Note: Descriptions are shown in the official language in which they were submitted.
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DaimlerChrysler AG
Device for internal high pressure formi
The present invention relates to a device for internal
high pressure forming according to the preamble of
claim 1.
A method and a device for the internal high pressure
forming of a hollow profile closed at the periphery has
been disclosed by the German Patent Application still
not published at the time of the present application
and having the official reference 103 49 699.8 dated
October 24, 2003. The known device has an internal high
pressure forming tool with a sealing arrangement which
contains an axial punch having a section plunging into
the hollow profile for holding and sealing an end of
the hollow profile, this end projecting from the
impression of the forming tool. Furthermore, a unit for
generating a high fluid pressure is provided for
expanding the hollow profile by means of fluidic
internal high pressure. Owing to the fact that an
outside diameter of the axial punch on the plunging
section is equal to or falls slightly below the inside
diameter of the hollow profile end, and owing to the
fact that the sealing arrangement contains at least one
clamping jaw and a pressing element which, when the
section of the axial punch has plunged in, presses
radially on the hollow profile end, said clamping jaw
fixes the hollow profile end in position. These
measures prevent the hollow profile blank from being
able to be pulled off the axial punch during the
internal high pressure forming process and thus prevent
its sealing effect from being reduced or even
completely neutralized. Since the hollow profile blank,
on account of the firm, axially immovable hold at the
end, cannot be drawn into the impression during the
forming, firstly the original overall length of the
hollow profile blank is unaffected by the forming and
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secondly no material of the hollow profile end can
subsequently flow from the end into the mold space, so
that, in particular in the case of long forming
sections, a largely uniform distribution of the wall
thickness can be achieved at each point of the hollow
profile blank.
EP 1 152 843 B1 discloses a device for the internal
high pressure forming of a hollow profile as defined in
the preamble, which device has a forming tool, a
sealing arrangement for holding and sealing an end of
the hollow profile, this end projecting from the
impression of the forming tool. The sealing arrangement
is formed by a section of an axial punch, this section
plunging into the hollow profile, and by at least one
clamping jaw which, when the section of the axial punch
has plunged in, presses radially from outside on the
hollow profile end in such a way that the clamping jaw
fixes the latter in position. The clamping jaw is
connected to an actuator which drives it for displacing
it only radially to the hollow profile axis.
DE 197 51 407 C1 discloses a device for hydraulically
sealing a hollow profile. The device has a die and a
clamping and feed unit and also a plurality of sealing
elements closing the hollow profile. In the region of
the sealing location, the die consisting of two die
halves has, on the inside, a respective rounded bulged
section extending radially inward over the periphery,
the clamping and feed unit being provided with an
axially movable mandrel which can be pushed into the
hollow profile by means of a push-pull element. This
mandrel is positioned with respect to the die in such a
way that the bulged sections of the die lie such that
they correspond to a mandrel section of corresponding
design. Since the distance from the tube end is
therefore not limited, sealing at any desired location
in the tool is possible.
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DE 38 20 952 C2 discloses a device for hydraulically
expanding metallic hollow profiles generally open at
end faces. The open end faces in this case are closed
by rigid sealing heads which surround the inner or
outer surface of the hollow profile in a close-fitting
manner but at a slight distance apart. A sealing gap in
between is sealed off in an elastic sealing ring which
is designed as a hollow body and to which internal
pressure can be applied. In addition, the sealing ring
is enclosed in the sealing head in such a way that, as
a result of the internal pressure, it can expand only
in the direction of the outer or inner surface of the
hollow profile to be sealed and comes into tight
contact with the latter. The result of the enclosing of
the sealing ring is therefore that the elastic material
cannot give way laterally. Since, furthermore, the
hydraulic expansion pressure is also applied in the
sealing gap, provision is made for the internal
pressure in the sealing ring to always be kept so far
above this expansion pressure that the contact pressure
of the sealing ring on the surface of the hollow
profile is always above the expansion pressure and thus
reliable sealing is ensured.
DE 197 33 473 A1 discloses a method and a device for
connecting a hollow-cylindrical air/fuel-ratio detector
holder to an exhaust pipe provided with an opening for
admitting exhaust gas to the air/fuel-ratio detector
fastened in the holder. In this case, the method uses
the internal high pressure technique for connecting the
air/fuel-ratio detector holder.
In this case, by means of internal high pressure, the
contour of the exhaust pipe is adapted in a simple
manner to the bearing contour of the lateral surface of
the holder at the location at which the future bearing
surface of the holder is provided. The connection of
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the lateral surface of the holder to the exhaust pipe
saves construction space, the holder, at this location,
being virtually sunk into the exhaust pipe, but at
least into the pipe wall.
The present invention deals with the problem of
specifying an improved embodiment for a device for
internal high pressure forming of the type mentioned at
the beginning, which embodiment ensures in particular
reliable holding and sealing of the semi-finished ends
of the hollow profile and at the same time enables
high-quality components formed by internal high
pressure to be produced.
This problem is solved according to the invention by
the subject matter of independent claim 1. Advantageous
embodiments are the subject matter of the dependent
claims.
The invention is based on the general idea, in a device
for the internal high pressure forming of a hollow
profile, which device has a sealing arrangement for
holding and sealing an end of the hollow profile, this
end projecting from an impression of the forming tool,
of providing an actuator which drives a clamping jaw
for displacing it only radially to the hollow profile
axis and thus presses the clamping jaw from outside
onto the hollow profile end in such a way that the
latter is fixed in position. In this way, improved
sealing and holding of the hollow profile end can be
achieved. Counteracting the pressure force in the
process is a section of an axial punch, this section
plunging into the hollow profile and being part of the
sealing arrangement and supporting the hollow profile
end from inside against the clamping jaw pressing from
outside.
The actuator results in the hollow profile end already
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being clamped and thus held and sealed before the
actual forming operation, so that the hollow profile
blank can be moved into the forming tool when the
latter is open and as a result any damage to a surface
of the hollow profile blank can be avoided or at least
reduced. At the same time, the hollow profile blank can
be reliably held during the entire production process
by being pressed against the axial punch by means of
the clamping jaw acting radially from outside. As a
result, this prevents a situation in which the hollow
profile blank can be pulled off the axial punch during
the internal high pressure forming process and thus its
sealing effect is reduced or even neutralized.
Since the hollow profile blank cannot be drawn into the
impression or cavity block, firstly the original
overall length of the hollow profile blank remains
unaffected by the forming and secondly no material of
the hollow profile blank can subsequently flow from the
end into the mold space, so that, in particular in the
case of long forming sections, a largely uniform
distribution of the wall thickness prevails at each
point of the hollow profile blank.
The largely uniform distribution of the wall thickness
also ensures production of a component coil without any
problems, from which, after forming has been effected,
a plurality of individual components of identical
configuration are produced in a subsequent parting
process, these individual components having identical
or at least similar functional properties on account of
the uniform distribution of the wall thickness.
Since, due to the device according to the invention,
the hollow profile end is not changed in its shape by
expansion, and at least the inside diameter is also
retained, subsequent end trimming may be dispensed
with, which saves production time and reduces the costs
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for the entire production process.
According to the solution according to the invention,
at least one V-ring is arranged on a side of the
clamping jaw facing the hollow profile end. Due to the
interlocking thereby achieved, not only is the hollow
profile end held more intensely between the clamping
jaw and the axial punch, but the axial material flow
within the hollow profile end is interrupted, which
prevents creeping of the hollow profile at its end in
the direction of the forming tool impression. The
result of this is that lower pressure forces have to be
applied in order to sufficiently counter the drawing-in
which is caused during the internal high pressure
forming.
According to a preferred configuration of the
invention, the actuator comprises at least one
hydraulic cylinder or is formed by at least one
hydraulic cylinder. As a result, the clamping jaw can
be pressed onto the hollow profile end hydraulically
and thus in a powerful and precise manner. At the same
time, hydraulic cylinders constitute a drive technology
which has proved successful for many years and is thus
reliable, so that the actuator can be realized in a
cost-effective manner with regard to operation and
maintenance.
According to an advantageous embodiment of the
invention, the actuator enables the clamping jaw to be
displaced when the forming tool is open. The forming
tool may be formed, for example, from at least two die
parts which are displaceable relative to one another
and form the impression in the closed state. Due to the
displaceability of the clamping jaw when the forming
tool is open, it is possible to move the hollow profile
blank into the forming tool without there being a risk
of damage to the surface of the hollow profile blank in
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the process, since the two die parts lie well outside
the path of movement of the hollow profile blank.
Especially high quality requirements can be fulfilled
by surface damage being avoided or reduced.
The die parts can expediently be displaced while the
clamping jaw fixes the hollow profile end. This results
in a method advantage, since the die parts must first
be displaced onto the hollow profile blank directly
before the internal high pressure forming and thus
premature damage to the surface of the hollow profile
blank caused by a bearing surface of the cavity block
can be avoided. At the same time, this prevents the end
of the hollow profile blank from being drawn in as a
result of preprofiling for the case where the hollow
profile blank, from the closing movement of the forming
tool, is to be compressed and thus preprofiled.
Further important features and advantages of the
invention follow from the subclaims, from the drawings
and from associated description of the figures with
respect to the drawings.
It goes without saying that the abovementioned features
and the features still to be explained below can be
used not only in the respectively specified combination
but also in other combinations or on their own without
departing from the scope of the present invention.
Preferred exemplary embodiments of the invention are
shown in the drawings and are described in more detail
below, the same designations designating identical or
functionally identical or similar components.
In the drawing:
fig. 1 shows one part of a device for internal high
pressure forming in an initial position,
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fig. 2 shows an illustration as in fig. 1 but with an
axial punch placed against one end of a hollow
profile,
fig. 3 shows an illustration as in fig. 2 but with a
clamping jaw pressed onto the end of the hollow
profile from outside,
fig. 4 shows an illustration as in fig. 3 but with
closed forming tool.
According to fig. 1, a device 10 for the internal high
pressure forming of a hollow profile 5 has a cavity
block 1, and adjustably mounted clamping jaw 3 arranged
thereon, and an axial punch 4. In this case, the cavity
block 1 is part of a forming tool (not explained in any
more detail) in which the hollow profile 5 is expanded
by internal high pressure and is formed in accordance
with an impression 16. The clamping jaw 3 and the axial
punch 4 are part of a sealing arrangement 11 which
serves to hold and seal an end 12 of the hollow profile
5, this end 12 projecting from the impression 16 or
cavity block 1 of the forming tool. At an end facing
the hollow profile end 12, the axial punch 4 has a
plunging section 6 (sealing region), with which the
axial punch 4 plunges into the hollow profile 5.
In general, according to figs 1 to 4, in each case only
one part of the device, for example a top part in figs
1 and 3 and a bottom part in figs 2 and 4, is shown.
The axial punch 4 widens from its plunging section 6 to
the rest of the punch body in a stepped manner while
forming a shoulder (not designated in any more detail),
by means of which the axial punch 4 strikes the hollow
profile end 12 while assuming the position of use. The
plunging section 6 of the axial punch 4 is in this case
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dimensioned in such a way that it comes to lie in the
position of use (cf. figs 2 to 4) on a certain
extension length in the forming tool. Due to the
mounting thus achieved, the axial punch 4 remains
oriented in a centered manner, which helps to achieve a
lasting sealing function.
Running in the axial punch 4 is at least one axial
action-medium passage 7, which on the one hand is
connected to a unit for generating high fluid pressure
and on the other hand opens out at an end face 13 of
the axial punch 4. An outside diameter of the axial
punch 4 on the plunging section 6 is favorably
dimensioned in such a way that it corresponds to the
inside diameter of the hollow profile end 12 or falls
slightly below the latter, so that the section 6 comes
to lie in the hollow profile end 12 free of play, but
without plastic expansion of the hollow profile end 12,
or with slight play.
According to fig. 1, the sealing arrangement 11 has at
least one clamping j aw 3 , which is an integral part of
the forming tool and which is mounted on the outer side
of the forming tool in such a way as to be displaceable
radially to the hollow profile axis. At least one V-
ring 2 is provided on an end face, facing the hollow
profile end 12, of the clamping jaw 3, and this V-ring
2, when the clamping jaw 3 presses on the hollow
profile end 12 resting in place on the plunging section
6, notches and fixes said hollow profile end 12. The
notch produced by the V-ring 2 can be advantageously
used, for example, during further use of the hollow
profile 5 in an operation for joining it to other
components.
According to the invention, an actuator 14 is provided
for actuating the clamping jaw 3 (cf. figs 3 and 4) and
drives the latter for displacing it only radially
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relative to the hollow profile axis . In this case, the
actuator 14 may be formed by at least one hydraulic
cylinder or may comprise at least one hydraulic
cylinder. Alternatively, it is also conceivable for the
actuator 14 to be formed by at least one electric motor
or to comprise at least one electric motor.
In general, the device 2 has at least two die parts 15
adjustable relative to one another, for example a top
die part 15' and a bottom die part 15" , which can be
displaced toward and away from one another
independently of the clamping jaw 3. According to figs
1 to 3, it is shown that the actuator 14 enables the
clamping jaw 3 to be displaced when the forming tool is
open.
In order to enable the clamping jaw 3 to be displaced
independently of the die part 15, the clamping jaw 3,
according to fig. 3, can be supported for example on
the forming tool, that is to say on the die part 15',
whereas the die part 15' is supported on a foundation
9.
However, it is also conceivable, according to fig. 4,
for both the clamping jaw 3 and the die part 15' of the
forming tool to be supported independently of one
another on the foundation 9.
In principle, it is conceivable for the clamping jaws 3
to be carried along axially. This ensures controllable
subsequent feeding of material during the forming
process, as a result of which the quality of the hollow
profile 5 produced can be increased. In the process,
the clamping jaws 3 may either be carried along
passively or via a, for example power-controlled,
actuator (not shown), which permits a displacement of
the clamping jaws 3 with respect to the die parts 15
axially relative to the hollow profile 5.
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The method sequence during the clamping or internal
high pressure forming process is to be explained
briefly below:
At the start of the method, the hollow profile 5 is
inserted into the bottom die 15" of the forming tool,
whereupon the section 6 of the axial punch 4, according
to fig. 1, is pushed in the direction of movement 8
into both ends, here into the end 12 of the hollow
profile 5, until its shoulder strikes the hollow
profile end 12. Alternatively, it is conceivable for
the plunging section 6 to be pushed into the hollow
profile 5 beforehand and for the latter to then be
displaced between the two die parts 15' and 15" .
After that, in a second method step according to fig.
2, the clamping jaw 3 is pressed radially from outside
onto the hollow profile end 12 by means of the actuator
14 and thus fixes the latter in position on the
plunging section 6 of the axial punch 4. Due to the
movement of the clamping jaw 3 in the direction of
movement 8' toward the hollow profile end 12, the
latter is notched by the V-ring 2 due to the pressure
force exerted by the actuator 14. In general, it is
conceivable for the actuator 14 for displacing the die
parts 15' and 15" or the clamping jaws 3 to be
designed as a hydraulic or electromechanical actuator.
The embodiment of the V-ring 2 shown according to figs
1 to 4 represents only one possible variant, clamping
jaws 3 without V-rings 2 also being conceivable. In
this case, the clamping jaw 3 is connected fractionally
to the hollow profile end 12, with an interference fit
being formed, and is thus sealed.
According to fig. 3, the clamping operation and thus
the sealing operation by the clamping jaw 3 being
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pressed radially onto the hollow profile end 12 has
been completed and the hollow profile 5 is fixed in
position in the device 10. The die part 15' is now
displaced toward the hollow profile 5 in the direction
of movement 8' ' by the actuator 14' . It is conceivable
here for either only the top die part 15' or else the
top and the bottom die part 15', 15 " to perform a
closing movement. The two die parts 15' and 15 " are
displaced toward one another until the two die parts
15' , 15' ' outside the impression 16 come to lie on the
hollow profile 5. In the process, the die parts 15' and
15" are displaced, while the clamping jaw 3 fixes the
hollow profile end 12. The clamping effect of the
clamping jaws 3 prevents the hollow profile end 12 from
being drawn into the impression 16 by the top die part
15' during the closing movement.
According to fig. 4, the closing operation of the
forming tool has now been completed, so that the hollow
profile 5, by means of the unit for generating high
fluid pressure, can be filled with a pressure fluid via
the at least one action-medium passage 7. After that,
the pressure fluid is put under an internal high
pressure, as a result of which the hollow profile 5
expands and comes into contact with the inner wall of
the impression 16 in such a way as to conform to the
contour. During the expansion, the clamping jaws 3
prevent the hollow profile end 12 from being drawn into
the impression 16 and at the same time seal the hollow
profile end 12. After the internal high pressure
forming has been effected, first the die parts 15' and
15 " and then the clamping jaws 3 are retracted or
opened, so that the finish-formed hollow profile 5 can
be removed by withdrawal of the axial punch 4.
