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Description  |
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The present invention relates to a printing apparatus which makes it
possible to exchange a cylindrical printing plate quickly without having
to remove the entire impression cylinder or the cylinder receiving shaft
from the apparatus.
An ever greater quality is demanded for printed products in particular when
printing on narrow strips, such as for example labels, blanks for
cigarette packs or similar blanks for the packaging industry which are
produced, for example, by means of gravure processes or in the production
of commercial prints, such as catalogues or brochures, which are often
produced in a very small edition, for example using flexographic printing
processes. The machine downtimes when changing over the machine are to be
reduced to a minimum. At the same time, it must be possible to print even
small editions of the widest variety in a cost-effective way. Even today
this demands a frequent exchange of the impression cylinders, a fact which
leads to considerable downtimes of the machine.
It is the object of the present invention to avoid the disadvantages of the
prior art and to propose a printing apparatus with which a simple and
quick exchange of the printing plate is possible. The object is achieved
according to the invention by the fact that the impression cylinder is
rotatably mounted on the drive side of the machine and the free end of the
impression cylinder is arranged to be suspended from the ground in order
to permit an unhindered attaching or a simple fitting of a cylindrical
printing plate.
The rotatable mounting of the impression cylinder at only one end makes it
possible to draw cylindrical printing plates onto the impression cylinder
in a simple and quick way. The printing plates can thus be exchanged
quickly and simply and are clamped on the impression cylinder using known
cylinders variable in their diameter.
There is also the possibility of making the change of the printing plates
automatic.
Further features of the invention can be taken from the following
description, the subclaims and the attached drawings.
The subject of the invention is now described in more detail with reference
to a number of exemplary embodiments and is represented diagrammatically
in the drawings, in which:
FIG. 1 shows an impression cylinder which is mounted so as to be freely
floating with respect to the printing apparatus;
FIG. 2 shows an impression cylinder of a longer design which is mounted on
one side of the apparatus and is supported at its other end by an
auxiliary apparatus;
FIG. 3 shows a view of a carriage for the transporting of tubular printing
plates; and
FIG. 4 shows a diagrammatic view of a cableway for feeding the printing
plates.
As FIG. 1 reveals, the frame 1 of the printing machine has a mounting, for
example in the form of rolling bearings 2 and 3 which are fitted in the
machine frame 1, only on one side. The bearings 2 and 3 receive an
extension in the form of a shaft 4 projecting from the impression cylinder
5. The shaft 4 is in effective connection with a gear wheel 6, which is
driven by known driving means of the printing machine.
As FIG. 1 also reveals, that impression cylinder 5, mounted on the frame so
as to be suspended from the ground, is suitable for receiving a
cylindrical printing plate 18. The printing plate 18 is drawn onto the
impression cylinder 5 from the end face of the latter, as represented by
the arrow f. The cylindrical printing plate 18 is fixed on the impression
cylinder 5 by the provision of known clamping devices. The impression
cylinders 5 are, for example, variable in their diameter in order thereby
to clamp the printing plate.
As revealed by FIG. 1, the cylindrically designed printing plate 18 can be
slid onto or slid off the impression cylinder 5 in an unhindered manner
since when the printing plate is drawn off from or drawn onto the
impression cylinder 5, impression cylinder 5 is supported above the ground
in a cantilever-like manner with only one end of the impression cylinder
being supported by shaft 4, and since inking device 8 is arranged
displaceably with respect to the cylinder 5. In the exemplary embodiment
according to FIG. 1, this is performed using a raising and lowering
device, for example a hydraulic piston-cylinder unit Z, which is connected
to the inking device so that the inking device can be raised and lowered
with respect to the impression cylinder. If the inking device 8 is in the
lowered positions (represented by dot-dashed lines), it can be seen that
in this case the impression cylinder 5 has a completely accessible end and
as a result, a quick fitting or detaching of the printing plate 18 on the
cylinder 5 is possible. This arrangement has proved particularly
advantageous in small print runs.
Apart from a lifting and lowering movement, the inking device 8 can also be
moved away from the printing apparatus 1. For this purpose, it is
sufficient for the inking device 8 to be designed as a carriage. This
possibility simplifies the usual cleaning and maintenance work on the
moved-out inking device 8.
The shaft 4 which projects from the cylinder 5 is assigned on the bearing
side (2, 3) a device known from the prior art for in-register setting of
the cylinder 5 in the axial direction, i.e. in the direction of the arrow
g. Since this setting device is generally known, a precise description has
not been included. In order to admit a pressure medium to the impression
cylinder 5 and, by varying the cylinder diameter, carry out a clamping of
the cylindrical printing plate on the cylinder 5, the end of the shaft 4
has a connection piece 9, via which a pressure medium can be introduced
into the interior of the impression cylinder 5. The pressure medium causes
the cylinder 5 to expand and, as a result, clamp the cylindrical printing
plate 18. A further exemplary embodiment of an impression cylinder 5 is
represented in FIG. 2. This impression cylinder 5 is also freely
accessible through sidewall 1a in order to permit a simple attaching or
drawing off of the printing plate 18.
In the case of this exemplary embodiment, the cylinder 5 is also assigned
splash guards 10, which are provided on the ends of the cylinder 5 and can
be displaced from a position represented by solid lines into a position
represented by dot-dashed lines.
As FIG. 2 also reveals, the cylinder 5 represented has a second shaft 11 in
the form of a projecting hub, which is fitted with a rolling bearing 12.
In order to avoid this hub or shaft 11 tending to oscillate or vibrate
under the rotary drive of the cylinder 5 on account of the greater overall
length of the cylinder 5, the rolling bearing 12 advantageously rests on a
bearing plate 13 which is in effective connection with the rod 14 of a
hydraulic piston 15 or a similar lifting means.
If a printing plate 18 on the impression cylinder 5 is to be exchanged, it
is necessary to free the opening 16 in the side wall la of the machine
frame. All that is needed to do so is to lower the bearing plate 13 while
the impression cylinder 5 is at a standstill by actuating the piston 15.
As a result, the opening 16 is free for an unhindered introduction of a
new printing plate 18 and a quick fitting of the printing plate 18 in the
direction of the arrow f becomes possible.
Of course, the splash guards 10 are also raised with the assistance of
pneumatic or hydraulic actuating means in order to be moved into the
position represented by dot-dashed lines. The inking device 8 is also
displaced into the moved-down position represented by dot-dashed lines.
It has proved to be extremely helpful to arrange in the wall 1 of the
machine frame a cylinder 21 of which the piston rod 17 acts on the end
face of the printing plate 18 when there is heavy caking (caused by the
inking), in order to dislodge this from the impression cylinder 5 and
thereby make it easier to draw off the printing plate 18.
In order to permit quick and simple exchanging of the printing plates 18,
it is advantageous to provide a carriage 19 for the feeding and storage of
the printing plates 18 according to FIG. 3. This carriage 19 has a series
of elevations 20. The printing plates 18 can be fitted onto these
projections 20 in an upright position.
Consequently, by use of a carriage 19, the printing plates 18 are
transported into the vicinity of the apparatus for the cylinder 5 of which
a tubular printing plate 18 is about to be exchanged. After the printing
plate 18 has been drawn off the corresponding cylinder 5, the no longer
required printing plate is fitted onto the free projection 20 of the
carriage, after which a new printing plate 18 is taken from the carriage
19 in order to be drawn onto the exposed impression cylinder 5. After
in-register positional arrangement of the printing plate 18 on the
cylinder, once again a clamping of the printing plate 18 on the cylinder 5
is carried out and the printing apparatus is available for new printing
operations.
A further transporting device 101 for the transporting of the printing
plates 18 is represented in FIG. 4. This device 101 consists essentially
of an overhead conveyor line or conveyor chain 100, which spans the
distance from the store for the printing plates 18 to the printing machine
1. The holding device 101 has peg-like holders 102, which can be spread
apart and make it possible to hold the printing plate during the
transporting movement and to release the printing plate 18 only when in
the vicinity of the printing apparatus. Of course, the holding device may
also be designed in the manner of a yoke and have a plurality of holders
102 for a plurality of printing plates 18.
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