Abstract:
An ink jet printing system includes an ink jet print head configured to deliver ink drops to a substrate, a support member having a plurality of protrusions configured to carry the substrate by being in contact with the lower surface of the substrate, and a substrate conveying mechanism configured to cause relative movement between the ink jet print head and the support member.

Description:
TECHNICAL FIELD 
     This application relates to the field of ink jet printing. 
     BACKGROUND 
     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 an ink substrate. There is also a need for printing ink images on irregular and/or small ink substrates such as candy and cookies. 
     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. 
     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 
     In one aspect, an ink jet printing system having an ink jet print head configured to deliver ink drops to a substrate, a support member having a plurality of protrusions configured to carry the substrate by being in contact with the lower surface of the substrate, and a substrate conveying mechanism configured to cause relative movement between the ink jet print head and the support member. In another aspect, a fluid delivery system having a fluid delivery head configured to deliver fluid drops to a substrate, and a support member having a plurality of protrusions configured to carry the substrate by being in contact with the lower surface of the substrate. 
     In yet another aspect, a method for printing an ink image on a substrate including providing a support member having a plurality of protrusions over the surface of the support member, placing a substrate over the plurality of protrusions, and disposing ink drops from an ink jet print head on the substrate. 
     Implementations of the system may include one or more of the following features. The fluid delivery system can further include a substrate conveying mechanism configured to cause relative movement between the fluid delivery head and the support member. The fluid delivery system can have a controller configured to control the fluid delivery head to deliver fluid to the substrate and to control the substrate conveying mechanism to cause relative movement between the fluid delivery head and the support member. At least a portion of the support member can include a substantially flat surface. The protrusions can be so configured that the substrate carried by the protrusions is substantially parallel to the surface of the support member. The protrusions can include tapered ends adapted to carry the substrate. The support member can include one or more conveying belts. The support member can include one or more continuous conveying belts. The ink jet printing system can further include a print head transport mechanism capable of moving the ink jet print head relative to the substrate. The ink jet printing system can further include one or more sensors configured to detect the location or the orientation of the ink substrate. The ink jet print head can deliver ink drops to form an ink image on the substrate. The ink image can be printed full bleed along at least one edge of the substrate. The substrate can include at least one irregular-shaped edge. The ink jet printing system can further include an ink absorbing material over the surface of the support member. 
     Embodiments may include one or more of the following advantages. The disclosed fluid delivery system can be capable of full bleed printing while reducing or preventing the contamination of the substrate by the overspray fluids. The disclosed fluid delivery system can be capable of printing ink images on small and irregular shaped substrates without the need or with greater tolerance for pre-aligning the substrates before printing. Fluid delivery systems can print full bleed over and to the edges of the irregular shaped substrates. Furthermore, the system can provide effective methods and mechanisms for cleaning the overspray fluids. 
     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 
         FIG. 1  illustrates an ink jet printing system having an ink jet print head and an ink substrate transport system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an ink jet printing system  10  including an ink jet print head  20 , controller unit  30  that provides image data and other digital data to the ink jet print head  20 , and ink reservoir  40  for supplying ink to the ink jet print head  20 . 
     An ink substrate  50  is transported by an ink substrate transport system  100 . The ink substrate transport system  100  includes at least one conveyor belt  70 , rollers  120  and  130  for driving the conveyor belt  70 , and a motor  110  that can drive the roller  120  under the control of the control unit  30 . A plurality of protrusions  80  extend from a surface of the conveyer belt  70 . The substrate  50  is placed over and supported by the protrusions  80 . The lower surface of the substrate  50  is in contact with the tip of the protrusions  80 . The substrate  50  is carried by the protrusions  80  to positions under the ink jet print head  20  to receive ink drops  140  ejected by the ink jet print head  20 . Substrates compatible with the present invention include paper or man-made image substrates for displaying images including opaque, translucent, or transparent materials. The substrates can also include foods such as cookies, candies, and cakes. The substrates can also comprise plastics, ceramics, stone, metallic substrate, wood, and fabrics. 
     The protrusions  80  can be provided by a plurality of protruding objects that are joined to the conveyor belt  70 . The protruding objects can be fixed to the conveyer belt, or formed integrally with the conveyer belt. The protrusions  80  can be made of rubber materials molded onto the conveyor belt  70 . The protrusions  80  can also be solid materials plugged or screwed onto the conveyor belt  70 . 
     The protrusions  80  are typically sparsely distributed to limit contact area to the lower surface of the substrate  50 . The density and the size of the protrusions can be scaled to the size of the substrates  50 . For example, for 8″×10″ sized substrates, the protrusions  80  can be distributed one inch apart in a two-dimensional array. The width of the protrusions  80  can be narrower than ⅛ or 1/16 of an inch. The protrusions  80  can comprise undersides near the surface of the conveyor belt  70  and outer ends pointing outward from the conveyor belt  70 . The outer ends can be tapered and narrower than the underside of the protrusions. The tapered outer ends of the protrusions  80  further limit the contact area between the protrusions  80  and the substrate  50 . 
     In one arrangement, the conveyor belt has a plurality of protrusions. The tips of the protrusions form a plane on which the substrate rests. The substrate travels along the protrusions of the conveyor belt as the conveyor belt moves underneath the printhead. The plane of the protrusions on which the substrate rests can be parallel to the conveyor belt. Alternatively, the conveyor belt  70  can be mounted on a cylindrically shaped rotating drum. The conveyor belt  70  can be continuous as shown in  FIG. 1 , or tensioned between a feeding roll and a receiving roll. 
     In another embodiment, the protrusions  80  for carrying substrate  50  may be fixed over a non-moving support member. The ink jet print head is transported by a print head transport system. The ink jet print head scans the substrate  50  during the printing of the ink image on the ink substrate  50 . 
     One or more sensors  150  can detect the position and orientation of the ink substrate  50 . The sensors  150  can include a plurality of photo diodes disposed at pre-determined locations, or image sensors that can detect images of at least a portion of the substrate  50 . Each of the photo diodes is illuminated by a light beam over a distance. The arrival of the substrate  50  interrupts the light beam and thus producing an electric signal. The correlations between the locations and timings of the light-beam interruption can be used to compute the substrate&#39;s position and the orientation. Similarly, the image captured by the image sensors can be processed by a pattern-recognition software to determine locations and orientations of the substrate  50 . The detection of the positions of the ink substrate  50  can be triggered by the edges of the ink substrate  50 . The detection of the position of the ink substrate can facilitate the printing of the ink pattern on the ink substrate  50  from the leading edge and around the edges of the ink substrate  50 . The ink overspray outside of the edges of the substrate  50  can be captured by the conveyor belt without accumulation near the undersides of the substrates  50 . Ink contamination on the ink substrates is a known issue in substrate transport mechanisms without the protrusions  80 , especially for full bleed ink jet printing. 
     The limited contact area between the protrusions  80  and the lower surface of the ink substrate  50  significantly reduces the probability of ink contamination at the lower surface of the ink substrate  50 . Furthermore, the ink substrate  50  is preferably positioned such that none of the tips of the protrusions  80  are not in contact with the edges of the substrate  50 . 
     The ink jet printing system is particularly useful for printing small and/or irregular shaped ink substrates such as goldfish, cookies, and candy. The term irregular shape refers to a substrate that has at least one edge that is not straight. The positions and the orientations of the small and/or irregular shaped ink substrates can be detected by one or more sensors  150 . The ink pattern printed can be full bleed along at least one edge of the substrate  50 . The overspray can be captured by the conveyor belt  70  without contaminating the undersides of the ink substrates because of the space separating the undersides of the ink substrate  50  and the conveyor belt  70 . The ink pattern can also be automatically adjusted according to the specific orientation of the substrate  50 . The ink jet printing system therefore enables the ink jet printing on irregular shaped ink substrates without the need for aligning the substrates  50  on the conveyor belt  70 . 
     The conveyor belt  70  and the plurality of protrusions  80  are preferably cleaned regularly by wiping, blotting, washing, etc. after printing one or more batches of ink substrates  50 . The ink substrate transport system  100  can further include absorbent material  90  near the underside of the protrusions  80  over the conveyor belt  70 . The ink absorbing materials can include foam, gel, and paper based materials. Preferably, the absorbent material  90  is replaceable or disposable to keep ink substrate transport  100  clean. The absorbent material  90  can include man made or natural materials. The absorbent material  90  can also be tailored to be most effective in absorbing the specific types of inks used for each batch of ink substrates: for example, aqueous, solvent types of inks. 
     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 dye or pigment. Furthermore, the ink jet printing system disclosed 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.