Note: Descriptions are shown in the official language in which they were submitted.
BA~KGROUND OF THE INVENTION
The present invention concerns an apparatus ~or seaming the end
of a tube made of plastic or a laminated material consisting
of plastic and aluminium foil layers, said tube being used
as a container for the storage and application of e.g.
toothpaste or cosmetic substances.
At present, there are three known main types of tube used
for the storage and application of toothpaste or cosmetic
substances and the like. Formerly, a commonly used type of
tube was made of light metal, notably aluminium. The end of
the tube was usually seamed by making several folds at the
tube end. However, a seam like this is no-t reliable enough,
because the end seam of aluminium tubes is often liable to
be damaged in use.
A widely used type of tube is the plastic tube, in which the
envelope is made of an elastic plastic ma-terial. Such a tube
has the advantage that its form remains unchanged in use.
Because of its unchanged'esthetic appearance, this type of
tube is especially suitable for use as a container of
women's cosmetics.
Another common type of tube currently used is the laminated
tube, in which the envelope is made of a laminated rrlaterial
consisting of alterna-te plastic and aluminium foil layers.
~nlike the all-plastic tube, due to the aluminium layers,
the laminated tube is deformed in use. The plastic materials
generally used in such tubes are polyolefines, such as high-
pressure or low-pressure polyethylene or polypropylene. The
end of a plastic or laminated tube is usually searned e.g. by
heating the open end of the tube, substantially circular or
elliptical in sectional form, until it becomes soft, and
then squeezing the tube sides together, so that a seam is
produced between them. The s-trength of a seam made in this
way is equal to the tearing resistance of` the plastic foil
seamed together on the inside of the tube. The strength of
the seam is therefore insufficient, considering that the
longitudinal seam of the tube envelope, if made by the
newest manufacturing methods, will withstand Up to twice as
rnuch pressure as the end seam can -tolera-te.
'~ith time, the end seam of the tube is weakened e.g. by
corrosion caused by factors like the aromatic substances
present in the product, such as toothpaste, contained in the
tube. Tests have proved -that the s-trength of the end seam is
reduced to half -the original within six months. Observations
like -this have naturally created a need to take a closer
look at the structure of the end seam. To make it easier to
understand the present invention and the advantages it
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offers, it is necessary to explain the reasons why the
seams currently used are inadequate in respect of dura-
bility.
The seam is normally about 5-10 mm long. The
seam is evenly Eormed and i-ts cross-section has the form
of a straight line. If a pressure is created in the tube,
the sides of the seam tend to be torn apart, because the
seam strength is insufficent to prevent -this. With time,
the above-mentioned aromatic substances corroding the
seam also contribute to the tearing apart of the seam
sides. The ren-t advances in an elliptical sectional form
until a hole appears in the end seam of the tube.
OBJECrr OF THE INVENTION
The object of the present invention is to create
a method for seaming the end of a plastic or laminated
tube so that the seam will have a greater resistance to
s-train. Another object of the inven-tion is to create
an apparatus for applying the said me-thod.
According to -the present inven-tion, there is
provided an apparatus for seaming open ends of filled
tubes closed at their other end and made of plastic or
of a laminated material made of alternate aluminum foil
and plastic layers, said appara-tus comprising conveying
means for moving the tubes continuously in a generally
straight line direction and carrying -the tubes with the
open ends upwards, a folding device and a seaming device,
wherein said conveying means comprises means for positive
guidance of the tubes between the conveying means and
the folding device as well as between the folding device
and the seaming device, and said conveying means, the
folding device and the seaming device as well as the said
means for positive guidance are arranged to convey the
:~o ~
tubes through the whole apparatus at a substantially con-
stant speed.
A preferable embodiment of the method of the
invention is characterized in that the tube end is heated
from both sides during seaming.
A preferable embodiment of the invention is
characterized in that the open end of the tube is first
cut so as to give it an oblique form, in such manner that
the side of the envelope towards which the end is to be
folded is shorter than the other side, thus producing
the effect that after the end has been folded, the fold
will have an even end.
Another preferable embodiment of the invention
is characterized in that, before folding, the open end
of the tube is cut so as to give it an oblique form, in
such manner that the side of the envelope towards which
the end is to be folded is considerably shorter than the
other side, producing the effec-t that, after the end has
been folded and seamed, the outer surface of the fold
will be joined to tha-t surface of the tube envelope which
faces towards the fold.
A preferable embodiment of the apparatus of
the inven-
5 ~ 3
tion is characterized in that it comprises cooling and
starnping devices arranged after the seaming device
Another prel'erable embodiment of the apparatus of the
invention is charac-terized in that the conveyor consists of
a foam rubber belt and a conveyor belt.
A further preferable embodiment of the apparatus of the
invention is characterized in that the folding device con-
sists of two successive bending discs.
Thus, a seam produced according to the invention has the advantage
that the cross-section of the tube end will always retain
its straight line-like form and no tearing can take place,
since the opposite sides of the tube envelope can not move
apart. This is due to the fact that another seam will be
formed outside the tube, between the fold and the tube sur-
face. Therefore, the aromatics of the substance contained in t
the tube can not get into the seam. A seam made acco.rding to
the invention has a considerably be-tter resistance to strain
than the known types of seam have, because its strength is
equal to the tensile strength of -the laminated material it-
self.
Another important advantage with the apparatus of the invention
is that the whole seaming operation is accomplished while
the tubes are moving along a continuous path in the same
direction, involving no back-and-forth jerking movements.
3~
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention is described in detail b~
the aid of examples of advantageous embodiment, reference
being made to the drawings attached, wherein:
Fig. 1 presents a top view of the apparatus applying the
method of the invention, partly sectioned.
Fig. 2 presents a section along the line II-II in fig. 1.
Fig. 3 presents a section along the line III-III in fig. 1.
Fig. 4 presents a section along -the line IV-IV in fig. 1.
Fig. 5 presents a section along the line V-V in fig. 1.
Fig. 6 presents a section along the line VI-VI in fig. 1.
Fig. 7 presents a section along the line VII-VII in fig. 1.
Fig. 8 presents a section along the line VIII-VIII in fig.
1.
Fig. 9 presents a section along the line IX-IX in fig. 1.
Fig. 10 present a sectional view of a known tube end seam.
7 ~ 3~3
Fig. 11 presents a sectional view of a tube end seam produ-
ced by the method of the invention, using the appa-
ratus applying this method.
Fig. 12 presents an advantageous embodiment of the inven-
tion.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIME~ITS
_,
In figure 1, the apparatus applying the method of the inven-
tion is shown in top view, partly sectioned. The apparatus
incorporates foam rubber belts 1, with which -the tubes 2 are
transpor-ted in an upright position with the open ends up-
wards. At this stage, the tubes have already been filled
with -the desired substances, such as -toothpaste or the like.
As the tubes get into the narrow space between the two oppo-
sitely placed conveyor belts 3, the upper end of each tube
is squeezed together, whereupon the tubes 2 are moved
further by the conveyor belts 3 into a folding device con-
sisting of two successive bending discs 4, 5. The first
bending disc 4 bends the tube end to an angle of 90 rela-
tive to the vertical plane, and the second bending disc 5
finishes the folding in the way shown in figure 6. On leav-
ing the folding device, the tube 2 has an end bent double.
The tube is transported from the first bending disc to the
second under positive guidance with the tube end in the
9 r-~
8 ~^~ ~ ~ ~
position shown in fig. 5. This prevents the oent end from
beind straightened out. In a similar way, under positive
guidance, the tube advances from the second bending disc ~
to a seamer consisting of two oppositely placed movable
seaming belts 7 arranged so that they slide over the heaters
8 and squeeze the tube ends. To keep the seaming belts 7
steadily in place in the vertical direction, the seamer is
provided with wires 9 embedde~ in the heaters 8 and attached
to the seaming belts 7 e.g. by vulcanizing. The heaters 8
are provided with heating cartridges lO, from which the heat
is conducted via the heaters and the belts to the folded
tube end to be seamed. While the -tube end is heated, it is
also tightly squeezed together by means of the seaming belts
7. The structure of the seams thus produced is explained in
detail in connection with figures 11 and 12. According to
the invention it is also possible to use the seamer with
only one heater 8, in which case lt is best placed on that
side to which the tube end is bent.
In addition, the apparatus may be provided with cooling and
stamping discs ll, placed after the seamer. By means of the
stamping disc, e.g. the manufacturing number may be printed
on the seam.
Figure 10 shows a tube end with a seam produced by the met-
hod most commonly used at present. In that method, the seam
12 is formed between the envelope sides 13 and 14. The seam
is made by heating the tube end and squeezing the tube sides
tightly together between cold squeezing jaws
Figure 11 shows a -tube end seam produced by the method OI
the invention Before the seaming, the envelope 13~ 14 is a
tube with a substantially round sectional form. According to
the invention, the envelope is either all plastic or lamina-
ted from alternate plastic and aluminium foils pla-ed one
upon the other. The most advantageous plastic materials for
the purpose are polyolefines, such as low-pressure and high-
-pressure polyethylene or polypropylene. In the tube shown
in figures 11 and 12, the envelope is made of a laminated
material having two aluminium foil layers 15. The number of
aluminium foil layers used is arbitrary and in no way re-
stricts the invention. An advan-tage is gained by cutting the
end of the envelope into a slightly oblique form in such a
way as to make the envelope shorter on the side to which the
end is to be bent. This makes it possible to produce a seam
with the ends of the envelope halves 13 and 14 flush. The
seam 16 is created between the outer surface of the envelope
half 13 and the inner surface of the fold. The seam 17 is
created within the fold between the two envelope halves 13
and 14. If necessary, the tube end may also be heated from
the other side to produce a seam between the envelope
halves 13 and 14 before the fold. This is the case in the
examples of embodiments presented in the figures. However,
as fas as durability of the end seam is concerned, this is
not necessary.
23~
In figures 10-12, for technical reasons and to irnprove the
readability of the figures, the si~e of the seam has been
greatly exaggerated. For instance, in figure 11 the dimen-
sion L is about 4-5 mm and the dimension S about 1 mm. In
the real proportions, the lower edge of the bend is not as
round as implied by figures 11 and 12, but sharp.
Figure 12 shows an advantageous embodiment of the invention
in which, prior to folding, the end of the envelope 13, 14
has been cut into an oblique form in such manner that, after
folding and seaming, the ou-ter edge l9 of the envelope half
14 is joined to the outer surface of the envelope half 13.
This improves the appearance and further increases the dura-
bility of the seamed end. Otherwise the structure of the
tube end is the same as in the embodiment shown in figure
11, i.e. when hea-ted from both sides, the seams 16, 17, 18
are produced.
It is obvious to a person skilled in the art that the inven-
tion is not restricted to the examples of its embodiments
presented above, but that it can be varied within the scope
of -the following claims.
