[0001] This invention relates to a plastic film bonding machine according to the preamble
of claim 1.
[0002] Such a film bonding machine is known by prior use, wherein the intermediate roller
is mounted on supports which do not allow it to float in relation to the adjacent
rollers.
[0003] US-A-4 046 931 discloses an apparatus for applying coating compositions to strip
material, wherein a small diameter transfer roll is allowed to float in a direction
parallel to the line joining the centres of two deformable-covered rolls, but is restrained
from movement in a direction perpendicular thereto. In this way, the inter-roll loading
between the small diameter transfer roll and the two deformable-covered rolls can
be made approximately equal.
[0004] Currently known plastic film bonding apparatus basically comprises film feed systems
consisting of pay-out reels with suitable tensioning devices, systems designed to
spread a layer of adhesive on one of the two sheets of film, bonded systems and film
reeling systems.
[0005] This type of apparatus, an example of which is illustrated in Fig. 1, generally uses
solvent-based adhesive.
[0006] In the apparatus illustrated a layer of plastic film is conveyed from pay-out reel
1, fitted with suitable tensioning devices 2, to station 3, where systems of a known
type apply a layer of solvent with adhesive onto one side of the film.
[0007] The film next runs over roller unit 4 and is conveyed into furnace 5, where the solvent
is evaporated.
[0008] From furnace 5 the first sheet of film is sent to bonding station 6, where it is
bonded to a second sheet of film conveyed from pay-out reel 7, identical to reel 1.
[0009] The two bonded sheets of film are then reeled onto winding reel 8. Unfortunately,
the solvents used for the adhesive are highly pollutant, with the result that their
use is gradually declining, especially as pollution legislation is becoming increasingly
strict.
[0010] In recent years, machines which bond plastic film with solventless adhesive have
been introduced. However, while this system offers considerable advantages as it totally
eliminates the pollution and danger involved in solvent use, it also presents numerous
disadvantages, because the high viscosity of this type of adhesive makes it very difficult
to spread the exact amount evenly on the film.
[0011] To give some idea of the difficulties which may be encountered, it is sufficient
to note that the amount of adhesive used is approx. 0.8 - 1.5 grams per square metre
of film, and that during spreading the film moves at high speed, often as fast as
5-6 metres per second.
[0012] The problem which the technical expert faces thus consists in designing systems which
spread the exact amount of adhesive evenly and regularly while the film is moving.
[0013] Various systems have been devised for this purpose, but none of them wholly solves
the problem.
[0014] For example, some known machines comprise a pair of counter-rotating rollers, one
of which picks up the adhesive from a container; the adhesive sticks to the roller
surface and is proportioned by adjusting the distance between the rollers.
[0015] However, this system is imprecise, especially when minimal amounts of adhesive have
to be distributed on the surface of the film.
[0016] Other systems use a steel roller with a mechanically engraved surface containing
a number of cells which fill with adhesive.
[0017] A doctor blade placed in contact with the roller surface removes the excess adhesive,
so that when the film comes into contact with the roller it only takes up the adhesive
in the cells.
[0018] Once again, this system is not wholly satisfactory, especially as the amount of adhesive
applied depends on the size of the cells, so that the roller has to be replaced with
one containing cells of different sizes whenever the amount of adhesive distributed
on the surface unit is altered.
[0019] Other systems use a steel roller, partly immersed in the adhesive container and in
contact with a rubber roller which, when pressed against the former, distributes the
adhesive in a sufficiently thin layer.
[0020] Once again, this system does not entirely deal with the problem, as it does not guarantee
consistent results under all machine operating conditions.
[0021] As the roller rotation speed increases, the external rubber layer tends to buckle,
which alters the thickness of the layer of adhesive remaining on the roller, and therefore
the amount of adhesive distributed per film surface unit.
[0022] In some machines the adhesive is passed between several pairs of rollers with decreasing
clearances. The rollers are mounted on supports fitted with micrometer regulation
devices, and the distance between each roller and the next is measured by comparators.
This system, like those described above, does not satisfactorily meet the requirements
of the case, as it is extremely complicated and it is particularly difficult to maintain
the precision of the micrometer regulations when the machine gathers speed.
[0023] There is consequently a strongly felt need in the industry for systems which spread
solventless adhesive evenly onto film moving at high speed and guarantee consistent
results, especially at different film feed speeds.
[0024] US-A- 4 363 288 describes a film adhesive coating machine comprising:
- a pair of counter-rotating rollers (9, 19), designed to take up the adhesive in the
form of a thin layer of constant thickness
- a spreader roller (3) designed to apply the adhesive to one side of the film (1) as
it is fed through the machine
- intermediate rollers (11, 10) designed to take un the adhesive from the said counter-rotating
rollers (9, 19).
[0025] The before mentioned object is achieved according to the invention by the features
of claim 1.
[0026] This invention will now be described in detail by way of example and not of limitation,
with special reference to the annexed figures in which:
- Figure 2 contains a diagram of an apparatus in accordance with the invention
- Figure 3 shows a cross-section of the adhesive spreading systems
- Figure 4 shows a front view of the devices illustrated in Fig. 3
- Figs. 5 and 6 show a detail of the devices illustrated in Figs. 3 and 4.
[0027] In the apparatus according to the invention, a sheet of plastic film conveyed from
pay-out reel 9 passes through adhesive spreading devices (assembly 10) and is then
sent to bonding station 11, where it is bonded to a sheet of film conveyed from a
second pay-out reel 12.
[0028] The bonded film is then reeled onto winding reel 13.
[0029] The spreading unit consists of a pair of heated chrome-plated steel counter-rotating
rollers 14 and 15, chrome-plated steel spreader roller 16 and intermediate roller
17, which is kept pressed against rollers 15 and 16 by a pair of pneumatic pistons
or similar 18.
[0030] Roller 17 is mounted on a support which allows it to float slightly in relation to
adjacent rollers 15 and 16. The relative mechanisms are illustrated in Figs. 5 and
6.
[0031] Each end of the shaft of roller 17 is inserted into seating 22 in support element
23, which in turn runs in seating 32 in the shoulder of the machine.
[0032] Seating 22 is slightly larger than the shaft of roller 17, to allow a degree of shaft
play.
[0033] Each support 23 is connected to rod 34 of piston 18. Rod 34 contains a toothed part
35 which engages the corresponding teeth of a gear 36, also fitted to shoulders 41
of the machine using bearings 37, for example.
[0034] Shaft 38 connects gears 36, forcing them to rotate together. This causes supports
23 of roller 17 to move together, with the result that the roller axis always remains
basically parallel to its original position except for the slight play referred to
above.
[0035] As a result, roller 17 is kept pressed against adjacent rollers 15 and 16 with constant
elastic force due to the pressure to which pistons 18 are subjected, but is allowed
to float slightly to compensate automatically for any play or dimensional variations
in rollers 15 and 16.
[0036] Rollers 14, 15 and 17 are interconnected by reducers of a known type, such as the
pulley and worm screw type, so that they rotate at differing speeds in a constant
ratio.
[0037] Roller 15 rotates at a higher speed than roller 14, and roller 17 moves at a higher
speed than the preceding rollers.
[0038] Roller 15 has a fixed shaft, while roller 14 is mounted on a support which enables
the distance between it and roller 15 to be regulated.
[0039] These regulation systems are of known type, and are therefore not described in detail.
[0040] The machine also includes gravimeter 21 which returns roller 14 to its exact previous
position whenever it has to be moved, with no need for remeasurement.
[0041] The clearance between rollers 14 and 15 is a few hundredths of a millimetre.
[0042] A heated adhesive tank 19 is fitted above these rollers, and a collector tray 20
is fitted below them.
[0043] Rollers 14, 15 and 17 are activated by independent motor 27 (Fig. 4) and the motion
from pulleys 28 is transmitted to the roller shafts via Schmidt joints 29.
[0044] This system overcomes the problems due to the difference in size between the drive
assemblies and the rollers, eliminating the need to use shafts with universal joints,
which would considerably increase the size of the apparatus.
[0045] Spreader roller 16 is connected to the main motor of the machine via pulley 30.
[0046] A rubber idle presser roller 31 fitted above roller 16 keeps film 39 pressed against
the spreader roller to transfer the adhesive.
[0047] The width of rubber roller 17 is less than that of the film bonded; alternatively,
the central part of the rubber roller has a greater diameter, but is still less wide
than the film.
[0048] A pair of separator elements 40 consisting, for example, of walls made of teflon
or similar material, is inserted between rollers 14 and 15. The shape of the separators
is complementary to that of the rollers, and they can be slid along a pair of support
guides.
[0049] The separators serve to delineate the width of the layer of glue picked up by the
rollers.
[0050] This system is designed to ensure that the glue is not squeezed from the sides of
the film and depsited on the roller surface as a result of the pressure exerted by
roller 31 during bonding, as this would slow the roller speed and compromise the operation
of the entire apparatus.
[0051] Spreader roller 16 and rubber presser roller 31 are wider than the film bonded.
[0052] As the surface of plastic film has a very low friction coefficient, roller 31 tends
to skid slightly in relation to the upper film. If this is not prevented, the upper
film would be fed through the machine at a slightly lower speed than the film below,
producing a difference in tension between the two layers and causing the bonded film
to roll up.
[0053] If, however, rollers 16 and 31 are wider than the film, they will advance at perfectly
synchronized speeds due to the rubber/steel contact between the ends of the two rollers,
thus ensuring that both layers of film are fed through the machine simultaneously.
[0054] The machine operates as follows:
The apparatus is first set up by suitably regulating the clearance between steel rollers
14 and 15 and activating piston 18 to bring rubber roller 17 against rollers 15 and
16.
[0055] Screw 26, which constitutes an adjustable travel stop for support arm 24 of roller
17, is then regulated to distance the said roller slightly from the preceding ones.
[0056] Under these circumstances, screw 26 constitutes a stop which limits the movements
of roller 17, preventing it from coming too close to rollers 15 and 16, and thus ensuring
that it is not "sucked in" during movement due to buckling of the rubber layer.
[0057] Roller 17 is therefore kept pressed against rollers 15 and 16 with constant elastic
force produced by the pressure applied to pneumatic cylinder 18, but is unable to
come too close to them even when the rubber layer tends to buckle as the rotation
speed increases, which would cause the drawbacks described above.
[0058] At this point the film is inserted between presser roller 31 and spreader roller
16, the heating of the steel rollers and the adhesive contained in tank 19 is switched
on, and the machine can be started up.
[0059] The film conveyed from pay-out reel 9 passes between rollers 16 and 31 and is then
sent to bonding station 11.
[0060] Devices of known type pick up a quantity of adhesive from tank 19 and drop it into
the space between rollers 14 and 15 and separators 40.
[0061] A thin layer of this adhesive, depending on the clearance between the said rollers,
adheres to roller 15 and is distributed over its surface, partly because this roller
rotates faster than the preceding one.
[0062] The layer of adhesive is picked up by roller 17, which deposits it on spreader roller
16.
[0063] As mentioned, each of these rollers rotates faster than the preceding one, with the
result that the layer of adhesive is distributed more and more thinly.
[0064] On the basis of a few tests, an expert in the field can easily determine the ideal
clearance between rollers 14 and 15 and the ratio between the speeds of rollers 14,
15 and 17 and spreader roller 16, depending on the type of adhesive and the type of
film used.
[0065] For example, if polypropylene film is fed through the machine at a speed of 4.2 metres
per second and an adhesive such as ADCOTE (Comochem trademark) is used, the clearance
between rollers 14 and 15 is eight-hundredths of a millimetre, the ratios between
the speeds of rollers 14, 15 and 16 are 1:80:100 with roller 14 rotating at a surface
speed of approx. 10 cm per sec., and the spreader roller moves at the speed of 4.5
m/sec.
[0066] The machine also contains devices of known type which synchronise the speed of secondary
motor 27 with that of the main motor of the machine so as to maintain a constant ratio
between the speed of roller 16 and the speeds of the remaining rollers.
1. Plastic film bonding machine with adhesive spreading systems, of the kind comprising:
- a pair of counter-rotating rollers (14, 15) designed to take up the adhesive in
the form of a thin layer of constant thickness
- a spreader roller (16) designed to apply the adhesive to one side of the film (39)
as it is fed through the machine
- an intermediate roller (17) designed to take up the adhesive from the said counter-rotating
rollers (14-15) and spread it on the said spreader roller (16),
- means for rotating each of the said rollers at a higher speed than the preceding
one, the spreader roller (16) having a surface speed equal to the film feeding speed,
characterised by the fact that:
the said intermediate roller (17) is mounted on supports designed to allow it to float
slightly in all radial directions in relation to adjacent rollers (15) and (16).
2. Plastic film bonding machine in accordance with claim 1, characterised by the fact
that it contains presser means (18, 34, 23) designed to bring the said intermediate
roller (17) against said roller (15) and said spreader roller (16) with a constant
force, and includes adjustable travel stop means (26) designed to limit the movements
of the said intermediate roller (17) so as to prevent it from coming too close to
the remaining rollers.
3. Plastic film bonding machine in accordance with claim 2, wherein said stop means are
constituted by a screw (26) in the support arm (24) of roller (17).
4. Plastic film bonding machine in accordance with claim 2, in which the said means bringing
said roller (17) against roller (15) and spreading roller (16) consist of a pair of
pneumatic pistons (18) whose rods 35 are connected to the shaft of the said intermediate
roller.
5. Plastic film bonding machine according to claim 4, wherein said rods (34) of pistons
(18) have toothed parts (35) engaging gears (36) connected by a shaft (38) fitted
to the shoulders of the machine.
6. Plastic film bonding machine in accordance with the above claims, characterised by
the fact that the counter-rotating rollers (14, 15) and the spreader roller (16) are
heated and made of chrome-plated steel, and the intermediate roller (17) is covered
with rubber.
7. Plastic film bonding machine in accordance with the previous claims, characterised
by the fact that it uses schmidt joints to transmit motion to the counter-rotating
and spreader rollers (14, 15, 16).
8. Plastic film bonding machine in accordance with claim 1, characterised by the fact
that the width of the said intermediate roller (17) is less than that of the film
bonded.
9. Plastic film bonding machine in accordance with claim 1, characterised by the fact
of providing a pair of separator elements (40) inserted between rollers (14) and (15),
said separator elements being movable along a support guides and having a shape which
is complementary to that of the rollers.
1. Vorrichtung zum Verkleben einer Kunststoffolie mit Klebstoffverteileinrichtungen,
umfassend
- ein Paar von gegeneinander drehenden Walzen (14, 15) zur Aufnahme des Klebstoffs
in der Form einer dünnen Schicht von konstanter Dicke,
- eine Verteilerwalze (16) zum Aufbringen des Klebstoffs auf einer Seite der Folie
(39) während ihres Durchlaufs durch die Vorrichtung,
- eine Zwischenwalze (17) zur Aufnahme des Klebstoffs von den gegeneinander drehenden
Walzen (14, 15) und zum Verteilen des Klebstoffs auf der Verteilerwalze (16);
- Einrichtungen zum Drehen jeder der Walzen mit einer höheren Geschwindigkeit als
die vorausgehende Walze, wobei die Verteilerwalze (16) eine Oberflächengeschwindigkeit
gleich der Folienlaufgeschwindigkeit hat,
dadurch gekennzeichnet,
daß die Zwischenwalze (17) auf Trägern montiert ist, die es ihr ermöglichen, in alle
radiale Richtungen relativ zu den angrenzenden Walzen (15) und (16) etwas zu schwimmen.
2. Vorrichtung zum Verkleben einer Kunststoffolie nach Anspruch 1, dadurch gekennzeichnet,
daß eine Andrückeinrichtung (18, 34, 23) vorgesehen ist, um die Zwischenwalze (17)
an der Walze (15) und der Verteilerwalze (16) mit einer konstanten Kraft anzudrücken,
und eine einstellbare Anschlageinrichtung (26) vorgesehen ist, um die Bewegung der
Zwischenwalze (17) zu begrenzen, so daß verhindert wird, daß sie zu dicht an die verbleibenden
Walzen heranbewegt wird.
3. Vorrichtung zum Verkleben einer Kunststoffolie nach Anspruch 2, wobei die Anschlageinrichtung
durch eine Schraube (26) in dem Trägerarm (24) der Walze (17) ausgebildet ist.
4. Vorrichtung zum Verkleben einer Kunststoffolie nach Anspruch 2, wobei die Einrichtung,
die die Walze (17) an der Walze (15) und der Verteilerwalze (16) zur Anlage bringt,
aus einem Paar von pneumatischen Kolben (18) besteht, deren Kolbenstangen (34) mit
der Welle der Zwischenwalze verbunden sind.
5. Vorrichtung zum Verkleben einer Kunststoffolie nach Anspruch 4, wobei die Kolbenstangen
(34) der Kolben (18) gezahnte Abschnitte (35) aufweisen, die mit Zahnrädern (36) in
Eingriff stehen, die durch eine Welle (38) verbunden sind, die auf den Schultern der
Vorrichtung aufgesetzt ist.
6. Vorrichtung zum Verkleben einer Kunststoffolie nach den vorausgehenden Ansprüchen,
dadurch gekennzeichnet, daß die gegeneinander drehenden Walzen (14, 15) und die Verteilerwalze
(16) beheizt sind und aus chromplattiertem Stahl bestehen, wobei die Zwischenwalze
(17) mit Gummi beschichtet ist.
7. Vorrichtung zum Verkleben einer Kunststoffolie nach den vorausgehenden Ansprüchen,
dadurch gekennzeichnet, daß Schmidt-Verbindungen vorgesehen sind, um die Bewegung
der gegeneinander drehenden Walzen und der Verteilerwalze (14, 15, 16) zu übertragen.
8. Vorrichtung zum Verkleben einer Kunststoffolie nach Anspruch 1, dadurch gekennzeichnet,
daß die Breite der Zwischenwalze (17) kleiner ist als die der zu verklebenden Folie.
9. Vorrichtung zum Verkleben einer Kunststoffolie nach Anspruch 1, dadurch gekennzeichnet,
daß ein Paar von Separatorelementen (40) zwischen die Walzen (14) und (15) eingesetzt
ist, wobei die Separatorelemente längs einer Trägerführung beweglich sind und eine
Form haben, die komplementär ist zu der der Walzen.
1. Machine de collage de films en matière plastique pourvue de systèmes d'étalement de
matière adhésive, du genre comportant:
- une paire de rouleaux (14, 15) tournant en sens opposés conçus pour entraîner par
enroulement la matière adhésive sous la configuration d'une couche mince d'épaisseur
constante
- un rouleau (16) formant dispositif d'étalement conçu pour appliquer la matière adhésive
sur un seul côté du film (39) à mesure qu'il est amené à travers la machine
- un rouleau intermédiaire (17) conçu pour entraîner par enroulement la matière adhésive
à partir desdits rouleaux tournant en sens opposés (14, 15) et pour l'étaler sur ledit
rouleau formant dispositif d'étalement (16),
- des moyens pour faire tourner chacun desdits rouleaux à une vitesse plus élevée
que le rouleau qui précède, le rouleau formant dispositif d'étalement (16) ayant une
vitesse superficielle égale à la vitesse d'amenée du film,
caractérisé par le fait que:
ledit rouleau intermédiaire (17) est monté sur des supports conçus pour lui permettre
de flotter légèrement en tous directions radiales, par rapport aux rouleaux adjacents
(15) et (16).
2. Machine de collage de films en matière plastique selon la revendication 1, caractérisée
par le fait qu'elle contient des moyens (18, 34, 23) formant dispositif de pressage
conçus pour amener ledit rouleau intermédiaire (17) contre ledit rouleau (15) et ledit
rouleau (16) formant dispositif d'étalement avec une force constante, et qu'elle comprend
un moyen réglable (26) d'arrêt de course conçu pour imiter les déplacements dudit
rouleau intermédiaire (17) de façon à l'empêcher de venir trop près des rouleaux restants.
3. Machine de collage de films en matière plastique selon la revendication 2, dans laquelle
ledit moyen d'arrêt est constitué par une vis (26) située dans le bras de support
(24) du rouleau (17).
4. Machine de collage de films en matière plastique selon la revendication 2, dans laquelle
lesdits moyens amenant ledit rouleau (17) contre le rouleau (15) et le rouleau d'étalement
(16) consistent en une paire de pistons pneumatiques (18) dont les tiges (34) sont
raccordées à l'arbre dudit rouleau intermédiaire.
5. Machine de collage de films en matière plastique selon la revendication 4, dans laquelle
lesdites tiges (34) des pistons (18) possèdent des parties dentelées (35) engrenant
des pignons (36) raccordés par un arbre (38) ajusté sur les contreforts de la machine.
6. Machine de collage de films en matière plastique selon les revendications ci-dessus,
caractérisée par le fait que les rouleaux (14, 15) tournant en sens opposés et le
rouleau (16) formant dispositif d'étalement sont chauffés et sont faits d'acier chromé,
et que le rouleau intermédiaire (17) est recouvert de caoutchouc.
7. Machine de collage de films en matière plastique selon les revendications précédentes,
caractérisée par le fait qu'elle utilise des joints schmidt afin de transmettre les
mouvements aux rouleaux tournant en sens opposés et au rouleau formant dispositif
d'étalement (14, 15, 16).
8. Machine de collage de films en matière plastique selon la revendication 1, caractérisée
par le fait que la largeur dudit rouleau intermédiaire (17) est plus petite que celle
du film collé.
9. Machine de collage de films en matière plastique selon la revendication 1, caractérisée
par le fait qu'elle contient des éléments (40) formant séparateurs insérés entre les
rouleaux (14)met (15), lesdits éléments séparateurs étant mobiles le long de guides
de support et ayant une forme complémentaire de celle des rouleaux.