Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: "EDGE-BENDING PRESS"
DESCRIPTION
The present invention relates to an edge-bending press
and in particular relates to an edge-bending press
suitable for processing metal sheets for the production
of longitudinally welded pipes.
It is known to use flat metal sheets for the production
of longitudinally welded pipes. The sheets undergo
successive processing operations in order to form the
pipe. During a first step the longitudinal edges of the
sheets are chamfered. During a second step, using an
edge-bending press (or crimping press), the
longitudinal edges are deformed with a radius of
curvature equivalent to that of the finished pipe.
During the third step the sheet is deformed until it
assumes a U-shaped cross-section. During the fourth
step the sheet is deformed until it assumes a cross-
section in the form of an open "0". During the fifth
and final step the sheet is welded longitudinally so as
to close the 0-shaped cross-section and obtain the
finished pipe.
The present invention relates to an edge-bending press
for imparting a curvature to the edges of the sheets.
This operation is illustrated generally in Figures 1 to
3.
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Usually this operation is completed by means of two
presses with an open C-shaped frame. The two presses
are situated opposite each other and positioned at a
suitable distance so that each one operates on one of
the two longitudinal edges of the sheet. This solution
is described for example in the patent US 3,911,709.
With this known solution it is possible to obtain, by
displacing one press with respect to the other one,
configurations suitable for the different widths of the
sheets to be processed. The width of the sheet is in
fact variable from a minimum of about 2 m to a maximum
of about 4.5 m, depending on the different diameters of
the pipe which is to be obtained.
In order to help one understand better the technical
subject it should be mentioned here that the edge-
bending presses designed for the described function are
able to generate a force in the direction of operation
(referred to as "separation force" and regarded below
as vertical) which is of the order of thousands of
tonnes. This force is necessary in order to be able to
bend sheets of considerable thickness, for example
thicknesses which are of the order of some centimetres.
During each of the bending operations, the sheet reacts
to the separation force applied by the press, with a
complex system of reaction forces. With respect to
external effects, these reaction forces may be regarded
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as a vertical resultant, a horizontal resultant and a
moment.
This solution of oppositely arranged C-shaped presses,
although widely used, is not defect-free.
The most evident defect relates to the structure of the
two presses. In fact each of the two presses must
oppose reaction forces of the sheet, which have a
markedly asymmetrical structure. Even if the reaction
forces generated by an edge of the sheet are a perfect
mirror-image of the forces generated by the other edge,
the fact that the two C-shaped presses are separate
from each other does not allow the two systems of
forces to be closed in such a way as to cancel out each
other. Finally, the open configuration of the two C-
shaped presses does not allow the structure of the said
presses to be exploited in the best possible manner.
Owing to the abovementioned factors, each of the two C-
shaped presses is subject to a notable overturning
moment. The overall system must take account of this
moment, allowing each of the two presses to perform a
limited rotational movement in order to comply
partially with this moment.
This type of response involves the use of particularly
complex constraining devices for each of the two
presses.
A further known solution is described for example in
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the patent application EP 1 958 712. This solution
envisages the use of an edge-bending press with a
closed frame in which double rams for positioning the
die-holders are fixed to the centre of each of the
platens or platens.
This solution, although it solves partly some of the
problems associated with the open structure of the C-
shaped presses, continues to have a number of
drawbacks.
Serious problems may arise, for example, should the
system of reaction forces generated during operation of
the press be asymmetrical, for example owing to
incorrect positioning of the sheet. In this case, the
system of reaction forces is not symmetrical: a lateral
thrust is in fact generated on one of the two edges and
is not compensated by any equal and opposite thrust
generated on the other edge of the sheet. This lateral
thrust, which may reach values of the order of some
thousand tonnes, is transmitted to the central support
of the die-holder positioning double ram. Obviously
this support may be suitably designed so as to
withstand such lateral forces, but only by providing
the structure with excessively large dimensions.
The object of the present invention is therefore to
overcome at least partly the drawbacks mentioned above
with reference to the prior art.
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In particular, one task of the present invention is to
provide an edge-bending press such that a closed system
of reaction forces is obtained on the two edges of the
sheet, resulting in a system of forces which is
symmetrical and zero with respect to external effects.
The abovementioned object and tasks are achieved by an
edge-bending press in accordance with that claimed in
Claim 1.
The characteristic features and further advantages of
the invention will emerge from the description provided
hereinbelow, of a number of examples of embodiments,
provided by way of a non-limiting example, with
reference to the accompanying drawings in which:
- Figure 1 shows a schematic cross-sectional view of a
generic edge-bending press during a first working step;
- Figure 2 shows a view of the press according to
Figure 1 during a second working step;
- Figure 3 shows a view of the press according to
Figure 1 during a third working step;
- Figure 4 shows a partially cross-sectioned front view
of an edge-bending press according to the invention;
- Figures 5.a to 5.d show successive configurations of
a press according to the invention;
- Figure 6 shows a cross-sectional view along the line
VI-VI in Figure 5.c;
- Figure 7 shows a view, similar to that of Figure 4,
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of another edge-bending press according to the
invention;
- Figure 8 shows a partial view of the cross-section
along the line VIII-VIII in Figure 7, where some parts
have been removed for greater clarity.
With reference to the accompanying Figure 4, 10 denotes
in its entirety an edge-bending press according to the
invention, while 100 denotes the sheet being processed.
The edge-bending press 10 according to the invention
comprises an upper platen 12, a lower platen 14 and
operating actuators 16. The operating actuators 16 are
designed to cause a relative movement of the upper
platen 12 and lower platen 14' towards and/or away from
each other. The press 10 also comprises an upper die-
holder assembly 22 which is connected to the upper
platen 12 and a lower die-holder assembly 24 which is
connected to the lower platen 14. Each die-holder
assembly 22, 24 comprises a right-hand die-holder and a
left-hand die-holder; thus there is an upper right-hand
die-holder 222, an upper left-hand die-holder 224, a
lower right-hand die-holder 242 and a lower left-hand
die-holder 244. The press 10 according to the invention
also comprises adjustment actuators 18 designed to
cause a relative movement of the right-hand die-holders
222, 242 and the left-hand die-holders 224, 244 towards
and/or away from each other. The press 10 according to
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the invention also comprises centring actuators 20
designed to impart a movement involving displacement of
the die-holder assemblies 22, 24 along the platens 12,
14.
Here and below the vertical and horizontal directions
refer to the condition where the press 10 is correctly
installed and in working order. Furthermore, the
longitudinal direction is understood as being the
horizontal direction for feeding the sheet 100 to the
press 10; the transverse direction is understood as
being the horizontal direction perpendicular to the
longitudinal direction.
Here and below the terms, top, upper, up, overlying and
the like and the terms bottom, lower, low, underlying
and the like refer to the press 10 correctly installed
and in working order. Similarly, the reference to
right-hand and left-hand is based on a view of the
press 10 which is similar to that in Figure 4.
Obviously the right-hand and left-hand positions could
be equally well reversed.
In accordance with one embodiment, the press 10
according to the invention also comprises a frame 26 on
which the platens and the actuators are mounted. The
frame 26 rests on a base and comprises preferably an
upper horizontal member 262 and a lower horizontal
member 264. The two horizontal members are connected by
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a right-hand vertical member 266 and a left-hand
vertical member 268.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the upper platen 12 is
fixed on the frame 26, while the lower platen 14 is
movable as a result of the action of the operating
actuators 16. In accordance with other possible
embodiments, on the other hand, the upper platen 12 is
movable and the lower platen 14 is.fixed.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the operating actuators 16
comprise hydraulic actuators of the cylinder and piston
type. The operating actuators 16 act in the vertical
direction.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the operating actuators 16
are positioned at the top of the upper platen 12 and
act on the lower platen 14 by means of tie-rods 160.
In accordance with one embodiment of the press 10, the
operating actuators 16 comprise an auxiliary cylinder
and piston unit (not shown in the Figures) and a main
cylinder and piston unit 164. The two auxiliary and
main units 164 are preferably arranged in a parallel
configuration. The function and the interaction between
the two cylinder and piston units, i.e. auxiliary unit
and main unit 164, is explained in detail below.
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In accordance with the embodiment of the press 10 shown
in the accompanying figures, convex dies 226 are
mounted on the upper die-holder assembly 22, while
concave dies 246 are mounted on the lower die-holder
assembly 24. In accordance with other embodiments and
without any differences in terms of operation, concave
dies are mounted on the upper die-holder assembly,
while convex dies are mounted on the lower die-holder
assembly.
The dies 226, 246 are interchangeable so as to allow
replacement of the worn dies, but in particular so as
make it possible to achieve different radii of
curvature for the edges of the sheets. The curvature to
be imparted to the edges of the sheet 100 in fact
depends on the diameter of the finished pipe to be
obtained.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the adjustment actuators
18 comprise hydraulic actuators of the cylinder and
piston type. In particular, the adjustment actuators 18
comprise an upper adjustment actuator 182 and a lower
adjustment actuator 184. The adjustment actuators 18
act in the transverse direction.
In accordance with other possible embodiments, the
adjustment actuators 18 may be mechanical instead of
hydraulic in nature. Mechanical actuators which are
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suitable for this purpose may be threaded-bar actuators
or rack-and-pinion actuators.
The upper adjustment actuator 182 is mounted on the
upper platen 12, while the lower adjustment actuator
184 is mounted on the lower platen 14. The adjustment
actuators 18 are mounted on the respective platens so
as to be able to slide in the transverse direction
relative thereto. The adjustment actuators 18 may, for
example, be mounted by means of tracks, rails or the
like.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the upper right-hand die-
holders 222 and the upper left-hand die-holders 224 are
fixed to the upper adjustment actuator 182. Similarly,
the lower right-hand die-holder 242 and the lower left-
hand die-holder 244 are fixed to the lower adjustment
actuator 184. In particular, the upper right-hand die-
holder 222 is rigidly fixed to the outer casing 182" of
the cylinder, while the upper left-hand die-holder 224
is rigidly fixed to the end 182' of the piston rod.
Similarly, the lower right-hand die-holder 242 is
rigidly fixed to the outer casing 184" of the cylinder,
while the lower left-hand die-holder 244 is rigidly
fixed to the end 184' of the piston rod.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the centring actuators 20
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comprise hydraulic actuators of the cylinder and piston
type. In particular, the centring actuators 20 comprise
an upper centring actuator 202 and a lower centring
actuator 204. The centring actuators 20 act in the
transverse direction.
In accordance with other possible embodiments, the
centring actuators 20 may be mechanical instead of
hydraulic in nature. Mechanical actuators which are
suitable for this purpose are threaded-bar actuators or
rack-and-pinion actuators.
The upper centring actuator 202 is mounted on the upper
platen 12, while the lower centring actuator 204 is
mounted on the lower platen 14. In particular, the
outer casing 202" of the cylinder of the upper centring
actuator 202 is rigidly connected to the upper platen
12. The end 202' of the piston rod of the upper
centring actuator 202 is connected to the upper
adjustment actuator 182. The outer casing 204" of the
cylinder of the lower centring actuator 204 is rigidly
connected to the lower platen 14. The end 204' of the
piston rod of the lower centring actuator 204 is
connected to the lower adjustment actuator 184.
As can be clearly seen in Figure 4, the end 202' of the
piston rod of the upper centring actuator 202 is
connected to the upper adjustment actuator 182 by means
of the upper left-hand die-holder 224. Respectively,
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the end 204' of the piston rod of the lower centring
actuator 204 is connected to the lower adjustment
actuator 184 by means of the lower left-hand die-holder
224. Obviously, other configurations may be adopted,
provided that operation of the centring actuators is
able to move the adjustment actuators and the die-
holders fixed thereto.
In accordance with the embodiment of the press 10 shown
in the accompanying figures, the upper platen 12
comprises a fixing plate 120 to which the outer casing
202" of the cylinder of the upper centring actuator 202
is rigidly fixed. Similarly, the lower platen 14
comprises a fixing plate 140 to which the outer casing
204" of the cylinder of the lower centring actuator 204
is rigidly fixed.
In accordance with one embodiment of the invention, the
centring actuators 20 comprise adjustable safety valves
(not shown in the figures).
In accordance with the. embodiment shown in the
accompanying figures, the press 10 also comprises means
28 for moving the sheet 100 and/or means 30 for
clamping the sheet.
In a manner known per se, the means 30 comprise
(hydraulic or mechanical) actuators with respective
abutments. The means 30 are able to exert on the sheet
100 a clamping force such as to keep the sheet itself
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in the correct position also in response to
disturbances in the system of forces generated during
operation of the press 10. This clamping force may be
quantified as being a good 20% of the force which the
press 10 requires in order to perform bending of the
edges (or crimping).
The clamping means 30 are mounted in a manner known per
se on straight guides so as to be able to slide in the
transverse direction together with the die-holders. The
clamping means 30 must in fact be able to act in the
vicinity of the edges of sheets of various widths.
In accordance with the embodiment shown in Figures 4
and 5, the clamping means 30 are mounted, in a manner
known per se, between the lower platen 14 and the upper
platen 12 of the press 100. In this configuration,
during the crimping action, the operating actuators 16
must also overcome the force exerted by the clamping
means 30.
In accordance with the embodiment shown in Figures 7
and 8, the clamping means 30 are instead mounted on the
frame 26. In particular, the clamping means 30 are
mounted on the lower horizontal member 264 by means of
straight guides so as to be able to slide in the
transverse direction together with the die-holders. The
clamping means 30 must in fact be able to act in the
vicinity of the edges of sheets of various widths.
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In this configuration, during the crimping action, the
force exerted by the clamping means 30 does not
influence the force of the operating actuators 16. As a
result of this solution, therefore, the operating
actuators 16 may be designed so as to develop a force
about 20% less than that of the preceding solution. All
other factors being equal, it can be noted how this
solution achieves a significant reduction in the
dimensions and operation of the operating actuators 16
and the associated power supply plant.
In accordance with a number of embodiments, the press
according to the invention also comprises means for
controlling the operating movements, for example for
controlling the hydraulic and/or mechanical operating,
adjustment and/or centring actuators. The control
.means may advantageously comprise some of the following
components: a user interface designed to receive
commands from a user; pressure sensors able to detect
the internal pressure of the hydraulic actuators; load
cells able to detect the force exerted at a given
point; displacement sensors able to detect the relative
position of given components; safety sensors; actuating
devices able to cause the displacement of the various
hydraulic actuators; a processing unit designed to
collect the signals received from the user interface
and from the various sensors and operate the actuating
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devices depending on a predefined logic.
In accordance with the embodiment shown in Figure 6,
the press 10 comprises a plurality of stations which
are arranged next to each other in the longitudinal
direction. Each station corresponds to the description
given above and comprises an upper platen 12, a lower
platen 14, operating actuators 16, die-holder
assemblies 22 and 24, adjustment actuators 18 and
centring actuators 20.
In accordance with one embodiment (not shown) of the
invention, the movable platens of the plurality of
stations are connected together in the longitudinal
direction by a middle member mounted between the said
platens and the die-holders. This middle member, where
present, may help improve mechanical synchronization of
the various stations.
In the light of the structural description given above,
operation of the press 10, in particular the operations
necessary for reconfiguring and using a press 10
according to the invention, will now be described
briefly.
Figure 5.a shows a press 10 according to the invention
in a configuration similar to that of Figure 4. In this
configuration, considered by way of example, the press
10 is able to operate on sheets of maximum width (in
the specific example about 4.5 m). It is assumed below,
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again by way of example, that it is required to
reconfigure the press 10 so as to be able to operate on
sheets of different width, for example minimum width
(in the specific example about 1.9 m). In order to
reconfigure the press 10 it is necessary first of all
to mount the upper (e.g. convex) dies 226 and the lower
(e.g. concave) dies 246 suitable for the minimum width
of the sheet, i.e. dies which are designed to impart to
the edges of the sheet 100 the curvature of a
circumference having an extension of 1.9 m.
It is then required to move the right-hand and left-
hand die-holders with the associated dies towards each
other. Figure 5.b shows a first temporary configuration
of the press 10 where the adjustment actuators 182 and
184 caused a relative movement of the right-hand die-
holders and left-hand die-holders towards each other.
As can be noted by comparing Figure 5.a with Figure
5.b, this temporary configuration is obtained by
keeping immobile the ends 182' and 184' of the piston
rods of the upper adjustment actuator 182 and lower
adjustment actuator 184, and therefore by keeping
immobile the left-hand die-holders 224 and 244. The
relative approach movement is obtained by means of the
movement of the outer casings 182" and 184" of the
upper adjustment actuator 182 and lower adjustment
actuator 184. This movement therefore involves the
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movement of the right-hand die-holders 222 and 242.
Asymmetrical positioning of the die-holders relative to
the centre of the press 10 is thus produced.
The asymmetrical configuration obtained would result in
an asymmetrical load on the platens and therefore on
the operating actuators 16 during crimping. It is
therefore required firstly to displace rigidly the
upper die-holder assembly 22 and lower die-holder
assembly 24 so as to reposition them in a symmetrical
configuration relative to the centre of the press 10.
This rigid displacement of the die-holder assemblies 22
and 24 is obtained by means of the upper centring
actuator 202 and lower centring actuator 204,
respectively.
The symmetrical configuration thus obtained is shown in
Figure 5.c, in which the sheet 100 correctly positioned
between the dies is also shown. The sheet 100 is
preferably brought into the position shown in Figure
5.c via the movement means 28. The press 10 in the
configuration shown in Figure 5.c is therefore ready
for performing crimping of the sheet 100.
The succession of movements of the dies described above
is merely exemplary and is intended to describe from a
logical point of view the steps required for
configuration. It is obviously equally possible, in
other embodiments, for the centring actuators 20 to be
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operated first, followed by the adjustment actuators
18, or also for the centring actuators 20 and the
adjustment actuators 18 to be operated simultaneously.
At this point, it is preferable to operate the clamping
means 30, if present, in a manner known per se and as
schematically illustrated in Figure 2. The use of the
clamping means 30 allows the sheet to be kept in
position also in the case of small disturbances in the
system of forces.
The next operation is that of activating the operating
actuators 16. In accordance with some embodiments and
as described above, the operating actuators 16 comprise
an auxiliary cylinder and piston unit (not shown) and a
main cylinder and piston unit 164. The auxiliary piston
has a working area which is decidedly smaller than that
of the main piston. Since the two units, i.e. auxiliary
unit and main unit 164, are supplied by the same
hydraulic plant, the auxiliary unit is able to provide
a smaller force (the oil pressure acts on a smaller
surface area), while ensuring a faster movement (the
oil flow must supply a smaller volume) . On the other
hand, the main unit 164 is able to provide a greater
force (the oil pressure acts on a larger surface area),
but with a slower movement (the oil flow must supply a
larger volume).
The auxiliary unit is therefore useful during the
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stroke performed by the lower platen 14 from the
position shown in Figure 5.c into the position where
the dies start to come into contact with the sheet 100.
This stroke in fact requires a minimum force since it
must overcome only the weight force of the lower platen
14 and the internal resistance of the press 10, while
there is no reaction to be overcome on the part of the
sheet 100. The main unit 164 instead intervenes when
the reaction forces of the sheet 100 start to be
generated. By means of the operating actuators 16 it is
therefore possible to obtain crimping of the sheet 100,
as shown in Figure 3 and Figure 5.d.
As mentioned above, during crimping, a complex system
of reaction forces arises on the part of the sheet 100.
This system of forces is, limited to each of the two
edges of the sheet, highly asymmetrical. Each edge of
the sheet therefore introduces an overturning moment
acting on the press 10 and a lateral force which tends
to displace the dies in the transverse direction. The
reaction forces produced by the right-hand edge and
left-hand edge are, in ideal conditions, identical. As
a result, when the structure of the press 10 is closed,
the right-hand reaction forces are cancelled out by the
left-hand reaction forces so as to produce a zero force
system with respect to external effects.
Obviously, inside the press 10 the reaction forces
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produced by the sheet 100 must be effectively opposed.
In particular, the adjustment actuators 18 must be able
to maintain the predefined distance between the dies
also during crimping, i.e. in response to transverse
forces equivalent to thousands of tonnes. This control
over the relative position of the dies is achieved in a
known manner by means of the hydraulic system of the
adjustment actuators 18. In ideal conditions,
therefore, the force which is transmitted onto the
fixing plates 120 and 140 during crimping has a zero
value.
It is possible, however, to obtain an asymmetrical
reaction, for example because the two edges of the
sheet 100 do not react in a symmetrical manner or
because the sheet 100 is incorrectly positioned. In
such a case the transverse reaction of one of the two
edges is not offset nor compensated by the reaction of
the other edge. This therefore produces a transverse
force on the centring actuators 20 and, in turn, on the
fixing plates 120 and 140. In such a situation the
safety valves of the centring actuators 20 described
above become useful. These safety valves allow a
threshold value for the pressure inside the actuator to
be predefined. When the threshold value is reached, the
safety valve is designed to open a vent so as to limit
the pressure inside the actuator. In other words, when
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the threshold value is reached, the safety valve is
designed to allow oil to flow out from inside the
actuator towards the storage tank. It should be noted
that the safety valves may be constructed with an
extremely simple and therefore reliable design. In
order to limit the pressure to a predefined value it is
in fact sufficient to use a mechanical valve which can
preferably be pre-loaded in a variable manner depending
on the specific requirements. It is thus possible to
limit in a very simple manner to a predefined value the
forces which may be transmitted by the centring
actuators 202 and 204 onto the respective fixing plates
120 and 140, for example in the case of a non-
symmetrical system of reaction forces on the part of
the sheet 100.
This operating logic may also be adopted in the case of
an edge-bending press of the known type in which die-
holder positioning double rams are fixed to the centre
of the platens. In this case, the safety device must
comprise a sensor for detecting the pressure inside
each of the two chambers of the said double ram and a
circuit which limits the difference between the two
pressures to a predetermined value. When the threshold
value is reached, the safety device is designed to
block operation of the press. It should be noted
therefore how this safety device required by the
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configuration of the prior art is in fact more complex
and therefore necessarily less reliable and robust than
the simple safety valve of the press according to the
invention.
In accordance with one embodiment, the press 10
according to the invention comprises means for
operating simultaneously, during the crimping step, the
centring actuators 20 and the adjustment actuators 18.
In this way it is possible to impart to the dies a
movement away from each other in the transverse
direction during the approach movement in the vertical
direction. This function of the edge-bending press is
useful for limiting or preventing slipping of the sheet
on the dies.
With regard to the embodiments of the edge-bending
press 10 described above, the person skilled in the art
may, in order to satisfy specific requirements, make
modifications to and/or replace parts described with
equivalent parts, without thereby departing from the
scope of the accompanying claims.
