Metal deforming – With use of control means energized in response to activator... – Metal deforming by use of roller or roller-like tool element
Reexamination Certificate
2001-02-28
2002-08-06
Tolan, Ed (Department: 3725)
Metal deforming
With use of control means energized in response to activator...
Metal deforming by use of roller or roller-like tool element
C072S011700, C073S862070, C073S862550
Reexamination Certificate
active
06427507
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an apparatus for measuring flatness of hot rolled strips in a rolling mill and, more particularly, to a contact-typed strip flatness measuring device which protects load sensors from heat or impact while controlling surface points of split rolls to move up and down.
(b) Description of the Related Art
Generally, metal strips produced through hot-rolling slabs should be kept to be even in flatness along the width thereof.
An automatic shape controller based on a shapemeter has been frequently employed for use in controlling the strip flatness during the hot rolling process.
FIG. 1
illustrates a rolling mill with such an automatic shape controller. In the automatic shape controller, a shapemeter
1
measures the shape change in the target hot rolled strip S through generating laser, and detects the strip flatness based on the measured shape change. The detected value of the strip flatness is input into a calculator
4
that calculates a control value. Then, depending upon the control value, a bender controlling unit
5
controls pressure of a bender
2
installed at the last stand, thereby controlling the strip flatness.
However, in the above strip flatness control technique, the strip flatness is basically controlled by taking the shape change of the hot rolled strip S as a criterion, and such a shape change largely differs from the practical value of strip flatness. Therefore, in such a technique, the strip flatness cannot be measured in a correct manner. Furthermore, when the frontal end portion of the hot rolled strip S transported over a roller table
3
is coiled around a coiler
6
, the hot rolled strip S is flattened under strain due to the difference in relative speeds between the last stand B and the coiler
6
. Accordingly, the shapemeter
1
cannot measure the strip flatness after the hot rolled strip S is coiled around the coiler
6
.
In order to solve such problems, a contact-type strip flatness measuring device has been suggested. In the device, the strip flatness is measured through detecting reduction in the hot rolled strip while directly contacting it.
Split looper rolles are arranged along the width of the hot rolled strip S, and a load sensor is attached to each split roll to detect load distribution of the hot rolled strip S. The detected load distribution is converted to a value of strip flatness, and makes feedback to a flatness control system, thereby controlling flatness across the hot rolled strip S.
When the load distribution signal issued from the strip flatness measuring device makes feedback to the flatness control system on line, uniform flatness can be obtained over the entire length of the hot rolled strip S.
However, such a contact-type load distribution measuring device should perform its intrinsic functions in poor working conditions such as high temperature, high humidity, and high vibration. Furthermore, it should ensure sufficient device stability and reliability, and detect the load distribution in a stable manner.
FIG. 2
illustrates a contact-type strip flatness measuring device installed at the Hoesch steel mill of German (Herman J. Kopineck, “Rolling of hot strips with controlled Tension and Flatness,” Hot strip profile and flatness seminar, Nov. 2-3, 1988, Pittsburg Pa.). As shown in
FIG. 2
, a load sensor
12
is provided at an end portion of a support
11
bearing a split roll
10
to detect the load applied to the split roll
10
, thereby measuring the strip flatness.
However, in such a device, since the difference in the maximum loads at tension and compression (hereinafter referred to as the “peak load”) is so great that the load sensor
12
is liable to be broken at repeated sensing operations, resulting in lowered precision and reduced device life span.
FIG. 3
illustrates another contact-type measuring device disclosed by George. F. Kelk in “New developments improve hot strip: Shapemeter-Looper and Shape Actimeter”, Iron and Steel Eng., August, 1986, pp. 48-56. As shown in
FIG. 3
, a compression-type load sensor
22
is provided at the bottom side of a shaft support
21
bearing a split roll
20
. In this structure, the tensile load applied to the split roll
20
does not influence the load sensor
22
so that the peak load can be reduced. However, since the strip flatness measuring device should play its intrinsic functions as a looper before it detects the load applied to the hot rolled strip S along the width thereof, the looper excessively moves up and down when uneveness in mass between the neighboring stands is present due to the great difference in relative speeds between the stands. In this case, the looper collides with an upper or lower damper so that strong impact is applied to the strip flatness measuring device, resulting in reduced life span of the load sensor
22
.
In this connection, a stopper
23
is provided at the strip flatness measuring device to prevent the load sensor
22
from being applied with an over-load.
However, when the maximum load is applied to the load sensor
22
, the compressed displacement is too small to make sufficient distance for preventing the load sensor
22
from being applied with the over-load. Thus, the mechanical means of protecting the load sensor
22
based on the stopper
23
has a limit in application in that whenever the device suffers slight deformation, the stopper
23
should be controlled each time.
Furthermore, the strip flatness measuring devices shown in
FIGS. 2 and 3
are interposed between the rolling stands, and the temperature of the hot rolled strips S amounts to 800 to 1200° C. In these conditions, the load sensor extremely sensitive to heat should be protected from the heat in a stable manner. If not, errors in meaurement are inevitably followed by.
For that reason, a cooling nozzle
24
is provided at the strip flatness measuring device to spray cooling water to the load sensor
22
. However, in case the spraying of the cooling water becomes poor due to breakage or alien materials, there is a problem in that the preparation for such a case is absent.
Furthermore, the hot rolled strips are differentiated in the load distribution depending upon their shapes. Therefore, when the strip flatness measuring device is used for a long time, the plural numbers of split rolls
10
and
20
are rubbed in a different manner so that they become differentiated in horizontal height, and errors in detection with respect to the load applied thereto are made.
In order to solve such a problem, the strip measuring device shown in
FIG. 2
is provided with a height control bolt
13
for controlling the tangent-movement thereof around a rotation shaft
14
, and the strip measuring device shown in
FIG. 3
with a wedge-shaped control member
25
for controlling the tangent-movement.
However, in such a case, as shown in
FIG. 4A
, deviation in rubbing dR between the split rolls
10
and
20
is made. Even though such a deviation in rubbing is controlled, as shown in
FIG. 4B
, deviance in controlling dR′ is present so that the load sensors
12
and
22
for detecting the load applied to the hot rolled strip S incorrectly detect such a load while making serious errors in the flatness detection signal. That is, in the one-directional control technique, the horizontal height of the measuring device cannot be controlled in a correct manner.
Meanwhile, in case the rubbed split rolls should be repaired or replaced by a new one, long repair or replacement time is required, lowering productivity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a strip flatness measuring device which can protect a load sensor from the external factors, and control the relative heights between split rolls while securing precesion in measurement.
This and other objects may be achieved by a strip flatness measuring device including a looper with a plurality of split rolls. The split rolls are assembled in a bracket such that each split roll can be separated from the bracket. A normal-mo
Hong Wan-Kee
Yi Joon-Jeong
Fish & Richardson P.C.
Pohang Iron & Steel Co. Ltd.
Tolan Ed
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