The present invention relates generally to printing presses, and more
particularly to a rolling element adjustment system for an offset printing press.
BACKGROUND OF THE INVENTION
Offset printing presses are well known in the art. Typically, water
and ink are supplied to a printing plate cylinder, and are then transferred to a
blanket cylinder for printing onto sheets or web, fed between the blanket cylinder
and an impression cylinder. The water supply to the plate cylinder usually comprises
a dampening unit having a dampening form roller which contacts the plate cylinder
and is fed water from a water pan through intermediate water transferring rollers.
Similarly, an inking unit transfers ink through one or more ink form rollers contacting
the plate cylinder, the ink form rollers receiving ink from an ink supply through
a series of ink transfer rollers.
While such presses have fixed lateral dimensions, and as such printed
products wider than the length of the cylinders cannot be produced, the circumference
of the rotating cylinders determines the length of each repeated pattern being printed
onto the web or sheets passing therethrough. Accordingly, the larger the circumference
of the plate and blanket cylinders being used, the longer the printed pattern that
can be produced. Therefore, in order to permit a press to be modified to permit
printing of different lengths of printed patterns, standard variable size presses
provide a changeable insert comprising plate, blanket and impression cylinders.
Replacement inserts comprising cylinders of different diameters can therefore be
used with the same press.
An important parameter determining printing quality is the line of
contact between two cylindrical rollers in contacting engagement, otherwise known
as the contact stripe. Standard adjustment mechanisms between rollers and cylinders
include mechanical means such as bolts or screws and single pneumatic actuators,
to allow fine tuning of the contact stripe between, for example, the inking or dampening
form roller and the plate cylinder. However, conventional adjustment mechanisms
are usually adapted to be used with plate and blanket cylinders of fixed diameter.
On standard variable size presses, mechanical stoppers are usually
included in the insert in order to adapt the adjustment mechanisms of the form rollers
and cylinders to the plate and blanket cylinder diameter. Such stoppers offer only
an adjustment having a limited precision.
Sleeve offset presses, such as the one disclosed in US Application
No. 60/457,295 by the applicant and incorporated herein by reference, provide for
replacing only the plate and blanket cylinders, thereby eliminating the need for
the various inserts. While the elimination of the inserts minimizes the complexity
of changing cylinder sizes and reduces the storage space previously required for
replacement inserts, it also eliminates the support for the prior mechanical stoppers.
Integrating the stoppers directly on the cylinder bodies greatly increases their
weight and cost. Alternatively, providing a different adjustment mechanism for each
cylinder size can be very costly as well as increase the storage space necessary
for spare parts and the down time when the cylinders are changed.
Accordingly, there is a need for a unique adjustment mechanism providing
an adequate contact stripe adjustment between rolling elements in a printing press
and being able to accommodate various dimensions of plate and blanket cylinders.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved adjustment
system for rolling elements in an offset printing press.
Therefore, in accordance with the present invention, there is provided
in a printing press an adjustment system for positioning a rolling element relative
to a first cylinder having a first outer diameter and relative to at least a second
cylinder adapted to replace the first cylinder and having a second outer diameter
different than the first outer diameter, the adjustment system comprising an actuating
member operable to displace the rolling element relative to the first cylinder,
the actuating member having first and second ends, the first end being pivotally
connected to a frame of the printing press and the second end being mechanically
linked to the rolling element, the actuating member providing sufficient displacement
to bring the rolling element into contact with the first cylinder such that a predetermined
contact pressure therebetween is reached, the actuating member also being operable
to bring the rolling element into contact with the second cylinder such that the
predetermined contact pressure therebetween is reached.
Also in accordance with the present invention, there is provided a
method for displacing a rolling element relative to at least a cylinder in a printing
press, the rolling element being mechanically linked to an adjustment system composed
of first and second independently controllable adjustment mechanisms, the method
comprising the steps of setting the first adjustment mechanism to a predetermined
length so that a total length of the adjustment system is such that the rolling
element is out of contact with the cylinder, and extending the second adjustment
mechanism such as to bring the rolling element in contact with the cylinder until
a desired contact pressure therebetween is reached.
Further in accordance with the present invention, there is provided
an offset printing press including at least a first cylinder and a rolling element
mounted in a frame structure in serial contactable engagement, the printing press
comprising an adjustment mechanism operable to displace the rolling element between
a predetermined printing position, wherein the rolling element and the first cylinder
are in contacting engagement, and a disengaged position, wherein the rolling element
is removed from contacting engagement with the first cylinder, the adjustment mechanism
being selectively actuable and providing controlled variable displacement of the
rolling element relative to the first cylinder.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the invention, reference
will now be made to the accompanying drawings, showing by way of illustration a
preferred embodiment thereof and in which:
Fig.1 is a schematic side elevation view of an offset printing press
including form rollers adjustment systems according to a preferred embodiment of
the present invention; and
Fig.2 is a schematic side elevation view of an offset printing press
including a cylinder adjustment system according to an alternative embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fig.1, an offset printing press 10 generally comprises
a plate cylinder 12, a blanket cylinder 14 and an impression cylinder 16, all supported
within a common frame structure 18. At least the plate and blanket cylinders 12,14
are adapted to be completely removed from the printing press 10, such that corresponding
replacement cylinders having a different diameter can be re-engaged in the press
in their place. Water and ink are supplied to the plate cylinder 12 by the dampening
unit 22 and the inking unit 20 respectively.
The inking unit 20 generally comprises at least one ink transfer roller
26 receiving ink from an ink supply. The inking unit also comprises ink form rollers
28 in direct contacting engagement with the transfer roller 26 receiving the ink,
and in direct contacting engagement with the plate cylinder 12 to transmit the ink
thereto. The dampening unit 22 generally comprises a dampening form roller 30 in
direct contacting engagement with the plate cylinder 12 and with dampening fluid
transfer rollers 32,33, which transfer the dampening fluid from the dampening supply
34 to the dampening form roller 30. A series of transmission rollers 27 can also
transfer ink from the ink supply to the dampening form roller 30, so that the dampening
form roller 30 applies both water and ink to the plate cylinder 12.
The plate cylinder 12 generally comprises a circumferentially disposed
printing plate on the outer surface thereof, the circumference of the plate cylinder
corresponding to the length of the print repeat produced by the printing plate.
The water and ink fed to the plate cylinder 12 are transferred from the exterior
surface thereof to the blanket cylinder 14, which is in contacting engagement with
the plate cylinder 12. Either sheets or a continuous web are fed between the blanket
cylinder 14 and an impression cylinder 16, which is similarly in contacting engagement
with the blanket cylinder 14. All cylinder rollers are rotatable and in precise
contacting engagement with each adjacent roller along a contact stripe, such that
fluid is transferred from one roller to the next. This contact stripe is precisely
set, to ensure exact and uniform contact pressure along the entire length of the
The present invention concerns an adjustment mechanism for rolling
elements of the printing press. The term rolling element as used herein is defined
to comprise any substantially cylindrical and rotatable press element, including
both rollers, such as ink or dampening form rollers, and cylinders, such as plate,
blanket or impression cylinders.
In a preferred embodiment, illustrated in Fig.1, the adjustment system
90a,b is adapted to be used with form rollers 28,30. Although a single adjustment
system 90a is shown for the ink form roller 28 and a single adjustment system 90b
is shown for the dampening form roller 30, two separate adjustment systems 90a,b
are preferably used for each, one disposed at each end thereof. The adjustment systems
90a,b used with the inking and dampening units 20,22 being similar in geometry and
function, they will be described simultaneously herein. However, it is to be understood
that the adjustment system 90a for the inking form roller 28 and the adjustment
system 90b for the dampening form roller 30 are independently operable from one
Each adjustment system 90a,b generally comprises an integrated multiple
pneumatic actuator assembly having a first pneumatic actuator 92a,b and a second
pneumatic actuator 94a,b. The first pneumatic actuator 92a,b includes an integral
locking mechanism 96a,b. The adjustment system 90a,b also comprises a fixed end
91a,b which is pivotally engaged to the press frame structure 18, and an opposed
translating free end 93a,b which is pivotally engaged to a support or link member
98a,b. The link member 98a,b rotationally supports the form roller 28,30 and rotates
about a fixed pivot 99a,b which is preferably located at the central axis of the
transfer roller 26,32.
The adjustment system 90a,b permits the form roller 28,30 to be "thrown
on" or "thrown off", such that the form roller 28,30 can be selectively engaged
or disengaged from contact with the plate cylinder 12. The adjustment system 90a,b
also allows for the location of the form roller 28,30 to be variable while remaining
in contact with the transfer roller 26,32, which permits the form roller 28,30 to
accommodate displacement of the plate cylinder 12 or an alternate plate cylinder
having a different diameter. The adjustment system 90a,b also permits fine contact
stripe adjustment between the form roller 28,30 and the plate cylinder 12.
In operation, the form roller 28,30 is correctly positioned in contact
with the plate cylinder 12 according to the following. With the second pneumatic
actuator 94a,b fully extended to the end of its stroke, the first pneumatic actuator
92a,b is extended by air pressure and is precisely adjusted until a desired contact
stripe is achieved between the form roller 28,30 and the plate cylinder 12. The
air pressure in the first pneumatic actuator 92a,b of each form roller adjustment
system 90a,b is preferably set by an independent air regulator. The air regulators
can be programmed to different fixed values, corresponding to different plate cylinder
diameters, so that only a fine adjustment may be required by the operator to obtain
a desired contact stripe. Once the desired contact stripe is obtained, the air-actuated
locking mechanism 96a,b is engaged to lock the output rod of the first pneumatic
actuator 92a,b in position, thereby fixing the distance between the translating
free end 93a,b and the fixed end 91a,b of the form roller adjustment system 90a,b.
Accordingly, the air pressure which regulates the first pneumatic actuator 92a,b
can be statically adjusted (ie: when the press is not running) such that a desired
contact stripe width between the form roller 28,30 and the plate cylinder 12 is
achieved, and the brake or locking mechanism 96a,b is then locked to fix the first
pneumatic actuator in position. Thus, during operation of the press, the locking
mechanism 96a,b provides a mechanical stop which correctly positions the form roller
in contacting engagement with the plate cylinder such that a desired contact pressure
therebetween is achieved.
The form roller 28,30 is disengaged from the plate cylinder 12 according
to the following. With the first pneumatic actuator 92a,b locked by the locking
mechanism 96, the second pneumatic actuator 94a,b is actuated to retract, thereby
shortening the overall length of the form roller adjustment system 90a,b. This causes
the link member 98a,b to rotate about the transfer roller 26,32, lifting the form
roller 28,30 out of contacting engagement with the plate cylinder 12. Since the
contact stripe before the disengagement of the form roller 28,30 from the plate
cylinder 12 was determined with the second pneumatic actuator 94a,b fully extended,
and since the first pneumatic actuator 92a,b is locked during that disengagement,
a simple return to full extension of the second pneumatic actuator 94a,b will place
the form roller 28,30 back in contact with the plate cylinder 12 with the same contact
The form roller adjustment system 90a,b alternately includes an integral
locking mechanism in the second pneumatic actuator, so that the desired contact
stripe can be set by the first pneumatic actuator with the second pneumatic actuator
being locked at a chosen length. Retraction of the second pneumatic actuator from
the chosen length thus breaks contact between the form roller and the cylinder,
and extension of the second pneumatic actuator back to the chosen length returns
the set contact stripe between the two rollers. In this case, the second pneumatic
actuator is adapted to retain a memory of the chosen length to be able to automatically
return thereto after retraction.
Referring to Fig.2, an alternative embodiment of the adjustment system
190 of the present invention is illustrated, adapted to be used to adjust the position
of the impression cylinder 16 with respect to blanket cylinders 14 of various sizes,
as well as to "throw-on" or "throw-off" the impression cylinder 16 with respect
to the blanket cylinder 14 when the printing process is to be stopped. This permits
printing to be interrupted, without having to drastically displace the impression
cylinder and blanket cylinder relative to one another, and permits printing to be
easily re-started without having to precisely reset the contact stripe between these
The impression cylinder 16 rotates about its center 144 which is displaceable
along an adjustment arc 142 by the action of first link members 198 which rotate
about a pivot 141. The impression cylinder adjustment system 190 comprises a first
pneumatic actuator 192 having a first translating end 193 which is pivotably engaged
to the impression cylinder first link member 198. A second, opposed end 185 of the
first actuator 192 is pivotably engaged to an eccentric mounting assembly 187 which
is rotatable within the frame structure 18 of the printing press 10. The eccentric
rotating assembly 187 of the first actuator 192 is rotatable by a second actuator
194, which is preferably a smaller pneumatic cylinder. A first translating end 195
of the second actuator 194 is engaged to the eccentric rotating assembly 187 by
a second link member 188. Opposed ends of the second link member 188 are respectively
pivotably connected with the translating end 195 of the second actuator 194 and
the second end 185 of the first actuator which is eccentrically engaged to the rotating
assembly 187. A second end 197 of the second actuator 194 is not displaceable, but
is pivotably connected to the frame structure 18.
Accordingly, and similarly to the first embodiment of the adjustment
system 90a,b previously described, the first actuator 192 is used for impression
adjustment, such that the impression cylinder can be displaced to accommodate the
particular size of blanket and plate cylinders being employed, and to control the
contact pressure between the impression cylinder 16 and the blanket cylinder 14.
By extending or retracting the first translating end 193 of the first actuator 192,
the impression cylinder first link member 198 is thus pivoted such that the impression
cylinder 16 displaced as required. The first actuator 192 preferably has a relatively
large travel, such that plate and blanket cylinder of various sizes can be accommodated.
However, the first actuator is also preferably precisely controlled, such that a
desired contact pressure between the impression cylinder 16 and the blanket cylinder
14 can be set. Once this is set, the first actuator 192 is locked, such that the
relative positions of the first and second ends thereof are fixed.
The second actuator 194 of the impression cylinder adjustment system
190 is used to "throw-on" or "throw-off" the impression cylinder 16, such that printing
can be started or stopped when required. Displacing the translating end 195 of the
second actuator 194 acts to rotate the eccentric rotating assembly 187 within the
frame structure 18, thereby slightly displacing the second end 185 of the locked
first actuator 192 by a slight distance, which accordingly disengages the impression
cylinder 16 from contact with the blanket cylinder 14 by said slight distance. This
slight distance generally corresponds to the eccentricity of the second end 185
of the first actuator 192 relative to the center of rotation of the rotating assembly
187. Thus, the precise location of the impression cylinder and the contact stripe
relative to the blanket cylinder can be preset by the first actuator 192 and then
locked in position, and the second actuator 194 can be activated to easily engage
and disengaged the impression cylinder 16 with the blanket cylinder 14, without
having to reset the position and contact stripe each time. A dial-adjusted mechanical
stop for the piston of the second actuator 194 is preferably also provided, such
that slight displacement of the impression cylinder 16 relative to the blanket cylinder
14 is possible to allow for the particular thickness of the web or sheet substrate
Accordingly, the pneumatically actuated and controlled roller and
cylinder adjustment system 90a,b and 190 permits the elimination of mechanical stoppers,
which have typically been used in the past to locate the form rollers relative to
the plate cylinder and the impression cylinder relative to the blanket cylinder.
The form roller and cylinder adjustment systems 90a,b and 190 provide the ability
to throw on or off the form rollers 28,30 and the impression cylinder 16, and further
permits more accurate adjustment of the contact stripe. It also enables the positioning
of the form rollers 28,30 and impression cylinder 16 as required regardless of the
plate and blanket cylinder size used.
Although pneumatic actuators were described as being the preferred
kind of actuator for the adjustment systems 90a,b and 190, it is understood that
other appropriate kinds of actuating members may be used, such as hydraulic or electric
linear actuators for example. Particularly, in one alternate embodiment of the present
invention, the first pneumatic actuator 192 is alternately a ball screw actuator.
If hydraulic actuators are used, hydraulic fluid pressure would have to be adjusted
to obtain the desired contact stripes.
Also, the adjustment systems as described herein can be used to similarly
adjust other rolling elements in the printing press as required.
The embodiments of the invention described above are intended to be
exemplary. Those skilled in the art will therefore appreciate that the forgoing
description is illustrative only, and that various alternatives and modifications
can be devised without departing from the spirit of the present invention. Accordingly,
the present is intended to embrace all such alternatives, modifications and variances
which fall within the scope of the appended claims.