Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND DEVICE FOR PROTECTIVE WRAPPING OF STACKS OF
PRINTED PRODUCTS
The invention belongs to the field of packing technology and relates to a
method and
a device according to the generic terms of the corresponding independent
claims.
Method and device serve for putting a protective wrapper around stacks of
printed
products. Method and device according to the invention are especially suited
for
application in connection with stacks of printed products having an edge
region
which edge region is thicker than the other regions and therefore decreases
stack
stability and which edge region needs to be protected in particular. Printed
products
of this kind are e.g. doubly folded newspapers with a folded edge (edge of the
second
l0 fold) or magazines with a glued or stitched spine.
Newspapers are supplied by rotation presses, from reels or by various devices
for
further processing (e.g. collating drum) in form of a scaled stream in which
the
newspapers are positioned with their folded edges facing downstream. For
transport
and distribution, these newspapers are stacked (mostly in cross stacks), the
stacks are
optionally equipped with a cover sheet and the stacks are then strapped and/or
wrapped.
In a doubly folded newspaper, the front page constitutes its outer surfaces
and the
printed information continues across the folded edge substantially without
interruption. This means that the front page is very exposed. On the other
hand, the
front page of the newspaper, being well visible, usually carries information
which is
considered important and for this reason should not be impaired. This however,
as
will be shown, is not simple.
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The same can be said about magazines or similar printed products in brochure-
form
having a glued spine or being bound in another manner. Such products have
spine
edges with an increased thickness which reduces stack stability. These spine
edges
may carry printed information and are in the stack exposed and therefore prone
to
getting damaged.
Newspaper and magazine stacks are, even when stacked crosswise, less stable in
a
direction perpendicular to the folded edges or spines (edges distinguished by
their
to increased thickness) than in parallel to these edges. This is due to the
fact that even
when stacked on a horizontal support a part of the products in the stack is
sloping in
a direction perpendicular to the distinguished edges and therefore, tend to
start
slipping even at a low momentum This is not the case in the direction parallel
to the
distinguished edges. For this reason, shifting such a stack in parallel to the
distinguished edges is considerably less difficult, i.e. it can be carried out
with
considerably simpler means and with greater accelerations than shifting
perpendicular to the distinguished edges. Therefore, stacking shafts are
usually
designed such that the stacks being produced in the shaft are ejected in a
direction
perpendicular to the distinguished product edges.
According to the state of the art, stacks are wrapped with a wrapping material
(e.g.
plastic sheet of foil) by moving them through a curtain of wrapping material
put up
in a substantially vertical manner. Thereby, the wrapping material is wrapped
around
the downstream side of the stack and can be closed on the upstream side of the
stack
to form a ring-shaped wrapping. At the same time, the wrapping material is
severed
in such a manner that it again forms a curtain for the following stack. If
according to
the named method, a stack is to be wrapped in such a way that the
distinguished
edges (e.g. folded edges or spines) of the stacked products are protected by
the
3o wrapper, the stack must be moved through the curtain of wrapping material
in a
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direction perpendicular to the distinguished edges, which, as mentioned above,
leads
to problems due to the low stack stability.
For wrapping newspaper or magazine stacks it is e.g. suggested to push the
stacks
through the curtain of wrapping material directly when being ejected from the
stacking shaft. This can be done without problems if the stacks are ejected in
parallel
to the distinguished edges and are wrapped in parallel to these edges.
However, this
leads to a wrapper which does not lay tightly against the distinguished
product edges
and thus does not protect these. It is also suggested to eject the stacks in a
direction
perpendicular to the distinguished product edges and to move them directly
through
the curtain. This leads to a wrapper which lays tightly against the
distinguished
product edges and effectively protects these. This method leads to the desired
product but is afflicted with problems due to the low stack stability in
ejection
direction. These problems cannot be solved satisfactorily for high speeds and
high
accelerations on ejection.
In view of the above mentioned problems it is also suggested to eject the
stacks from
2o the stacking shaft in a direction perpendicular to the distinguished edges
and to strap
them immediately after being ejected perpendicular to the ejection direction
for
giving them enough stability for being wrapped. In such a way wrapping for
protecting the distinguished edges is rendered problem-free but the strapping
prior to
the wrapping constitutes a high risk of damaging the distinguished edges.
There seems to be no satisfactory method with which in a stack of printed
products,
edges distinguished by increased thickness, e.g. the folded edges or spines of
newspapers or magazines, can be protected in a lasting manner by means of
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wrapping as it is possible for packages of rolled printed products, the
manufacture of
which also belongs to the state of the art.
Publication US-4341056 describes a device for wrapping stacks which stacks are
to
be pressed as strongly as possible in wrapped condition. In order to not have
to create
the pressure with the wrapping, the stack is pressed between pressing jaws, is
wrapped together with the jaws and is then separated from the jaws.
Therefore, it is an object of the invention to create a method and a device
making it
possible, with simple means and at high speeds, to eject from a stacking shaft
stacks
of printed products having an edge distinguished by increased thickness in a
direction parallel to these edges and to wrap the stacks immediately
afterwards with a
protective wrapper such that the wrapper fits tightly to the sides of the
stack on
which the distinguished edges are positioned. Furthermore, the inventive
method and
the device for carrying out this method are to be applicable for the serial
wrapping of
stacks with different individual heights.
ZO
This object is achieved by the method and the device as defined in the patent
claims.
The inventive method is based on the idea of ejecting stacks from a stacking
shaft in
a direction parallel to the distinguished product edges and immediately on
ejection,
positioning them between two forks forming a pair of forks. Then the stack is
pressed
between the forks, the pair of forks is moved through the curtain of wrapping
material together with the pressed stack and the wrapping material is closed
on the
upstream side of the pair of forks. Then the wrapped stack is separated from
the pair
of forks by moving the stack relative to the forks. This means that the
movement of
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the stack necessary for the wrapping procedure is carried out in a direction
perpendicular to the distinguished edges which however does not cause any
problems
as the stack is clamped between the forks and such stabilized and can
therefore be
moved quickly and without problems even against the resistance of the wrapping
material.
Because the wrapping is initially positioned not around the stack but around
the stack
pressed together by the forks, i.e. is fitted and closed around the stack and
the pair of
1o forks, and because the pair of forks is separated from the stack by drawing
the forks
out of the wrapper, the inventive method produces a taut wrapping only if the
printed
products are sufficiently elastically compressible in their thickness and/or
if the
wrapping material is of sufficient elasticity such that it can contract to a
sufficient
tightness around the stack after withdrawal of the forks.
It shows that with the inventive method, stacks of newspapers or magazines of
usual
height can be fitted with a protective wrapper of polyethylene sheeting of a
thickness
of 15 to 50 ftm without problems. The wrapped stacks can then easily be
strapped or
further processed in any suitable manner.
The inventive method and the inventive device are described in more detail in
connection with the following Figures, wherein
Figure 1 shows a stack of newspapers or other printed products having
an edge distinguished by increased thickness, the stack being
wrapped in a protective wrapper;
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Figure 2 shows a diagram of the successive steps of the inventive
method;
Figures 3 and 4 show in a schematic manner two exemplified embodiments of
the inventive device;
Figure S shows an exemplified embodiment of a pressing fork being
additionally equipped for positioning a cover sheet on the
stack.
Figure 1 shows a stack 1 of printed products 2 having each one edge 3
distinguished
by increased thickness, e.g. a stack of newspapers or magazines with folded
edges or
spines respectively. In the shown stack all distinguished edges are arranged
superimposed on the same side of the stack such that the stack has a greater
height on
this side than on the opposite side. The stack could also, however, be a cross
stack in
which groups of printed products (part stacks) are stacked on top of each
other such
that the groups of distinguished edges are arranged alternatingly on two
opposite
sides of the stack. In a cross stack the instability due to the edges of
increased
2o thickness is less important than in a stack as shown in Figure 1. All the
same, the
instability exists and cannot be neglected when handling cross stacks.
The stack 1 in Figure 1 comprises a protective wrapper 4 which surrounds the
stack
in a direction perpendicular to the distinguished edges 3 and which is at
least as wide
as the length of the distinguished edges. The wrapper covers tightly the
lateral
surfaces of the stack in which the distinguished edges are arranged as well as
the
lower side of the stack and to the upper side of the stack and it protects the
distinguished edges well. The wrapping material may protrude from the stack on
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both sides and the protruding wrapper parts can, in a further processing step,
e.g. be
closed across the uncovered sides of the stack such protecting the stack on
all sides.
The wrapper 4 of the stack as shown in Fig. 1, has apart from a protecting
function
also an at least limited stabilizing function. The wrapped stack can be
accelerated in
a direction perpendicular to the distinguished edges with considerably less
problems
than the not yet wrapped stack.
to
Figure 2 shows successive steps a to a of the inventive method for producing a
protective wrapper 4 around a stack 1, e.g. around a cross stack comprising
three
crosswise stacked product groups. The viewing direction is in parallel to the
distinguished edges. The steps are the following:
a A stack 1 is ejected in a direction parallel to its distinguished edges 3
from a
stacking shaft, into an ejection position, the stack being guided laterally
and
on its face-side by ejection guides (10/10', 11/11') and being positioned on a
carrier fork 12 (ejection direction perpendicular to the paper plane of the
figure).
b In the ejection position, a pressing fork 13 is lowered onto the stack 1,
the
stack 1 is pressed between carrier fork 12 and pressing fork 13 and the
ejection guides (10/10', 11/11') are at least partly removed from their
guiding
position.
c The stack 1 being pressed between carrier fork 12 and pressing fork 13 is
moved in a direction perpendicular to the distinguished edges through a
curtain 14 of a wrapping material into a wrapping position.
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d The wrapping material is closed on the upstream side of the pair of forks
12/13 and stack 1 to form a protective wrapper 4, by e.g. producing a
connection 15 each on wrapping 4 and curtain 14.
a Stack 1 and fork pair 12/13 are separated from one another by a relative
movement in a direction parallel to the distinguished edges between stack 1
and fork pair 12/13, the separation being carried out in the wrapping position
or advantageously in a separation position into which the pair of forks 12/13
and stack 1 are moved before the separation.
to
The steps c, d and a are shown in two embodiments being depicted in an upper
and a
lower part of the figure. According to the upper embodiment, the pressed stack
1 is
moved through the curtain 14 of wrapping material without change of
orientation
such that the wrapping material must be connected on a side of the stack
containing
distinguished edges (connection 15). For an even better protection of the
distinguished edges this is prevented according to the embodiment depicted in
the
lower part of Fig. 2 by rotating the stack 1 pressed between forks 12 and 13
by 90°
between the ejection position (b) and the wrapping position (c) such that
either fork
12 or 13 constitutes the downstream side of the stack. The connection 15 is
therefore
made at a distance from the printed products and there is no risk of damaging
the
products or their distinguished edges.
Figure 2 diagrammatically shows the most important parts of the inventive
device.
These are the following:
~ The lateral and face-side ejection guides 10/10' and 11/11' arranged in the
ejection position and being at least partly able to be displaced from a
guiding
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position (a) into a rest position (b), e.g. vertical shifting of upper (10,
11) and
lower (10', 11') guide elements;
~ The pair of forks 12/13, which is able to be moved from the ejection
position into
the wrapping position and possibly from the wrapping position into a
separation
position, the pair of forks comprising the Garner fork 12 and the pressing
fork 13,
the two forks being able to be pressed against each other and in the ejection
position, the two forks having a distance from each other which corresponds to
at
least the stack height (possibly the pair of forks is in addition able to be
moved
1o for the separation and/or to be rotated between ejection position and
wrapping
position around its own axis by 90°).
~ The known means for positioning the strapping material as a substantially
vertical curtain 14 at the entrance to the strapping position (c, d) and for
connecting and severing it on the upstream side of the stack to form a
connection
15, e.g. on the closed wrapper 4 and on the newly formed curtain 14.
The device for carrying out the inventive method further comprises separating
means
(not shown in Fig. 2) for separating stack 1 from the pair of forks 12/13. The
separating means are e.g. pins able to be introduced into slots of the forks
12 and/or
13 and to be moved relative to the pair of forks 12/13 in a direction parallel
to the
distinguished edges (as shown in Fig. 3).
Figure 3 shows a diagrammatic top view of a possible spatial arrangement of
the
parts of the inventive device. An arrow S indicates the supply of printed
products 2
with distinguished edges 3 (shown by means of a bold line) positioned
downstream.
The products 2 are e.g. supplied as a scaled stream. The products are supplied
to a
3o stacking shaft 20 to form a stack 1. The stacking shaft 20 is arranged such
that the
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stack 1 is ejected in a direction substantially perpendicular to the supply
direction
(arrow S). The lateral and face-side ejection guides 10 and 11 of the ejection
position
and the pair of forks 12/13 of which only the pressing fork 13 is visible are
arranged
on the ejection side of the stacking shaft. The pair of forks 12/13 is movable
in a
direction perpendicular to the ejection direction (in parallel to the supply
direction)
through the curtain 14 into the wrapping position. For separating the wrapped
stack
from the pair of forks, e.g. in the wrapping position, pins 21 are inserted
into slots 22
of the forks and are moved towards the end of the fork (arrows B) while the
pair of
forks 12/13 remains stationary. Through this movement of the pins ,21 the
wrappet~
1o stack 1/4 is separated from the pair of forks and is then conveyed away
(arrow W)
e.g. on a conveying belt (not shown) in a direction perpendicular to the
supply
direction (arrow S).
A device, as shown in Figure 3, is operable with a single pair of forks 12/13
if it is
equipped with means for moving the pair of forks back an forth between the
ejection
position and the wrapping position. For an increased capacity of the device it
is
advantageous to equip the device with a plurality of pairs of forks 12/13, the
pairs
being e.g. arranged equidistantly on an endless chain and being moved stepwise
by
this chain along a closed path. Fig. 3 shows two pairs of forks 12/13 and part
of a
driving chain 23.
It is easily seen from Fig. 3 that the path of the fork pairs 12/13 can pass,
in addition
to the ejection position, further processing positions e.g. arranged in a
line: e.g. a
processing position following downstream after the wrapping position and being
equipped for e.g. printing on the wrapper of the stack or for closing parts of
the
wrapper protruding from the stack etc. Downstream of a plurality of such
processing
positions, follows a separation position for separating the wrapped stack from
the
3o pair of forks 12/13, which according to Fig. 3 is done in the wrapping
position. Of
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course, there may be additional processing positions between the ejection
position
and the wrapping position for processing the not yet strapped stack.
The individual parts of the device shown in Fig. 3 as well as the drives and
guide
means necessary for its operation can easily be designed by one skilled in the
art and
therefore, need not be shown and described in more detail here.
Figure 4 shows a further, exemplified embodiment of the device for carrying
out the
inventive method. The function of the device parts are the same as in the
device
shown in Fig. 3. The same reference numbers are used for the device parts. The
device comprises four pairs of forks 12/13 which are arranged around a
substantially
vertical axis 30 spaced from each other by 90°. The axis is driven to
rotate in the
direction of the arrow. The ejection position (9 o'clock position), the
wrapping
position (6 o'clock position) and the separation position (3 o'clock position)
are
arranged in a circular manner, also spaced from each other by 90°.
Obviously it is
also possible to arrange a processing position in the 3 o'clock position and
the
separation position in the 12 o'clock position.
In similar devices to the one shown in Fig. 4 there may be more or Less than
four
pairs of forks 12/13 arranged at regular angles.
Figure 5 shows a pressing fork 13 with an additional function. The fork is
equipped
with a movable compartment for a cover sheet 31 or other flat product to be
positioned on a stack in the ejection position. The pressing fork 13 is shown
in two
positions, above in a position distanced from an ejected stack and below in a
position
3o lowered onto the stack 1.
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The pressing fork 13 comprises a compartment 32 which is fastened on its the
lower
side in a pivoting manner such that in a force-free status it is distanced
from the free
end of the fork and can receive between fork 13 and compartment 32 a cover
sheet .
e.g. directly from a printer. When the fork 13 is lowered onto a stack 1 the
compartment 32 is pressed against the lower side of the fork and is thus
substantially
closed. When separating the wrapped stack and the pair of forks the
compartment 32
is pulled out of the wrapping together with the pair of forks and the cover
sheet
i0 remains on the stack 1.
Although the inventive method and the inventive device are designed for stacks
of
products with an edge distinguished by increased thickness they can obviously
also
be used for products without such edges.
