Note: Descriptions are shown in the official language in which they were submitted.
CA 02357336 2001-09-14
PERIPHERAL REWINDING MACHINE AND METHOD
FOR PRODOCING LOGS OF WEB MATERIAL
Background
The present invention relates to a peripheral rewinding machine and a
related rewinding method for the production of rolls or logs of web material,
such as paper and the like, on a tubular support or core.
In a peripheral or surface rewinding machine of the type to which the
invention refers, the roll is wound around a tubular core which is set in
rotation
between a group of three rollers that act on the periphery of the roll being
formed, and the speeds of which are kept constant and equal during the winding
cycle.
The group of three motorized rollers forms a space of variable size so
that the three rollers are always in contact with the roll being formed, as
the roll
increases in diameter. Two of the three rollers are placed at a fixed
distance, so
as to define a gap, through which the core is inserted, and in which the web
material travels, whilst the third roller or pressure roller is movable to
allow the
diameter of the roll to increase and the roll to be expelled at the end of
winding.
In these rewinding machines the so-called changeover stage, sometimes
called cutoff and transfer, is important. That stage includes insertion of a
new
core in the winding space, accompanied by a special inserter, and discharge of
the completed log, following severing of the web material. This severing is
obtained in various ways according to the prior art, generally requiring
sudden
changes in the speed of two of the three winding rollers.
According to some known methods, the speed change of said rollers
alone, which is naturally of rather a large magnitude, causes tensioning and
tearing of the web of paper following nipping thereof against the roller along
which it is fed, nipping which can take place by means of a new core which is
inserted in the winding space. After severing of the web of paper, entry of
the
new core into the winding space and discharge of the formed log take place
through differences in speed between the two input rollers and the two output
rollers, respectively.
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As stated previously, this method of severing the paper requires large
variations in speed between the rollers, and in particular strong
accelerations of
the pressure roller, which cause stress on the structure of the machine.
Moreover, such methods make it difficult to sever the web material along a
single pre-selected perforated line to provide the completed log with exact
sheet
count.
Other systems use true cutting blades that cut the web at the end of
winding and require complicated actuating mechanisms. Moreover, they are not
very flexible in that they are tied to carrying out the cut on well-defined
lengths
of web material.
Summary of the Invention
The object of the invention is to eliminate the drawbacks of the solutions
of the prior art, and therefore to provide a rewinding machine and a rewinding
method that are reliable and simple to create and ensure precise cutting of
the
web material.
This object is achieved with the rewinding machine and method
according to the appended independent claims. Preferred embodiments of the
invention are apparent from the dependent claims.
Substantially, according to the invention, a blade is carried by a rotating
member which is pivoted on the axis of the roller around which the web
material is wound and rotates in the same direction as the roller is provided.
The rotating member is actuated when the log is in the completion stage at a
speed equal to or substantially similar to that of the web material, to be
subsequently slowed or accelerated when it is inside the winding space, to
cause
tensioning and severing of the web material. Normally severing of the material
takes place along a line of perforation in the web.
Further characteristics of the invention will be made clearer by the
detailed description that follows, referring to a purely exeiriplary and
therefore
non-limiting embodiment.
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Descriution of the Drawings
The invention will be explained in conjunction with the
drawings, in which -
Figure 1 is a schematic side view of the basic elements of the rewinding
machine according to the invention;
Figures lA to 6A are views like that in Figure l, illustrating successive
stages of the winding cycle according to a first embodiment of the invention;
Figures 1B to 6B are views like that in Figure 1, illustrating successive
stages of the winding cycle according to a second embodiment of the invention.
Descriution of Suecific. Embodiment
With reference to said figures, for now in particular to Figure l, which
schematically illustrates a few more elements of the machine, a brief
description
of said elements will be made. In the description that follows, reference will
be
made in the singular to the elements shown in the drawings, it nevertheless
being obvious that many of them, such as the arms and levers, are disposed in
pairs, at the two sides of the machine.
In the appended figures, W designates a web material, in particular paper,
which is unwound from a large-sized roll, not shown, and, travelling in the
direction of the arrow F, is suitably tensioned by rollers R1 and R2 and wound
around a first winding roller A, to be rewound in rolls or logs 1, of a
considerably smaller diameter, around a tubular central core 2.
The first winding roller A is associated with a second winding roller B,
which defines therewith a gap 3, through which the cores 2 are inserted. The
width of the gap 3 is constant during operation of the machine and not greater
than the diameter of the core so that the latter enters the gap with slight
forcing.
One of the two rollers A, B, in the example shown the first winding roller A,
is
supported by a mobile arm 4, schematised in the figure, pivoted at 5, to
adjust
the width of the gap 3 to the diameter of the core 2 which is used.
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The group of three winding rollers is completed by a third roller C, also
called a pressure roller, supported by an arm 6 movable around a fulcrum 7,
according to a pre-determined law of motion, to allow the roll 1 to be
increased
in diameter and discharged at the end of winding. The rollers A, B, and C are
ratatably mounted in a frame (not shown) and may be controlled by
conventional servo motors.
Upstream of the gap 3 a feed slide 8 is provided for the cores 2. A core
inserting device comprising idler rollers 9 is carried at the end of an arm 10
pivoted at 11. The arm 10, which in the appended figures has been schematised
with a segment of straight line, in fact has, in a per se known manner, a beak
shape so as to push the core 2 into the winding space without interfering with
the winding roller B.
A rotating member 14 carrying a blade 15 protruding beyond the profile
of the roller A is pivoted on the axis X of the first winding roller A. The
member 15 has been called and will henceforth be called a blade, in that it
causes severing of the web material, as will be explained below, but in fact
it
may not have, and preferably does 'not have, knife-type cutting edges.
The rotating member 14 is driven in rotation in the same direction as the
roller A, which is anticlockwise in the appended figures, and is motorized
separately by means of a belt drive 16 actuated by a motorized wheel 17 and
passing round a tensioning roller 18. Obviously, other actuating means can be
provided for the rotating member 14, such as, for example, chains, gears and
the
like. The wheel 17 can be controlled by a servo motor.
Operation of the machine according to two different embodiments,
shown respectively in Figures lA to 6A and 1B to 6B, will now be illustrated,
using in both cases the same reference numerals to designate like or similar
parts.
In the embodiment according to Figures lA to 6A , the blade 15 has a
concave shape toward the outside, substantially a very wide V shape, with the
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first leg, in the direction of rotation, longer than the other and less
inclined with
respect to the tangent to the winding roller A.
Figure lA illustrates the configuration of the machine during winding of
the roll l, with the blade 15 in the resting position, that is with the
rotating
member 14 at a standstill. In this condition, the three rollers A, B, C all
rotate at
a constant and substantially the same speed, a speed which corresponds to the
feeding speed of the web material.
In Figure 2A the machine is near the changeover, that is about at the end
of winding of roll 1, when said roll is about to be discharged and a new core
2
must be inserted. In this stage the blade 15, together with the rotating
member
14, is set in rotation by the motorized wheel 17 and the belt drive 16 in the
same
direction of rotation as roller A, indicated by the arrow F1 in the appended
figures. After an initial acceleration stage, the blade 15 reaches the same
speed,
or a very similar speed, as that of the web material W.
In the stage illustrated in Figure 3A, the blade 15, which travels at
substantially the same speed as that of the web material W, has slightly
raised
the material W from the profile of the winding roller A and is accompanying it
into the winding space. Again in this stage, the core inserting arm 10 begins
to
rise to bring a new core 2 into the gap between the two rollers A, B.
In Figure 4A the log 1 is practically completed and severing of the web
material is taking place. In this stage the pressure roller C has begun an
acceleration stage, and the bottom roller B is possibly slowed, causing the
roll 1
to move toward the outlet from the winding space. At the same time, or with
slight staggering with respect to the acceleration of the pressure roller C,
the
blade 15 is slowed, so that the web material W has to slide on the contact
edge
15' of the blade 1 S. In this situation, a transverse line of perforation of
the web
material comes to pass on the point of contact 15' with the blade 15, and
tensioning of the web material due to acceleration of the pressure roller C
causes such a lengthening as to cause separation of the material at said line
of
perforation, as shown in Figure SA.
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It can be advantageous for the blade 15 to have a high coefficient of
friction, at least at the point of contact 15' with the web material W, so as
to
facilitate severing of the web material. However, depending upon the types of
material to be wound, the various types of perforations adopted, or even the
lack
of perforations on the web material, the blade 15 can assume different
configurations, for example, with a continuous edge, serrated, or the like.
Returning to Figure 5A, it can be noted that a new core 2, on which an
adhesive has previously been spread, comes into contact with the already
separated web material W, beginning to wind it on itself, thus starting
formation
of a new roll 1, which is moved into the winding space by a possible
difference
in speed between the rollers A and B, the latter having previously been
decelerated.
This situation is shown in Figure 6A, where the formed log has been
expelled and a new log being formed is entering the winding space. The blade
15 is moving into the resting position and the core inserting arm 10 is going
back to pick up a new core, to start a new winding cycle, and the three
rollers A,
B, C begin to rotate again at the same speed.
In the embodiment illustrated in Figures 1B to 6B, the same series of
stages is shown as in figures lA to 6A of the first embodiment, therefore they
will not be described in detail.
The substantial difference of this second embodiment with respect to the
first lies in the fact that the blade 15 is accelerated instead of decelerated
to
cause separation of the web material W. For this purpose, the blade 15, made
of a material with a high coefficient of friction, is advantageously given a
convex profile toward the outside.
In the situation in Figure 4B, the acceleration of the blade 15 with the
strong grip on the portion of web material W nipped by the new core 2 against
the upper winding roller A, causes a further stretching of the web material
and
thus severing along the line of perforation between the core being inserted
and
the blade.
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Of course the invention is not limited to the particular embodiments
previously described and illustrated in the appended drawings, but numerous
changes of detail within the reach of a person skilled in the art can be made
thereto, without thereby departing from the scope of the invention, as defined
by
the appended claims.
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