 102 which is effective in modifying slightly the diameter of the passage between the shaping wheels.



   The knurls and the casing as well (-that the bearings of the knobs are constructed so as to leave a continuous open space 103 which extends from the center of the passage between the knobs, passing between the upper ends of the casing, to arrive at the plane of the adjustment member 102, for the purpose which will be indicated more fully in what follows.



   The shaft 101 can be mounted in bearings 104 which can be adjusted in height and supported by adjustment screws 105 by means. of which the bearing beds can be mounted lowered at will to leave between the shaping wheels a passage of exact dimensions required.

  <Desc / Clms Page number 44>

 his. The adjustment screws can be locked in their position by means of nuts 106.

   To control the shaft 101 -on can provide the latter, at one of its ends, with a bevel pinion 107 meshing with a more or less similar pinion 108 mounted on a shaft 109. This shaft extends from preferably in the length direction of the apparatus and can be controlled by a motor 110 by means of a suitable speed reduction device 111. The motor can be of any construction or type, but it is preferably of the variable speed type, the speed being controllable by suitable regulators 112.

   In order to actuate the knurls 97, they can be constructed with teeth 113 coming with said knurls and capable of meshing with teeth 114 forming one unit with the lower wheel 100 as can be clearly seen in FIG. 9.



   The knobs 97 and 100 can be adjusted in position from the start, relative to the diameter of the pipe P to be welded, so as to bring the spaced edges 115 of said pipe into contact with each other or in the vicinity. immediately from each other as desired when said pipe passes between the knobs.



   The support 95 carries two similar housing elements 116 each carrying a substantially vertical shaft 117 on which wheels 118 turn intended to act on the two diametrically opposed sides of the pipe. The housing elements shown are supported at their lower end by appropriate pivots 119 and cooperate at their

  <Desc / Clms Page number 45>

 upper part with a / 3 adjustment member 120 similar to the adjustment member 102 described above.

   It is clear, to those skilled in the art, that instead of mounting the elements of the housings 116 on pivots, they can be constructed in a manner analogous to that of the supports of the preliminary closing wheels so that one can adjust them, within the limits necessary for the proper adjustment of the knobs 118, taking advantage of the elasticity of said housing or support. These knobs are adjusted in a normal fashion with respect to the diameter of the pipe to be welded so as to allow the edges 115, in
 EMI45.1
 / come in the event that they are while they pass through the passage between the knurls of the first support or casing, to move away slightly as indicated in fig. 10, for the purpose which will be explained later.



   The support or casing 96 for receiving the knurls for the final welding or closing is preferably of analogous in construction as a whole to that of the support or casing of the knurls which performs the first closing and closing. Organs corresponding to those already described with regard to this first support or casing are designated in what follows by the same reference numbers assigned an index (′).



   From the description which has been given of this modified embodiment of the present invention, it follows that the support or casing for the knurls intended to effect the first closure generally corresponds to the casing 3 and to the casings. - ganes associated with said casing; -that 'the crankcase

  <Desc / Clms Page number 46>

 or support 96 for the wheels intended to complete the welding and the closing of the tube corresponds to the casing 2 and to the members associated with it and that the casing or intermediate support in which the short arc is adjusted generally corresponds from the point of view of its construction and function to the support frame 25 and the members which are associated with it.



   However, it follows from the operation as described that, in the operation of this embodiment, the material is generally subjected to actual compression to a sufficient degree in the passage between the knurls effecting the compression. first closure so that the edges of the pipe are brought into direct contact with one another, that;

   in the operation of the embodiment shown in fig. 1, it is envisaged, under the usual conditions that the edges are kept apart from each other although these conditions, can be reversed, if desired, in the two constructions 0 '
In another embodiment which has been tried in practice and which is shown schematically in FIG. 28, the casing 3 in fig. 1 is placed outside or in front of the pole piece 31 of laminated iron, so that the first closing (or (crushing) effected on the pipe can be performed totally outside the magnetic circuit as a simple mechanical operation which, incidentally, allows the pipe to be advanced with great force.

  <Desc / Clms Page number 47>

 



   The sections of the pipes prepared for supply to the apparatuses shown in fig. 8 to 18 preferably have a shape similar to that shown in FIG. 9 of the drawing and presents a bump 121 arranged diametrically opposite the plane where the edges 115 meet.



  If the pipe is closed during its passage between the knobs intended to effect the first closure / it has a tendency xx to open by elasticity when the pressure of these knobs is released, the degree of opening being regulated by the knobs 118 of the support or housing for the knurls between which the short arc xxx air is adjusted. As a result, when the pipe passes through the support or casing of the rollers effecting the initial closure, the edges are generally brought into contact, this contact then being broken to the extent that the initial adjustment of the rollers intended to adjust the arc allows. short xx flash.

   As described above, the quantity of energy supplied to the joint which is welded is determined by the size of the space between the edges 115, a quantity which is determined by the knobs intended to adjust. the short arc xx xxxxx and, although it is desirable to increase this percentage of energy as much as possible between the capacity limits of the apparatus, this space should not be taken too large for two reasons.



    In the first place, if the space is large enough, the characteristic short arc xxxxxx disappears and the result is a proper arc, the action of which is harmful due to its local action.

  <Desc / Clms Page number 48>

 On the other hand, when the space is too large, it frequently results in the complete rupture of the short arc xxxxxxx.



   It is also evident that, although we have. for simplicity, shown in the drawing a single wheel casing to adjust said short arc xxxxxxx, the number of these casings can be increased at will and the individual casings can be placed at a certain distance from each other at different locations desired along the length of 1 device.



   Between the two supports or housings 94 and 96 and insulated in any way with respect to them, extends a laminated carcass 122 of magnetic material. -If desired, this carcass can be made rigid by a massive central bar 123, although this form of construction is not essential. The carcass 122 can be fixed to the support or casing of the knobs intended to firstly close the tube, '-, by means of elastic plates 124 or any other equivalent devices which allow the supports or housings to be slightly adjusted in the manner of - already written, without making any changes to the way in which the carcass is supported by said housings or supports.

   Similar members 125 can be used to support the carcass in the vicinity of the support or casing 96 of the knobs which complete the closing or welding. The
30 construction must however make it possible to maintain a determined position between the. carcass and

  <Desc / Clms Page number 49>

   supports or casings of the rolls and particularly / of the pipe at a determined distance between the frame and the axle
 EMI49.1
 welding to the inlet end the air, poo, sse near the inlet end of the apparatus, the carcass 122 has a descending part 126 protruding which has, preferably a generally narrow section in the form of corner shown in fig.

   14 of the drawing, but at the level of line XIV-XIV only, the inclination of the sides allowing the edges 115 of the pipe, passing in the immediate vicinity of this part, to gradually approach under the influence of the support or wheel casing 94 intended to effect the first closing.



   In the vicinity of its other end, the carcass 122 carries a rolled pole piece 127 projecting downwardly, the construction of which is shown more specifically in FIG. 12 of the drawing, said part preferably joining with the carcass along angular lines 128. as shown in detail in FIG. 13 although joints of other types can be used, the carcass and the pole piece can be kept in suitable contact for their operation by means of angular supports
129 fixed at both ends of the carcass.



   At its lower end, the pole piece 127 has an opening 130 which is slightly chamfered on the inlet side and of a diameter slightly larger than the outside diameter of the pipe being welded in order to allow the latter free passage through said opening. At its lower end, the pole piece 127 can be fixed to the housing or support- 96 to the

  <Desc / Clms Page number 50>

 by means of a suitable crosspiece 131 of non-magnetic material or by any other means.



   A central magnetic core 132 extends continuously between the downwardly directed piece 126 and a pole piece 127; said core has dimensions which allow it to pass freely above the pipe which is welded.



   This core is preferably formed by sheets of silicon steel sheet and has a massive central bar 133 approximately one centimeter thick, as shown in detail in Figs. 15, 16 and 17. On a part of the length of the core 132, there is a winding 134. In this winding can be incorporated a cooling device 135 either in the middle part of said winding, or along its outer edge only or or still along its inner edge, only. it being possible for the device to be of any construction.



   Fig. 18 shows the first-mentioned embodiment. It will also be noted in FIG. 18, of the drawing that each of the turns of the winding 134 is characterized in general by conductors placed in the field and supported by a single cooling device.



   All these windings are preferably connected in parallel so as to give the conductors the necessary cross-section and so as to ensure efficient transmission of heat between said winding and the cooling device. This joint favorable to the transmission of the

  <Desc / Clms Page number 51>

 Heat can be obtained by knocking down the lower ridges 136 at an angle and soldering the conductors there to the cooling device.



   It is optional to provide between the winding 134 and the pipe P a cooling jacket 137 of non-magnetic material. Cooling fluid can be supplied to the cooler 135 and jacket 137 by means of a suitably insulated inlet pipe 133 and outlet pipes connected to electrical conductors 138 and 148 which extend towards it. outside from the inside of the pipe, through the space between the edges 115, to the left of the downward protrusion 126. The current can be brought to the winding 134 through the above conductors. referred to 138 and 148. It is evident that the coil is suitably insulated.



   In the vicinity of the casing or support 96 of the knobs intended to complete the closing of the pipe, a circular pole piece 140 is provided.



   The magnetic seal between said part 140 and its core preferably receives a V-shape as seen in FIG. 17, so as to allow the desired change in the direction of flow, as will be understood by those skilled in the art and as stated above, when it has been indicated that it is desirable to bring the flow into lamellae and to bring it out through one of the edges of said lamellae rather than through their spread surface.



   Around the cooling jacket 137 of the winding 134 of the pole piece 140

  <Desc / Clms Page number 52>

 and the core 132 can be placed a guide 141 which should be given the shape of a non-magnetic metal pipe of a certain length, the section of which has the shape of a C and which has a high resistance, the opening 142 lying between the edges of the pipe preferably lying in line with the space between the edges 115 of the pipe being welded.

   In practice, this space may or may not be filled with a heat-resistant and insulating substance such as 'mica capable of being renewed / or replaced insulated', and by a water pipe, / not shown, but serving to protect the interior assembly against the projection of any particles of heated metal detaching from the pipe during the heating operation. This C-pipe can be divided into sections which can be cooled by means of water, as shown in fig. 24 and that we have, if we wish ,. above the surface carrying the windings.



   It is understood that the guide 141 and the cooling jacket 137 fulfill the purpose x described.: .. with regard to figs. 23 and 24. For the same purpose, it is possible to provide along one of the edges of the guide 141 protrusions 143 constructed in the same way and serving for marl effects as the protrusions 59 described above.



   It is of course further understood that the inner roller 134 may be constructed in sections for the purpose indicated above. In fig. 16 has been shown, in addition to the inner winding 134, an outer winding 144 for adjusting the power supply.

  <Desc / Clms Page number 53>

 tee in turn by means of suitable large section conductors 145. ' This winding can be constructed either in one piece or in several sections. When external adjustment windings are provided, they should be made to rest on suitable supports 146 and it is obvious that said windings are suitably insulated from said supports.



   These windings, shown in a more particular way in Fig. 16, constructed in one piece or in several sections, are preferably so saturated that they can be adjusted axially with respect to the pipes that they are. 'is welded, which makes it possible to regulate in an exact way the tension or the intensity of the heating current which one brings along the different parts of the joint and it should be recalled that, thanks to the conditions fulfilled by the windings, voltage and amperage of the current which is brought along the joints at any point be lowered by moving the primary winding or primary windings away from that particular point and vice versa
 EMI53.1
 Splitting the short arc weld ôI # XS hx3z,

   the potential difference across the joint should generally be a little higher and the current supplied should be a little lower for
 EMI53.2
 the period in which the short arc occurs only during the first contact made by the casing of the rollers effecting the first closure or during the following contact which occurs by the action of the casing with welding sutures in the work in the considered form ; the indicated arrangement xxxx

  <Desc / Clms Page number 54>

 of the winding provides a suitable means of controlling this factor.

   From this point of view, it will be noticed that, although the conditions from the electric and magnetic point of view in which one finds oneself and the characteristics of the seal which one must produce, indicate that the internal unit winding or the The subdivided primary winding are the best, it is perfectly possible to construct a welding apparatus in which the entire winding is arranged outside the pipe which is being welded.



   It is understood, however, that in this case the magnetic repulsion takes place inwardly in the short arc zone or vapor zone and that special precautions must be taken with regard to the construction of the l. look inside. But, when the pipe which is welded has a diameter so small that it does not offer sufficient space for an internal winding and for its core, the external winding may be imposed.

   The Applicant has also observed that, while for pipes of large diameter, the electrical energy used for heating can be brought to 60 cycles, the tubes, as their diameter is smaller, require higher and higher frequencies. and experience has shown that frequencies of 240 to 550 cycles per second give satisfactory results. This is because the smaller diameter pipes do not provide sufficient space inside for the section of the low frequency cores necessary when starting from thick metal and working at high speeds. of the kind discussed above.

  <Desc / Clms Page number 55>

 



     Applicants have also found that in many cases the combination of an outer winding and an inner primary winding having substantially the same number of turns is desirable because the effect of the magnetic losses of one of the windings through. the pipe is more or less canceled by the other. But in this case, the magnetic de-repulsion effect is not completely effective in one direction and a greater effort is required to clean the inside face of the joint, which is difficult to access after welding.



     The pipe, after passing the inner pole piece 140 is at a temperature where it can be welded effectively and at that temperature it enters the passage between the casing reels 96 in which is the final closure, passage where it is subjected to the action of the knurls 97 'and 100' the passage section being such that the heated edges 115 are brought into contact for welding and pressed together to a sufficient extent. considerable. The profile of the lower roll 100 'is preferably such that it removes the bulge 121 and gives the pipe a perfectly circular outer contour.

   It is clear to those skilled in the art that the metal which constitutes the bulge tends, when it is brought to its new position under the influence of the lower roll 100 ', to resume its original shape after that he passed between the knobs. As a result, the edges which have just been welded are in more intimate contact, which precludes the possibility of tearing these edges from one another.

  <Desc / Clms Page number 56>

 



   Instead of producing a profile such as that which has just been indicated and which includes the bulge 121, it is possible to organize the apparatus which is the object of the invention for the work of perfectly circular profiles and, for this purpose , pn provides for a series of retaining rollers capable of cooperating with the welded pipe and of preventing the separation of the edges during their cooling ,.



  In fact, it has been found that similar retaining knobs are not necessary for pipes with a wall thickness of 12.5 mm or less because the hot weld is strong enough to prevent opening of the xxxxx joint which has been subjected to the action of the knobs intended to effect the final closing.



   It is obvious that in working with this embodiment of the present invention one can cause the formation of a short circuit in the casing of the knurls which effects the first closing, which short circuit is followed by the creation of. a short arc as the edges separate instead of the working mode described above, in which preferably the initial contact does not occur until the material has passed between the wheels of the housing 3.

     After the initial creation of the short arc zone that one wishes to produce, this zone is kept in space, in one of the embodiments in exactly the same way as in the other,
As the pipe constitutes a mobile secondary, the importance of constructing the roller housings so as to constitute an open space

  <Desc / Clms Page number 57>

 continuous between the opposite sides of the housing and from the surface of the pipe being welded to a point which is at least above the plane of the carcass 122 serving for the return of the magnetic circuit, becomes evident .

   The water jacket 137 does not constitute a closed continuous circuit and the guide 141 has a space between its neighboring edges whereby conditions are achieved in which large current losses do not occur along other circuits. than that which constitutes the secondary of the pipe itself. For the same purpose the support member 131 of the pole piece 127 and the support or supports 146 of the outer winding or windings 144 are constructed of a non-magnetic material and preferably all organs are suitably isolated from one another from the otter to prevent external losses of the apparatus.



   All the primary windings are shown in the accompanying drawing as being field wound. Although this construction is desirable, this winding method is not essential. Each of the windings is however preferably provided with a cooling device, the inner winding being shown as comprising a cooling pipe 135 with which it is integral while the outer pipe comprises a like cooling pipe 147; water or cooling oil which may be conducted through said pipe 135 in any desired fashion from iso-

  <Desc / Clms Page number 58>

 the 138, 139 and 148 which constitute limits.



  Similar conduits not shown would be used with pipe 147.



   In fig. 8 of the drawing, there is shown, more or less schematically, an embodiment of a combined adjustment device for supplying current to the winding or windings and for supplying water from the winding. cooling to the cooling devices for which this water is intended. -In this figure, water pipes associated with terminals 138 and 148 constitute the twin return paths of the water circulation system having a single inlet pipe 139 which, as we have seen shown, is connected to a supply valve 149. This valve is provided with a rod 150 which projects above it.

   In cooperation with the conductors L and the supplying the current to the winding or to the windings, there is provided a circuit switch 151 provided with a connection member 158 which acts on the rod 150 of the valve. solenoid 153 which operated the circuit switch; inside said solenoid operates a core 154 connected to the circuit switch. The core is normally biased downward by a spring 155 so as to open the circuit switch.



  But, when the solenoid is energized, the circuit switch 151 is moved to the off position so as to supply current to the primary winding or windings and the valve.
149 opens to supply said windings with cooling water. Water fittings

  <Desc / Clms Page number 59>

 directing towards the tap 149 and carrying pipes associated with the conductors 138 and 148, obviously pass through a protective casing, the communication with 139 being able however, in certain cases, to be carried out directly by means of a metallic member if the input is disposed at the electrically neutral point of the winding, or the current can then be divided to return by two paths as mentioned above.



   This construction prevents supplying current to the windings before coolant is also supplied. It is obvious that the tap box which supplies the water from -
 EMI59.1
 /: little cooling mrnulements. -be ld lliç;! 1lt; j that that which supplies cooling water to the cooling jacket or to any other means of cooling provided and that this type of combined adjustment for the current and for the cooling medium is applicable to any type of apparatus constructed in accordance with the present invention.

   Although the apparatus shown in Figs. 8 to 18 has been described as a complete assembly, the construction allows the apparatus to be used in series with a forming machine, by which sheet metal or any sheet material is bent, so that it takes the shape desired to be fed into the welding apparatus. The construction of the roller housing described may include suitable means for the attachment of spacers 156 which may result in such a forming machine. The type of the forming machine is not important, however.

  <Desc / Clms Page number 60>

 essential for the present invention because it is clear that any other suitable device can be used.



   It is possible to use, in order to cooperate with the casing of final closing rollers, a suitable internal mandrel comprising rolls similar to the rolls 44 and 45 described above;
A stopper 157 can also be used. When a stopper is used, it is preferably of high-speed hardened steel or some other special material, the stopper having an outside diameter such as to have the desired inside diameter. pipe as it passes through the passage where it is welded. '
Said stopper can be supported in any desired way, for example by an appropriate extension. from the end of the inner assembly.



   Fig. 19 of the drawing shows a construction slightly modified with respect to the original characteristics of the sheet or strip used to form the article to be welded. As indicated, short arc welding can be initiated by simply bringing the edges of the material to be welded into contact. But if desired the edges can receive small ribs 158 placed along one. - certain angle with respect to said edges. If these small ribs are arranged at equal angles but in opposite direction to the surface of the plate when the plate is spread, they will intersect and give a small contact area when bending the sheet for it. give a tubular shape.

   Small initial metal contact area easily initiates

  <Desc / Clms Page number 61>

 short arc xxxxxxx This measurement is particularly useful when the speed of the welding operation is very high. The thin ribs can be easily crushed and pushed back to ensure the contacts which follow each other at equal distance; the contacts being consumed rapidly under the effect of the short arc xxxxxxx which forms as indicated above.



   Practical tests have shown, however, that no special edge preparation is required and that when a short arc xxxxxxxx begins anywhere along the edges it will propagate rapidly as far as the edge. The space between the two edges and the position of the winding allow this. Said short arc xxx receding along the joint as the pipe advances so that the short arc maintains approximately the same position in space.



   In fig. 26 and 27 there is shown a feed device which is particularly useful in welding devices when it is not desired to bring the edges together or to subject the material to too considerable a deformation force during the phase. of the feed. The feeder shown is of the magnetic type and comprises a large stationary winding 160 to which current is supplied from any source of electricity but preferably from a source of direct current. With this fixed winding cooperates an endless chain 161 carried by chain wheels 162, one of these wheels or

  <Desc / Clms Page number 62>

 , the two wheels being able to be controlled in any desired way, for example by the shaft of a welding machine.

   The chain carries a series of blocks or cores. 163 constructed of a magnetic material and preferably having a U-shape so that they can overlap a part of the winding during the operation of said chain.



   The section of the winding is chosen,. in such a way, with respect to the opening of the nuclei
163 that said winding lies below the outer surface of said cores.



   This outer surface is preferably given a corresponding curve; generally to that of the material to be transported. Due to the fact that the winding is fixed and made of thick copper wire, without moving contact or brushes, there is no difficulty in supplying it with the necessary energy and there are no wires or d 'delicate moving parts which can give rise to disturbances. This makes it possible to construct a robust and extremely efficient magnetic feeder device which gradually comes into contact with the material and which moves outwardly away from said material after the movement of the material has been completed.



   In fig. 28 of the drawing there is shown an embodiment of a device intended for cleaning the joints, this device being more particularly indicated, for pipes of large diameter and when the speed of the welding work is
 EMI62.1
 high 0 zâmûPc that represented in fig. 5.

  <Desc / Clms Page number 63>

 



  Uonformement to this embodiment, the housings 2a and 3a can * hearth away from each other like the housings 2 and 3 of FIG. 1 or they can be slightly more distant from each other. The carcass 28a carries a first pole piece 29a and a second pole piece 31a, these two pole pieces being constructed in the same general way as those shown for example in FIG. 1 of the accompanying drawing.



   The housing 2a carries an upper guide roller 170 and, inside the housing and in the vicinity of the path of the material to be welded, there is a second guide roller 171. Likewise, the housing 3a carries a roller. guide 172 and a lower guide roller 173.



  With these guide rollers cooperates, as shown more or less schematically in Fig. 28, an endless conveyor 174 on which a number of blocks 175 are mounted in series, these blocks being able to be constructed from 'generally like the blocks 75 shown in FIG. 25 and may present the characteristic marls.



   The guide roller 172 shown is driven at a relatively low speed by a chain 176 from a chain wheel 177 which, in turn, is driven by a motor. 178 via a suitable speed reducer 179. This motor is preferably disposed directly on the housing 3a and can be operated to move the blocks 175 either in the direction of movement of the material. M, either in

  <Desc / Clms Page number 64>

 the opposite sense to it.

   In both cases the speed of movement must be such that the blocks are kept at a temperature low enough to prevent them from being burned, the length of the path of these blocks, when they are not in contact with the material, being preferably greater than the length of the path during which they come into contact with the material whereby they have the opportunity to cool themselves effectively in contact with air ., This type of construction is preferable from certain points of view to that shown in FIG. 25 in the sense that the blocks can be more easily cooled, which considerably prolongs their existence.



   It is obvious that the necessary modifications can be made in the construction of the housings to allow the passage of the endless conveyor with its abrasive blocks. It is further evident that cleaning devices of the type shown in FIGS. 25 and 28, are not limited in their application to a particular form of welding apparatus, but that they can be used with any welding apparatus of any shape by means of which the continuous welding is carried out,
In many cases,

   it has been found desirable to construct the inner winding and core assembly so as to facilitate!
30 / of the material
 EMI64.1
 the gu.idage / towards these organs and so as to maintain in a suitable way the -, matter: on these crûmes. Those skilled in the art will understand that

  <Desc / Clms Page number 65>

 the material can be shaped in different ways, some of these ways obviously producing a more precise blank than others. But in all cases, the blank (or material) should be led through the device with the seal in a determined position.

   For this purpose, the construction shown in a more particular way in FIGS. 29-32 which show the core winding assembly with a tubular extension 180 protruding from this assembly on the entry side of the machine.



   This tubular extension ends in a head
181 of a generally conical shape also suitable for forming a plate of suitable shape. At its end, it is possible to weld onto the conical part 181 a threaded sleeve 182 intended to receive a tip 183 over which the material first passes when it enters the apparatus.



   In the embodiment of the present invention shown in the drawing, in which the seal of the material is at the top when it is introduced into the apparatus, it is possible to mount on the conical part. 181 a rib 184 welded to said conical portion in any suitable manner and projecting upwardly so as to extend between neighboring edges of the material.



   The main tubular body 180, the diameter of which is such that it can cooperate effectively with the wider end of the conical part 181 and constituting an extension.

  <Desc / Clms Page number 66>

 management of said conical piece is. preferably provided with a groove 185 in which a guide tape with rollers 186 has been introduced.

   This roller guide tape is constructed, as shown in Fig. 31, and has openings 187 opposed to each other, said openings being able to receive guide rollers 188 clearly visible in Fig. 30 of the drawing, the dimensions of which are such tools, protrude slightly above the edges of the strip 186 in order to come into rolling contact, with the edges of the material which comes to rest on said rollers. By proper selection of the width of the strip 186, the diameter and the position of the rollers 188, the desired space can be maintained between the neighboring edges of the material as it passes over the extensions. guide.

   With the strip 186 a coating tape 189 cooperates, the construction of which is such that it constitutes supports for the upper ends of the axes 190 of the rollers, the lower ends of said axes being screwed into the strip 186. Thanks to this construction, one can achieves a smooth top surface.



   In addition to les.galets 188, the extension 181 has a series of openings at determined points over its entire length and with each of these openings a housing 191 cooperates as shown, in more detail, FIG. 32. In each of these cases turns a roller 192, the periphery of which protrudes slightly above -

  <Desc / Clms Page number 67>

 the outer surface of the extension, as seen in fig. 30. Any desired number of such guide rollers 192 can be provided so that the desired cooperation with the inner surface of the tube-like material is provided.



   It is clear that an extension of this kind constitutes a suitable bending device for the material during its entry into the welding apparatus and for keeping the edges of said material at the desired distance from each other and within. the desired position so that it can undergo an efficient welding operation.



   Although the appended drawing has shown and described in the foregoing the application of the invention to the manufacture of pipes from a single strip of material, it is obvious to those skilled in the art. In the art that in applying the invention to the manufacture of pipes of relatively large diameters, several parallel sheets or strips may be used which each occupy the corresponding part of the total perimeter of the pipe.



  It is not uncommon at the present time in practice to construct large pipes from two or more individual strips or sheets and, by applying obvious but not essential modifications to it, the invention can be adapted to simultaneous welding xxxx or successive of several joints.



   This constitutes, to the knowledge of the applicant, the first effective device for continuous welding with a short arc by the aintien in place of a determined zone where

  <Desc / Clms Page number 68>

 short arc. A zone of this character realizes, as indicated, the rapid heating of a limited part of the metal of the gasket and allows the repulsion of the vapor whereby a clean gasket is obtained of uniform characteristics. . The present apparatus also allows rapid heating whereby a finished product free or substantially free from bending is obtained.



   Further advantages of the present invention result from the fact that the soldering apparatus is of the induction type instead of the contact type and also result from various details of the invention.
 EMI68.1
 / - thanks to the construction described above, / to, 7which the necessary mechanical or electrical options are actually obtained.



   Although throughout the present description we have spoken of induced current heating, it is obvious to those skilled in the art that there is also a part of the heating which is current. Foucault and part also to hysteresis, but it is clear that the heating due to the hysteresis stops after reaching the critical point where the metal becomes non-magnetic. It is evident, moreover, that the magnitude of the heating due to the hysteresis depends on the frequency of the current employed and that the higher the frequencies, the greater the heating due to the hysteresis. Due to the fact that low frequency current is used, a greater part of the heat is generated by the induced current.

  <Desc / Clms Page number 69>

 



   It is also clear to those skilled in the art that, although the material has been shown as being fed into the welding apparatus with the joint facing upwards, said material can also be fed into the apparatus with the seal in any other desired position provided, -; make the necessary modifications for this purpose. In some cases, for example, it has been found desirable to perform the weld, with the joint facing the lower part of the material, because the repulsive effect of the inner winding described above is increased, in this position of the organs, of the action of gravity.

   The fact that the opening is directed downwards also allows free fall between the edges, before the completion of the weld, of any foreign material; such as scabs etc.,. which may have been detached during the shaping operation.



   It has been found in yet other cases that certain satisfactory results are obtained when the joint is placed in a substantially horizontal plane because any substance expelled can fall freely and / loosen from the material outside. the latter without coming together in the vicinity of the seal on the inside, that is to say on the path of the inner rollers.



   In the above, we have discussed the usual tendency of the arc to move erratically from one point to another after its initiation and the advantages of a short arc compared to a work under these conditions. It was further found that

  <Desc / Clms Page number 70>

 the favorable results obtained by using an area where the short arc occurs are often improved or increased when the material is held to have a narrow area / shape.
 EMI70.1
 of short arc xoôéodXKK of YJjjKJè that the Doras apart are over a certain perceptible distance - narrowing parallel,

     said zone gradually cooling to zero at the end of its ends or at both ends / In this way, the tendency of this zone to spread out or to contract due to variations in the width of the joint is complete- ment removed and a determined zone of substantially constant dimensions and heating characteristics is maintained. It is obvious that this mode of working can be easily achieved by means of any of the two embodiments of the present invention.

   In the embodiment shown for example in fig 1, it is possible to adjust the initial passage between the rollers and the passage between the rollers of the auxiliary frame so as to achieve substantially the same internal diameter whereby the material which is The effect of changing from one set of knurls to changing from the other set of knurls does not undergo variations in the spacing of its edges. However, as the material travels from the intermediate support frame to the passage between the final rolls, the edges are brought together.



   In the embodiment shown in fig 8, the passage between the first mittens can be adjusted so that the edges are not actually brought into contact, but so as to bring

  <Desc / Clms Page number 71>

 / se said edges 0 / close until. desired point, the rollers 118 being adjusted so as to maintain this / rollers 97 spacing while the relative position of the / and rollers 97 and 118 is adjusted so as to maintain in position an area of the desired length and position where the short or lightning arc forms.



  Then, the edges of the material, as it passes from rollers 118 to knurls 97 ', can be brought together so as to establish a resistance heating zone. Obtaining a short arc or elair production area. such that the edges are substantially parallel, can obviously be provided by the use of any device chosen from a large number of devices of different shapes.



   The Applicant has further observed that when the housings are moved apart, as has been more or less hematically indicated in FIG. 28, one can produce a kind of short arc xx flash zone of substantially constant dimensions and exhibiting substantially uniform heating characteristics with pipes whose perimeter and contour are originally more or less variable while, at the same time, the wheels 18 of the casing 3a can exert a considerable force for the supply of the material M which they consequently advance at a constant speed. All these points constitute valuable industrial characteristics for any welding apparatus manufacturing large pipes. diameter.



  All the results just mentioned are produced by the deformation of the cold pipe for

  <Desc / Clms Page number 72>

 to give it the shape in the casing 3a which causes a pressure so high that it necessarily results in a traction favorable to the drive on the pipe, allowing said pipe to be driven forward at a sensitive speed. constant despite the usual obstacles which cause varying speed effects in many other manufacturing methods.



   This deformation effected in fact, outside the pole piece 31a, is of a purely mechanical nature and has no effect on the electrical or magnetic circuit of the machine. After the pipe leaves the shaping rolls 18 of the housing 3a, the joint opens slowly until the joint reaches its maximum width and the edges converge again as the tube approaches the rolls. who perform the final closing.

   Due to the fact that this opening of the seal occurs after the deformation or shaping operation in the rigid housing 3a, this opening for the seal will be practically constant for steel sheets of thickness and thickness. constant hardness, regardless of moderate variations in the width of the original plate from which the tire was formed.



   If the maximum width of the gap is kept significantly less than the distance where the short arc occurs with the applied potential and if the primary winding is of sufficient length to be placed under practically all the housing of the closing edges , the entire heating zone is clearly defined and the heat

  <Desc / Clms Page number 73>

 developed becomes substantially constant regardless of the normal variations in the perimeter of the pipe when it is given its first shape. The area where the short arc occurs in the case of the V-joint is not defined in this way, as there are no precise limits for the propagation of the flame along the joint.



   If the heating zone of the joint (of the form mentioned above) is rather narrow and long, we
 EMI73.1
 l-of the tension- finds that the proportion of the metal artie in the pipe over its entire circumference increases and that the proportion / of the tens- tiox '.-' the joint decreases in a correspondingly distributed manner in considerable limits, which tends. to better stabilize the short arc and to give more consistency to the current helps to maintain the desired constant heating; on the other hand, the perfect evenness of movement mentioned above also helps to keep constant the total quantity of heat released per unit length of the joint.



   During the present description, it has been a question of adjustments, pressures, frequencies, currents, currents, speeds, displacements, etc.



  Due to the current knowledge of this branch of industry relating to welding, it is considered that the indications of the present description are sufficient to enable a person skilled in the art to implement the invention. However, in order to facilitate the practice of the invention and to entirely eliminate any need for lengthy experiments, there will be indicated in what follows, by way of example only and not in a limiting manner a series of conditions under which an apparatus as described has worked successfully.

   In the work in question the material of a substantially tubular shape was produced by shaping plates the width of which was 1.59m and the thickness of about 9.5m, the

  <Desc / Clms Page number 74>

 length of the plate varying according to commercial standards,
This material which had been shaped by a cold operation could have been formed in any other desired way.

   In this form, it constituted a substantially tubular body whose edges were spaced from each other by about 38mn and whose outer diameter, including the seal was about 528mm, the inner diameter being about 509mm, With the embodiment of the invention shown in fig. 1, the passage between the first rollers was adjusted for an internal diameter of approximately 516mm, which considerably brought the edges of said tubular body closer together and reduced their spacing. at approximately 0.85mm. When we wanted to achieve a ssnsible parallelism between the edges, we adjusted. the rollers 26 for the same internal diameter as that which corresponds to the knurling wheel 18 of the catter 3.



   Under these conditions, the wheels 18 of the housing 2 were adjusted so as to achieve an internal diameter of approximately 513mm, this being sufficient to bring the edges into contact so that they can be welded together, to expel; the heated part of these edges to a temperature where metal can flow and to contact the parts which had been heated to approximately the temperature of fine grain formation, whereby a weld was obtained! exhibiting the characteristics described above.



     By working under these conditions with a single primary internal winding, said winding was provided from 3,400 to 3,800 K.V.A. the primary voltage being approximately 850 V., the intensity varying between 4,000 and 4,500 amperes and the frequency being 60 cycles.



   The material was advanced through the welding apparatus at a speed varying between

  <Desc / Clms Page number 75>

 13.75 m. and 2.30 m. per minute, the highest speeds being below the limits that can be achieved when using an organization giving a number of K.V.A. higher.



   Under these conditions, a product was obtained whose welded joint possessed greater strength and whose grain was better than those of other parts of the product, the maximum heating having taken place in the vicinity of the edges of the joint and having been. almost entirely limited to these edges. In the finished product the joint appeared as an almost perfectly straight line from end to end; said joint was continuous from end to end. The pipe passed rigorous hydrostatic pressure testing and exhibited no end-to-end bends.



   Although in the foregoing a concrete example has been given, it is understood that the conditions are likely to vary according to the characteristics of the material to be formed, the surface of the section, the speed at which it is desired to carry out the welding. and the energy available.



   Although in the foregoing certain preferred details of embodiment of the present invention have been shown and described, it is obvious to those skilled in the art that the object of the present invention is not limited to the details of the invention. particular construction shown and that modifications in construction as well as in procedure may be made without departing from the spirit of the present invention.


    

Claims (1)

R E V E N D I C A T IONS 1. A welding process comprising the use of the material to be welded. as a mobile secondary and the generation of successive heating currents in said material. during its movement, the method being characterized by the fact that said heating currents are produced by several primary sources organized so as to generate an induced current / in succession in the material and arranged / in the axis of this material. 2. Method according to claim 1, for the welding of a moving material substantially tubular in shape, .characterized by the fact that the metal is .deformed so that it takes a substantially regular contour and that periodically varying induced currents are generated in the material - which moves, in order to perform the welding operation. 3.- Method according to claim 1, or in claim 2, for the continuous welding of a mobile material of substantially tubular shape characterized by a short arc heating operation xxxxxx carried out.- in said mobile material by the induced currents generated in this material from the sources primary. 4. Method according to any one of claims 1 to 3, characterized in that the material is guided so as to produce a short arc heating zone xxxxxxxx and a resistance heating zone, a certain pressure. being applied to the material to complete <Desc / Clms Page number 77> the welding. 5, - Process according to any one of claims 1 to 4, characterized in that an open seal is produced in which the heating is carried out and that the distance between the edges of the seal is maintained at a limit value maximum, substantially constant, to then close the gap to form a heating surface, by a short arc or flash, elongated, very narrow and substantially defined. 6. - Method according to any one of claims 1 to 5 characterized in that settxxxx with respect to xxxxxx the intensity / heating of the current, the duration of the weld and the degree of the pressure applied. to the material so as to expel all the metal from the seal xxxx whose temperature is substantially above the critical point. 7.- A method according to any one of claims 1 to 6, characterized in that the metal of the joint, after being welded is quickly cooled to approximately the critical temperature to minimize the time during which the grain may grow larger and therefore produce finer grain. 8. Welding apparatus for carrying out the processes of any one of claims 1 to 7 and comprising devices moving the material to be welded and which may have a substantially tubular shape, the apparatus being characterized by a winding with multiple elements connected in parallel, placed in the immediate vicinity of the material and acting on the latter by induction. - <Desc / Clms Page number 78> 9.- Apparatus according to claim 8, characterized by the fact that the multi-element winding is placed inside the material. 10, - Apparatus according to claim 8 or in claim 9, characterized in that the multiple element winding is arranged to be supported in a position such that the tubular material which is welded moves relative to said winding so that the latter acts on it by induction. II.- Apparatus according to any one of claims 8 to 10, characterized by a protective screen for the winding. 12.- Apparatus according to any one of claims 8 to 11, characterized by guiding members of the tubular material arranged so as to keep the edges of the pipe over a certain length thereof out of contact ef- effective with each other and produce a short arc heating zone xxxxxxxx in this part of the pipe. 13.- Apparatus according to claim 12 characterized in that some of the guide members are effective in bringing the edges of the pipe into contact so as to produce a resistance heating zone. 14.- Apparatus, according to claim 12 or claim 13, characterized in that a primary winding has been arranged so that it cooperates with a part of the material, part 'in which the edges are kept out. contact and that a second rnroule- <Desc / Clms Page number 79> ment in parallel with the first and organized so as to cooperate mainly with a part of the material, part in which the edges are in contact. 15. - Apparatus according to any one of claims 8 to 14, characterized by a casing or a greater number of casings each comprising several wheels, organized so that they come into engagement with the material in the form of pipe to be welded, the knobs of one of the casings or of a greater number of eccentric casings cooperating with sleeves / meshing with each other to effect the adjustment of said knurls in moving them inward or outward with respect to a substantially common axis. 16.- Apparatus according to any one of claims 8 to 15, characterized in that a wheel or several wheels are organized to engage with the material in the form of a pipe and that each of them carries a removable bandage or in several parts. 17.- Welded product obtained by applying the methods according to any one of claims 1 to 7 and characterized by a joint consisting essentially of fine-grained metal. 18.- Welded tubular product obtained by applying the processes according to any one of claims 1 to 7 and characterized by a welded zone from which the material initially rejected has been removed before the final welding operation. <Desc / Clms Page number 80> 19.- Welded product, obtained by the application of the processes according to any one of claims 1 to 7 and characterized by a joint of which the parts of metal heated above the critical temperature have been substantially all. extruded and in which the fine-grained transition zones are substantially in contact. BRIEF SUMMARY Electrical de.soudure method for the manufacture of tubes characterized by creating an induced current in the sheet by serving as a secondary this sheet moving above a primary winding arranged inside the tube, in formation; the flow passes from the primary to the secondary, heating the seal, expelling the impurities and oxides they contain from the molten materials. The welding apparatus comprises, in addition to the windings used to establish the electrical circuit, knurls which bring the edges of the tube into contact and then spread them very slightly apart to produce over a certain extent a very short arc which performs the welding.