Method and apparatus for sheet and carton blank aligning

Abstract

Apparatus and a method aligns and orients a moving article, such as a sheet or a carton blank during processing of the sheet/carton blank, relative to its intended path of travel through a conveyor-type assembly machine. In one embodiment, a pair of sensors detect passage of respective laterally spaced leading edge portions of the moving sheet and provide inputs to a controller which, in turn, provides an appropriate signal to one of a pair of spaced sheet-gripping rollers in contact with the respective laterally spaced portions of the sheet for aligning, or squaring, the sheet's leading edge relative to its intended path through the assembly machine. In another embodiment, a single sensor detects a linear lateral edge of the sheet and a single drive element orients and aligns the sheet's edge so that it is coincident with and parallel to a linear target line defining the intended path of travel.

What is claimed is: 
     
         1 . A method for aligning a linear edge of a moving sheet-like article transverse to an intended direction of travel of the sheet-like article, said method comprising:
 positioning first and second drive mechanisms in contact with respective laterally spaced first and second sections of the sheet-like article for displacing the sheet-like article generally in the intended direction of travel, wherein said first and second sheet-like article sections are disposed along and include the linear edge of the sheet-like article;   positioning first and second sensors in alignment with the first and second portions of the sheet-like article to respectively detect passage of the first portion of the linear edge past the first detector and passage of the second portion of the linear edge past the second detector for providing an output signal representing a difference in position relative to the intended direction of travel of the first and second portions of the sheet-like article; and   coupling a controller to said first and second sensors and to at least one of said drive mechanisms, wherein said controller is responsive to said output signal for changing the speed of one of the first or second portions of the sheet-like article so that the first and second portions are aligned in the desired orientation relative to the intended direction of travel.   
     
     
         2 . The method of  claim 1 , wherein the step of providing an output signal representing a difference in position relative to the intended direction of travel of the first and second portions of the sheet-like article and includes the step of detecting a leading edge of each of the article's first and second portions, measuring a time interval between these two detections, and calculating a correction signal to bring the sheet's first and second portions in alignment transverse to the intended direction of travel, and providing said correction signal to one of said drive mechanisms. 
     
     
         3 . The method of  claim 2  further comprising the step of equalizing the speeds of said first and second drive mechanisms and said first and second sheet portions following the aligning of said first and second sheet portions with each other. 
     
     
         4 . The method of  claim 1  further comprising the step of compensating for nonlinear alignment of said first and second drive mechanisms and said first and second sensors in aligning the linear edge of the sheet-like article. 
     
     
         5 . The method of  claim 1  further comprising the step of transporting the sheet-like article by means of upper and lower moving belts. 
     
     
         6 . The method of  claim 1  further comprising the step of transporting the sheet-like article by means of a vacuum belt. 
     
     
         7 . A method for aligning a straight lateral edge of a moving sheet-like article having an intended direction of travel with a target line, said method comprising:
 positioning first and second drive mechanisms in alignment with respective first and second laterally spaced portions of the sheet-like article for engaging and displacing said first and second lateral spaced portions of the sheet-like article in the intended direction of travel;   positioning a sensor adjacent to the sheet-like article's straight lateral edge for detecting the sheet-like article's straight lateral edge and a change in the extent of coverage of said sensor by the sheet-like article's straight lateral edge and for providing an output signal representing detection of said straight lateral edge and a change in the extent of coverage of said sensor by said straight lateral edge; and   coupling a controller to said second drive mechanism and to said sensor, wherein said controller is responsive to said output signal for increasing or decreasing the speed of said second drive mechanism and the speed of the second portion of the sheet-like article relative to said first portion for positioning and maintaining said straight lateral edge in alignment with and parallel to the target line.   
     
     
         8 . The method of  claim 7  further comprising the step of providing said sensor in the form of an analog gap sensor. 
     
     
         9 . The method of  claim 8 , wherein said analog gap sensor includes a glass bifurcated light guide and an analog output photoelectric sensor defining a sensing zone. 
     
     
         10 . The method of  claim 9  further comprising the step of establishing alignment of the sheet-like article's straight lateral edge with said target line when the straight lateral edge covers approximately one-half of said sensing zone. 
     
     
         11 . The method of  claim 7  further comprising the step of using a proportional, integral, derivative (PID) process for increasing or decreasing the speed of said second drive mechanism in proportion to the amount the lateral edge is not in alignment with the target line. 
     
     
         12 . The method of  claim 7  further comprising the step of equalizing the speeds of said first and second drive mechanisms and said first and second sheet portions following the alignment of said first and second sheet portions with each other. 
     
     
         13 . A method for aligning or squaring a moving sheet-like article having at least one straight lateral edge with an intended direction of movement of the article, said method comprising the steps of:
 linearly displacing the article generally along the intended direction of movement by engaging and displacing first and second laterally spaced portions of the sheet;   detecting the orientation of the article's straight lateral edge relative to the intended direction of movement;   rotating the sheet-like article either clockwise or counter clockwise by changing the speed of the sheet's second portion relative to its first portion so as to re-orient the article's straight lateral edge in a pre-determined orientation relative to the intended direction of movement.   
     
     
         14 . The method of  claim 13 , wherein the pre-determined orientation of the article's straight lateral edge is parallel for aligning or perpendicular for squaring the straight lateral edge relative to the intended direction of movement of the article. 
     
     
         15 . The method of  claim 13 , wherein the article's intended direction of movement is defined by a linear target line, said method further comprising the step of detecting when said lateral edge and said linear target line are coincident and controlling the speed of the sheet's second portion relative to the first portion so as to maintain said linear target line coincident with said lateral edge. 
     
     
         16 . A method for aligning or squaring a straight lateral edge of a sheet-like article with an intended direction of travel of the article, said method comprising the steps of:
 linearly displacing the article generally along the intended direction of travel by engaging and displacing first and second laterally spaced portions of the sheet, including using respective first and second servo control systems for engaging and displacing said first and second portions of the sheet, respectively;   detecting the orientation of the article's straight lateral edge relative to the intended direction of travel and outputting an analog control signal representing the orientation of said lateral edge relative to the intended direction of travel; and   providing said analog control signal to one of said first or second servo control systems for changing the speed of said first or second portions of the article in re-orienting the article relative to the intended direction of travel and aligning or squaring the article's straight lateral edge relative to the intended direction of travel.   
     
     
         17 . Apparatus for aligning a moving sheet-like article with its intended direction of travel defined by a linear target line, said apparatus comprising:
 first and second laterally spaced drive mechanisms in alignment with one another in a direction generally transverse to the sheet-like article's target line, wherein said first and second drive mechanisms engage and linearly displace first and second laterally spaced portions of the sheet-like article in the intended direction of travel, and wherein said first drive mechanism is disposed between the target line and the second drive mechanism;   a sensor disposed on the target line and adapted to detect a straight lateral edge of the moving sheet-like article and the angle between the sheet-like article's straight lateral edge and the target line direction of travel, wherein said sensor outputs a signal representing detection of said straight lateral edge and an angle between the target line and article's straight lateral edge; and   control means coupled to said second drive mechanism and to said sensor, wherein said control means is responsive to said output signal and to the angle between the target line and the sheet-like article's straight lateral edge for decreasing the speed of said second drive mechanism and of the article's second portion when said straight lateral edge is disposed between the target line and said drive mechanisms and for increasing the speed of said second drive mechanism and of the article's second portion when said target line is disposed between said straight lateral line and said drive mechanisms.