Abstract:
A fluid delivery system includes a first conveyor adapted to transport a substrate and a second conveyor disposed adjacent to the first conveyor. The second conveyor is configured to receive the substrate across a gap from the first conveyor. A fluid delivery head is disposed above the gap between the first conveyor and the second conveyor.

Description:
TECHNICAL FIELD  
       [0001]     This application relates to the field of ink jet printing.  
       BACKGROUND  
       [0002]     Ink jet printing is a non-impact method that produces droplets of ink that are deposited on a substrate such as paper or transparent film in response to an electronic digital signal. In various commercial or consumer applications, there is a general need to provide ink jet images that are printed edge-to-edge on a substrate. There is also a need for printing ink images on irregular and/or small substrates such as candy and cookies.  
         [0003]     Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. Multiple orifices or nozzles also may be used to increase imaging speed and throughput. The ink is ejected out of orifices and perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the electrically charged ink droplets are passed through an applied electric field that is controlled and switched on and off in accordance with digital data signals. Charged ink droplets are passed through a controllable electric field, which adjusts the trajectory of each droplet in order to direct it to either a gutter for ink deletion and recirculation or a specific location on a recording medium to create images. The image creation is controlled by electronic signals.  
         [0004]     In drop-on-demand systems, a droplet is ejected from an orifice directly to a position on a recording medium by pressure created by, for example, a piezoelectric device, an acoustic device, or a thermal device controlled in accordance with digital data signals. An ink droplet is not generated and ejected through the nozzles of an imaging device unless it is to be placed on the recording medium.  
       SUMMARY  
       [0005]     In one aspect, a fluid delivery system includes a first conveyor to transport a substrate, a second conveyor disposed adjacent to the first conveyor, the second conveyor being configured to receive the substrate across a gap from the first conveyor and a fluid delivery disposed above the gap between the first conveyor and the second conveyor.  
         [0006]     In an aspect, a fluid delivery system includes a first conveyor to transport a substrate, a second conveyor disposed adjacent to the first conveyor, the second conveyor being configured to receive the substrate across a gap from the first conveyor and a fluid delivery head configured to eject fluid drops on the substrate when the substrate is transported over a gap from the first conveyor to the second conveyor.  
         [0007]     In one aspect, a method for printing an ink image on a substrate includes transporting a substrate from a first conveyor across a gap to a second conveyor and ejecting ink drops from an ink jet print head to the substrate when the substrate is transported over the gap between the first conveyor and the second conveyor.  
         [0008]     Implementations of the system may include one or more of the following. A fluid delivery system includes a first conveyor adapted to transport a substrate, a second conveyor disposed adjacent to the first conveyor, wherein the second conveyor is configured to receive the substrate across a gap from the first conveyor, and a fluid delivery head disposed above the gap between the first conveyor and the second conveyor. The fluid delivery head can be configured to eject fluid drops on the substrate when the substrate is transported over the gap from the first conveyor to the second conveyor. The fluid delivery head can be configured to print a fluid pattern that is full bleed at least along one edge of the substrate. The fluid delivery system can further include a controller that can control the fluid drop ejection from the fluid delivery head. The fluid delivery system can further include a first motor operatively coupled to the first conveyor and controlled by the controller, said first motor being configured to control the first conveyor. The fluid delivery system can further include a second motor operatively coupled to the second conveyor and controlled by the controller, said second motor being configured to control the second conveyor. The first conveyor can further include one or more of a drive roller, a passive roller, a conveyance belt, and a motor. The second conveyor can further include one or more of a drive roller, a passive roller, a conveyance belt, and a motor. The fluid delivery system can further include one or more sensors configured to detect substrate and its position and to generate a substrate location signal that can be used to control the ejection of the fluid drops. The fluid delivery system can further include one or more sensors configured to detect the orientation of the substrate and to generate a substrate orientation signal that can be used to control the ejection of the fluid drops. The fluid delivery system can further include a fluid collector disposed below the gap between the first conveyor and the second conveyor for collecting overspray fluid drops ejected by the fluid delivery head.  
         [0009]     The fluid delivery system can further include a fluid absorbent material over the fluid collector for collecting overspray fluid drops ejected by the fluid delivery head. The fluid absorbing material can be replaceable. The fluid delivery system can further include a fluid reservoir configured to supply fluid to the fluid delivery head. The fluid delivery device is an ink jet print head.  
         [0010]     Embodiments may include one or more of the following advantages. The disclosed ink jet system provides ink jet printing in a gap between two sequentially positioned conveyors and the collection of the overspray inks below the gap. The disclosed ink jet system is capable of full bleed printing without contamination of the substrate by the overspray inks. The disclosed ink jet system is capable of printing ink images on substrates without the need of pre-aligning the substrates before printing. Furthermore, the system provides effective methods and mechanisms for cleaning the overspray inks.  
         [0011]     The details of one or more embodiments are set forth in the accompanying drawing and in the description below. Other features, objects, and advantages of the invention will become apparent from the description and drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  illustrates an ink jet printing system capable of full-bleed printing. 
     
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  shows an ink jet printing system  10  including a first conveyor  100  and a second conveyor  200 . The second conveyor  200  is positioned downstream to the first conveyor  100  and is separated from the first conveyor  100  by a gap  99 . An ink jet print head  20  is disposed over the gap  99  between the first conveyor  100  and the second conveyor  200 . The ink jet print head  20  may include one or more ink nozzles through which ink drops  140  can be ejected. The ink jet printing system  10  further includes a controller unit  30  and an ink reservoir  40  for supplying ink to the ink jet print head  20 . A substrate  50  can be sequentially transported by the first conveyor  100  and the second conveyor  200 . The ink jet printing system  10  can also include one or more sensors  150  for detecting the location and/or the orientation of the substrate  50  to produce substrate position signals. The substrate position signals are sent to the control unit  30  for controlling the ejection of the ink drops from the ink jet print head  20 .  
         [0014]     The first conveyor  100  includes a conveyor belt  170 , a drive roller  120  for driving the conveyor belt  170 , a motor  110  that can drive the drive roller  120  under the control of the control unit  30 , and a passive roller  130 . The substrate  50  is carried and transported by the conveyor belt  170  toward the second conveyor  200  that is down stream to the first conveyor  100 . The second conveyor  200  includes a conveyor belt  270 , a drive roller  220  for driving the conveyor belt  270 , a motor  210  that can drive the drive roller  220  under the control of the control unit  30 , and a passive roller  230 .  
         [0015]     The substrate  50  is moved under the ink jet print head  20  and then received by the second conveyor  200  that can continue to transport the substrate  50  at the same speed. The location of the substrate  50  is detected by the sensor  150  when it moves over the gap  99  between the first conveyor  100  and the second conveyor  200 . The sensor  150  produces substrate location signals that can be received by the control unit  30 . The control unit  30  provides image data and other digital data to the ink jet print head  20  and controls the ink jet print head  20  to eject ink drops  140  onto the substrate  50 .  
         [0016]     In an embodiment, the ink jet print head  29  can print edge-to-edge across the substrate  50 . The accurate sensing of the lead and the rear edges of the substrate  50  by the sensor  150  allows the placement of ink drops  140  from the lead edge of the substrate  50 , thus forming a full bleed ink pattern on the substrate  50 . Along a substrate edge to be printed full bleed, the control unit  30  prepares the image data and controls the ink jet print head  20  such that it prints slightly over the edge so that a full ink image is produced without a blank margin along the edge. In the present application, the term “full bleed” is used to describe an image that extends up to one or more edges of a substrate. The term “full bleed” can also describe a printed image without borders along one or more edges of an substrate.  
         [0017]     In an embodiment, the ink jet print head  20  is transported by a print head transport system along a fast scan direction while the substrate  50  is transported by the first conveyor  100  and the second conveyor  200  along a slow scan direction. The ink jet print head  20  can dispose ink drops on the substrate  50  from one side edge to another in each printing swath along the fast scan direction. The detection of the lead and rear edges of the substrate  50  allows the full bleed printing of ink image along all four edges of the substrate  50 .  
         [0018]     In an embodiment, one or more sensors  150  can detect the orientation of the substrate  50  in addition to substrate position. Substrate orientation signals subsequently produced are sent to the control unit  30 . In response, the image data are processed such that the ink pattern to be disposed will be automatically adjusted according to the specific orientation of the substrate  50 . One advantage of the orientation detection and image printing adjustment is that the substrate  50  does not need to be aligned in any particular orientation on the first conveyor  100 . Another advantage is that irregular shaped substrates having one or more non-straight edges can be printed full bleed using the disclosed ink jet printing system  10 .  
         [0019]     For example, as a rectangular-shaped substrate moves along the first conveyor  100 , the substrate may pass under the print head  20  at a 45° angle. One or more sensors  150  can detect that the rectangular-shaped substrate is traveling at a 45° angle. Once the sensors  150  detect the orientation of the rectangular-shaped, a substrate orientation signal is sent to the control unit  30 . Then, the image data is processed such that the ink pattern will be adjusted to a 45° angle. In another embodiment, one or more sensors send signals to a control unit. The control unit detects the orientation of the substrate and adjusts the image data to the orientation of the substrate.  
         [0020]     The ink drops ejected from the print head  20  beyond the substrate edges can be referred to as overspray ink. As shown in  FIG. 1 , the overspray ink is collected by an ink collector  90  disposed below the gap  99 . An ink absorbing material  95  can be placed over the ink collector  90  to absorb the overspray ink and to prevent ink accumulation. The ink absorbing material  95  can be replaced or disposed from time to time to keep the system clean. The absorbent material  95  can include man made or natural materials. The absorbent material  95  can also be tailored to be most effective in absorbing the specific types of inks used for each batch of substrates: for example, aqueous or solvent types of inks. The ink collector  90  can be fluidly connected with an waste ink reservoir  97  through an ink line  98  to allow excess ink collected in the ink collector  90  to over flow into the waste ink reservoir  97 . Effective removal of waste inks allows the ink jet printing system  10  long periods of continuous printing operation without maintenance. Furthermore, different colored ink fluids may each include an ink collector under the corresponding ink jet print head and below the gap  99 . The waste ink can be recycled for future printing operations.  
         [0021]     Ink types compatible with the ink jet printing system described include water-based inks, solvent-based inks, and hot melt inks. The colorants in the inks can comprise dyes or pigments. Furthermore, the ink jet printing system is also compatible with delivering other fluids such as polymer solutions, gel solutions, solutions containing particles, low molecular-weight molecules, which may or may not include any colorant, flavors, nutrients, biological fluids, or electronic fluids.  
         [0022]     An advantage of the disclosed system and methods is that full-bleed ink jet printing in the gap between two sequentially positioned conveyors and the collection of the overspray inks below the gap assures that the overspray inks are not accumulated on the conveyor belts  170  and  270 . The underside and the edges of the substrate  50  are therefore not contaminated by the overspray inks.