Web lateral position control system using both coarse and fine mode control means

A control system for controlling the relative lateral position of a moving web of material having a repeating series of graphics printed thereon based upon the lateral position of the graphics with respect to a fixed station along the web comprising:

• (a) optical sensor means for sensing the relative lateral position of a longitudinally extending guide line printed on the web in fixed spacial relationship with the repeating series of graphics, and generating an optical sensor control signal indicative of the relative lateral position of said guide line within relatively narrow transversely extending guide line detection zone of said optical sensor means, said optical sensor control signal being also indicative of the presence and absence of said guide line from said detection zone;
• (b) web edge sensor means for sensing the relative lateral position of an edge portion of said moving web and generating an edge sensor control signal indicative of the relative lateral position of said web edge portion within a relatively broad transversely extending edge detection zone of said web edge sensor means;
• (c) web lateral position adjustment means for adjusting the relative lateral position of the moving web in response to a control signal from said optical sensor means in a fine control mode and from said edge sensor means in a coarse control mode;
• (d) mode selection means for receiving said optical sensor signal and for enabling operation of said control system in said fine control mode during periods when said optical sensor signal indicates the presence of said guide line in said optical sensor detection zone and for enabling operation of said control system in the coarse control mode during periods when said sensor signal indicates the absence of said guide from said optical sensor detection zone.

A method of controlling the lateral position of a moving web of material having at least one substantially linear lateral side edge and having graphics printed thereon including a guide line oriented in generally parallel relationship to the linear lateral side edge of the web at a preset distance therefrom, comprising the steps of:

• (a) monitoring the relative lateral position of the lateral edge of the web with an edge sensor having a relatively broad detection zone and generating a web edge monitoring signal in response to the detected position of the lateral edge of the web;
• (b) monitoring the relative lateral position of the guide line with a line sensor having a relatively narrow detection zone and generating a guide line monitoring signal in response to the detected position of the guide line and also to the detected presence and absence of the guide line from the detection zone;
• (c) controlling the lateral position of the web in a coarse operating mode based on the web edge monitoring signal;
• (d) controlling the lateral position of the web in a fine operating mode based on the guide line monitoring signal;
• (e) selecting one of the coarse operating mode and the fine operating mode based upon the guide line monitoring signal by selecting the coarse operating mode when the guide line is detected to be absent from the detection zone of the line sensor and by selecting the fine operating mode when the guide line is detected to be present in the detection zone of the line sensor.

A method of controlling the lateral position of a moving web of material comprising the steps of:

• (a) monitoring a lateral position indicating indicia of the web with a first sensor having a relatively small width first detection zone and generating a first detection signal in response thereto;
• (b) controlling the lateral position of the web in response to the first detection signal so long as the lateral position indicating indicia monitored by the first sensor is detected in the first detection zone;
• (c) monitoring a lateral position indicating indicia of the web with a second sensor having a relatively large width second detection zone and generating a second detection signal in response thereto;
• (d) controlling the lateral position of the web in response to the second detection signal so long as the lateral position indicating indicia monitored by the first sensor is detected to be absent from the first detection zone.