[0001] The present invention relates to systems for supplying moving web material in accordance
with the preamble of Claim 1 hereinbelow.
[0002] A system of this type is known - for example - from US-A 3 995 791. This document
describes a system for the continuous supply of moving web material, the system in
question consisting, inter alia, of two stations intended to accommodate the rolls
from which the web material is to be paid out. The web is taken alternatively from
one or the other of the said stations, matters being arranged in such a manner that
the expiring end of the web from a dispensing roll in one station is spliced to the
beginning of the web from a ready roll carried in the other station, thus avoiding
solutions of continuity in the supply (payout) of the web. The system in question
includes a web storage device in the form of a so-called web festooner. When web supply
is to be switched from one roll-carrying station to the other and the two web ends
have to be spliced together, the said web storage device is brought into action in
a positive manner by mechanical means in synchrony and in phase with a set of rollers
that feed the web material towards the utilization station. The speed at which the
web material is paid out on the output side of the system therefore stands in a fixed
mechanical relationship with the speed at which the web is utilized, and this makes
it possible to bring the motion of the web to a halt upstream of the web storage device,
so that the two web sections can be spliced in what are to all intents and purposes
conditions of standstill. As soon as the splicing operation has been completed, the
system is set in motion again and the web storage device begins to reconstitute a
certain web reserve contained in its interior, thus making possible a subsequent roll
switching and web splicing operation in exactly the same conditions as have just been
described.
[0003] More particularly, in the solution described in US-A-3 995 791 matters are arranged
in such a way that the web storage device is inserted in a position directly between
a web splicer and the unit that feeds the web towards a utilization station situated
at the downstream end of the system. The system is controlled as a function of the
operating speed of the said unit feeding the downstream station. When it becomes necessary
to switch the rolls and splice the web, a signal provided by a sensor unit associated
with the dispensing roll that is about to run out triggers the intervention of a cam
mechanism that is operated by the shaft of the traction unit moving the web in the
downstream station. The said mechanism not only causes a gradual slowdown of the speed
with which the web is moved in the splicer (bringing it to a complete standstill),
but also brings into action the driving means associated with the web storage unit.
This is done in such a manner that, even during the period of time needed to complete
the splicing of the web, the supply needs of the utilization station at the downstream
end are satisfied by a length of web material taken from the storage device. As soon
as the splicing has been completed, the web material in the splicer is gradually re-accelerated,
while the driving means of the web storage device are gradually slowed down, these
processes being continued until the re-establishment of the normal operating conditions
in which the supply needs of the downstream utilization station can be satisfied directly
by web material passing through the splicer. Subsequently, the driving means of the
web storage device are activated again, but this time in the direction opposite to
the previous one, so that the web storage unit can gradually build up a new web reserve.
[0004] This solution in accordance with the state of the art is however associated with
some basic problems and difficulties.
[0005] Firstly, the deceleration/acceleration of the web motion at the splicer, as also
the complementary motion of the driving means of the web storage unit, are piloted
in a rigid manner via a cam mechanism, so that - for example - it is not readily possible
to modify the applied acceleration and deceleration laws to take account of possible
variations of the operating parameters (size and moment of inertia of the web rolls,
etc.).
[0006] Secondly, the fundamental parameter for controlling the operation of the system is
the rate (speed) at which the utilization station situated downstream of the web storage
device absorbs the web. Both the speed of the web in the splicer and the speed of
the driving means of the web storage device are controlled as functions of this absorption
rate, though always in the previously described rigid manner.
[0007] Another drawback - and one that is extremely penalizing whenever the web material
in use is of a delicate nature - is constituted by the fact that the part of the web
comprised between the splicer and the unit that feeds the web to the downstream station
has to be dragged in a positive manner between these two points and also in the web
storage unit. Any instantaneous difference of speed between the various moving parts
will therefore inevitably become translated into a longitudinal tensile stress acting
on the web.
[0008] A solution of the previously described type can therefore prove to be generally satisfactory
from the functional point of view only for as long as one is concerned with relatively
low web payout speeds at the output side (generally less than 150 m/s) and web materials
of relatively good tensile strength characteristics to enable them to withstand the
traction forces, polyethylene and nonwoven tissue being two cases in point.
[0009] However, the present trend, especially in the sector of the production sanitary and
hygienic products (for example, disposable hygienic products as sanitary towels for
ladies, nappies and nappy pants babies, and the so-called nappies for enuresis), is
to operate with much higher payout speeds (typically of the order of 300 - 500 m/s)
even when such relatively fragile materials as cellulose wadding (the so-called "tissues")
are involved.
[0010] When the operations are carried out at such high speeds and involve relatively fragile
materials, it becomes imperative, especially in the transitory phases associated with
the switchover of the web supply stations and the subsequent splicing of the two lengths
of web material, to avoid the possibility of the materials becoming subjected to stresses.
This is particularly true as regards longitudinal tensile stresses, which are liable
to compromise the very integrity of the web material.
[0011] More generally, there also exists the need of providing devices of the type specified
above and having operating characteristics that are either substantially or even completely
independent of any equipment situated upstream and/or downstream thereof.
[0012] For example, the system described in the previously cited US-A-3 995 791 is intrinsically
bound up with the possibility of having to function in combination with a splicer
intended to operate in standstill conditions (that is to say, in accordance with what
are nowadays known as "zero speed" modalities). The state-of-the-art system as previously
described does not therefore constitute a self-contained unit capable of performing
its function of supplying web material in a controlled manner, complete with storage
capacity, in an autonomous manner. In particular, the said system is
de facto designed and realized as a function of the processing stations situated upstream
(splicer) and downstream (utilization station) of it. Such a device, conceived to
operate with a splicer that works in "zero speed" conditions, cannot be adapted to
enable it to function also with a splicing system capable of working in dynamic conditions,
i.e. without bringing the web to a standstill, except on the basis of a complete reconfiguration.
The previously examined state-of-the-art system does not therefore lend itself to
being used for retrofitting operations involving already existing installations.
[0013] It is nevertheless very important to have at one's disposal systems or devices that
can be combined with any type of web supply and switchover device and therefore offer
the possibility of carrying out modernization operations on existing plant with a
view to improving the performance of such installations in terms of operating speed.
[0014] Yet another need that is being felt to an ever greater extent is that of being able
to use as web supply sources also very unstable raw material rolls (i.e. rolls having
a very high ratio between the diameter and the width of the material) and rolls of
web material having a very high moment of inertia (direct consequence of a large roll
diameter or roll weight), at the same time avoiding the roll damage phenomena of the
type generally known as "decoring", i.e. the phenomenon arising when the core on which
the web material is wrapped becomes removed from the roll in an undesirable manner.
[0015] The present invention sets out to provide a device of the type specified hereinabove
such as to overcome the drawbacks associated with the state-of-the-art systems and
thus to provide a wholly satisfactory answer to the various needs just discussed.
[0016] According to the present invention, this scope can be attained by a device for the
continuous supply of web materials having the additional characteristics set out in
the claims hereinbelow.
[0017] The invention will now be described, though solely by way of an example not to be
considered as limitative in any manner or wise, by reference to the drawings attached
hereto, where:
- Figure 1 is a general view in elevation of a device according to the invention,
- Figure 2 is a perspective view of the said device, and
- Figures 3 to 5 are three diagrammes that illustrate the behaviour of the device in
accordance with the invention.
[0018] The reference number 1 in the figures and drawings attached hereto indicates the
whole of a device capable of being used for supplying web material in a controlled
manner and with storage capacity.
[0019] The web material, which is indicated by the letter W, may be - inter alia - a web
material (sometimes also referred to as "fabric") to be used for the production of
sanitary and hygienic products, including those of the previously mentioned type.
In particular, the web material W may be constituted by a material such as cellulose
wadding ("tissue") that has very limited resistance to mechanical stresses, especially
tensile stresses in the longitudinal direction. It is however quite evident that the
specific reference to the manufacture of sanitary and hygienic products is not to
be interpreted as in any way limiting the scope of the present invention, which has
a particularly wide range of possible uses.
[0020] In the embodiment example here illustrated - which, be it said once more, is no more
than such - the device 1 is essentially configured as a module intended to be inserted
between processing stations on its upstream and downstream side in the general context
of a plant for the processing and/or handling of web material.
[0021] In the example explicitly illustrated by Figure 2 the device 1 may be located on
the downstream side of a supply unit made up of a pair of stations intended to carry
the respective rolls B1, B2 of web material, the said stations being associated with
a splicer S to be used for making the joints between successive lengths of web material,
which is taken in alternating sequence from the said two rolls. To all intents and
purposes, the arrangement of the said supply unit may be substantially analogous to
the one illustrated in US-A-3 995 791, a document already repeatedly referred to hereinabove.
[0022] Any type of utilization station employing the web material W may be situated on the
downstream side of the device 1. For example, the said station (which is not illustrated
here) may employ a typical "in line" process to pair the web material W with other
web materials to form a chain of hygienic and sanitary products intended to be separated
by means of a subsequent chain segmentation operation, thus giving rise to individual
products.
[0023] It will nevertheless be appreciated that the characteristics and the nature of the
processing stations situated upstream and downstream of the device 1 are not in themselves
particularly relevant as far as a proper understanding of the embodiment of the present
invention is concerned. In general terms, in fact, the invention aims at realizing
a device capable of receiving at its intake side (i.e. the position generically indicated
by the reference number 2 on the drawings annexed hereto) a web material W that is
being supplied to it at a given input speed. This input speed may be selectively varied,
this even to the point of completely zeroing the said speed and thus bringing the
incoming supply of the web W temporarily to a standstill. The device 1 seeks to make
the web material W available at its output side (i.e. the position generically indicated
by the reference number 3 on the drawings annexed hereto) at a speed that within reasonably
brief intervals of time (such as those necessary for making a splice between two successive
lengths of a web material W) will be substantially independent - and to all intents
and purposes wholly independent - of the speed at which the said material is supplied
to its intake side. And this while yet making sure that the part of the web material
W actually contained within the device 1 will not become subjected to forces capable
of producing tensile stresses in the longitudinal direction.
[0024] In the embodiment example here illustrated, the device 1 consists of a vertical supporting
panel 4 that may be constituted either by a frame or a single member of solid structure,
usually realized as steelwork. Fixed to the supporting panel 4, in the solution here
illustrated more or less in a central or midway position, there is a solid cage 5
that carries, likewise in a fixed position with respect to the support 4, a first
set of rollers 6 (the set consisting of five such rollers in the particular embodiment
here illustrated). The rollers 6 are here represented as capable of rotating freely
around a horizontal axis.
[0025] In the embodiment example here illustrated the cage 5 projects from the supporting
panel 4 in a horizontal direction, the general arrangement being that of a bracket
(or shelf). Likewise mounted on the said supporting panel 4 there is a series of vertical
guide rails 4a on which there is mounted a sliding trolley 7 that in the vertical
direction extends to above the cage 5. On the trolley 7, in turn, there is mounted
a certain number of rollers 8 (there being four such rollers in the particular embodiment
here illustrated), which can once again rotate freely on a horizontal axis and are
located above the rollers 6 carried by the cage 5.
[0026] As can be seen more readily from the side elevation shown in Figure 1, the rollers
8 are arranged in such a manner that, as seen in plan, each one of them is positioned
midway between two of the rollers 6 carried by the cage 5. In particular, it can readily
be appreciated in this connection that the number of rollers 8 will always be one
less than the number of rollers 6. This makes it possible to arrange matters in such
a way that the web material W will follow a general zig-zag course between the rollers
6 and 8 (as can be seen more readily from the perspective view reproduced in Figure
2), thus giving rise to a "festoon" of web material, i.e. a zig-zag section of web
wrapped round the rollers 6 and 8 that has a very considerable overall length as compared
with the space effectively occupied by the festoon.
[0027] The trolley 7 (and therefore also the rollers 8 mounted on it) can move along the
guide rails 4a under the action of the driving means 9, which - just like the other
driving and sensor organs subsequently to be described herein - are controlled by
a central processing unit 10, for example, a so-called PLC (acronym for "Programmable
Logic Controller"). The driving means 9, for example, can be an electric motor (of
known type and characteristics) that acts via an appropriate reduction gear 11 on
an endless screw 12 that engages with a female thread (not shown) provided on the
trolley 7.
[0028] By appropriately controlling the operation of the driving means 9 (in either one
or the other of the possible directions of rotation), the trolley 7 can therefore
be selectively lowered or raised (and therefore be brought either closer to the cage
5 or moved further away therefrom), which has the effect of varying the distance that
separates the set of rollers 6 mounted on the cage 5 from the set of rollers 8 carried
on the trolley 7. The said translatory movement of the trolley 7 thus makes possible
a selective variation of the length of the individual branches of the web festoon
formed between the rollers 6 and 8 and therefore also the overall length of web material
accumulated in the storage unit defined by the rollers 6 and 8.
[0029] With a view to clarifying ideas (though, naturally, without this being interpreted
as limiting the range of the invention), in the case of the storage unit here illustrated,
in which the web festoon consists of eight individual branches, a translatory movement
of the trolley 7 of the order of - for example - 1.5 m (or, to be more precise, 1.5625
m) will make it possible to vary the overall length of the stored web material by
1.5625 x 8 = 12.5 m. And this, be it noted, without thereby interfering in any way
with the actual mechanism that moves the web W from the intake side 2 to the output
side 3. Moreover, it will be readily appreciated that even when the web W at the intake
side 2 is brought ideally to a complete standstill, a lowering of the trolley 7 will
still ensure that a corresponding length of web material will issue from the output
side 3. The rate at which the web is paid out is determined by the translation speed
of the trolley 7 and therefore by the speed of rotation of the driving means.
[0030] Preferably, the driving means 9 - and therefore also the appropriate control commands
- are configured in such a way as to make it possible for the rollers 8 to descend
below the level of the rollers 6. Placing the trolley in this position at the moment
when the device 1 is initially prepared for operation, the web W can be made to pass
horizontally between the rollers 6 and the rollers 8, which in that position will
be situated, respectively, just above and just below the web. When the driving means
9 subsequently determine an upward movement of the rollers 8 to rise, this will automatically
cause the web to become disposed in the manner of a festoon.
[0031] Still referring to the perspective view in elevation reproduced as Figure 2, it will
be noted that the web material W enters the device 1 by passing over a series of rollers
that are here jointly indicated by the reference number 13. The said series of rollers
13 comprises at least one motor-operated roller 14 over which the web W has to pass
before it arrives, passing over one or more deflection rollers (such as the one here
indicated by reference number 15), at the intake side of the previously described
storage unit.
[0032] The roller 14 is operated, once again preferably via an appropriate reduction gear
16, by other driving means 17 substantially similar to the previously described driving
means 9 and likewise slave to the control unit 10.
[0033] On leaving the storage device 6, 8, the web W passes over one or more deflection
rollers 18, which must comprise at least one roller 19 performing the function of
a so-called "floating" or "jockey" roller. More particularly, the roller 19 in question
is mounted on a lever arm 20 capable of oscillating around a horizontal hinge pin
21 projecting from the supporting panel 4. The oscillating lever arm 20 should preferably
be subject to the balancing action of a counterweight or some similar return device
here indicated by the reference number 22. The latter should preferably act in the
sense of inducing the lever arm 20 to swing in the direction that will cause a slackening
of the loop of web material W that passes round the roller 19.
[0034] The reference number 23 indicates a position sensor (of a known type, which could
be - for example - a linear potentiometer or some similar device) capable of providing
the control unit 10 with a finely sensitive feedback signal that will enable the said
control unit to detect with considerable accuracy any difference between the speed
with which the web material W is fed into the intake side 3 of the device 1 and the
speed with which the said web is paid out after leaving the storage unit defined by
the rollers 6, 8.
[0035] It will therefore be appreciated that in the embodiment example here illustrated:
- the supporting panel 4 is on the whole of an elongated shape and carries the first
set of transmission means (the rollers 6) in the vicinity of the driving means 17
and the sensor means 19 to 23,
- the driving means 9 are situated at the opposite end of the supporting panel 4, and
- the second set of transmission means (the rollers 8) is mobile and arranged generically
in a position between the first set of transmission means (the rollers 6) and the
driving means 9.
[0036] The manner in which the device in accordance with the invention operates can be described
by supposing the starting condition of the system to be its normal steady operating
condition, which in the three diagrammes reproduced as Figures 3 to 5, where the time
scale is always indicated on the abscissa, is represented by the condition prevailing
immediately prior to the time t
1.
[0037] It will also be noted that in the said diagrammes the speed v
1 shown in Figure 3 corresponds to the speed at which the web material W passes over
the set of rollers 13 at the intake side 2 of the device 1 and, more particularly,
the motor-driven roller 14. In practical terms, this speed is determined by the speed
of rotation that the control unit 10 imposes on the driving means 17.
[0038] The diagramme reproduced as Figure 4, on the other hand, identifies the operating
speed that the said control unit 10 imposes on the driving means 9, i.e. the driving
means that move the trolley 7 up and down. More precisely, the speed v
2 shown in Figure 4 represents the speed with which, following operation of the driving
means 9, the web W is effectively paid out at the output side 3 of the device when
the intake speed v
1 is reduced to zero. In particular, it has here been assumed that immediately prior
to the time t
1 the trolley 7 is to be found in a position at some distance from the cage 5 (to be
quite clear: in the position indicated schematically by means of broken lines in Figure
1). In practice we here have a condition in which the storage unit defined by the
rollers 6 and 8 contains a rather substantial reserve of web material W. Naturally,
when the trolley 7 is kept in a fixed position, the driving means 9 are necessarily
at a standstill and its speed of rotation is zero (always refer to the part of Figure
4 immediately preceding the time t
1).
[0039] Lastly, the diagramme reproduced as Figure 5 represents the speed v
L at which the web material is paid out at the output side 3 of the device 1. The same
value of the ordinate is indicated by the chain-dotted line in Figures 3 and 4, thus
providing an immediate reference.
[0040] In the steady operating conditions just described, the driving means 9 are not running
and the speed v
L, at which the web issues from the output side of the device 1 depends solely on the
driving means 17. Naturally (and in a manner that is in itself known), the feedback
signal provided by the sensor 23 and generated by the so-called "jockey" roller 19
will make it possible to absorb any instantaneous speed fluctuations, since these
will become translated into a momentary variation of the position and orientation
of the lever arm 20.
[0041] In actual practice, whenever the feed rate of the material on the intake side of
the device drops accidentally below the speed at which it is paid out on the output
side, the roller 19 will rise, the lever arm 20 will rotate (in a clockwise direction
as seen when viewing the drawing) and this rotatory movement will be detected by the
control unit 10 via the feedback signal it receives from the sensor 23. The control
unit 10 will therefore arrange to step up the speed of the driving means 17 by such
small amount as may be required to absorb the displacement just described. A complementary
but functionally analogous operating sequence will take place whenever there occurs
a momentary deflection in the other direction (i.e. whenever the web feed rate on
the intake side exceeds the speed at which the material issues from the output side).
[0042] Put in other words, the described feedback mechanism aims at compensating accidental
differences between the input speed and the output speed, this in the sense of seeking
to keep the lever arm 20 always pointing in the same direction.
[0043] Let us now suppose that on account of some specific event (for example, because the
two rolls furnishing the web material have to be switched at the upstream station
and the two separate web lengths have therefore to be spliced while they are standing
still or moving at practically zero speed) the speed v
1 at which the web material is fed to the intake side of the device has to be reduced,
possibly to the point where it will momentarily be equal to zero. With this end in
view, the control unit 10 will impose a gradual slowdown of the speed of the driving
means 17, causing this speed to diminish very gradually, preferably in the manner
of a flat ramp, until it attains a minimum value (virtually equal to zero) at the
instant of time indicated by t
2.
[0044] In order to avoid this slowdown of the feed rate having repercussions on the payout
to the downstream station, the control unit 10 immediately activates the driving means
9 and thus causes the trolley 7 to move downwards and come closer to the cage 5. The
result of this movement is a gradual reduction of the length of web contained in the
storage device. This becomes necessarily translated into the stored web being paid
out to the output side 3 at a speed v
2, which can be selectively controlled (in a known manner, via the geometry of the
storage unit 6, 8) by the control unit 10 and in accordance with a ramp pattern that
is the exact counterpart (complement) of the ramp pattern in accordance with which
the feed rate on the intake side is being reduced.
[0045] The process just described is therefore such as to assure that the relationship
is always complied with.
[0046] More particularly, this is as true for the interval of time between t
1 and t
2 in which the driving means 17 are slowed down and the driving means 9 correspondingly
accelerated as it is for the interval of time between t
2 and t
3 when the driving means 17 are maintained at a constant (and possibly zero) speed
while the feed of web material W to the downstream station is
de facto assured to a very substantial (and possibly complete) extent by the gradual reduction
of the length of web stored between the rollers 6 and the rollers 8.
[0047] This operating mode is continued for the entire period of time in which the feed
of web material to the intake side of the device has to be minimized or completely
suspended (for example, to permit the two lengths of web material to be spliced in
standstill or substantial standstill conditions), that is to say, until the instant
of time indicated by t
3. At that moment of time (following a signal sent to the control unit 10, for example,
by the splicer S, along a line generically indicated in Figure 1 by L), the control
unit 10 will act on the two driving means 9 and 17 in accordance with the complementary
modalities described hereinabove and schematically illustrated in Figures 3 and 4
for the time intervals between t
3 and t
4. The speed v
1 at which web material is fed to the device (driving means 17) will thus be gradually
increased, so that it will be gradually brought up to its normal operating value (which
de facto corresponds to v
L), while the speed at which the trolley 7 is lowered will be gradually and complementarily
reduced until the trolley 7 (at the time t
4) is brought to a complete standstill in its lowermost position, at which point the
driving means 9 are also brought to a halt. The entire operation is performed while
complying with the previously cited relationship v
1 + v
2 = v
L.
[0048] At this point the system re-establishes the previously described steady operating
conditions (as prevailing immediately prior to the time t
1).
[0049] The previously described operating cycle can thus be repeated at any time thereafter
and whenever the need therefor arises.
[0050] Naturally, as soon as the steady operating conditions have been re-established, the
control unit 10 again acts on the driving means 9, causing them to rotate (but now
in the direction opposite to the one in which it rotated during the phase in which
the stored length of web material was paid out to the output side of the device),
so that the trolley 7 will now be gradually raised to its uppermost position, shown
by the dotted line in Figure 1, which has the effect of creating a new reserve of
web material within the storage device.
[0051] This operation of reconstituting the reserve can generally be carried out by operating
in a gradual manner and therefore at a slow speed, always preserving (just as in all
the other operating conditions of the storage device) the possibility of exercising
fine control over the web supply rate assured by the supply speed sensor, which (in
the embodiment here illustrated) is represented by the so-called "jockey" roller 19
mounted on the lever arm 20 and the various organs associated therewith. Any technician
skilled in the art will in any case realize that a wholly analogous feedback function
- based on the detection of a slackening or a shortening of a loop of web material
W - can also be obtained with equivalent devices (for example, a speed sensor of the
encoder type or similar devices).
[0052] The above description makes it clear that the various control phases that have just
been described - by reference to both the diagrammes reproduced in Figures 3 to 5
and the reconstitution of the reserve of web material W in the storage unit constituted
by the rollers 6 and 8 - can be realized by the control unit 10 on the basis of intervention
laws that can be selectively varied, especially between one phase and the next.
[0053] Furthermore, the device 1 in accordance with the invention is a completely self-contained
piece of equipment and can therefore perform its function no matter what type of web
handling and/or processing stations may be situated upstream and downstream of it.
[0054] In particular, the device in accordance with the invention can be combined with any
type of unwinding station and any type of splicer, quite irrespective of whether the
latter operates at zero speed or at full speed. As far as splicers of the zero speed
type are concerned, the device in accordance with the invention can be used both with
tape splicing systems and with splicing systems of the hot wire type. Moreover, the
device in accordance with the invention not only completely avoids tensile forces
acting on the web W, but also drastically reduces the accelerations to which the various
mechanical components of the system are subjected, including the set of parts (rollers
6 and 8 and the elements associated with them) that form the web reserve festoon.
[0055] Then located downstream of a web unwinding and splicing system, the device in accordance
with the invention can be used to dilate the braking and acceleration times of the
web rolls as compared with the corresponding times of the line they serve, and this
quite independently of the switchover phase. This may become necessary with unstable
rolls of raw material (for example, rolls having a very high ratio between diameter
and web width) or rolls having an extremely high moment of inertia.
[0056] More particularly, the device in accordance with the invention makes it possible
to modulate the deceleration, switchover and acceleration "ramps" to take due account
of the various parameters in play. In this connection it should be noted that the
straight-line pattern of the acceleration and deceleration ramps shown in Figures
3 and 4 are to be considered as purely exemplifying and can therefore be replaced
by any other pattern capable of being used for that purpose (for example, acceleration
and deceleration ramps of what is currently known as the "cos
2" type).
[0057] When the raw material to be handled is of considerable inertia (i.e. rolls of large
diameter and/or heavy material), the time of the deceleration ramp used to slow down
a dispensing roll about to become exhausted can be cut down, subsequently extending
the time of the acceleration ramp of the ready roll inserted to serve as the new source
of web material, so that the motors to be installed can be of more limited power and
reducing the probability of such harmful phenomena as roll decoring.
[0058] When it is desired to use a splicer S with a splicing system of the hot wire type,
it becomes more or less imperative to extend the duration of the switchover time (i.e.
the time during which the web material W at the intake side of the device 1 remains
standing still) to enable the splicer to cool the splicing area.
[0059] Furthermore, the device in accordance with the invention is particularly and almost
ideally suitable for retrofitting operations on existing installations, i.e. when
it is desired to improve the performance of an existing plant without extensive reconfiguration
interventions.
[0060] Without prejudice to the principle of the invention, of course, the design details
and the embodiment forms of the invention can be widely varied as compared with what
has here been described and illustrated without in any way going beyond the scope
of the invention as defined by the claims attached hereto. In this connection it will
readily be appreciated that the roller 19 (hereinabove referred to as "jockey" roller),
together with the other elements associated with it, could also be situated upstream
of the storage unit constituted by the rollers 6 and 8 and, more precisely, in a position
between the roller set 13 inclusive of the motor-driven roller 14 and the said storage
unit. This would still preserve the advantage deriving from the fact that the action
of detecting the web speed is based on the slackening or the shortening of a loop
formed by the web itself in substantial absence of tensile stresses applied to the
web material W.
1. A device for supplying web material (W), including:
- a storage unit (5 to 8) capable of accommodating a reserve length of the web material
(W) passing between an intake side (2) and an output side (3) of the device,
- first driving means (17) to control the speed of the web material (W) at the said
intake side (2),
- second driving means (9) acting on the said storage unit (5 to 8) to selectively
vary the said reserve length of the web material (W), the variation of the said reserve
length of the web material during the supply of this web material (W) producing a
variation of the speed of the web material (W) at the said output side (3) even when
the speed of the web material (W) at the intake side (2) remains unchanged,
- sensor means (19 to 23) capable of detecting the speed of the web material (W) and
generating an appropriate control signal, and
- control means (10) sensitive to the said signal and capable of acting on the said
first (17) and second (9) driving means in such a manner as to maintain the speed
of the web material (W) at the said output side at a predetermined level independently
of the speed of the web material (W) at the said intake side (2),
characterized in that the said sensor means (19 to 23) are capable of cooperating
in a winding relationship with a loop of the said web material (W) and generating
the said control signal as a function of the slackening or the shortening of the said
loop in substantial absence of tensile stresses applied to the said web material (W).
2. A device in accordance with Claim 1, characterized in that the said sensor means (19
to 23) are sensitive to the speed of the web material (W) at the said output side
(3) and the said control means (10) are configured for selectively controlling the
said second driving means (9) as a function of the speed imposed by the said first
driving means (17) on the said web material (W) at the said intake side (2).
3. A device in accordance with Claim 1 or Claim 2, characterized in that the said sensor
means include:
- a rotating lever arm (20) carrying a return means (19) for the said loop of web
material (W), so that both a slackening and a shortening of the said loop of web material
(W) will produce a rotation of the said lever arm (20), and
- detection means (23) sensitive to the rotation of the said lever arm (20) and capable
of generating the said control signal corresponding to the rotation of the said lever
arm (20).
4. A device in accordance with any one of Claims 1 to 3, characterized in that the said
sensor means (19 to 23) include an element (22) acting in the direction that induces
a slackening of the said loop of web material (W).
5. A device in accordance with any of the preceding claims, characterized in that the
said sensor means include a return means for the said loop of web material in the
form of a roller (19).
6. A device in accordance with any one of the preceding claims, characterized in that
it includes a supporting panel (4) that carries the said storage unit (5 to 8) as
a self-contained unit, together with the said first (17) and second (9) driving means.
7. A device in accordance with any one of the preceding claims, characterized in that
the said storage unit (5 to 8) includes a first (6) and a second (8) set of return
means on which the said web material (W) is wound in the general configuration of
a festoon, the said second driving means (9) acting in such a manner as to vary the
distance between the said first (6) and the said second (8) return means.
8. A device in accordance with Claim 7, characterized in that the said first (6) and
the said second (8) set consist of return means in the form of rollers.
9. A device in accordance with Claim 7 or Claim 8, characterized in that the return means
of the said second set (8) are mounted on an appropriate mobile trolley (7) and that
the said driving means (9) control the movement of the said mobile trolley (7).
10. A device in accordance with Claim 9, characterized in that it includes a supporting
panel (4) provided with means (4a) for guiding the movement of the trolley (7).
11. A device in accordance with Claim 10, characterized in that the said supporting panel
(4) is of an elongated shape, with the said first set of return means (6) positioned
in the vicinity of the said first driving means (17) and the said sensor means (19
to 23), that the said second driving means (9) is situated at the opposite end of
the supporting panel (4) and that the said second set of return means (8) is mobile
in a position generically intermediate between the said first return means (6) and
the said second driving means (9).
12. A device according to any one of the preceding claims, characterized in that the said
first (17) and second (9) driving means are electric motors.
13. A device according to any one of the preceding claims, characterized in that the said
control means (10) are configured to control the said first (17) and second (9) driving
means in at least one of the following operating phases:
- slowing down of the said first driving means (17), with a corresponding reduction
of the speed (v1) of the web material (W) at the said intake side (2) and activation of the said second
driving means (9) in the direction of rotation that produces a reduction of the length
of the web material (W) at a speed (v2) such as to maintain the speed of the web material (W) at the said output side (3)
at a substantially constant value (vL) independently of the speed reduction at the said intake side (2),
- acceleration of the said first driving means (17), with a corresponding increase
of the speed (v1) of the web material (W) at the said intake side (2) and activation of the said second
driving means (9) in the direction of rotation that produces a reduction of the said
length of web material (W) at a gradually decreasing speed (v2), so that the speed of the web material (W) at the said output side (3) is maintained
at a substantially constant value (vL) independently of the increase of the speed of the web material (W) at the said intake
side (2), and
- activation of the said second driving means (9) in the direction that will produce
an increase of the said length of web material (W) with a corresponding increase of
the speed of the said first driving means (17), so that the speed of the web material
(W) at the said output side (3) will be maintained constant and the reserve of web
material (W) contained in the said storage unit (5 to 8) will be reconstituted.
14. A device in accordance with Claim 13, characterized in that the said control means
(10) is configured in such a way as to realize the said phases, intervening on the
said first (17) and second (9) driving means in accordance with selectively variable
control laws.