U.S. patent application number 13/031635 was filed with the patent office on 2012-06-07 for method of bending a metal plate.
Invention is credited to Uwe Feldmann, Manfred Kolbe.
Application Number | 20120137748 13/031635 |
Document ID | / |
Family ID | 43923718 |
Filed Date | 2012-06-07 |
United States Patent
Application |
20120137748 |
Kind Code |
A1 |
Feldmann; Uwe ; et
al. |
June 7, 2012 |
METHOD OF BENDING A METAL PLATE
Abstract
A plate workpiece having an edge is bent with a press having a
stationary upper die with a lower face and a vertically and
horizontally movable lower die with an upper face. With the upper
face of the lower die spaced below the lower face of the upper die,
the workpiece is fitted between the dies such that the edge of the
plate bears in a horizontal direction on the upper face of the
lower die and an upper face of the plate bears upward on a portion
of the lower face of the upper die. Then the lower die is moved
vertically upward toward the upper die at a predetermined vertical
rate while the lower die is shifted horizontally synchronously in
the direction at a predetermined horizontal rate such that the
plate edge engaging the lower-die upper face does not shift there
along during upward movement.
Inventors: |
Feldmann; Uwe;
(Rommerskirchen, DE) ; Kolbe; Manfred;
(Moenchengladbach, DE) |
Family ID: |
43923718 |
Appl. No.: |
13/031635 |
Filed: |
February 22, 2011 |
Current U.S.
Class: |
72/379.2 |
Current CPC
Class: |
B21D 5/015 20130101;
B21D 19/08 20130101 |
Class at
Publication: |
72/379.2 |
International
Class: |
B21D 5/04 20060101
B21D005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2010 |
DE |
102010008894.3 |
Claims
1. A method of deforming a plate workpiece having an edge with a
bending press having a stationary upper die with a lower face and a
vertically and horizontally movable lower die with an upper face,
the method comprising the steps of: with the upper face of the
lower die spaced below the lower face of the upper die, fitting the
workpiece between the dies such that the edge of the plate bears in
a horizontal direction on the upper face of the lower die and an
upper face of the plate bears upward on a portion of the lower face
of the upper die; and synchronously moving the lower die vertically
upward toward the upper die at a predetermined vertical rate while
shifting the lower die horizontally in the direction at a
predetermined horizontal rate such that the plate edge engaging the
upper face does not shift along the upper face during upward
movement.
2. The method defined in claim 1 wherein the upper and lower faces
are complementary and the lower die is shifted upward until the
workpiece is held in surface contact with both faces.
3. The method defined in claim 2 further comprising the step of
holding the plate between the faces after the workpiece is in
surface contact with both faces.
4. The method defined in claim 1 wherein the lower face is
downwardly convex and the upper face is upwardly concave.
5. The method defined in claim 4 wherein the curvature of the lower
face is not constant.
6. The method defined in claim 4 wherein the curvature of the upper
face is not constant.
7. The method defined in claim 1, further comprising the step of
clamping the plate against horizontal movement after the edge
contacts the upper face and during upward movement of the lower
die.
8. The method defined in claim 1 wherein the press includes a
controller that sets the rates in accordance with a stored
correlation between the vertical rate and the horizontal rate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to method of bending a metal
plate. More particularly this invention concerns such a method for
making a workpiece from which welded pipe can be made.
BRIEF DESCRIPTION OF THE DRAWING
[0002] The prior art and the invention are described below in more
detail with reference to the drawing in which:
[0003] FIG. 1 illustrates a prior-art method;
[0004] FIG. 2 illustrates another prior-art method; and
[0005] FIG. 3 illustrates the method of the present invention
BACKGROUND OF THE INVENTION
[0006] In order to make welded pipe, a piece of flat normally steel
plate is first bent into a shape of U- or C-section. Then the two
longitudinally extending plate edges are pressed together and
welded, forming a closed tube. The first step therefore involves
bending up both the edges of the starting workpiece that has a pair
of opposite and parallel planar faces.
[0007] This initial bending is typically done in a bending or
crimping press having a stationary upper die with a lower face
whose shape is roughly that of a quarter cylinder, corresponding to
the desired final shape of the respective workpiece edge after
pressing. The press also has a lower die with an upper face and
some sort of actuator means for at least vertically displacing the
lower die upward.
[0008] For the bending operation the workpiece edge is positioned
between the die faces and the lower die is raised. This action
deforms the edge into an upwardly curving shape. Obviously, both
longitudinal edges of the plate are thus deformed to the desired U-
or C-section, and then the workpiece is run through several rollers
that further deform it into the desired closed circular shape.
[0009] One problem with most prior-art systems as described below
is that the plate edges are damaged and/or deformed to have an edge
burr that interferes with the subsequent welding process and that
also produces a lump at the weld seam.
[0010] To remedy this, U.S. Pat. No. 7,735,348 describes a method
where at the start of the crimping process the lower face of the
plate contacting working face of the lower die comes to rest flatly
against an abutment that can rock or pivot. This flat contact is
maintained during the entire crimping process in that as the lower
die moves straight upward, the abutment pivots and the plate
workpiece slides on the abutment in face, not line, contact.
[0011] An approach comparable to this is known from GB 1,537,055
and shown in FIG. 1. Here, a crimping press 2 is used to deform a
flat plate workpiece 1 from an initial basically planar shape, that
is with upper and lower faces lying in parallel horizontal planes,
shown in solid lines to a shape with one edge upwardly curved into
a part-cylindrical shape as shown in broken lines. This type of
bending is applied to both longitudinal edges of the workpiece 1 so
that it can be formed subsequently into a welded or open seam pipe.
The press 2 has an upper die 3 and an lower die 4 respectively
having a lower face 7 and an upper face 6, shaped as complementary
part cylinders centered on respective parallel horizontal axes. The
upper die 3 is stationary and the lower die 4 is shiftable
vertically in a straight line as shown at H.sub.V.
[0012] Initially the plate 1 is fitted between the dies 3 and 4
with the lower die 4 in the solid-line lower position such that the
one lower longitudinal edge of the workpiece contacts the upper
face 6 of the lower die 4 at line or position 5. Workpiece advance
in direction D is then stopped and the lower die 4 is raised as
shown by H.sub.V to the broken-line upper position. During this
movement the workpiece corner slides on the face 6 of the lower die
4 along path s from position 5 to position 5'. This action forms a
burr on the lower longitudinal edge of the workpiece 1.
[0013] What is thus effected in the illustrated solution is a
bending stroke without horizontal motion and this results in
relative motion between the plate 2 and the lower die 4 when there
is high face pressure between the lower die 4 and the plate
workpiece 2.
[0014] FIG. 2 shows another previously known solution for crimping
plate 1 in a crimping press 2 known from DE 10 2007 012 316. Here
the difference from the solution of FIG. 1 consists in the fact
that the lower die has a face 6' that, while part-cylindrical, is
not complementary to the face 7 but instead is part-cylindrically
convex. Here also, a horizontal vector H.sub.H is superimposed on
the vertical upward vector H.sub.V. This is aimed at minimizing
ridge formation. Consequently, the result again is that during the
intended crimping of the plate the starting contact position 5
shifts in the course of the crimping operation along the face 6 of
the lower die 4 to position 5'. The displacement path s is again
along an arc.
[0015] What thus occurs in the solution of FIG. 2 is a bending
stroke with superimposed horizontal motion by the lower die 4, and
this does in fact enable the face pressure to be reduced. A
disadvantageous aspect, however, is that there is a high relative
motion between the end edge of the plate and the face of the lower
die. The workpiece 2 is left with a hard-to-weld edge.
[0016] A similar solution is disclosed in EP 1 958 712.
[0017] What cannot be accomplished by any of the previously known
solutions in sufficiently reliable fashion is for the bent edge of
the strip to have the desired shape. Instead, a burr or flash
formation can result when high stresses occur in the edge region of
the plate during the crimping process and yield processes
result.
OBJECTS OF THE INVENTION
[0018] It is therefore an object of the present invention to
provide an improved method of bending a metal PLATE.
[0019] Another object is the provision of such an improved method
of bending a metal PLATE that overcomes the above-given
disadvantages, in particular that largely avoids any burr formation
at the workpiece edge, leaving it nearly perfectly square and
smooth.
SUMMARY OF THE INVENTION
[0020] A plate workpiece having an edge is bent with a press having
a stationary upper die with a lower face and a vertically and
horizontally movable lower die with an upper face. With the is
upper face of the lower die spaced below the lower face of the
upper die, the workpiece is fitted between the dies such that the
edge of the plate bears in a horizontal direction on the upper face
of the lower die and an upper face of the plate bears upward on a
portion of the lower face of the upper die. Then according to the
invention the lower die is moved vertically upward toward the upper
die at a predetermined vertical rate while the lower die is shifted
horizontally synchronously in the direction at a predetermined
horizontal rate such that the plate edge engaging the upper face
does not shift along the upper face during upward movement.
[0021] In practice this is simultaneously done to both of the
longitudinal edges of the workpiece. Subsequently the workpiece,
which has been bent into a C- or U-shape, is fed to a plurality of
roller benders and a welder that form it into a closed circular
shape and weld the two longitudinal edges together.
[0022] The horizontal motion by the lower die is preferably
effected by at least one hydraulic actuator. A piston-cylinder
system can be advantageously employed as the hydraulic
actuator.
[0023] The face of the lower die contacting the plate is usually of
concave form. In one development, provision is made that the
curvature of the face of the lower die is not constant, which
aspect provides the ability to use different regions of the die for
different curvatures of the plate.
[0024] The face of the upper die contacting the plate is usually of
convex form; here again, provision can be made whereby the
curvature of the face of the upper die is not constant.
[0025] During crimping, the plate is preferably fixed in the
lowermost region of the upper die relative to this die.
[0026] Finally, a control means working with or without feedback
controls the vertical and horizontal movement of the lower die in
such a way that a specified functional correlation exists between
vertical and horizontal motion.
[0027] With the proposed solution a plate strip required to create
an open seam pipe, in particular, a large-diameter pipe, can be
bent in an ideal fashion into a cylindrical shape, the joint of the
plate faces, in particular, can be formed optimally, that is free
if any flash or burrs.
[0028] This is accomplished in that any sliding motion is prevented
after of the initial contact of the plate on the face of the lower
die. Thus, no material that is under high mechanical stress during
the crimping process is drawn out and no burr is created.
[0029] Advantageously, wear on the face of the lower die is also
significantly reduced by the proposed procedure since no relative
motion results at the line contact between the face and the
plate.
[0030] The welding operation, by which the joint points of the
plate are joined, can thus be implemented under optimal conditions
and is not hampered by a burr.
SPECIFIC DESCRIPTION
[0031] As seen in FIG. 3, where elements identical to FIGS. 1 and 2
have the same reference numerals, a horizontal vector H.sub.H of
movement is superimposed on the vertical movement vector H.sub.V of
the lower die 4 when the plate 1 is bent. Here the faces 5 and 6
are not part-cylindrical, but their curvature is not constant, that
is their radius of curvature changes from one angular end to the
other.
[0032] More particularly this horizontal motion H.sub.H is
synchronized to the vertical motion H.sub.V such that the contact
region 5 determined at the start of the bending operation between
lower die 4 and plate 1 remains the contact region between the
lower die 4 and the plate 1 during the entire bending operation,
that is the plate 1 does not slide on the face 6 during the bending
operation. In and between the lower solid-line position of the
lower die 4 and the upper broken-line position, the contact region
5 is stationary on the face 6 of the lower die 4. As a result,
there is no significant deformation of the material at the edge of
the plate. Burr formation is thus reliably prevented.
[0033] A control means or controller 9 is provided to coordinate
the vertical lifting motion H.sub.V with the horizontal motion
H.sub.H. This controller 9 is linked to a vertical actuator 10 that
effects the vertical lifting motion H.sub.V, and a horizontal
actuator 11 that effects the horizontal motion H.sub.H. An
algorithm or curve path is stored in the controller 9 that
specifies a corresponding horizontal motion for each point of the
vertical lifting motion. This can then be operated in a closed-loop
or feedback-type control system using appropriate horizontal- and
vertical-movement sensors 12 and 13 connected to the controller
9.
[0034] As a result, there is no shifting of the contact line 5 as
in FIGS. 1 and 2.
* * * * *