Patent Application
20070017952
1. Field of the Invention
The present invention is directed to steering units on a process line and, more particularly, to linking steering units on a continuous process line running a continuous web material to create a cascading steering control scheme.
2. Description of Related Art
Referring to
In order to laterally move the steering assembly 914, a measurement of the web 912 in relation to the center 916 of the process line 900 is taken. This measurement provides feedback to the steering unit 910 in order to determine a direction and distance for pivoting or moving the steering assembly 914.
A conventional steering assembly 914 includes an articulated frame 920 and a roller 922. The roller 922 is stationary with respect to the frame 920. Movement of the frame 920 in turn effects movement of the roller 922. Thus, when it is determined that the web 912 is off-center and needs to be guided back to the center 916, lateral pivoting or movement of the frame 920 pivots the roller 922 which in turn directs the web 912 back toward the center 916 of the process line 900.
A process line 900 usually has multiple steering units 910 independently attempting to maintain the web 912 at the center 916 of the process line 900. For example, if a process line has two steering units (a downstream steering unit 924 and an upstream steering unit 926), the upstream steering unit 926 attempts to center the web 912 only at the upstream steering unit 926, and the downstream steering unit 924 attempts to center the web 912 only at the downstream steering unit 924. In many instances, if the web 912 is consistently tracking to one side, centering the web 912 at the upstream steering unit 926 does not compensate enough for the consistent tracking to one side. Thus, by the time a point in the web 912 which is re-centered at the upstream steering unit 926 reaches the downstream steering unit 924, it is already at an edge 928 or partially off of the process line 900. This causes damage to the edges of the web 912—damaging a length (possibly the entire length) of the material 912. This also causes delay by stopping the process line 900, removing the damaged material 912, and starting the process line 900 back up. Damage and delay result in lost profits.
It is an object of the present invention to provide a web steering system for a process line, in which downstream web steering units provide input regarding a web's running position to the upstream web steering units in order to inhibit a web from traveling excessively off-center downstream in the process line.
The process line cascade steering control system (“cascade system”) includes hardware and software that electronically links two or more steering units on a process line. The cascade system monitors where the web track tendency is on a downstream steering unit and intentionally offsets the upstream steering unit accordingly, so that the web will remain closer to the process line center.
To achieve this, the cascade system includes a feedback signal from a downstream steering unit, which is fed into a controller. The feedback is combined with other data to set the aim point of one or more of upstream steering units, usually to something other than process line center. By electronically linking separate steering units together, the downstream steering units can guide more effectively with a greater range of control.
New or existing electromechanical process equipment can be used in conjunction with the software programming. The software utilizes process line conditions, such as web dimensions, line process speed, accumulating loop position (if applicable), steering unit positions, and web positions relative to process line center as inputs. From those inputs, the controller, for example, a PLC, calculates and outputs the desired offset in the downstream and upstream unit(s) in order to produce a positive effect downstream.
Typically, in a process line with two steering units, each unit would be set to guide the material to the center of the line. If the material is consistently tracking toward one side of the line, as is often the case, each unit will independently move the material back to center.
However, in the cascade system, feedback from the downstream steering unit will cause the upstream steering unit to over-correct by guiding past the process line center to a point opposite where the material is tracking. This results in the downstream steering unit having to make a much smaller correction itself and, therefore, having a much greater range of control.
For example, consider a galvanizing line that processes a continuous steel strip (web). Virtually all metal strip has some camber. Camber is a slight curve along the length of the strip. That is, if a coil of steel were to be rolled out on a flat surface, a slight curve would be observed over the strip length. While this curve may only be a couple of feet over the length of a 5000-feet-long coil, it does affect steering through a line. In this example, the strip is 72 inches wide and the process line rolls are 80 inches wide. The camber will cause the strip to track consistently toward one side of the line. If the strip moves more than 4 inches off-center between any two steering units, the strip edge will be damaged ((80−72)/2=4).
With the cascade system in place, the consistent effect of the camber will be noted via feedback from the downstream steering unit, and the upstream steering unit will then guide the web past the line center toward the opposite side from where the cambered web is tracking. The adjustment to the guide point, instead of the line center, would steer the edge of the strip near the roll edge away from the camber direction. Thus, the cascade system can run a strip with twice the camber, or other steering problems, without damage.
A complete understanding of the present invention will be obtained from the following description when taken in connection with the accompanying drawing figures, wherein like reference characters identify like parts throughout.
For purposes of the description hereinafter, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” and derivatives thereof shall relate to the present invention as it is oriented in the accompanying drawing figures. However, it is to be understood that the present invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the present invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting.
Referring to
In general, the downstream steering unit 106 collects positional data regarding the web material 102 near the downstream steering unit 106 and sends it to the downstream controller and the upstream controller. The upstream steering unit 108 collects positional data regarding the web material 102 near the upstream steering unit 108 and sends it to the upstream controller 114. Positional data may be an actual position of the web 102 within the process line 100 or may be a position of a piece of equipment (a frame or a roller of a steering unit) used to steer the web 102.
The downstream controller 112 utilizes the positional data from the downstream steering unit 106, along with conditions of the process line 100, such as speed, type of material, etc., to determine an adjustment to be made to the downstream steering unit 106 in order to guide the web 102 into a position, such that the web 102 will run along a center 116 of the process line 100.
The upstream controller 114 utilizes the positional data from the downstream steering unit 106 and the upstream steering unit 108, along with conditions of the process line 100, such as speed, type of material, etc., to determine an adjustment to be made to the upstream steering unit 108 in order to guide the web 102 into a position such that the web 102 will run along the center 116 of the process line 100 further down the process line 100 from the upstream steering unit 108.
If the cascade system includes only one controller 110, each steering unit 104 is in communication with the controller 110, and the controller 110 handles all calculations.
In a preferred embodiment of the present invention, the downstream steering unit—106 includes a downstream measurement device 118 and a downstream steering assembly 120. The downstream measurement device 118 is located proximate the downstream steering assembly 120. The downstream measurement device 118 is positioned to collect a downstream measurement of the web material 102 in relation to the center 116 of the process line 100. The downstream measurement is sent to the downstream controller 112. The downstream measurement device 118 may be any conventional device capable of measuring a position of the web 102.
The downstream steering assembly 120 includes a downstream frame 122 and a downstream roller 124. The downstream frame 122 is moveable, for example, pivotable, in relation to the center 116 of the process line 100. The downstream roller 124 is supported by the downstream frame 122 and is stationary with respect to the downstream frame 122. With this construction, when the downstream frame 122 is pivoted, the downstream roller 124 pivots as well. The movement of the downstream frame 122 and the downstream roller 124 exerts a force on the web 102 running along the downstream roller 124 and thereby causes the web 102 to move with respect to the center 116 of the process line 100.
The upstream steering unit 108 includes an upstream measurement device 126 and an upstream steering assembly 128. The upstream measurement device 126 is located proximate the upstream steering assembly 128. The upstream measurement device 126 is positioned to collect an upstream measurement of the web material 102 in relation to the center 116 of the process line 100. The upstream measurement is sent to the upstream controller 114. The upstream measurement device 126 may be any conventional device capable of measuring a position of the web 102.
The upstream steering assembly 128 includes an upstream frame 130 and an upstream roller 132. The upstream frame 130 is moveable, for example, pivotable, in relation to the center 116 of the process line 100. The upstream roller 132 is supported by the upstream frame 130 and is stationary with respect to the upstream frame 130. With this construction, when the upstream frame 130 is pivoted, the upstream roller 132 pivots as well. The movement of the upstream frame 130 and the upstream roller 132 exerts a force on the web 102 running along the upstream roller 132 and thereby causes the web 102 to move with respect to the center 116 of the process line 100.
In use, the downstream controller 112 receives the downstream data. Along with process line conditions, the downstream controller 112 utilizes the downstream data to determine a downstream adjustment to be made to the downstream roller 124 via the downstream frame 122. The downstream adjustment is an amount to pivot the downstream frame 122 in order to guide the web material 102 back toward the center 116 of the process line 100.
The upstream controller 114 receives the upstream data. Additionally, the upstream controller 114 receives positional data regarding the web material 102 at the downstream steering unit 106. The positional data may be the downstream data or a position of the downstream roller 124.
Along with process line conditions, the upstream controller 114 utilizes the position of the downstream roller 124 (or the downstream data) and the upstream data to determine an upstream adjustment to be made to the upstream roller 132 via the upstream frame 130. The upstream adjustment is an amount to pivot the upstream frame 130 in order to guide the web material 102. The upstream adjustment does not necessarily guide the web 102 back to the center 116 of the process line 100. In most cases, the upstream adjustment will over-compensate for the downstream position of the web 102 at the downstream steering unit 106. In other words, the upstream adjustment will typically guide the web 102 to a position beyond the center 116 of the process line 100 to compensate for tracking of the material to one side.
Referring to
Referring to
It is common for a process line 100 to have more than two steering units 104. In such case, the lead steering unit is the upstream steering unit 108, and the end steering unit is the downstream steering unit 106. Middle steering units 134 function as both downstream and upstream steering units.
In one embodiment of the present invention, data collected by a downstream steering unit is utilized to determine an adjustment for itself and the immediate upstream steering unit (the previous steering unit when traveling along the direction of travel of the web through the process line). Data collected by the upstream steering unit is utilized to determine an adjustment for itself only. The data collected by the steering units “cascades” back through the process line.
For example, a process line has four steering units: SU1, SU2, SU3, and SU4. SU1 is at the beginning of the line and is the upstream steering unit. SU4 is at the end of the line and is the downstream steering unit. SU2 and SU3 are both in the process line between SU1 and SU4. Thus, SU2 and SU3 act as both an upstream steering unit and a downstream steering unit.
Data collected at SU4 is utilized to position SU4 and SU3. Data collected at SU3 is utilized to position SU3 and SU2. Data collected at SU2 is utilized to position SU2 and SU1. Data collected at SU1 is utilized to position SU1.
Thus, any downstream data is utilized to effect movement of the immediate upstream steering unit in order to inhibit the web from moving too far off-center by the time it reaches the downstream steering unit, before it strays too far and gets damaged or processed improperly.
In another embodiment of the present invention, data collected by a downstream steering unit is utilized to determine an adjustment for itself and all steering units located upstream in the process line (the previous steering units when traveling along the direction of travel of the web through the process line). Data collected by an upstream steering unit is utilized to determine an adjustment for itself only. The data collected by the steering units “cascades” back through the process line.
For example, a process line has four steering units: SU1, SU2, SU3, and SU4. SU1 is at the beginning of the line and is the upstream steering unit. SU4 is at the end of the line and is the downstream steering unit. SU2 and SU3 are both in the process line between SU1 and SU4. Thus, SU2 and SU3 act as both an upstream steering unit and a downstream steering unit.
Data collected at SU4 is utilized to position SU4, SU3, SU2, and SU1. Data collected at SU3 is utilized to position SU3, SU2, and SU1. Data collected at SU2 is utilized to position SU2 and SU1. Data collected at SU1 is utilized to position SU1.
Thus, any downstream data is utilized to effect movement of the upstream steering units in order to inhibit the web from moving too far off-center by the time it reaches the furthermost downstream steering unit, before it strays too far and gets damaged or processed improperly.
It will be understood by those skilled in the art that while the foregoing description sets forth in detail preferred embodiments of the present invention, modifications, additions, and changes might be made thereto without departing from the spirit and scope of the present invention.
