This disclosure is directed to printers and, more particularly, to media transport systems for 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 often 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 can include holes exposed to the vacuum plenum. The relative locations of gaps on the belt often change between print jobs that use print media of different sizes. The suction force of the vacuum plenum draws air through the exposed holes near the edges of the print media, which produces airflow. In regions around the printheads, the airflow can affect the paths of ink drops as the ink drops travel from the printhead to the surface of the print medium, which can reduce the accuracy of drop placement and degrade image quality, particularly near the leading and trailing edges of the print media. For example,
In one embodiment, a media transport system that reduces the negative effects of airflow through exposed holes around a workstation or print zone has been developed. The media transport system includes a vacuum plenum, a belt positioned over the vacuum plenum, a first shutter positioned between the vacuum plenum and the belt, and a first actuator configured to move the belt over the vacuum plenum in a process direction to enable the belt to carry a plurality of media in the process direction. The belt includes at least one member that forms a surface to carry media, a plurality of rows of holes formed through the at least one member to enable the vacuum plenum to draw air through the plurality of rows of holes, and a first plurality of inter-copy gaps formed in a first row of holes in the plurality of rows of holes, each inter-copy gap in the first plurality of inter-copy gaps includes no holes formed through the at least one member, and the first plurality of inter-copy gaps is arranged at a first predetermined interval along the first row of holes, the first predetermined interval corresponds to a first predetermined size of media that the belt carries in a process direction. The first shutter includes a solid member that prevents a flow of air between the vacuum plenum and a portion of the belt positioned above the first shutter, and a first aperture formed through the solid member, the first aperture being aligned with the first row of holes in the belt to enable the vacuum plenum to draw air through the first row of holes and to prevent the vacuum plenum from drawing air through the first aperture as each inter-copy gap in the plurality of inter-copy gaps moves over the first aperture.
In another embodiment, a printer with a media transport system that reduces the negative effects of airflow through exposed holes near printheads has been developed. The printer includes a media transport system, and a print zone. The media transport system includes a vacuum plenum, a belt positioned over the vacuum plenum, a first shutter positioned between the vacuum plenum and the belt, and a first actuator configured to move the belt over the vacuum plenum in a process direction to enable the belt to carry a plurality of print media in the process direction. The belt includes at least one member that forms a surface to carry print media, a plurality of rows of holes formed through the at least one member to enable the vacuum plenum to draw air through the plurality of rows of holes, and a first plurality of inter-copy gaps formed in a first row of holes in the plurality of rows of holes, each inter-copy gap in the first plurality of inter-copy gaps including no holes formed through the at least one member, and the first plurality of inter-copy gaps being arranged at a first predetermined interval along the first row of holes, the first predetermined interval corresponding to a first predetermined size of print media that the belt carries in a process direction. The first shutter includes a solid member that prevents a flow of air between the vacuum plenum and a portion of the belt positioned above the first shutter and a first aperture formed through the solid member, the first aperture being aligned with the first row of holes in the belt to enable the vacuum plenum to draw air through the first row of holes and to prevent the vacuum plenum from drawing air through the first aperture as each inter-copy gap in the plurality of inter-copy gaps moves over the first aperture. The print zone includes at least one printhead positioned over the belt in a location that is proximate to the first shutter, the printhead being configured to eject ink drops onto a surface of a print medium placed on the belt between a first inter-copy gap and a second inter-copy gap in the first plurality of inter-copy gaps where each inter-copy gap covers the first aperture of the solid member an edge of the print medium moves past the at least one printhead.
The foregoing aspects and other features of a media transport system 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 print media through the printer including through a print zone including at least one printhead. 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. The 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.
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 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 holes arranged in a plurality of rows with each row including holes that are arranged substantially parallel to the process direction and multiple rows of holes are arranged across a width of the belt in the cross-process direction. One side of the belt exposes the holes at least one opening in the vacuum plenum that is described above. On another side of the belt, the holes engage the print media that the belt carries through the printer and the vacuum force through the holes that engage the print media holds the print media in a fixed position relative to the surface of 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 “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 illustrative embodiment, an inter-copy gap of approximately 2.5 cm in length 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). As described in more detail below, the belt includes no holes in the inter-copy gap locations for a portion of the rows of holes that are formed in the belt. To accommodate multiple print media sizes using a single belt, the belt includes no holes in two or more different rows of holes at different intervals for the inter-copy gaps of different sizes of print media that the belt carries in the media transport system. Additional details about specific embodiments of the belts and the structure of the inter-copy gaps are presented below.
As used herein, the term “shutter” refers to a solid member, such as a polymer or metallic sheet, with at least one aperture formed in the solid member. The aperture is aligned with one row of holes in the plurality of rows of holes formed in the belt corresponding to an inter-copy gap for a predetermined size of print medium that the belt carries during a print job. As described in more detail below, the shutter is positioned between the belt and the opening of the vacuum plenum at a location that is proximate to a printhead in the printer to reduce or eliminate airflow that the vacuum plenum produces in the inter-copy gap regions where the print medium does not cover holes in the belt. In some embodiments, an actuator adjusts the location of the shutter along the cross-process direction to align one or more apertures in the shutter with different sets of rows in the belt. Each set of rows has a different inter-copy gap interval to accommodate a different size of print medium. By moving a shutter to different positions under the belt prior to commencing a print job, the media transport system enables a single belt to accommodate multiple print media sizes. Additionally, the media transport system optionally includes two or more shutters along the process direction.
The media transport system 104 includes the vacuum plenum 108, belt 112, belt actuator 114, two shutters 132 and 140, and a shutter actuator 148. In the overhead view of
The belt 112 includes the four rows of holes 116A-116D. The belt 112 includes two different sets of inter-copy gaps that enable the belt 112 to accept two different sizes of print media. For example, the rows of holes 116A and 116C are configured for media sheets with a process-direction dimension 122 as depicted in
As depicted in
The shutters 132 and 140 each include two apertures positioned in each shutter to align with the two corresponding rows of holes in the belt 112 for a given print medium size during a print job. For example
In the printer 100, the shutter 132 is located upstream in the cross-process direction P from the printhead 164 in the print zone 160 and the shutter 140 is located downstream from the printhead 164. While the printer 100 includes two shutters that are located on either side of the printhead 164 in the process direction P, an alternative configuration includes a single shutter on only one side of the printhead 164 or a single shutter in a location that is directly under the printhead 164. In particular, printer configurations in which the size of the inter-copy gap in the process direction P is approximately the same size or larger than the process-direction dimension of the inkjet array in one or more printheads may employ the single shutter positioned directly under the printhead.
The print zone 160 includes a single printhead 164. The printhead 164 is positioned over the surface of the belt 112 to enable the printhead 164 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. The printhead 164 includes an array of inkjets that eject drops of ink onto the surface of a print medium in the print zone 160. While
In
As mentioned above, the shutters 132 and 140 block the holes in the belt 112 in regions proximate to the printhead 164 to improve the accuracy of ink drop placement from the printhead 164 onto the surfaces of print media in the print zone 160. Each shutter, however, also includes one or more apertures to enable a portion of the holes in the belt 112 to remain in communication with the vacuum plenum 108 as a print medium passes over each shutter. The apertures enable the media transport system 104 to maintain at least partial suction on the media sheets to secure the media sheets to the surface of the belt 112 even as the media sheets pass over the shutters 132 and 140. For example, in
The various embodiments of the media transport system 104 are described with reference to the printer 100. However, those of skill in the art will recognize that the media transport system 104 can be used in a wide range of industrial settings that utilize a moving belt transport system. Various manufacturing processes benefit from reducing or eliminating unwanted airflow through a plenum in a region of the belt around a workstation, which is analogous to the print zone 160 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.
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