Abstract:
A print system including a vacuum blower configured to create both a vacuum pressure and exhaust, a vacuum chamber configured to distribute the vacuum pressure created by the vacuum blower, a transport belt configured to pass in close proximity to the vacuum chamber, the transport belt having a plurality of holes, and a pneumatic cleaning device configured to direct the exhaust created by the vacuum blower through one or more holes of the transport belt in close proximity to the pneumatic cleaning device. The pneumatic cleaning device includes an upper cleaning head comprising a one or more vents configured to direct air through holes in a transport belt; and a lower cleaning body. The lower cleaning body includes a muffler, a removable collection area configured to collect debris in the exhaust, and a filter configured to collect in the exhaust.

Description:
BACKGROUND 
       [0001]    The present invention relates to pneumatic cleaning systems. More specifically, the present invention relates to pneumatic belt hole cleaning systems for vacuum transport systems. 
         [0002]    Direct-to-media printing systems typically include a printable media hold-down system. As a printable medium passes on a transport surface under a print head, the hold-down system attempts to maintain a critical print head to printable media gap as well as to prevent contact between the printable medium and the print head. Contact between printable media and the print head may result in contamination of the printable media as well as fibers from printable media becoming lodged in ink nozzles in the print head. Over time, a substantial number of fibers could become lodged in the nozzles causing the print head to clog. A clogged print head can damage printable media by printing incorrectly, waste ink, and cause significant downtime as the clogged head must be cleaned and/or replaced. 
         [0003]    Several hold-down systems are prevalent in modern direct-to-media printing systems. One example is a vacuum/chamber transport system. In this system, a series of small holes are placed in the transport element surface, and air is sucked through the holes, away from the print head (or print head array). As the printable medium passes under the print head (or print head array), a vacuum is created under the printable medium, thereby holding the printable medium against the transport surface. 
         [0004]      FIG. 1  illustrates an exemplary vacuum transport system  100 . A printable medium  102  is transported past a print head array  104  on a transport belt  106 . The transport belt  106  may be made of a highly porous material or a nonporous material with a number of holes for allowing air flow through the transport belt. These holes may be small in size (e.g., 1.0 mm in diameter) and spaced evenly apart on the transport belt  106 . A vacuum blower  108  creates a vacuum pressure that is directed through a vacuum chamber  110  to the transport belt  106 . The vacuum pressure pulls air through the transport belt  106  toward the vacuum blower  108  (as indicated by arrow A). The vacuum chamber  110  acts as a diffuser, spreading the vacuum pressure equally over the surface of the transport belt  106 . As the printable medium  102  advances, the vacuum pressure pulls the printable medium against the transport belt  106 , thereby protecting the print head array  104  from contact with the printable medium as well as providing a necessary tacking force to transport the printable medium with the transport belt through a print zone. 
         [0005]    Vacuum hold-down systems have inherent problems, however. One problem is clogged holes in the transport belt. Fibers from the printable media, dust and debris from the ink such as stray ink drops may become lodged in the individual holes in the transport belt, thereby reducing or completely blocking the flow of air through that hole. Over time, enough holes may become clogged in the transport belt to reduce the overall vacuum pressure created by the vacuum hold-down system to a level where a printable medium may contact an individual print head (or multiple print heads in a print head array). Additionally, when a hole is clogged, dirt may be transferred to the side of the printable medium touching the vacuum belt resulting in imperfections on the printable medium. 
         [0006]    One approach to eliminate this problem is to periodically remove the transport belt from the system in which it is installed and clean the holes in the transport belt. However, this approach results in significant downtime for the print system, as printing must be halted in order to remove the belt. 
       SUMMARY 
       [0007]    Before the present methods are described, it is to be understood that this invention is not limited to the particular systems, methodologies or protocols described, as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present disclosure which will be limited only by the appended claims. 
         [0008]    It must be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to a “printable medium” is a reference to one or more printable media and equivalents thereof known to those skilled in the art, and so forth. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used herein, the term “comprising” means “including, but not limited to.” 
         [0009]    In one general respect, the embodiments disclose a print system. The print system includes a vacuum blower configured to create both a vacuum pressure and exhaust, a vacuum chamber configured to distribute the vacuum pressure created by the vacuum blower, a transport belt configured to pass in close proximity to the vacuum chamber, the transport belt having a plurality of holes, and a pneumatic cleaning device configured to direct the exhaust created by the vacuum blower through one or more holes of the transport belt in close proximity to the pneumatic cleaning device. 
         [0010]    In another general respect, the embodiments disclose a print system. The print system includes a vacuum blower configured to create both a vacuum pressure and exhaust, a vacuum chamber configured to distribute the vacuum pressure created by the vacuum blower, a transport belt configured to pass in close proximity to the vacuum chamber and configured to transport printable media past a print head array, the transport belt having a plurality of holes configured to direct the vacuum pressure created by the vacuum blower from the vacuum chamber to the printable media, and a pneumatic cleaning device configured to direct the exhaust created by the vacuum blower through one or more holes of the transport belt passing in close proximity to the pneumatic cleaning device. 
         [0011]    In another general respect, the embodiments disclose a pneumatic cleaning device. The pneumatic cleaning device includes an upper cleaning head comprising a one or more vents configured to direct air through holes in a transport belt; and a lower cleaning body. The lower cleaning body includes a muffler, a collection area configured to collect debris in the exhaust, and a filter configured to collect debris in the exhaust. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Aspects, features, benefits and advantages of the present invention will be apparent with regard to the following description and accompanying drawings, of which: 
           [0013]      FIG. 1  illustrates an exemplary printable-media vacuum hold down system; 
           [0014]      FIG. 2A  illustrates a vacuum transport system having an integrated pneumatic hole cleaning device; 
           [0015]      FIG. 2B  illustrates a cutaway view of the transport system of  FIG. 1 ; and 
           [0016]      FIG. 3  illustrates a more detailed view of the collection chamber of the pneumatic hole cleaning device of  FIG. 2A . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    For purposes of the discussion below, a “printable medium” refers to a physical sheet of paper, corrugated board, plastic, film and/or other suitable substrate for printing images thereon. 
         [0018]    An “exhaust duct” refers to an enclosure suitable for directing air flow between spaces in a structure or a device. 
         [0019]    A “vacuum blower” refers to a device capable of creating one or more of a vacuum pressure and exhaust by directing air flow from one area to another. 
         [0020]      FIG. 2A  illustrates an exemplary embodiment of a vacuum transport system  200  having a pneumatic hole cleaning device for removing debris from holes in a transport belt. Similar to the vacuum transport system  100  in  FIG. 1  discussed above, the vacuum transport system  200  may be designed to transport a printable medium  202  past a print head array  204  on a transport belt  206  in a process direction shown by arrow D. The transport belt  206  may be a strip of fabric, film, elastomer or similar material that loops around, for example, three rollers, roller  207 A, roller  207 B and roller  207 C. At least one of the rollers (e.g., the roller  207 A) may be configured to rotate in a specific direction, e.g., clockwise, thereby providing a driving force that causes the transport belt  206  to move. The transport belt  206  may be made of a highly porous material or a nonporous material with a number of holes for allowing air flow through the transport belt. 
         [0021]      FIG. 2B  shows a more detailed cutaway view of vacuum transport system  200  including holes  218  of vacuum belt  206 . The holes  218  may be small in size (e.g., from approximately 0.5 to approximately 2.5 mm in diameter) and spaced evenly apart on the transport belt  206  (e.g., from approximately 5 mm to approximately 15 mm apart) to enable the creation of a uniform vacuum pressure across a portion of the transport belt traveling in close proximity to a vacuum chamber  210 . 
         [0022]    Referring again to  FIG. 2A , a vacuum blower  208  creates a vacuum pressure that is directed through the vacuum chamber  210  to the transport belt  206 . The vacuum pressure pulls air through the transport belt  206  toward the vacuum blower  208  (as indicated by arrow A). The vacuum chamber  210  acts as a diffuser, spreading the vacuum pressure equally over the surface of the portion of the transport belt  206  in close proximity to the vacuum chamber. The vacuum chamber  210  may be positioned below the transport belt  206  between roller  207 A and  207 B. As the printable medium  202  advances along the transport belt  206  between roller  207 A and  207 B, the vacuum pressure distributed along the transport belt by the vacuum chamber  210  pulls the printable medium against the transport belt, thereby protecting the print head array  204  from contacting the printable medium. 
         [0023]    The vacuum blower  208  may also include an exhaust duct  212  that directs air (“exhaust”) away from the vacuum blower (as indicated by arrow B). The exhaust may be directed along the exhaust duct  212  toward a pneumatic cleaning device  214 . The pneumatic cleaning device  214  may direct the exhaust from the vacuum blower  208  through the transport belt  206  in an opposite direction of the normal airflow through the holes (as indicated by arrow C) in order to clear debris that may be lodged in the holes of the transport belt. The pneumatic cleaning device  214  may be positioned such that a portion of the transport belt  206  remote from the print head array  204  is cleaned between roller  207 B and roller  207 C. The exhaust duct  212  may further include a valve  216  configured to selectively direct the exhaust towards either the pneumatic cleaning device  214  or additional exhaust ducts connected to the exhaust duct  212 . Individual components of the pneumatic cleaning device  214  and additional information relating to the integration of the pneumatic cleaning device into vacuum transport system  200  is discussed in greater detail below in the discussion of  FIG. 3 . 
         [0024]    Depending on the volume of air that passes through the pneumatic cleaning device  214 , backpressure may be created in the vacuum blower  208 , resulting in a reduced vacuum pressure exerted on the transport belt  206  by the vacuum chamber  210 . Accordingly, the valve  216  may be controlled to eliminate this backpressure when a printable medium is passing over the vacuum chamber  210 . For example, when the printable medium  202  is passing over the vacuum chamber  210 , the valve  216  may be in a first position, closing off the pneumatic cleaning device  214 , thereby directing all exhaust through the exhaust duct  212 . Once the printable medium  202  is past the vacuum chamber  210 , the valve  216  may be moved to a second position by any suitable electromechanical position control system, directing the exhaust through the pneumatic cleaning device  214 . Depending on the distance between discrete printable media, various portions of the transport belt  206  may be cleaned. 
         [0025]    If the printable media are positioned close together such that cleaning between individual printable media is substantially not performed, a cleaning cycle may be used during a non-printing belt maintenance cycle in which the transport belt  206  is run continuously for several complete loops of the belt, allowing for each hole in the transport belt to be cleaned a plurality of times. A belt maintenance or cleaning cycle may be run after a predetermined period of time (e.g., after 2 hours of printing time), at startup and/or at shutdown of the printing device. 
         [0026]      FIG. 3  illustrates a close-up view of the pneumatic cleaning device  214  and the individual components that may be included in one exemplary embodiment of the pneumatic cleaning device. The pneumatic cleaning device  214  may include two main components, an upper cleaning head  302  and a lower cleaning body  304 . The transport belt  206  may pass between these two components. The upper cleaning head  302  may attach to the exhaust duct  212  near the valve  216  such that when the valve is in the second position, any exhaust passing through the exhaust duct is directed into the pneumatic cleaning device  214 . The upper cleaning head  302  may be designed in various geometric shapes depending on the application or the amount of space available. For example, the upper cleaning head  302  may flare out radially from the exhaust duct  212  such that a larger surface area of the transport belt  206  passes under the upper cleaning head. The upper cleaning head  302  may be positioned in close proximity to the transport belt  206  (e.g., less than approximately 1 mm from the surface of the transport belt) and may include appropriate peripheral seals such that the amount of exhaust lost around the edges of the upper cleaning head is minimized. The upper cleaning head  302  may include one or more vents  303  for directing exhaust directly at the transport belt  206  in a direction substantially perpendicular to the surface of the transport belt. The exhaust may then pass through the individual holes of the transport belt  206 , dislodging debris from the holes. The exhaust and any dislodged debris may then pass into the lower chamber  304  positioned on the exterior of the transport belt  206 . 
         [0027]    Once the exhaust passes into the lower chamber  304 , the exhaust may pass through one or more mufflers  306 . The one or more mufflers  306  may be designed such that they reduce or otherwise eliminate noise created by the exhaust as it passes through the pneumatic cleaning device  214  and through holes in the transport belt  206 . The one or more mufflers  306  may be geometrically designed to include a resonance chamber specifically sized and positioned to produce a destructive interference. The destructive interference may be equal in frequency, but opposite in phase, to sound waves produced by the exhaust. As the exhaust passes through the resonance chamber, the sound waves created by the exhaust combine with the destructive interference to reduce or eliminate the sound of the exhaust. Similarly, the one or more mufflers  306  may include a sound dampening material such as acoustical foam. The acoustical foam may absorb sound waves produced by the exhaust to further reduce or eliminate the noise produced by the exhaust. 
         [0028]    The exhaust and debris may pass into a collection area  308  where large pieces of debris are collected. The exhaust and smaller pieces of debris may then pass through a filter  310 . Smaller pieces of debris may be collected by the filter  310 , and the exhaust may exit the pneumatic cleaning device  214  through one or more exhaust vents  312 . 
         [0029]    The lower chamber  304  may be detachably mounted to a support structure such that the lower chamber may be removed and cleaned. Any debris collected in the collection area  308  may be emptied. Similarly, the filter  310  may be removed and cleaned and/or replaced. 
         [0030]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.