Patent Application
20180339529
This disclosure is directed to printers and, more particularly, to media transport systems that use belts to transport print media in inkjet printers.
Inkjet printers form printed images using one or more printheads, each one of which includes an array of inkjet ejectors. A controller in the printer operates the ejectors to form printed images that often include both text and graphics and may be formed using one or more ink colors. Some inkjet printers move print media, such as paper sheets, envelopes, or any other article suitable for receiving printed images, on a belt past one or more printheads to receive the ink drops that form the printed image. Many printers that use belts to transport print media use a vacuum plenum and belts that have holes to generate a suction force through the surface of the belt. Each print medium engages a portion of the holes on the surface of the belt and the suction force holds the print medium to the surface of the belt to prevent the print media from slipping or otherwise moving relative to the surface of the belt as the belt moves through the printer. Holding each print medium in place relative to the surface of the moving belt enables the printer to control the timing of the operation of printheads to ensure that the printheads form printed images in proper locations on each print medium and ensures that the print media do not cause jams or other mechanical issues with the printer. In large-scale printer configurations, the belt often carries multiple print media simultaneously.
One problem with belts that carry print media over a vacuum plenum is that the print media do not completely cover every hole on the belt. For example, as a belt carries two or more print media, a gap between sheets of consecutive print media includes holes that are exposed to the vacuum plenum. The suction force of the vacuum plenum draws air through the exposed holes near the edges of the print media, which produces airflow and deviations in pressure in a region around the inter-copy gap. As the inter-copy gap moves past the printheads, the variations in pressure can negatively affect the meniscuses of liquid ink held within the nozzles of the inkjets in the printheads. In some instances, inkjets become inoperable when the variations in air pressure either draw ink from a nozzle in an undesirable manner or push the ink upwards into the nozzle. Either occurrence often results in an inoperable inkjet that can only be returned to service via a cleaning process that requires interruption of operations in the printer. Consequently, improvements to media transport systems that reduce or eliminate the occurrences of inoperable inkjets due to variations in air pressure within a print zone would be desirable.
In one embodiment, a media transport system for an inkjet printer that reduces air flow at inter-copy gaps between media on a belt moving over a vacuum plenum has been developed. The media transport system includes a vacuum plenum and a belt positioned over the vacuum plenum. The belt includes at least one member configured to carry print media in a process direction, a first plurality of holes formed through the at least one member in a first region that carries a first print medium to enable the vacuum plenum to apply a force to hold the first print medium against the at least one member of the belt, a second plurality of holes formed through the at least one member in a second region that carries a second print medium to enable the vacuum plenum to apply the force to hold the second print medium against the at least one member of the belt, and a plurality of slots formed through the at least one member in a third region corresponding to an inter-copy gap that is positioned between the first region and the second region, each slot in the plurality of slots being formed with a first area that is greater than a second area occupied by one hole in the first plurality of holes or the second plurality of holes.
In another embodiment, a printer including a media transport system that reduces air flow at inter-copy gaps between media on a belt moving over a vacuum plenum has been developed. The printer includes a media transport system with a vacuum plenum and a belt positioned over the vacuum plenum. The belt includes at least one member configured to carry print media in a process direction, a first plurality of holes formed through the at least one member in a first region that carries a first print medium to enable the vacuum plenum to apply a force to hold the first print medium against the at least one member of the belt, a second plurality of holes formed through the at least one member in a second region that carries a second print medium to enable the vacuum plenum to apply the force to hold the second print medium against the at least one member of the belt, and a plurality of slots formed through the at least one member in a third region corresponding to an inter-copy gap that is positioned between the first region and the second region, each slot in the plurality of slots being formed with a first area that is greater than a second area occupied by one hole in the first plurality of holes or the second plurality of holes. The printer also includes a print zone with at least one printhead positioned over the belt. The at least one printhead is configured to eject ink drops toward the first region of the belt and the second region of the belt as the belt moves past the at least one printhead in the process direction.
In another embodiment, a belt for a media transport system in an inkjet printer that reduces air flow at inter-copy gaps between media on a belt moving over a vacuum plenum has been developed. The belt includes at least one member configured to carry print media in a process direction, a first plurality of holes formed through the at least one member in a first region that carries a first print medium to enable the vacuum plenum to apply a force to hold the first print medium against the at least one member of the belt, a second plurality of holes formed through the at least one member in a second region that carries a second print medium to enable the vacuum plenum to apply the force to hold the second print medium against the at least one member of the belt, and a plurality of slots formed through the at least one member in a third region corresponding to an inter-copy gap that is positioned between the first region and the second region, each slot in the plurality of slots being formed with a first area that is greater than a second area occupied by one hole in the first plurality of holes or the second plurality of holes.
The foregoing aspects and other features of a media transport system using a belt to transport print media and an inkjet printer including the media transport system are explained in the following description, taken in connection with the accompanying drawings.
For a general understanding of the environment for the device disclosed herein as well as the details for the device, reference is made to the drawings. In the drawings, like reference numerals designate like elements.
As used herein, the word “printer” encompasses any apparatus that produces images with colorants on media, such as digital copiers, bookmaking machines, facsimile machines, multi-function machines, and the like. As used herein, the term “process direction” (P) refers to a direction of movement of a belt that carries print media past at least one printhead in a print zone. For example, a media transport system includes a belt that moves in the process direction. The belt has a surface that carries print media along the process direction past at least one printhead in a print zone. At least one printhead ejects drops of ink to form printed images on each print medium. A location that is “upstream” in the process direction relative to a component in the printer refers to a location that the print media passes prior to reaching the component, such as an upstream location that a print medium passes prior to reaching a printhead or other component in the printer. A location that is “downstream” in the process direction relative to a component in the printer refers to a location that the print media passes after reaching the component, such as a downstream location that a print medium passes after passing a printhead or other component in the printer. As used herein, the term “cross-process” direction (CP) refers to an axis that is perpendicular to the process direction along a surface of the belt and the print media on the surface of the belt.
In isolation from the use of the belt within a printer, the process direction also refers to the longitudinal axis of the belt along the circumference of the loop for an endless belt. In isolation from the use of the belt within a printer, the cross-process direction also refers to the lateral axis of the belt, which is the width of the belt between the two lateral edges in an endless belt.
As used herein, the term “belt” refers to at least one moveable member in a media transport system that has a surface configured to carry print media in the process direction through the printer. The belts described herein include openings that enable a vacuum plenum that is positioned on a bottom side of the belt to apply a vacuum force that draws air through openings that are formed in the belt. The vacuum force from the plenum holds sheets of print media, such as paper or plastic sheets, securely to the top surface of the belt. Openings in the belt that are not covered by a media sheet enable the vacuum plenum to draw air through the belt. Examples of belts include, but are not limited to, rubberized endless belts formed from at least one member that optionally include composite fabric layers, segmented belts formed from flexible or rigid members that join together to form the surface of the belt, and any other suitable belt structure.
As used herein, the term “vacuum plenum” refers to an apparatus that includes at least one chamber, a vacuum source, such as an electrical pump or fan system, and at least one opening that is configured to engage one surface of a belt in a media transport system. The vacuum source draws air through holes that are formed in the belt through the chamber and out an exhaust opening. A print medium placed on a surface of the belt opposite the surface that engages the opening to the chamber in the vacuum plenum covers a portion of the holes in the belt. The vacuum generated in the vacuum plenum applies a downward force to the print medium through the holes in the belt that are covered by the print medium.
As used herein, the terms “hole” and “slot” both refer to types of openings that are formed through at least one member in a belt. More particularly, a “hole” refers to an opening that is formed through the belt with a shape that is substantially equal in both the process direction and the cross-process direction from a center of the hole. For example, a circular shaped opening is one common example of a hole, although other geometric forms including squares, pentagons, hexagons, octagons, plus-sign crosses, and the like can form holes as well. The “slot” refers to an opening that is formed through the belt in which one axis of the opening is substantially longer than the other axis in either the process direction or the cross-process direction. An elongated rectangle with a length that runs along either the process direction axis or the cross-process direction axis of the belt is one example of a slot, although other elongated shapes including ellipses can form slots as well. Furthermore, as described in further detail below, the slots in a belt are formed with an area that is larger than the areas of the holes in the belt to enable the slots to reduce the overall variation in pressure that occurs when a vacuum plenum draws air through the slots compared to drawing air through the holes.
As used herein, the term “inter-copy gap” refers to predetermined regions of the belt that that lie between print media while the belt carries the print media in the process direction. In one configuration, an inter-copy gap of approximately 64 millimeters in length along a process direction separates adjacent media sheets on the belt, although alternative embodiments use larger or smaller inter-copy gap sizes. The inter-copy gaps repeat at regular intervals along the length of the belt corresponding to the predetermined length of a print medium (e.g., every 210 mm or 297 mm for size A4 paper depending upon the paper being arranged width-wise or length-wise, respectively, on the belt).
In
In the belt 112, both the first region 116A and the second region 116B include a plurality of holes that are formed through the at least one member in the belt 112. The holes enable the vacuum plenum to apply vacuum force to the media sheets via openings in the platen 132 and the holes. During operation of the media transport system, the first region 116A and the second region 116B both receive media sheets prior to passing one or more printheads in a print zone of an inkjet printer. For example, the hole 118A in the first region 116A applies a vacuum force to a media sheet that is placed on the surface of the belt 112 in the region 116A. Similarly, the hole 118B in the region 116B applies a vacuum force to a media sheet that is placed on the surface of the belt 112 in the second region 116B.
In the embodiment of
The belt 112 also includes inter-copy gap regions that are located between adjacent media sheets on the belt 112. In
Each of the inter-copy gaps 120A-120C in the belt 112 includes a plurality of slots, including the slots 124A, 124B, and 124C that are formed in the inter-copy gaps 120A, 120B, and 120C, respectively. Each of the slots forms an opening through at least one member of the belt 112 with an area of the slot opening being greater than the area of the opening for any of the holes that engage a print medium, such as the holes 118A or 118B. In the embodiment of
The belt configuration of
In the belt 212, the inter-copy gaps 220A-220C are regions that are formed on either side of the regions 116A and 116B along the process direction P that do not carry the print media. The inter-copy gaps 220A-220C each include a plurality of slots arranged in a two-dimensional array along the cross-process direction CP. For example, the slots 224A, 224B, and 224C, are each arranged in one of the inter-copy gaps 220A, 220B, and 220C, respectively. In the illustrative embodiment of
The vacuum plenum 108 includes a chamber that is placed in communication with the belt 312 via openings in the platen 132. The vacuum plenum 108 is further connected to the pumps 110, which are embodied as an array of electric fans. During operation, the fans of the pumps 110 draw air through the belt 312, platen 132, and emit the air from the base of the vacuum plenum 108. The pumps 110 generate a reduced level of pressure in the chamber of the vacuum plenum 108. The reduced level of pressure in the vacuum plenum 108 enables the holes the belt 312 to apply a vacuum force to media sheets that are positioned on the upper surface of the belt 312 and for the slots in the inter-copy gaps of the belt 312 to draw in air from above the upper surface of the belt 312. Alternative embodiments of the vacuum plenum 108 include a different number of pumps.
The print zone 160 includes an array of fours printhead units 164A-164D, although other embodiments include a different number of printhead units. In the printer 100, each of the printhead units 164A-164D is positioned over the upper surface of the belt 112 to enable printheads within each printhead unit to form printed images on the surfaces of print media that the belt 112 carries in the process direction P through the print zone 160. In the illustrative example of
Referring again to
It is believed that the larger areas of the slots in the inter-copy gap regions of the belts 112 and 212 produce a substantial reduction in the variations in air pressure above the belt in the print zone 160 as the inter-copy gaps in the belt move past the printhead units 164A-164D. As depicted above in
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the following claims.
