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Патент USA US3045536

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July 24, 1962
J. w. WALLACE ETAL
3,045,517
STRIP THICKNESS CONTROL APPARATUS
Filed May 29, 1957
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July 24, 1962
J. w. WALLACE ETAL
3,045,517
STRIP THICKNESS CONTROL APPARATUS
Filed May 29, 1957
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Mill or Strip Speed
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United States Patent 0
11
C6
3,045,517
Patented July 24, 1962
1
2
3,045,517
member 14 operative with a strip 16 of material. A
mill motor 18 is operative to control the movement
John W. Wallace, Orchard Park, and Robert E.. Hull,
well-known radiation gauge 20 is operative with a servo
STRIP THICKNESS CONTROL APPARATUS
. Eggertsville, N.Y., assignors to Westinghouse Electric
Corporation, East Pittsburgh, Pa., a corporation of
Pennsylvania
speed of the strip 16 through the rolling mill 10. A
motor 22 to vary the position of a control arm on a ?rst
potentiometer device 24 and to vary the position of a
control arm on a second potentiometer device 26 in ac
Filed May 29, 1957, Ser. No. 662,425
oordance with the actual thickness of the strip 16. In
this regard, the control arm of a potentiometer device 28
The present invention relates, in general, to control 10 and the control arm of a potentiometer device ‘30 are
apparatus for automatically controlling a predetermined
positioned in accordance with a predetermined desired
operation relative to a workpiece, and more particularly
strip thickness. The potentiometer devices 24 and 28
relates to control apparatus for controlling the thickness
are part of a ?rst control bridge circuit 29 operative to
or gauge of a moving strip of material, ‘such as metal.
provide a control signal to the ampli?er device 32 in
It is an object of the present invention to provide im 15 accordance with the error or deviation in the strip thick
proved motor control apparatus, and more particularly to
' ness relative to said predetermined desired strip thick
provide improved apparatus for controlling the operation
ness. Similarly, the potentiometer devices 26 and 30
of one or more motors of a strip rolling mill or the
are part of a second control bridge circuit 34 operative to
like, to thereby better control the gauge or thickness
provide a control signal to the magnetic ampli?er device
of the strip relative to a particular stand of the mill and 20 36 in accordance with said error or deviation of the
in accordance with the operating speed of the mill.
. thickness of the strip 16. The control signal. from the
It is a further object of the present invention to‘ pro
ampli?er device 32 is supplied to a mixer ampli?er device
vide improved control apparatus for controlling the rela
38 and supplied through a dead-zone device 40 to a mo
tive positions of a pair of work members operative with
tor control device 42 for controlling the operation of a
a moving workpiece to control a predetermined param
first screwdown motor 44- and a second screwdown mo
eter of said workpiece, such that a ?rst and faster acting
tor 46 as described in copending application, Serial No.
7 Claims. (Cl. 80-56)
control system is provided to correct for fast changes in
said parameter of the workpiece relative to a predeter
662,479, ?led May 29, 1957, by J. W. Wallace, R. E.
Hull and R. W. Moore, entitled “Position Control Appa
mined value for said parameter and a second and slower
ratus,” and assigned to the same assignee as the present
acting control ‘system is provided to correct for slow 30 application.
changes in said parameter of the workpiece relative to a
In this regard, a sample switching control device 48
predetermined value for said parameter.
is mechanically coupled to and operative in accordance
It is an additional object of the present invention to
provide improved control apparatus for a strip rolling
mill, which apparatus is provided with a gain dharacter~
with the operating speed of the mill motor 18 for con
trolling a sampling operation such that during the sample
On period the control signal from the ampli?er device
32 is applied to control the operation of the screwdown
istic and response time that varies in accordance with
the operating speed of the mill.
motors 44 and 46. During the sample Oil period, the
It is‘ another object of the present invention to provide
reset motor control device 50 is operative to sense the
improved control apparatus for a strip rolling mill which
output signal from the mixer ampli?er device and to con
apparatus is more stable in its operation by responding 40 trol the operation of a reset motor 52 for varying the
differently to a deviation or error in the operation of the
mill relative to a predetermined desired or reference op
eration and in accordance with and'as a function of the
operative speed of the mill, to thereby more accurately
control the operation of the rolling mill. *
It is a different object of the present invention to pro~
vide improved control apparatus for a strip rolling mill
which apparatus is operative to better control the strip
position of a contact arm on the potentiometer device 54
through the mechanical diiferential device 56 to balance
the settings of the control ‘arm on the bridge or servo
reset potentiometer device 54 relative to the setting of the
control arm on the reference potentiometer device 58,
such that a zero output or difference signal is applied to
the mixer ampli?er device 38 from the control bridge
circuit 59. Then the sample switching control device 48
is operative to provide another sample On period and
ner controlling the screwdown spacing of the roller mem 50 the control signal from the ampli?er device 32 is again
bers of any particular stand of the rolling mill.
operative to control the screwdown motors 44 and 46.
It is still another object of the present invention to
The screwdown motor 44 is operatively connected through
gauge or thickness by better and in a more stable man
provide improved control apparatus for a'st-rip rolling mill
a servo transmitting device 60 iand a servo receiving de
for better holding the screwdown spacing of a particular
vice 62 to apply a control signal through the mechanical
pair of roller members substantially constant or as may 55 diiferential device 56 relative to the now locked servo
be desired relative to a predetermined reference, and to
motor 52 for varying‘the position of the contact arm
thereby improve the operation of the rolling mill regard
on the bridge reset potentiometer device 54 in accordance
ing On gauge or desired thickness strip.
with the movement of the screwdown motor 44, such that
These and other objects and advantages of the present
invention will become apparent in view of the following
the control bridge 59 including the potentiometer device
54 and the potentiometer device 58 provides a control
signal, to cancel out the control signal received from the
ampli?er device 32, and corresponding to the movement
FIGURE 1 is a schematic showing of the control-appa
of the screwdown motors 44 and v46 to provide a full
ratus in accordance with the present invention;
’
FIG. 2 shows a curve chart illustrating the operation 65 correction for any error or deviation in the thickness of
the strip 16 as sensed by the radiation gauge device 20.
of the present control apparatus;
A
This operation is fully explained in said copending appli
‘FIG. 3 illustrates a modi?cation of the present control
description taken in conjunction ‘with the drawings,
wherein: ‘
‘
apparatus; and
cation Serial No. 662,479, ?led May 29, 1957, entitled
FIG. 4 shows a curve chart illustrating the operation
of the latter modi?cation.
In FIG. 1 there is shown a well-known rolling mill 10
including an upper roller member 12 and a lower roller
“Position Control Apparatus.” .
A pilot ‘generator 66 is operatively connected to the
mill‘motor 18 such that it is driven at a speed correspond
ing to the operating speed of the mill motor 18, and cor
3,045,517
4
responding to the movement speed of the strip 16, to
provide a control voltage to the center connection pro
vided on each of the potentiometer devices 68 and 70,
respectively, of the control bridge 34 to thereby vary the
In this regard, the control bridge circuit 34 within the
proportional control system is operative, in combination
with the gain control circuit including the recti?er bridge
72 and the impedance member, 74 operative with the di
circuit including a recti?er bridge device 72 and an im~
rect-current voltage source 76 and the impedance mem
ber 78, such that up to ‘a predetermined mill speed corre
sponding to a predetermined output voltage level from
pedance member 74 is connected in parallel with the con
trol bridge 34 and is operative with a direct-current
the pilot generator 66, the ‘bridge circuit 34 is operative to
provide for the proportional control system a ?rst gain
applied voltage across the control bridge 34 as a function
of the operating speed of the rolling mill 10. A control
voltage source 76 and an impedance member 78 such that 10 characteristic in accordance with the straight line curve
92. At a predetermined mill speed and the correspond
at a predetermined value of the output voltage of the
pilot generator 66, the value of the voltage supplied from
ing output voltage level from the pilot generator 66, the
shunt gain control circuit including the recti?er bridge 72
and the impedance member 74 becomes conductive such
current will ?ow through the impedance device 74. This
latter current ?owing through the impedance device 74 15 that the current ?owing through the latter impedance
member 74 is operative by changing the voltage applied
when added to the current already ?owing through the
across the control bridge '34 to change the gain character
impedance device 75 increases the voltage drop across
istic of the proportional control system including the
the latter impedance device 75 to thereby change the volt
ampli?er device 36 in accordance with the straight line
age applied across the control bridge 34. The control
across the impedance device 78 is overcome, such that a
signal received from between the control arms on the 20 curve 94, such that the desired gain characteristic as indi
respective potentiometer devices 26 and 30, and corre
sponding to the error or deviation in- the thickness of the
cated by the theoretical continuous curve 90 is thereby
empirically approximated and effected for the purpose
of controlling the screwdown motors 44 and 46 to provide
the desired correction relative to the thickness of the strip
strip 16 relative to a predetermined desired thickness, is
applied to the input control windings of a magnetic ampli
?er device 36. For values of the output voltage of said 25 member 16 as a function of the operating speed of the
rolling mill 10.
pilot generator 66 below a predetermined value as deter
The voltage ‘applied across the control bridge 34 and in
mined by the setting of the control arm on the impedance
accordance with the curve 92 is a linear function of strip
member 78, the proportional control system including
speed; the slope of the gain characteristic is changed above
the ampli?er device 36 has a ?rst gain characteristic lower
than the gain characteristic of the sampling control system 30 a predetermined strip speed and in accordance with the
curve 94. Thusly the gain of the closed loop proportional
including the ampli?er device 32. However, when the
acting regulation system is varied as a function of strip
output voltage from the pilot generator 66 exceeds the
or mill speed. If desired, as many additional shunt gain
predetermined value at which the branch circuit including
control circuits could be provided as required to approxi
the bridge 72 and the impedance member 74 becomes
conductive, then the proportional control circuit including 35 mate as closely as desired the actual shape of the theo—
retically desired gain versus speed curve 90.
the ampli?er device 36 has a second and still lower gain
In FIGURE 3 there is illustrated a gain control circuit
characteristic relative to said ?rst gain characteristic.
operative with the control bridge 34 and including a ?rst
The output control signal from the ampli?er device 36,
shunt path including impedance device 74 and a second
which is part of the proportional control system, is ap
plied to the input control windings 80 and '82 of a mag 40 shunt path including impedance device 79. The imped
ance device 78 is provided with a ?rst voltage setting, and
netic ampli?er device 84 provided within the motor con
the‘ impedance device 81 is provided with a second and
trol device 42. The control signal from the sampling
different voltage setting that may be larger than the latter
control system as received from the ampli?er device 32
?rst voltage setting. Thusly, and as shown in FIGURE
and passing through the mixer ampli?er device 38 and
the dead-zone device 40 is applied to a second pair of - 4, the curve 93 is obtained by a ?rst value of voltage be
ing applied across the control bridge '34 up to a ?rst pre
input control windings 86 and 88, such that the control
determined value of the output voltage from the pilot
signal received ‘from the proportional system including
generator 66; then the ?rst shunt path including imped
the ampli?er 36 is additive relative to the control signal
ance device 74 becomes conductive to apply a second and
received from the sampling control system including the
ampli?er device 32. The latter operation and the opera 50 lower value of voltage across the control bridge 34 and
tion of the motor control device 42 for controlling the
screwdown motors 44 and 46 are believed’ to- be fully
explained in the above-referenced copending application
the curve 95 is obtained.
Then at a second and greater
predetermined value of output voltage from the generator
66, the second shunt path becomes conductive to apply
a third and still lower value of voltage across the control
In FIG. 2, there is shown a curve chart illustrating the 55 bridge 34, and the curve 97 is obtained.
Although the present invention has been described with
desired gain characteristic as a function of mill speed for
a certain degree of particularity, it should be understood
the proportional system including the ampli?er device 36
that the present disclosure has been made only by way of
as shown in FIG. 1. The curve 90 illustrates the theo
example and that numerous changes in the details of con
retically desired gain characteristic for the closed loop
struction and the combination and arrangement of parts
proportional regulating system, and the ?rst straight line
may be resorted to without departing from the scope and
92 illustrates the gain characteristic obtained by the opera
spirit of the present invention.
tion of the control bridge circuit 34 when the output volt
We claim as our invention:
age of the pilot generator 66 is below a predetermined
1. 'In control apparatus for a strip rolling mill including
value corresponding to a preretermined movement speed
Serial No. 662,479, ?led May 29, 1957.
of the strip 16-and a predetermined operating speed of the
mill 10 and at which it is desired to lower the gain char
a pair of roller members operative with a moving strip
for controlling the thickness of said strip, with said mill
acteristic of the proportional system including the ampli~
further including a motor operative with at least one of
?er device 36. The line 94 illustrates the latter lowered
said roller members to control the spacing between said
roller members, the combination with said rolling mill of
a strip thickness sensing device operative to provide a ?rst
gain characteristic obtained when the parallel connected
conductive path including the recti?er bridge 72 and the
impedance member 74 becomes conductive by virtue of
the output voltage of the pilot generator 66 exceeding the
voltage drop across the impedance device 78 as determined
by the setting of the contact arm of the latter impedance
device 78.
75
control signal that varies as a function of the thickness of
said strip, a control device including signal value sensing
means and ‘being responsive‘ to said ?rst control signal and
operative with said motor for controlling the spacing be
tween said roller members in accordance with the varia
3,045,517
5
6
.
tions of said ?rst control signal, 1a strip speed sensing de
control signal, a workpiece movement speed sensing de
vice operative to provide a second control signal that var
ies as a function of the mov-t ment speed of said strip, with
said signal value sensing means of the control device being
responsive to said second control signal for e?ecting a
varies as a function of the movement speed of said work
?rst gain characteristic for strip speeds below a predeter
mined value and a second gain characteristic for strip
speeds above said predetermined value to cooperate with
said ?rst control signal for controlling the spacing between
said roller members.
2. A control apparatus for a strip rolling mill including
a pair of roller members operative with a moving strip
for controlling the thickness of said strip, with said mill
vice operative to provide a second control signal that
piece, with said control device being responsive to said
second control signal for changing the response of said
control device to said ?rst control signal in accordance
with the variations of said second control signal, with
said control device including a control circuit operative
with said second control signal to provide a ?rst response
10 characteristic ‘for values of said second control signal
below a predetermined value and to provide a second and.
‘lower response characteristic for values of said second
control signal above said predetermined value.
5. In control apparatus for a strip rolling mill including
further including a motor operative with at least one of
said roller members to control the spacing between said 15 i a pair of roller members operative with a moving strip
for controlling the thickness of said strip, with said mill
roller members, the combination with said rolling mill
of a strip thickness sensing device operative to provide a
further including a motor operative ‘with at least one of
?rst control signal that varies as a function of the thick—
said roller members to control the spacing between said
ness of said strip, a ?rst control device operative with
roller members, the combination with said rolling mill of
said motor and responsive to said ?rst control signal 20 a strip thickness sensing device operative to provide a
for controlling the spacing between said roller members
?rst control signal that varies as a function of the thick
ness of said strip, a control device responsive to said
in accordance with the variations of said ?rst control
?rst control signal and operative with said motor for
signal, a second control device operative with said motor
and responsive to said ?rst control signal for controlling
controlling the spacing between said roller members in
the spacing between said roller members in accordance 25 accordance with the variations of said ?rst control sig—
nal, a strip speed sensing device operative to provide a
with the variations of said ?rst control signal, with said
second control signal that varies as a function of the
second control device having a lower gain characteristic
movement speed of said strip, with said control device
than said ?rst control device, and a strip speed sensing
being responsive to said second control signal for eifecting
device operative to provide a second control signal that
varies as a function of the movement speed of said strip,v 30 a ?rst response characteristic for strip speeds below a
predetermined value and ,a second response character
with said second control device being responsive to said
istic ‘for strip speeds above said predetermined value rela-'
second control signal for elfecting a ?rst gain character
tive to the "response to said ?rst control signal for con
istic for strip speeds below a predetermined value and a
trolling the spacing between said roller members, with
second gain characteristic for strip speeds above said pre
said control device including a control circuit operative
determined value.
with said control device for controlling the response
3. In control apparatus 'for a strip rolling mill includ
characteristic of said control device, with said control
ing a pair of roller members operative with a moving
circuit having at least a ?rst conductive path for values
strip for controlling the thickness of said strip, with
of said second control signal below a predetermined
said mill further including a motor operative with at
least one of said roller members to control the spacing 40 value and providmg at least a pair of parallel connected
conductive paths ‘for values of said control signal above
between said roller members, the combination with said
rolling mill of a strip thickness sensing device operative
said predetermined value.
to provide a ?rst control signal that varies as a function
of the thickness of said strip, a control device operative
6-. In control apparatus for a strip rolling mill inc-lud
ing a pair of roller members operative with a moving
vide a second control signal that varies as a function of
rolling mill of a strip thickness sensing device operative
with said motor and responsive to said ?rst control sig 45 strip [for controlling the thickness of said strip, with
said mill ‘further including a motor operative with at
nal for controlling the spacing between said roller mem
least one of said roller members to control the spacing be
bers in accordance with the variations of said ?rst con
tween said roller members, the combination with said
trol signal, a strip speed sensing device operative to pro
the movement speed of said strip, with said control de 50 to provide a ?rst control signal that varies as a function
of the thickness of said strip, a control device responsive
vice being responsive to said second control signal for
to said ?rst control signal and operative with said motor
changing in accordance with the variations of said second
for controlling the spacing between said roller members
control signal the response of said control device to said
in accordance with the variations of said ?rst control
?rst control signal, with said control device including a
control circuit having at least ‘?rst and second current 55 signal, a strip speed sensing device operative to provide a
second control signal that varies as a ‘function of the
paths, with one of said current paths being non-conduc
movement speed of said strip, with said control device
tive until said second control signal reaches a predeter
being responsive to said second control signal for e?ect
mined value and then being conductive to thereby change
ing a ?rst response characteristic ‘for strip speeds below a
the response of said control device to said ?rst control
signal.
predetermined value and a second response characteristic
for strip speeds above said predetermined value relative
to the response to said ?rst control signal for controlling
the, spacing between said roller members, with said con
trol device including a control circuit for controlling the
mined operation relative to said workpiece, with said
machine device including a motor operatively connected 65 response characteristic of said control device, with said
control circuit having at least a ?rst conductive path for
' to at least one of said work members for controlling a
values of said control signal below a predetermined value
predetermined relationship between said Work members,
and having at least a pair of parallel connected conduc
the combination with said machine device of a work
tive paths for values of said control signal above said
piece parameter sensing device operative with said work
predetermined value.
piece for providing a ?rst control signal that varies as a
70
7. In control apparatus for a strip rolling mill includ
function of the value of a predetermined parameter of
ing
a pair of roller members operative with a moving
said workpiece, a control device operative with said
strip rfor controlling the thickness of said strip, with saidv
motor and responsive to said ?rst control signal for con
mil-l further including a motor operative with at least
trolling said predetermined relationship between said work
one of said roller members to control the spacing be
members'in accordance with the variations of said ?rst 75 tween said roller members, the combination with said
4. In control ‘apparatus for a machine device includ
ing a ?rst work member and a second work member opera
tive with a moving workpiece for performing a predeter
3,045,517
8
6
rolling mill of a strip thickness sensing device operative
to provide a ?rst control signal that varies as a function
of the thickness of said strip, a ?rst control device oper
ative to provide a parallel shunt path relative to said con
trol bridge circuit for values of said second control sig
nal above a predetermined value.
ative with said motor and responsive to said ?rst control
References Cited in the ?le of this‘ patent
UNITED STATES PATENTS
signal \for controlling the spacing between said roller U!
members in accordance with the variations of said ?rst
control signal, a second control device operative with said
motor and responsive to said ?rst control signal for con
trolling the spacing betWeen- said roller members in ac
cordance with the variations of said ?rst control signal, 10
with said second control device having a lower gain char
acteristic than said ?rst control device, and a strip speed
2,264,095
2,687,052
2,708,254
2,735,051
Mohler _____________ __
Zeitlin ______________ __
Macaulay et al. ______ __
Gille _______________ __
2,851,911
Hessenberg __________ .._ Sept. 16, 1958
533,162
Great Britain _________ __ Feb. 7, 1941
said strip, with said second control device being respon 15
25,
24,
10,
14,
1941
1954
1955
1956
FOREIGN PATENTS
sensing device operative to provide a second control sig
nal that varies as a ‘function of the movement speed of
Nov.
Aug.
May
Feb.
sive to said second control signal ‘for effecting a ?rst
OTHER REFERENCES
gain characteristic for strip speeds below a predetermined
value and a second gain characteristic for strip speeds
above said predetermined value, with said second control
device including a control bridge circuit and being oper
“Rolling Slabs Into Strip Steel” (Vossberg), Control
Engineering, September 1956 (pages 116 and 117 relied
on).
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