U.S. patent application number 11/352953 was filed with the patent office on 2006-08-17 for method and apparatus for making tubes.
This patent application is currently assigned to Benteler Automobiltechnik GmbH. Invention is credited to Wolfgang Streubel.
Application Number | 20060179769 11/352953 |
Document ID | / |
Family ID | 35911086 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060179769 |
Kind Code |
A1 |
Streubel; Wolfgang |
August 17, 2006 |
Method and apparatus for making tubes
Abstract
In a method of making a tube a sheet metal blank. having
opposite longitudinal flanks is placed in a die of a shaping tool.
At least one of the longitudinal flanks of the sheet metal is
provided with a contact projection suitable for resistance pressure
welding. The blank is pressed into a U-shaped cavity of the cavity
by a ram to shape the blank into a U-shaped configuration which is
then shaped between an upper mold and a lower mold of a molding
press into a tubular profile with the longitudinal flanks
confronting one another. The upper mold has in an area of the
confronting longitudinal flanks oppositely poled electrode strips
which are insulated against one another. During subsequent welding
operation, the contact projection on the one longitudinal flank is
welded to the confronting longitudinal flank as a result of welding
heat generated through introduction of an electric current via the
electrode strips into the longitudinal flanks and a clamping
pressure by which the upper and lower molds are held together.
Inventors: |
Streubel; Wolfgang;
(Detmold, DE) |
Correspondence
Address: |
HENRY M FEIEREISEN, LLC
350 FIFTH AVENUE
SUITE 4714
NEW YORK
NY
10118
US
|
Assignee: |
Benteler Automobiltechnik
GmbH
Paderborn
DE
|
Family ID: |
35911086 |
Appl. No.: |
11/352953 |
Filed: |
February 13, 2006 |
Current U.S.
Class: |
52/582.1 |
Current CPC
Class: |
B21C 37/0826 20130101;
B23K 2101/06 20180801; B21C 37/0815 20130101; B23K 11/0873
20130101; B23K 33/006 20130101; B21C 37/157 20130101 |
Class at
Publication: |
052/582.1 |
International
Class: |
E04B 2/00 20060101
E04B002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 11, 2005 |
DE |
10 2005 006 579.1 |
Claims
1. A method of making a tube, comprising the steps of: placing in a
shaping tool a sheet metal blank having opposite longitudinal
flanks; providing at least one of the longitudinal flanks of the
sheet metal with contact projections suitable for resistance
pressure welding; pressing the blank into a U-shaped cavity of a
lower mold of the shaping tool by a ram to shape the blank into a
U-shaped configuration; shaping the U-shaped blank between an upper
mold and the lower mold into a tubular profile with the
longitudinal flanks confronting one another, wherein the upper mold
has in an area of the confronting longitudinal flanks oppositely
poled electrode strips which are insulated against one another; and
welding the contact projections on the one longitudinal flank to
the confronting longitudinal flank as a consequence of welding heat
generated through introduction of electrical current by means of
the electrode strips into the longitudinal flanks, and an applied
clamping pressure that holds the upper and lower molds
together.
2. The method of claim 1, wherein both longitudinal flanks are
formed with said contact projections.
3. The method of claim 2, wherein the contact projections of the
longitudinal flanks are disposed in offset relationship.
4. The method of claim 2, wherein the contact projections of the
longitudinal flanks oppose each other in pairs.
5. Apparatus for making a tube, comprising a shaping tool having an
upper mold and a lower mold for shaping a U-shaped blank into a
substantially tubular profile, said upper mold having electrode
strips which are disposed in an area of confronting longitudinal
flanks of the tubular profile in parallel relationship to the
longitudinal flanks, said electrode strips being insulated against
one another and including contact surfaces facing an outer
circumference of the tubular profile for introduction of a welding
current into the tubular profile.
6. The apparatus of claim 5, wherein the contact surfaces of the
electrode strips have a contour which conforms to the outer
circumference of the tubular profile.
7. The apparatus of claim 5, wherein the contact surfaces of the
electrode strips are part of a shaping contour of the upper
mold.
8. The apparatus of claim 5, wherein the electrode strips are
configured as mirror images in relation to a longitudinal center
plane between the longitudinal flanks to be welded.
9. The apparatus of claim 5, further comprising an insulation
layer, disposed in a longitudinal center plane between the
longitudinal flanks to be welded, for separating the electrode
strips form one another.
10. The apparatus of claim 5, wherein the contact surfaces of the
electrode strip are pieced at uniform distances at the outer
circumference of the tubular profile by the upper mold which
carries the electrode strips.
11. The apparatus of claim 5, wherein each said electrode strip has
a generally comb-shaped configuration, with a spine and plural
spaced-apart electrode fingers extending from the spine.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the priority of German Patent
Application, Serial No. 10 2005 006 579.1, filed Feb. 11, 2005,
pursuant to 35 U.S.C. 119(a)-(d), the content of which is
incorporated herein by reference.
[0002] This is one of two applications both filed on the same day.
Both applications deal with related inventions. They are commonly
owned and have the same inventive entity. Both applications are
unique. Accordingly, the following U.S. patent application is
hereby expressly incorporated by reference: "Method and Apparatus
for Making Tubes".
BACKGROUND OF THE INVENTION
[0003] The present invention relates, in general, to a method and
apparatus for making tubes.
[0004] DD 276 043 A1 discloses a method and apparatus for making
thin-walled tubes from sheet metal blanks by using indirect lap
welding. The apparatus includes a molding press having a shaping
tool which is comprised of a lower forming piece, which has a
semicircular cavity to embrace the blank from outside, a
cylindrical mandrel with incorporated copper rail, and two upper
forming pieces. A drawback of this construction is its complexity
of the overall apparatus.
[0005] It would therefore be desirable and advantageous to provide
an improved method and apparatus for making a tube from a sheet
metal blank to obviate prior art shortcomings and to operate more
efficiently.
SUMMARY OF THE INVENTION
[0006] According to one aspect of the present invention, a method
of making a tube includes the steps of placing in a shaping tool a
sheet metal blank having opposite longitudinal flanks, providing at
least one of the longitudinal flanks of the sheet metal with
contact projections suitable for resistance pressure welding,
pressing the blank into a U-shaped cavity of a lower mold of the
shaping tool by a ram to shape the blank into a U-shaped
configuration, shaping the U-shaped blank between an upper mold and
the lower mold into a tubular profile with the longitudinal flanks
confronting one another, wherein the upper mold has in an area of
the confronting longitudinal flanks oppositely poled electrode
strips which are insulated against one another, and welding the
contact projections on the one longitudinal flank to the
confronting longitudinal flank as a consequence of welding heat
generated through introduction of electrical current by means of
the electrode strips into the longitudinal flanks, and an applied
clamping pressure that holds the upper and lower molds
together.
[0007] The present invention resolves prior art problems by joining
the longitudinal flanks together through resistance projection
welding in the area of the contact projections. No lap welding is
involved. As the longitudinal flanks are held together under the
pressure, the sheet metal blank is able to lie against the shaping
tool. No mandrel is necessary to force the areas to be welded
against one another and no mandrel needs to be pulled out from the
tube or vice versa. As a result, the manufacturing process is
simplified and faster to implement for producing various types of
pressure-resistant tubes or other tubes for various applications
such as, e.g., as dashboard support, door impact support, or for
use in the chassis region for axles. Applications other than those
in the automobile industry are, of course, also conceivable in the
event a load-carrying capability of the tubular profile is
desired.
[0008] There are many ways of arranging the contact projections.
For example, the contact projections may be provided on one or both
longitudinal flanks. The contact projections of the longitudinal
flanks may be disposed in offset relationship or in pairs. An
arrangement of the contact projections in offset relationship in
particular results in quasi intermeshing of the longitudinal
flanks. The geometry of the projection determines also whether or
not the tubes are tight.
[0009] Provision of further manufacturing steps are, of course,
also conceivable, such as subsequent welding operations to partly
or completely weld together the longitudinal flanks, in the event
the strength of the connection should meet locally more stringent
demands.
[0010] According to another aspect of the present invention, an
apparatus for making a tube includes a shaping tool having an upper
mold and a lower mold for shaping a U-shaped blank into a
substantially tubular profile, with the upper mold having electrode
strips which are disposed in an area of confronting longitudinal
flanks of the tubular profile in parallel relationship to the
longitudinal flanks, wherein the electrode strips are insulated
against one another and include contact surfaces facing an outer
circumference of the tubular profile for introduction of a welding
current into the tubular profile.
[0011] According to another feature of the present invention, the
contact surfaces of the electrode strips may have a contour which
conforms to the outer circumference of the tubular profile. The
contact surfaces of the electrode strips may hereby be part of a
shaping contour of the upper mold. In this way, the outer
circumference of the tubular profile is protected against burning,
and the service life of the electrode strips is increased.
[0012] In general, it is also possible to provide a plurality of
individual electrodes lined up in rows to define overall an
electrode strip which is in contact with the tubular profile at
individual contact zones but not along the entire length of the
tubular profile. Electrodes made of copper typically have a smaller
wear resistance than a shaping tool of steel. To prevent excess
wear in the area of the electrode strips, the contact region of the
electrode strip may be pierced by the at the outer circumference of
the tubular profile at even distances by the upper mold that
carries the electrode strips. In other words, the electrode strip
may have a generally comb-shaped configuration, with the spine of
the electrode comb joining together all spaced-apart electrode
fingers. The electrode fingers are hereby in contact with the outer
circumference of the tubular profile and may continuously adjust as
wear increases.
[0013] According to another feature of the present invention, the
electrode strips may be configured as mirror images in relation to
a longitudinal center plane between the longitudinal flanks to be
welded.
[0014] According to another feature of the present invention, an
insulation layer may be disposed in a longitudinal center plane
between the longitudinal flanks to be welded, for separating the
electrode strips form one another.
BRIEF DESCRIPTION OF THE DRAWING
[0015] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
currently preferred exemplified embodiments of the invention with
reference to the accompanying drawing, in which:
[0016] FIGS. 1a to 1d are schematic views of forming steps for
shaping a sheet metal blank into a tubular configuration;
[0017] FIG. 2 is a schematic illustration, on an enlarged scale, of
a detail of an upper mold in accordance with the present invention;
and
[0018] FIGS. 3a to 3c are schematic illustrations of four
embodiments of sheet metal blanks for use in a method according to
the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] Throughout all the Figures, same or corresponding elements
are generally indicated by same reference numerals. These depicted
embodiments are to be understood as illustrative of the invention
and not as limiting in any way. It should also be understood that
the drawings are not necessarily to scale and that the embodiments
are sometimes illustrated by graphic symbols, phantom lines,
diagrammatic representations and fragmentary views. In certain
instances, details which are not necessary for an understanding of
the present invention or which render other details difficult to
perceive may have been omitted.
[0020] Turning now to the drawing, and in particular to FIG. 1a,
there is shown a schematic illustration of a molding press,
generally designated by reference numeral 1, for shaping a sheet
metal blank 2 in a first manufacturing step from a flat
configuration to a U-shaped configuration. The molding press 1
includes a shaping tool having a ram 3 and a lower mold 5 which is
formed with a U-shaped cavity 4. After placing the flat blank 2 on
the lower mold 5, the ram 3 is lowered in the direction of the
lower mold 5 to force the blank 2 into the cavity 4 and thereby
shape the blank 2 to assume the U-shaped configuration. This
shaping step is shown in FIG. 1b.
[0021] A subsequent second manufacturing step transforms the
U-shaped blank 2 to a tubular profile R, as shown in FIGS. 1c and
1d. The U-shaped blank 2 of FIG. 1b is placed into a cavity of the
lower mold 5, as shown in FIG. 1c. Subsequently, an upper mold 6 is
moved in a direction of arrow P towards the lower mold 5 to shape
the blank 2 into a tubular profile R. This is shown in FIG. 1d.
During the shaping operation, the initially parallel legs of the
U-shaped blank 2 are curved inwards so that their longitudinal
edges 7, 8 confront one another in midsection of the upper mold
6.
[0022] Referring now to FIG. 2, there is shown a schematic
illustration, on an enlarged scale, of a detail of an upper mold 6
in accordance with the present invention, depicting the contact
region of the longitudinal flanks 7, 8 of the tubular profile R.
The longitudinal flanks 7, 8 abut each other via incorporated
contact projections 9 and are welded together, using projection
welding by which the longitudinal flanks 7, 8 are joined while
being held together under pressure applied by the upper mold 6. A
welding current is hereby introduced via electrode strips 10, 11
into the longitudinal flanks 7, 8 and thus into the contact
projections 9. The electrode strips 10, 11 are disposed in the
upper mold 6 adjacent to the longitudinal flanks 7, 8 and
configured as mirror images in relation to a longitudinal center
plane MLE between the longitudinal flanks 7, 8 being welded
together. Extending in the longitudinal center plane MLE is an
insulating layer 12 by which the electrode strips 10, 11 are
separated electrically from one another.
[0023] The electrode strips 10, 11 have contact surfaces 13 of a
contour conforming to the outer circumference of the tubular
profile R and forming part of the shaping contour of the upper mold
6.
[0024] The introduced welding current seeks its path to the other
electrode strip via the contact projections 9 between the
longitudinal flanks 7, 8. As a result, the longitudinal flanks 7, 8
are welded together in the area of the contact projections 9.
Depending on a toothed configuration of the sheet metal blank, the
tube that can be removed from the molding press 1 after disengaging
the upper mold may or may not be pressure-tight.
[0025] FIG. 3 shows three possible embodiments of sheet metal
blanks 2a, 2b, 2c. The sheet metal blank 2a, shown in FIG. 3a, has
contact projections 9 formed along each of the longitudinal flanks
7, 8 in opposite relationship. Only the contact projections 9 come
into contact during manufacture of the tubular profile R. The sheet
metal blank 2b, shown in FIG. 3b has contact projections 9 in
offset relationship so that the shaping of the blank 2b into a
tubular profile R results in an intermeshing engagement. In this
way, opposing contact projections 9 and longitudinal flanks 7, 8
are respectively joined. The sheet metal blank 2c, shown in FIG.
3c, has contact projections 9 only along one of the longitudinal
flanks 7, 8 (here longitudinal flank 7).
[0026] It will be appreciated by persons skilled in the art that
the geometry of the contact projections 9 as shown in FIGS. 3a to
3c has been randomly selected for illustrative purposes of
different options for positioning of the contact projections 9. Of
course, the configuration or geometry as well as the number of
contact projections 9 can be selected in any suitable manner that
is appropriate for the situation at hand. For example, the contact
projections 9 may also be of different width or height, or may be
arranged at even distances from one another or at varying distances
from one another.
[0027] While the invention has been illustrated and described in
connection with currently preferred embodiments shown and described
in detail, it is not intended to be limited to the details shown
since various modifications and structural changes may be made
without departing in any way from the spirit of the present
invention. The embodiments were chosen and described in order to
best explain the principles of the invention and practical
application to thereby enable a person skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *