U.S. patent application number 12/357718 was filed with the patent office on 2010-07-22 for tension control system for deformable nip rollers.
This patent application is currently assigned to GOSS INTERNATIONAL AMERICAS, INC.. Invention is credited to Douglas Joseph Dawley, Daniel Matthew Perdue, Michael Raymond Rancourt.
Application Number | 20100181360 12/357718 |
Document ID | / |
Family ID | 42336135 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100181360 |
Kind Code |
A1 |
Perdue; Daniel Matthew ; et
al. |
July 22, 2010 |
Tension Control System for Deformable Nip Rollers
Abstract
A method and apparatus for controlling web tension in a web
printing press having a plurality of sets of deformable nip
rollers, each set driven by a separate driver, the web passing
sequentially through each set of deformable nip rollers and forming
a web segment therebetween. The driver of a downstream set of
deformable nip rollers is adjusted to set the tension of a first
web segment and a controller adjusts a first characteristic of the
driver of the upstream set of deformable nip rollers to maintain
the tension of a second web segment constant. Alternatively, a
sensor measures a second characteristic of the second web segment
and the controller adjusts the first characteristic of the driver
of the upstream set of deformable nip rollers based on the
measurement from the sensor.
Inventors: |
Perdue; Daniel Matthew;
(Rochester, NH) ; Dawley; Douglas Joseph; (Dover,
NH) ; Rancourt; Michael Raymond; (Merrimack,
NH) |
Correspondence
Address: |
Davidson, Davidson & Kappel, LLC
485 7th Avenue, 14th Floor
New York
NY
10018
US
|
Assignee: |
GOSS INTERNATIONAL AMERICAS,
INC.
Durham
NH
|
Family ID: |
42336135 |
Appl. No.: |
12/357718 |
Filed: |
January 22, 2009 |
Current U.S.
Class: |
226/4 ; 226/195;
226/42 |
Current CPC
Class: |
B65H 2515/32 20130101;
B65H 2557/264 20130101; B65H 2513/10 20130101; B65H 23/1888
20130101; B65H 2404/1122 20130101; B65H 2801/21 20130101; B65H
2557/26 20130101; B65H 2515/314 20130101 |
Class at
Publication: |
226/4 ; 226/195;
226/42 |
International
Class: |
B65H 23/192 20060101
B65H023/192; B65H 23/188 20060101 B65H023/188; B65H 23/18 20060101
B65H023/18 |
Claims
1. A method for controlling web tension in a web printing press
having a plurality of sets of deformable nip rollers, each set of
deformable nip rollers driven by a separate driver, the web passing
sequentially through each set of deformable nip rollers, each
adjacent set of deformable nip rollers forming a web segment
therebetween, comprising the steps of: adjusting a first
characteristic of the driver of a downstream set of deformable nip
rollers to set the tension of a first web segment which is between
the downstream set of deformable nip rollers and an upstream set of
deformable nip rollers; and adjusting a first characteristic of the
driver of the upstream set of deformable nip rollers to maintain a
constant tension on a second web segment which is immediately
preceding the upstream set of deformable nip rollers.
2. The method of claim 1, further comprising the step of: measuring
a second characteristic of the second web segment; and wherein the
step of adjusting a first characteristic of the driver of the
upstream set of deformable nip rollers is based on the measurement
of the second characteristic.
3. The method of claim 2, wherein the first characteristic is the
rotational speed of the driver.
4. The method of claim 2, wherein the second characteristic is the
tension of the second web segment.
5. The method of claim 2, wherein the second characteristic is the
speed of the second web segment.
6. The method of claim 2, wherein the second characteristic is the
amount of torque in the driver of a set of deformable nip rollers
immediately preceding the upstream set of deformable nip
rollers.
7. An apparatus for controlling web tension in a web printing press
having a plurality of sets of deformable nip rollers, each set of
deformable nip rollers driven by a separate driver, the web passing
sequentially through each set of deformable nip rollers, each
adjacent set of deformable nip rollers forming a web segment
therebetween, comprising: means for adjusting a first
characteristic of the driver of a downstream set of deformable nip
rollers to set the tension of a first web segment which is between
the downstream set of deformable nip rollers and an upstream set of
deformable nip rollers; and a controller for adjusting a first
characteristic of the driver of the upstream set of deformable nip
rollers to maintain a constant tension on a second web segment
which is immediately preceding the upstream set of deformable nip
rollers.
8. The apparatus of claim 7, further comprising: a sensor for
measuring a second characteristic of the second web segment; and
wherein the controller adjusts the first characteristic of the
driver of the upstream set of deformable nip rollers based on the
measurement from the sensor.
9. The apparatus of claim 7, wherein the first characteristic is
the rotational speed of the driver.
10. The apparatus of claim 8, wherein the sensor measures the
tension of the second web segment.
11. The apparatus of claim 8, wherein the sensor measures the speed
of the second web segment.
12. The apparatus of claim 8, wherein the sensor measures the
torque in the driver of a set of deformable nip rollers immediately
preceding the upstream set of deformable nip rollers.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to web printing
presses and more particularly to a method and apparatus for
controlling the tension of the web in a printing press including
two or more sets of nip rollers with deformable covers.
[0002] Web printing presses print a continuous web of material,
such as paper. The web travels through nips formed by opposing nip
rollers. The web is moved on its way by driven nip rollers which
are driven by respective nip roller drivers.
[0003] Tension in the web must be maintained within a desired range
in order to achieve smooth operation of the printing press. At the
same time, the velocity of the web, and hence the rotational speed
of nip rollers, must be held relatively constant to achieve good
print product quality. Tension in a web span between two nips can
be adjusted by controlling the speed of the nip roller driver in
the downstream nip.
[0004] Multiple types of nip rollers have been used in conventional
web printing presses. Some nip rollers were formed with a
deformable surface layer such as urethane. Nip rollers with a
deformable surface were found to provide less than ideal operation
because of uneven ribbon-to-ribbon tension in upstream web
spans.
[0005] As a result, nip rollers formed with a deformable surface
such as microcellular foamed urethane were introduced (see, U.S.
Patent Publication No. 2006/0157924 A1 published on Jul. 20, 2006
and incorporated herein by reference). Nip rollers with this type
of deformable surface layer were found to overcome the uneven
ribbon-to-ribbon tension problem of the earlier nip rollers.
However, it was found that any nips with non-rigid covers have an
effective gain that is a function of the tension difference across
the nip roller, so that if the tension of the web downstream from
the nip roller is changed, the tension of the upstream web will
also change requiring an additional tension adjustment.
BRIEF SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide a method
and apparatus which allows for adjustment of the tension of a
downstream span of web without affecting the tension of an upstream
span of web.
[0007] The present invention provides a method for controlling web
tension in a web printing press having a plurality of sets of
deformable nip rollers, each set of deformable nip rollers driven
by a separate driver, the web passing sequentially through each set
of deformable nip rollers, each adjacent set of deformable nip
rollers forming a web segment therebetween. A first characteristic
of the driver of a downstream set of deformable nip rollers is
adjusted to set the tension of a first web segment which is between
the downstream set of deformable nip rollers and an upstream set of
deformable nip rollers. Then, a first characteristic of the driver
of the upstream set of deformable nip rollers is adjusted to
maintain a constant tension on a second web segment which is
immediately preceding the upstream set of deformable nip
rollers.
[0008] In an alternative embodiment, a second characteristic of the
second web segment is measured and the first characteristic of the
driver of the upstream set of deformable nip rollers is adjusted
based on the measurement of the second characteristic.
[0009] The present invention also provides an apparatus for
controlling web tension in a web printing press having a plurality
of sets of deformable nip rollers, each set of deformable nip
rollers driven by a separate driver, the web passing sequentially
through each set of deformable nip rollers, each adjacent set of
deformable nip rollers forming a web segment therebetween. The
apparatus includes a circuit for adjusting a first characteristic
of the driver of a downstream set of deformable nip rollers to set
the tension of a first web segment which is between the downstream
set of deformable nip rollers and an upstream set of deformable nip
rollers. The apparatus also includes a controller for adjusting a
first characteristic of the driver of the upstream set of
deformable nip rollers to maintain a constant tension on a second
web segment which is immediately preceding the upstream set of
deformable nip rollers.
[0010] In an alternative embodiment, the apparatus also includes a
sensor for measuring a second characteristic of the second web
segment and the controller adjusts the first characteristic of the
driver of the upstream set of deformable nip rollers based on the
measurement from the sensor.
[0011] The first characteristic may be the rotational speed of the
driver. The second characteristic may be the tension of the second
web segment, the speed of the second web segment, or the amount of
torque in the driver of a set of deformable nip rollers immediately
preceding the upstream set of deformable nip rollers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above and related objects, features and advantages of
the present invention will be more fully understood by reference to
the following detailed description of the presently preferred,
albeit illustrative, embodiments of the present invention when
taken in conjunction with the accompanying drawings wherein:
[0013] FIG. 1 is a block diagram of an embodiment of the present
invention having closed loop control based on a feedback signal
provided from a tension sensor;
[0014] FIG. 2 is a block diagram of an embodiment of the present
invention having closed loop control based on a feedback signal
provided from a velocity sensor;
[0015] FIG. 3 is a block diagram of an embodiment of the present
invention having closed loop control based on a feedback signal
provided from a torque sensor; and
[0016] FIG. 4 is a block diagram of an alternative embodiment of
the present invention having open-loop control.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0017] FIG. 1 shows a block diagram of an apparatus for setting the
tension of a downstream web without affecting the tension of an
upstream web in a web printing press 10 according to one presently
preferred embodiment of the invention. Web 12 is moved by driven
nips 22, 28 and 34 in the direction indicated by arrow 14. Nips 22,
28 and 34 are formed by nip rollers 20 and 24, 26 and 30, and 32
and 36, respectively. Nip rollers 22 and 24, 26 and 30, and 32 and
36 rotate as indicated by arrows 27 and are formed with a
deformable surface as described above and in more detail in U.S.
Patent Publication No. 2006/0157924 A1.
[0018] Nip rollers 20, 26 and 32 in FIG. 1 are driven by nip roller
drivers 38, 40 and 39, respectively. Nip roller drivers 38, 40 and
39 may be, for example, electric motors, or other type of suitable
drivers. Drive controllers 48, 50 and 49 provide control signals to
nip roller drivers 38, 40 and 39, respectively, to control the
rotational speed of respective nip rollers 20, 26 and 32. The
control signals are provided from controller 70 to the drive
controllers 48, 50 and 49 on respective signal lines 58, 60 and 59,
respectively.
[0019] Upstream web span 16 is formed between nips 22 and 28, while
downstream web span 18 is formed between nips 28 and 34. As one of
ordinary skill in the art will readily recognize, additional nips
may be provided in the printing press 10 within the context of the
present invention, and the principles of this invention apply in
that event as well. A tension sensor 92 directly measures the
tension in upstream web span 16 and provides a corresponding output
signal on line 93 to controller 70. Controller 70 also includes an
input 60 which is used by an operator to set the tension of
downstream web span 18 according to principles of the
invention.
[0020] In the embodiment of FIG. 1, closed loop control is used to
maintain the tension of upstream web span 16 at a constant value
when an operator desires to change the tension of the downstream
web span 18. In particular, when an operator inputs a tension
adjustment for upstream web span 18 to controller 70 via input 80,
controller 70 first calculates an updated value for the control
signal 59 so that drive controller 49 will adjust the rotational
speed of nip roller driver 39 thereby changing the tension of
downstream web span 18 to the desired value. Since the change in
tension of downstream web span 18 would also result a change in the
upstream web span 16 when using deformable nip roller, controller
70 also changes the rotational speed of nip roller driver 40 in a
manner that will maintain the tension of upstream web span 16 at a
constant value. This requires a decrease in the rotational speed of
nip roller driver 40 when the tension of downstream web span 18 is
increased (by increasing the speed of nip roller driver 39), and an
increase in the rotational speed of nip roller driver 40 when the
tension of downstream web span 18 is decreased (by decreasing the
speed of nip roller driver 39). In particular, controller 70
receives a signal on line 93 from tension sensor 92, and compares
the received tension signal with the desired tension level and
adjusts, in a closed loop manner, the control signal 60 so that the
result of the comparison between the received tension signal and
the desired tension level is zero. In this manner, whenever an
operator changes the tension of downstream web 18, the tension of
upstream web 16 will be automatically kept constant by closed loop
control via the feedback signal provided from tension sensor 92. By
maintaining the tension on upstream web span 16 at a constant
level, the change of tension on downstream web span 18 is invisible
to all preceding nips and spans.
[0021] Although the embodiment of FIG. 1 shows a single controller
which separately sets and controls the speed of nip roller drivers
38, 39 and 40, as one of ordinary skill in the art will readily
recognize, each nip roller driver 38, 39 and 40 could be separately
controlled, and that the closed-loop control is only applied in
this illustrative embodiment to control the nip roller driver which
is upstream from the web span having its tension changed. Of
course, as one of ordinary skill in the art will readily recognize,
the techniques of this invention can be applied to allow adjustment
of any span in a printing machine without affecting the tension of
any other span. Thus, in the embodiment of FIG. 1, nip roller
drives 38 and 39 are shown being set by controller 70, but could
alternatively could be set by other means known to one of ordinary
skill in the art. Also, although FIG. 1 shows a controller 70 which
compares the signal from tension sensor 92 to a desired value to
calculate the feedback control signal 60 to apply to drive
controller 50, as one of skill in the art would readily recognize,
this could alternatively be done in the analog domain using a
comparator and other ancillary circuitry, where the comparator
compares an analog signal from the tension sensor 92 to a
predetermined value representing the desired tension setting.
Finally, although FIG. 1 shows drive controllers 48, 49 and 50 as
separate from controller 70, as one of ordinary skill in the art
will understand, the drive controller functions could alternatively
be implemented either within controller 70 or separately within nip
roller drivers 38, 39 and 40.
[0022] FIG. 2 shows a first alternative embodiment of the present
invention which also relies on closed loop control to maintain the
tension of upstream web span 16 at a constant value when the
tension of downstream web span 18 is intentionally changed by the
operator. The only change from the embodiment of FIG. 1 is that a
velocity sensor 95 is provided to monitor the velocity of upstream
web span 16 and provide a corresponding velocity signal 98 to
controller 70 (and tension sensor 92 is omitted). Since the
velocity of the web span is proportional to the tension thereof,
controller 70 compares the measured velocity signal 98 to the
desired velocity value and generates a control signal 60 for the
drive controller 50 connected to nip roller driver 40 which,
because of the closed loop nature of the system, will cause the
difference between the measured velocity signal 98 and the desired
velocity value to quickly become zero, even after the tension on
downstream web span 18 is changed.
[0023] FIG. 3 shows a second alternative embodiment of the present
invention which also relies on closed loop control to maintain the
tension of upstream web span 16 at a constant value when the
tension of downstream web span 18 is intentionally changed by the
operator. The only change from the embodiment of FIG. 1 is that a
torque sensor 90 is provided in nip roller driver 38 to provide a
torque signal 57 to controller 70 (and tension sensor 92 is
omitted). Since the torque of the nip roller driver 38 is
proportional to the tension on upstream web span 16, controller 70
compares the measured torque signal 57 to a toque value that
corresponds to the desired tension on upstream web span 16 and
generates a control signal 60 for the drive controller 50 connected
to nip roller driver 40 which, because of the closed loop nature of
the system, will cause the difference between the measured torque
signal 57 and the desired torque value to quickly become zero, even
after a change on the tension on downstream web span 18.
[0024] FIG. 4 shows a third alternative embodiment of the present
invention which, unlike the other embodiments, does not rely on
closed loop control to maintain the tension of upstream web span 16
and thus does not require any sensor to monitor the tension of
upstream web span 16. Instead, when the operator inputs a tension
change for downstream web span 18, controller 70 automatically
calculates the amount of change necessary for both control signal
59 and control signal 60 based on characteristics stored in memory.
These characteristics can be defined empirically or using
predictive models, as understood by one of ordinary skill in the
art, and, for example, control signal 60 could be a fixed
percentage of control signal 59.
[0025] While the present invention has been particularly shown and
described with reference to the preferred embodiments and various
aspects thereof, it will be appreciated by those of ordinary skill
in the art that various changes and modifications may be made
without departing from the spirit and scope of the invention. It is
intended that the appended claims be interpreted as including the
embodiments described herein, the alternatives mentioned above, and
all equivalents thereto.
* * * * *