Apparatus and method for cleaning a roller

A roller cleaning system includes a pad disposable against a roller for cleaning the surface of the roller when the roller is rotated. The pad is supported in a frame which may be stationary or mounted for translation so that the pad may traverse a length of the roller while cleaning the roller surface. The pad may be further provided with an actuator for urging a portion of the pad against the roller at an additional force. The frame has a first portion disposed at a fixed distance from the surface of the roller and a second portion carrying the cleaning pad, the second portion being pivotable from the first portion about an axis parallel to the axis of the roller. Means are included for measuring torque exerted on the pivot, which torque is indicative of frictional drag on the cleaning pad. In a preferred embodiment, a piezo-electric strain gauge disposed between the frame portions is connected in a feedback loop with a controller and the pad actuator. As the roller turns against the pad, the resulting drag exerts a torque about the frame pivot, which produces an output signal to the controller. Under steady-state conditions, the output signal is constant and the controller takes no action. If the frictional drag begins to increase, the torque also begins to increase, and the controller then reduces the force exerted by the actuator against the pad to reduce the frictional drag.

The present invention relates to systems (apparatus and methods) for 
removing contaminants from process rollers and more particularly to 
apparatus and methods for washing and scrubbing contaminants from process 
rollers. This invention provides apparatus and methods for removing 
accumulated particles from contact cleaning rollers used to clean such 
particles from substrates, which substrates may be other process rollers 
or sheet or web stock being conveyed as by process rollers. 
A common problem with process rollers is that they eventually accumulate 
contaminants on their surfaces, especially foreign particles which can 
cause unwanted physical and/or chemical anomalies in the substrates being 
conveyed by such rollers and in coatings upon the substrates. All such 
process rollers, therefore, require cleaning of their surfaces from time 
to time. The term "process roller" may include not only conventional metal 
or polymer rollers used to convey web or sheet stock along a path but also 
specialty rollers such as, for example, contact cleaning rollers (also 
referred to herein as "CCR's") used either to clean the web or sheet 
substrate directly or to clean other conveyance rollers along the web 
path. 
The problem of retained contaminants is particularly acute for CCR's which 
are intended by their very nature to become clogged on their surfaces as 
they remove particles from the surfaces of substrates over which they have 
been rolled and which must be renewed by cleaning in order to restore 
their particle-removing effectiveness. 
In the process roller cleaning apparatus of the allowed parent application, 
a cleaning pad is brought into rubbing contact with the contaminated 
surface of a roller to be cleaned. The roller is rotationally driven past 
the pad, which may be dry or, typically, moistened with a suitable liquid 
to aid in dislodging or dissolving the contaminants on the roller surface. 
Such rubbing or scrubbing of the cleaning pad against the roller causes 
contaminants to be transferred from the roller to the cleaning pad. The 
pad may consist of a simple resilient material such as a sponge, or, more 
typically, a cleaning web of cloth in contact with the roller surface, 
supported by a backing element such as a sponge to urge the cleaning web 
against the roller at a first force. The cleaning web may be 
intermittently or continuously dispensed from an unsoiled source to 
present clean web to the roller, the soiled web being accumulated out of 
contact with the roller. The pad including the web may be moved axially of 
the roller during cleaning so that a pad substantially narrower than the 
roller can progressively clean the entire roller surface, as disclosed in 
our above referenced '281 patent. 
Further disclosed in the allowed parent application, an actuator is 
disposed for actuation in the direction of the roller against a portion of 
the rear surface of the cleaning pad, preferably a central portion, at a 
second force which is in addition to the first force being applied over 
the entire pad. This localized higher force is extremely effective in 
accelerating the rate of cleaning of the roller by the pad. In wet 
cleaning installations, the cleaning fluid acts not only as a cleaning 
agent but also as a lubricant to reduce the frictional drag of the pad 
against the roller. 
Typically, the cleaning fluid is supplied continuously to the pad during 
cleaning. If the supply fails, dangerously high frictional forces can 
build up rapidly, which can result in permanent damage to the roller 
surface. Contact cleaning rollers, having typically a relatively soft 
surface, are especially vulnerable to damage from such forces. 
In the allowed parent application, a control system is disclosed wherein 
the frictional drag during cleaning is sensed as a component of the load 
on the motor driving the roller. If the cleaning area becomes dry, 
frictional resistance begins to increase. As the motor load also begins to 
increase, the controller automatically begins to reduce the second force 
on the cleaning pad to reduce frictional resistance of the pad against the 
roller. If the motor load continues to increase, the controller will 
continue to decrease the second force. Preferably an alarm limit is 
established within or at the limit of controller action, at which point 
the system presents an alarm condition and activates an alarm. Preferably, 
cleaning of the roller is automatically terminated at the alarm, either by 
separating the roller from the cleaning pad or by shutting down the roller 
drive, or by both. 
In an alternative embodiment, the drive motor may be such that increased 
frictional load causes a decrease in motor speed, for example, an air 
motor or an hydraulic motor. In such case, the control scheme can utilize 
the rotational speed of the motor as the set point for the controller. The 
action of the controller and the alarm is the same as above. 
The disclosed system functions well for cleaning relatively small, 
light-weight rollers which typically are driven by fractional-horsepower 
motors, wherein a small change in load is easily sensed. However, many 
industrial processes utilize very large and heavy rollers which may be 
driven by large, multiple-horsepower motors wherein small but significant 
load changes may not be easily recognizable. Thus, another approach is 
needed for sensing the onset of an unacceptably high friction condition. 
It is a principal object of the invention to provide an improved method and 
apparatus for the feedback control of frictional drag between a cleaning 
pad and a rotating roller being cleaned by the pad. 
It is a further object of the invention to provide an improved method and 
apparatus for sensing changes in frictional drag between a cleaning pad 
and a roller being cleaning by the pad. 
It is a still further object of the invention to provide an improved method 
and apparatus for controlling the frictional drag between a cleaning pad 
and a roller being cleaned by the pad which is useful for rollers of any 
length, diameter, and weight. 
It is a still further object of the invention to provide improved apparatus 
for controlling the frictional drag between a cleaning pad and a roller 
being cleaned by the pad, which apparatus is relatively inexpensive to 
install and maintain. 
Briefly described, in a roller cleaning system embodying the invention, a 
pad is disposed against a roller at a first force as by a device which 
provides static or dynamic pressure, referred to as a first actuator, for 
cleaning the roller when the roller is rotated. The pad is supported in a 
frame which may be stationary or mounted for translation, for example, on 
rails, parallel to the axis of the roller so that the pad may traverse a 
programmed axial length of the roller while cleaning the roller surface. 
The pad is further provided with a separate actuator for urging a portion 
of the pad against the roller at a second and additional force. Frictional 
control is provided in that the frame has a first portion disposable at a 
programmable first distance from the surface of the roller, and a second 
portion carrying the cleaning pad, the second portion being pivotable from 
the first portion about an axis parallel to the axis of the roller. Means 
are included for measuring torque exerted on the pivot, which torque is 
the net resultant of gravitational force on the second frame portion and 
frictional drag on the cleaning pad. 
In a preferred embodiment, the range of pivoting is limited by first and 
second mating stops on the first and second frame portions, respectively. 
Disposed between the stops is means for measuring the force exerted on the 
stops, for example, a piezo-electric strain gauge, connected in a feedback 
loop with a controller and the pad actuator. As the roller turns against 
the pad, the resulting drag exerts a torque about the frame pivot and 
generates a force on the measuring means, which produces an output signal 
to the controller. Under steady-state conditions, the output signal is 
constant and the controller takes no action. If the frictional drag begins 
to increase, the force exerted against the measuring means also increases, 
and the controller then reduces the force exerted by the actuator against 
the pad as in the parent art. 
The controller of the subject invention may also be programmable to respond 
to a variable set point, so that the first and/or second forces may be 
varied with time to permit differing portions of the roller to be cleaned 
at differing amounts of force on the cleaning pad. For example, the outer 
portions of the roller surface near the ends may benefit from increased 
first and/or second cleaning forces. Additionally, vigorous cleaning of 
the roller surface may not be needed on every axial cycle of the 
traversing cleaning system along the length of the roller, and pad life 
may be extended by programming the controller to exert a higher first 
and/or second force on, for example, every fifth or tenth such cycle. 
The subject invention is also useful in simple cleaning installations not 
equipped with an actuator for providing an additional, localized force to 
the pad. The apparatus and control loop may include instead other means 
for reducing the frictional drag such as, for example, slowing the 
rotational speed of the roller or increasing the spacing between the 
roller and the cleaning apparatus.

Referring to FIG. 1, there is shown a roller cleaning system 10 in 
accordance with the prior art, comprising a roller cleaning assembly 12 
and controller in a control loop 14. System 10 is in position to clean a 
process roller 16, which may be a conventional conveyance roller or a 
specialty roller such as, for example, a contact cleaning roller, a 
coating roller, a fountain roller, a gravure roller, or the like. 
In assembly 12, a frame 18 is mounted at a fixed distance from roller 16 
for translation axially of roller 16 along rail guide 20. Frame 18 
supports roller cleaning apparatus 22 including a cleaning pad 24 
comprising a backing element 25 and a cleaning web 26. Other cleaning pad 
configurations may also be used, for example, a resilient material active 
directly upon the surface of roller 16 without resort to an additional web 
26. In the preferred embodiment, backing element 25 may be any suitable 
resilient material, preferably a sponge or sponge cartridge, and operates 
to urge cleaning web 26 against roller 16 at a substantially uniform 
pressure over the entire surface of element 25. Preferably, cleaning web 
26 is continuously wetted at the contact point with roller 16 by a 
cleaning fluid dispensed from a reservoir (not shown) included in assembly 
12. Cleaning web 26 is dispensed intermittently or continuously from a 
feed roll 28 of material and is accumulated on a take-up roller 30 when 
soiled. 
Roller 16 is driven in rubbing contact past cleaning pad 24 by a friction 
drive wheel 32. Preferably, roller 12 is driven at a fixed rotational 
speed experimentally predetermined to yield adequate cleaning of roller 16 
in a desired length of time. Assembly 12 may be moved axially of roller 16 
during cleaning so that a relatively narrow cleaning web can clean a 
relatively long roller. 
An actuator 34 is disposed between the back side of backing element 25 and 
frame 18 and is preferably a pneumatic cylinder supplied with pressurized 
air from a high-pressure source 36 through a reducing valve 38 and a 
supply line 40. Actuator 34 engages only a portion of the back side of 
element 25, thereby creating a second localized force against pad 24 which 
is additive over that portion of the element to the first force applied 
over the entire pad. 
The controller in the control loop 14 is an electronic controller 42 which 
senses a signal from a conventional electronic drive package 44 which 
controls a motor driving drive wheel 32. The current 46 drawn by the drive 
motor is indicative of the magnitude of frictional resistance between 
roller 16 and cleaning web 26 and is preferably held constant during 
roller cleaning. Controller 42 outputs through a conventional I/P 
transformer 48 to adjust the opening of valve 38 to increase or decrease 
the second force exerted locally on the cleaning pad and thereby to 
maintain as constant the amperage drawn by the drive motor. An alarm 49 
can also be activated by the controller. 
The system described thus far is the subject of the allowed parent 
application. We have found that this system works well for cleaning 
lightweight, small-diameter process rollers driven by relatively small 
motors, for example, a roller having a diameter of 4 inches, a length of 
60 inches, and a weight of 50 pounds, being driven by a 1/4 horsepower 
motor. Small absolute changes in motor load associated with increased 
friction at the cleaning point can represent large percentage changes and 
can be readily sensed and controlled. 
However, for much larger rollers, this patented system can be sub-optimal, 
for example, a roller having a diameter of 12 inches, a length of 200 
inches, and a weight of 1200 pounds, being driven by a 3 horsepower motor. 
Small absolute changes in motor load can represent only small percentage 
changes which may not be readily detectible. In addition, because of much 
higher inertial force associated with a massive rotating roller, roller 
damage from cleaning pad friction may begin at an even lower signal level 
than with a smaller roller. 
We have found the following novel control system, which does not depend on 
sensing motor load, to be suitable for use with rollers of any size and 
weight. Instead of sensing parametric changes on the roller side of the 
frictional pair, this system senses changes on the cleaning apparatus 
side, specifically the torque imposed on the cleaning assembly by contact 
with the rotating roller. 
Referring to FIG. 2, a roller cleaning system 50 in accordance with the 
invention includes a roller cleaning assembly 52 and controller in a 
control loop 54. Assembly 52 includes a first frame 56 disposed for 
translation along rail guide 20 parallel to the axis of process roller 16 
and at a predetermined, preferably variable, distance therefrom. A 
pivotable frame assembly 55 includes a second frame 58 pivotably mounted 
on first frame 56 via matching bores in both frames and a pivot pin 60 
therein. The axis of the bores and pin is substantially parallel to the 
axis of roller 16, permitting second frame 58 to swing through an arc 
orthogonal to the axis of roller 16. Pivotable frame assembly 55 also 
includes a third frame 62 adjustably mounted on second frame 58 via an 
alignment channel 64 and upper and lower adjustment screws 66 and 68, 
respectively. Third frame 62 supports a feed roll 28, a take-up roll 30 
for a cloth cleaning web 26, a cleaning pad backing element 24 for urging 
web 26 against the surface of roller 16 at a first force, and an actuator 
34. Screws 66,68 may provide static pressure adjustment, but the pressure 
may be varied dynamically by one or more controllable actuators, such as 
pneumatic actuators whereby the first force over the entire surface of the 
cleaning pad may be varied by varying the supply of pressurized air 
thereto, preferably by a programmable controller. 
As in the parent application, actuator 34 is disposed against a central 
portion of the backing element 24 to create a locally higher and variable 
second force thereupon. The magnitude of the first force may be varied by 
adjustment of the adjustment screws 66,68 to move third frame 62 closer to 
or farther from process roller 16. Preferably, backing element 24 includes 
a resilient mesh layer 27 on its back side and comprises a sponge 
cartridge which may be readily replaced in the cleaning assembly. 
The actuators 34, 66 & 68 may be hydraulic, pneumatic, electromechanical or 
electromagnetic devices. 
First frame 56 includes an extension 70 opposite a lower portion 72 of 
second frame 58. In the space therebetween is mounted a strain gauge 74 
having a base 76 supported by extension 70 and a load button 78 in contact 
with second frame 58. Strain gauge 74 is thus positioned to detect torque, 
and changes in torque, of second and third frames 58,62 about pivot pin 60 
relative to first frame 56. A suitable strain gauge, for example, is an 
OMEGADYNE Model LCGD-100 load cell, available from Omegadyne, Inc., 
Sunbury, Ohio USA. 
A first reservoir 80 holds a supply of cleaning fluid 82, and a second 
reservoir 84 holds a supply of cleaning additive 86, for example, a 
detergent, which may be supplied individually or together via tubing 88 to 
cleaning pad 24. The cleaning fluid may be supplied to the pad itself or 
directly into the nip between the cleaning web 26 and roller 16. 
The control loop 54 controller 42, preferably a programmable controller, 
taking its input signal from strain gauge 74, and an alarm 49, I/P 
transformer 48, and reducing valve 38 as described hereinabove. The 
controller may include an A/D converter which provides a digital 
representation of the input signal and an electronic computer 
(microprocessor based system). 
In operation, roller 16 is rotated at a fixed speed in either the A or B 
direction. A flow of cleaning fluid 82 is established to backing element 
25 and cleaning web 26. Third frame 62 is advanced toward roller 16 to 
urge the cleaning pad against the roller at a desired first cleaning 
force. Actuator 34 is engaged by compressed air against a portion of the 
back side of backing element 25 creating a desired magnitude of second 
force thereupon. The air pressure supplied to the actuator is the 
controller output variable. The signal from strain gauge 74 is the 
controller set point. Under operating conditions, the controller will vary 
the air output to the actuator to maintain a constant signal from the 
strain gauge, thereby preventing build-up of frictional drag and avoiding 
potential damage to the surface of the roller during cleaning. If 
frictional resistance continues to tend to increase, the controller will 
continue to reduce air output to the actuator until the limit of control 
is reached, at which time the controller may activate an alarm or may 
terminate further cleaning in known or obvious fashion, or both. 
The force on the strain gauge is an arithmetic combination of the 
gravitational force on the second and third frames and the frictional drag 
between the cleaning pad and the roller. If the roller is rotating in 
direction B, toward the strain gauge, increasing drag causes an increasing 
signal from the strain gauge. If rotation is in direction A, away from the 
strain gauge, increasing drag causes a decreasing signal. The controller 
must be provided with the proper response algorithm. 
Other means of measuring torque on second and third frames 58,62 about 
pivot pin 60 may be selected and are within the scope of the invention. 
For example, a rotary strain gauge may be substituted for pivot pin 60, 
wherein the strain gauge is fixed to both first frame 56 and second frame 
58 and torque is sensed in the pivot pin itself. 
The controller of the subject invention may also be programmable to respond 
to a variable set point which biases the strain gauge output, so that the 
first and/or second forces may be varied with time. Since the cleaning 
apparatus may be mounted to traverse axially along the roller during a 
cleaning cycle, this feature permits differing portions of the roller to 
be cleaned at differing amounts of force on the cleaning pad without 
triggering an out-of-control response by the controller. Thus, for 
example, the outer portions of the roller surface near the ends, which 
typically bear a preponderance of the particulate contamination on a 
contact cleaning roller, may benefit from increased first and/or second 
cleaning forces. Additionally, vigorous cleaning of the roller surface may 
not be needed on every axial cycle of the traversing cleaning system along 
the length of the roller, and pad life may be extended by programming the 
controller to exert a higher first and/or second force on, for example, 
every fifth or tenth such cycle. 
From the foregoing description it will be apparent that there has been 
provided an improved method and apparatus for cleaning a roller, wherein a 
pivotable cleaning assembly includes a strain gauge responsive to the 
frictional resistance of a cleaning pad against the roller and a 
controller responsive to the strain gauge to vary the force directed 
against a portion of the back side of the cleaning pad and thereby to 
maintain a constant frictional resistance. Variations and modifications of 
the herein described roller cleaning method and apparatus, in accordance 
with the invention, will undoubtedly suggest themselves to those skilled 
in this art. Accordingly, the foregoing description should be taken as 
illustrative and not in a limiting sense.