Patent Application
20180346274
The present subject matter relates to a system and method for controlling position.
In some production processes, a web is transported past one or more devices that undertake manufacturing step(s). In other processes, the web itself is modified in some manner, such as by applying inks and/or coatings thereto.
In any such production processes, it is important that the web be precisely registered with the equipment undertaking the manufacturing step(s) so that the step(s) are undertaken correctly. Accuracy in the process direction is accomplished by accurate installation of production line components, and accurate control of web speed. Lateral positioning transverse to the process direction is accomplished by, among other things, accurately controlling the lateral web position. Most web steering or guiding systems that control lateral web position are intended for positioning a web as it enters a process from a source roll.
A known steering roll assembly sold by AccuWeb, Inc. of Madison, Wis., utilizes steering rolls mounted within a movable frame. A linear bearing system and linear actuator allow motion of the movable frame accomplishing the desired web steering function. The linear actuator is controlled by a control system that responds to measurements provided by a web edge sensor. Pivoting of the movable frame relative to an adjustable theoretical pivot point maintains a desired lateral web position. It has been found, however, that this steering roll assembly is not suitable for use in certain environments where space is limited due to constraints imposed by the process that is being undertaken. A more compact steering mechanism may also be required when adding this capability to existing equipment.
Most web steering or guiding systems are intended for positioning a web as it enters a process from a source roll. The guiding system corrects for a roll that is offset to one side or the other (a static error) or a roll that has lateral runout (uneven edge).
According to an exemplary embodiment, a position control system includes a roller rotatable about a longitudinal axis thereof and a pivotable member having a first member end rotatable about a first pivot axis and a second member end coupled to the roller. The second member end is rotatable about a second pivot axis spaced from the first pivot axis and the first and second pivot axes are movable relative to one another. A motor is adapted to move the roller along the longitudinal axis wherein movement of the roller along the longitudinal axis causes the pivotable member to tilt the roller relative to the longitudinal axis. A control system is responsive to a sensed parameter for controlling the motor.
According to another exemplary embodiment, a web position control system for controlling a position of a web to be guided by a roller rotatable about a longitudinal axis thereof includes a mounting structure that mounts the roller for rotational movement about the longitudinal axis, linear movement parallel to the longitudinal axis, and tilting movement relative to the longitudinal axis. A pivotable linkage has a first linkage end rotatable about a first pivot axis and a second linkage end coupled to the roller wherein the second linkage end is rotatable about a second pivot axis spaced from the first pivot axis and wherein the first pivot axis is fixed and the second pivot axis is movable relative to the first pivot axis. A motor is adapted to move the roller along the longitudinal axis wherein movement of the roller along the longitudinal axis causes the pivotable member to tilt the roller relative to the longitudinal axis. A control system includes a web position sensor for controlling the motor.
According to yet another exemplary embodiment, a method of controlling lateral position of a web traveling over a roller wherein the roller is mounted for rotation about a longitudinal axis by first and second opposed shaft portions includes the step of providing a linkage having a first end rotatable about a fixed axis and a second end rotatable about a movable axis spaced from the fixed axis wherein the second end of the linkage is coupled to the roller. The method further includes the step of providing a mounting structure and the step of providing a motor wherein the mounting structure mounts the roller for rotational movement about the longitudinal axis, linear movement parallel to the longitudinal axis, and tilting movement relative to the longitudinal axis. The motor is coupled to one of the first and second shaft portions and adapted to move the roller along the longitudinal axis wherein movement of the roller along the longitudinal axis causes the linkage to tilt the roller relative to the longitudinal axis. The method still further comprises the steps of sensing the lateral position of the web; and controlling the motor in response sensed lateral position of the web in turn to control lateral web position.
Other aspects and advantages will become apparent upon consideration of the following detailed description and the attached drawings wherein like numerals designate like structures throughout the specification.
FIG.7 is a block diagram of an exemplary controller of the control system of
Referring to
In some exemplary embodiments, each printhead 106 of the print unit 102 may print a particular color of ink. As may be apparent to one of skill in the art, the print unit 102 may include, for example, four printheads 106 that print cyan, magenta, yellow, and black ink to form four-color images on the medium 104. The print unit 102 may also include one or more other printheads 106 that print a custom color ink, a white ink, a metallic ink, and/or the like. Each printhead 106 includes a nozzle plate (not shown) having a plurality of nozzles (orifices) and during operation ink or another liquid may be ejected through such nozzles and deposited on the medium 104. The medium 104 may be any substrate on which ink or another material ejected by the printhead 106 may be deposited.
In an exemplary embodiment, the printing system 100 includes a controller 112 to coordinate relative movement between the print unit 102 and the medium 104, operation of the printheads 106 to print an image on the medium 104, and other functions, such as maintenance of the printheads 106. In some embodiments, during printing, the medium 104 may be transported in a direction parallel to a first axis 114 while the print unit 102 is transported in a direction parallel to a second axis 116 perpendicular to the first axis 114. In other embodiments, the print unit 102 may be transported in directions parallel to both the first axis 114 and the second axis 116, while the medium 104 is transported parallel to the first axis 114. Other variations of relative movement are possible.
Referring to
In the illustrated exemplary embodiments, some provision must be made to register the medium 104 with respect to the components of the printing system 100. Diagrammatically illustrated in
In an exemplary embodiment, the roller 202 may include integral outwardly extending roller shaft portions 204a, 204b or the outwardly extending shaft portions 204a, 204b may be integral with or unitarily formed with a central shaft section (seen in later FIGS.) and the roller 202 may be journaled on the central shaft section and/or the outwardly extending roller shaft portions 204a, 204b. In either event, the roller shaft portions 204a, 204b are mounted by bearings and/or other devices as described in greater detail hereinafter to maintain the roller in position along an x-direction (also referred to herein as the process direction) while permitting movement generally along a y-direction perpendicular to the x-direction (the y-direction is also referred to herein as the lateral direction). The roller 202 is rotatable about a longitudinal axis 206 of the roller 202 and the lateral movement along the y-direction generally occurs along the longitudinal axis 206. As noted in greater detail hereinafter, the roller 202 is also mounted for tilting movement of the longitudinal axis 206. Tilting of the longitudinal axis 206 of the roller 202 causes the lateral portions of the web 118 to traverse differential travel paths, in turn leading to the ability to control the lateral position of the web 118.
The control system 200 of
An actuator or motor 230 is also coupled to the roller 202, either directly or via one or more structural elements. In the illustrated exemplary embodiment of
Referring also to
It should be noted that the components illustrated in
Referring next to exemplary embodiments of
A distal portion 322 of the linear bearing rail 308 is disposed in a spring recess 324 defined by a mounting block 325 and is surrounded by a spring 326 disposed in the recess 324. The spring 326 is disposed between an end wall 328 defining the spring recess 324 and the base wall 329 of this recess in a compressed or uncompressed state. A spring swivel pusher element 330 is clamped around the bearing rail 308 by any suitable means, such as a threaded bolt or other fastener. Adjustment means (not shown) may adjust the height of each side of the roller as required for the particular manufacturing process without restricting tilting movement or movement along the y direction.
The rotary bearing sets 216a, 216b are identical, and hence, only the bearing set 216b will be described in detail. As seen in
As noted above, the bearing set 216a is identical to the bearing set 216b. A bolt, cap screw, or other fastener 358 extends through a bore (not shown) in inner races 360, and 361 through an arcuate slot 362 in a sensitivity adjuster plate 364 secured to the mounting block 325. A threaded end 366 of the bolt 358 is threaded in a nut 368 captured within a recess 370 located between the plate 364 and the mounting block 325.
A web edge sensor mount 350 is secured by any suitable means, such as fasteners and/or welds to one or both of the plate 364 and/or the mounting block 325. The web edge position sensor 234 (as shown in the FIGS.) is an IG series sensor sold by Keyence Corporation of America of Itasca, Ill., and is secured to the mount 350 at a location that is suitable for detecting a position of a web passing between legs 352, 354 of the mount 350.
The apparatus illustrated in
After energizing and calibrating the control system 200, during production, the control system monitors the lateral web position by sensing the output of the position sensor 234, and if the lateral web position deviates from the target value, the controller 232 operates the motor 318 to move the roller 202 along the y direction. The linkage 212 permits such lateral movement, which movement is facilitated by the fact that the linkage end 214b, while being rigidly fixed to the bearing rail 308, is otherwise free to float and moves with the rail 308 with or against the force exerted by the spring 326. During such movement, the fastener 248 and the spring swivel pusher element 330 rotate relative to the end 214b of the linkage 212. Also, the end 214a of the linkage 212 rotates about the bolt 358, which is fixed in position. This arrangement thus results in concurrent displacement along the y direction and tilting of the roller 202 in and out of the page as seen in
In summary, a position control system is capable of side-to-side linear displacement of a web to rapidly offset position errors along such direction as well as concurrent tilting movement to establish a stable web position at the desired position. The position control system accurately and efficiently corrects for a roll that is offset to one or another side (a static error) or a roll that has lateral runout (uneven edge) and has a compact form factor. An additional benefit of the illustrated exemplary embodiments is the mass of the moving mechanism is lower than most existing solutions, thus allowing for an improved response time to dynamic disturbances in web position without the need for costly actuators and support control systems.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar references in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.
Numerous modifications to the present disclosure will be apparent to those skilled in the art in view of the foregoing description. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the disclosure.
