Patent Application
20140327724
This invention relates to an industrial grade inkjet printer for providing selective simplex (one-sided) and duplex (two sided) printing of a medium and to a method of printing therefor.
It is desirable in high speed printers to be able to print cut sheets at a rate of the order of 140 feet per minute. Such a requirement is made more difficult if there is a requirement for duplex printing. It is known in duplex inkjet printers to perform duplex printing by passing a cut sheet into a printing dock under the inkjet printhead, to print one side, to withdraw the cut sheet from the printing dock, turn the cut sheet over, transport the inverted sheet back into the printing dock under the printhead, print the other side, and then direct the duplex printed sheet to an output. The various operations, and in particular the sheet insertions and extractions, take time and detract from the throughput speed. It is desirable either to obviate or modify some of the steps in order to achieve faster duplex and simplex performance with easy selection of the desired printing mode.
According to one aspect of the invention, there is provided a printer for selective duplex and simplex printing on a medium, comprising an input zone and an output zone, a transport mechanism having a selectable first transport path for transporting a medium from the input zone to the output zone past a first print station for printing on one surface of the medium by a first inkjet printhead, the transport mechanism having a second selectable transport path including a substantial part of the first transport path for transporting a medium from the input zone to the output zone past a second print station for printing on one surface of the medium by a second inkjet printhead and then past the first print station for printing on the reverse surface of the medium by the first ink jet printhead.
Preferably the first and second transport paths include a first generally horizontal span at a first height, the first inkjet printhead being positioned to jet ink down onto the medium as it is transported in a first direction along the first generally horizontal span. The second transport path can include a second generally horizontal span at a second height, the second inkjet printhead being positioned to jet ink down onto the medium as it is transported in a second direction opposite to the first direction along the second generally horizontal span. Preferably the printer further comprises a turn unit to turn a medium between the horizontal spans. The first and second generally horizontal spans can be vertically adjacent horizontals limbs of a generally S-form path.
The printer can further include a drying unit mounted downstream of at least one of the inkjet printheads.
For printing on a sheet medium, the printer can further comprise a first diverter drivable between a first position for passing sheet media from the input zone onto the first transport path and a second position for passing sheet media from the input zone onto the second transport path and a second diverter drivable between a third position for directing sheet media transported on the first transport path towards the output zone and a fourth position for directing sheet media transported on the second transport path towards the output zone. The printer can further comprise at least one continuous belt for transporting the sheet media along at least one of the generally horizontal spans.
For printing on a web medium, the printer can further comprise a plurality of rollers positioned to guide a driven web from the input zone to the output zone on the second transport path, a subset of the plurality of rollers positioned to guide a driven web from the input zone to the output zone on the first transport path. The printer can further comprise idler rollers to support the web at the inkjet printheads.
Preferably the printer further comprises a first priming unit and a first drying unit for priming and drying one surface of a medium transported on the first transport path and for priming and drying one surface of a medium transported on the second transport path, the printer having a second priming unit and a second drying unit for priming and drying a reverse surface of a medium transported on the second transport path.
For added versatility, the printer can have first common transport elements operable to transport both sheet media and web media, second transport elements selectively operable to transport sheet media but not web media, and third transport elements selectively operable to transport web media but not sheet media.
According to another aspect of the invention, there is provided a method for selectively duplex and simplex printing onto a medium, comprising selecting one of a simplex printing mode and a duplex printing mode, when the simplex printing mode is selected, transporting a medium to be printed from an input zone to an output zone along a first transport path past a first printing station for simplex printing onto one surface of the medium by a first inkjet printhead, when the duplex printing mode is selected, transporting a medium to be printed from the input zone to the output zone along a second transport path past a second printing station for printing onto one surface of the medium by a second inkjet printhead and then past the first printing station for printing onto the reverse surface of the medium by the first inkjet printhead.
For simplicity and clarity of illustration, elements illustrated in the following figures are not drawn to common scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Advantages, features and characteristics of the present invention, as well as methods, operation and functions of related elements of structure, and the combinations of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of the specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:
Referring to
The transport paths, including the input and output zones, utilize a combination of nips, guides and belts to act on transported sheets to move them through the apparatus. The horizontal spans have respective endless conveyor belts to convey the sheets along the span. A suitable belt and associated drive and control apparatus are as described in copending U.S. patent application Ser. No. 13/368,280 (Multiple print head printing apparatus and method of operation) filed Feb. 7, 2012, the contents of which are hereby incorporated by reference in their entirety and made part of the present United States Patent Application. Such printing apparatus has a series of inkjet print heads spaced from one another in a transport direction. A continuous belt driven around a roller system is used to feed sheet media successively to the print heads so that a partial image printed by one print head is overprinted at a subsequent print head with registration of the partial images. A sheet medium is caused to become electrostatically tacked to the belt by passing the sheet past a charging device. Movement of the belt is tracked by a tracking sub-system and operation of the print heads is coordinated with the tracked belt movement to achieve precise registration of the partial images.
The electrostatic belt arrangement is particularly useful for conveying the sheet media along the upper and middle spans of the S form transport path although a simpler conveyor belt arrangement can be contemplated for the lower span. Referring in detail to
The transport mechanism includes diverters 58, 59. As shown in the detail view of
Referring back to
The transport includes a second diverter 59 which is in a reverse orientation compared with the diverter 58 and is spaced from it by a bridging span 110 having one of more sheet transfer nips for moving sheet media 12 from the diverter 58 to the diverter 59. The bridging span forms a part of the shorter transport path. The diverter 59 when in the down position receives sheet media transported to the diverter 59 along the longer transport path, and when in the up position, receives sheet media transported along the shorter transport path for simplex printing.
The transport mechanism includes 180 degree turn units 88, 89 and 90 degree turn units 86, 87. The turn units are of the form shown in copending U.S. patent application Ser. No. 13/439,909 (Registration and transport unit for a sheet feeder) filed Apr. 5, 2012, the contents of which are hereby incorporated by reference in their entirety and made part of the present United States Patent Application for all purposes. As shown in
The printer also includes a pair of priming fluid applicator units 106. The function of the units 106 is to coat sheets 12 such as cut paper sheets with a coating of fluid as the paper is transported through the units. Application of the priming fluid acts to present a layer of material on the sheet that means that subsequently jetted inks result in a higher quality image than would be the case if no primer were used. For example, the primer may increase the waterfastness of certain inks in comparison with printing onto paper without primer. Alternatively, or in addition, the primer may improve the colour gamut. The priming fluid is applied with a roller although other suitable means may be adopted. Each priming unit has a dryer 108 positioned immediately downstream of the primer applicator unit to dry the applied priming fluid before the coated sheet 12 is further manipulated.
One primer applicator unit 106 is located in the input zone 14 and is used to prime the surface of a sheet medium 12 moving from right to left through the zone 14, regardless of whether the sheet is to be printed on one side or both. The other primer applicator unit 106 is located in the downward span 84 additionally to coat the reverse side of sheets 12 that are destined to be duplex printed. Both of the primer applicator units 106 have associated dryers 108 to dry the applied primer coat. The dryer units are radiant heater dryers having a pair of twin carbon filament bulbs extending across the full width of the printing apparatus to accommodate double page width sheets.
In operating the printer, the first step that is performed is to decide whether the sheet is to be simplex printed or duplex printed. If that decision is simplex printing, the two diverters 58 are driven to their up positions. Sheet material 12 to be printed is driven from the right as shown into the input zone 14. A first of the priming fluid applicators 106 is then operated to coat the upper side of the sheet 12 with priming fluid and the dryer in the input zone is operated to dry the applied coating. The sheet 12 is then driven by nips into the diverter 58 which directs the sheet into the guide 72 which forms part of a bridging span 110, forming a part of the shorter transport path, where it is registered against a side reference member (not shown). Re-referencing of the side edge of the sheet 12 is repeated periodically as the sheet is transported through the equipment. The sheet 12 is driven by a further nip or nips associated with a bridging span to the reverse oriented diverter 59 onto the continuous belt 32 occupying the top span 26 of the S-form transport mechanism. The sheet medium 12 is electrostatically tacked to the belt 32 which then conveys the sheet 12 under an array 20 of inkjet printheads which operate in sequence to print a composite image onto the sheet 12. The image is dried at a dryer 112 which is similar to the dryer 108. The printed sheet 12 is then conveyed by further nips from the belt 32 to the output zone 16. The sheet medium 12 throughout its movement though the transport equipment is monitored by optical sensors which determine any problem caused by a paper jam and can be used to ensure that the sheet media are properly aligned.
If the decision is duplex printing, the two diverters 58, 59 are driven to their down positions. Sheet material 12 to be printed is again driven from the right as shown into the input zone 14 and the priming fluid application unit 106 and the dryer 108 associated with the input zone are operated in a similar manner as for simplex printing to prime one surface of the sheet 12. The sheet 12 is then driven into the diverter 58 which directs the sheet into the 90 degree curved guide 86. Nips associated with the curved guide drive the sheet downwardly to a reverse 90 degree curved guide 87. In between the two 90 degree curved guides 86, 87, the sheet passes through a second priming fluid applicator unit 106 and its associated dryer 108 to impart a primer coating to the unprimed surface of the sheet 12. From the lower 90 degree curved guide 87, the sheet is launched onto the lowest span 30 of the S-form transport path. At the end of the span 30, the leftward driven sheet 12 is turned though 180 degrees at a 180 degree curved guide 88 and launched onto the middle span 28 of the S-form transport path. The sheet medium 12 is electrostatically tacked to the belt 34 which then conveys the sheet 12 under an array 24 of inkjet printheads which operate in sequence to print a composite image onto one surface of the sheet 12. The image is dried at a dryer 112 similar to the dryer 108. At the end of the middle span 28, the rightwardly driven sheet is turned though a reverse 180 degrees at another curved guide 89. At the output end of the curved guide 89, the transported sheet is directed into the reverse oriented diverter 59 and onto the continuous belt 32 of the top span 26 of the S-form transport mechanism. The sheet is registered against a side reference plate at each of the curved guides 88, 89. As shown in
Referring to
In the course of a printing operation, the web 13 is conveyed from right to left as shown in
The idler rollers 114 are brought into service for duplex printing by threading the web 13 around them. In one threading technique, a leading end of the web is threaded successively around the rollers 114a to 114f. In an alternative technique, the rollers 114a to 114f are mounted on a laterally slidable carriage and a portion of the web 13 between the belts is held temporarily in a position where the carriage can be slid into place for duplex printing with the intervening web portion draped around the idler rollers 114. The web is then tensioned to tighten it around the rollers before web transportation and printing begins.
The array of rollers 114 is arranged to bring the web 13 through a transport path configured substantially the same as the sheet transport path of
In operating the printer for simplex printing, the web 13 is driven from the right as shown into the input zone 14 and is guided in a direct route between the idler rollers 114a and 114f. The first priming fluid applicator 106 at the input zone is operated to coat the upper side of the web 13 with priming fluid and its associated dryer 108 is operated to dry the applied coating. The tensioned web 13 is supported by idler rollers 42 as it is fed along the top span of the S-form transport path and under the printhead array 20. The printheads operate in sequence to print a composite image onto the web 13 and the image is dried at dryer 112.
For a duplex printing operation, once the web 13 is in place around the rollers 114, it is driven from the right into the input zone 14 and the first priming fluid application unit 106 and dryer 108 are operated to prime and dry one surface of the web 13. The web 13 is guided around roller 114a and downwardly past the second priming fluid applicator 106 and dryer 108 which are operated to prime and dry a reverse side of the web 13. The web is guided around the roller 114b and directed along the lowest span of the S-form transport path. The web is then turned though 180 degrees at the pair of rollers 114c, 114d and directed along the middle span of the S-form transport path where it is supported by idler rollers 42. The web is conveyed under the array 24 of inkjet printheads which operate in sequence to print a composite image onto one surface of the web 12. The image is dried at a lower dryer 112 similar to the dryer 108. At the end of the middle span, the rightwardly driven web is turned though a reverse 180 degrees at roller pair 114e, 114f. From the roller pair 114e, 114f, the web is directed along the top span of the S-form transport path where it is supported by idler rollers 42 as passes under the top array 20 of inkjet printheads 56 which operate in sequence to print a composite image onto the upwardly facing surface of the web. Once the image is complete, it is dried at the upper drier 112 and then directed to and through the output zone 16.
It will be appreciated that the arrangement illustrated in
Other variations and modifications will be apparent to those skilled in the art. The embodiments of the invention described and illustrated are not intended to be limiting. The principles of the invention contemplate many alternatives having advantages and properties evident in the exemplary embodiments.
