Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
ANTI-WRAP UP DEVICE FOR WEB FED PRINTING PRESSES
This invention relates to an apparatus for protecting the prlnting unit of
a web fed printing press, usually the printing cylinders, against damage that
can be caused by paper wrapping around on the blanket cylinder when there is a
break in the web after it has left the printing unit. Generally, the
apparatus comprises free turning rotational inertia means that cooperate in
gripping the web between them and which are driven by the web so that they
continue to draw the web forwardly when there is a web break downstream of the
apparatus.
Background of the_Invention
Prior Art-
In the production of printed web materials, as for example through the use
of a web fed offset printing press, it is known that the web leaving the last
printing unit carries ink which is not yet dry and it is further known that
the web after leavin~ the press is often subject to rupture or breakage. When
such breakage occurs, ~t is the normal occurrence that the broken end of the
web will wrap around one of the rolls of the last printing unit, usually the
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blanket roll, and cause damage. Even if no damage results from the web
wrapping around the blanket cylinder, it is difficult and time consuming to
remove the wrapped around web from the press. Therefore, it has been known in
the prior art to provide apparatus which is designed to prevent a broken web
from wrapping around cylinders that are contained in the printing unit
1tself. In most of the prior art the web carrying wet ink passes between a
pair of spaced apart rolls, so that the ink is not smeared, which rolls are
designed to move together when a sensor detects a break in the web. Typical
of this form of apparatus are those described in U.S. Patent 4,549,485 and in
Br1tish Patent 1408176. In U.S. Patent 4,549,485 there are provided a pair of
opposed gripping rollers 3 and 15 which are spaced apart during normal
operat1On of the press but which can be moved into contacting relationship
with the web when the web 1s ruptured. The movement of the rolls toward each
other 1s effected when a suitable sensor such as a web tension sensor, detects
that the ~eb has been broken. A somewhat similar arrangement is described in
the British Patent which was noted above. In both the U.S. patent and Tn the
Brit1sh patent the rolls that grip the web are driven by some suitable outside
dr1ving apparatus.
In another type of apparatus, specif1cally that described in U.S. patent
4508033, there are prov1ded a pair of opposed rolls 14 and 15 which are rubber
covered and are in constant contact with the traveling web. In th1s case the
rolls are dr1ven at a peripheral speed which is slightly greater than the
llnear speed of the printed web so as to maintain tension on the web that is
ex1ting from the printing press.
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It has been determined that whlle apparatus of the type re~erred to above
are somewhat effective they still are not totally effective because on the one
hand the reaction to grip a broken end depends upon senslng that the web has
already been broken so that the gripping rolls do not always advance the web
coming from the press in a reliable fashion. In addition, all of the rolls
are driven so that speed adjustments must constantly be maintained to insure
that there is uniformity of rotational speed of the gripping elements and the
linear speed of the web to maintaln proper tension. In addition, where the
rolls are in total contact with the traveling web there is the problem of
smearing or otherwise disturbing the ink that has been printed on the
travellng web.
Summary of the Inventlon
It is therefore a principal object of this lnvention to provide an
improved capturing device for continuously withdrawing printed web from the
last prlnting stand when a rupture has occurred downstream from the capturing
apparatus.
It is a further object of this invention to provide an anti-wrap up device
in which the gripping element are driven by the web so that the speed is
identical to that of the traveling web.
An additlonal object of this lnvention is to provide an antl-wrap up
devlce in whlch laterally adjustable gripping rlngs are provided that permit
the travellng web to be gripped in pre-selected positions in non print areas.
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In accordance with an embodiment o~ the invention,
in an offset lithographic printiny press haviny support
frame apparatus, a printiny couple comprised of a blanket
cylinder and an impression cylinder mounted on the frame
apparatus web capturing apparatus mounted on the frame
apparatus, downstream of the printing couple *or protecting
the printing couple from damage in the event of web breakage
after it exits the printing couple, the capturing apparatus
comprised of a pair of web capturing inertial rollers
between which the web passes, each of the rollers having a
plurality of circular web gripping rings mounted thereon for
contact with the traveling web, bearing apparatus freely
rotatably supporting the rollers on the support frame
apparatus with the gripping rings in normal constant contact
with the web so that the rollers are rotatably driven sol~ly
by the web, throw-out apparatus operatively associated with
the bearing apparatus supporting one of the inertial rollers
whereby the bearing apparatus can be moved to a position at
which the gripping rings of the one supported roller are not
in contact with the web, and apparatus providing adjustment
of the gripping rings laterally along the axis of rotation
of the inertial rollers for positioning the gripping rings
in the margins between printed columns on the web.
Other and additional objects of this invention
will be in part obvious and in part explained by reference
to the accompanying specification and drawings in which:
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Fig 1 is a side elevation of the anti-wrap up device of this inventlon
showing cooperating free turning rotational inertia means mounted as they
engage the traveling web; and
Fig. 2 is a front elevation of a portion of the anti-wrap up device of
Figure 1 showing the manner in which the free turning rotational inertia means
are journaled in the ~rame and showing the manner in which the gripping means
contact the traveling web.
Description of the Preferred Embodiment
Referring to Fig. 1 of the drawings, there is shown a horizontally
disposed traveling web 10 that passes between a pair of free turning
rotational inertia means 11 and 12, hereshown as a pair of opposed rollers.
It should be pointed out that although rollers are shown here as one
embodiment it should be pointed out that any other inertial gripping means
such as trolleys or wheels etc. may be used. The important thing is that the
inertia means be in constant contact with traveling web 10 and be of
sufficient mass as to provide continued rotation and contact with the web in
the event of a web break downstream from the gripping apparatus.
The rollers or inertia means 11 and 12 are shown as being journaled in
frame 15 b~ means of stub shafts 16 and 17 that are disposed within bearings
18 and 19 respectively. As can be seen most clearly in Fig. 2 of the
drawings, a throw out mechanism 20 is provided for moving the upper roll 11
toward and away from the lower roll 12 to provide for disengagement when
desired.
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Since the ink on traveling web 10 is wet when it enters the nip between
the inertia means or rollers 11 and 12, the apparatus of this invention
provides gripper means 25 which take the form Gf rings that are disposed about
the periphery of the inertia means 11 and 12. The gripping rings 25 may be
secured to the rolls 11 and 12 by means of set screws or other fastening means
so that they may be loosened and adjusted laterally along the length of the
axis of the rollers 11 and 12. This is done in order that the rings can be
placed in the non-printed areas which exist between printed columns on the
web. In this manner the possibility of smearing or smudging or otherwise
disturbing the freshly printed matter is eliminated.
In operation, the throw out mechanism is used to move the roll 11 away
from roll 12 as the web 10 is threaded through and on into subsequent
processing apparatus such as a dryer or the like. The throw out mechanism
then lowers the roll 11 into contact with the web as illustrated in Figure 2
and the printing operation is initiated. It is obvious that as the web is
drawn between the inertia means or rollers 11 and 12, it causes the rollers to
rotate at exactly the same speed as the traveling web. In the event of a web
break after the capturing or anti-wrap up device the inertial movement of the
tvo opposing inertia means 11 and 12 will continue to draw web through the nip
between them and prevent any wrap up about the printing rolls in the last
printing unit. This device then does not require a signal to activate its
capturing function, since the inertia of the device wants to continue to
rotate even if the web is broken and wants to go slack. Therefore, it does
not experience a delay and keeps the web in tension back to the printing
unit. The loose end of the web is then accumulated past the anti-wrap up
device (in a location that wi11 not cause damage and is easy to clean~.
