Patent Publication Number: US-2004045996-A1

Title: Web outfeed processing system for high performance printer

Description:
BACKGROUND OF INVENTION  
       [0001] Modern high speed laser printers have developed at a pace which has outstripped the performance capabilities of present-day web rewinding systems. One solution has been proposed by the Assignee herein, whereby two or more tension-free web loops are provided downstream of the printer to accommodate the variations in output speed of such laser printers. U.S. Pat. No. 5,992,789 issued Nov. 30, 1999. However, the technology of web handling systems must be further improved to accommodate the latest output web speed and displacement of today&#39;s high speed, high performance laser printers. For example, one such high performance laser printer now marketed by OCÉ has a requirement that the web take-up system must accommodate not only abrupt changes in speed, but reversals in direction on the order of several meters.  
       [0002] While tension-free loops generally afford the most efficient way of accommodating accumulated sections of web, not only during radical speed changes, but also during reversals in direction of the web, the accelerations and decelerations of the web in the latest printers have been found to exceed the capabilities of present-day tension-free loop controllers such as that referred to in, U.S. Pat. No. 5,992,789.  
       SUMMARY OF THE INVENTION  
       [0003] In accordance with the present invention, a relatively tall cabinet is provided so as to ensure an environmentally controllable space within which to accommodate a paper web that will be subjected to accelerations and decelerations on the order of magnitude of gravity itself, and to accommodate as well reverse motion of the web back into the printer on the order of several meters. The cabinet is preferably on the order of two meters in height and includes provision for maintaining a relatively high degree of humidity inside the cabinet as to counteract the drying affect on the paper web of the laser printer. The cabinet includes cooling capability as well, but without the usual moisture removal typical of present-day air conditioning systems. In its place, a source of shop air is expanded to create a cooling effect without adversely affecting the relatively humid air that is maintained in the cabinet by use of a conventional humidifier. This combination avoids the need for running the paper web through a solution to increase the humidity of the paper web emanating from the printer as is sometimes done in present-day print shops.  
       [0004] Instead of one or more tension-free loops the present invention portrays a weighted bar to provide a gravity-biasing force downwardly on the paper web loop. Although this is a known practice in the printing technology generally, the present invention adds a constant force spring-biasing means to the weighted roller. The acceleration and deceleration of the paper web can sometimes exceed the forces and acceleration otherwise expected from gravity itself, hence the need for constant force spring biasing means.  
       [0005] A control panel is preferably provided on the cabinet and includes status lites which indicate to the operator the status of the printer upstream of the cabinet, and also the status of downstream devices to which the paper web will be delivered, namely cutters, job separators, rewinders, fan folders, booklet makers, and other such paper web handling devices known to this art.  
       [0006] The control panel also displays certain conditions within the cabinet itself, namely the temperature, the humidity, and the output of a transducer probe or electrical resistance measuring device, provided adjacent the paper web and capable of measuring the humidity of the paper web itself. It should be noted that the temperature controlled atmosphere in the cabinet, required as per the present invention, is necessary to increase the humidity of the paper as a result of the drying effects on the paper web from the laser printer.  
       [0007] The control panel also preferably includes a laptop computer interface which will permit the operator to read out past histories of the computerized input to the status lites and other internal circuitry associated with control of the system components. The operator control panel serves to provide the user with an understanding of the effectiveness of the unit during the preceding day or other convenient timeframe.  
       [0008] Another optional feature of the present invention lies in the cabinet affording a convenient location along the path of the web from the printer to the downstream device for taking intermittent or continuous video inspection shots of both sides of the web, either for calibration purposes or for any other reason. Further, edge sensors are employed to provide input to the drive roller which is “steerable” in order to assure that the web tracks properly through the apparatus of the present invention. The display screen provided on the control panel is preferably of the touch-pad variety so as to allow control of the temperature and humidity within the cabinet, and for control of the video inspection cameras.  
       [0009] The control system for the loop in the cabinet may be similar to that for controlling the loops in the above U.S. Pat. No. 5,992,789. An ultrasonic transducer serves the bottom of the loop and provides an input to the control circuit for changing the speed of and direction or rotation for the drive roller. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
     [0010]FIG. 1 shows in schematic fashion a cabinet containing the components of the present invention, this view being a side elevation, with the path taken by the web shown in solid lines entering the cabinet and leaving the cabinet, and showing in broken lines the path taken by the web in forming the web loop. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
     [0011] Turning now to the drawing in greater detail, FIG. 1 shows a high performance laser printer  10  of the type which imparts heat to the paper web, and which requires changes in, not only the speed of the web exiting the printer, but reversals in direction for the web all in accordance with the operation of the high performance laser printer itself.  
     [0012] The web W enters the cabinet  12  through a slot  12   A  at the input side of the cabinet, and passes by a transducer, in the form of a compactive probe, which is adapted to measure the moisture content (or dryness) of the paper web. The output from the transducer is fed to a control circuit  14  which in turn is capable of controlling an air cooling unit  16  of the type operating from a source of air under pressure (such as shop air at 20 pounds plus or minus) that utilizes a valve to expand the air and thereby achieve cooling of the environment within the cabinet  12 .  
     [0013] The cabinet  12  also includes a humidifier  18  for introducing moisture into the atmosphere within the cabinet so as to increase the moisture content of the web and avoid the excessive dryness created in the web by the laser printer  10 .  
     [0014] The web undergoes a loop in the cabinet created by a weighted bar  20  provided in the web loop, and the position of the weighted bar and web loop is sensed by an ultrasonic transducer  22 . The output from this ultrasonic transducer is fed to the control circuit  14  for regulating the speed of the motor M, and hence the speed of idler rotation of the drive roller  24 . The web loop is defined between the drive roller  24  and an idle roller  26  over which the web is entrained as it passes through the cabinet from right to left and as indicated by the broken line in FIG. 1.  
     [0015] In the front side of the cabinet  12  a control panel  30  is provided, and that control panel has an interactive screen  30   A  as described previously, together with the status lites  30   B  also as described above.  
     [0016] The weighed bar  20  is acted upon by gravity to create a biasing force on the web that allows the web to be accommodated within the cabinet from movement of the bar between the positions shown. To increase the force exerted on the web a constant force spring  32  is provided so as to act on the weighted bar  20  and increase the force downwardly on the web in the event that accelerations of the web due to gravity is not sufficient for accommodating the speed changes required at the laser printer  
     [0017] In further accordance with the present invention cameras are provided to view one or both sides of the web passing along the path dictated by the cabinet components described previously. Operation of these video cameras can be provided for at the panel  30 . The cabinet also preferably include suitable means for neutralizing any static electricity build up on the web. Such a device is conveniently provided at or near the mounting structure for the cameras (not shown).  
     [0018] In light of the above disclosure it will be understood by those skilled in the art that the invention may be practiced otherwise than as specifically described herein, and it is therefore the intent of the application that the invention be defined by the scope of the appended claims.