Patent Publication Number: US-2015068377-A1

Title: Cutting a moving media

Description:
BACKGROUND 
     Paper and other print media for large format inkjet printers may be supplied as pre-cut sheets or rolls of flexible web. Printers printing on a media web sometimes include a cutter that automatically cuts the web into the desired size sheets before, during, or after printing. 
    
    
     
       DRAWINGS 
         FIG. 1  is a block diagram illustrating an inkjet printer in which examples of a new, diagonal media cutter may be implemented. 
         FIG. 2  is a diagrammatic elevation view illustrating a web printer that includes a diagonal web cutter, according to one implementation of the invention. 
         FIG. 3  is a plan view illustrating one example of a diagonal web cutter such as might be used in the printers shown in  FIGS. 1 and 2 . 
         FIGS. 4 and 5  illustrate the operation of the diagonal cutter shown in  FIG. 3 . 
         FIGS. 6 and 7  illustrate cutting the print media at other than a square cut. 
         FIG. 8  is a block diagram illustrating one example of a cutter that may be used for the diagonal cutter shown in  FIGS. 1-5 . 
         FIGS. 9-12  illustrate the operation of a rotary blade cutter as one example for the diagonal cutter shown in  FIGS. 1-5 . 
         FIGS. 13 and 14  illustrate a retractable cutter blade that may be used in the cutter shown in  FIGS. 9-12 . 
     
    
    
     The same part numbers are used to designate the same or similar parts throughout the figures. 
     DESCRIPTION 
     In conventional inkjet web printers, the web is stopped to allow the cutter to cut the web. The cutting operation in such printers is often quite fast compared to the printing operation and, therefore, stopping the web for cutting does not significantly reduce the throughput of the printer. However, as faster inkjet printers are developed, stopping the web for printing may significantly reduce printer throughput. Consequently, a new media cutter has been developed to allow cutting a print media web in large format inkjet printers without stopping the web during cutting. The new cutter, however, is not limited to use in inkjet printers or to cutting media webs, but may be implemented in other devices and/or for cutting sheets, webs, or other media forms. The examples and implementations described below should not be construed to limit the scope of the invention, which is defined in the Claims that follow this Description. 
     In one example, a new cutter for cutting a moving media includes a cutting tool driven along a straight guide line at a speed V C  sufficient to cut moving media along a straight cut line different from the guide line. While it is expected that the cut line will typically be perpendicular to the direction the media moves during the cutting operation, thus making a square cut, other straight cut lines are possible. For making a square cut, the guide line is oriented at an acute angle a measured with respect to the direction the media moves and the speed V C  of the cutting tool is determined by the equation 
     
       
         
           
             
               V 
               C 
             
             = 
             
               
                 V 
                 M 
               
               
                 cos 
                  
                 
                     
                 
                  
                 α 
               
             
           
         
       
     
     where V M  is the speed of the media. 
     As used in this document, an “acute angle” means an angle less than 90° and greater than 0°. 
       FIG. 1  is a block diagram illustrating an inkjet printer  10  in which examples of a new media cutter may be implemented. Referring to  FIG. 1 , inkjet printer  10  includes a printhead  12 , an ink supply  14 , a carriage  16 , a print media transport mechanism  18  and a controller  20 . Printhead  12  in  FIG. 1  represents generally one or more printheads and the associated mechanical and electrical components for dispensing drops of ink on to a sheet or a continuous web of paper or other print media  22 . Printhead  12  may include one or more stationary printheads that span the width of print media  22 . Alternatively, printhead  12  may include one or more printheads that are scanned back and forth on carriage  16  across the width of media  22 . Printhead  12  may include, for example, thermal ink dispensing elements or piezoelectric ink dispensing elements. Other printhead configurations and ink dispensing elements are possible. Controller  20  in  FIG. 1  represents generally the programming, processor(s) and associated memories, and the electronic circuitry and components needed to control the operative elements of printer  10 . 
     Ink chamber  24  and printhead  12  are usually housed together in an ink pen  26 , as indicated by the dashed line in  FIG. 1 . Ink supply  14  supplies ink to printhead  12  through ink chamber  24 . Ink supply  14 , chamber  24  and printhead  12  may be housed together in an ink pen. Alternatively, ink supply  14  may be housed separate from ink chamber  24  and printhead  12 , as shown, in which case ink is supplied to chamber  24  through a flexible tube or other suitable conduit. Printer  10  typically will include several ink pens  26 , for example one pen for each of several colors of ink. 
     Media transport  18  advances print media  22  past printhead  12 . For a stationary printhead  12 , media transport  18  may advance media  22  continuously past printhead  12 . For a scanning printhead  12 , media transport  18  may advance media  22  incrementally past printhead  12 , stopping as each swath is printed and then advancing media  22  for printing the next swath. Printer  10  also includes a diagonal cutter  28  for cutting print media  22 . As described in detail below, cutter  28  is configured to move in a straight line and make a square cut (or other desired cut angle) without stopping media  22 . While it is expected that a diagonal cutter  28  will usually be implemented in a web fed printer  10  printing on a web media  22 , a diagonal cutter  28  could also be implemented in a sheet fed printer  10  printing on sheet media  22 . 
       FIG. 2  is a diagrammatic elevation view illustrating a printer  10  that includes a diagonal web cutter  28 , according to one implementation of the invention. Referring to  FIG. 2 , printer  10  includes, for example, a group of multiple ink pens  26  for dispensing different color inks. Ink pens  26  are mounted on a carriage  16  over a platen  30 . In the example implementation shown in  FIG. 2 , media transport  18  in printer  10  includes a web supply roll  32  and a series of transport rollers  34 ,  36 , and  38  for moving a media web  22  along a media path  40  from supply roll  32  over a platen  30  at print zone  42  to an output basket  44 . Media guides  46  may be used to support and guide media  22  along media path  40 . In one example, cutter  28  (in solid lines) is positioned upstream from print zone  42  between transport rollers  34  and  36 . In another example, cutter  28  (in dashed lines) is positioned downstream from print zone  42  between transport rollers  36  and  38 . 
     Once media web  22  is cut, the downstream, cut part of the web could be characterized as a media sheet rather than a media web, particularly for shorter lengths of cut web. For convenience, however, and to avoid confusion between the use of a cutter  28  in a web fed printer such as printer  10  shown in  FIG. 2  and the use of a cutter  28  in a sheet fed printer, reference to “web” media or a media “web” means the print media in a web fed printer both before and after the web is cut and reference to a “sheet” media or a media “sheet” means the print media in a sheet fed printer both before and after a sheet is cut. 
       FIG. 3  is a plan view illustrating one example of a diagonal web cutter  28  such as might be used in the inkjet printers shown in  FIGS. 1 and 2 .  FIGS. 4 and 5  illustrate the operation of cutter  28  shown in  FIG. 3 . Referring to  FIG. 3-5 , cutter  28  includes a cutting tool  48  and a stationary, linear guide  50 . “Stationary” in this context means the guide is stationary during a cutting operation, and does not mean the guide is immovable. Indeed, it is expected that the position of guide  50  will be adjustable in some implementations. Guide  50  is oriented at an acute angle α measured with respect to the direction media  22  moves past guide  50 . Thus, cutting tool  48  moves along a straight guide line  52  ( FIG. 4 ) in a direction not perpendicular to the advancing media  22 . It has been demonstrated that cutting tool  48  and media  22  can be moved along linear paths at the same time in different directions to make a square cut line  54  ( FIG. 5 ) without stopping media  22  during the cutting operation. 
     The velocity of cutting tool  48  is designated by a vector V C  in  FIG. 3 . The velocity of media  22  is designated by a vector V M  in  FIG. 3 . The speed of each part (i.e., the magnitude of the velocity vector) is designated V C  and V M , respectively. (Velocity V in bold typeface and speed V in italics typeface.) Cutting tool  48  is driven along at a speed V C  and at an angle α sufficient to cut the moving media  22  along a straight cut line  54  different from the guide line  52 . While it is expect that the cut line will typically be perpendicular to the direction the media moves during the cutting operation for making a square cut, other cut lines are possible as described below with reference to  FIGS. 6 and 7 . For a square cut line  54  shown in  FIG. 5 , where guide line  52  is oriented at an acute angle α measured with respect to the direction the media moves, the speed V C  of the cutting tool is determined by Equation 1 below. 
     
       
         
           
             
               
                 
                   
                     V 
                     C 
                   
                   = 
                   
                     
                       V 
                       M 
                     
                     
                       cos 
                        
                       
                           
                       
                        
                       α 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
     where V M  is the speed of the media. 
     In general, Equation 1 defines the relationship among cutting tool speed V C , guide angle α, and media speed V M  for a square cut line. Thus, although the form of Equation 1 above specifies V C  as a function of V M  and guide angle α, Equation 1 could be rewritten to specify guide angle α as a function of cutting tool speed V C  and media speed V M , or to specify media speed V M  as a function of cutting tool speed V C  and guide angle α. 
     The velocity of cutting tool  48 , V C , can be divided into two components—one component V CY  in the same direction media  22  is moving (in the Y direction in  FIG. 3 ) and a second component V CX  perpendicular to the direction media  22  is moving (in the X direction in  FIG. 3 ). If the component of cutting tool velocity in the direction of media advance, V CY , has the same magnitude as the media velocity, V M , (i.e., V CY =V M ), then the cutter movement on media  22  is perpendicular to the direction of media advance. Thus, the cutting component perpendicular to media  22 , V CX , is the only component cutting media  22  and the cut is made as if media  22  was stopped and cutting tool  48  driven straight across media  22  when, in fact, media  22  has never stopped moving. 
       FIGS. 6 and 7  illustrate cutting media  22  at other than a square cut. Referring to  FIGS. 6 and 7 , cut line  54  is made at an acute angle θ with respect to the direction media  22  is moving (which is parallel to the edges of media  22 , the Y direction in  FIGS. 6 and 7 ). Cut line  54  slopes down from left to right in  FIG. 6  and up from left to right in  FIG. 7 . In either case, the relationship among cutter speed V C , guide angle α, and cut line angle θ is defined by equation 2 below. 
     
       
         
           
             
               
                 
                   
                     tan 
                      
                     
                         
                     
                      
                     O 
                   
                    
                   
                     - 
                     = 
                   
                    
                   
                     
                       
                         V 
                         C 
                       
                        
                       sin 
                        
                       
                           
                       
                        
                       α 
                     
                     
                        
                       
                         
                           V 
                           M 
                         
                         - 
                         
                           
                             V 
                             C 
                           
                            
                           cos 
                            
                           
                               
                           
                            
                           α 
                         
                       
                        
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   2 
                 
               
             
           
         
       
     
     where V M  is the speed of the media and |V M −V C  cos α| is the absolute value of V M −V C  cos α. 
     In one example of an inkjet web printer  10  shown in  FIG. 2 , in which the media web  22  advances at a speed in the range of 1 inch/second to 8 inches/second, testing indicates a cutter guide angle α in the range of 80° to 86° and a corresponding cutter speed V C  according to Equation 1 above makes a good quality square cut for a paper web  22 , if web  22  is not under tension during the cutting operation. In one specific example, therefore, a cutter speed V C  of 90 inches/second is needed to make a square cut on a paper web media  22  advancing at 8 inches/second for a guide angle αof 85°. Relieving tension (if any) in a media web  22  during cutting improves the quality of the cut. Moving media  22  into cutter  28  slightly faster than moving media  22  away from cutter  28  during a cutting operation helps relieve tension in media  22  at cutter  28 . If this technique is used to relieve web tension, then the speed of media  22  moving away from cutter  28  is used for V M  in Equations 1 and 2. 
     The specific parameters noted above do not preclude the use of other acute guide angles α and cutter speeds V C . Rather, these parameters are given to illustrate one example implementation in a real printing environment. 
       FIG. 8  is a block diagram illustrating one example of a cutter that may be used for a diagonal cutter  28  shown in  FIGS. 1-5 .  FIGS. 9-12  illustrate an operating sequence of a rotary blade cutter as one example for a diagonal cutter shown in  FIGS. 1-5 . Referring first to  FIG. 8 , cutter  28  includes a cutting tool  48 , linear guide  50 , a variable speed motor  56 , and a motor controller  58 . Controller  58  controls the speed of motor  56  to drive cutting  48  along guide  50  at the desired speed V C . One advantage of at least some examples of the new, diagonal cutter is the ability to adapt conventional variable speed media cutters to the new design. For example, a conventional variable speed rotary blade cutter may be oriented at the desired guide angle α and driven at the desired speed to achieve a square cut, as shown in  FIGS. 9-12 . Motor controller  58  in  FIG. 8  may be integrated into printer controller  20  ( FIG. 1 ) or a separate, programmable motor controller may be used. 
     As best seen by comparing  FIGS. 9 ,  10 , and  11 , a rotary blade cutting tool  48  is driven at the desired speed V C  along a stationary, linear guide  50  oriented at the desired angle α, as described above, to produce a square cut across media  22 . Then, as shown in  FIG. 12 , cutting tool  48  is returned to its starting position in preparation for another cutting operation. To return cutting tool  48  to its starting position with stopping media  22 , a conventional retractable rotary blade cutting tool  48  such as that shown in  FIGS. 13 and 14  may be used.  FIG. 13  shows tool  48  with a cutting blade  60  deployed for cutting.  FIG. 14  shows tool  48  with cutting blade  60  retracted for returning to the starting position. In the example shown in  FIGS. 13 and 14 , a blocker  62 ,  64  at each end of the cutter path engages the end of a lever arm  66  on cutting tool  48  to retract and deploy blade  60 , respectively, which is supported in a carriage  68 . A biasing spring  70  helps retain blade  60  in each position. 
     As noted above, the examples and implementations shown in the Figures and described above do not limit the invention. Other examples and implementations are possible. Accordingly, these and other examples, implementations, configurations and details may be made without departing from the spirit and scope of the invention, which is defined in the following claims.