Abstract:
A printing unit is provided. The printing unit includes an ink feed system, a plate cylinder and an inker having multiple rollers and a belt wrapped around the rollers. The belt accepts ink from the ink feed system and transfers the ink to the plate cylinder. A method of printing and an inker are also provided.

Description:
[0001]    The present invention relates generally to printing presses, and more particularly to inking apparatuses used in printing presses. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many printing processes, such as the lithographic printing process, may use rollers and cylinders to deliver and apply ink to a substrate, such as a paper web. An ink metering system, such as a fountain and ductor roll, may apply ink at one end of an arrangement of rollers called an inker. As the rollers rotate, ink is transferred between adjacent rollers at roller contact locations, called nips. Eventually, ink is applied by the rollers to image areas on a plate cylinder containing text and images to be printed. The plate cylinder may then transfer the ink either directly to the substrate or to another rotating cylinder, called a blanket cylinder, which applies the ink to the substrate. 
       SUMMARY OF THE INVENTION 
       [0003]    A printing unit is provided. The printing unit includes an ink feed system, a plate cylinder and an inker having multiple rollers and a belt wrapped around the rollers. The belt accepts ink from the ink feed system and transfers the ink to the plate cylinder. 
         [0004]    A method of printing is also provided. The method includes the steps of applying ink from the ink feed system to a belt, moving the belt along a path of the belt and transferring the ink from the belt to a plate cylinder. 
         [0005]    An inker is also provided. The inker includes multiple rollers and an ink transfer belt wrapped around the rollers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The present invention is described below by reference to the following drawings, in which: 
           [0007]      FIG. 1  schematically shows a printing unit including an inker according to one embodiment of the present invention; and 
           [0008]      FIG. 2  schematically shows a printing unit including an inker according to a further embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  describes a printing unit  10  according to the present invention, having an ink feed system  12 , an inker  14 , a plate cylinder  16 , and a backup cylinder  18 . Ink feed system  12  feeds ink into inker  14 . Inker  14  delivers ink to plate cylinder  16 . Plate cylinder  16  applies ink to a substrate  20  in a nip  22  formed between plate cylinder  16  and backup cylinder  18 . 
         [0010]    Inker  14  includes a belt  24 , an outer idler roller  26 , inner idler rollers  28 , vibrator rollers  30  and a tensioning roller  32 . Belt  24  wraps around idler rollers  28  and tensioning roller  32  and passes inside of idler roller  26 , vibrator rollers  30  and plate cylinder  16 , which assist in guiding belt  24  along a belt path  34 . Belt  24  travels along belt path  34  at a velocity V 1 . Surfaces of idler roller  26 , idler rollers  28  and vibrator rollers  30  adjacent to belt  24  also travel at velocity V 1 . Tensioning roller  32  applies a force F 1  to keep belt  24  at a desired tension. Idler rollers  28 ,  36  may be rubber coated. 
         [0011]    In one preferred embodiment, tensioning roller  32  may be driven to translate belt  24 . In alternative embodiments of the present invention, a driven roller may be added to translate belt  24  or one of the idler rollers  28  may be replaced by a driven roller. 
         [0012]    In one preferred embodiment, belt  24  may be a tooth-driven belt and tensioning roller  32  may include teeth to drive belt  24  to prevent belt  24  from slipping during velocity changes of printing unit  10 . Slipping during operation may cause issues with surface quality and increase waste product. For a friction-driven embodiment of belt  24 , a center cross-section of an inner perimeter of belt  24  may include a cut-out portion. The cut-out portion may limit an amount of lateral travel of belt  24 , in relation to a center axis of plate cylinder  16 , caused by vibrator rollers  30  or other forces during operation. Accordingly, idler rollers  28  and tensioning roller  32  may include circumferential protrusions that are received by the cut-out portion of belt  24  during operation. 
         [0013]    The ink received by inker  14  from ink feed system  12  is transported by belt  24  to plate cylinder  16  along belt path  34 . As belt  24  travels around idler roller  26  and vibrator rollers  30 , ink thickness variations on belt  24  may be reduced by ink transfer between belt  24 , idler roller  26 , and vibrator rollers  30 . Vibrator rollers  30  oscillate back and forth across the belt width to further reduce ink thickness variations. The ink transferred by belt  24  to plate cylinder  16  is replaced by additional ink from ink feed system  12  with each passage of belt  24  around belt path  34 . 
         [0014]    The present invention may simplify the process of changing a plate cylinder diameter D 1 . In the prior art, the rollers adjacent to the plate cylinder, called form rollers, are typically only capable of small movements normal to the plate surface and therefore may not easily accommodate a new plate cylinder  36  with a diameter D 2 , represented by a dashed circle in  FIG. 1 . In the present invention, new plate cylinder  36  may be more easily installed because belt  24  simply takes a new path  38  around new plate cylinder  36  and tensioning roller  32  moves to a new position  40 . The ability to change print cylinder diameter may advantageously allow the length of printed images to be changed. 
         [0015]    In the embodiment shown in  FIG. 1 , since a blanket cylinder is not used, new plate cylinder diameter D 2  is not limited to being equal to a blanket cylinder diameter divided by some integer. Directly printing from plate cylinder  16  to substrate  20  thus may allow new plate cylinder diameter D 2  to be more freely chosen. 
         [0016]      FIG. 2  describes a printing unit  50  according to the present invention, having an ink feed system  52 , an inker  54 , a water feed system  56 , a plate cylinder  58 , a blanket cylinder  60 , and a backup cylinder  62 . Ink feed system  52  feeds ink into inker  54 . Inker  54  delivers ink to plate cylinder  58 . Plate cylinder  58  applies ink to blanket cylinder  60 , and blanket cylinder  60  applies ink to a substrate  64 . In another embodiment, printing unit  50  may be a perfecting printing unit and backup cylinder  62  may be a blanket cylinder printing on the other side of substrate  64 . 
         [0017]    Water feed system  56  is used when the printing process is lithographic. Water feed system  56  delivers an aqueous solution, called fountain solution, to the plate so that ink sticks to the plate image areas and not to the non-image areas. 
         [0018]    Inker  54  includes a belt  66 , an outer idler roller  68 , a rider roller  70 , inner idler rollers  72 , vibrator rollers  74 , and a tensioning roller  76 . Belt  66  wraps around idler roller  68 , rider roller  70 , idler rollers  72 , vibrator rollers  74 , and plate cylinder  58 . Belt  66  travels around a belt path  78  at a velocity V 2 . The surfaces of idler roller  68 , rider roller  70 , idler rollers  72 , and vibrator rollers  74  adjacent to belt  66  also travel at velocity V 2 . Tensioning roller  76  applies a force F 2  to keep belt  66  at a desired tension. 
         [0019]    In one preferred embodiment, tensioning roller  76  may be driven to translate belt  66 . In alternative embodiments of the present invention, a driven roller may be added to translate belt  66  or one of the idler rollers  72  may be replaced by a driven roller. 
         [0020]    In one preferred embodiment, belt  66  may be a tooth-driven belt and tensioning roller  76  may include teeth to drive belt  66  to prevent belt  66  from slipping during velocity changes of printing unit  50 . Slipping during operation may cause issues with surface quality and increase waste product. In an alternative embodiment, belt  66  may be may be friction-driven. For a friction-driven embodiment of belt  66 , a center cross-section of an inner perimeter of belt  66  may include a cut-out portion. The cut-out portion may limit an amount of lateral travel of belt  24 , in relation to a center axis of plate cylinder  16 , caused by vibrator rollers  30  or other forces during operation. Accordingly, idler rollers  72  and tensioning roller  76  may include circumferential protrusions that are received by the cut-out portion of belt  66  during operation. 
         [0021]    The ink received by inker  54  from ink feed system  52  is transported by belt  66  to plate cylinder  58  along belt path  78 . As belt  66  travels around idler roller  68 , rider roller  70 , and vibrator rollers  74 , ink thickness variations on belt  66  may be reduced by ink transfer between belt  66  and idler roller  68 , rider roller  70 , and vibrator rollers  74 . Vibrator rollers  74  oscillate back and forth across a width of belt  66  to further reduce ink thickness variations. The ink transferred by belt  66  to plate cylinder  58  is replaced by additional ink from ink feed system  52  with each passage of belt  66  around belt path  78 . 
         [0022]    The present invention may simplify the process of throwing plate cylinder  58  and blanket cylinder  60  off impression. During printing, plate cylinder  58  and blanket cylinder  60  are on impression, meaning plate cylinder  58  and blanket cylinder  60  are in contact to form a nip  80 , and blanket cylinder  60  and backup cylinder  62  are in contact with substrate  64  to form a nip  82 . Cylinders  58 ,  60  may be thrown off impression, so that plate cylinder  58  and blanket cylinder  60  move apart from one another creating a gap G 1  between blanket cylinder  60  and substrate  64  and a gap G 2  between plate cylinder  58  and blanket cylinder  60 . The dashed circles in  FIG. 2  show off impression locations  84 ,  86 ,  88  for plate cylinder  58 , blanket cylinder  60 , and backup cylinder  62 , respectively. When blanket cylinder  60  is thrown off from substrate  64  and plate cylinder  58  is thrown off from blanket cylinder  60 , and plate cylinder  58  and blanket cylinder  60  are at off impression locations  84 ,  86 , respectively, a plate of plate cylinder  58  may be changed and a blanket on blanket cylinder  60  may be changed. Automated mechanisms such as autoplating may used for these changes. 
         [0023]    In the prior art, throwing plate cylinder  58  and blanket cylinder  60  off impression typically requires moving form rollers out of the way. Designing form rollers to move with the plate cylinder is complicated and expensive. In the present invention, throwing plate cylinder  58  and blanket cylinder  60  off impression may be simplified because belt  66  simply takes a new path  90  around new position  84  of plate cylinder  58 , and tensioning roller  76  moves to a new position  92 . 
         [0024]    The present invention provides for a large gap G 1 , which may facilitate auto-transfer. During auto-transfer a web continues to run through a printing press while blanket cylinders of one or more printing units are thrown off from the web. While the blanket cylinders are thrown off, blanket cylinders of one or more other printing units are printing images on the web. Plates and blankets of the printing units with the thrown off blanket cylinder may be changed, while the other printing units print, minimizing press downtime. Auto-transfer requires a large gap between blanket cylinders and the web so that the web may pass by the thrown off blanket cylinders without receiving ink from the thrown off blanket cylinders. The present invention simplifies auto-transfer because belt  66  may take new path  90  via a movement of tensioning roller  76 . 
         [0025]    By constructing inkers  14 ,  54  with belts  24 ,  66 , the present invention simplifies inker setup and maintenance. Inkers may commonly have about twenty nips, each requiring setup and periodic adjustments for desired contact and tension. In the present invention, the contact between belts  24 ,  66  and adjacent rollers may be adjusted with tensioning rollers  32 ,  76 . Also, where conventional inkers may have about ten rubber rollers that may become worn and need replacement, inkers  14  and  54  each have only one comparable item, belts  24 ,  66 , respectively, that may become worn and need replacement. Since there are fewer nips to adjust and fewer items to replace, inker setup and maintenance may be thus advantageously simplified. 
         [0026]    To minimize print defects such as doubling, inkers  14  and  54  may be driven independently from plate cylinders  16  and  58 , respectively. Compliant contact over belts  24 ,  66  may further help isolate plate cylinders  16 ,  58  from torsional disturbances in inkers  14 ,  54 . 
         [0027]    Further embodiments are conceivable: ink feed systems  12 ,  52  may provide different ink feed rates across the web width, if desired; substrates  20 ,  64  may be either sheets or a web, and may be made of a variety of materials; multiple inkers may be used to print multiple color text and images; inker parameters, such as the number of rollers, the arrangement of rollers, the roller sizes, and belt length, may be varied to produce any desirable inker configuration; various ink feed systems, such as ink fountains, spray nozzles, and ink pumps, may be used; belts may be tooth-driven or friction-driven, for example; and vibrator roller lateral oscillation rate may be made independent of vibrator roller rotation rate. 
         [0028]    Driving tensioning rollers  32 ,  76  with a drive system may allow the drive system to act as a tensioning system by moving the drive system on a hydraulic driven carriage having a proper structural integrity. Driving tensioning rollers  32 ,  76  may be advantageous because of the amount of surface contact between belts  24 ,  66  and tensioning rollers  32 ,  76 , respectively, may increase the friction between belts  24 ,  66  and tensioning rollers  32 ,  76 , respectively, and deliver more positive torque without affecting print quality of respective printing units  10 ,  50 . 
         [0029]    In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.