SYSTEM AND PROCESS FOR CONTROLLING THE FORMATION OF SHEET MATERIAL

SYSTEME ET PROCEDE DE CONTROLE DE FORMATION DE MATERIAU EN FEUILLES

English Abstract

ABSTRACT OF THE DISCLOSURE
A process is provided for controlling a thickness regulating
member such as a slice lip coupled to slice rods. The process includes
determining the desired configuration of the slice lip and determining the
required slice rod movements based upon physical characteristics of the
slice lip and the slice rods.

Claims

WHAT IS CLAIMED IS:
1. A process for controlling the configuration of a
thickness-regulating member which is coupled to a plurality
of actuators, the process comprising:
(a) determining the desired configuration of the
thickness-regulating member;
(b) determining the actuator movements required
to substantially obtain the desired con-
figuration of the thickness-regulating
member according to the following equation:
Z =<IMG>
where:
Z = required actuator movements;
Y = required displacements of the thickness-
regulating member at each actuator;
E = modulus of elasticity of the thickness-
regulating member;
I = cross-sectional moment of inertia of the
thickness-regulating member;
k = spring constant of an actuator;
l = distance between actuators;
[A] = a first predetermined matrix;
[J] = identity matrix;
[Ra] = a second predetermined matrix;
wherein said first and second predetermined
matrices are determined by modeling a thickness-
regulating member and actuator system as an
elastic system, without basing the determination
on any of the following parameters; spring
constants of the actuators, elastic modulus of
the thickness-regulating member, and cross-
- Page 1 of claims -

sectional moment of inertia of the thickness-
regulating member; and,
(c) controlling the actuators based upon the
required actuator movements.
2. A process according to claim 1 wherein,
[A] = [Pa][Da] where:
Pa =
<IMG>
Da =
<IMG>
n = number of actuators.
3. A process according to claim 1 wherein:
Ra =
<IMG>
4. A process for controlling the configuration of a
thickness-regulating member which is coupled to a plurality
of actuators, the process comprising:
(a) determining at least one matrix by modeling a
thickness-regulating member and actuator system
as an elastic system, said determination being
made without basing the determination on any of
the following parameters; spring constants of the
- Page 2 of claims -

actuators, elastic modulus of the thickness-
regulating member, and cross sectional moment of
inertia of the thickness-regulating member;
(b) determining the desired configuration of the
thickness-regulating member;
(c) determining actuator movements required to
substantially obtain the desired configuration of
the thickness-regulating member based upon the
determined at least one matrix; and
(d) controlling the actuators based upon the required
movements.
5. A process according to claim 4 wherein the thickness-
regulating member is a slice lip.
-page 3 of claims -
11

Description

1303706
SYSTEM AND PROCESS FOR CONTROLLING
THE FOR~ATION OF A SHEET MATERIAL
BACKGROUND OF THE INVENTION
..
The Field of The Invention
The present invention concerns a system and process for controlling
the formation o~ sheet materials such as paper. `~
State of the Art
Various sheet materials are manufactured by causing the material in a
fluid state to flow in a controlled fashion onto a conveyer or the like.
For example, sheet plastic is often manufactured by extruding heated plas-
tic through a die onto a conveyer belt. Likewise~ paper is often manufac-
tured by causing a slurry of paper pulp to flow from a headbox onto a mov-
ing wire. In the manufacture of sheet materials, a thickness-regulating
member is norma11y used to insure that the thickness of the sheet is sub-
stantially uniform both in the direction in which the sheet travels and in
the direction perpendicular thereto. In the case of paper, the thickness
regulating member is called a slice lip and in the case of plastics, the
thickness regulating member can be called a die. In either case, the
position of the thickness-regulating member is controlled by actuators,
which in the case of paper manufacturing include slice rods.
U. S. Patent 3,413,1~2 teaches a system for controlling a thickness
regulating member used in the manufacture of sheet products. According to
the patent, a water slurry of fibrous paper stock is fed into a headbox,
and the slurry then flows through a slice lip opening slot to be deposited
in a continuous web onto a Fourdrinier wire which is continuous1y moving
in a direction away from the headbox. The position of the slice lip is
controlled by a plurality of actuators connected to the slice lip and to
the headbox and spaced apart from one another along the length of the
slice lip.

1303706
Further, according to the patent, the paper slllrry dries as it
travels along the Fourdriner wire and thereafter the paper web is fed
between press rolls for removal of additional moisture. The web is tnen
fed through a drier section, and the finished paper web issues fr~m the
drier. After the dried paper leaves the drier7 a conventional basis
weight measuring gauge including a source o~ nuclear radiation is used to
measure the thickness of the web across the width thereof. Information
from the measuring gauge is transmitted to a control system which in turn
controls the slice actuators to maintain the thickness of the paper being
produced according to a predetermined scheme.
One of the shortcomings of the system taught in the patent is that
the physical characteristics of the slice lip and the actuators are nct
explicitly considered. It is believed that this leads to certain inaccur-
acies in the operation of the system.
.
Summary and Objects of the Invention.
The inv~ntion is directed to a process for controlling the
configuration of a thickness-regulating member which is coupled
to a plurality'of actuators, the process comprising: (a) deter-
mining the desired configuration of the thickness-regulating
member; (b) determining the actuator movements required to
substantially obtain the desired configuration of thè thickness-
regulating member based upon physical characteristics of the
thickness-regulating member and'of the actuators; and (c) control-
ling the actuators based upon the required'movements.
An object of the present invention is to provide a system and process
for controlling a thickness regulating member wherein the physical charac-
teristics of the thickness regulating member are taken into consideration
prior to using the system to control the manufacture of a sheet material.
-Further objects and advantages of the present invention can be ascer-
tained by reference to the specification and drawin~s which are offered by
way of example and not in limitation of the invention which is defined by
the claims and equivalents thereto.

1303'706
Brief Description of the Drawings
Figure 1 is a schematic illustration of a paper making system accord-
ing to one embodiment of the present invention.
Figure 2 is an expanded view of one part of the system shown in
Figure 1.
Figure 3 is a graph illustrating one mode of operation of the present
embodiment.

1303706
DETAILED DESCRIPT~ON OF THE PREFERRED EMBODIME~T
As shown in Fi~ure 1, the present embodiment includes a headbox 10 to
contain paper pulp. The headbox 10 includes a plurality o~ control mem-
bers 12 coupled to a slice lip 14. Below the slice lip 14 is located the
slice opening 16 through which the paper pulp is distributed onto a moving
Fourdrinier wire 20. In accordance with conventional paper making pro-
cesses the sheet of paper 22 is processed in a drier 24 and then rolled
for shipment onto a reel 26. A scanner 30 is positioned across the sheet
22 near the reel 26. The scanner 30 is conventional and will not be des-
cribed in detail herein. The scanner has two gauges, a basis weight gauge
32 and a moisture gauge 34, which move back and forth across the movin~
sheet and simultaneously measure the basis weight and moisture o~ the
sheet. The gauges 32 and 34 produce electrical sign~ls corresponding to
the measured property of the sheet, and the electrical signals are trans-
mitted to a controller 36. The controller 36 includes a computer to pro-
cess information received from the gauges 32 and 34, and the controller
also inoludes means coupled to the control members 12 to control the
operation thereof.
Figure 2 shows details of the control members 12. Each member 12
includes a support tube 40 which is connected to the side of the headb~x
10 by mounting brackets 42. A screw jack 44 is coupled to the upper end
of the support tube 40, and a knob 4~ is coupled to the upper end of the
screw 44. To the lower end of the screw jack 44 is coupled a slice rod or
actuator 45 which includes a heating element, not shown. The slice rod 45
is hollow, and the heating element extends substantially the full length
of the interior of slice rod 45. The heating element is a pair of elec-
rically insulated wires so that when current is applied the wires heat
thereby heating the slice rod. A wire pair 51 is coupled to the heating
element and extends out of the tube 40 for coupling to a power source.
Each connector 50 has a threaded hole, not shown, formed therein to
accept a slice rod 45, and the rods 45 are threaded at their lo~er ends to
permit the rods to be screwed into the connectors 50. Each conn2ctor 50
has a mounting member 54 formed on its lower end to cooperate with the
slice lip 14.

1~03706
~ hen electric current is app7ied to the wires 51, the heating element
is heated thus heating the rod 45 so that it expands and becomes longer,
thus forcing the slice lip 14 downward. On the other hand, when no
current is applied the heating element cools and the rod 45 contracts.
For further discussion of the control members 12, see U. S. Patent
4,406,740 titled "Apparatus for Effecting the Fine Adjustment of the Lip
of a Headbox of a Paper Making Machine" assigned to Chleq Frote et Cie.
- The slice lip 14 extends the length of the headbox and has a substan-
tially flat side which fits flush against the-front wall of the headbox
1~. The opposing side of the slice lip 14 is curved and has a notch 56 to
cooperate with the mounting member 54 so that vertical movements of 2 con-
nector 50 results in corresponding vertical ~ovement of the portion of the
slice lip to which the connector is coupled. Behind the slice lip 14 the
front face of the headbox 10 has a slice opening 16 to permit pulp to flow
from the headbox onto the wire above a forming board 60. Thus it can be
seen that the shape of the lower edge of the slice lip 14 determines the
configuration of the flow of pulp from the slice opening 16. That is, if
a portion of the slice lip 14 is raised, more pulp will be allowed to flow
through the slice opPnin~ 16, and if a portion of the slice lip 14 is
lowered toward the forming board 60, the slice opening will be correspond-
ingly reduced in height there~y restricting the flow of pulp through the
slice opening. Thus, it can be seen that the operation of the slice rods
or actuators 45 can be used to control the basis weight of the paper
measured by the gau~e 32.
We have found that control of the actuators can advantageously be
based upon certain information which is predetermined prior to operation
of the system.
Prior to operation of the system, two matrices are determined.
Ra = . . . . . ~
1-2 1 0 . . . O
0 1-2 1 0 . . O
........
. . . . . . . .
O . . . 0 1-2 1
. O . . . . . . O
tA3 = tPa}tDd~ where:
_5

1~037(~6
Pa= 1 00 .... O .
1 4 1 0 0
00. . . 14i
~ O . . . . O O
~a = 0 1 ~ 3 . . . (n-l)
0 0 1 2 3 . . (n-2)
0 0 i
11..,.. 1
n = the number of actuators coupled to the slice lip.
Each of the above matrices is derived by modelling the slice lip as
an elastic b-eam supported by elastic supports and loaded at the actuators.
Such systems are well analyzed in mechanical and civil engineering disci-
plines, and various approximations are well known. For the particular
application for headbox slice lip control we have chosen an approximation
which is to consider the slice lip as a slender elastic beam, and its de-
flections small with respect to its other dimensions This allows approx-
imation of the radius of curvature at any point of the be~m as l/R - y",
where y is displacement, and allows expression of the relationship between
the moment, M, and the curvature as M = E I y", where E is the modulus of
elasticity and I is the moment of inertia. In practice, the slice rods 4
are relatively thin and flexible. This allows for a reasonable assumption
that the rods apply forces only, and the torques exerted by the rods are
negligible. The behavior of the slice lip segments between two adjacent
actuators can be expressed in terms of moments acting at the two ends of
each segment. The neighboring ends of two adjacent segments must assure
the continuity of the slice lip, and hence the positions and s10pes at the
neighboring ends must equal each other. This way one can express (n-~)
rela~ions~ where (n) is the number of rods along the slice lip and where 1
is the distance between rods, as,
ljMj + 2 (lj + lj+l) Mj+1 + ~ Mi+2
= (6 E I /lj + lj+~ +l yj-(li + lj+l j)Yj+1 i i+2
--6--

- 1303'706
The moments arise primarily from the forces exerted by the rods and can be
expressed in (n-l) equations as,
Mj-Mj 1 = llF1 + 12F2 + +1i-lFi-l
In equilibrium, all forces ac~in3 on the slice lip must add up to zero,expressed as,
Fl + F2 ~ + F = O
n
Since the forces emerge due to the loading of the rods, causing them todeform practically in an elastic manner,
Fj = kj ~zj- yj)
The collection of these equations can be solved to express the necessary
displacement of the rods (z;) to result in a slice lip shape (yj).
Thus it can be seen that the matrices Ra~ A, Pa and Da are
based upon the assumptions of equal spacing between the rods; all force on
the slice lip is acting a~ the rods; and all rods are identical. In the
event that any or all of these assumptions is not satisfied, different
matrices could be computed. However, as a practical matter, we have found
that the above identified matrices would be applicable to most practical
cases.
Once matrices A and Ra have been determined then certain physical
parameters of the system must be determined also. In particular9 the
following must be determined based upon a physical experiments or informa-
tion from the manufacturer of the equipment.
E, the modulus of elasticity of the slice lip;
I, the cross sectional moment of inertia of the slice lip;
k, the spring constant of the slice rod 45;
1, the distance between slice rods.
Once this information has been determined or computed, the-informa-
tion is fed into the computer of the controller 36. Then the system can
be installed in the field and operated according to the following equation:
~ = ~A] 1 ~ ~Ra~ ~ ~J]

1303706
In this equation, ~ equals a vector of the required slice rod move-
ments ~ equals a vector of required displacements of the thickness regula-
tor member at each actuator, J equals the identity matrix and the other
variables are as discussed above. In more general terms, the required
slice rod movements are a function of the required displacements and
physical paraneters of the system, i.e.:
= f(Y, E, I, k, 1)
In some circumstances, it may not be convenient to determine the
parameters E, I, k based on data provided by the manufacturer of the hard-
ware. In such cases, an operator in the field can utilize the following
procedure to develop a parameter c, which can be used in place of the
parameters identified above. Specifically, with reference to Figure 3, a
series of curves have been developed showing -rod number versus displace-
ment of the slice lip when a single rod, for example, rod 10 is moved in
one direction. Tests have shown that if the parameter c is a certain
value~ say Cl, and rod 10 is displaced a distance X1 then the slice lip in
the area ad3acent the rod 10 will be displaced as shown on the curve C1.
Likewise, if rod 10 is displaced a distance X2 then the slice lip adjacent
the rod 10 will be displaced according to curve C2, and if parameter c has
the value C3 and rod 10 is displaced a distance X3 then the slice lip will
be displaced accordin~ to curve C3. Once the parameter C has been deter-
mined, then the following equation can be used to operate the system.
= [A] c~Ra] + tJ] Y
It should be understood that although one particular type of actuator
is taught herein, the present invention is likewise applicable to other
types of actuators. For example, plastic extruders and other sheet mater-
ial processes employing actuators of the type taught herein or actuators
which are hydraulically powered or motor driven are appropriate ~or appli-
cation of the present invention.
,

Representative Drawing