Note: Descriptions are shown in the official language in which they were submitted.
1 CA 02539332 2006-03-16
r
29019/W0/1
DaimlerChrysler AG
Method and device for producing a peripherally closed
hollow profiled element
The invention relates to a method for producing a
peripherally closed hollow profiled element according
to the preamble of patent claim 1 and to a device for
this purpose according to the preamble of patent
claim 2.
A generic device and a generic method are known from
EP 0 621 091 B1. An internal high-pressure forming
tool, which consists of an upper die and of a lower
die, may be gathered from said publication. The lower
die has a forming space which introduction slopes
adjoin upwardly. The upper die has on its underside a
ram-like extension which is beveled laterally according
to the introduction slopes. To produce a hollow
profiled element, then, a hollow profiled element blank
is laid onto the introduction slopes, after which the
ram-shaped extension squeezes the hollow profiled
element blank into the forming space of the lower die.
During the squeezing operation, creases, corrugations
and edges having different wall thicknesses and
inherent stresses arise in an uncontrolled way in the
hollow profiled element which has, in terms of its
height, an oversize, as compared with the forming
space. When the hollow profiled element blank lies
completely in the forming space, then, the latter has
an intermediate form which possesses a rough contour
approximating to the contour of the forming space. When
the forming tool is in the closed position, a fluidic
internal high pressure is then generated within the
hollow profiled element blank preprofiled in this way
and expands the hollow profiled element blank until it
comes to bear against the walls of the forming space
which are formed by the impression of the lower die. On
account of the abovementioned creases, corrugations and
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edges with different wall thicknesses and inherent
stresses and high degrees of hardening, during the
known preprofiling weak points are generated, at which
the risk of bursting of the hollow profiled element
blank is particularly high in the subsequent expanding
forming by means of internal high pressure.
Furthermore, the hollow profiled element blank is
spaced relatively far apart from the impression wall of
the forming space in the region of the creases, so that
the reduced expandability of the material still
available after squeezing is not sufficient to allow
complete expansion with a high degree of process
reliability.
The object on which the invention is based is to
develop a generic method to the effect that it becomes
possible to have internal high-pressure forming of a
hollow profiled element blank introduced with oversize
into the forming space and to be preprofiled into a
final form of the hollow profiled element with a high
degree of process reliability. A device which serves
for carrying out the method is likewise to be
specified.
The object is achieved, according to the invention, by
means of the features of patent claim 1 with regard to
the method and by means of the features of patent
claim 2 with regard to the device.
By virtue of the invention, the hollow profiled element
blank having oversize can be inserted in a simple way
into a lower portion of the forming space, without the
latter at the same time being deformed. During the
movement of closing the forming tool, then, at least
one slide is activated, which is guided laterally onto
the hollow profiled element blank by a drive means of
the device. Since the hollow profiled element blank
already lies in part of the forming space, the blank
can be pressed uniformly by the slide, thus avoiding a
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flow of substance of the blank material over an edge of
the forming tool, which causes creases and frictional
wear on the hollow profiled element blank. During the
pressing operation, the hollow profiled element blank
can spread out freely toward the upper die until the
upper die comes to lie on the lower die and closes off
the forming space upwardly. As a result of the free
spread of the hollow profiled element blank, the latter
comes on all sides relatively close to the impression
of the upper die, so that, during subsequent expansion
by means of internal high pressure, only a little
expandability of the hollow profiled element blank is
necessary in order to come to bear completely against
the impression. Since, during the preprofiling of the
hollow profiled element blank, no creases and similar
phenomena which are an impediment to forming occur on
the hollow profiled element blank, and the degree of
forming of the preprofiled intermediate form of the
hollow profiled element blank into the final form of
the hollow profiled element is low, a hollow profiled
element blank provided with oversize, as compared with
the forming space, can, on the one hand, be preprofiled
with a high degree of process reliability and, on the
other hand, be shaped into the final form of the hollow
profiled element with a high degree of process
reliability.
In a preferred development of the device according to
the invention, as claimed in claim 3, the pressing
surface of the slide forms an impression which at least
partially delimits the forming space laterally. The
device is thereby simplified in structural terms, since
the subsequent arrangement of an impression-carrying
tool segment may be dispensed with. Moreover, if
appropriate, after the preprofiling pressing operation,
the forming tool would have to be opened once again in
a complicated and time-consuming way in order to
replace the slide for the tool segment.
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In a further preferred development of the invention, as
claimed in claim 4, during the internal high-pressure
forming of the blank into the final form, the slide is
held at the rear by a supporting means. Although it is
conceivable that the slide can be detained by means of
a stop pin which can pass through a transverse bore of
the slide, a rear support is advantageous in that, on
the one hand, access to the rear side of the slide from
outside is very good and, on the other hand, the design
of the support can be kept simple in structural terms .
In this case, it is conceivable, for example, that the
support is taken over by a ram which is led up to the
slide from outside. A further simplification would be
that the drive means of the slide at the same time
affords the support.
In a preferred development of the device according to
the invention, as claimed in claim 5, the drive means
is an oblique tension column which is fixed in the
upper die and projects obliquely downward toward the
lower die, the column being inclined toward the forming
space. The slide in this case has a reception bore, the
run of which corresponds to the oblique extent of the
column and which is arranged with respect to the column
such that the latter penetrates into the reception bore
during the movement of closing the forming tool.
Although the drive means may have a pneumatic or
hydraulic basis, a mechanical solution is preferred
here, since it is far less complicated in terms of
apparatus. In this case, of course, it is conceivable
that the mechanical drive means is, for example, a ram
which, with regard to the internal high- pressure
forming tool, constitutes a separate component and
possesses a separate control. However, with the
proposed oblique tension column which is integrated
into the forming tool and which penetrates into a
reception bore of the slide during the closing
movement, the slide is displaced in a structurally
simple way between a position of non-use and a position
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of use solely as a result of the movement of closing or
opening the forming tool, so that separate controls and
the energy sources necessary for these may be dispensed
with so as to achieve a saving in outlay and in
resources. In order to bring about the automatic
movement of the slide, however, the oblique tension
column must be arranged so as to be inclined obliquely
toward the forming space and the reception bore of the
slide must be coordinated with the oblique run of the
column. As a result of the movement of penetration or
extraction of the guide column into or out of the
reception bore, the column acts upon the slide
according ~ to the wedge principle, so that the slide is
moved by positive control. For an ordered displacement
of the slide, it is in this case beneficial if the
slide is guided laterally. It may be stressed once
more, at this juncture, that, in said embodiment of the
invention as claimed in claim 5, by the function of the
drive means for the slide being transferred to the
forming tool, the outlay in terms of apparatus for the
device is reduced considerably and there is a saving in
construction space for the device.
In a further preferred embodiment of the invention, as
claimed in claim 6, the supporting means is the upper
die which engages behind the slide in the closed
position of the forming tool. By the supporting
function of the slide being taken over by the forming
tool, separate supporting means may be dispensed with,
thus leading to a structural simplification of the
device, and the outlay in terms of apparatus and in
terms of control can be reduced.
In a further preferred embodiment of the invention, as
claimed in claim 7, the upper die has, in its region
engaging behind the slide, a wedge surface, the angular
position of which corresponds to the angle of slope of
the oblique tension column and which, in the closed
position of the forming tool, bears against an
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identically angled wedge surface formed on the rear
side of the slide. By a wedge surface being arranged in
that region of the upper die in which the latter
engages behind the slide and by the wedge surface
bearing, in the closed position, against a wedge
surface which is formed on the rear side of the slide,
there is no risk of jamming between the slide and the
upper die of the forming tool. Furthermore, the wear
between the wedge surfaces, that is to say between the
upper die and the slide on its rear side, is minimized.
In a further preferred development of the invention, as
claimed in claim 8, a sliding plate, against which the
upper die bears with its region engaging behind the
slide, is arranged on the rear side of the slide. By
the rear side of the slide having arranged on it a
sliding plate which, moreover, may also alternatively
be fastened to the wedge surface of the upper die, the
friction between the upper die and the slide and
therefore the wear between the two is minimized.
The invention is explained in more detail below by
means of an exemplary embodiment illustrated in the
drawing.
In this case, the figure shows, in a lateral
longitudinal section, a device according to the
invention with an oblique tension column as drive means
of a slide and with an upper die, designed as
supporting means, of a forming tool of the device, the
figure being split in the illustration into an opening
position of the forming tool (on the left) and a closed
position of the forming tool (on the right).
The figure illustrates a device 1 for producing a
peripherally closed hollow profiled element by means of
fluidic internal high pressure, said device containing
an internal high-pressure forming tool 2. The latter is
composed of an upper die 3 and of a lower die 4, the
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impressions 5 and 6 of which enclose a forming space 7
for the hollow profiled element. The forming space 7
has inserted into it a hollow profiled element blank 8,
the diameter of which is larger than that of the
forming space 7. The device 1 comprises, furthermore, a
member for pressing the blank 8 in the internal high-
pressure forming tool 2, the member being formed by two
slides 9 which are seated on the lower die 4 of the
internal high-pressure forming tool 2 on the right and
left laterally with respect to the hollow profiled
element blank 8. Furthermore, the device 1 also
contains a fluid high-pressure generation system which
is fluidically connected at least to one end of the
hollow profiled element blank 8. The underside 10 of
the upper die 3 has worked into it oblique bores 11, in
which oblique tension columns 12 are arranged and
fixed. The oblique tension columns 12, one of which is
assigned in each case to a slide 9, project obliquely
downward toward the lower die 4, the columns 12 being
inclined toward the forming space 7. The oblique
tension columns 12 in each case form the drive means
for the slide 9, by means of which the slide 9 can be
moved between a position of use and a position of non-
use during the movement of opening and closing the
forming tool 2. The slide 9 has, for this purpose, a
reception bore 13 , the run of which corresponds to the
oblique extent of the column 12. The reception bore 13
is arranged in relation to the oblique tension column
12 such that the latter penetrates into the reception
bore 13 during the movement of closing the forming tool
2. The upper die 3 has, furthermore, on its underside
10, clearances 14, in which the slides are received
during the movement of closing the forming tool 2 and
in the closed position of the latter. The clearances 14
are open toward the forming space 7 and on the opposite
side possess a flank 15 which is designed as a wedge
surface. The angular position of the wedge surface
corresponds exactly to that of the angle of slope of
the oblique tension column 12. On the rear side 16 of
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the slide 9, said rear side facing away from the
forming space 7, a wedge surface 17 is likewise formed,
which is angled identically to the wedge surface of the
upper die 3. A sliding plate 18 is fastened to this
wedge surface 17.
To produce the hollow profiled element, the circular-
cylindrical hollow profiled element blank 8, the
diameter of which has a continuous oversize, as
compared with the diameter of the forming space 7, is
inserted into the depression-like impression 6 of the
lower die 4, said impression forming a lower portion of
the forming space 7. Subsequently, the upper die 3
moves toward the lower die 4, the oblique tension
columns 12, which possess an introduction phase at
their free end 19, penetrating into the reception bores
13 of the slides 9. On account of the resulting wedging
action between the columns 12 and the slide 9, the
latter is moved on the lower die 4 onto the tubular
hollow profiled element blank 8 transversely with
respect to the direction of the closing movement of the
forming tool 2. During the movement of closing the
forming tool, the slide 9 assumes a position of use
upon contact with the blank 8. The hollow profiled
element blank 8 which has hitherto remained unformed is
pressed together by the pressing surface 21, acting on
it, of the slide 9, with the result that the blank
assumes a preprofiled intermediate form 22 which has a
rough contour approximating to the contour of the about
rectangular forming space 7. In the final phase of the
movement of closing the upper die 3, the impression 5
of the latter acts upon an upper region of the hollow
profiled element blank 8 and presses this upper region
inward until the forming space 7 is closed completely.
In the closed position of the forming tool 2, the
pressing surface 21 of the slide 9 forms the impression
which delimits the forming space 7 laterally. This may,
depending on the design of the slide 9, be a local
boundary or a boundary which is extended virtually over
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the entire longitudinal extent of the hollow profiled
element blank 8. In the closed position of the forming
tool 2, the underside 10 of the upper die 3 lies on the
top side 23 of the slide 9. At the same time, the slide
9 is held outwardly, on its rear side 16, by the flank
of the clearance 14 of the upper die 3. The flank 15
of the upper die 3 in this case engages behind the rear
side 16 of the slide 9 and bears against the sliding
plate 18 of the slide 9. The rear support of the slide
10 9 by that region of the upper die 3 which engages
behind said slide and is designed as a flank 15 is,
however, necessary in that, during the subsequent
internal high-pressure forming of the intermediate form
22 of the hollow profiled element, the slide 9 is not
15 driven outward and therefore the forming space 7 is not
opened laterally, the result of which would be that the
hollow profiled element blank 8 would expand laterally
outward out of the forming space 7 in an undesirable
way.
A fluidic internal high pressure is then generated
within the intermediate form 22 of the hollow profiled
element blank 8 via the fluid high-pressure generation
system, after which the intermediate form 22 is formed
by expansion into the final form of the hollow profiled
element. In this case, those regions 24 of the blank 8
which were still just spaced apart from the blank 8 in
the intermediate form 22 of the latter also come to
bear against the impressions 5, 6 and 21. Moreover, it
is also conceivable that the hollow profiled element
blank 8 is filled with pressure fluid even before the
pressing operation by the slide 9, thus leading, during
the pressing operation, to an internal support of the
blank 8. This internal support additionally counteracts
a creasing of the hollow profiled element blank 8
during the pressing operation and thus also contributes
to the high degree of process reliability of the
forming operation and therefore to the desired
formation of the hollow profiled element.
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After the forming of the hollow profiled element blank
8 into the desired final form of the hollow profiled
element has taken place, the pressure fluid within the
hollow profiled element is depressurized and the
forming tool 2 is opened. In this case, the upper die 3
is moved away from the lower die 4, the flank 15
sliding along, free of jamming, on the sliding plate 18
of the slide 9. At the same time, as a result of the
wedging action which the tension column 12 exerts on
the slide 9, the latter is moved into a position of
non-use outwardly away from the forming space 7 and
transversely with respect to the direction of movement
of the upper die 3. After the opening of the forming
tool 2, the ready-formed hollow profiled element can
then be extracted from the tool 2.
