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PROCESS AND DEVICE FOR PRODUCING THIN WALLED OR EXTRA-THIN WALLED SMOOTH TUBES BY WELDING
CROSS REFERENCE TO RELATED APPLICATION
Applicant's prior application, Ser. No. 878,279, filed Nov. 20, 1969, now U.S. Pat. No. 3,610,863, issued on Oct. 5, 1971, entitled "APPARATUS FOR THE PRODUCTION OF THIN METAL TUBES" discloses a similar process and apparatus except that in said prior application, the welding electrode is moved longitudinally along the tube blank. Such tubes are disclosed to be high quality tubes suitable in particular for processing into corrugated pipes, for example, by hydroforming.
This invention relates to improvements thereto, providing on the one hand, for a substantial simplification of the device, and on the other hand, for a substantial increase in production.
Essentially, the process, according to the invention is characterized in that, while using practically the same tube blank conformation and welding means as in the previously mentioned application, the production is carried out as a continuous operation, whereas, according to said application, operations were carried out in successive steps. The technical progress achieved is very significant. Indeed, all idle times involving the return of the welding torch to the starting position, and the tightening and loosening of the jaws seizing the tube blank, in disconnecting the arc, and in the opening and closing controls for protective gas pipes, which are to be effected at each advance step, are thus eliminated. The torch remains stationary and the tube blank goes by in front of it, at a constant speed, until the strip of sheet metal, which provides this tube blank, is used up. As the ends of rolls of sheet metal for the tube blank can be joined together, the length of the tube produced can be practically unlimited.
The characteristics of the invention will best appear from the description which will now be given of an embodiment shown simply by way of illustration in the appended drawings, in which:
FIG. 1 is an overall elevation and partial vertical longitudinal cross-sectional view of the machine;
FIG. 2 is a cross-sectional view to a larger scale, approximately along plane II—II of FIG. 1;
FIG. 3 is another section, approximately along plane HI—III of that same figure;
FIG. 4 shows the main components of this machine, partly in perspective and partly as a vertical longitudinal section;
FIG. 5 is a partial view showing a vertical longitudinal section of an alternative embodiment of the invention;
FIG- 6 is a partial vertical longitudinal sectional view to a larger scale;
FIG. 7 is a sectional view, approximately along plane VII-VII of FIGS. 1 and 6, and
FIG. 8 is a view similar to that of FIG. 4, showing a varying embodiment.
The machine, according to the invention, comprises the following main components, listed in the order in which they go into operation.
a series of vertical forming roller pairs in an appropriate number, designated as A in FIG. 1, processing in a known manner a strip of sheet metal 1 provided by a feeding coil, not shown, first as a gutter
2 and then as a tube blank 3 open along its upper generatrix.
a pair of horizontal rollers designated as B, completing the conformation of the tube blank;
a die-conformator unit, designated as C;
a welding unit, designated as D, and which comprises essentially, according to the invention, and in addition to the known welding torch 4, two external half-shells and an internal support-distributor;
finally, a pair E of horizontal rollers designed to guide the welded tube which, as it exits from the machine, is seized and propelled continuously by a pair of caterpillars of known construction, not shown.
The pairs of forming rollers, considered individually, are not substantially different from those already described in the previously mentioned application, but, according to the invention, each pair is arranged at a level which is slightly higher than that of the preceding pair, in the direction of feed of the strip of sheet metal, so that the edges of the blank are subjected to a tensile stress. Applicant has indeed noted that, when forming the tube blank, its lower part travels, during its movement up to the die, over a shorter distance than its edges, thus leading to the formation of folds. This drawback is eliminated very simply by the arrangement adopted. The optimum slope to be given to the tube blank is determined by the relative location of the successive pairs of rollers which, to this effect, are vertically adjustable in their supporting cages, which are in turn horizontally adjustable with respect to one another.
The horizontal rollers B do not, by themselves, have any original characteristic. However, it should be mentioned that each of them is adjustable in the horizontal plane with great accuracy, through use of an appropriate micrometer screw device. It is indeed important that the two lips of the tube blank maintain between them the free passage of the end part of the supportdistributor which will be described later, without being damaged in any way by the same.
The tube blank thus prepared then moves into the die conformator unit designated as a whole as C, which acts in a manner already described in the previous application, so as form thereon, on each edge, a joining lip 5 (see FIG. 7). However, and according to the invention, the conformation of the tube blank before welding can be provided for according to two different methods, to which correspond respectively FIGS. 2, 4 and 5, 8.
According to the first of these, die 10 is constructed in two parts, separated along a horizontal plane including the diameter. In a known manner, forming plates II made of treated metal reinforce the edges of the upper slit of the die, which is itself made of a material having a very low friction coefficient, and whose section continuously decreases between the inlet end and the outlet end of the latter, to act progressively on the tube blank and apply its edges on the conforming or lip forming boot 12 known from the previous application. The latter is hinged to a support 13, adjustable particularly in the vertical direction with great precision, by means of a micrometer screw.
In this first embodiment shown in FIGS. 2,4, the two parts of the die have their end faces in coincidence, as shown in FIG. 4, and the conforming boot 12 is housed and supported in the upper part of said die. It must in
deed be perfectly maintained and guided, considering are made. They must also be made of a material which
the high stresses to which it is subjected upon forma- will eliminate any instability of the electric arc by mag
tion of the lips 5. netic blow out.
In the second embodiment of the machine, shown in According to the invention, an elastic or resilient asFIGS. 5 and 8, lips 5, instead of being completely ob- 5 sembly of half-shells can also be provided, so that they tained through cooperation of the die and the conform- can absorb expansions due to heating, while maintaining boot 12, as mentioned above, are preformed by the ing an accurate pressure contact on the lips of the rollers of unit A. Thus the conforming boot 12 now blank. To this effect, and as shown in FIG. 3, the halfprovides only for the completion of the lips, and it can shells are maintained close to each other by comprestherefore be positioned downstream of die 10, at a lo- 10 sion springs 31 surrounding axles 23a, 23ft and bearing, cation where it will be completely unconstrained. on the one hand, against supports 22 and, on the other
A disk 15 is fixed, at the outlet end of die 10, to a hand, against said half-shells,
mounting 16 which is itself assembled to support 17 of As already mentioned above, the tube blank is accu
the die, this disk forming, in order to correctly guide rateiy guided, at the time of welding, by means of half
and maintain the tube blank 3 upon its entrance into 15 shells 20a 20b and support-distributor 20, whose roles
welding unit D, a central circular opening whose diam- is very important, and which will now be described in
eter is practically equal to the external diameter of the greater detail, referring more particularly to FIG. 6. It
tube blank, with a notch providing for the passage of is essentiany intended to protect the inner side of the
the lips 5. It acts furthermore, as a shielding screen to weld agajnst oxydation by adequately localizing the
prevent overheating of die 10 by the welding arc. 20 protective gas> to prevent the coiiapse of the meited
In the second embodiment, the die consists of two meta, bath SQ as to ensure a smooth appearance of the
parts, 13a, 13b separated along a median horizontal weld> and alsQ tQ contribute t0 tnerma, dissipation.
plane (see FIGS. 5 and 8), its upper part 13a being According to the invention, said support-distributor
shifted towards the upstream side of said die together rises a tubular bod 21 flxes to the downstream
with the conforming boot 12 associated with it thus 25 ^ Qf & ^ ^ ^ ^ ^ ^ ^
moving them away from the electric arc of torch 4 whkh carri in ^ ^ of itg tream end an end
The tube blank thus conformed then passes into the jece 33 (seg HQ 4 Qf directJveIticM dSi
welding unit itself, designated as D in FIG. 1. As shown . . . , . - . , ,, , ,
■ m • • • •• c L i_ i. passing between both edges of the tube blank 3. The
in FIG. 7, it consists essentially of two half-shells 20a, , D ,. , . , ° ... , . ...,
„„, ,' ,. . • . in length of tube 32 is chosen so that end piece 33 will be
20b and of a support-distributor 21, between which the JU . °. , . .. , . r ... ,
x , , . , vv. ■ . ■ '. ,. located in a zone in which these edges will be suffi
tube blank moves in a continuous motion, according to .. . . , ■" ..
. ... „ , .. «„ ... ,.. ciently far apart from each other so as not to risk any
the invention. Half shells 20a, 20ft are mounted in slid- . J „ r iW , „ T, ■ . . ■ ,. , .
* ii Hi. u- u *u u .u • . damage from the latter. This end piece is hinged to a
ing supports 22a, 22o, which, through their transverse . , °. 1JL
displacement controlled by any suitable means, not fork 34, ^PPorted by a supporting rod 35 whose opposhown, provide for the accurate adjustment of these 35 «te end is attached to the frame of the machine in any two half-shells with respect to the support-distributor. appropriate manner. It is thus possible, by moving fork According to another characteristic of the invention, 34 on 5°d 35't0 adjust the longitudinal posihalf-shells 20a, 20ft freely oscillate around horizontal l'on of the support-distributor 21 with respect to torch pivotal axis 23a, 23fc, thus providing for their self- 4- Moreover, the end piece 33 can freely oscillate orientation with respect to the tube blank 3, and thus 40 around ,ts axls of attachment to fork 34, so as to profacilitating its passage. Said sheels 20a, 20ft are pro- vlde for the self-alignment of support-distributor 21 invided with bores or channels 24 in appropriate number slde the tube blank.
and arrangement, for the circulation of a gaseous or liq- Just 1,ke half-shells 20a, 20ft, support-distributor 21
uid refrigerating fluid, so as to remove a substantial is bored with channels, not shown, designed for circula
part of the heat given off during the welding operation. 45 tion of a refrigerating fluid which arrives therein
For the same purpose, supports 22a, 22ft are provided through an inlet tubing 26 and is evacuated through an
with cooling fins or blades 25, which also provide for outIet tubing 27» as shown in FIG. 4.
thermal dissipation. Inlet and outlet tubings for the re- According to the invention, retaining tube 32 is also
frigerating fluid, hot shown, are connected to the corre- used to feed support-distributor 21 with protective gas.
sponding half-shells channels, designated by 24a, 24ft 50 To this end, it is connected through its upstream end to
in FIG. 4. an inlet tubing 36 which, just like lines 26 and 27, pass
Furthermore, a small horizontal plate 28 of treated through the upper slit of the tube blank 3.
steel comprising a groove 29 on its lower face (see FIG. Radial channels such as 38 (FIG. 6) communicate
7), in which the two lips 5 of the tube blank 3 are en- with the blind central bore 37 of support-distributor 21,
gaged, is provided upstream of the welding torch 4, but said radial channels conducting the protective gas in a
in the direct vicinity of the latter; said plate being median longitudinal upper groove 39 corresponding to
pressed against the upper face of half-shells 20a, 20ft, the weld seam.
by means of jaws 30 which are tightened by screws as It is very important practically to provide for a consshown in FIGS. 6 and 7. The plate 28 can also be pro- 6Q tant flow and good distribution of the protective gas, vided in two parts which are contacting in the vertical and this condition is satisfied, according to the invenwelding plane. tion, by suitably choosing not only the number and loExperience has shown that the surface condition of cation of channels 38, but also the profile of groove 39, the half-shells 20a, 20ft between which the tube blank which is of a general trapezoidal section, and whose passes, plays an important role in practice. They must 65 depth and width vary along its length, as a function, in be ground and polished with great care, so as to avoid particular, of the characteristics of the metal of which gripping of the tube blank and contamination of the the tube blank 3 is made, and of the welding process weld by particles of the metal of which these half-shells adopted (for example TIG or Micro-plasma).
Just as half-shells 20a, 20b, the support-distributor 21 must also have an appropriate surface condition. For example, it will be chromed or polished, so as to avoid gripping and especially entrainment of particles of metal which would risk contaminating the weld.
Further, and according to the invention, said support-distributor has additional features, each of which contributes to the high quality of the weld obtained.
First of all, it comprises two diametrically opposed lateral flat surfaces 40, 40', (see FIG. 7) which reduce the friction of the tube blank, upon its passage against the same. Its external diameter D. over a certain length L (see FIG. 6), is very slightly greater than the internal diameter of the tube blank to be welded. Over another length LI, its external diameter d becomes smaller than the internal diameter of the tube blank. Over a third length L2, its external diameter dl is still further reduced to a greater extent. Finally, over the last length L3, its external diameter d2 becomes equal again to diameter D. Channels 38 open into zones L and Li, and the zone LI being that in which the welding is carried out. The size of channel 38a opening into this zone, straight beneath the welding torch 4, is greater than that of the other channels 38. The outlet opening of this channel 38a is at a minimal distance L4 from the rear edge of small plate 28, so as to avoid the initiation of an arc on the latter; however, the welding point is sufficiently close to this small plate to prevent any deformation of the metal through a thermal effect over this length L4, and thus provides for a good interfusion of the two lips 5.
As far as zone L2 is concerned, it forms an annular peripheral chamber in which the protective gas is retained, so as to provide both a deoxidizing and cooling action. Zone L3 partially closes the previously mentioned chamber, while providing for the measured evacuation of part of the hot protective gas. The channels for the circulation of the refrigerating fluid in the support-distributor 21 have not been shown; they can have any appropriate configuration and distribution.
As a simple illustrative example, in a machine constructed according to the invention, and having given complete satisfaction, the specifications of the supportdistributor mentioned above were as follows, for the production of a tube with an internal diameter, d>, of 15 mm.
L = 27 mm D = * + 2/10 mm
LI = 23 mm d =4> - 5/10 mm
L2 = 21mm dl =<£ -10/10 mm
L3 = 9 mm d2 ->-5/10mm
Small plate 28 comprises, at the upstream end of its median groove 29, a rounded edge not shown, facilitating the entry into said groove of lips 5 of the tube blank. The upper ends of these lips are thus maintained substantially in the same horizontal plane by said plate, in order to ensure the equal fusion of these two lips, which is indispensable for obtaining a good quality weld.
Finally, and as shown in FIG. 6, a screen 42 is arranged downstream of torch 4, so as to protect the welding electric arc from air currents, thus improving its stability.
It will be noted that the weld unit D of FIG 1 comprises components with simple shapes, easy to assemble and which are interchangeable.
The operation of the device described and shown is as follows: the starting strip of sheet metal 1, passes
through the forming roller unit A, progressively taking up a more and more pronounced shaped in the form of a gutter, there being no danger of any folding or wrinkling, due to the staggered position of the roller pairs.
5 The horizontal rollers of the unit B then bring the edges of the strip of sheet metal already shaped in the form of a gutter closer together and prepare its entry into the conforming die unit C. In the latter unit, the conforming boot 12, in cooperation with the plates 11, acts to
10 form the lips 5 on the edges of the strip of sheet metal preparatory to feeding to the welding bath, or it only completes said lips, if the latter have already been preformed on the edges of the strip by means, in particular, of appropriately shaped roller pairs.
15 The two half-shells 20a, 20b in weld unit D, in cooperation with support-distributor 21, then provide a precise approach of the lips toward each other, and the perfect alignment of said Hps of the blank with respect to the electrode of torch 4. The support-distributor 21
20 also contributes to the guiding of the tube blank into the weld zone and, because of its very special shape, it provides, in addition, for an optimum distribution of the protective gas beneath the weld. It also participates in providing efficient cooling of the welded tube, as do
25 also the half-shells 20a, 20b.
The combination of all these means makes it possible to obtain a weld whose quality is in no way inferior to that obtained by the means described in the previously mentioned prior application.
30 The significance of the improvements obtained will appear clearly from the two following numerical comparisons:
the cost of the welding unit constructed according to
this invention is only one tenth of that of the recip35 rocating welding unit provided according to the
previous application; the production, with an identical starting strip of
sheet metal, has been increased from 1.30 to 3m
*® It should be specified, finally, that the areas of application of the two machines under consideration are not identical. The device covered by the previous application, operating step by step, is more appropriate for the production of tubes with a diameter equal to or greater
45 than 25 mm, because of the very elaborate guiding and holding members which it comprises. The one described and shown in the present application, which is simpler and more rapid, is particularly suitable for the production of tubes with a relatively small diameter.
Obviously numerous modifications of a constructive nature can be introduced, without departing from the scope of the invention, into the various components of the machine here described and shown by simple way
55 of illustration. I claim:
1. In a device for continuously producing smooth tubes having thin to extra-thin walls from a continuous strip of sheet metal of the type having a horizontally ar
g0 ranged series of roller pairs for forming the continuous strip first into a gutter and then into the outline of a tube with a circular section open at its upper part, additional means for forming an exterior oriented lip on each of edges at the upper part of said tube blank and
65 means for aligning and welding said lips, the improvement comprising adjustable mounting means for a plurality of said pairs of forming rollers whereby the tube blank as it travels toward said welding means is made