Note: Descriptions are shown in the official language in which they were submitted.
2~ 80~62
9th November 1995
Apparatus and roller for the coating of rotationally
symmetrical mouldings
DESCRIPTION
The invention relates to an apparatus and a
roller for the coating of the outer surface of
rotationally symmetrical mouldings, especially bottles,
and to a correspon~; ng method.
Variou6 apparatuses for the coating of bottles
with flowable material, for example plastic, are already
known. In this respect, reference is made representa-
tively to DE-A-28 30 316 and the publications mentioned
in this. By means of the injection-moulding or casting
head known from DE-A-28 30 316, it is to be possible to
guarantee accurate uniform coating of the bottles.
To apply fluids to bottles, special machines,
with their own drive and with a star feeder moving the
bottles on a path in the form of an arc of a circle, are
already known. An apparatus of this type is described by
way of example in EP-A-0 452 943. In this known appar-
atus, the bottles in the star feeder are set in natural
rotation by rolling on a fixed friction segment and at
the same time are subjected to the fluid. This fluid is
applied especially for the purpose of covering the
chafings, occurring after several recyclings in the case
of returnable bottles, as well as other splinterings and
scratches on the cylindrical bottle body and of giving
the bottles the appearance of being as new.
Apparatuse~ are also already known, for example
from US-A-4 586 458, in which fluid from an injection
nozzle moving relative to an applicator element is
transferred by means of intermediate rollers.
In the drinks industry, there is now a need for
the hollow bodies necessary for packaging, especially
glass bottles in the non-returnable and returnable
sector, to be made increasingly lighter, in order to save
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costs of material and of transport. However, the walls of
bottles of this kind cannot be made as thin as desired,
since this entails considerable risks. Thus, for example,
bottles filled with drinks containing CO2 are exposed to
sustained internal pressure by the filling media. If the
surface of a thin-walled bottle is damaged, then
pressurized bottles of this type may easily burst. This
may lead to unforeseeable product liability claims.
In addition, the outer surface of returnable
bottles is normally damaged and scratched during cleAn;ng
and filling. Since glass as a material has the property
that its stability is influenced primarily by the state
of the surface, a pressurized gla~s bottle may burst,
etc. even when the damage to the surface is only slight.
It is already known to provide bottles with an
outer coating which protects the surface of the bottle
against damage during the filling operation, etc. and
which "can hold together" the shape of even a splintered
bottle. A product sold by Huls AG under the brand name
"Vesticoat" and described in DE-A-29 38 309 or EP-A-0 025
932 and DE-A-29 38 229 or EP 0 025 994 can be used as a
coating material of this type. By employing materials of
this kind, it is possible to use more thin-walled and
therefore lighter bottles which are even more reliable
than the uncoated glass bottles known hitherto.
These known flowable coating materials are
solvent-free for reasons of environmental protection. The
disadvantage of this is that these coating materials have
relatively high viscosity and cannot be applied simply by
injection, dipping or casting. These high-viscosity
coating materials are therefore, at the present time,
applied in extruded form through a casting or injection
head onto the bottle to be coated itself and are then
distributed or levelled off by blowing, or also by
downstream rolls, on the outer surface of the bottle to
be coated. In this respect, it is also known to apply the
plastic extrusions to a roll and to transfer these by
means of this onto the outer surface of the bottle to be
coated. In this known technique, therefore, the bottle
21809~2
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held rotatably at its head and at its bottom is rotated;
the said roll or roller is brought to bear on this
rotated bottle and is kept in contact with the bottle for
some time, 80 that the coating material is distributed on
the bottle surface. These rollers used hitherto had a
purely cylindrical shape. On account of this, the coating
material was not distributed uniformly over the surface
of the bottle. Losses and defective coatings consequently
occurred. Moreover, the coated bottles often did not
satisfy the quality criteria placed on them.
The object of the invention is, therefore, to
provide an apparatus, a roller and a method, by means of
which high-viscosity solvent-free coating materials can
be applied to mouldings reliably, uniformly and
reproducibly.
This object is achieved by means of the teaching
of the claims.
The apparatus according to the invention, like
the apparatuses known hitherto, possesses a device for
transporting and rotatably holding the mouldings to be
coated. This device is referred to below as a transport
device. Furthermore, the apparatus according to the
invention is equipped with a sprinkler head for the
coating material and with at least one rotatable roller
which can be pressed onto the moulding to be coated and
which can be lifted off again. The axis of rotation of
the roller, in the pressed-on state, is arranged at least
essentially parallel to the axis of rotation of the
moulding to be coated and serves for distributing the
coating material on the outer surface of the moulding.
This roller, after distributing the coating material, is
moved away from the moulding. The coating material
distributed on the moulding is then cured in a way known
per se, 80 that a protective outer layer or coating
forms.
The high-viscosity solvent-free coating systems
or lacquer systems employed in this case are especially
those with a viscosity of 40,000 mps at approximately
10C up to 1,000 mps at approximately 100C, especially
2 1 80962
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30,000 mps at 20C to 5,000 mps at 70C.
The expression "rotationally symmetrical" used
here is not to be understood in the strictly mathematical
sense. According to the invention, mouldings which
deviate slightly from rotational symmetry can also be
coated.
The inventive essence of the present invention i8
that the roller for distributing the coating material
possesses an outer contour shaped complementarily to the
outer contour of the moulding. In other words, the
profile of the roller represents the negative profile of
the moulding to be coated. It may also be said that, in
the region in which the moulding and roller come into
contact, the lateral profile line of the moulding pro-
jected onto a plane coincides approximately with thelateral profile line of the roller likewise projected
onto a plane. This criterion can be satisfied even when
the moulding and roller have different dimensions, in
which case the roller and moulding can rotate at differ-
ent speeds. According to a preferred embodiment, however,the roller and moulding have comparable or similar
dimensions. Nore specifically, this means that the sum of
the radius of the roller and the radius of the moulding
results, at any point along the longit~ n~l axis or axis
or rotation, in approximately the same value which
corresponds approximately to the distance between the two
axes of rotation in that state in which the moulding and
roller are pressed on one another. It could also be said
that the roller has the rotationally symmetrical negative
shape of the moulding to be coated or that the roller
represents, in relation to the axis of rotation, the
rotationally symmetrical complementary shape of the
moulding to be coated.
The subject of the invention is therefore also
a roller of this type for the coating of the outer
surface of rotationally symmetrical mouldings.
By virtue of the shape of the roller according to
the invention, it is possible for high-viscosity coating
materials to be distributed uniformly, at high production
21 80962
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speeds, onto glass hollow bodies to be coated, 80 that,
after curing, a homogeneous, uniformly distributed
coating is obtained. In this case, the high-viscosity
coating materials employed are expediently processed at
an operating temperature of 30-100C, especially at
40-60C, or are heated to this temperature.
According to an P~hodiment which is also pre-
ferred, in the apparatus according to the invention, the
sprinkler head is arranged in such a way that the coating
material iB first applied to the roller and is then
transferred, either staggered in time or simultaneously,
onto the moulding by means of this roller. In this case,
the sprinkler head or applicator device used can be any
known device used for this purpose, for example casting
strip, nozzle, etc. Expediently, however, the coating
material is applied to the roller as long as the roller
is not yet in contact with the moulding to be coated.
Moreover, the apparatus according to the inven-
tion expediently has a metering device known per se. By
means of this metering device, an individually adjustable
specific quantity of coating material can be applied from
a correspo~;ng casting strip onto different regions of
the roller in each case via individual combined nozzles,
80 that as uniform a distribution as possible can take
place. This metering device can also be designed and
controlled in such a way that different quantities of
coating material are applied to different regions of the
roller simultaneously.
In the apparatus according to the invention, at
least either the moulding or the roller is positively
rotated. If the moulding is positively rotated, then the
roller is positively rotated in the opposite direction
when the moulding comes to bear on it. The same applies
conversely if the roller is positively rotated. The
moulding and roller are preferably positively rotated in
opposition, especially at the same rotational speed. If
the coating material is applied first to the roller, then
the roller and the moulding to be coated are kept in
contact until the coating material used is transferred in
- - 2 1 80962
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sufficient quantity or completely.
According to an embodiment which is also pre-
ferred, the roller according to the invention possesses
an inelastic core and an elastic transfer material
applied to the outside of the latter. In this case, the
core can be a cylinder; in this case, the transfer
material is "responsible" for the outer contour or for
the external shape of the roller. The thickness of the
transfer material therefore also changes according to the
variation, along the longitll~;n~l axis, in the shape of
the moulding to be coated.
According to an embodiment which is also pre-
ferred, the elastic transfer material has approximately
the same layer thickness over the entire length. In this
case, the shape of the core is approximately the comple-
mentary shape of the moulding to be coated.
In the two embodiments last described, the core
can possess, on its outer generated surface, a plurality
of radially continuous grooves, into which radially
inward-projecting beads of the transfer material engage,
so that an axial displacement of transfer material
relative to the core is prevented.
It is also possible, of course, for the core to
possess beads which are radially continuous on the
outside and which engage into continuous grooves cut out
in the transfer material. The core expediently possesses
a central continuous bore, concentric to the axis of
rotation, for receiving a bearing shaft, etc.
The transfer material can be open-pored and
consist of sponge rubber, foamed plastics or fibrous
natural products, for example lambskin. Furthermore, the
transfer material can be closed-pored and be composed of
sponge rubber, types of caoutchouc and foamed plastics,
especially EPDM and polyurethane plastics. The composi-
tion of the transfer material and, of course, also of thecore is expediently to be selected in such a way that it
is compatible with the coating materials, does not swell
and is also not chemically attacked. Thus, for example,
there should be compatibility towards coating materials
- 2~096~
based on formulations of polyurethane, acrylate, epoxy
and synthetic resin. Moreover, the transfer material
should withstand mechanical stresses for as long as
possible.
The rotationally symmetrical core of the roller
can consist of wood, plastics and metals, especially
aluminium or steel of any quality.
On account of the fact that the roller is con-
structed from a core and a transfer material, the trans-
fer material can be eliminated and renewed according to
fixed criteria of use or of wear, 80 that the require-
ments in terms of the uniformity of distribution of the
coating material are fulfilled.
The transfer material expediently has a thickness
15 of l to 100 mm, especially 30 mm. Especially when the
transfer material has a uniform layer thickness over the
entire length, as uniform a pressing force as possible
and therefore also as good a distribution of the coating
material as possible are afforded.
All transport devices known hitherto can be used
as a transport device of the apparatus according to the
invention. Preferably, however, the transport device
serves for the simultaneous transport of a plurality of
approximately uniformly spaced mouldings. A transport
device of this type can, for example, be a star feeder or
a similar device. Preferably, however, the transport
device is a conventional conveyor chain, in which the
mouldings to be coated are held rotatably 80 as to lie
horizontally and at the same time be spaced from one
another.
The apparatus according to the invention prefer-
ably has a plurality of rollers for the simultaneous
coating of a number of mouldings corresponding to the
n-~mher of rollers. In this case, the mutual spacing of
the rollers corresponds approximately to the mutual
spacing of the mouldings in the transport device. In this
case, the rollers are preferably held in a lifting
carriage which, starting from an initial position, is
moved in the direction of the transport device in such a
- 2 1 80962
-
way that the rollers are pressed approximately simulta-
neously onto the mouldings to be coated. In this pressed-
on state, the lifting carriage is then moved at the same
speed as the transport device and parallel to this
transport device, 80 that the rollers are kept pressed
against the mouldings. After a predetermined distance or
after a predetermined time, the lifting carriage together
with the rollers is lifted off from the mouldings and
returns to its initial position again.
This lifting carriage is equipped with at least
one sprinkler head having, for example, a casting strip.
If there is only one sprinkler head, this must be moved
up and down in such a way that, during a cycle, each
roller is provided with a ~ufficient coating quantity. In
this case, the coating quantity is preferably transferred
onto the roller in the time interval in which the roller
is not in bearing contact on the mouldings.
Preferably, however, the lifting carriage is
equipped with a nl~her of sprinkler heads correspon~; ng
to the number of rollers. In this case, these sprinkler
heads are arranged stationarily relative to the lifting
carriage. In other words, each roller is assigned its own
sprinkler head.
According to an embodiment which i6 also pre-
ferred, the rollers are held rotatably on a revolvingendless chain. This endless chain iæ guided in such a way
that a plurality of rollers are simultaneously held in
bearing contact on the mouldings assigned to them and are
moved at the speed of the transport device parallel to
the latter. This endless chain is guided approximately in
the same way as the chain of a crawler tractor.
It was ætated above that the mouldingæ or bottleæ
to be coated are held rotatably both at the head and at
the bottom in the transport device. This two-sided
holding is necessitated primarily by the fact that, when
the roller is pressed on, it is necessary, on account of
the high-viscosity coating material, to exert an
appreciable pressure which must, of course, be absorbed
by the means of holding the bottle.
2 1 80q6~
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It may also be necessary, in the effort to save
further weight, to coat the bottom of a bottle. In this
case, it is possible to mount the bottle in the transport
device at the head only, for example by means of an
exp~n~;ng mandrel engaging into the bottle mouth. How-
ever, if a roller described here were to be pressed onto
a bottle mounted in this way, there would be a great risk
that the bottle neck would break off.
In order to counteract this risk, according to a
preferred embodiment, the apparatus according to the
invention is equipped with at least one supporting roller
which is arranged opposite the roller for distributing
the coating material and which, at least in that region
in which the roller is pressed against the bottle to be
coated, is likewise pressed from the opposite side onto
the bottle to be coated, 80 that only slight loads occur
on the mouthpiece at the point where the bottle is held.
This supporting roller must, of course, be guided and
moved, parallel to the bottle to be coated, at the same
speed as the transport device and as the roller which
serves for distributing the coating material.
When the roller for distributing the coating
material is brought to bear from above against the bottle
to be coated, the said supporting roller is, of course,
pressed from below virtually as an abutment against the
bottle to be coated. The supporting roller too must, of
course, be mounted rotatably.
A conventional cylindrical roller can be employed
as a supporting roller. Expediently, however, this
supporting roller has the same shape as the roller for
distributing the coating material.
According to an embodiment which iR also pre-
ferred, a plurality of, especially two supporting rollers
located next to one another are provided, the lateral
spacing of the two supporting rollers being selected in
such a way that they form a kind of bed or bearing for
the bottle to be coated. The lateral spacing of the
mutually confronting outer generated surfaces of the
supporting rollers is therefore smaller than the diameter
2 1 80962
- 10 -
of the bottle to be coated. In other words, if, as seen
in the direction of the axes of rotation, the axis of
rotation of the roller for distributing the coating
material is connected to the axis of rotation of the
bottle and this i8 in turn connected to the two axes of
rotation of the supporting rollers, then a Y iæ obtained,
this Y preferably "st~n~;ng on its head". In this caæe
too, the supporting rollers can be shaped in respect of
their outer contour in the same way as the roller for
distributing the coating material.
The invention is explained in more detail below
by means of figures representing the preferred embodi-
ments. Of the figures:
Figures 1 to 3 each show a side view of a bottle to be
coated and a section through the associ-
ated roller of complementary shape
according to the invention;
Figure 4 shows a sketched functional representa-
tion of the apparatus according to the
invention with a lifting carriage having
a plurality of rollers and sprinkler
heads;
Figure 5 shows a representation correspo~; ng to
that of Figure 4, but with only one
sprinkler head;
Figure 6 shows a representation corresponding to
that of Figure 4, but in which the
rollers are held on a revolving endless
chain;
30 Figure 7 shows a representation corresponding to
that of Figure 6, but in which there are
only two sprinkler heads; and
Figure 8 shows a perspective view of a moulding to
be coated, with an associated roller and
an assigned sprinkler head.
In Figure 4, a transport device 2, here a trans-
port chain, of the apparatus according to the invention
is shown in greatly simplified sketched form. A transport
chain 2 of this type is known. The mouldings, here
2 1 ~09~2
11
bottles 3, to be coated are held horizontally and are
arranged parallel to one another at an approximately
equal spacing. At the same time, the bottles are held at
the head and at the bottom, for the bottles have a suffi-
cient wall thicknes6 in these regions, 80 that these
regions do not have to be coated. The bottles 3 can be
rotated about their longitl~; n;-l axis.
The lifting carriage 5 shown in Figure 4 is
equipped with four rollers 4 which are described in more
detail further below. These rollers 4 are at a mutual
spacing which corresponds to the mutual spacing of the
bottles 3. Each of the rollers 4 is equipped with a
separate sprinkler head 6, through which the coating
material is applied in metered quantity onto the associ-
ated roller 4.
The lifting carriage 5 can execute both a
translational to-and-fro movement and a lifting movement
according to the arrows shown in Figure 5. To carry out
the coating operation, the lifting carriage is brought
from an initial position (not shown), in which the
rollers 4 and bottles 3 are not in contact with one
another, into the position shown in Figure 4. From there,
the lifting carriage 5 is moved parallel to the transport
chain 2 and at the same speed in the direction of the
arrow pointing to the right. At the same time, the
coating material applied to the rollers 4 is transferred
onto the bottles 3 and distributed on their outer sur-
face. In this case, the bottles 3 and the rollers 4 are
both positively rotated in opposition.
After a predetermined time or after a predeter-
mined distance, the lifting carriage is raised and
returns to its initial position (not shown). During this
cycle of movement, the coating material is applied in
metered quantity onto the rollers 4 which continue to be
rotated.
The mouldings and rollers employed in this case
can have the shapes shown in Figures 1 to 3. As emerges
from these Figures, the outer contour 8 of the roller 4
according to the invention has a shape complementary to
21 80q~
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the outer contour 9 of the bottle 3. In this case, the
sum of the radius a (see Figure 1) of the bottle 3 and
the radius b of the roller 4 is equal to the distance
between the longitn~;n~l axis of the bottle 10 and the
longitl-~;n~l axis 11 of the roller 4 in the pressed-on
state. In other words, the sum of a and b corresponds to
the sum of x and y of Figure 1, but it is assumed, in
this case, that the transfer material 12 of the roller 4
is not compressed in the pressed-on state. However, this
is so in actual fact. The above calculations therefore
relate to the state in which the roller 4 is pressed onto
the bottle 3 without any compression of the transfer
material 12. During the actual coating operation,
however, the transfer material 12 is compressed slightly.
The roller 4 according to the invention and the
bottle 3 are held rotatably and mounted on their two end
faces. The devices necessary for this purpose are known
and are therefore not shown.
The roller 4 possesses a hollow-cylindrical core
13 which is surrounded on the outside by the transfer
material 12. The core 13 possesses, on its outer gener-
ated surface, a plurality of radially continuous grooves
14, into which radially inward-projecting beads 15 of the
transfer material 12 engage.
In the embodiment shown in Figure 2, the core 13
is virtually the cause of the negative shape of the
roller 4. This core 13 carries, on its outer generated
surface, the transfer material 12 which has approximately
the same layer thickness along the longitudinal axis 11.
This uniform layer thickness guarantees that the pressing
force and consequently also the distribution of the
coating material are approximately the same over the
entire outer surface of the bottle 3.
The representation shown in Figure 5 corresponds
essentially to the representation of Figure 4. The
difference is that, in the embodiment shown in Figure 5,
there is only one sprinkler head 6 which is moved to and
fro, so that the coating material is applied to all four
rollers 4. The sprinkler head 6 is thus movable to and
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_ - 13 -
fro relative to the lifting carriage (not shown).
The representation shown in Figure 6 also corre-
sponds approximately to the representation shown in
Figure 4. However, the rollers 4 are held on an endless
chain 16 revolving in the manner of a crawler tractor. In
this case, starting from an initial position A, the
rollers 4 are guided relative to the transport chain 2
and are brought to bear on a bottle 3. From this position
B, the roller 4 is guided parallel to the tranæport chain
2, with the roller 4 and bottle 3 rotating in opposition,
as far as a point C. There, the roller 4 is lifted off
from the bottle 3 and guided to the point D. There, the
coating material is applied to the roller 4 by means of
the sprinkler head 6.
In this case, the lifting carriage 5 possesses
four sprinkler head~ 6 and can be moved to and fro
according to the upper arrow x.
In this embodiment too, the sprinkler heads 6,
together with the associated carriage, are moved to and
fro horizontally. In this case, however, there is no need
for raising and lowering again.
The embodiment shown in Figure 7 corresponds
approximately to the embodiment shown in Figure 6. The
difference is that the carriage 5 possesses only two
sprinkler heads which are moved to and fro according to
the arrow x.
Moreover, in all the embodiments, the rotational
speed of the bottle and roller can be especially 1
revolution per minute to 300 revolutions per minute. This
rotational speed is expediently adjustable.
Figure 8 shows a typical sprinkler head 6 with a
casting strip 18. From this casting strip 18, the necess-
ary coating material is transferred in metered quantity
onto the roller 4. The design of the sprinkler head is,
in this case, of a conventional kind.
The roller 4 possesses the core 13 already
described above, with the elastic transfer material 12
and with a central continuous bore 17 concentric to the
axis of rotation. This roller 4 is pressed against the
2 1 8~q62
- 14 -
bottle 3 and at the same time transfers the coating
material onto the bottle 3 and distributes it over the
outer surface of the latter.
Due to the fact that each bottle to be coated or
each moulding to be coated is asæigned its "own" roller,
it is also possible to allow for the frequently occurring
fact that a location for a moulding 3 in the transport
device 2 is often not occupied by the moulding 3 to be
coated.
The apparatus according to the invention can
therefore be equipped with a detecting device (not shown)
which ascertains whether, at a location for a moulding in
the transport de~ice 2, a moulding of this type is
actually present or not. If no moulding to be coated i8
present, then this information is c~mmnn;cated to a
control and regulating device for metering the quantity
of coating material. This control device then ensures
that no coating material is transferred onto the roller
4 if the moulding to be coated or the bottle 3 to be
coated is not present in the transport device 2. This
ensures that, for each bottle, the intended quantity of
coating material is applied to the respective roller and
is then transferred from this onto the bottle 3 to be
coated. In other words, there is no possibility that the
coating material applied to the respective roller in one
work cycle will not be transferred onto the bottle 3, but
remains on the roller 4, onto which the same coating
quantity is then applied once again in the next work
cycle, 80 that double the coating quantity is
subsequently transferred onto the next bottle to be
coated. A reproducible and uniform coating meeting the
requirements is thereby achieved.
