Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS FOR CONTROLLING THE PRODUCTION
OF PAPER ROLLS PRODUCED BY THE REWINDER
IN ORDER TO ENSURE STEADINESS OF LENGTH
OF THE WOUND PAPER AND/OR OF REACHED DIAMETER
BACKGROUND OF THE INVENTION
In the preparation of logs or rolls of paper of
relatively small diameter from large diameter rolls produced
on a paper-making machine, the equipment and apparatus have
been well developed to produce such logs or rolls
automatically and at high speed.
Relevant patents relating to the background of this type
of paper-converting machinery and process are the U.S.
Patents 3,869,095, 4,327,877 and 4,422S88.
In the preparation of these logs or rolls, the web of
paper fed to the machine quite often varies in basis weight,
caliper, surface characteristics and the like, and it is also
important that the manufacturer provide the precise number of
sheets or usable units in each of the finished rolls.
All of this has to be accomplished while keeping the
outside diameter of the roll within pre-determined limits,
which are generally dictated by the wrapping and packaging
equipment, as well as by the size of the holder or dispenser
on which the finished roll is used by the consumer.
The core on which the paper is wound may also vary in
diameter, and this creates a further problem for the
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manufacturer in keeping the outside diameter of the finished
roll within pre-determined limits.
Under the circumstances, it is important for economic
and commercial reasons that the length of the paper wound
into the roll, the number of sheets or usable units provided
in the roll, and the outside diameter of the roll, be
controlled as accurately as possible. The apparatus of the
present invention provides such equipment.
SUMMARY OF THE INVENTION
The apparatus comprises means for detecting the desired
diameter, means for detecting the weight of a finished roll
and/or of the length of paper wound at any moment, means for
pre-setting the final diameter to be reached, as well as
means for comparing the pre-set data with the detected ones,
and correction means to keep length and diameter or weight
and diameter steady.
DETAILED DESCRIPTION
The invention relates to machines for paper manufacture
and, in particular, to the rewinders, i.e., machines which
are fed with one or more large rolls or with a roll of
two-ply paper, for the production of "logs" or rolls of paper
having relatively smaller diameter. These "logs" are
subsequently cut perpendicularly to their axes to provide
small rolls of paper for use as toilet paper, kitchen towels,
or for similar uses. In these machines, it is suitable and
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sometimes indispensable to provide an exact diameter of the
roll so that the small rolls meet requirements of successive
operations, such as cutting and packaging, as well as
practical requirements, such as fitting into a toilet-roll
dispenser.
It is also suitable (or even necesary) that the exact
diameter be obtained with a precise and pre-determined length
of paper, or with a precise and pre-determined number of
sheets (when the paper is perforated to be detached in sheets
of equal length), again for commercial requirements and so as
not to exceed desired paper length according to economical
requirements.
A particular requirement is that of keeping the length
(that is, the number of sheets of the paper) or the weight of
the small roll, and the diameter of the small rolls uniform,
even though the characteristics (such as basis weight or
caliper or surface finish) may not be constant.
The apparatus in question ensures control and correction
of the production in order to achieve uniformity of the
above-mentioned cahracteristics.
Therefore, it is an object to provide an apparatus for
controlling the production of rolls or "logs" of paper
produced by a rewinder fed with large rolls or two-ply paper
rolls, especially for ensuring an exact overall diameter and
the paper length and/or paper weight within pre-set limits.
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It includes means for detecting the desired diameter, means
for detecting the weight of a finished roll and/or the length
of paper wound into the roll, means for pre-setting the final
diameter to be reached, means for comparing the pre-set data
with the detected ones, and correction means.
Advantageously, the correction means may comprise a
regulator for adjusting the pressure, i.e., the thrust
exerted by a small presser acting on the surface of the roll
being formed.
The diameter-sensing means may be associated with the
small presser, and it is activated when the desired diameter
is reached.
The apparatus may be combined with an electronic logic
able to operate a correction by means of the small presser
acting on the roll being formed and activated by the thrust
exerted by said roll on the presser.
The apparatus may comprise at least two sensors and a
cam member, or an encoder, for evaluating limit positions,
and thresholds for controlling fine and coarse adjustments
according to the sensed diameter of the stick, i.e.,
according to the position of the presser assembly. There can
be provided two fixed sensors, which have adjustable position
and interspace, and a screen member located on an arm for the
angular displacement of the presser, in order to obtain the
various adjustments through four practicable and subsequent
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pulses. Alternatively, the diameter sensor may be arranged
as an encoder that measures the angular displacement of the
presser arm.
According to another embodiment,a weighing means may be
provided, such as a load cell, able to evaluate the weight of
the log or roll as data to be used for corrections.
Therefore, the apparatus provides for carrying out the
simultaneous control of the diameter and length of the paper
or of the weight of the log up to the pre-determined limit.
Moreover, the apparatus provides for keeping said diameter
exact when the characteristics of paper are changing, either
by imposing a change of length of the paper supplied for each
roll, or by keeping the length and the diameter steady
through a variation of the thrust operated by the small
presser.
In one embodiment, the presser thrust is reduced, thus
increasing the roll diameter with the same length of wound
paper. Vice-versa, paper may be added to the roll, in order
to reach the desired length, by causing a greater thrusting
action of the presser on the roll, to reach the pre-set
diameter with a greater quantity of rolled-up paper.
In a further embodiment, the apparatus allows the paper
weight to be kept steady through a variation of the length,
and by maintaining the diameter steady through a variation of
the presser thrust on the roll being formed.
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All the operations can be carried out with the machine
in operation, without interrupting the production process,
and providing for successive corrections up to the
restoration of the pre-set and desired limits.
With the above and other objects in view, more
information and a better understanding of the present
invention may be achieved by reference to the following
detailed description.
DETAILED DESCRIPTION
For the purpose of illustrating the invention, there is
shown in the accompanying drawings a form thereof which is at
present preferred, although it is to be understood that the
several instrumentalities of which the invention consists can
be variously arranged and organized and that the invention is
not limited to the precise arrangements and organizations of
the instrumentalities as herein shown and described.
In the drawings, wherein like reference characters
indicate like parts:
FIG. 1 shows a schematic representation of a rewinder,
limited to the main members for the winding of the paper web
into a roll.
FIG. 2 shows a block diagram of the electronic p~rts
relevant to the correction system.
FIG. 3 shows another embodiment similar to FIG. 1.
FIG. 4 shows an explanatory switching diagram.
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Referring to the attached drawings, and particularly
FIGS. 1 and 3, the continuously fed paper web N is
transversally perforated at equal distances (to provide
sheets) by a device l and is turned by a cylinder 2 in order
to be fed to the main cylinder 3. Cylinder 3 determines the
total length of web to be wound and includes a cutting
device, including a cylinder 5, which carries out the cutting
of said web N.
Number 7 indicates a cylinder which cooperates with
cylinder 3 and defines an interspace with it, wherein a
tubular core, preferably made of cardboard, is inserted--in a
known manner--in the direction of arrow fA. The paper web is
wound on the core to form the roll or log BS, which is then
suitably moved away in the direction of arrow fB. Such
cutting and winding arrangements are well-known, as shown in
U.S. Patent 4,327,877. They may include also a so-called
presser, i.e., a further pressing roller indicated by 9,
which is movably mounted, for example, on a pair of arms 12
pivoted at 14. Presser 9 is able to produce a suitable
pressure, that is, a thrust on the roll BS being formed and
thus to completely define the diameter of the roll.
Presser 9 is capable of varying the pressure exerted on
the roll BS being formed and thereby compact the paper in the
roll to a more or less degree. The presser 9 assembly, with
its supporting arms 12, allows also to sense the diameter of
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the roll being formed and, therefore, the presser itself may
cooperate with a diameter evaluating sensor. For example, the
regulation of the pressure exerted by the presser on the roll
may be obtained by an adjustable weight slidable along arm
12, by a screw-control or other device (not shown).
As shown in FIG. 1, a sensor is provided for evaluating
said diameter, which sensor comprises a screen 16 located on
the arms 12, and a sight 18 of optical type such as an
"electric eye", for example, at a fixed position. A more
simple arrangement includes a suitably positioned microswitch
which establishes the diameter that the roll BS must reach to
meet the above-mentioned requirements. Two optical sensors
may be provided that can regulate the coarse and fine
corrections of the presser thrust on the paper.
On the assembly of arms 12 of presser 9, means is
provided for adjusting the pressure to be exerted by presser
9 on the roll BS being formed. The regulator may consist of a
cylinder-piston system 20 supplied by pressure adjustable
through a control system, generally indicated by 22, which is
dependent on control means electronically operated according
to a suitable program. The regulator may operate by increase
of the pressure inside the system 20 and thus reduce the
presser thrust on the roll, and vice versa.
Fig.2 shows an electronic block diagram including an
input 31 for the data concerning the desired diameter, which
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data are obtained by a sensor like that indicated by 16,18 in
Fig. 1. Numerals 33 and 35 in Fig.2 indicate two timers
which are set for a longer and shorter time, respectively, to
obtain coarse and fine corrections, respectively. Numerals
36 and 37 indicate the date input for setting the lengths
(i.e., the meters) of paper representing the limits of the
allowable range of paper, while numeral 38 indicates the
input of the actual value of the length of the fed paper,
such input being supplied through a counter 24 associated
with cylinder 3. Numeral 39 indicates an electronic logic
which can receive a card (which can be easily changed)
containing the program. Numerals 41, 43, and 45 indicate
three gates associated with the three outputs of electronic
logic 39 and which receive also the data relevant to the
reached diameter from input 31. Gates 41 and 43 are intended
for the coarse correction and gate 45 for the fine
correction.
From gates 41 and 43 data are fed through lines 47 and
49 to two switches 51 and 53, respectively, for increasing or
decreasing coarse correction represented by blocks 55 and 57
respectively. Switches 51 and 53 receive the correction time
from timer 33 which is set for a longer duration. The two
corrections 55 and 57 may also be activated by switches 59
and 61, provided for the fine adjustment, which are connected
to timer 35, set for the shorter duration, and by gates 67
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and 69. The correcting signals arrive at switches 59 and 61
via two lines 63 and 65, respectively, coming from two gates
67 and 69 fed with data obtained via line 71 from the gate 45
of the electronic logic. Data for the delivery of the type
of fine correction to be made are obtained from lines 73 and
75 which are connected to the counter 24 for detecting the
length of passed paper, said counter being connected, for
example, to cylinder 3 and to the diameter sensor such as
that indicated by 16 and 18.
The operation of the apparatus is as follows.
As the optical sensor (or microswitch) 16, 18 - either
single or dual- is activated because the roll diameter has
reached the desired preset value, and the counter 24, which
provides the information relative to the length of wound
paper, has not arrived at any of the two selections preset by
36 and 37 in the electronic logic, it is necessary to
increase the length of paper and thus the pressure of presser
9 must be increased so that greater compaction of the rolls
of paper will allow an accumulation of a larger amount of
paper while maintaining the roll diameter at the desired
value.
If the microswitch 16, 18 is actuated and the counter 24
has already reached the upper selection limit for the
allowable paper length, this means that there is sufficient
paper in the roll, and as a consequence the pressure of
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presser 9 must be lowered so that the desired diameter is
reached with a smaller amount of paper.
The two above-mentioned corrections are achieved
through timer 33 and the enabling controls on switches 51 and
53 coming from gates 41 and 43 respectively.
Figs. 3 and 4 show a modified embodiment, in which two
proximity or optical sensors 118 and 120 can cooperate with a
screening body 116 carried by arm 12. Sensors 118 and 120
may be carried by a support 122 pivotable at 114. Likewise
arm 12 is pivotable at 114. Support 122 is adjustable, for
example, by a screw 126 to set the position of the two
sensors 118 and 120 and thus the desired diameter for roll
BS. The distance between the two sensors 118 and 120 can
also be adjusted for establishing the tolerance of the
diameter of roll BS.
In this embodiment, the regulation system is driven by a
series of pulses. With reference to the diagram of Fig. 4,
lines 201, 202, 203 and 204 may be considered as the
thresholds delimited by pulses obtained from the pair of
sensors 118 and 120 influenced by screen 116, wherein:
- 201 corresponds to the screening (actuating) pulse
of the first sensor;
- 202 corresponds to the releasing (abandoning) pulse
of the first sensor;
- 203 corresponds to the screening (actuating) pulse
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of the second sensor; and
- 203 corresponds to the releasing (abandoning) pulse
of the second sensor.
The regulation may be carried out by comparing the
output of counter 24 driven by the main cylinder 3 (pro-
portional to the length of wound paper) with pulses 201,
202, 203 and 204 through the following logical consequences:
(1) If the preset counting goes off and pulse 201 has
not yet arrived, it is necessary to provide a coarse
regulation to lower the presser thrust and slacken the
winding in order quickly to increase the diameter of roll BS;
(2) If the preset counting goes off and pulse 201 has
already arrived, it is necessary to provide a fine regulation
to lower the presser thrust;
(3) If the preset counting goes off when pulse 201 has
already been delivered and pulse 202 has not, it is necessary
to provide a fine regulation in order to increase the presser
thrust:
(4) The moment pulse 202 goes off and up to the moment
the pulse 203 goes off, the diameter is within the tolerance
range;
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(5) If the preset counting goes off and pulse 203 has
already arrived, it is necessary to provide a fine regulation
in order to increase the presser thrust;
(6) In the interval between pulses 203 and 204, the
fine regulation is maintained;
(7) If the preset counting goes off and pulse 204 has
already arrived, it is necessary to provide a coarse
regulation in order to increase the presser thrust and
reduce the diameter.
All this is accomplished by utilizing the two proximity
sensors 118 and 120 whose distance of application determines
the tolerance field TL accepted for the roll diameter, in
relation to the thickness of the screening body 116 carried
by the presser 9, 12.
Another solution can be that of mounting a pulse
genertor on the fulcrum 14 of arm 12 of presser 9 and
comparing the pulses thereof with those emitted by the
counter 24 on cylinder 3 with the same criteria as those of
the preceding solution.
What has been described above relates to a kind of
operation in which a certain length of paper is set before-
hand, and diameter adjustments are imposed through variations
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of the thrust operated by presser 9 on the roll being formed
in order to assure that the final diameter of the rolls is at
the desired value.
As soon as the screening body 116 obscures the first
sensor 118, a pulse takes place and the programmer compares
the length of paper passed through - evaluated by pulses
produced by the counter 24 on cylinder 3 - with the preset
length (which takes into account a constant which is
necessary to carry out the whole exchange cycle) and, if the
two values are substantially equal, the change of rolls (an
operation which always takes place in any case) is actually
carried out without making a change in the presser thrust.
If, instead, the two values are different (being either
greater or smaller) the system will initiate a change by
decreasing or increasing the thrust of the presser in order
to correct the amount of paper in the roll. The greater the
difference between the two countings (paper length and
diameter of roll BS), the greater will be this correction.
Alternatively, the diameter and weight of the roll may
be preset and the corrections performed by imposing
variations in the length of paper. In this case, the
diameter of the roll is ensured but not the length of the
wound paper, which length may vary by an amount of even one
revolution of cylinder 3.
Weighing systems may be included, such as load cells
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like those shown in dotted lines at C in Fig. 3 for weighing
the roll which has left the position BS (where it was formed)
and has moved along chute S in the direction of arrow fB. By
the weight date it is possible to affect the corrections of
the presser thrust and/or of the length of the paper which
has been fed to each roll.
It is furthermore to be understood that the present
invention may be embodied in other specific forms without
departing from the spirit or special attributes, and it is,
therefore, desired that the present embodiments be considered
in all respects as illustrative and, therefore, not
restrictive, reference being made to the appended claims
rather than to the foregoing description to indicate the
scope of the invention.
