Note: Descriptions are shown in the official language in which they were submitted.
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EDGE SENSING ARRANGEMENT
The invention relates to an arrangement in connection with a wire
guide roll of a paper machine, which arrangement comprises a wire guide roll
transverse to the direction of travel of a wire, the wire guide roll being
arranged
to be turned in the direction of travel of the wire by means of at least one
ac-
tuator, and which arrangement comprises a guide flap arranged against the
wire edge and adapted to observe the lateral position of the wire, and in
which
arrangement the wire guide roll is arranged to turn and guide the wire on the
basis of information provided by the guide flap on the lateral position of the
wire and which arrangement further comprises means that are arranged to
inform a control system of the paper machine of the lateral position of the
wire.
Various wires are used in paper machines for conveying and sup-
porting a fibre web. In this connection, a paper machine can also be under-
stood as a board machine, a pulp washing apparatus and similar paper
manufacturing equipment provided with wires. When a wire is passed around
and supported by different rolls in a paper machine, the wire may be driven to
either edge in its direction of travel, which makes the wire edge rub against
the
structures of the paper machine. The wire does not naturally withstand this
kind of strain, but will be damaged. The wire itself can be the reason why the
wire is driven to the side, but usually this is caused by erroneous positions
of
rolls. Also impurities adhered to the rolls and the wire may cause the wire to
move in the lateral direction. To solve the problem 'a wire guide roll', which
prevents the wire from drifting in the lateral direction, is arranged in
connection
with wire circulation. When the wire is driven to the side, the wire guide
roll is
automatically turned to the required direction, and the wire is guided back to
its
right track of travel. The guide roll receives the guidance information from a
guide flap which continuously monitors the edge of the wire. In addition to
the
guide flap, paper machines generally have edge flaps at both edges of the
wire, which sense the lateral position of the wire and give an alarm to the
con-
trol system of the paper machine, if the wire is for some reason driven too
close to the edge. A prior art solution is described later in Figure 1 and in
its
description. A drawback of the known solution is, however, that arranging the
equipment into a paper machine is laborious. It is difficult to arrange
several
flaps, fasteners of the flaps and cables leading to the flaps to narrow places
with demanding conditions. In addition, maintenance is difficult, since the
sen-
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sors are located on different sides of the paper machine and far away from
each other. Some mass washing apparatuses apply a thin single-layer wire,
and when the known solution is employed, the problem has arisen that the
guide flap bends the thin wire from its edge, and as a- result of the bent
edge
the edge flaps provide the control system of the paper machine with wrong
information and the operation of the flaps is also otherwise unreliable. In
addi-
tion, since the guide flap and the edge flaps are at a distance from the guide
roll in the direction of travel of the wire, delays occur in the wire
adjustment
and control. It is also expensive to manufacture the solution, since it
comprises
a lot of various components.
Furthermore, solutions are known, in which optical sensors or pres-
surized air streams are used in sensing the position of the wire. The problem
of such solutions is, however, that the sensors become dirty and faulty under
severe conditions and, compared to mechanically performed monitoring, the
operation is also otherwise unreliable. The use of inductive sensors has also
been tested, but similar problems have come up in connection with them as
well. The solution further requires that a metal strip or the like, which the
in-
ductive sensor detects, is arranged to the wire edge. This kind of a wire is,
however, expensive.
It is an object of the invention to provide an arrangement by which
prior art problems can be avoided.
The arrangement of the invention is characterized in that at least
one sensor is arranged in connection with the guide flap and that the informa-
tion on the lateral position of the wire is adapted to be transmitted from the
sensor to the control system of the paper machine.
The essential idea of the invention is that the guide flap is arranged
to observe the edge of the wire in continuous contact and, in case the wire is
driven to the side, give guidance information to the control unit controlling
the
actuator, whereupon the wire guide roll is made to turn and the wire is guided
back to its right lateral position. Further, means for transmitting
information on
the lateral overtravel of the wire to the control system or the like of the
paper
machine are arranged in connection with the guide flap. The guide flap is ar-
ranged after the guide roll, into its immediate proximity, in the direction of
travel of the wire, and the devices that monitor and control the lateral
position
of the wire form an entity. Furthermore, an essential idea of a preferred em-
bodiment of the invention is that there are limit switches or corresponding
sen-
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sors at the guide flap arm, which determine the lateral position of the wire.
This way it is also possible to register the cases where the wire exceeds the
allowable predetermined operating range. The essential idea of another pre-
ferred embodiment of the invention is that there are sensors at the guide
flap,
which continuously observe the lateral position of the wire and transmit infor-
mation on the lateral position of the wire to the control system of the paper
machine.
The invention provides the advantage that no separate edge flaps
are required at both edges of the wire, but the wire position is only observed
by means of the guide flap. Sensors observing the wire edge are arranged at
the guide flap. Thus, edge flaps need not be manufactured and installed at
all.
The structure of the system becomes simpler and the maintenance much
easier. The solution also enables the use of thin wires, which are cheaper and
easier to run. In addition, since the guide flap is located near the guide
roll, the
wire at the guide flap is well supported by the guide roll, and therefore the
thin
wires no longer tend to bend because of the guide flap either. Thus, the wire
edge can be observed accurately and reliably. The arrangement of the inven
tion further allows the wire to be run looser as before, which makes the wires
to last longer in use. When the guide flap is arranged in connection with the
guide roll, no harmful delays occur in the control system.
The invention will be described in greater detail in the attached
drawings, in which
Figure 1 is a top view of a prior art arrangement,
Figure 2 is a schematic side view of a solution of the invention,
Figure 3 schematically shows a detail of a solution of the invention,
and
Figure 4 schematically shows a detail of another solution of the in-
vention.
Figure 1 is a top view of a prior art arrangement for controlling the
lateral position of a wire. A wire 1 is run in the direction A. For various
reasons
the wire may be driven to the side in the direction B transverse to the
direction
of travel of the wire. The position of the wire in the lateral direction B is
sensed
by means of a guide flap 2 which is arranged after a guide roll 3 in the direc-
tion of travel of the wire. The guide flap is in continuous contact with the
wire
edge. A guide flap, or 'a spoon', is a plate-like element, usually bent to be
slightly curved, which is pushed by means of a spring, for example, against
the
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edge of the wire. Guidance information is transmitted from the guide flap to a
control unit 4 which controls an actuator 5 operating the guide roll. The
actua-
tor is typically a pneumatic bellows, and the pressure that is fed to it is
regu-
lated by means of an air control valve of the control unit. Usually the guide
flap
is directly arranged to mechanically use the air control valve. Based on the
guidance information obtained from the guide flap, the actuator moves one
end of the guide roll in the longitudinal direction C of the wire. Since the
other
end of the guide roll is arranged pivotally to the frame, the actuator makes
the
guide roll turn. On the other side of the guide roll there is another
pneumatic
bellows 8, to which constant pressure is fed. Thus the direction of movement
of the guide roll is determined by the interrelation of the pressures to be
fed to
the first and the second bellows. The known arrangement further comprises
edge flaps 6 and 7 which are arranged at both sides of the wire and give an
alarm if the wire comes into contact with the flaps. The alarm that indicates
the
exceedings of the edge zone is transmitted to the control system 15 of the pa-
per machine. Thus the edge flaps and the guide flap in connection with the
wire guidance are entirely separate units from each other, and moreover, they
are complicatedly arranged at a considerable distance from each other.
Figure 2 shows a simplified view of an arrangement of the invention,
as seen from the movable end of a wire guide roll. A wire 1 is arranged to
move in the direction A via a guide roll 3 which, to make the guidance more
effective, is arranged to be elevated such that the wire bends slightly at the
guide roll. The end of the guide roll is supported by a bearing support 9,
which
is pivoted to a frame 11 by means of slide blocks 10 or rollers, for example,
whereupon it can be moved in the direction C. The guide roll end is turned by
means of actuators 5 and 8. The actuators are preferably pneumatic bellows
as shown in the figure, but also pneumatic and hydraulic cylinders, electric
motors and other devices that are suitable for this purpose can be used. Al-
though the figure shows two different actuators arranged at opposite sides of
the guide roll, the guide roll can also be used by only one actuator that can
be
moved in two directions, or the return motion can be performed by means of a
spring element, for instance. The guide roll can also be moved from its both
ends, but usually this is not necessary. According to the idea of the
invention,
a guide flap 2 is arranged into immediate proximity of the guide roll. The
guide
flap is then so close to the guide roll that the wire edges are still firm,
due to
the supporting effect caused by the nearby guide roll. Preferably the guide
roll,
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control unit and guide flap form an entity, to which it is easy to install the
re-
quired cables, pipes etc. and which can be serviced via one service lid, if
nec-
essary. An air-pressure duct leading to an air control valve 4 is marked with
a
line of dots and dashes 16 in the figure, a channel leading to the first
actuator
5 with a line of dots and dashes 17 and a channel to be led to the second ac-
tuator, intended for transmitting constant pressure, with a line 18. A
conductor
leading to the control unit of the paper machine is marked with a broken line
19.
Figure 3 shows a detail of an arrangement of the invention. A guide
flap 2 is arranged to the free end of an arm 12, whereby the lateral movement
of a wire 1 turns the arm in respect to the pivot point of the arm. The arm is
combined with the air control valve of a control unit 4 such that the movement
of the arm opens and closes the connection from a compressed air source to a
pneumatic bellows 5 according to the lateral position of the wire. The
allowable
transversal range of movement of the wire is marked with a reference L in the
figure. The exceeding of the allowable range of movement is controlled for
example by means of edge sensors 13 and 14 arranged to give an alarm to a
control system 15 of the paper machine. The edge sensors can be limit
switches, inductive sensors or the like which are arranged to be activated
when the arm 12 moves to a certain extent. The relative position of the edge
sensors can be adjusted, and thus the size of the allowable operating range
can be changed.
In addition, one or more sensors 20 measuring the position of the
guide flap can be used, and the measuring result is transmitted to the control
system 15 of the paper machine. In this case the lateral position of the wire
can be continuously measured during the operation of the paper machine.
Such an application is shown in Figure 4. Values corresponding to the allow-
able range of movement can be programmed in the control system/automation
system of the paper machine. The information on the exceedings of the allow-
able range of operation L and the position of the wire can be utilized in the
maintenance, when the conditions of the wire and wire guide roll are evaluated
and further when the operating parameters of the paper machine are adjusted.
It can also be seen from Figure 4 that the guide flap can also be arranged to
be moved linearly in the direction B by means of a suitable slide mechanism,
for instance.
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In this application, a control system of a paper machine is under-
stood as various automation systems, a user interface and, in its simplest, a
control panel of a paper machine. A control unit, for its part, can in its
simplest
be an air distributor with a mechanically or electrically operated control
valve
for controlling the pneumatic actuator. The control unit may also be a pro-
grammable logic controlling the electric motor, for instance, or some other
suitable controller between the actuator and the guide flap.
The drawings and the related description are only intended to illus
trated the idea of the invention. The details of the invention may vary within
the
scope of the claims. Consequently, besides a plate-like flap, the guide flap
refers to other elements which can be applied to the monitoring of the
position
of the wire edge and arranged into physical contact with the wire edge.
