Process of spirally winding tapes

A method and a device for the spiral winding of tapes for the continuous production of tubes without a core and having an angular cross-sectional area. A tape is guided centripetally during each bending process along a convexly curved conducting surface situated in the region of the tube being formed, the intake side of which conducting surface is located at the feed level. The centripetal guiding of the tape is suspended when the conducting surface reaches the outlet side for forming the excluding level segment of the tape.

FIELD OF THE INVENTION 
The present invention relates to a process for the spiral winding of tapes, 
especially of metal tapes longitudinally grooved at the edge, on tubes 
having essentially angular cross-sectional areas, whereby the tape being 
continually advanced is bent off obliquely to the feed direction around 
each respective interior angle of the cross-sectional area in accordance 
with a predetermined length of feed, as well as a device with which to 
carry this out. 
PRIOR ART AND ITS DISADVANTAGES 
Known in the art are tubes with an angular cross-section, such as are used 
principally in ventilation channels, and especially those having a 
rectangular cross-section, which are preferred over round tubes for 
aesethetic reasons and where space conditions are restricted, although 
these are considerably more expensive and costly to manufacture. 
Thus, for example, in German Pat. No. DE-A-22 28 935 a process is described 
according to which a metal tape equipped with grooved edges is fed 
diagonally in cadence into a bending station, is fixed in position by 
means of a hold-down on the guide table and is edged over the table edge 
by means of a bending tool situated above the guide table. Following the 
reverse motion of the bending tool into the starting position the metal 
tape is advanced by the next length of feed and is then fixed in place and 
edged off. 
A winding process for edged tubes in which the tape is wound around a core 
are known in the art from American U.S. Pat. Nos. 2,276,285, 2,440,792 and 
2,640,451. The use of a core is disadvantageous since a separate core is 
required for each cross-sectional area and it is necessary to adjust the 
bending and connecting devices impinging on it. 
Tubes with a round cross-section may be wound from relatively narrow tapes 
of great length drawn off spools around an intended core in spiral form in 
a continuous operation, so that the tubes will show a given diameter 
(AT-B-248 839 and 316 283). 
According to AT-B-316 283, the winding of folded-seam tubes is accomplished 
by means of roller pairs which simultaneously close the folded seam. 
According to AT-B-248 839, the tape is freely bent by means of a number of 
traverses or strokes of a tool in the close vicinity of an abutment. 
Non-round tubes can also be produced if periodic alterations are made in 
the criteria determining the curvature. This process is only applicable to 
welded-seam tubes since the striking process is not possible for edged 
grooved borders. 
OBJECT OF THE INVENTION 
The present invention has the object of finding a process and a device for 
the continual production without a core of tubes with an angular 
cross-sectional area, whereby grooved edges can also be provided for the 
use of metal tape. By an essentially angular cross-sectional area a 
cross-sectional area is meant bordered by straight lines that fit into one 
another by means of curves, so that the tubes manifest edge areas that are 
rounded. 
In accordance with the present invention this object is accomplished by 
guiding the tape centripetally during each bending process along a 
convexly curved conducting surface situated in the region of the edge of 
the tube being formed, the intake side of which conducting surface is 
located at the feed level, whereby the centripetal guiding of the tape is 
in turn suspended when the conducting surface reaches the outlet side for 
forming the excluding level segment of the tape. 
The process in accordance with the present invention thus represents a 
continual winding process not dependent on the formation of the seam. 
Angular tubes with rounded-off edges of any desired length may be produced 
without interrupting the tape feed and while retaining the guide, even 
during the bending process, whereby tubes with any convex cross-sectional 
area and any given number of angles may be manufactured by virtue of the 
choice of the length of curve and of the length of the flat segments. 
A preferred embodiment for carrying out the process in accordance with the 
present invention has a guide table for the incoming tape, a supporting 
element in the region of the edge of the tube being formed, a bending tool 
which can be moved around an axis parallel to the contact surface of the 
guide table, and a mechanism with spools for the continuing connection 
between the incoming tape with the advancing winding of the tube and is 
characterized by the fact that the supporting element is formed by a bar 
extending above the guide at an interval corresponding to the thickness of 
the tape over at least two windings of the tube, which bar is equipped at 
the least in its lower half facing the guide table with a convexly curved 
contact surface, and that the bending tool is formed by a level bending 
plate inserted into the guide table, the upper side of which bending plate 
guiding the tape during the bending process rolls from the contact level 
crossing upward on the conducting surface, drops downward at the end of 
the bending process around a fixed axis on the table away from the 
conducting surface and into the contact surface and finally moves back 
into the starting position. 
The tape feeding into the aperture between the bar and the contact level of 
the guide table is advanced on the guide table, with account taken of the 
angle between the direction of intake and the longitudinal direction of 
the bar, by the extent of the desired length of side of the 
cross-sectional area and the tube being produced, less double the portion 
of the curves, following which the bending plate turns up from the contact 
level. In so doing, the continually advancing metal tape is guided 
centripetally on the conducting surface of the bar and bent to match. As 
soon as the the curve length corresponding to the desired interior angle 
between the two lateral surfaces of the emerging tube is reached, an axial 
interlocking is accomplished between the bending plate, which turns around 
the axis of the conducting surface during the bending process, and the 
guide table. The bending plate is closed down into the guide table around 
the resulting axis fixed on the table. This axis fixed on the table arises 
opposite the incoming tape in relation to the aperture between the bar and 
the guide table, so that the upper side of the bending plate pulls up in 
the shutting motion from the tape being guided on the conducting surface 
and does not impede the continued further advancing of the tape, whereby 
the side wall part, which has just been bent upward, of the emerging tube 
is shunted along. During the advancing of the next segment corrsponding to 
a second side of the cross-sectional area the bending plate reverts to its 
starting position after the axial interlocking has been disengaged. Thus 
the next bending procedure can be introduced. The upper side of the level 
bending plate, which, in order to guide centripetally, always turns 
parallel to a tangential level of the conducting surface during the 
bending process, in a further embodiment is capable of being moved in a 
guide of the guide table parallel to the conducting surface which is also 
convexly curved. A preferred embodiment makes provision for the bending 
plate to have at least one trunnion which engages in a guide aperture 
running parallel to the conducting surface of the bar and which can be 
stopped in in the final bending position when the axis fixed on the table 
is formed, whereby at least one controlled activating lever is hinged on 
the bending plate. A sequence-switch cam has been provided for the motion 
of the activating lever especially, the drive of which is coordinated with 
the advance of the tape. 
An additional preferred embodiment provides for the roll-off speed of the 
upper side of the bending plate in the shifting motion to be the same as 
the advancing speed of the tape, so that practically no relative motion 
occurs between the tape and the bending plate and that as fast a tilting 
motion of the bending plate as possible will occur at the end of the 
bending procedure. This can be accomplished by an appropriate designing of 
the sequence-switch cam, by coupling and uncoupling the control drive, and 
if necessary by means of a step-up in the transmission via an additional 
activating lever. 
To bring about the axis fired on the table by means of an axial 
interlocking of the trunnion a spring-loaded stop lever will preferably be 
used which comes to rest on the trunnion when the bending procedure is 
concluded, whereby a disengaging extension is provided for on the stop 
lever to act on the bending plate dropping down at the end of the 
retro-closing movement. As soon as the upper side of the bending plate is 
aligned with the contact surface of the guide table, the trunnion is thus 
set loose and the axial interlocking disengaged, whereupon the bending 
plate will return to the starting position, preferably by means of a 
restoring spring. Thus in a preferred embodiment a guide stretch in a 
straight line is formed for leading back into the starting position and 
this connects the ends of the convex guide. The switching operation is 
thus accomplished for leading back in a straight line by means of a 
depressed stop lever, which when connecting to its detent shows a segment 
aligned with the restoring movement in a straight line and bridging the 
convex guide movement. 
The mechanism equipped with a locking or welded roller pair for connecting 
the longitudinal tape edges by winding the tube can in itself be located 
in any place desired. It will be advantageous to install it at the 
narrowest point of the aperture between the bar facing the conducting 
surface and the guide table or the bending plate impinging into this 
region since no change of location for the roller pair is necessary there. 
For this purpose it is provided in one embodiment for the bar to be 
cylindrical and hollow and for the inner connecting roll to be parallel to 
the feeding device in relation to the tube to be formed. Since in general 
it is necessary for it to have a drive, it is mounted on a shaft which 
extends diagonally into the hollow cylindrical bar. In the area closest to 
the guide table, thus at the narrowest site of the aperture a pass-through 
slot is provided for the inner connecting roller, through which it makes 
contact with the tape edges to be connected. The outer counter-roller is 
mounted in the guide table. 
During the blending process the tube under formation is moved upward by the 
bending plate. For tubes of a fairly large cross-sectional area it will be 
advantageous to make provision for an opposing support from the point of 
exceeding the unstable point of equilibrium, on which support the tube can 
rest until the bending process is completed. Thus in a further embodiment 
a support place is situated just opposite the bending plate, which support 
plate is also guided centripetally in the conducting surface. At the 
beginning of the bending process the support plate located in the guide 
table and which is displaced opposite the bending plate in the 
longitudinal direction of the tube by at least the width of the incoming 
tape is also moved upward and directly returns to its starting position 
again when the tube being formed is taken over. Since the sequence of 
movements is similar to that of the bending plate, the control of it can 
also be accomplished in a similar manner, for which purpose at least one 
activating lever and a sequence-switch cam have in turn been provided by 
preference. If cam disks are provided for as sequence-switch cams, these 
should preferably be installed each to an intermediate lever hinged to the 
activating lever. Provision is made through a further possibility for one 
arm extending radially from the drive shaft each to be provided for as cam 
sterring, on the free end of which a tang has been provided, and for a 
stop groove to be provided on the free end of each activating lever in 
which the tang reaches via an angular area of its backward motion. 
Preferably both sequence-switch cams will be arranged on the same drive 
shaft, the rotation of which, as mentionedl, is coordinated with the 
advance of the tape. 
For the production of long pieces of tube it is recommended to have an 
additional support device for the tube, each to consist of a plate pair 
that can be moved to be synchronous with the bending plate and the 
supporting plate, and is arranged in a fixed position to them.

The process illustrated in the sequence of motions in FIGS. 1-8 can be 
accomplished, for example, with a device in accordance with FIGS. 9 
through 11. On a stand for the device a guide table 9 and a number of 
vertically situated plate-shaped supports 27 have been provided. Above the 
table level A a support element in the form of a hollow cylindrical bar 2 
extends while retaining an aperture to the table level A corresponding to 
the thickness of the tape 1 to be wound and and located in the 
longitudinal direction of the tube 12 to be wound (FIGS. 1 through 8), 
which support element has a length which encompasses at least two, but 
preferably three or four windings of the tube 12. Below the hollow 
cylindrical bar 2 a sluable bending plate 4 is situated in the guide table 
9 in the region of the incoming tape 1, the length of which bending plate 
4 is approximately that of the bar 2. The upper side of the bending plate 
4 lies at the table level A and two strips 29 extending in the 
longitudinal direction of the tube 12 being wound are located on the 
underside of the bending plate 4. The bending plate extends, beginning at 
a vertical axial level through the hollow cylindrical bar 2 on to the side 
of the incoming tape 1 opposite in relation to the bar 2. The half of the 
casing of the hollow cylindrical bar 2 pointing downward forms a convexly 
curved conducting surface 3, along which the incoming tape 1 can be bent 
with the aid of the bending plate 4. The inlet side of the conducting 
surface 3 for bending the tape 1 is situated in the vertical axial level 
through the hollow cylindrical tube 2, thus an the narrowest point of the 
aperture between the bar 2 and the table level A, and the outlet side 
correspondingly shifts in accordance with the interior angle to be bent by 
the appropriate circular measure. The bending plate 4 is guided at the 
time of the sluing motion from table level A upward one the one hand in 
circular guide slots 11 in the plate-shaped supports 27 through a trunnion 
20 protruding laterally from the strips 29, whereby in lieu of the 
penetrating trunnions 20 as shown in the illustrations trunnions only 
slightly overhanging the strips 29 can be provided, and on the other hand 
moves via activating levers 5 hinged to the strips 29. The predominant 
direction of motion of the activating lever runs approximately vertically 
upward, whereby the upper side of the bending plate 4 (with, of course the 
tape 1 to be moved in the intermediate position) rolls off one the 
conducting surface 3 and in so doing traverses all tangential levels to 
the conducting surface 3 between the starting position shown in complete 
lines in FIG. 9 and the final bending position shown in dash lines for a 
90-degree bending angle. The movement of the bending plate 4 thus 
represents a revolution around the axis of the hollow cylindrical bar 2, 
whereby it is continuously pressed centripetally to the conducting surface 
3. Since the sluing speed of the bending plate 4 will preferably be 
coordinated with the feed-in speed of the continually incoming tape 1, 
there will only be a slightly relative motion between the tape undergoing 
bending and the bending plate, and this may only be attributed to the 
oblique input angle of the tape. 
Just opposite the bending plate, thus on the inlet side of the bar 2, a 
support plate 21 has been provided which is displaced in the longitudinal 
direction against the bending plate 4. 
The support plate 21, which is also sluable upward from the table level A, 
serves the purpose of assuming the segment of tube just produced during 
each bending procedure when the unstable position of equilibrium has been 
exceeded and of supporting it relevant to the further tilting through the 
bending plate 4 moving upward into the final bending position to the 
return to contact on the table level A. The supporting plate 21 is formed 
essentially symmetrical for this purpose and arranged thus, i.e. it has at 
least one strip 30 on its lower side, from which on either side a trunnion 
22 protrudes, which trunnion can be shifted in circular guide slots 23 of 
additional plate-shaped supports 27. The upper side of this support plate 
21 rolls during the shifting in the conducting surface 3 as well (and, of 
course, also on the outer side of already produced tube windings that are 
being centripetally guided during this procedure), whereby at least one 
activating 25 is hinged to the strip(s) 30 of the support plate 21. 
The sequence of movements of the bending plate 4 and the support plate 21 
is controlled by a cam operation. According to FIGS. 1-9, two cam disks 7, 
24 are arranged on a drive drive 8 in the preferred embodiment, and along 
their controlling curves rollers 18, 19 fixed on each intermediate lever 
6, 26 roll during rotation. The intermediate lever 6 is hinged to the 
activating lever 5 of the bending plate and the intermediate lever 26 is 
hinged to the activating lever 25 of the support plate 21. The control 
curves of the two cam disks 7, 24 are differently shaped. 
According to the FIGS. 12 through 17 showing additional embodiments, the 
control of the activating lever 5, 25 is not performed by cam disks. In 
lieu of these, arms 31, 32 protruding radially from the drive shaft 8 are 
employed that have tangs 33, 34 on the end. In the course of rotation 
these are aligned via angle areas to stop grooves 35, 36 provided at the 
ends of the activating levers 5, 25. The drive shaft 8 of the two arms 31, 
32 situated diametrically opposite one another can be connected to the 
main drive via a magneto coupling, for example. 
A disk is also attached to the drive shaft 8, on the circumference of which 
a notch 37 is formed to define the rest positon. A stop lever acted on by 
an initial compressed air cylinder 42 engages in the notch 37. A second 
compressed air cylinder 43 bears a ram 39 for putting the activating lever 
5 into action. Two additional compressed air cylinders 44, 45 are assigned 
to the activating lever 25 and these move the rams 40, 41, whereby the ram 
41 is provided for coming to rest on a projection 46, which stands out 
from the free end of the activating lever 25 toward the outside. In 
addition, a restoring spring 47, shown only schematically, between the 
frame of the device and the activating lever 25 has been supplied, whereby 
a detent (not shown) lies in the restoring path of the activating lever 
25. 
The process will be explained in greater detail for manufacturing tubes 12, 
with reference to FIGS. 1 through 8. FIG. 1 shows at least one winding of 
the tube 12. The tape 1, in each of the illustrations as seen on the 
right, on the guide table 9 into the mechanism. According to FIGS. 1 and 
2, the portion of the tube 12 already produced pushed on unimpeded to the 
left, whereby the bending plate 4 and the support plate 21 are lowered in 
the guide table 9. According to the relevant length the lower, rounded 
edge region of the tube 12 (at right in the drawing) applies itself to the 
right half of the conducting surface 3 of the bar 2. Since the feed of the 
tape 1 is not interrupted, the portion of the tube already produced must 
turn upward (FIGS. 3-6), whereby the bending plate 4 turns upward via the 
cam control and the tape 1 is guided centripetally around the bar along 
the left half of the conducting surface 3, so that any deformation of the 
tube will be prevented and the tape 1 is bent exactly. As will be seen in 
FIGS. 3 and 4, the support plate 21 also shifts simultaneously with the 
bending plate 4, and it is shifted upward, as mentioned, from the guide 
table 9 and rests against the tube 12. Thus the turning point of the 
shifting movement of the support plate 21 is reached, which, controlled 
via the cam disk 24 and the two activating levers 26, 26, again moves 
downward into the guide table 9, whereby it (FIG. 5) supports the tube 12 
when it exceeds the unstable point of equilibrium while the bending plate 
4 is once more raised upward until the conclusion of the bending process 
(FIG. 6). The trunnions 20, 22 of the bending plate 4 and the support 
plate 21 move in the guide slots 11 and 23, whereby the arc length of the 
guide slot 23 for the support plate 21 is shorter than the guide slot 11 
for the bending plate 4. As soon as the final bending position in 
accordance with FIG. 6 has been attained, the trunnion 20 is fixed in 
place, through which means an axis 10 fixed to the table is formed (FIGS. 
7, 9). This is accomplished by means of a stop lever 13 activated by a 
sping (FIGS. 9, 11), which lever can be slued below the bending plate 4 
around an axis 28 and which has a stop catch, which comes to rest on the 
trunnion 20 when the final bending position is reached. The cam disk 7 has 
a slightly radially declining concluding flank, so that the activating 
lever 6 can drop directly downward, whereby the bending plate 4 revolves 
around the axis 10 fixed to the table. The bending place 4 thus lifts up 
very swiftly, precisely with a speed corresponding to that of at least the 
infeed speed of the tape, and laterally from the conducting surface 3 as 
well as the tape bending upward, by means of which, owing to the rounded 
edge region thus, the continuous advance of the tape is not obstructed 
(FIG. 8). The cam disks 7, 24 rotate back into the starting position and 
are not put into motion again until the beginning of the next bending 
sequence. 
The stop lever 13 has a disengaging extension 14, which is activated by the 
lowering bending plate 4 in the final portion of the path of movement. The 
stop lever 13 is accordingly depressed downward and frees the trunnion 20 
again, by which means the axis 10 fixed to the table is once more removed. 
The bending plate 4 shifted back into the guide table 9 can return to 
starting position during the further advance of the tape 1, for which 
purpose restoring mechanisms (not shown in the drawing) serve. 
In order to be able to wind longer tubes 12 at least one pair of plates has 
been provided at the end of the tube, both of which are installed and 
controlled in the same manner and which pair moves along with the tube in 
the longitudinal direction, whereby here in lieu of the bending plate 4 a 
second support plate is provided to carry out this function. 
According to the device illustrated in FIGS. 12 through 17 the activating 
levers 5, 25 are controlled in the following manner: 
The bending procedure is started up from the rest position shown in FIG. 12 
by an electrical impulse. This activates the magneto coupling mentioned of 
the drive shaft 8 and the two compressed air cylinders 42 and 45. The 
drive shaft 8 is connected to the main drive via the magneto coupling by 
the way of a countershaft, whereby a choice of gear ratios for the speed 
of rotation of the drive shaft 8 allows for adaptation to the infeed speed 
of the tape 1. The stop ram 38 of the compressed air cylinder 42 is 
withdrawn from the notch 38 and sets the revolving arms 31, 32 mounted on 
the drive shaft 8 into motion. Activation of the compressed air cylinder 
45 pulls in the ram 41 lodged on the projection 46, so that the activating 
lever 25 under the effect of the spring 47 is pulled up into the position 
shown in FIG. 13, so that the support plate 21 is turned by 45 degrees 
into the starting position. The tang 35 [sic] of the first arm 31 in rest 
position (FIG. 12) reaches into the stop groove 35 of the activating lever 
5. The beginning rotation of the arms 31, 32 now effects the return motion 
of the revolving process since the bending plate 4 is shifted upward by 
the activating lever 5. In the intermediate position shown in FIG. 14 the 
two arms 31, 32 extend horizontally and the bending plate 4 has been moved 
upward by 45 degrees, so that this together with the support plate 21 form 
a right angle. The detent for the activating lever 25 of the support plate 
21 is arranged in such an manner that the stop groove 36 of the activating 
lever 25 is situated at the level of the drive shaft 8, so that in the 
intermediate position as shown in FIG. 14 the tang 34 of the arm 32 clicks 
into the stop groove 36. At the time of rotation into the position as 
depicted in FIG. 15 the two activating levers 5, 25 are positively guided 
by the arms 31, 32, so that the bending plate 4 is shifted further upwards 
and the support plate 21, which is increasingly assuming the weight of the 
tube under construction, shuts back to the table level. The bending 
process is completed in the position according to FIG. 15, whereby the 
stop lever 13 interlocks the trunnion in the axis 10. In this position the 
compressed air cylinder 43 is activated, the ram of which 39 deflects the 
activating lever 5 so far to the side that the tang 33 moves out of the 
stop groove 35, through which means the connection with the arm 31 is 
disengaged. Through this means the bending plate 4 drops or flaps back 
around the axis 10 into the table level, so that the continued advance of 
the tape is not impeded. At the same time, however, the compressed air 
cylinders 44 and 45 are activated, so that the ram 41 of the cylinder 45 
is moved back into the catch position and the activating lever 25 is 
deflected by the ram 40 of the cylinder 44. At the same time the 
projection 46 is lodged on the ram 41 of the cylinder 45 and the tang 34 
slides out of the stop groove 36, by which means the support plate 21 is 
retained at the table level. The rams 39 and 40 are again restored during 
the further rotation of the arms 31, 32 (FIG. 17). As soon as the notch 37 
has once more come into the starting or rest position according to FIG. 
12, the stop ram 38 engages in it while the drive shaft 8 is uncoupled. 
The cam steering is thus finished for this bending sequence. 
During the remainder of the rotation of the arms 31, 32 into the rest 
position (FIG. 15, FIG. 17, FIG. 12) the restoration of the bending plate 
4 to table level takes place, whereby FIG. 16 shows an intermediate 
position in detail that can be assigned roughly to follow the intermediate 
position shown in FIG. 17 of the cam steering. The guide slot 11 for the 
trunnion 20 has a straight-line return stretch 48, so that the bending 
plate 4 is brought back into the starting position in a horizontal motion 
by the pull-back mechanism. For this purpose the beginning of the convex 
guide slot 11 must be bridged. The stop lever 13 for this purpose has a 
segment 49 connecting to its detent, which segment aligns with the 
straight line return stretch 48 in the close-back position of the bending 
plate 4, through which means this part exclusively of the guide slot 11 is 
free. When the bending plate 4 shifts upwards, the spring-loaded stop 
lever 13 switches downward, so that the shifting motion of the bending 
plate 4 is not obstructed. 
The connecting device which connects the incoming tape 1 to the last 
winding of the tube is in itself not a component of the present invention 
and can, for example comprise a pair of folding rollers, of which one 
closing roller 15 is provided in the interior of the emerging tube 12 and 
the other on the outside. The connection or fold-closing is accomplished 
in an especially simple manner at the single location that does not shift 
relative to the guide table and through which the tube runs during 
winding, viz. in the vertical axial level of the bar 2, thus at the 
narrowest point of the through-put aperture. 
The inner closing roller 15 is situated on axis jutting diagonally into the 
hollow cylindrical bar 2 or situated on a driven shaft 16 likewise 
positioned, whereby within the conducting surface 2 a penetration aperture 
17 has been provided in the wall of the bar 2 (FIGS. 10, 11), so that the 
closing roller 15 is in direct contact with the connecting area between 
the tape 1 and the winding of the tube 12. The counter roller on the 
outside is situated in the guide table 9 below the closing roller 15, but 
has not been depicted for reasons of clarity in viewing. Since the infeed 
angle of the tape 1 must be altered, depending on the width of the tape 1 
and the size of the tube 12 to be produced, the closing roller 15 and the 
counter roller opposite it are sluable around the imagined vertical axis 
extending through the axis of the bar 2 and the midpoint of the two 
connecting rollers. In FIGS. 10 and 11 the maximum angle of traverse is 
depicted, respectively, between the shaft 16 and the bar 2. 
If the tube windings are connecting by a fold as is made possible by the 
closing roller 15 illustrated, the bending plate 4 and the support place 
21 will have indentations (not shown) into which the grooved edges of the 
tape 1 and the grooves between the windings impinge, so that the bending 
plate 4 and the support plate 21 have contact over the entire width of 
each winding and it is possible to guide the material with precision along 
the conducting surface. As mentioned, welding rollers can also be 
installed with which to weld the material. 
The process in accordance with the present invention is suitable for the 
production of continuously wound tubes having essentially rectangular 
cross-sectional areas since both the interior angle to be bent and the 
length of the side can be selected.