Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a method for the
production of a cardboard presentation box of high
mechanical strength for the packaging of eomparatively
heavy objeets such as glass bottles filled with a liquid.
For the production of cardboard boxes of high mecha-
nical strength which offer a substantial degree of rigidity
after being shaped cardboard grades of considerable
thickness and substantial density are utilized. However,
the printing and grooving or scoring techniques utilized
impose limitations in practice. As a matter of fact, for
a cardboard grade of greater weight than 500 g. it is no
longer possible to utilize ofset printing ana, similarly,
for cardboard grades of greater weight than 600 g. it is
no longer possible to make use of the conventional mechan-
ical or HF grooving or scoring methods. For cardboard
grades of weight up to 700 g. the grooving or scoring
operation may be replaced by an embossing or corrugating
method, but this technique is costly and the embossing or
corrugating operation may be performed only at a low speed.
In order to eliminate this disadvantage, micro-
corrugated cardboard grades have been developed which, for
a small thickness, have a higher mechanical strength than
an ordinary eardboard of the same thickness. These card-
boards may be subjected to offset printing and grooved or
scored by conventional techniques. However, they frequen-
tly suffer from surface deformations which are unacceptable
if a high-quality appearance oE the box is sought.
The present invention has as its object to provide
a method for the production of a presentation box having
a very high mechanical strength and a substantial degree
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of rigidity, from cardboard grades of small thickness which
are able to accept offset printing and to be grooved or
scored in accordance with conventional mechanical or HF
methods permitting operation at high speeds.
S More specifically, there is provided, in
accordance with the present invention,a method for the
production of a presentation box of high mechanical strength
and of substantial rigidity from a pregrooved or prescored
blank of cardboard of small thickness able to accept
offset printing and to be grooved or scored in accordance
with conventional mechanical or high frequency grooving or
scoring methods, characterized in tha-t it comprises selec-
tive reinforcement of parts of the blank not traversed by
grooves or score lines so as to produce on each side oE
the different grooves or score lines parts which are not
reinEorced to allow subsequent folding of the blank to form
the box, said selective reinforcement step comprising impre-
gnation of at least said parts to be reinforced with a har-
denable, polymerizable resin and exposure of the par-ts to
be reinforced to a high frequency field, in order to produce a poly-
marizatlon and hardening of the resin only over said parts to be reinforced.
The use of a cardboard blank of small thickness
convenient to undergo offset printing enables scoring or
~grooving of the blank according to a conventional method
and at high speed prior to reinforcing the blank by the
method according to the invention. Given that this reinfor-
cement does not affect -the folds, the reinforced blank may
be formed to shape easily by conventional mechanical means.
In accordance with preferred embodiments of the
invention, (a) only the parts to be reinforced an impregnated
with resin, or (b) all the surface of the cardboard blank
is impregnated with resin but only the parts to be reinforced
are exposed to the high frequency field.
The resin preferably consists of a thermosetting
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resin, such as an acrylic resin, an urea formol resin, a
melamine formol resin, a phenolic resin or else combinations
of resins of this kind.
The impregnation of the carclboard blank may be
made either by immersion of the cardboard blank in a bath
of resin, or by projecting the resin onto at least one sur-
face of the blank.
Possibly, a further reinForcement may be effec-
; ted by applying an auxiliary material combined with the said
imprenation. In this case, the bonding of the auxiliary
material and the polymerization of the impregnating resin
are preferably performed by means of a single HF treatment.
~ The auxiliary material may consist of a pliable
- ~ or semi-rigid material such as a fabric, leather, or a sheetof a plastics material or else a rigid material such as wood,
cardboard, a metal sheet or a sheet of a rigid plastics
material.
The invention will now be further described,
by way of example, with reference to the accompanying dra-
wings, in which:-
Figure 1 is a plan view of a prescored card-
board blank processed in accordance with the method of the
invention,
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Figure 2 is a diagrammatic perspective view of
an HF treatment tool for carrying out a preferred
embodiment of the method in accordance with the invention,
and
S Figure 3 is a diagrammatic perspective view of
an HF tool for the hardening of an impregnating resin
utilized according to another embodiment of the method
in accordance with the invention.
Figure 1 shows a cardboard blank 1 for a cardboard
box which has been cut out and prescored in a conventional
manner in order to form a parallelepipedic presentation
box. This blank 1 has panels 2 to 5 intended to form
the side, rear and front walls of the box. The panels
are separated by scored lines 6 to 8. Furthermore,
at their upper and lower extremities, these panels carry
flaps 9 to 15 intended to form the base and lid of the
box. These flaps are separated from the said panels
2 to 5 by scored lines 16 to 22. The flap 10 and the
panel 5 moreover comprise a sealing tab 23 and 24,
respectively.
The blank 1 is produced from a cardboard of smaller
weight than 500 g. in order to allow conventional cutting
out and scoring by means of mechanical devices operating
at a high speed. Furthermore, the cardboard may then
be printed by a rapid and economical offset method.
In order that a box of very high mechanical strength
may be produced from this blank 1, the parts which are
not traversed by the scored lines 6 to 8 and 16 to 22
of the panels 2 to 8 and of the flaps 9 to 15 are the
parts which are selectively reinforced by the method
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according to the invention. In the embodiment illustrated
in Figure 1, only the panels 2 to 5 and the flap 10
are reinforced as illustrated diagrammatically at 25
to 29. Practice has shown that a reinforcement of this
kind is sufficient to increase the m~chanical strength
of the box obtained, to a considerable degree. It is
however evident that it is also possible to reinforce
the whole of the panels and flaps of the cardboard blank
1.
Accordinq to a first embodiment of the method in
accordance with the invention, this reinforcement of
~ the~parts 25 to 29 is performed by positioning separate
`~ cutouts of an auxiliary material and bonding these
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cutouts on the cardboard blank 1 by means of an HF bonding
method. Operations of this kind are rapid and economical
and may easily be performed on a machine such as that
described in the Applicants French patent application
published under number 2,523,509 on September 23, 1983.
According to the invention, materials which are
~; 20 pliable, semi-rigid or rigid and which are able to be
bonded on the cardboard blank 1 by an HF bonding method,
may be utilized as the auxiliary materials. Advantag-
eously pliable materials such as fabrics and leather,
or semi-rigid or rigid materials such as cardboard and
sheets of plastics materials or sheet metal may be
utilized.
In the case of the utilization of auxiliary materials
which are comparatively expensive and which equally
serve the purpose of improving the aesthetic appearance
of the box obtained, the method according to the
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invention and the embodiment illustrated in Figure 1
in particular, make it possible to accomplish considerable
savings on material which may amount to 40~ as compared
to the consumption of material in accordance with th~
known methods in which the whole surface of the card-
board blank 1 is covered. For example, in the case
of utilization of leather, this represents a considerable
advantage.
Figure 2 diagrammatically shows an llF bonding tool
for bonding cutouts of auxiliary material on the parts
which are to be reinforced, 25 to 29 of the cardboard
blank 1 illustrated in Figure 1. The top plate 30 of
a conventional HF press is shown in this figure. This
plate 30 carries on its lower face a separate bonding
tool 31 to 35 formed by a rectangular frame of a brass
section for each cutout of auxiliary material which
is to be bonded. A peripheral bond of this kind of
the cutouts of auxiliary material has proved to be
sufficient to enhance the mechanical strèngth of the
box obtained.
According to another embodiment~ of the method in
accordance with the invention, the parts 25 to 29 of
the cardboard blank 1 are~reinforced by impregnating
them~with a thermosetting polymerizable resin. These
parts 25 to 29 are then exposed to an HF treatment
producing a localised polymerization and hardening of
the resin in the parts which are to be reinforced.
-To this end, use is made of resins able to harden under
the action of an HF treatment.
According to another embodiment of the method in
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accordance with the invention, the whole of the surface
of the cardboard blank is impregnated with a thermosetting
resin. Only the parts which are to be reinforced are
thereafter exposed to the HF treatment,thus producing
S a localised polymerization and hardening of the resin,
whereas the fold lines or projections of the cutout
are unaffected by this treatment and thus permit forming
the box to shape by mechanical means.
Thermosetting resins are preferably utilized for
this impregnation, such as acrylic resins, urea formol
resins, melamine formol resins, a phenolic resin or
else combinations of such resins. The catalysts utilised
with these resins determine the final rigidity of the
treated parts of the cardboard blank.
An HF tool such as that illustrated in Figure 3
is utilised for the HF treatment in these last two
embodiments. The top plate 36 of a conventional HF
press, which is not illustrated in detail, is apparent
from this figure. The plate 36 comprises on its lower
20 ~ace, for each part 25 to 29 of Figure 1 which is to
be reinforced, a separate HF tool 37 to 40 formed by
a sectional rectangular frame. Each frame comprises
a series of longitudinal and transverse webs 42 and
43 respectively. Practice has shown that a tool of
this kind enables the carrying out of a polymerization
and hardening of the impregnating resin in the parts
25 to 29 which are to be reinforced, in a manner adequate
to effect a considerable improvement of the rigidity
of the cardboard blank 1.
According to a preferred embodiment of the method
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in accordance with the invention, the selective reinfor-
cement by the application of cutouts of auxiliary
material is combined with the reinforcement by means
of localized impregnation and hardening. In this case,
the cardboard blank 1 is first impregnated with an
` appropriate resin. The auxiliary material cutouts are
then placed in position and, during another stage, an
HF treatment is applied to effect the bonding of the
- cutouts and the localized hardening of the resin. If
appropriate, this operation may be performed in a single
stage and with a single appropriate HF tool.
This tool may be of the kind illustrated in Figure
3. With an appropriate setting of the HF press, it
then simultaneously assures the bonding of the auxiliaxy
material cutouts and the polymerization as well as the
hardening of the impregnating resin in the parts 25
to 29 which are to be reinforced. The bonding of the
auxiliary material cutouts and the polymerization of
the impxegnating resin may also be performed i~ two
successive stages and with two different tools such
~; as those illustrated in Figures 2 and 3, respectively.
The invention is clearly not limited to the
embodiments described and illustrated herein, and numerous
modifications may be made without departing from the
scope of the lDvention.
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