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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a cylinder in a printing machine, wherein the
cylinder is driven by an electric individual drive and is arranged so as
to be swivelable with respect to its position by means of a swiveling
device, wherein a rotation transducer or rotation sensor is arranged at
the cylinder for measuring its angular position with respect to the
swiveling device.
2. Description of the Related Art
Recently, there has been an increase in the use of printing machines with
individually driven cylinders such, for example, as an offset printing
machine with both a form cylinder and a blanket cylinder having an
individual electric drive motor. In the offset type of printing machine,
the blanket cylinders must be adjusted or moved toward the printing stock
web at the start of a printing process and adjusted or moved away from it
at the end of the printing process. For this purpose, the blanket
cylinders are arranged together with their electric drive arrangement on a
swiveling device. The swiveling device is an eccentric element or a rocker
type mechanism, for example. The plate cylinder, form cylinder, or other
cylinders, such as a printing cylinder, may also be swivelably arranged.
When an eccentric element is used, the eccentric element is rotatably
mounted in a sidewall of the printing machine. The shaft of the cylinder
is eccentrically mounted on the eccentric element with respect to the
center of rotation of the eccentric element.
A prior art cylinder for a printing mechanism that is driven by an
individual drive, is known from German reference DE 196 24 394 A1. In this
prior art cylinder, a hollow neck or journal of the cylinder is received
eccentrically on a spindle unit that is mounted, in turn, in a side wall
of the printing mechanism. A carrying tube of the spindle unit houses a
stator of an electric motor. A rotation sensor housing located on the
journal is fastened to the carrying tube for regulating the driving of the
motor. For purposes of changing the position of the cylinder relative to
an adjacent cylinder, the spindle unit and, accordingly, the carrying tube
are rotated. During rotation of the spindle unit, the stator of the motor
and the rotation sensor housing are also rotated. Accordingly, the
reference angle to which the rotation sensor references the rotational
angle position of the journal of the cylinder, and therefore the
rotational angle position of the rotor of the motor, is also displaced.
This results in an unwanted rotation of the cylinder being moved in
relation to the adjacent cylinder cooperating with it.
It has been shown in practice that even small displacement paths between
the "print on" and "print off" positions of the cylinder lead to large
rotations of the above described eccentric mechanism . For example,
displacement paths of 0.1 mm already require 10-degree rotation of the
eccentric mechanism. This problem also occurs when a rocker is used as a
swiveling device for the cylinder. However, the angular errors occurring
with rockers, depending on their length, are smaller than with eccentric
mechanisms.
After a swiveling movement is carried out, the intended angular position of
the cylinder is displaced not only in relation to the adjacent cylinder,
but also in relation to the printing stock web. The movement in relation
to the printing stock web occurs because, the blanket cylinder, due to the
position regulation, also executes a further movement in addition to its
movement corresponding to the web speed of the printing stock when the
eccentric mechanism is rotated. The further movement comprises a rotating
movement and--corresponding to the offset of the center of rotation of the
cylinder from the center of the eccentric--a transverse movement. This
movement can cause the printing stock web to tear during the
print-on/print-off setting process because the blanket cylinder not only
rolls along the surface of the printing stock web, but also causes sliding
friction on its surface due to the translational movement. In this
respect, the blanket cylinder draws the printing stock web toward it.
SUMMARY OF THE INVENTION
It is the object of the invention to correct the rotational movement of the
cylinder that is corrupted by the swiveling movement of the eccentric
mechanism or rocker type device and to prevent tearing of the printing
stock web.
The object of the invention is met according to the invention with a
swivelable cylinder assembly which includes a swivelable cylinder for a
printing machine that is mounted on a swiveling device. The angular
position of the cylinder with respect to the swiveling device and the
swivel movement of the-swiveling device with respect to the printing
machine in which it is located are measured by measuring devices. A
reference rotational angle is obtained from an angular value of the web
speed of the printing machine and the angle value of the swivel movement
of the swiveling device. The reference rotational angle of the cylinder is
compared to the measured rotational angle of the cylinder and a control
signal is generated in response to the comparison for controlling the
rotational velocity of the cylinder.
The various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming a part
of the disclosure. For a better understanding of the invention, its
operating advantages, and specific objects attained by its use, reference
should be had to the drawing and descriptive matter in which there are
illustrated and described preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described more fully in the following with reference
to the drawings. In the drawings:
FIG. 1 is a sectional view of an eccentrically mounted blanket cylinder
according to the present invention;
FIG. 2a shows a form cylinder and a blanket cylinder configuration with a
common drive according to the present invention;
FIG. 2b is a side view of a printing mechanism with the form cylinder and
blanket cylinder arrangement of FIG. 2a;
FIG. 3 is a side view of a satellite printing mechanism with individually
driven cylinders according to the present invention; and
FIG. 4 is a block diagram showing a control circuit for angle correction of
a cylinder of the present invention with respect to the fixed parts of the
printing machine.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
Referring initially to FIG. 1, a cylinder 1 such, for example, as a form
cylinder or a blanket cylinder is rotatably mounted in a carrying tube 6
by its shaft journal 2 and a shaft 3 by roller bearings 4, 5. The carrying
tube 6 is fixedly connected with an eccentric element 7 on a side remote
from the cylinder 1 and is formed eccentrically, with respect to the shaft
3. The eccentric element 7 is rotatably mounted in a side wall 9 via
needle bearings 8 or any other suitable bearings. A connection tube 10 is
flange mounted on the shaft 3 and is rotatably mounted via ball bearings
11 in the eccentric element 7. In the region between the ball bearings 11
and the end side of the shaft 3, the connection tube 10 is surrounded by a
rotor 12 of an electric motor 14. A stator winding 13 of the electric
motor is fastened to the inner side of the carrying tube 6. The rotor 12
and the stator 13 are separated from one another by an air gap as in any
electric motor. The electric motor 14 rotates the connection tube 10,
shaft 3, and cylinder 1 relative to the carrying tube 6 and the eccentric
element 7. A rotation sensor 15 is mounted on the eccentric element 7 on
the side of the side wall 9 remote from the cylinder 1 on a projection of
the eccentric 7, but could be located anywhere along the shaft 3. The
rotation sensor 15 measures the rotational angle of the cylinder 1 at the
connection tube 10 relative to the eccentric element 7 with respect to a
fixedly predetermined zero position. The rotation sensor 15 transmits an
output signal in response to the speed of the shaft 3 to a regulating
circuit (see FIG. 4) continuously or in predetermined time intervals.
Another rotation sensor 16 which measures the angular position occupied by
the eccentric element 7 relative to the side wall 9 is rigidly attached to
the side wall 9. The eccentric element 7 is moved together with the
carrying tube 6, for example, by means of a hydraulic actuating motor 17.
The actuating motor 17 has a hydraulic cylinder 18 whose piston rod 19 is
connected with the carrying tube 6 via a pivot joint 20. The hydraulic
cylinder 18 is articulated at a fixed component part 21 of the printing
machine such, for example, as the side wall 9.
The cylinder 1 may be mounted by one side in the side wall 9, or may be
mounted by both side in opposing side walls of the printing machine. In
the latter case, it is also mounted in the second side wall via a second
eccentric element (not shown). When the cylinder 1 is mounted by only one
side wall 9, a supporting wall 22 may be provided in which the carrying
tube 6 is mounted via a bearing, for example, a needle bearing 23. When
eccentric elements 7 are provided on both sides of the cylinder 1, angle
measuring devices such as the rotation sensors 16 may also be arranged on
both sides. Both of these angle measurement devices supply the angle
values measured by them to the regulating circuit (FIG. 4). The measured
angle values can be weighted, for example, in a ratio of 1:1.
Instead of the rotation sensor 16, other means for determining the position
of the eccentric element 7 may also be used. For example, an encoder may
be to determine the angular position of the eccentric element with respect
to the side wall 9. A translational movement of the eccentric element 7
may also be measured, especially when this translational movement is
approximately proportional to the rotational angle of the eccentric
element 7 in case of small rotational angles. Further, a horizontal and
vertical component of the translational movement may also be determined
when two position sensors are provided in a corresponding manner for
measuring the translational movements. The values of the translational
movement are supplied to a computing circuit which determines a respective
angle value for the rotational movement of the eccentric element 7.
Instead of the bearing of the cylinder 1 being received in the eccentric
element 7, the shaft journal 2 and the electric motor 14 may be received
by a rocker swivelably fastened in the side wall 9 and in the opposite
side wall. When a rocker is used, a smaller angular error occurs because
of the longer lever in comparison with the eccentric element 7; it is
therefore possible in this case to approximate the angular movement by a
translational movement.
In another embodiment of the invention shown in FIGS. 2a and 2b, both sides
of a blanket cylinder 24 are mounted at both sides via eccentric elements
25, 26 in side walls 27, 28 of a printing mechanism tower 29. The blanket
cylinder 24 is driven directly by an electric motor 30 mounted on the
eccentric element 26. An angle encoder 31 arranged at the end side of the
electric motor 30 measures the rotational angle of a shaft journal 32 of
the blanket cylinder 24 relative to the eccentric element 26. The
rotational movement of the blanket cylinder 24 is transmitted by a meshed
connection of toothed wheels 33 and 34 to drive a form cylinder 35. An
angle encoder 37 arranged on the shaft journal 36 of the form cylinder 35
directly measures the angular position of the form cylinder 35 and also
accordingly indirectly measures the angular position of the eccentric
element 26 with respect to the rigid side wall 28. The blanket cylinder 24
and the form cylinder 35 cooperate with other blanket cylinders 38 to 44
and form cylinders 45 to 51 to ink both sides of a printing stock web 52
in the printing mechanism tower 29 with four colors on each side. Only the
blanket cylinders 24, 38 to 44 are driven by motors. Also, when the
eccentric element is adjusted, the drive connection is maintained because
the adjustment of the eccentric moves only within the tooth flank
clearance of the respective toothed wheels 33, 34.
In another embodiment example of the invention shown in FIG. 3, a printing
stock web 53 in a satellite printing mechanism 54 is imprinted on both
sides by two colors on each side. The satellite printing mechanism 54
comprises four pairs of blanket cylinders 55 to 58 and form cylinders 59
to 62 associated respectively therewith. Also, in this embodiment form,
the blanket cylinders 55 to 58 are mounted on eccentrics or rockers (not
shown here). The blanket cylinders 55 to 58 are driven directly by
electric motors. The form cylinders 59 to 62 and printing cylinders 63, 64
are driven via toothed wheel connections in the same way as is shown in
FIG. 2a by the electric motors arranged on the shaft journals of the
blanket cylinders 55 to 58. Rotation sensors 65 to 68 are fixedly
connected at the side wall of the satellite printing mechanism 54 for
measuring the angular position of the eccentrics of the blanket cylinders
55 to 58.
To regulate the movement of cylinder 1 of FIG. 1, blanket cylinders 24, 38
to 44 of FIG. 2a, and blanket cylinders 55 to 58 of FIG. 3 during an
adjustment of the eccentric element so that the cylinders do not slide on
the surface of adjacent cylinders, but rather roll continuously on the
latter and, in particular, also do not pull on the printing stock web 52,
53 by sliding such that the printing stock web 52, 53 could tear, the
movement of the eccentric element is regulated such that the rotation of
the eccentric is accompanied by a rolling movement of the cylinder 1 or
blanket cylinders 24, 38 to 44, 55 to 58.
Referring now to FIG. 4, a block diagram of a control circuit 100 is shown
for determining a rolling movement of a cylinder to accompany the rotation
of the eccentric element to prevent the potential for tearing the web. A
speedometer 110 determines a web speed of the printing stock web
V.sub.web. The web speed of the printing stock web V.sub.web is known
under normal circumstances by a preset on the control station of the
printing machine and may be input to the speedometer 110 as a constant.
However, independent from this known value, the actual web speed may also
be determined by a measuring device in the immediate vicinity of the
printing mechanism in which the movement of the eccentric element takes
place. The speedometer 110 transmits the known or determined web speed
V.sub.web to a divider 115 which is used to derive a reference angular
speed .omega..sub.cyl. which is the quotient of the web speed V.sub.web
and the radius r.sub.cyl. of a cylinder Z. By integrating over time in
integrator 120, the reference angular speed .omega..sub.cyl. gives the
reference rotational angle .phi..sub.cyl. occupied by the cylinder Z with
respect to the machine frame, the printing stock web, for example,
printing stock web 52 or 53, and with respect to the other cylinders, for
example, the form cylinders 35, 45 to 51 and 59 to 62 or the printing
cylinders 63, 64. The reference rotational angle .phi..sub.cyl. is
transmitted to a first summing point S1 at which the difference in
relation to an angle .phi..sub.ecc. of the eccentric element E with
respect to the machine frame flows into a second summing circuit S2. The
angle .phi..sub.ecc. is either directly the angle measured by the second
rotation sensor, for example, the angle encoder 37, or an angle measured
by one of the rotation sensors 65 to 68 relative to the side wall, or an
angle derived therefrom. For example, the angle .phi..sub.ecc. may also be
obtained from the transverse relative movement of the cylinder axle of the
eccentrically mounted cylinder, for example, by linearization of the
functional relationship between the transverse offset and the associated
angle .phi..sub.ecc.. The angle reference value .phi..sub.ref. obtained
from the angles .phi..sub.cyl. and .phi..sub.ecc. is transmitted to a
bearing or position regulator 125 in which a reference speed
.omega..sub.ref is obtained from the reference angle value .phi..sub.ref.
This reference speed .omega..sub.ref is transmitted through a third
summing circuit S3 to a speed regulator 130. The speed regulator 130
obtains, as regulating variable, a reference current I.sub.ref or a
reference torque for an electric motor M which corresponds, for example,
to electric motor 30 and which drives the cylinder Z from the reference
speed .omega..sub.ref. The rotation sensor or angle encoder 140 of
cylinder Z which corresponds to rotation sensor 15 supplies the actual
rotational angle .phi..sub.1cyl. of the cylinder Z with respect to the
eccentric element E, for example, eccentric element 7, or with respect to
the motor housing which is connected, for example, with the carrying arm
6. The actual rotational angle .phi..sub.1cyl. is transmitted to the input
side of the speed regulator 130, for example, via a differential element
145. The differential element 145 obtains the actual angular speed
.omega..sub.1cyl. from the actual rotational angle .phi..sub.1cyl.. The
actual angular speed .omega..sub.1cyl. may also be obtained by subtraction
from different actual rotational angle values at different times and
dividing by the difference in times. The actual rotational angle
.phi..sub.1cyl. is also transmitted to the input of the position regulator
125 the second summing point S2. Further, in accordance with an embodiment
form of the invention, the actual rotational angle .phi..sub.1cyl. may
also be utilized to obtain a suitable function from the angle
.phi..sub.ecc. of the eccentric element E which is supplied to the summing
point S1. The adjusting movement of the eccentric element E is accordingly
either directly detected as an angular adjustment .phi..sub.ecc..
auxiliary variable, for example, the setting of a lever acting on the
eccentric element E, is transformed into a value corresponding to the
angle .phi..sub.ecc..
Further, it is also possible that the exact movement sequence of the
eccentric element movement is already known beforehand, so that a direct
or indirect detection of the angle .phi..sub.ecc. of the eccentric element
may be dispensed with and the respective angle values from the starting
time or ending time of the eccentric movement are stored already in an
electronic storage and used for regulating the angular position of the
cylinder. The transverse movement executed by the cylinder during
adjustment of the eccentric is likewise known by way of the movement
sequence of the eccentric and can be compensated by the drive control of
the cylinder. Damaging relative movements between the cylinder and the
printing stock or with other adjacent cylinders can accordingly be
prevented. For example, the translational component of the adjustment of
the eccentric can be calculated from the angle .phi..sub.ecc. of the
eccentric E in a computing circuit and supplied separately to the summing
point S1.
However, it is also possible to measure exclusively the translational
movement of the eccentric E with an appropriate sensor and to obtain
therefrom the respective angle value .phi..sub.ecc. in a computing
circuit, for example, from an algebraic rule. A filter can be installed to
smooth the calculated angle values .phi..sub.ecc.. The angle values for
.phi..sub.ecc. may also already be stored in a table so that an angle
value .phi..sub.ecc. corresponding to the path traveled during a
determined translational movement of the eccentric E is supplied from the
table to the regulating circuit of FIG. 4.
The adjusting movement between the cylinder and the side wall may be
detected indirectly by the rotation sensor of an eccentric element, as was
described above, or may be detected directly via a rotation sensor
arranged at the cylinder shaft which measures the movement of the cylinder
relative to the side wall.
The present invention provides a cylinder 24 having an adjustable position.
The cylinder 24 may be adjusted away from a printing stock web or an
adjacent cylinder 35 and the change in position caused by a movement of
the eccentric is compensated by an additional rotating movement superposed
on the rotating movement of the cylinder 24 such that the outer surface of
the cylinder 24 has no velocity relative to the adjacent cylinder 35 or to
the printing stock web. Compensation is performed by a regulating circuit
to which is supplied the actual rotational angle .phi..sub.1cyl. of the
cylinder 24 with respect to the eccentric 26 and the actual rotational
angle .phi..sub.ecc. of the eccentric 26 with respect to the side wall 28
or an angular function derived therefrom.
Instead of being driven directly as was described above, the blanket
cylinder 24, 38, 39, 40, 41, 42, 43, 44, 55, 56, 57, 58 may be driven
indirectly by the form cylinder 35, 45, 46, 47, 48, 49, 50 or 51 which is
driven directly.
The invention is not limited by the embodiments described above which are
presented as examples only but can be modified in various ways within the
scope of protection defined by the appended patent claims.
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