Note: Descriptions are shown in the official language in which they were submitted.
~1259292
Folding box
The invention is directed to a folding box, consisting
of a first cut-to-size blank from non-transparent material,
particularly cardboard, and a second cut-to-size blank
from transparent stiff plastic foil, which extends over at
least one box edge which, in one portion, is constituted
by a bending line provided in the plastic foil, and which
is glued with the first cut-to-size blank overlapping on
its inside; an overlap between the first and second cut-
to-siæe blank exists also at at least one end of the
bending line and the bending line is continued in the
first cut-to-size part by a corresponding groove line,
at which the box edge to the other part is formed.
Such folding boxes consisting of differing materials
are known in different embodiments. In a known window
folding box, the cardboard cut-to-size part has an aperture
constituting a viewing window, which is sealed by a leaf
of stiff plastic (DE~OS 31 48 443). In another known
folding packing (DE 31 53 240 of the Internatonal
Application WO 82/00449), not only is a viewing window
in the cardboard blank provided, but a plurality of walls
or wall portions connected with each other by box edges
possibly including ad~acent sealing flaps and dust strips
are fabricated completely from a plastic part.
In the two box types described above, overlaps between
the two blanks consisting of differing materials exist at
the end of bending lines formed in the plastic blank, or
can exist in the previously described folding packing.
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These points of overlap cause difficulties during
folding, since, because of the double material thickness
at the points of overlap, material displacement and
material stretching can occur. Since the plastic blank
rests on the inside of the cardboard blank, the plastics
foil is crushed during folding in the area of the groove
line of the cardboard blank, while the cardboard is simul-
taneously stretched in such a way that its outer layer or
lining can tear along the groove line. The folding at
such overlap points can be performed mechanically only in
an unsatisfactory manner.
It is provided for avoidance of the previously
described difficulties in an additional known folding
container with window (DE-OS 14 36 993), that recesses are
provided in the window foil edge in the area of the bending
line, while tangs or fingers are provided at the cardboard
blank which overlap these recesses. Since the overlapping
surfaces at the fingers and the window foil are free of
glue in this area, a displacement between these surfaces
during folding is possible without the occurrence of
stresses. At the same time, the folding container does
not become leaky at the recesses, since the tangs cause a
covering in the area of the container edges. The tangs or
fingers existing in this known folding container, however,
not only considerably limit the shaping possibilities of
the container, but also render the mechanical folding more
difficult, because they bend outwards during the folding
.~- -2-
2~i~2~
process and thus forrn undesirable protrusions.
rn the pceviously mentioned known window folding box
(~E-OS 31 4~ 4~3), it is provided that the above-mentioned
cecesses or notches extend at least up to the edge of the
window opening~ Because of the more or less large aper-
tures thus formed between the cardboard blank and the
plastics leaf in the area of each overlap spot at the oox
edges, material displacement in these difficult areas should
not occur during the folding process. The existence of
apertures at folding box edges is, however, not acceptable
for all applications of packagings of this type.
The present invention provides a folding box of the
previously discussed species, in which neither outwardly
projecting tangs nor apertures exist at the overlap spots in
the area of the folding box edges and which, in spite o
that, can be mechanically folded without diffic~llty also at
these overlap spots. Thus, according to the invention there
is provided a folding box consisting of a first cut-to-size
blank from non-transparent material and a second cut-to-
size blank from transparent stiff plastic foil, whichextends over at least one box edge, a bending line
provided in the plastic ~oil, second blank overlapping and
being glued to the first cut-to-size blank on an inside
surface of said first blank, wherein the overlap between
the Eirst and the second cut-to-size blanks exists also at
- at least one end of the bending line, and the bending line
`~
~2~3Z~2
is continu~d in the ~irst cut-to-size blank by a
cocresponding groove line, th~ bending line and groove
line being approximately the same width and wherein a box
edge of two box walls is ~ormed by said bending line and
said groove line, characterized in that the second blank
is thinned-down to a fraction of the thickness of
remaining portions of the second blank in an area along
the bending line and directly adjacent to .he bending line
at the overlap between the first and the second blanks,
the thinned-down area of the second blank extending over
the entire width of the overlap.
These measures cesult in a complete stress equalization
at the explained difficult areas of the overlap spots located
at the box edges, because the thinned-down areas are easy
to deform under the action of the upsetting forces generated
during folding. These deformations, which essentially occur
as small creases exclusively in the area of the thinned-down
areas, are located on the inside of the groove lines of
the cardboard blank and therefore are not observable in an
undesirable fashion from the outside. If the thinned-down
areas are dimensioned in such a manner that they extend only
over the overlap length or possibly are slightly larger,
meaning that they do not protrude at all, or only slightly,
beyond the cardboard edge, a smooth and continuous edge
without interruptions is obtained when folding the box edge
involved, which c~ntains neither holes nor steps a~ those
~ 4 -
3~ '
12~9~92
points where the two different materials abut which would be
visible Erom the outside.
The thinned-down areas appropriately exhibit an essen-
tially constant cross-section across their length. Thus a
uniform stress equalization over their length is achieved in
the form of continuous small creases, if the folding box is
Eolded at the edges involved, that is, when it is erected
from its flat collapsed position.
- 4a -
125~29~
The thinned-down areas comprises,advantageously,a dimin-
ishing thickness starting from their side edges towards the
center, wherein the thickness is smallest in the area of the
groove lines in the first blank. The deformability of the
thinned-down areas along the groove lines of the first blank
is largest because of these measures, wherein the formation of
small creases equalizing the stress is favored.
The thinned-down areas,which naturally are produced in
the plastic foil blank prior to its being united with the
cardboard blank by gluing, can be produced by action on the
plastic foil from both sides~ Preferably,however,they are
produced by action only on one side of the plastic foil, while
the plastic foil part is resting on a flat surface.
Especially suitable thinned-down areas for the task
provided are achieved if these are produced together with the
fold lines by high frequency-/pressure action or by hot stamping.
Attention has to be paid when forming the thinned-down area, so
that no interfering migration beads,consisting of plastics
material,are generated at the side edges of the thinned-down
23 areas, so that a gluing with a cardboard blank is also possible
on that foil side at which such migration beads could be formed.
Pursuing the inventive thought the thinned-down areas
can be differently shaped while retaining the same,or nearly
the same,effectiveness. Preferably,the thinned-down areas
125~Z~
are bounded on one side in an arc-shaped manner viewed in cross-
section. They can, however, also be bounded on one side respect-
ively by at least two abutting inclined planes. Another
possibility consists in that the thinned-down areas are bounded
on one side,respectively)by two outer inclined planes and one
central flat plane. Finally, an embodiment is also possible in
which they are bounded on one side by flat faces arranged in a
step-shaped manner.
It is provided in a preferred embodiment o~ the
folding box that,respectively,three parallel grooves are molded
spaced equally within the thinned-down areas, the central groove
being arranged in direction of extension of the appropriate
bending line in the second blank. These fine grooves create
intended folding points, at which small uniform wrinkles are
generated when folding the folding box, which take care of the
required stress equalization and which extend parallel to the
neighboring groove lines in the first blank.
It is advantageous here if the central groove follows
directly upon the bend line, and the two side grooves extend,
respectively,kinked at their inner ends and unite with the central
groove at the junction point to form the bend line. Because of
this groove configuration, the stresses occurring during folding of
the box also at the transition between the bend line in the
plastic foil and the thinned-down area,are compensated by a
roof-li~e deformation of the small surface areas of the thinned-
~.......
;~' down area bounded by the three converging grooves.
125~292
Particularly good results are achieved in the formation
of small predetermined wrinkles in the overlapping edge area
if the central groove is pressed into the thinned-down foil up
to a smaller foil residual thickness than the two side grooves,
which are pressed in up to an equal foil residual thickness.
With a thickness of between 200 ~m and 400 ~m of the
plastic foil used for the second blank it,has been shown to be
adavantageous if the minimum thickness in the region of the
thinned-down areas amounts to about 100 ~m.
It is appropriate for achieving good folding at the
critical edge overlapping zones of the two differing materials,
if the foil residual thickness at the central groove amounts
to about one-third and the foil residual thickness of the two
side grooves to about two-thirds of the minimum thickness in
the region of the thinned-down areas.
It is advantageous for the desired formation of small
wrinkles from the thinned-down areas along the groove lines
in the cardboard blank, if the overlap gluing between the two
blanks ends approximately at the side edges of the thinned-down
areas. During the placement of the three parallel grooves
within the thinned-down areas for the formation of such pre-
determined wrinkles,one has to pay attention that the overlap
gluing between the two blanks ends at the side grooves.
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lZ5~9~
Good results are also achieved if the thinned-down
areas comprise,respectively,one central strip covering the
associated groove line of the first blankand followingupon the
associated bend line of the second blank; said central strip
has a constant foil residual thickness at all points and is
adjoined in a stepless fashion by transition planes which
are arched in concave manner on the sides and which reach
up to the side edges. If in this case the central strip has
a foil residual thickness of approximately 40 to 60 ~m with
a thic~ness of the plastics fsil used for the second blank of
approximately between 200 and 400 ~m, while its width amounts
to about 1/3 to 1/6 of the width of the thinned-down a~ea,
particularly good results are achieved.
A folding box designed according to the invention
can be folded without problems, during box erection, at
the overlapping places located at the box edges defined
by the groove lines in the first blank and the bend lines
in the second blank aligned with said groove lines; this
without the cardboard material of the first blank tearing
in the zone of the groove lines and also without inter-
fering deformation of the plastic foil constituting the
second blank appearing in an area open to view. Herein,
all stresses arising during the folding operation are
compensated by the thinned-down areas existing at the
overlapping places.
--8--
~25~292
Due to the manufacturing tolerances, above all during
gluing of the two blanks, displacements of the thinned-down
areas with respect to the first blank can occur under certain
circumstances, which at the boundary between the visible area
-5 and the overlapping places can lead to residual stresses not
completely compensated by the thinned-down areas, particularly
when thicker plastic foils of roughly 400 ~m thickness are
utilized. In order to be able to also remove residual stresses
of this kind, should this be required in order to eliminate
the stress effects on the cardboard material and the foil visible
zones adjacent to the overlapping places, it is proposed
according to a further refinement of the invention, that at
the junction place between the bend lines and the thinned~down
areas in the second blank,respectively,one interruption be
provided which is continuous throughout the material thickness,
and which, in essence, is not overlapped by the first blank.
It has been shown that all possible residual stresses at
the boundaries between the visible area and the cardboard ~one
can be absorbed by such breaks; this alleviates the possibility
of the cardboard tearing at the cardboard boundary as well as
warping of the adjacent foil regions. In its simplest form
sufficient for most applications, the break is made advantageously
to be a line-shaped incision extending transversely to the bending
line, which incision projects on both sides beyond the bend line,
has approximately the width of the thinned-down area, and
extends parallel to the closely adjacent edge of the
, ., , . _g_
:~2~
first blank. The incision can hardly be seen from the outside
and does not constitute a hole worth mentioning in the foil
material even in the erected state of the box.
In cases where it is relatively unimportant
whether an~ holes are formed at the box edge in the visible area,
an arrangement can be made,according to a further embodiment of
the invention,in such a way that the break is designed as a
hole cutout which projects,at both sides,beyond the bend line
with surface areas corresponding approximately to each other
and whose width corresponds to approximately the width of the
thinned-down area.
Particularly favorable stress equalization results are
achieved by this method if the hole cutout is designed to be
circularly-shaped in the flat resting second blank or if the
hole cutout in the flat resting second blank exhibits approx-
imately the shape of an ellipse, whose longer axis extends
parallel to the adjacent edge of the first blank.
The invention is described with particularity in the
following with the help of drawings illustrating the embodiment
examples, in part, schematically, wherein:
Fig. 1 is a perspective view of a window folding
box blank consisting of two parts glued to
each other,
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12$~2~Z
Fig. 2 is a plan view of a blank consisting also o
two parts glued to each other of another
folding box type;
Fig. 3 is a partial magnified plan view of an
overlapping place with a thinned-down area
arranged in the plastic material blank, in
a flat resting position;
Fig. 4 is a plan view similar to Fig. 3 with paral-
lel grooves formed in the thinned-down area;
Fig. 5 is a cross-sectional view of the plastic
material blank taken along the line V-V in
Fig. 3;
`~
Fig. 6 is a corresponding cross-sectional view of
the plastic material blank taken along the
line VI-VI in Fig. 4;
Fig. 7 are cross-sectional views similar to those
to 9 in Figs. 5 and 6 showing further embodiment
and 13 shapes of the thinned-down areas;
Fig. 10 is a perspective view of a window corner of
the glued, erected and closed window folding
box according to Fig. l;
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12~;9Z~2
Fig. 11 is a partial side view of the folding box
illustrated in Fig. 10;
Fig. 12 is à cross-sectional rnagnified view of the
folding box taken along the line XII-XII in
Fiq. 11;
Fig. 14 is a partial and rnagnified inside view of an
overlapping place of a folding box blank
composed of two blanks in a flat resting
position with a first embodiment of a break;
Fig. 15 is a partial side view of the folding box
erected from the folding box blank according
to Fig. 14;
Fig. 16 is an inside view of an overlapping place of
a folding box blank similar to Fig. 14, with
a second embodiment of the break,
Fig. 17 is a partial perspective view of the folding
box erected from the folding box blank
according to Fig. 16;
Fig. 18 is an inside view of an overlapping place of
~0 a folding box blank similar to the Figs. 14
and 16 with a third embodiment form of the
~;? break; and
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92
Fig. 19 is a partial perspective view of the folding
box erected from the folding box blank
according to Fig. 18.
In the magnified illustrations in the Figs. 5 to 9,
and 12 and 13, the thickness dimensions are shown consider-
ably more magnified than the width dimensions for reasons of
clarity.
Fig. 1 shows a typical blank of a window folding box,
which is composed of a first blank portion 1 of cardboard
defining the outer contour of the blank and a second blank
portion 3 from transparent stiff plastic foil covering a
window opening 2 in the cardboard blank portion in an over-
lapping manner. The blank results, after gluing, erection
and sealing on both sides, in a cube-shaped window folding
box, whose window opening 2 extends across its front wall 4
and across partial regions of the side walls 5 and 6 adjacent
thereto. The rear wall 7, adjacent to the side wall 6, is
part of the cardboard blank portion 1 as well as four dust
tabs 8 connected to the side walls 5 and 6l and the sealing
tabs 9 connected to the front wall 4. Insert tabs 10 are
connected to the sealing tabs 9. A gluing tab 11 is provided
at the rear wall 7 for gluing together of the blank into a
compact box jacket, the external face of gluing tab 11 being
glued to the inside face of the side wall 5. At the inter-
faces between previously mentioned portions of the cardboardblank portion 1, groove lines 12 are pressed into the card-
board, which in turn, form the box.
~^ -13-
12~Zg2
edges after gluing, erecting and closing of the folding box.
The foil blank 3 is glued to the inside surfaces of
the front wall 4 and the side walls 5 and 6 so as to overlap
the window opening 2 on all sides in a frame-like manner.
The frame-like overlapping surface is indicated in Fig. 1
with dots. The same applies to Figs. 2-4. Naturally, the
entire overlapping surface is not required for gluing the
two blank parts 1 and 3 together. The application of glue
can be limited to a relatively narrow strip, which, in Figs.
3 and 4, is indicated as being bounded by broken lines.
The foil blank 3 is divided by two fold lines 13 into
a front wall portion 14 and two side wall portions 15 and 16.
The fold lines 13 are continued by aligned groove lines 12,
which are located between the front wall 4 and the side walls
5 and 6 of the cardboard blank 1. Two box edges are formed
at these groove lines and the fold lines 13 which are exactly
aligned therewith when the folding box is erected.
,
Thinned-down areas 17 in the foil blank 3 are provided
respectively at four overlap points between the two blank
portions 1 and 3 in the area of the two previously mentioned
box edges; said thinned-down areas will be explained with
particularity hereinafter.
~2~329~
The invention is basically applicable to all types of
folding boxes and other foldable packaging units, as for
instance foldable slip-on covers; this to the extent that
overlap between cardboard and plastic foil occurs in the area
of box edges. In order to illustrate, to that extent, the
universal utilizability of the invention, a type of folding
box considerably deviating from the window folding box accord-
ing to Fig. 1 is shown as a blank in Fig. 2 with the help of
its blank. Here we are dealing with a folding box which has
the approximate shape of a cube after gluing, erecting and
closing on both sides. Here no window opening is provided in
the first blank 18 consisting of cardboard. Rather the second
blank 25, fabricated from transparent stiff plastic foil,
constitutes, with its external outline, a portion of the
overall blank, so that complete wall surfaces, or wall surfaces
continuous throughout one box edge length, consisting of
transparent plastic foil are formed in this folding box.
The first blank 18 comprises the rear wall 19, two half
side walls 20, 21, a smaller sealing flap 22, a larger sealing
flap 23 and four half dust tabs 24. The foldability between
these parts is again made possible by the groove lines 12
pressed into the cardboard.
The second blank 25, fabricated from transparent stiff
plastic foil, comprises the front wall 26, two side wall parts
27, 28, a larger sealing flap 29, a smaller sealing flap 30 and
four dust tab parts 31 connected to the side wall parts 27, 28.
,~
-15-
~25~Z9~
The foldability of the described foil parts is again
assured by the bend lines 13 located in the foil. Insert tabs
32 are located at the sealing flaps 29, 30, which engage slits
33 when the folding box is closed; said slits 33 are located
in the sealing flaps 22, 23 of the cardboard blank part 18.
As is evident, the sealing flaps 22 and 29, on the one hand,
and the sealing flaps 23 and 30, on the other hand, interact
when the folding box is closed. Since the smaller sealing
flap 22 of the cardboard blank part 18 is only half as large
as the sealing flap 23 constituting the box base, the upper
box closure also permits a view inside of the box because of
the transparent sealing flap 29.
As Fig. 2 furthermore shows, the two blank parts 18 and
25 are glued to each other so as to overlap, which is indicated
by the dotted surface area. Herein, the portions of the foil
blank 25 which are designed to be larger, as far as the area
is concerned, namely, the side wall portion 28 and the two
connected dust tab portions 31, overlap the corresponding
portions 20 and 24 of the cardboard blank part 18. The gluing
between the two blank portions occurs in the dotted surface
area on the insides of the parts 20, 24. Correspondingly, the
half side wall 21 and the half dust tabs 24 connected thereto
of the cardboard blank portion 18 are glued in an overlapping
fashion to the side wall part 27 and the dust tab parts 31
connected thereto of the foil blank portion 25. The overlap
limits are inclicated in Fig. 2 by means of two broken lines.
-16-
12~i~29~
Also in the case of this folding box, overlap points
in the area of the four box edges are located in the two
existing overlap areas of the two blank portions 18 and 25,
at which respectively, one bend line 13 is continued in a
precisely aligned manner by a groove line 12. At these
overlap points, four thinned-down areas 17 in the foil
material of the foil blank portion 25 are again provided in
accordance with the invention. The design and arrangement
of the thinned-down areas 17 is now explained with
particularity.
In this connection, reference is made, first of all,
to the Figs. 3 and 4, in which, respectively, one single
overlap point between the cardboard blank portion 1 or 18
and the foil blank portion 3 or 25 is shown. As can be
seen, the groove line 12 in the cardboard blank portion is
exactly aligned with the bend line 13 in the foil blank
portion, so that a folding edge of the box is formed during
the folding process which passes in a straight line through
both materials. In the region of this box edge, the foil
blank portion 3 (25) includes the thinned-down area 17,
which extends across the entire overlap length and slightly
beyond. The thinned-down area 17 comprises an approximately
rectangular outer periphery, the longer central axis of
which coincides with the groove line 12 and the bend line 13.
-17-
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As can be seen from the schematic sectional
illustrations of the Figs. 5 to 9, the foil blank portion 3
(25) is thinned-down to a fraction of its original thickness
in the region of the thinned-down area 17, wherein the
S thickness is smallest in the center of the thinned-down area
17, i.e. in the region of the groove line 12. The cross-
sectional formations of the thinned-down areas 17 illustrated
in Figs. 5 to 9 extend essential:Ly over the length of the
areas 17. Furthermore, it can be seen from the Figs. 5 to 9
that the thinned-down areas 17 diminish in thickness starting
from their side edges 34 towards the center thereof. The
reduction in thickness differs in the embodiments shown.
At the side edges 34 of the thinned-down areas 17
small beads are indicated in the Figs. 5 to 9 and 12, which
15- occur due to material migration from the thinned-down area
during the fabrication of the thinned-down areas. The
dimensions of these beads can be held within limits by means
of suitable measures, so that they do not interfere even if
the foil blank portion 3 (25) is glued together with the
cardboard blank portion 1 (18) on the side carrying the
beads. Tn the example according to Fig. 12, the surface of
the foil blank portion not comprising the beads is glued to
the cardboard blank portion.
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The thinned-down area 17, viewed in cross-section,
can be bounded on one side in an arch-shaped manner as is
illustrated in the Figs. 5 and 6. In the example according
to Fig. 7 the thinned-down area 17 is bounded on one side by
two inclined planes 35 meeting in the center. An embodiment
shape is illustrated in Fig. 8, in which the thinned-down
area 17 is bounded on the one side by two outer inclined
planes 36 and a central flat plane 37. Fig. 9 finally illus-
trates an embodiment of the thinned-down area 17 including
flat surfaces 38 to 40 arranged in a step-shaped manner on
one side of the foil. In each of the embodiments according
to the Figs. 5 to 9, the thickness of the thinned-down area
decreases from the side edges 34 towards the middle.
The border surface profilings of the thinned-down
areas described above are achieved by an appropriate design
of the tool provided for fabrication of the thinned-down
areas. The application of the thinned-down area 17 can
occur simultaneously with the placement of the bend lines 13
in one work process, and indeed with the help of processes
for the application of the bend lines. High frequency
heating with the simultaneous application of pressure is
principally used for this purpose, by means of which
particularly pliable soft bend edges are generated. Usable
results are, however, also achieved by simultaneous hot
stamping of the thinned-down areas 17 and the bend lines 13.
~, -19-
2~12
Herein, the fabrication of the thinned-down areas as well as
the bend lines 13 occurs appropriately by action on one side
of the plastic foil. The application of the bend lines 13 with
the high frequency process (DE-PS 25 41 324) as well as with the
hot stamping process are so well ~nown, that they do not require
any further explanation at this time.
If the folding of the overlap points for formation of
a box edge in an embodiment of the thinned-down area 17 occurs
according to one of the Figs. 5 and 7-9, then small wrinkles
occur essentially along the groove line 12 caused by the material
upsetting in the region of the thinned-down area 17 in direct
proximity of the groove lines 12 of the cardboard blank portion 1
(18); this completely compensates the upsetting stresses in the
foil in the overlap region of the box edge. The described process
for formation of the small wrinkles can be additionally con-
siderably promot~d, if three parallel grooves equally spacedfrom each other are molded within the thinned-down areas 17, as
.shown in the examples in Figs.-4 a-n~.6. The molding.of
these small grooves occurs simultaneously with the fabrication of
the thinned-down areas 17 and the bend lines 13. As can be
recognized in the example according to Fig. 4, the central groove
42 follows directly the bend line 13, while the two side grooves
41 and 43 are kinked at their inner ends and.unite with the
central groove 42 at the junction point with the bend line 13. If
the thus formed thinned-down area 17 is deformed during folding
of the folding box edge concerned, then intended folds defined
along the grooves 41 to 43 are formed, as is illustrated
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12~292
in Fig. 12 in a greatly magnified manner. Because of this
the overlap area eonsidered here is not only folded in a
'particularly easy manner,but adefined foil deformation in the
thinned-down area is generated during the stress compensation
S with the successful equal appearance of all overlap areas
in the box edge area after the erection of the folding box.
Fig. 12 illustrates the typical formation of a bead 44
lying inside in the region of the groove line 12 in the
cardboard blank section 1 '(18). As is evident, the surface
zones of the thinned-down areas located between the grooves
41 to 43 rise in a roof-shaped manner from the bead 44 when
the defined predetermined folds are formed; this happens if
parallel grooves 41 to 43 are placed'in accordance with Fig. 4
and 6. The extent of this roof-shaped predetermined folding
generated inwards however diminishes in the inner end zone
of the grooves 41 to 43, in which the grooves converge towards
the junction point at the bend line 13; this phenomenon causes
again an approach of the foil material towards the bead 44.
The predetermined fold formation therefore does not lead to
the formation of holes in the edge transition region between
the'folded bend lines 34 and the groove lines 12, as is illus-
trated in the Figs. 10 and 11.
~' .
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12~ 32
As can be seen in Figs. lO and ll, it is not necessary
that the inner end region of the thinned~down area 17 projects
essentially beyond thecardboard edge. Inspite of that all the
stressesarising during folding are compensated by the thinned-
down area 17 in such a way,that neither a perturbing deformationof the foil in the visible region nor a tearing of the cardboard
material in the zone of the groove line 12 occurs. Bend
line 13 and groove line 12,rather,constitute a smoothly
continuous box edge, which is also nearly free of steps at
the transition point between the carton and the foil in the
edge region. The folding box thus meets all requirements
including aesthetic ones.
The placement of parallel grooves 41 to 43 was
only described with reference to an arc-shaped delimitation
of the thinned-down area 17, however the thinned-down area 17
can also be provided with grooves 41 to 43 corresponding to
the embodiments illustrated in Figs. 7 to 9. A parti-
cularly favorable easy foldability in the region of the grooves
41 to 43 results if the foil residual thickness of the central
groove 42 is smaller than that of the two corresponding side
grooves 41 and 43.
If stiff plastic foils are used for the fabrication
of packagings, particularly folding boxes, foil thicknesses
are utilized which lie in the region between 200 and 400 ~m.
For this thickness range,it has been found to be advantageous
if the thinned-down areas 17 are rormed in such a way that the
minimum thickness of the central region of the thinned-down
-22-
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areas amounts to approximately 100 ~m. The placement of
grooves 41 to 43 reduces the minimum thickness at the grooves
considerably. One obtains good results if the central groove
42 results in a foil residual thickness of approximately 30
~m, while the foil residual thickness at the two side grooves
41 and 43 amounts to approximately 60 ~m.
In the embodiment illustrated in Fig. 13 depicting
the cross-sectional shape of the thinned-down area 17, we
are also dealing with a schematic sectional presentation.
Previous statements dealing with the embodiment examples in
Figs. 5 and 9 apply also to Fig. 13 to the extent that no
deviating statements are made in the following text. Thus,
the additional placement of parallel grooves 41 to 43
according to Fig. 4 is not provided for the embodiment in
Fig. 13. In addition, the above statements concerning the
minimum thickness in the central region of the thinned-down
areas do not apply.
As is recognizable, a flat central strip 45 is located
in the thinned-down area 17, the width of which is indicated
by the dimension lines given the reference number 47. This
central strip 45 extends across the entire length of the
thinned-down area 17 and covers the assigned groove line 12
in the cardboard blank portion when the foil blank portion
3 (25) is joined witn the cardboard blank portion 1 (13).
Since the central strip 45 extends across the entire length
of the thinned-down area, it is directly contiguous to the
associated bend line 13
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. . .
9~'
in the foil blank portion 3 (25). The central strip 45 has
a very small constant foil residual thickness of 40 to 60 ~m
throughout. Good folding results are achieved with a
residual thickness of 55 ~m. The small foil residual thickness
indicated applies to a thickness of plastic foil of between
200 and 400 ~m which is to be used for the foil blank portion 3
(25). The width 47 of the central strip 45 lies between
one-third to one-sixth of the width of the thinned-down area 17,
which can amount to approximately 8 mm. A corresponding width
of 8 mm for the thinned-down area 17 is also suf~icient for the
examples described previously. Good results were achieved with
a width of the central strip 45 of between 1.5 and 2 mm.
Transition surfaces 46 arched in a concave manner
adjoin the central strip 45 on both sides- in a stepless fashion;
said transitional surfac~ 46 ~erminate at the side edges 34
of the thinned-down area 17. When folding the glued-together
blanks,it has been shown that the desired small wrinkles occur
in the region of the central strip if the cross-sectional
shape is according to that shown in Fig. 13; this results
n an approximate configuration as shown in Fig. 12,
even if the glue between the two blanks is not interrupted
at the thinned-down areas17- In this case micro wrinkles form
which,in actual practice,rest tightly at the beacl 44.
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.
. .
9~
The overlap spots depicted in truncated ~orm in the
Figs. 14, 16 and 18 can basically be designed in all known
types of folding boxes as illustrated in said figures,
,provided the~ are composed out of a first blank portion 1,
which, for instance, is constituted by cardboard and a second
blank portion 3 from transparent thick plastic ~oil. Such
composites of foldin~ boxes can be designed resembling a
window folding box, as indicated by window openings 2 in
Figs. 15, 17 and 19 at a comparatively sMaller scale, or
they can comprise a larger plastic material part compared
to a window folding box, which extends across several wall
portions possibly including adjacent sealing flaps and dust
tabs. The folding boxes considered here have, in common,
the overlap between the cardboard blank part 1 and the foil
blank part 3, wherein both blank parts are glued together,
and indeed the cardboard blank part 1 on its inside and the
foil blank part 3 on its external side. The overlapping gluing
is indicated in a dotted manner in the Figs. 14, 16 and 18
and does not have to extend across the entire overlap area.
The gluing can also be executed in a strip-shaped manner, as
it is indicated in the above-named figures by the broken lines
extending parallel to the edges of both blank parts 1 and 3.
In case of the window folding box depicted in the
Figs. 15, 17 and l9,the foil blank part 3, and with it also
the window opening 2,extend across at least two abutting
wall surfaces of the folding box, namely,across the front
wall 4 and the side wall 6 in the illustrated embodiment.
.' ~, . .
-25-
: '
1259~
Accordingly,the foil blank part 3 comprises a front wall
portion 14 and a side wall portion 16, which abut at the
- bend line 13. The reference number 7 designates the rear
wall, and the reference number9,the lower sealing flap of
the folding box. The front wall 4 and the side wall ~ of
the cardboard blank part 1 are located on both sides of
the groove line 12 pressed into the cardboard. In the
drawings,only one groove line 12 of the folding box and
only one section of a bend line 13 is illustrated. It can,
however, be seen that the bend lines 13 and the g~oove line
12 are exactly aligned with each other if the folding box
blank (Figs. 14, 16 and 18) is in a flat resting ~osition;
after gluing, erecting and closing of the folding box,said
bend line 13 and groove line 12 form a continuous box edge
(Figs. lS, 17 and 19).
At all overlap spots existing at the box edges, of
which only one is depicted in the drawings, the plastic
foil material,consisting, for instance, of polyvinylchloride,
is thinned-down to a fraction of its original foil thicknessof
approximately 200 to 400 ~m in the zone of a thinned-down area
17, wherein the thickness within the thinned-down area 17
is smallest in the center, that is the region of the groove
line 12. The thinned-down area 17 is delimited by edges 34
on the sides, at which also the gluing between the cardboard
blank part 1 and the foil blank part 3 can end. As is seen,
the thinned-down area 17 extends across the entire overlap
length of both blank parts 1 and 3.
j~ ,
~ ~ ";
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iX~292
The placement of the thinned-down area 17 can occur
simultaneously with the placement of the bend line 13 in one
single work process using procedures common for placement
of bend lines, for instance by high frequency heating of
the foil with simultaneous application of pressure. Bend
lines produced in this manner yield particularly bendable soft
bending edges.
The tbinned-down area 17 compensates for stresses and
consequent deformations occurring in the foil material at the
overlap spots during folding, without which the cardboard
material is stretched so that it tears at the edge overlap
points. Residual stresses can occur particularly with thicker
foils during folding in the transition ~one between the
thinned-down area 17 and the original foil material o~ the
wall parts 14 and 16; this is because the bend line 13 has the
desirable tendency to migrate somewhat towards the outside dur-
ing the folding process, in order to form a practically step-
less continuous box edge by alignment with the groove line 12.
It is necessary to avoid damage of the cardboard blan~
part at the boundary to the viewing area of the window opening 2
as well as possible warping in the area of the foil material of
the wall parts 15 and 16 adiacent to the overlap spot. Therefore,
to absorb such residual stresses a line-shaped incision 48
is made in the ~oil blank part 3 in the embodiment form
according to the Fig. 14, lS at the juncture between the
~l2~ 9~
bend line 13 and the thinned-out area 17, said incision
passing through the material thickness of the foil blank part
3. The incision 48 protrudes on both sides beyond the bend
line 13 and extends parallel to the near edge of the cardboard
blank part 1. The smaller the distance of t~e incision
48 from the mentioned neighboring edge of the cardboard blank
part 1, the less prominent is the incision when the folding
box is erected, as is shown in Fig. lS. In this case,because
of the explained outward migration of the bend line 13 during
~ 10 the folding process,there is generated only a very small
downwardly oriented opening (referred to the illustration
according to Fiq. 15) at the separation point at the box
edge defined by the incision 48.
In the embodiment of the separation discernible from
Figs. 16 and 17, said separation is constructed as a circularly-
shaped hole cutout 49, which separates the bend line 13 from
the thinned-out area 17 and is only in outline overlapped
by the cardboard blank part 1. The hole cutout 49 protrudes
with approximately equal surface regions towards both sides
202 beyond the bend line 13, as can be discerned from Fig 16.
It has been seen that a comparatively small diameter of the
,hole cutout 48 in relationship to the width. of the thinned-
out area 17 is sufficient in order to cause the above-mentioned
additional stress equalization at the junction point between
the bend line and the thinned-out area 17 to occur. Because
of the small diameter,the hole cutout 49 is scarcely noticeable
when the folding box is erected, as is made clear in Fig. 17.
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~L2~ 2~2
In the embodiment accordin~ to Figs. 18 and 19, the
hole cutout constituting the separation is constructed in
the shape of an ellipse 50, longer axis of which extends
parallel to the neighboring edge of the cardboard blank part.
In this case also the ellipse 50 protrudes with approximately
equal surface areas to both sides of the bend line 13 and
is only slightly overlapped by the cardboard blank part 1.
The smaller diameter of the ellipse is made to be so small,
that the box edge of the erected box constituted by the
bend line 13 and the groove line 12 is only slightly in-
terrupted. In the illustrated example,the largest diameterof the ellipse 50 is considerably smaller than the width of
the thinned-out area 17, which,because of the increased
scale in the Figs. 14, 16 and 18,appears to be in any case
wider than it is in actual practice.
The geometric versions of the hole cutout discernible
from the Figs. 16 and 18 are only given by way of preferred
examples. Deviating geometric configurations such as, for
instance, polygons are also possible if only an approximately
symmetrical arrangement with reference to the bend line 13
and the groove line 12 is provided and the other indicated
conditions are observed.
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