Note: Descriptions are shown in the official language in which they were submitted.
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This invention rela-tes -to a paper can barrel and,
more particularly, to a paper can barrel in which the ver-
tical joint portion is coated with a synthe-tic resin.
In a conventional paper can barrel, the ver-tical
joint is formed by superposing both marginal ends of a sheet
oE paper to each o-ther and adhering them to each o-ther by
means of an adhesive or, al-ternatively, by lapping and
jointing these marginal edges Wit}l the inner end being folded
or bent. In the first-mentioned jointing struc-ture, however,
the liquid contained by the can inconveniently permeates
into the cut end surface of the paper sheet which is exposed
to the inside of the can, so tha-t it is necessary suitably
to treat the end surface to prevent the permeating of the
liquid. In the join-ting structure of the second-mentioned
type, the thickness of the jointing portion is increased
undesirably to make it difficult to fix a can end plate to the
paper can barrel. In addition, the non-adhered lapping
portion in -the vertical join-t -tends to be deformed undesir-
ably by application of externa] force.
Accordingly, the presen-t invention provides an
improved paper can barrel having an improved join-t structure,
-thereby to overcome -the above-described problems of the
prior art.
To -this end, according to the invention,-there is provided
a me-thod of making a paper can barrel which comprises apply-
ing -to each surface of a sheet of paper a lining layer of
a heat-fusible weldable synthetic resin; coating one marginal
end inner surface of said sheet of paper and also -the other
marginal end outer surface of the said shee-t of paper with a
heat-fusible and weldable synthetic resin layer having a
serrated profile; forming a jointing step on one of these
two marginal ends; superimposing the other marginal end on
the jointing step; and pressing and heating -the superimposed
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portion so that -the lining layers of resin in contact become
fused together, and the serrated profile resin layers are
caused to flow and spread over the -two marginal ends.
In particular it has been found that coating the
marginal surfaces of the shee-t of paper with a heat-fusible
and weldable syn-thetic resin layer wi-th a serrated profile
renders the layer more readily fusible than in a non-serra-ted
profile thus reducing the-time for the pressing and heating
of -the sheet of paper and -thus the risk of damaging the
sheet of paper such as by scorching.
A preferred paper can barrel made in accordance
with the invention is hereinafterOdescribed by reference to
the accomapnying drawings, in which:-
Fig. 1 is a schematic perspective view of -the
paper can barrel;
Fig. 2 is a front elevational view of a paper
sheet used as a blank for the paper can barrel shown in Fig.
1 ;
Fig. 3 is a plan view of the paper sheet shown in
Fig. 2;
Fig. ~ is a schematic end view of the paper sheet
in a rounded state;
Fig. S is an enlarged sec-tional view of a part of
-the paper sheet as shown in Fig. ~; and
Fig. 6 is an enlarged sectional view of the ver-
tical joint portion of the paper can barrel.
The paper can barrel 6 as shown in Fig. 1, is
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constituted by a paper cylindrical body formed by join-ting
both marginal ends of a shee-t 1 ofpaper shown in Fig.s 1
-to 4. The paper sheet 1 is prepared by lining the outer
surface of a core paper sheet 7 (see Fig. 5) with a layer 4
of a heat-fusible and weldable synthetic
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resin such as polye-thylene, applying an alumin~n foil
o to the inner surface of the core paper sheet 7, and
lining the ou-ter surface of the aluminum foil 8 with a
heat-fusible and weldable synthetic resin such as polye-
-thylene.
The surface of the marginal end 2 of the paper
sheet 1, which is to constitute the inner surface of the
vertical joint portion of the paper can barrel, is coated
with a layer 5 of polyethylene of serrated profile.
Also, the.su~face of ~he marginal end 2a oF the
paper shee-t 1, which is to constitute the outer surface
of the ver-tical joint portion of the paper can barrel, is
coa-ted with a layer 5a also of serrated proFile, as shown
in Figs. 3 to 5.
The marginal end 2 of the paper sheet 1 is pressed
over a predetermined width of, for example, about 8 mm -to
form a join-ting step 3 which projects inwardly of the
paper can barrel to be formed.
The paper sheet 1 thus formed is then rounded and
i-ts marginal ends 2, 2a are lapped so that the marginal .
end 2a fits o~er the jointing step 3. The overlapping
portion is then clamped and pressurized by a clamping
tool while being subjected to heat, so that the polyethy-
lene layers are fused and united to each other thereby to
form a paper can barrel 6 having a vertical joint portion
10. Then the layers L~, L~a of the synthetic resin on the
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4.
inner and outer surfaces of the paper shee-t 1 are fused
and softened so as to be integrated with each o-ther with
the imler surface of the marginal end 2a firrnly adhered
-to the outer surface of the jointing step 3.
Meanwhile, the layer 5 of the synthetic resin applied
to the im~er end of the marginal end 2a, i.e. the jointing
step 3, is fused to flow and spread toward the end surface
9 of the paper sheet 1 as sho~n in Fig. 6, so as to coat
the inner end of the jointing step 3, end surface 9 and
the inner portion of the marginal end 2a of the vertical
joint portion. On the other hand, the layer 5a of the
-synthetic resin applied to the outer end of the marginal
end 2a of the paper sheet 1 is also fused to flow and
spread toward the end surface 9a of the paper sheet 1 to
coat the outer surface of the jointing step 3, end surface
9a and the outer side of the jointing marginal end 2a.
Since the marginal edge of the paper sheet 1 constit-
uting the vartical joint portion 10 of the paper can barrel
6 is completely covered by the synthetic resin, it is
possible -to avoid the undesirable permeation of the li4uid
content of the paper can into the end surface of the paper
shee-t now formed into the paper can barrel. Thanks to the
provision of the jointing step 3, it is possible to obtain
a smooth and continuous outer surface for the paper can
barrel at the vertical joint portion 10.
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Instead of projecting the jointing step 3 inwardly
of tlle paper can barrel, it is possible -to project the
s~ne outwardly of the paper can barrel.
It has been confirmed through an experiment conduc-
ted by the presen-t inventors that the layers 5, 5a of the
synthetic resin of serrated form flow and spread in a
satisfactory manner.
In the paper can barrel of the present invention
having the described construction, -the syn-the-tic resin
applied to the jointing portion effec-tively stiffens the
joint portion and comple-tely eliminates any permeation
of the liquid content of the can into the cut end surface
of the paper sheet constituting the paper can barrel.
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