U.S. patent application number 12/252016 was filed with the patent office on 2010-01-07 for method and device for forming an essentially flat metal blank to produce a thin-walled, shell-type body, and the use of same.
This patent application is currently assigned to MT AEROSPACE AG. Invention is credited to Johannes HEGELS, Helmut MICHEL, Wulf RADTKE.
Application Number | 20100000279 12/252016 |
Document ID | / |
Family ID | 36950046 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100000279 |
Kind Code |
A1 |
MICHEL; Helmut ; et
al. |
January 7, 2010 |
METHOD AND DEVICE FOR FORMING AN ESSENTIALLY FLAT METAL BLANK TO
PRODUCE A THIN-WALLED, SHELL-TYPE BODY, AND THE USE OF SAME
Abstract
The invention relates to a vacuum-assisted method and a device
for forming an essentially flat blank (12) of metal into a
thin-walled, shell-type body (14), especially for performing the
method in accordance with one of the preceding claims, that has a
supporting structure (16) forming a mold chamber (18) that holds
the blank (12) during increasing deformation into the thin-walled,
shell-body (14), a device (20) allocated to the supporting
structure (16) for clamping the blank (12) about its circumference
(22) to the supporting structure (16), that seals the reverse face
(24) of the blank (12) facing towards the mold chamber (18) against
the front face (26) of the blank (12) facing away from the mold
chamber (18), and a device (28) allocated to the mold chamber (18)
that also communicates with the mold chamber (18) for applying a
vacuum and evacuating the mold chamber (18), and at least one
forming tool (50) applied to the front face (26) of the blank (12)
is/are allocated to the supporting structure (16), and the use of
same.
Inventors: |
MICHEL; Helmut; (Esslingen,
DE) ; RADTKE; Wulf; (Planegg, DE) ; HEGELS;
Johannes; (Muenchen, DE) |
Correspondence
Address: |
ROTHWELL, FIGG, ERNST & MANBECK, P.C.
1425 K STREET, N.W., SUITE 800
WASHINGTON
DC
20005
US
|
Assignee: |
MT AEROSPACE AG
Augsburg
DE
|
Family ID: |
36950046 |
Appl. No.: |
12/252016 |
Filed: |
October 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11437814 |
May 22, 2006 |
7454936 |
|
|
12252016 |
|
|
|
|
Current U.S.
Class: |
72/38 ;
72/84 |
Current CPC
Class: |
B21D 22/185
20130101 |
Class at
Publication: |
72/38 ;
72/84 |
International
Class: |
B21D 22/16 20060101
B21D022/16; B21D 26/00 20060101 B21D026/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2005 |
DE |
10 2005 024 627.3 |
Claims
1. Method for forming an essentially flat blank (12) of metal into
a thin-walled, shell-type body (14), with the blank (12) being
clamped over its circumference (22) to a supporting structure (16)
with a mold chamber (18) in which the blank (12) is held during
increasing deformation into a thin-walled, shell-type body (14),
the rear face (24) of the blank (12) facing towards the mold
chamber (18) being sealed with respect to the front face (26) of
the blank (12) facing away from the mold chamber (18), a vacuum
being applied to the mold chamber (18) forming the closure of the
blank (12) and the blank (12) being deformed into a thin-walled,
shell-type body (14) by a defined evacuation of the mold chamber
(18) and by at least one forming tool (50) applied to the front
face (26) of the blank (12), with the blank (12) and the at least
one forming tool (50) being moved, especially rotated, relative to
each other.
2. Method in accordance with claim 1, characterized in that the
blank (12) is brought to an elevated temperature profile by at
least one device (30) for warming and/or heating the blank (12)
allocated to the mold chamber (18).
3. Method in accordance with claim 1, characterized in that the
blank (12) is held at an elevated temperature profile by at least
one device (32) for thermal insulation allocated to the mold
chamber (18) and/or at least one device (34) allocated to the mold
chamber (18) for heat reflection.
4. Method in accordance with claim 1, characterized in that the
blank (12) is supplied with protective gas by a device allocated to
the mold chamber (18) or communicating with the mold chamber
(18).
5. Method in accordance with claim 1, characterized in that the
blank (12) is deformed into the thin-walled, shell-type body (14)
by a perforated mating mold (48) allocated to the mold chamber
(18).
6. Method in accordance with claim 1, characterized in that the
blank (12) is deformed into the thin-walled, shell-type body (14)
by at least one forming or pressure roller and/or one, preferably
hydrostatically mounted, pressure ball.
7. Method in accordance with claim 6, characterized in that the
front face (26) of the forming tool (50) applied to the blank (12)
is guided relative to the blank (12) from the circumference (22) to
the centre of the blank (12) and/or from the centre to the
circumference (22) of the blank (12).
8. Method in accordance with claim 6, characterized in that the
forming tool (50) applied to the front face (26) of the blank (12)
is controlled by means of a template or numerically using
closed-loop and/or open-loop control.
9. Method in accordance with claim 1, characterized in that the
blank (12) before deforming into the thin-walled, shell-type body
(14) is formed from at least two separate flat elements joined
together to form one unit by means of tungsten inert gas (TIG)
welding, metal inert gas (MIG) welding, friction stir welding
(FSW), electron beam (EB) welding, laser welding, plasma welding or
a similar welding method.
10. Method in accordance with claim 1, characterized in that the
blank (12) is soft annealed before deforming into the thin-walled,
shell-type body (14).
11. Method in accordance with claim 1, characterized in that the
blank (12) is pre-contoured by chip removal, especially by turning,
milling and/or grinding, before deforming into the thin-walled,
shell-type body (14), with a predetermined wall thickness
distribution of the blank (12) being set to obtain the required
final wall thickness of the thin-walled, shell-type body (14).
12. Method in accordance with claim 11, characterized in that the
blank (12) is provided with contouring on its reverse face (24)
before deforming into the thin-walled, shell-type body (14).
13. Method in accordance with claim 1, characterized in that the
blank (12), before deforming and/or stretching into the
thin-walled, shell-type body (14), is provided, by chip removal,
especially by turning, milling and/or grinding, with openings,
perforations or similar cutouts, especially in the pole area of the
blank (12) that are temporarily sealed vacuum tight by covers,
especially a film.
14. Method in accordance with claim 1, characterized in that the
blank (12) is preformed and/or pre-pressed before deforming into
the thin-walled, shell-type body (14).
15. Method in accordance with claim 1, characterized in that the
blank (12), before deforming into the thin-walled, shell-type body
(14), is brought to condition T4 by solution annealing followed by
quenching.
16. Method in accordance with claim 1, characterized in that the
blank (12) is cold formed for deforming into the thin-walled,
shell-type body (14).
17. Method in accordance with claim 1, characterized in that the
blank (12) is hot age-hardened and brought to condition T8 before
deforming into the thin-walled, shell-type body (14).
18. Method in accordance with claim 1, characterized in that the
blank (12) is continuously measured when deforming into the
thin-walled, shell-type body (14).
19. Use of the method and/or device in accordance with claim 1 for
producing components (12) that are rotationally symmetrical and/or
not rotationally symmetrical, are shell-shaped, especially
hemispherical-cap shaped, dome-shaped, elliptical-dome shaped,
elliptical, or Casini-shaped or with other cross-section
shapes.
20. Use of the method and/or device in accordance with claim 1 for
the production of shells as domes for rocket fuel tanks, satellite
tanks, parabolic antennas, parabolic deflector dishes, parabolic
solar collectors, searchlight housings, container bottoms, tower
cupolas, pressure domes or similar.
21. Use of the method and/or the device in accordance with claim 1
for rolling, especially compaction rolling, of defined surfaces of
thin-walled, shell-type bodies (14).
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a division of U.S. application Ser. No.
11/437,814, filed May 22, 2006, which claims the benefit of German
Patent Application No. 10 2005 024 0627.3 filed on May 30,
2005.
DESCRIPTION
[0002] This invention relates to a method and a device for forming
an essentially flat metal blank to produce a thin-walled,
shell-type body, and the use of same.
[0003] Such methods and devices for the production of shell-type
bodies from essentially flat blanks, round blanks or similar sheets
are generally known, but overall have a number of disadvantages
that are to some extent considerable.
[0004] During bottom pressing, a round blank is positioned on a
draw ring and, by means of a punch that has the shape of the
internal contour of the shell-type of body, is pressed from the top
centre through the draw ring gap. In this case, a starting material
is always used that is distinctly thick-walled relative to the
shell diameter. When forming shell shapes with a small wall
thickness-diameter ratio, folds form in the sheet. Bottom pressing
therefore does not enable small thin-walled metal components with
the correct final contour to be produced. To obtain the required
final wall thickness rather requires a reworking by turning or
milling.
[0005] With convex pressing, a round blank, that is held in the
pole or centre of rotation against a rotating, convex-shaped
pressure mold is pressed against the pressure mold by means of a
forming roller and formed into a shell-type body. The forming
always takes place from the centre clamping outwards. By means of
the convex pressing, such as for example is described in GB
1,468,659 or EP 1 285 707 B1, relatively thick starting sheets can
generally also only be formed into shell-type bodies. The minimum
wall thickness required for the forming, in addition to the
diameter of the shell to be produced, depends on the shape of the
cross section of the shell-type body. When forming shell-type
bodies with a small wall thickness-diameter ratio, folds likewise
form in the sheet. To reduce the folding and mechanical reworking,
devices are recommended according to U.S. Pat. No. 3,355,920 that
are designed to enable the mold to be sized.
[0006] With concave mating mold pressing, a preformed round shell,
that is held in the instaneous centre or centre of rotation against
a rotating, concave-shaped pressure mold, is pressed against it by
means of a forming roller and is rotationally-symmetric formed from
the inside. As, for example, can be seen from U.S. Pat. No.
6,006,569, a shell-type body cannot be brought to its final shape
and size in the concave pressure mold. Instead, further steps,
particularly an additional forming on a convex curved pressure
mold, are necessary.
[0007] With shot-blast forming, single, flexibly pre-curved
components are formed into the spherically-curved segments of a
shell-type body by blasting with small balls and then a pole cap is
either welded or riveted to a, mainly large, shell-type body.
Although shot-blast forming, as for example disclosed in DE 38 42
064 C2, has been proven in practice, the necessary wall thickness
reinforcements of weight-optimized shell-type bodies such as the
domes of tanks for aerospace applications in the area of welds
and/or riveted joints has proved an obstacle.
[0008] With counterroller pressing, a rotating round blank clamped
on the edge is formed by an internal roller and a counterroller.
This enables materials that are difficult to form to be formed
essentially using pressure forces. This is produced by the
interaction of the two opposing rollers whereby the rotating
shell-type body is stressed and thus formed. The formability of
materials is improved by applied pressure stresses. With the
counterroller pressing, as for example has been described in EP 0
593 799 B1 and has been proved in practice, the forming takes place
exclusively due to pressure stresses that build up between the
rollers. This means that undesirable material stresses due to
tension are avoided or limited. This results, not least, in certain
restrictions for counterroller pressing because the overall design
of the device, due to the many individual components required owing
to the rollers having to correspond to each other, is very
expensive and cost intensive. Furthermore, the programming expense
for the NC controller is greater because two rollers have to be
controlled.
[0009] Finally, with concave pressing, for example described in EP
0 457 358 B1, U.S. Pat. No. 3,316,745, GB 201,269 and U.S. Pat. No.
6,006,569, a rotating circular blank cut to size, e.g., a preformed
round blank, is secured along its circumference to a ring or
clamping plate, is curved outwards by a roller in a free space
behind the ring plate or clamping plate and formed as necessary
into a rotationally symmetrical, shell-type body with the correct
final contour dimensions. This takes place, depending upon the
necessary curving, mostly in several individual steps, with the
round material being plastically expanded and tensioned in azimuth
in the diaphragm area due to the increase in area. Substantial
manufacturing costs of the shell-type body due to the high heat and
energy costs on one hand and the high manpower, retoolings and thus
time and cost on the other hand have been shown to be a serious
disadvantage, particularly with concave pressing.
[0010] The object of this invention is therefore to provide a
method and a device for forming or deforming an essentially flat
metal blank to produce a thin-walled, shell-type body, by means of
which the above disadvantages can be avoided, that furthermore
enables a much improved economic utilization and, particularly in
view of the greatly increasing requirements of aerospace, provides
low weight and high strength combined with a high degree of
dimensional stability, and use of same.
[0011] With regard to the method, the object is achieved in a
surprisingly simple manner by the features of claim 1.
[0012] By means of the arrangement of the method in accordance with
the invention for forming or deforming an essentially flat blank of
metal into a thin-walled, shell-type body, with the blank being
clamped over its circumference to a supporting structure with a
mold chamber in which the blank is held during increasing
deformation into the thin-walled, shell body, the reverse face of
the blank facing the mold chamber being sealed with respect to the
front face of the blank facing away from the mold chamber, a vacuum
being applied to the mold chamber closed by the blank and the blank
being deformed by a defined evacuation of the mold chamber and by
at least one forming tool applied to the front face of the blank to
form the thin-walled shell body, with the blank and the at least
one forming tool being moved, especially rotated, relative to each
other, a method of manufacture is proposed that due to a
substantially improved utilization of existing heat and force
potentials leads to a high economic efficiency due to the
substantial reduction in energy costs and accompanying time saving.
At the same time, a significantly large shape and dimensional
accuracy of the thin-walled, shell-type body accompanied by weight
saving and an increase in strength and load limits are enabled. The
application of a vacuum and the defined evacuation of the mold
chamber is very significant, with the term "vacuum" in the
following being a technical term including a coarse vacuum and
generally a negative pressure. The forming and/or deforming or
concave pressing with the aid of a negative pressure is thus
substantially accelerated. The negative pressure at the same time
has the effect of holding the blank clamped due to the pressure
difference between the ambient pressure on its front face and the
negative pressure on its reverse face and consequently is drawn or
lightly pressed into the mold chamber in the direction of the
subsequent final geometry into a thin-walled, shell-type body. The
negative pressure, in an advantageous manner, compensates for any
material shifts that occur due to the different stress conditions
within the blank during the deforming or forming or during concave
pressing into a thin-walled, shell-type body. By applying a vacuum
to the mold chamber closed by the blank and by the defined
evacuation of this chamber, further substantial advantages result.
Thus, the clamping forces acting on the blank in the supporting
structure to be deformed or formed or to be pressed are increased.
Thus also, stresses in the blank can be induced that are
proportional to the effective pressure difference between the
ambient pressure acting on the front of the blank and the negative
pressure felt on the reverse of the blank. These stresses
substantially support and accelerate, particularly with regard to
time, the deforming and/or forming or concave pressing. At the same
time, a further problem can be prevented, or at least reduced. Thus
if a forming tool is used, any material wave of the blank driven
before the forming tool is reduced, because the level of such a
wave can be reduced by the influence of the stresses induced in the
blank by the vacuum or negative pressure. Last but not least, the
evacuation of the mold chamber on one hand and the accompanying
accelerating deforming and/or forming or concave pressing of the
blank into a thin-walled, shell-type body on the other generally
reduces the occurrence of oxidation.
[0013] Further advantageous design details of the method in
accordance with the invention are described in claims 2 to 18.
[0014] In an embodiment of the inventive method, the blank in
accordance with claim 2 is warmed and/or heated to an elevated
temperature profile by at least one of the devices allocated to the
mold chamber.
[0015] In an advantageous manner, the blank is furthermore in
accordance with claim 3 held at an elevated temperature profile by
at least one of the devices allocated to the mold chamber for
thermal insulation and/or by at least one of the devices for heat
reflection allocated to the mold chamber. Hot forming depends
principally on maintaining, within narrow tolerances, the
temperature conditions of the blank that have been set or an
elevated temperature profile of the blank that has been reached, so
that the heat energy requirement, particularly also in the case of
thin-walled blanks or shell-type bodies, is kept constant without a
great control effort, and particularly kept small. For this
purpose, heat losses in the blank or subsequent shell-type body in
the mold chamber are reduced in that convection losses can be
largely eliminated by extracting the air through the device for a
defined evacuation of the mold chamber and pipeline or radiation
losses also almost completely eliminated by lining the mold chamber
with heat-insulating material and surrounding the mold chamber with
reflecting (multiscreen) reflector film.
[0016] To avoid, or at least to limit, oxidation to which the blank
is exposed due to the application of heat, according to claim 4 of
the invention protective gas is applied to the blank through a
device arranged in the mold chamber or communicating with the mold
chamber.
[0017] The measures of claim 5 are particularly significant for a
simplified and accelerated production of a thin-walled, shell-type
body from an essentially flat blank. According to this, the blank
is formed into a thin-walled, shell-type body by means of a
perforated mating mold arranged in the mold chamber. The perforated
mating mold also serves to hold and support the blank or subsequent
thin-walled, shell-type body after the mold chamber has been
adequately evacuated.
[0018] With blanks with a greater wall thickness or with a more
complicated meridian geometry it is particularly advantageous that
the method in accordance with the invention for deforming and/or
forming or pressing is supported by the use of vacuum using the
technical features of claim 6. According to this, the blank is
formed into a thin-walled, shell-type body similar or corresponding
to the principal of "concave pressing" by at least one forming tool
applied to the front of the blank. In this case, at least one
forming or pressure roller and/or a pressure ball, that is then
advantageously hydrostatically mounted, is used as the forming
tool. In doing so, the blank and the at least one forming tool are
moved relative to each other, especially rotated.
[0019] In this connection, it has been shown to be particularly
advantageous to influence the dimensional stability of the blank
and subsequent thin-walled, shell-type body during the deforming
and/or forming of concave pressing in accordance with the measures
of claim 7, in that the forming tool applied to the front of the
blank is, in deviation from the previous handling, moved relative
to the blank from the circumference to the middle of the blank
and/or equally from the middle to the circumference of the blank.
By means of such movement, that may be alternating as required, the
disturbing influence due to strong elastic recovery of the blank in
the area of its pole in particular is better controlled and is
reduced early. This method also provides the possibility of
creating particularly flat shapes in the pole area of the blank,
such as are frequently used in aerospace. Furthermore, distinctly
shortened travel paths of the forming tool are achieved by such
guidance and, not least, this results in a clear overall time
saving. In principle, the special movement of the at least one
forming tool can be in the form of a spiral relative to the blank
from inside to outside or vice versa from outside to inside, but
always consisting purely of great circles or kinematic combinations
of same that lead to the required geometry of the thin-walled,
shell-type body. A relative movement between the blank and forming
tool can also take place in steps with a matched application in
each case and in any combinations of the particular basic
movements, in order to generate a required geometry.
[0020] A further increase in the dimensional stability that can be
achieved with the method in accordance with the invention is
achieved by the features of claim 8, whereby the forming tool
applied to the front of the blank is controlled by closed-loop
and/or open-loop control. The final geometry of the thin-walled,
shell-type body can thus be defined by the meridian curve of a
(plate) template or by programming the meridian curve of the
(plate) template into an NC controller. In this way, the feed of
the forming tool is determined and limited parallel to the central
axis of location of the blank relative to the radius and also takes
account of the elastic recovery behavior of the material at the
same time. Subsequent changes or adaptations of the geometry for
other-shaped, shell-type bodies are possible without a
high-expenditure of time, personnel or accompanying costs, with it
being necessary merely to change the template or NC controller for
the forming tool.+
[0021] In a further embodiment of the method in accordance with the
invention, the blank in accordance with claim 9 is, before
deforming into the thin-walled, shell-type body, formed in a quite
advantageous manner from at least two separate flat elements that
are joined together to form one unit by means of tungsten inert gas
(TIG) welding, metal inert gas (MIG) welding, friction stir welding
(FSW), electron beam (EB) welding, laser or plasma welding or any
other suitable method of welding.
[0022] In this connection it is especially significant that the
blank in accordance with claim 10 is soft annealed before deforming
into a thin-walled, shell-type body. The deforming and/or forming
or concave pressing can thus be performed more simply and safely,
the softer and more ductile the material behaves. If the blank to
be deformed and/or formed or pressed consists of an assembly of
several separate surface elements, the soft annealing is
advantageous for the removal of internal stresses and differences
in the deformation strength due to welding.
[0023] Furthermore, the design measures of claim 11 are of
particular interest for obtaining the required final wall thickness
of the thin-walled, shell-type body. Accordingly, before deforming
into the thin-walled, shell-type body, the blank is pre-contoured
by chip removal, particularly by turning, milling and/or grinding,
i.e. provided with a predetermined wall thickness distribution in
the flat condition. Due to the rigid clamping of the blank on the
circumference, the material required for changing the shape or
increasing the area of the blank is to be obtained by ironing out
from the starting thickness. With a predetermined component shape
and material properties technically suitable for forming, this
leads to a typical meridianal wall thickness distribution, with the
wall thickness of the blank at the pole and at the circumference
being maintained due to the process. The final wall thickness of
the thin-walled, shell-type body can be precisely set by
pre-contouring the starting thickness before deforming. If the
blank is welded together from several separate flat elements due to
its proportions or dimensions, the wall thickness distribution can,
moreover, be appropriately chosen in the area of the welds.
[0024] The appropriate provision of a contouring of the rear face
of the blank in accordance with claim 12 has been shown to be
particularly advantageous in practice. This makes sure that the
forming tool comes into contact with the uncontoured, smooth front
face of the blank, provided such a forming tool is really
necessary.
[0025] Equally, the blank can, particularly in its pole area, in
accordance with the features of claim 13, be provided with openings
or similar cutouts by chip removal, particularly by turning,
milling and/or grinding, before deforming and/or stretching into
the thin-walled, shell-type body. With a shell-type body that is
perforated in the pole area before the solution annealing, in order
to guarantee a fast, problem-free coolant draining when quenching
the shell-type body, the stretching can, aided by vacuum if the
openings, perforations or similar cutouts are vacuum-proof sealed
before the stretching, be carried out in the cold condition. Covers
that provide a temporary vacuum-proof sealing are provided for this
purpose. For example, stick-on covers of plastic film are suitable
as such covers. To increase the retention of the covers, the
openings, perforations or similar cutout are preferably small but
proportionally more numerous. In this way, the covers can remain
safely attached and supported on the intermediate webs, even under
large negative pressures.
[0026] The measures in accordance with claims 14 to 17 serve quite
advantageously for the further arrangement of the method in
accordance with the invention. Particularly if the blank is made of
metal, especially from aluminum or a, possibly hardenable, aluminum
alloy such as A1 2219 or A1 2195, an optimum heat treatment is
usually sought in order to achieve material properties with a
condition T8. Starting with a soft-annealed, possibly already
pre-contoured or otherwise preformed blank, the blank is clamped in
accordance with the inventive method and formed by initial
pressing. In this way, depending on the geometry, degrees of local
forming of more than 50% with regard to wall thickness reduction
and of more than 60% with regard to lengthening in the meridian
direction can be realized. The blank, at least the first
semifinished, thin-walled, shell-type body, is unclamped and
subjected to intermediate heat treatment. Such intermediate heat
treatment includes solution annealing and quenching. The blank, at
least the first semifinished, thin-walled, shell-type body, is then
clamped again and finally shaped by uniform stretching. An
additional tool is not necessary. Furthermore, the deforming and/or
forming or concave pressing is defined by the control of the final
vacuum and/or of the forming tool. After stretching, a hot
age-hardening in an oven takes place in order to achieve the T8
condition. The T8 condition is at present the maximum achievable
condition for hardenable aluminum alloys frequently used for rocket
fuel tanks.
[0027] Finally, to further increase the achievable dimensional
stability, it is provided in accordance with the invention that the
blank in accordance with claim 18 is continuously measured when
forming into the thin-walled, shell-type body. Such a geometric
measurement of the blank can, for example, be carried out
automatically, perhaps using a contactless measuring system that
can be swung into place. The vacuum and/or the movement of the
forming tool can be automatically adjusted by a closed-loop and/or
open-loop control system, in order to compensate for deviations
from the required shape of the blank. Dimensional deviations, such
as out-of-round, are compensated for or eliminated in this way. The
dimensional accuracy of the final produced thin-walled, shell-type
body is substantially increased. At the same time rotational
symmetry material properties as well as material properties that
are not rotationally symmetric can be corrected.
[0028] The object is further achieved with regard to the technical
device in a surprisingly simple manner by the features of claim
19.
[0029] By means of the embodiment of the device in accordance with
the invention for forming or deforming an essentially flat blank of
metal into a thin-walled, shell-type body, that includes a
supporting structure forming a mold chamber, that holds the blank
for its increasing deformation in a thin-walled, shell-type body,
includes a device for clamping the blank around its circumference
to the supporting structure that seals the rear face of the blank
facing towards the mold chamber with respect to the front face of
the blank facing away from the mold chamber, and a device allocated
to and communicating with the mold chamber for applying a vacuum
and evacuating the mold chamber, and at least one forming tool
applied to the front face of the blank is/are allocated to the
supporting structure, a structure that is overall particularly
simple whilst at the same time compact and stable is achieved.
Furthermore, with the device in accordance with the invention, the
applied heat and force potentials can be substantially better
utilized compared with prior art. Not least, this results in
overall substantially reduced energy, and thus manufacturing costs
for the particular thin-walled, shell-type body. Of particular
significance are the device for providing a sealing clamping of the
blank on one hand and the device allocated to and communicating
with the mold chamber on the other for applying a vacuum and
evacuating the mold chamber itself. In this way, the deforming
and/or forming or concave pressing of the blank into a thin-walled,
shell-type body can be aided by a negative pressure and
significantly accelerated. The time saving that can be achieved is
substantial. Not least, the device in accordance with the invention
enables a high degree of cost effectiveness to be achieved. At the
same time, the device in accordance with the invention enables a
particularly high degree of dimensional stability to be obtained
for the parts to be formed from the blank into a thin-walled,
shell-type of body. By using a vacuum chamber, it is furthermore
possible to increase the clamping forces acting on the blank and to
reduce the convective heat losses when heat is used. Furthermore,
the negative pressure assists the deforming and/or forming or
concave pressing during the possible use of an additional forming
tool. An area of the material possibly not yet formed is drawn in
the direction of the new mold of the thin-walled, shell-type body
by the negative pressure, with it being possible at the same time
to reduce any wave that forms in front of the forming tool. Any
variations in stress conditions within the blank during its
deforming and/or forming or concave pressing into a thin-walled,
shell-type body are advantageously compensated for by the negative
pressure. In this way, it is possible to enlarge the individual
steps for deforming and/or forming or concave pressing and/or to
increase the degree of forming for individual steps and thus to
reduce the overall number of work steps required. With forming
assisted by vacuum, the drive power required for the forming tool
is reduced where at least one forming tool is used with the other
conditions remaining the same, thus resulting in a reduction in the
production and operating costs. There is also a further aspect of
particular significance, i.e. the oxidation of materials due to the
application of vacuum or evacuation of the mold chamber during
deforming and/or forming or concave pressing can be prevented or at
least reduced. Subsequent cleaning of the surface is
correspondingly reduced. This in turn very substantially reduces
the time required.
[0030] Further advantageous design details of the device in
accordance with the invention are described in claims 20 to 50.
[0031] Accordingly, it is possibly as part of the invention to form
the supporting structure for forming the mold chamber in accordance
with claim 20 essentially as a cup, pot, dish, cone, truncated cone
shape or similar hollow shape.
[0032] The features of claim 21 are of particularly great
significance for a simple, effective and efficient construction.
According to this, the supporting structure of the device in
accordance with the invention has at least one device for
irradiating the mold chamber for warming and/or heating the blank,
that in particular is designed as an electrically operated light
lamp heater, infrared radiation heater, induction heater or
circulation-type heater with a circulating heat carrier, preferably
water, oil, molten salt or sodium. The warming and/or heating of
the blank takes place in this manner by the actual device in
accordance with the invention and not, as is the case with prior
art, from outside, although other external heat sources could be
used. This is very advantageous in that not only is the total
energy requirement of the thin-walled, shell-type body to be
produced effectively minimized but also the time required for
warming and/heating can be reduced. If radiation sources are used,
it is useful if these are distributed over the complete surface in
order to achieve a largely uniform distribution of the temperature
over the blank and subsequent shell-type body. A reduced radiator
temperature and/or an adequate distance between the radiator and
blank itself help(s) to prevent isolated temperature increases, hot
spots, on the shell-type body. Electrically heated resistors or
electrically heated surface radiators filled with a suitable heat
carrier can, for example, be used as radiators. Alternatively, an
induction heater can be used for ferromagnetic materials. Suitable
optimization enables not only the heat requirement but particularly
also the machine utilization time to be reduced.
[0033] The measures of claims 22 to 24 also provide a further
saving in heat and energy, and thus associated costs, combined with
an additional improvement in the efficiency and cost effectiveness
of the device in accordance with the invention. Accordingly, the
supporting structure has at least one device allocated to the mold
chamber for thermal insulation and/or at least one device allocated
to the mold chamber for heat reflection, particularly a reflecting
(multiscreen) reflector film, and/or a device for active cooling
134. This enables the heat and energy applied to the blank, and the
subsequent shell-type body, to be optimized and at the same time
protects the supporting structure of the device in accordance with
the invention against high thermal stresses.
[0034] To prevent, or at least limit, the oxidation of the surface
of the blank, preferably a device for applying protective gas to
the blank is allocated to the supporting structure in accordance
with claim 25, that in particular is arranged in the mold chamber
or communicates with the mold chamber for supply of same.
[0035] To improve the monitoring of the deformation and/or
formation or pressing operation, a device for monitoring the
temperature of the mold chamber and/or the blank at points and/or
over the complete area, is allocated to the supporting structure
and/or the blank in accordance with claim 26, for example in the
form of thermocouples, and, additionally or as an alternative, a
thermal imaging camera. In this way, anomalies can be more quickly
detected and then dealt with before damage can occur to the blank
or shell-type body.
[0036] Advantageously, the device for clamping the blank in
accordance with claim 27 has a pressure ring and clamping ring with
a sealing ring between the pressure ring and clamping ring, by
means of which complete sealing of the rear face of the blank
facing towards the mold chamber with respect to the front face of
the blank facing away from the mold chamber is ensured.
[0037] Furthermore, it is provided in accordance with the invention
that the supporting structure in accordance with claim 28 is fitted
with a device for reducing the radial heat expansion between the
blank and the device for clamping the blank.
[0038] In this connection, the device for clamping the blank in
accordance with claim 29 can be shifted radially and/or
circumferentially with respect to the supporting structure or can
otherwise be flexibly arranged. In any case, part of the
impermissible thermal distortion in the blank or finished
shell-type body in the form of stresses can be accommodated by
elastic recovery. Consequently, relative movements of the blank or
shell-type body during the warming or heating are enabled.
[0039] Furthermore, it is within the scope of the invention that a
perforated mating mold arranged in the mold chamber is allocated to
the supporting structure of the device in accordance with the
invention according to claim 30 that is provided to hold and
support the blank to be formed into the thin-walled, shell-type
body.
[0040] In an alternative or additional embodiment, it is provided
in accordance with the invention corresponding to claim 31 that at
least one forming tool applied to the front face of the blank is
allocated to the supporting structure. This forming tool can
consist of one or more forming or pressure roller(s) and/or
pressure ball(s). Advantageously, such pressure ball(s) is/are
preferably hydrostatically mounted. An advantage of a pressure ball
compared with a pressure roller is its simple construction and
overall handling, and with a pressure ball, the complete structural
expenditure for the articulation of the pressure roller, e.g., a
servodrive for tracking the angle of inclination, etc., is omitted.
In every case, the production time for a shell-type body from an
essentially flat blank by using at least one additional forming
tool is substantially reduced. Particularly where several forming
tools are used simultaneously and synchronously, for example where
there are also two differently set, i.e. offset radially and in
azimuth, forming tools, this can have a considerable influence on
the production time of a shell-type body.
[0041] The at least one forming tool applied to the front face of
the blank is, according to the features of claim 32, template- or
numerically-controlled using open-loop and/or closed-loop
control.
[0042] Furthermore, it is within the framework of the invention
that the at least one forming tool that is applied to the front
face of the blank can be individually set with regard to its
application in accordance with claim 33.
[0043] It has been shown to be completely appropriate that the at
least one forming tool applied to the front face of the blank in
accordance with claim 34 is supported by a traverse that is
allocated to the supporting structure, with the supporting
structure together with the blank and traverse being moveable,
especially rotatable, relative to each other.
[0044] In a case of deforming and/or forming or the concave
pressing of the blank into a thin-walled, shell-type body with the
aid of at least one forming tool, it is particularly advantageous
if the supporting structure and the at least one forming tool can
be rotated relative to each other in accordance with claim 35.
[0045] Of particular interest in this case are the features of
claim 36, according to which the supporting structure together with
the blank clamped to it are designed to be rotatable and the at
least one forming tool can move in two dimensions only along a
fixed meridian.
[0046] In this connection, it is within the framework of the
invention in accordance with claim 37 that the supporting structure
together with the blank can be rotated by a drive device about a
central axis of rotation of the supporting structure, while the at
least one forming tool can be moved two-dimensionally on a
specially fixed meridian curve by means of two servodrive devices.
The at least one forming tool thus does not move on a circle or
spiral tracks but instead only on a spatially-fixed meridian curve.
It is guided in two dimensions by a (plate) template or an NC
controller. A spatial spiral movement relative to the blank results
from the superimposition of the rotation of the supporting
structure together with the blank and the movement of the forming
tool.
[0047] In an alternative embodiment of the invention in accordance
with claim 38, the supporting structure together with the blank can
be of fixed construction and the at least one forming tool can be
designed to rotate. Such an embodiment of the device in accordance
with the invention is advantageous if the blank, or subsequent
thin-walled, shell-type body, has large dimensions, particularly a
large diameter.
[0048] According to the measures of claim 39, the at least one
forming tool in this case is appropriately arranged in a traverse
that extends diametrically over the supporting structure together
with the blank and is guided in a rail arrangement or similar, can
be rotated about a central axis of rotation by the drive device of
the traverse and can be moved on a meridian curve relative to the
traverse by means of two servodrive devices. In this way, the
usually heavy supporting structure together with the blank is not
rotated about a central axis of rotation by means of a drive
device, but instead the traverse with the at least one forming tool
complete with a roller guide is rotated. The roller guide and the
necessary servodrive devices are arranged on the traverse that
extends diametrically over the traverse with a clearance from the
blank. The traverse is guided on both sides by a rail arrangement,
for example in rails or similar, and circles over the blank during
deforming and/or forming or concave pressing with at least one
forming tool. To avoid the traverse lifting out of the rail
arrangement, a special prism guide is provided. The forming tool
again moves relative to the traverse on a meridian curve, i.e. in
two dimensions. Accordingly, there are two templates or
NC-controlled servodrive devices in each case for each forming tool
for the vertical or radial movement or deflection. For reasons of
stability, the traverse can also have a sufficiently wide
supporting surface, if necessary using two transverse supports or
similar, in order, for example, to cope with emergency stops at
high rotational speeds without the large transverse forces acting
on the rail arrangement of the traverse.
[0049] In a useful manner, the central axis of rotation of the
supporting structure or of the traverse in accordance with claim 40
is arranged horizontally or vertically. The choice depends mainly
on the design conditions, such as for example the drives, etc.,
that can be used. The larger the dimensions of the blank and
shell-type body, the more devices with a vertical axis of rotation
are preferred.
[0050] Of particularly great importance for an unhindered clamping
of the blank in the device in accordance with the invention or the
unclamping of the shell-type body from the device in accordance
with the invention are the design measures of claims 41 to 46. In
this way, free access to the supporting structure of the device in
accordance with the invention is guaranteed in each case.
[0051] Accordingly, the traverse for replacing a blank with a
thin-walled, shell-type body and vice versa, can in accordance with
claim 41 be detached from the circulating supports or a circulating
rail ring or rails or similar and lifted off by means of a hoist,
for example in the form of a works crane, in order for it to be
able to be placed to the side of the device in accordance with the
invention for the next loading or unloading.
[0052] As an alternative to this, it can also be provided in
accordance with the invention for the traverse for replacing a
blank by a thin-walled, shell-type body and vice versa, to be
designed in accordance with claim 42 so that it can be moved by
means of rail switches on two straight parallel rails, that are
tangentially connected to a rail ring. In this way, it is possible
for loading and subsequent unloading to bring the traverse to a
temporary parked position next to the device in accordance with the
invention.
[0053] Furthermore, it is possible for replacing a blank by a
thin-walled, shell-type body and vice versa, for the traverse to be
designed to be hydraulically lowered and moved sideways in
accordance with claim 43. The device in accordance with the
invention can again be temporarily brought to a side parked
position for loading and unloading.
[0054] In a further alternative proposal for replacing a blank by a
thin-walled, shell-type body and vice versa, the traverse in
accordance with claim 44 can be moved out of, or into, an opening
in the rail supporting structure underneath a rail or similar
supporting carrier ring. The carrier ring for the rails or similar
is therefore located above the device for clamping the blank, so
that the supporting structure can be moved in and out through the
opening in the rail supporting structure. The traverse thus remains
stationery in the rails or similar. The replacement of the blank or
shell-type body takes place outside the rail supporting structure.
For deforming and/or forming or concave pressing, the supporting
structure complete with the blank is moved back to the centre of
the rail supporting structure, centrally aligned and locked and
connected to the vacuum connection and to other supply connections
for electric power and electric signals.
[0055] In accordance with a further embodiment in accordance with
the invention, the traverse in accordance with claim 45 is moved
linearly backwards and forwards on two straight parallel rails or
similar above the fixed supporting structure and carries the at
least one forming tool so that it can be moved backwards and
forwards along the traverse in such as way that the at least one
forming tool can be applied to the blank in circles or spiral
tracks with a constant angle of inclination and at defined height
positions. The traverse can thus be moved linearly backwards and
forwards along two straight rails or similar parallel to each other
above the supporting structure in a standard gantry design. The at
least one forming tool is arranged on the traverse and moved in a
lengthwise direction to the traverse in such a way that the forming
tool describes a circle on the blank or the thin-walled, shell-type
body being formed, the plane of which extends vertically relative
to the central axis of rotation. The servodrive device required for
this must operate synchronously with the drive device of the
traverse, in order to be able to perform the particular sign or
cosign curves precisely. Further servodrive devices are provided
for setting the height position or the pressure depth and for the
inclination or articulation of the forming tool relative to the
central axis of rotation.
[0056] Equally, a kinematic reversal of same is conceivable whereby
the supporting structure in accordance with claim 46 is moved
linearly backwards and forwards on two straight parallel rails or
similar under the fixed supporting structure and the traverse
carries the at least one forming tool that can be moved backwards
and forwards lengthwise along the traverse in such a way that the
at least one forming tool is applied to the blank in circles or
spiral tracks with a constant angle of inclination and in defined
height positions. The supporting structure therefore forms a
backwards and forwards movement in a linear slide guide, while the
gantry-shaped traverse is fixed.
[0057] Furthermore, the device in accordance with the invention is
characterized by the features of claim 47. According to this, the
supporting structure includes a thermally insulated cover or
similar covering plate especially provided with heating surfaces,
for covering the face of the blank facing away from the mold
chamber. By means of the covering element or similar cover plate
132, the usually cold, blank to be deformed can be kept covered
until its temperature reaches the working temperature due to the
application of heat. In particular when bringing the device in
accordance with the invention up to working temperature, the
substantial heat losses of the blank and associated overall machine
occupancy time can be reduced. The cover or similar covering plate
132 makes it easy to vary the heating but also ensures a reduction
in the heat losses and oxidation.
[0058] An additional advantage are the measures of claim 48,
whereby the supporting structure is provided with at least one
safety device 136 allocated to the mold chamber to protect against
external influences by gaseous and/or liquid coolants, in
particular inert gas, preferably argon, nitrogen or water. To
quench the blank or thin-walled, shell-type body, inert gas, e.g.:
argon or nitrogen, but also water, is used as a coolant. To protect
against possible damaging effects of the coolant, the supporting
structure and in particular its other components such as devices
for warming and/or heating the blank, devices for thermal
insulation, devices for heat reflection, the vacuum connection or
supply connections for electrical power and electrical signals are
installed in such a way that they are safely protected. In this
way, it is possible to leave the blank in the device in accordance
with invention for further machining. Additional manpower, time and
cost-intensive retooling can thus be spared.
[0059] In accordance with the features of claim 49, the supporting
structure in this connection preferably has at least one device for
cooling 134, particularly quenching, the blank and/or the
thin-walled, shell-type body via the reverse face facing towards
the mold chamber and/or the front face facing away from the mold
chamber of the blank or thin-walled, shell-type body, and also
including all the necessary supply and return lines for the coolant
itself. It is thus possible to quench the shell-type body from both
faces, i.e. from its reverse and/or front face.
[0060] The device for applying a vacuum and evacuating the mold
chamber in accordance with claim 50 appropriately includes a vacuum
connection that extends into and through the axis of rotation of
the supporting structure and/or communicates with the mold
chamber.
[0061] Finally, it is also part of the invention that the method in
accordance with the invention and/or the device in accordance with
the invention corresponding to claim 51 is/are used to produce
shell-shaped components that are rotationally symmetrical and/or
that are not rotationally symmetrical. Hemispherical,
spherical-flat shaped, dome-shaped, ellipsoidal-dome shaped,
conical or elliptical components or components that are
Casini-shaped or with other cross-section shapes have been shown to
be particularly advantageous for this purpose.
[0062] The method in accordance with the invention and/or the
device in accordance with the invention corresponding to claim 52
is/are quite particularly suitable for the production of shells as
domes for rocket fuel tanks, satellite tanks, parabolic antennas,
parabolic reflector dishes, parabolic solar collectors, searchlight
housings, tank ends, tower cupolas, pressure domes or similar.
[0063] Furthermore, it has been shown to be very advantageous in
practice to use the method in accordance with the invention or the
device in accordance with the invention corresponding to claim 53
for rolling, particularly compaction rolling, of defined surfaces
of the thin-walled, shell-type body. This enables material
properties such as density, hardness, surface appearance, etc., to
be improved at the same time.
[0064] Further features, advantages and details of the invention
are given in the following description of preferred forms of
embodiment of the invention and with the aid of drawings. The
drawings are as follows:
[0065] FIG. 1 A first form of embodiment of a device in accordance
with the invention for deforming an essentially flat blank into a
thin-walled, shell-type body.
[0066] FIG. 2 A further form of embodiment of a device in
accordance with invention for deforming an essentially flat blank
into a thin-walled, shell-type body.
[0067] FIG. 3 Another form of embodiment of a device in accordance
with the invention for deforming an essentially flat blank into a
thin-walled, shell-type body.
[0068] FIG. 4 A schematic plan view of a further form of embodiment
of a device in accordance with the invention for deforming an
essentially flat blank into a thin-walled, shell-type body.
[0069] FIG. 5 A modified form of embodiment of a device in
accordance with the invention for deforming an essentially flat
blank into a thin-walled, shell-type body.
[0070] FIG. 6 A further modified form of embodiment of a device in
accordance with the invention for deforming an essentially flat
blank into a thin-walled, shell-type body.
[0071] FIG. 7 A schematic plan view of a further different form of
embodiment of a device in accordance with the invention for
deforming an essentially flat blank into a thin-walled, shell-type
body.
[0072] The device 10 in accordance with the invention and/or the
method in accordance with the invention is/are provided for forming
or deforming an essentially flat blank 12 or an essentially flat
round blank of metal, particularly of aluminum or a, preferably
hardenable, aluminum alloy such as Al 2219 or Al 2195 into a
(thin-walled) shell-type body 14, shell-shaped component or similar
formed part, and regardless of whether in a hot or cold condition.
In the following description of various examples of embodiment of
the device 10 in accordance with the invention, corresponding
components that are the same are provided with identical reference
designators.
[0073] The device 10 and/or the method in accordance with the
invention is/are suitable especially for producing shell-shaped
components that are rotationally symmetrical and/or not
rotationally symmetrical. In a clearly advantageous manner, the
device 10 and/or the method in accordance with the invention is/are
used for the production of hemispherical, spherical-cap shaped,
dome shaped, ellipsoidal-dome shaped, conical and elliptical
components or Casini-shaped components or components with other
shapes of cross-section.
[0074] In a quite advantageous manner, the device 10 in accordance
with the invention and/or the method in accordance with the
invention is/are suitable for the production of shells as domes for
rocket fuel tanks, satellite tanks, parabolic antennas, parabolic
reflector dishes, parabolic solar collectors, searchlight housings,
tank ends, tower cupolas, pressure domes or similar.
[0075] Furthermore, the practical use of the device 10 in
accordance with the invention and/or the method in accordance with
invention for rolling, particularly compaction rolling of defined
surfaces of a, including finished, (thin-walled) shell-type body 14
has proved particularly useful.
[0076] FIG. 1 shows a first form of embodiment of such a device 10
in accordance with the invention or similar spinning lathe for
forming or deforming an essentially flat blank 12 of metal into a
thin-walled, shell-type body 14.
[0077] The device 10 has a supporting structure 16 that forms or
encloses, i.e. encloses or limits, a mold chamber 18. The
supporting structure 16 holds the blank 12 during increasing
deformation into a thin-walled, shell-type body 14. To form the
mold chamber 18, the supporting structure 16 is essentially
cup-shaped, pot-shaped, dish-shaped, cone-shaped, truncated
cone-shaped or a similar hollow shape. The supporting structure 16
preferably consists of materials that are adequately temperature
resistant.
[0078] Furthermore, the device 10 in accordance with the invention
includes a device 20 for clamping the blank 12 around its
circumference 22 to the supporting structure 16. The device 20 for
clamping the blank 12 is in this case arranged on the supporting
structure 16 or held by it. The device 20 for clamping the blank 12
seals the reverse face 24 of the blank 12 facing towards the mold
chamber 18 against the front face 26 of the blank 12 facing away
from the mold chamber 18. The interior of the mold chamber 18 is
thus insulated from the environment.
[0079] Finally, the device 10 in accordance with the invention has
a device 28 for applying a vacuum and evacuating the mold chamber
18. The device 28 for applying the vacuum and evacuating the mold
chamber 18 is allocated to the mold chamber 18 and is in connection
with same, in order to communicate with same.
[0080] The supporting structure 16 of the form of embodiment of the
device 10 shown in FIG. 1 has at least one device 30, especially
one that can be variably controlled, for warming and/or heating the
blank 12, that radiates to or into the mold chamber 18. The device
30 for warming and/or heating the blank 12 can be designed as an
electrically operated light lamp heater, internal or external
infrared radiation heater, induction heater or circulation-type
heater with a circulating heat carrier, such as water, oil, molten
salt or sodium. Any other forms of embodiment of the device 30 as
heat sources for warming and/or heating the blank 12 are equally
conceivable. Furthermore, other heat sources or devices 31 for
warming and/or heating the blank 12 that are, for example, arranged
outside the mold chamber 18 are also possible.
[0081] As can be seen from FIG. 1, the supporting structure 16 of
the device 10 in accordance with the invention is further fitted
with at least one device 32 for thermal insulation. The device 32
for thermal insulation is fitted to the inside of the supporting
structure 16 and thus allocated to the mold chamber 18. The device
32 for thermal insulation can be a thermal insulating layer, for
example on a glass fiber or ceramic base.
[0082] Alternatively or in addition, the supporting structure 16 of
the device 10 in accordance with the invention, as shown in FIG. 1,
also has at least one device 34 for heat reflection. The device 34
for heat reflection is attached to the inside of the supporting
structure 16 and is thus also allocated to, or facing, the mold
chamber 18. The device 34 for thermal reflection can, for example,
be a reflecting (multiscreen) reflector film.
[0083] Without being shown in detail, the supporting structure 16
of the device 10 in accordance with the invention can additionally
be provided with a device for active cooling 134. For example, the
device for active cooling 134 can consist of an internal cooling
system with for example water or oil as the coolant.
[0084] The device 32 for thermal insulation and/or the device 34
for heat reflection assist the establishment and maintenance of an
elevated temperature profile in the inside of the mold chamber 18
and thus the warming and/or heating of the blank 12 at the same
time. The device 32 for thermal insulation and the device 34 for
heat reflection also serve to provide thermal protection, if
appropriate, to the supporting structure 16 itself, in conjunction
with the device for active cooling 134.
[0085] As shown schematically in FIG. 1, a device 36 for monitoring
the temperature of the mold chamber 18 and/or of the blank 12 is
allocated to the supporting structure 16 of the device 10 in
accordance with the invention and/or the blank 12. The device 36
for monitoring the temperature can in this case include
thermocouples 38 fitted to the reverse face 24 of the blank 12 and,
in addition or as an alternative, a thermal imaging camera 40
facing the front face 26 of the blank 12. In this respect, a point
and/or area-wide temperature monitoring is provided.
[0086] For detachable fixing of the blank 12 to the supporting
structure 16, the device 20 is provided with a pressure ring 42 and
clamping ring 44 for clamping the blank 12 as shown in FIG. 1. The
clamping ring 44 can, for example, be secured by means of bolts
(not shown) to the pressure ring 42 with the blank 12 arranged in
between. To completely seal the mold chamber 18 against the
environment by the blank 12 at the same time, the device 20
additionally has a sealing ring 46 for clamping the blank 12. The
sealing ring 46 is positioned between the pressure ring 42 and
clamping ring 44. The sealing ring 46 can, for example, be an
O-ring. It is also equally conceivable that the sealing ring 46 is
a rubber-type profile with a U-shaped cross-section, that is placed
on the circumference 22 of the blank 12 before clamping the
clamping ring 44 to the pressure ring 42. Other constructive
designs that completely seal the mold chamber 18 against the
environment by means of the blank 12 are, without being shown in
detail, equally conceivable.
[0087] When deforming and/or forming or concave pressing of the
essentially flat blank 12 into a thin-walled, shell-type body 14,
thermal distortion due to the temperature application can occur in
the area of the device 20 for clamping the blank 12, due to unequal
expansion of the clamped blank 12 and supporting structure 16. An
impermissible thermal distortion of this kind can be counteracted
in that the supporting structure 16 is fitted with a device for
reducing radial and/or circumferential thermal expansion 47 between
the blank 12 and the device 20 for clamping the blank 12 (not
illustrated). Thus for example, the device 20 for clamping the
blank 12 can be designed so as to be displaceable radially and/or
circumferentially relative to the supporting structure 16 (also not
illustrated). Equally conceivable is a design of the supporting
structure 16 that ensures adequate flexibility of the supporting
structure 16 when subjected to radially- and/or
circumferentially-acting stresses, without impairing the
deformation strength of the supporting structure 16 when subjected
to (negative) pressure, especially in the area of the device 20 for
clamping the blank 12. The stress conditions themselves within the
blank 12 due to effects of (negative) pressure can also be
advantageously compensated for.
[0088] The deforming and/or forming or concave pressing of the
essentially flat blank 12 into a thin-walled, shell-type body 14
with the device 10 in accordance with the invention is based solely
on the application of (negative) pressure and temperature to the
blank 12. The blank 12 is thus mainly automatically brought from an
essentially flat shape to a rotationally symmetrical or non
rotationally symmetrical (hollow) shape by the effect of external
pressure and temperature.
[0089] Optionally, in the form of embodiment of the device 10 in
accordance with the invention shown in FIG. 1, a perforated mating
mold 48, comparable to the form of embodiment of the device 10
shown in FIG. 3, can be allocated to the supporting structure 16.
The perforated mating mold 48 is arranged in the mold chamber 18
and is used to hold and support the blank 12 to be deformed into
the thin-walled, shell-type body 14. Therefore, the perforated
mating mold 48 is partly used as a template for the final shape of
the thin-walled, shell-type body 14 to be achieved. The perforated
mating mold 48 thus serves to precisely define the final shape to
be achieved of the thin-walled, shell-type body 14. The
perforations in the mating mold 48 are necessary in order to be
able to apply the vacuum to the mold chamber 18 and then to be able
to evacuate the mold chamber 18. As shown in FIG. 1, the clear
space bounded by the perforated mating mold 48, that is finally
completely filled by the thin-walled, shell-type body 14, is
smaller than the mold chamber 18 itself and is therefore not
identical to the mold chamber 18.
[0090] In an alternative or additional embodiment of the device 10
in accordance with the invention, at least one forming tool 50 is
furthermore allocated to the supporting structure 16, that comes
into contact with the front face 26 of the blank 12 and is thus
applied to the front face 26 of the blank 12. The forming tool 50
is used to support the deforming and/or forming or concave pressing
by the device 10. Only one such forming tool 50 is provided for the
form of embodiment of the device 10 shown in FIG. 1. Here, the
forming tool 50 is designed as a forming or pressure roller.
Without being shown in detail, the forming tool 50 can, however,
also be designed as a pressure ball that is preferably
hydrostatically mounted, by means of which the tracking of the
angle of inclination of a forming or pressure roller, necessary in
many cases, can be avoided.
[0091] In an advantageous manner, the at least one forming tool 50
that is applied to the front face 26 of the blank 12 is controlled
using a template or numerically using closed-loop and/or open-loop
control.
[0092] The supporting structure 16 together with the blank 12 and
the at least one forming tool 50 are furthermore designed to be
rotatable relative to each other.
[0093] With the form of embodiment of the device 10 shown in FIG.
1, the supporting structure 16 together with the blank 12 clamped
to it is rotatably mounted, while the at least one forming tool 50
can be moved only along a fixed meridian. For this purpose, the
supporting structure 16 together with the blank 12 is designed to
be rotated by a drive device 54 about a central axis of rotation 52
of the supporting structure 16. A rotation of the supporting
structure 16 together with the blank 12 takes place therefore by
means of the drive device 54 according to arrow 56. A connection 58
for applying a vacuum to the mold chamber 18 and for evacuating the
mold chamber 18, a supply connection 60 for electrical power and a
supply connection 62 for electrical signals, for example using
wiper rings (not illustrated in more detail), are located on the
central axis of rotation 52.
[0094] The axis of rotation 52 of the supporting structure 16 is in
this case appropriately horizontally arranged. Without being shown
in detail, the axis of rotation 52 can also be equally arranged
vertically.
[0095] The at least one forming tool 50 can in contrast be moved in
two dimensions on a meridian curve fixed in space or can be rigidly
mounted by means of two servodrive device 64, 66, that for example
interact with a roller drive 68, as shown by the double arrows 70,
72. The roller guide 68 is rigidly mounted.
[0096] As can be seen from FIG. 1, the forming tool 50 in the form
of a forming or pressure roller is permanently set with respect to
the central axis of rotation 52 of the supporting structure 16. The
attitude of the forming tool 50 applied to the front face 26 of the
blank 12 can of course be individually set with respect to the axis
of rotation 52 of the supporting structure 16. The angle or
articulation of the forming tool 50 can therefore if necessary be
changed or adjusted as required, for example relative to the radius
on which the forming tool 50 is actually guided.
[0097] The form of embodiment of the device 10 in accordance with
the invention shown in FIG. 2 differs from the form of embodiment
of the device 10 shown in FIG. 1 mainly in that the supporting
structure 16 together with the blank 12 is rigidly mounted, whereas
the at least one forming tool 50 can be rotated.
[0098] As can be clearly seen in FIG. 2, there is also a total of
two forming tools 50 provided as forming or pressure rollers. The
deforming and/or forming or concave pressing of the blank 12 into a
thin-walled, shell-type body 14 can be substantially accelerated by
forming tools 50 that are operated either simultaneously or
individually. The forming tools 50 can in this case be offset
radially and/or in azimuth, to enable the blank 12 to be machined
at different distances simultaneously. Such a synchronous design of
several individual deforming and/or forming or pressing steps
results in a substantial overall shortening of the particular
production interval.
[0099] The two forming tools 50 in the form of embodiment of device
10, shown in FIG. 2, are arranged on a traverse 74 and supported by
same. The traverse 74 extends diametrically over the complete
supporting structure 16 together with the blank 12. The central
axis of rotation 52 of the traverse 74 in this case runs
vertically.
[0100] The two forming tools 50 are therefore each subjected to a
rotation of the traverse 74 about their central axis of rotation
52. A rotation of the traverse 74 takes place in the case of the
present example of an embodiment of the device 10 shown in FIG. 2
by means of a drive device 76 as shown by arrow 78. At the same
time, the two forming tools 50 can each be moved by the two
servodrive devices 80, 82 on a meridian curve relative to the
traverse 74, in a radial direction corresponding to the double
arrow 84 and in a vertical direction corresponding to the double
arrow 86.
[0101] Because of the rigid mounting design of the supporting
structure 16 together with the blank 12, a simple construction is
obtained with the form of embodiment of the device 10 shown in FIG.
2. Because the vacuum connection 58, the supply connection 60 for
electric power and the supply connection 62 for electric signals do
not have to be passed in and through the central axis of rotation
52 of the supporting structure 16 but can instead be rigidly
installed, the construction cost can be substantially reduced. The
vacuum connection 58, that communicates in a simple manner with the
mold chamber 18, is referred to only as an example. Furthermore,
all the centrifugal force stresses on the supporting structure 16
and/or the blank 12, and the other components such as the device 20
for clamping the blank 12, the device 30 for warming and/or heating
the blank 12, the device 32 for thermal insulation or the device 34
for heat reflection are omitted.
[0102] In the case of the form of embodiment of the device 10 shown
in FIG. 2, the traverse 74 is guided on a rail arrangement 88. The
rail arrangement 88 is supported on a rail supporting structure 90.
The rail supporting structure 90 is formed by the pillars 92
anchored in the ground and a carrier ring 94, the end of which is
supported by the pillars 92.
[0103] The rail arrangement 88 includes a ring gear 96 to which the
traverse 74 is attached. The ring gear 96 is itself mechanically
connected on the underside to a rail ring 98. The rail ring 98
holds a number of fixed guide rollers 100 that are distributed
equidistantly along the inner and outer circumference of the ring,
centered precisely on the central axis of rotation 52. Because the
rail ring 98 engages in a prism guide or prism-shaped notches 102
in the guide rollers 100, the rail ring 98 and thus the traverse 74
cannot lift out of the rail arrangement 88. Immediately the rail
ring 98 circulates, the guide rollers 100 rotate about the axis of
the pin 104 anchored in a ring plate 106. The ring plate 106 is in
turn supported by the carrier ring 94 of the rail supporting
structure 90.
[0104] The traverse 74 is rotated by the drive device 76 that in
the form of embodiment of the device 10 shown in FIG. 2 is an
electric motor. The drive device 76 is attached to the rail
supporting structure 90. The drive device 76 drives a pinion 108
that engages in the ring gear 96, with which the traverse 74 is
connected via the support 110. As an alternative, the drive device
76 can also be designed as a special stepper motor pulled by
magnetic fields circulating in the rail ring 98.
[0105] The power supply for the server motor drive devices 80, 82
mounted on the traverse 74 is provided centrally via a current
collector shaft 112, that for example is provided with slip
rings.
[0106] The traverse 74 is, as shown clearly in the form of
embodiment of the device 10 illustrated in FIG. 2, to be detached
from the ring gear 96 or guide rollers 100 with the prism-shaped
notches 102, i.e. the circulating prism-shaped ring, and the
support 110 in order to replace the blank 12 by a thin-walled,
shell-type body 14 and vice versa, and then can be lifted off by a
hoist (not illustrated), for example a workshop crane, and set down
at the side of the device 10.
[0107] The form of embodiment of the device 10 shown in FIG. 3
differs from that shown in FIG. 2 only in that, additionally, a
perforated mating mold 48 is arranged in the mold chamber 18 by
means of which a deforming and/or forming or concaving pressing of
the mold 12 into a thin-walled, shell-type body 14 is assisted.
[0108] In accordance with the example of an embodiment of the
device 10 in accordance with the invention, shown schematically in
FIG. 4, the traverse 74 can, as shown by the double arrow 114, be
rotated on the rail ring 98 about the central axis of rotation 52.
The two forming tools 50 can, as shown by the double arrows 116, be
moved backwards and forwards along the traverse 74. To replace a
blank 12 by a thin-walled, shell-type body 14 and vice versa, the
traverse 74 can be moved by rail switches 118 on two straight
parallel rails 120 along the double arrow 122. Both straight
parallel rails 120 are in this case tangentially connected to the
rail ring 98. In this way, the traverse 74 can move sideways into a
position in which the blank 12 and/or the thin-walled, shell-type
body 14 can be easily lifted out from the supporting structure 16,
or lifted into the supporting structure 16, by a hoist (again not
illustrated) such as a workshop crane.
[0109] FIG. 5 shows a further form of embodiment of the device 10
in accordance with the invention. With the form of embodiment of
the device 10 shown in FIG. 5, the supporting structure 16 can be
lowered and positioned at a lower level on the side as shown by the
double arrow 123, either hydraulically or by using a hoist (not
illustrated), e.g., a workshop crane.
[0110] In the form of embodiment of the device 10 in accordance
with the invention shown in FIG. 6, the supporting structure 16 can
be moved in and out through an opening in the rail supporting
structure 90 underneath the rails or similar carrier ring 94. This
is enabled by the special design of the rail arrangement 88 that is
arranged above the level spanned by the blank 12.
[0111] FIG. 7 is a schematic of a further different form of
embodiment of the device 10 in accordance with the invention.
According to this, the traverse 74 with this form of embodiment of
the device 10 is again moved on two straight parallel rails 124 or
similar, diametrically above the supporting structure 16, together
with the blank 12 to be formed. The supporting structure 16 is thus
rigidly mounted. The traverse 74 can be moved linearly backwards
and forwards along the two parallel rails 124 of the double arrow
126 by means of a drive device 76 (not illustrated) by NC control.
The traverse 74 is fitted with at least one forming tool 50 in the
form of a forming or pressure roller. The forming tool 50 is
actuated by a servodrive device 128 relative to, and vertical to,
the traverse 74, and also vertical to the straight parallel rails
124 according to the double arrow 130. Therefore the forming tool
50 can describe a great circle at a defined height on the
non-rotating blank 12, corresponding to the interactive control
actions of the drive device 76 for the traverse 74 and the
servodrive device 128 for the forming tool 50, in such a way that
the great circle is formed from a superimposition of a programmed
sinusoidal or cosinusoidal feed function in each case. Additional
servodrive devices (not illustrated) are necessary for setting the
vertical height position or pressing depth and for the inclination
or articulation of the forming tool 50 relative to the central axis
of rotation 52 of the blank 12 or of the thin-walled, shell-type
body 14. Therefore, an additional servodrive device in the form of
a stepper motor for the vertical height positioning and a further
servodrive device in the form of a geared lever device for the
inclination can be provided. For replacing a blank 12 by a
thin-walled, shell-type body 14 and vice versa, the traverse 74 can
be easily moved and parked outside the supporting structure 16.
[0112] Without showing the details, it is of course possible at any
time to perform a kinematic reversal of the form of embodiment of
the device 10 in accordance with the invention as shown in FIG. 7.
Accordingly, the supporting structure 16 can be moved backwards and
forwards on two straight parallel rails 124 instead of the traverse
74. The traverse 74 with the weight of the heavy servodrive device
128 and the additional servodrive devices in the form of stepper
motors or geared-lever device, however, remain rigidly mounted. The
controller of the drive device 76 of the traverse 74, the
servodrive device 128 of the forming tool 50 and the additional
servodrive devices remains unchanged. The vacuum connection 58 and
the supply connections 60, 62 for the electrical power and
electrical signals are carried in flexible leads/hoses.
Alternatively, a vacuum pump can also be fitted in the supporting
structure 16 and the electrical power supplied safely using low
voltage, for example via the rails or similar.
[0113] Without being shown in detail, the supporting structure 16
can also have a thermally insulated, especially provided with
heating surfaces, covering element or similar cover plate 132 for
covering the front face 26 of the blank 12 facing away from the
mold chamber 18. Accordingly, the blank 12 or shell-type body 14
can be covered on the supporting structure 16 during the heat
treatment and its temperature raised to the particular required
heat treatment temperatures by means of the existing heating
surfaces.
[0114] By means of the design features, also not shown in more
detail, whereby the supporting structure 16 provided with at least
one safety device 136 allocated to the mold chamber 18 for
protection against external effects by gaseous and/or liquid
coolant, particularly inert gas, preferably argon, nitrogen or
water, the blank 12 or shell-type body 14 is enabled to remain
clamped on the supporting structure 16 until final removal, to thus
undergo further machining and/or heat treatment, for example
solution annealing, quenching or age hardening. In this way the
blank 12 or the shell-type body 14 after its initial pressing does
not need time-consuming removal for the subsequent heat treatment
or subsequent time-consuming refitting for the stretching. The heat
treatment of the blank 12 can thus be carried out directly in the
supporting structure 16 in the fitted condition. The time saving is
particularly significant with large blanks 12 or shell-type bodies
14. Accordingly, a shell-type body 14 made of Al 2219, for example,
can be solution annealed at 535.degree. C. after initial pressing,
quenched, stretched and then age hardened as necessary at
160.degree. C. to 190.degree. C. to achieve the T8x condition.
[0115] By means of such a structural embodiment of the device 10 in
accordance with the invention, it is easily possible to produce a
thin-walled, shell-type body 14 from an essentially flat blank 12
of metal.
[0116] The method in accordance with the invention for forming an
essentially flat blank 12 of metal into a thin-walled, shell-type
body 14 using the device 10 is explained in more detail:
First, the blank 12 is clamped over its circumference 22 on the
supporting structure 16 to the mold chamber 18. From the mold
chamber 18, the blank 12 is held during the increasing deformation
into a thin-walled, shell-type body 14. At the same time, the rear
face 24 of the blank 12 facing towards the mold chamber 18 is
sealed against the front face 26 of the blank 12 facing away from
the mold chamber 18. A vacuum is then applied to the mold chamber
18 sealed by the blank 12. By means of a defined evacuation of the
mold chamber 18, the blank 12 is then formed into a thin-walled,
shell-type body 14. In doing so, the surface of the blank 12 is
stretched with the original thickness being reduced. Contact does
not occur between the blank 12 or thin-walled, shell-type body 14,
and the supporting structure 16 or its components, because of the
limiting and continuous monitoring of the vacuum and a controlled
travel movement of the forming tool 50.
[0117] Before forming, the blank 12 is brought to an elevated
temperature profile by means of the at least one device 30,
allocated to the mold chamber 18, for warming and/or heating the
blank 12. Furthermore, heat sources such as devices 31 can also be
used, that heat the blank 12, if necessary, from both sides 24, 26,
raise it quickly to the specified temperatures and maintain it at
these temperatures during the deforming and/or forming or concave
pressing. In order then to avoid heat losses and at the same time
maintain the elevated temperature profile, the blank 12 is
furthermore held at the elevated temperature profile by means of
the at least one device 32 for thermal insulation and/or the at
least one device 34 for heat reflection.
[0118] The blank 12 can, as appropriate, be deformed into a
thin-walled, shell-type body 14 by means of a mating mold 48
arranged in the mold chamber 18 and, alternatively or in addition,
by means of at least one forming tool 50 applied to the front face
26 of the blank 12. At least one forming or pressure roller and/or
a pressure ball is/are preferably used as the forming tool 50. In
the latter case, the pressure ball is more appropriately
hydrostatically mounted.
[0119] When applying the forming tool 50 to the front face 26 of
the blank 12, it is especially advantageous if the forming tool 50
is moved relative to the blank 12 from the circumference 22 to the
centre and/or from the centre to the circumference 22. The forming
tool 50 in this case is preferably controlled by a (metal) template
or numerically, using closed-loop and/or open-loop control.
[0120] Before forming the blank 12 into a thin-walled, shell-type
body 14 by means of the device 10 in accordance with the invention,
it is especially advantageous if the blank 12 is made from at least
two separate surface elements. The at least two separate surface
elements can in this case be joined to form a single unit by means
of tungsten inert gas (TIG) welding, metal inert gas (MIG) welding,
friction stir welding (FSW), electronic beam (EB) welding, laser
welding, plasma welding or any other suitable method of welding. In
this way, large blanks 12 that can then be deformed and/or formed
or concave-pressed into a thin-walled, shell-type body 14 can also
be produced.
[0121] If the blank 12 is made of several separate surface
elements, it can be particularly advantageous if the blank 12 is
soft annealed in a conventional manner before forming.
[0122] The blank 12 is, in a preferred manner, pre-contoured by
chip removal, especially by turning, milling and/or grinding,
before forming into a thin-walled, shell-body 14. In doing so, a
predetermined wall thickness distribution of the blank 12 is set to
obtain a required final wall thickness of the thin-walled,
shell-type body 14. In this connection, it is particularly useful
if the blank 12 is contoured on its rear face 24. In the case of an
application to the front face 26 of the blank [12], a smooth
movement of the forming tool 50 is thus guaranteed.
[0123] Furthermore, it is useful if the blank 12 before forming
and/or stretching into a thin-walled, shell-type body 14 is
provided with openings, perforations or similar cutouts by chip
removal that then by means of covers, particularly a film, are
temporarily vacuum-sealed. The chip removal in this case can be by
means of turning, milling and/or grinding, with suitable openings,
perforations or similar cutouts being made particularly in the pole
area or in the centre of the blank 12.
[0124] Before the blank 12 is deformed and/or formed or concave
pressed into the thin-walled, shell-type body 14 by means of the
device 10 in accordance with the invention, it can be advantageous
to subject the blank 12 to further preparatory processing steps. It
is thus conceivable to preform the blank 12 if required and/or
prepress, solution anneal, quench to obtain condition T4, then cold
form, age harden in an oven and bring to condition T8.
[0125] In order to obtain the dimensional accuracy, it is very
advantageous to subject the blank 12 to continuous measurement
during the deforming into the thin-walled, shell-type body 14.
[0126] By means of the method and the device 10 in accordance with
the invention, domes, for example for the fuel tank of the Ariane
5, are meanwhile being manufactured that have a diameter of 5.4 m
and above and wall thickness of about a maximum of 7 mm on the edge
and approximately 3.3 mm in the area of the shell-type body 14.
[0127] The invention is not limited to the forms of embodiment of
the device 10 in accordance with the invention shown. It is thus
easily possible to fit the supporting structure 16 with a device
terminating in the mold chamber 18 for the supply of a protective
gas (not illustrated). In this way, the oxidation of the blank 12
or thin-walled, shell-type body 14 is further stemmed during the
warming and/or heating or further processing or heat treatment, in
order to minimize the subsequent surface cleaning at the same
time.
* * * * *