SYSTEMS AND METHODS FOR POSITIONING PRINTHEADS OF A PRINTING APPARATUS

Systems and methods for printing on a polymeric film web are disclosed in which first and second adjacent printhead holders slidably are disposed on at least one rail and a projection extends from the first printhead holder toward the second printhead holder. A linear actuator is operated to cause the printhead holders to move between a first position in which the projection contacts the second printhead holder and a second position in which the projection is not in contact with the second printhead holder and the first and second printhead holders are separated by predetermined distances.

FIELD OF DISCLOSURE

The present subject matter disclosed herein relates to printing apparatus, and more particularly, to a printing apparatus that comprises systems and methods for positioning printheads of the printing apparatus.

BACKGROUND

High speed printing systems have been developed for printing on a substrate, such as a web of heat-shrinkable polymeric film. Such a material typically exhibits both elasticity and plasticity characteristics that depend upon one or more applied influences, such as force, heat, chemicals, electromagnetic radiation, etc. Materials deposited on the web by an imaging unit of the printing system are typically dried before additional material is deposited by a subsequent imaging unit. Some webs, such as a heat-shrinkable polymeric film, begin to shrink, deform, or otherwise become damaged if heated beyond a critical temperature. Drying of one or more material(s) deposited on such webs must be monitored and controlled so that sufficient heat is applied to dry the material deposited thereon without raising the temperature of the web beyond the critical temperature.

SUMMARY

According to one aspect, a system for printing on a polymeric film web includes at least one rail, a linear actuator, first and second adjacent printhead holders slidably disposed on the at least one rail, and a projection extending from the first printhead holder toward the second printhead holder. Operating the linear actuator causes the printhead holders to move between a first position in which the projection contacts the second printhead holder and a second position in which the projection is not in contact with the second printhead holder and the first and second printhead holders are separated by predetermined distances.

According to another aspect, a method for printing on a polymeric film web includes disposing first and second adjacent printhead holders slidably on at least one rail and operating a linear actuator to move the first and second printhead holders between a first position in which a projection extending from the first printhead holder contacts the second printhead holder and a second position in which the projection is not in contact with the second printhead holder and the first and second printhead holders are separated by predetermined distances.

According to a further aspect, a system for printing on a clear polymeric film web at a particular resolution includes a web transport, a first printhead, and a second printhead. The web transport transports the web along a process direction. The first printhead has a first nozzle plate having a first nozzle and a first side edge, wherein the first nozzle plate is free of nozzles between the first nozzle and the first side edge. The second printhead has a second nozzle plate that faces the web and has a second side edge and a second nozzle, wherein the second nozzle plate is free of nozzles between the second nozzle and the second side edge. In addition, the second side edge is parallel and proximate the first side edge. The first nozzle and the second nozzle are separated along a width direction perpendicular to the process direction by one nozzle pitch determined by the particular resolution and the first side edge and the second side edge are separated in the width direction by a distance greater than one nozzle pitch.

Other aspects and advantages will become apparent upon consideration of the following detailed description and the attached drawings wherein like numerals designate like structures throughout the specification.

DETAILED DESCRIPTION

A flexible substrate22in the form of a web, of, e.g., thermoplastic polymer material, is passed through one or more printing modules and receives ink, which is dried to obtain a printed web that may be further processed to form printed individual units, such as bags. The bags may be adapted to receive one or more articles therein. More particularly,FIGS.8and9illustrate a global controller110operable to control various elements as described hereinafter andFIGS.1-7illustrate an embodiment of a module200responsive to the global controller110, and, optionally, other devices, that prints aqueous substances on the flexible substrate22. (It may be noted thatFIGS.1-7are illustrated with certain tubing and fluid conduits omitted therefrom for the sake of clarity). The print module200includes one or more printing units201each comprising one or more ink jet printheads202, (seen in detail inFIG.5), with associated printhead controllers203. In the illustrated embodiment, each of four controllers203a-203dis associated with and operates one of four printheads202a-202d, respectively. The print module200further includes ink supply apparatus, such as one or more ink supply units205that receive ink from a main ink reservoir205ashown inFIGS.8and9, a dryer system204comprising one or more dryers (best seen inFIG.6), and a substrate transport apparatus212that controls the continuous movement of the substrate22at a throughput speed of, for example, at least 500 feet per minute. The substrate may instead be transported at a faster or slower throughput speed, e.g., 1000 feet per minute, as desired. The global controller110is responsive to one or more sensors and controls the substrate transport apparatus212, the ink supply unit(s)205, the printheads202via the controllers203, and the dryer system204. The global controller110may also control additional elements and may be implemented by one or more suitably programmed computer-based devices, each comprising, e.g., a desktop or laptop computer, a device using one or more application specific integrated circuits (ASIC's) and/or field-programmable gate arrays (FPGA's), a tablet, a smartphone, etc. and/or combinations thereof. The global controller110may be unitary or may be distributed across one or more networks. As seen inFIG.9, the global controller110is coupled to local and/or networked interfaces, such as a keyboard, a mouse, a display, a touchscreen, a local area network (LAN), a wide area network (WAN) such as the Internet, etc. The global controller110is responsive to commands supplied thereto by a user via the local and/or networked interfaces.

In addition to the foregoing, the print module200includes one or more structural elements that provide support for various conduits and other elements and enclosures that provide spaces to house various elements, as necessary and/or desirable.

As seen specifically inFIG.6, the dryer system204comprises first, second, and third sets of dryers220,222, and224, respectively. The dryer sets200,222, and224include dryers220a-220dand222a-222dand224a-224j, respectively, (FIG.6) successively arranged in the FIGS. in sequence of substrate movement. Some or all of the dryers220a-220d,222a-222d, and/or224a-224jmay comprise one or more dryer components, such as heaters and/or blowers, or may simply comprise passive conduits or radiators, and may receive dryer air from inlet conduit sets225a-225c(FIG.1) and may exhaust air through exhaust conduit sets226a-226c(FIG.2). The dryer system204further comprises first and second rotatable drums227and228disposed opposite the sets222and224, respectively. The drums227,228control substrate tension. Further, rollers230a-230g, some or all of which may comprise driven or idler rollers, are arranged as seen inFIG.6in successive manner in order of substrate movement through the dryer system204.

The dryers are controlled to dry the ink applied to the substrate22in a fashion to minimize deformation of the substrate as much as possible.

The printing unit201is disposed at a print station250accessible by an operator. As seen inFIG.6, the print station250includes one or more idler or driven rollers230d-230fsuccessively arranged in the FIG. in order of substrate movement that transport the substrate through the printing unit201opposite the printheads202, which are operated to deposit aqueous ink onto a single side22aof the substrate22so as to effectuate simplex printing.

FIG.7illustrates an embodiment in which two of the print modules200shown inFIG.6are disposed in a frame270that allows room for one or two operators to control the modules. (It may be noted that the frame270may form a part of or be associated with one or both of the modules or may be separate from both modules. Also, the printheads202and associated controllers are not shown inFIG.7and certain reference numbers for elements visible in bothFIGS.6and7are not shown inFIG.7for clarity.) More specifically, first and second modules200a,200b, each identical to the module200, are disposed in spaced relationship in the frame270to form a printing system271. As should be evident fromFIG.7, the modules200a,200bprint on the substrate22in serial fashion. The frame270includes one or more idler and/or driven rollers272a,272bthat transport the substrate22through the frame270and between the modules200a,200b. In the illustrated embodiment, the rollers272aand272bare successively arranged inFIG.7in the direction of substrate movement. Thus, as seen inFIG.7and also referring toFIG.6, the substrate enters the module200aand passes over/about the rollers230a-230cof the module200a, and thereafter passes over the rollers230d-230fin the print station250of the module200a. In the process of traveling from the roller230dto the roller230f, the printheads202deposit aqueous ink on the side22aof the substrate. The ink that is deposited may be any individual “color(s)” or combination(s) thereof, including C (cyan), M (magenta), Y (yellow), K (key, i.e., black), O (olive), V (violet), G (green), S (a spot color), white, a clear or other primer, UV (ultraviolet), a magnetic ink, etc. In an embodiment, the module200aprints a clear primer and/or a white panel and other printed content on successive portions of the substrate22at 1200 dpi or any other resolution.

Following application of ink, the substrate22traverses the rollers230g-230iof the module200aand passes the first set of dryers220of such module. The printed side22aof the substrate22is presented toward a first stage of the dryer system204comprising the dryers220a-220d, which are operated as pinning devices and initiate the drying process. As seen inFIG.6, the substrate22travels to the drum227and thereafter to the drum228via the roller230j, and the substrate22is then guided by the rollers230k-230nand out of the module220a. As should be evident, the side22ais sequentially presented to second and third stages of the dryer system204comprising the dryers222a-222dand224a-224k, respectively, to complete the drying process.

As shown inFIG.7, the substrate continues over the rollers272aand272bto the module200bat which the side22aof the substrate22receives further printed content as described above in connection with the module200a. The printed content on the side22ais dried as described above by a dryer unit204of the second module200b. The printed substrate may be transported out of the frame270for further handling, printing, processing, and/or storage, as necessary or desirable.

In an embodiment, the module200bofFIG.7prints up to four “colors” (as noted above) on the side22aof the flexible substrate22. Thus, for example, the module200bmay print, for example, C, M, Y, and/or K at a resolution of 1200 dpi or any other resolution in register with the successive portions of the substrate22that are printed by the module200a. In a further example, the module200amay print primary process colors C, M, Y, K at any resolution on successive portions of the substrate22and the module200bmay print secondary process colors O, V, G, and an optional spot color S in register with and atop and/or in combination with the primary process colors C, M, Y, K on the same side22aof the substrate22. Alternatively, in such an embodiment, it may be advantageous and/or desirable that both of the modules200a,200bprint primary and/or secondary process colors or any other same or different “color(s)” either at the same resolution or different resolutions, in-register or out-of-register, as necessary or desirable.

If more “colors” and/or different resolutions are to be printed, additional printheads and associated printhead controllers and ink supplies can be added to the module(s)200a,200b. Alternatively, a turn bar other substrate inversion device (not shown) may be provided downstream of the module200bofFIG.7and one or two or more additional modules identical to the module200could be provided downstream of the turn bar or other substrate inversion device to permit duplex mode printing in four or eight or more “colors” on a side22bof the substrate22.

In addition to the foregoing, the module200includes one or more structural elements that provide support for various conduits and other elements and enclosures that provide spaces to house various elements, as necessary and/or desirable.

Referring toFIGS.10and11, in one embodiment, each printhead500(which may be the printhead202described above or another printhead) disposed in a printhead holder502of the printing unit201of the print module200includes a printhead housing504and an ink chamber506. The ink chamber506includes one or more ink supply ports508that may be coupled to a source of ink (not shown) via a corresponding ink supply line (not shown).

The printhead500includes a bottom portion510having a bottom face512. The printhead500is disposed in the printhead holder502such that the bottom face512faces the substrate22. The bottom portion510(and thus the bottom face512) is defined by a first side edge516, a second side edge518, a front edge520, and a rear edge522. In addition, the bottom portion510includes a nozzle plate524having a plurality of nozzles526disposed between a first side edge528and a second side edge530of the nozzle plate526. During printing, ink in the ink chamber506is ejected from one or more of the plurality of nozzles526disposed in the nozzle plate524as the substrate22is transported past such plurality of nozzles526.

In some embodiments, the first side edge516and the second side edge518of the bottom face512are substantially parallel and the front edge520and the rear edge522of the bottom face512are substantially parallel.

In some embodiments, the first side edge516of the bottom face512comprises a first side edge portion532a, the first side edge528of the nozzle plate524, and a second side edge portion532b, all of which are substantially collinear. Similarly, the second side edge518of the bottom face512comprises a first side edge portion534a, the second side edge R126of the nozzle plate524, and a second side edge portion534b, all of which are also collinear.

In some cases, the first side edge516, the second side edge518, the front edge,520, and the rear edge522of the bottom face512define a perimeter514of the bottom face512. In some embodiments, such perimeter514is a parallelogram with the first side edge516forming oblique angles with the front and rear edges520, R118and the second side edge518also forming oblique angles with the front and rear edges520,522. It should be apparent to one who has ordinary skill in the art that the perimeter514may have a different shape including, for example, a different polygonal shape (square, rectangle, hexagon, etc.) or even a shape having one or more non-linear segment(s).

FIG.12shows one embodiment of the print module200that includes a printing unit201comprising a plurality of printheads500each of which is configured to deposit a particular fluid (e.g., a primer, a particular color of ink, a coating material, and the like) through the plurality of nozzles526onto the substrate22as the substrate22is moved along the process direction538.

The printheads500that comprise the printing unit201are secured to one or more printhead holders502. Specifically, one or more of the printheads500that comprise the printing unit201are secured to each printhead holder502. As shown inFIG.12, for example, printheads500athrough500dare secured to printhead holder502a, printheads500ethrough500hare secured to printhead holder502b, and so on. The printheads500that comprise the printing unit201, and the printhead holders502to which such printheads500are secured, are disposed such that the plurality of nozzles526(seeFIG.11) of the printheads500extend along the web width direction536.

Referring also toFIG.13, in one embodiment, the printheads500are disposed such that the front edges520of the printheads disposed in each holder502are offset relative to one another in the process direction538. Thus, as illustrated inFIG.13, the printheads500athrough500edisposed in the printhead holder502aare offset relative to one another, the printheads500fthrough500idisposed in the printhead holder502bare offset relative to one another, and so on. Because side edges516,518of adjacent printheads500disposed in each printhead holder502are not parallel to the process direction538, offsetting the printheads500in this manner forms a gap540along the width direction536between adjacent printheads500without affecting the distance along the web width direction536between adjacent nozzles of the plurality of nozzles526of adjacent printheads500, respectively. Such gap540prevents excess drops of fluid ejected by such printheads500from entering and drying between the sidewalls of adjacent printheads500, prevents debris from becoming lodged between such sidewalls, allows cleaning fluid to enter the gap540, dislodges and washes away any ink and/or debris in such, and facilitates removal from the holder502of one printhead500disposed in such holder502without knocking or otherwise contacting an adjacent printhead500disposed in such holder502.

In some embodiments, each printhead holder502is also offset along the process direction538relative to another holder502adjacent thereto. As a result, the printhead500disposed in one printhead holder502(e.g., the printhead500ddisposed in the printhead holder502a) and an adjacent printhead500disposed in another printhead holder502(e.g., the printhead500edisposed in the printhead holder502b) are also offset relative to one another along the process direction538. Offsetting the printhead holders in this manner forms a gap542along the width direction between the first printhead500d,500h,5001,500p, or500tdisposed in the first printhead holder502a,502b,502c,502d, or502e, respectively, and the second printhead500e,500f,500i,500q, or500udisposed in the second printhead holder502b,502c,502d,502e, or502f, respectively, wherein the first printhead and the second printhead are adjacent to one another and disposed in adjacent printhead holders502. In addition to the reasons for having the gap540between adjacent printheads500of the same printhead holder502described above, having the gap542between adjacent printhead holders502also facilitates removal of the printhead holder502from the print module200without risk of a printhead500disposed in such printhead holder502accidently contacting or knocking against another printhead500disposed in an adjacent printhead holder502.

In some embodiments, the printhead holders502are secured to a mounting bar543(FIG.12). Stand-offs and mounts (not shown) are disposed between and secured to the printhead holders502and the mounting bar543.

FIG.14further illustrates the relationship of first and second adjacent printheads544,546(identical to the printheads500described above) and first and second nozzles548,550thereof, respectively, wherein the first and second nozzles548,550are adjacent to one another (i.e., the first and second nozzles548and550are operable to deposit adjacent drops of fluid onto the substrate22along web width direction536). The first printhead544represents any of the printheads500athrough500wand the second printhead546represents any of the printheads500bthrough500xadjacent to the printheads500athrough500w, respectively, shown inFIG.12. Note that the arrangement of the first and second printheads544,546and the first and second nozzles548,550are diagrammatically shown for illustrative purposes

It should be apparent that because the first nozzle548of the first printhead544is adjacent to the second nozzle550of the second printhead546, there is no other nozzle of the first printhead544between the first nozzle548and the first side edge516of the first printhead544. Similarly, there is no other nozzle of the second printhead546between the second nozzle550and the second side edge518of the second printhead546. Further, to ensure no discontinuities or other unwanted artifacts are apparent between first and second adjacent portions of an image printed by the first and second printheads544,546, respectively, a distance552along the web width between the first nozzle548and the second nozzle550should be substantially identical to the nozzle pitch (i.e., distance between nozzles that deposit adjacent drops of another fluid onto the substrate22) of the plurality of nozzles526(seeFIG.11) of the first and second printheads544,546. That is, for example, if the first and second printheads544,546are 1200 dot-per-inch printheads, then the nozzle pitch of the plurality of nozzles526of such first and second printheads544,546is approximately 0.00083 inch (0.021 mm). In such cases, the distance552between the first and second nozzles548,550of the first and second printheads544,546should also be approximately 0.00083 inch (0.021 mm). It should be apparent to one who has ordinary skill in the art that such nozzle pitch varies in accordance with the resolution of the first and second printheads544,546that are being used.

As illustrated inFIG.14, offsetting the first and second printheads544,546along the process direction538by a distance554increases the space between the first side edge516of the bottom face512of the of the first printhead544and the second side edge518of the bottom face512of the second printhead546. As the offset along the process direction538is increased, a distance556along the width direction (i.e., the gap540or542discussed above) increases correspondingly. If the offset along the process direction538is sufficient, then the distance556exceeds the distance552between the first and second adjacent nozzles548and550. That is, the distance556exceeds the nozzle pitch of the plurality of526of the first and second printheads544,546. If the first and second printheads print at different resolutions, the distance556along the web width direction536exceeds the distance552(i.e., nozzle pitch) between the first and second nozzles548and550along the web width direction536.

In some embodiments, the adjacent first and second printheads544,546that are in the same printhead holder502are offset along the process direction538so that the distance554between a rear edge522of the bottom face512of the first printhead544and the rear edge522of bottom face512the second printhead546is between approximately 0.0846 inches and 0.1034 inches, and in an embodiment, approximately 0.094 inches (2.38 mm). Further, the adjacent first and second printheads544,546that are in adjacent printhead holders502are offset along the process direction538so that the distance554between the rear edge522of the bottom face512of the first printhead544of one holder502and the rear edge522of bottom face512of the second printhead546in an adjacent holder502preferably is between approximately 0.3096 inches and approximately 0.3784 inches, and, in an embodiment, preferably approximately 0.344 inches (8.74 mm).

In some embodiments, the gap540between adjacent printheads500in the same holder502results in a spacing between adjacent sidewalls516,518of the printheads500when measured along a direction perpendicular to such sidewalls of between approximately 0.0342 inches and approximately 0.0418, and, in an embodiment, approximately 0.038 inches.

In some embodiments, the gap542between adjacent printheads500of adjacent holders502results in a spacing between adjacent sidewalls516,518of the adjacent printheads500disposed in adjacent holders502when measured along a direction perpendicular to such sidewalls between approximately 0.0954 inches and approximately 0.1166, and, in an embodiment, preferably approximately 0.106 inches.

It should be apparent to one who has ordinary skill in the art that increasing or reducing the distance554between the rear edges522of the first and second printheads544,546increases or reduces the distance556between adjacent sidewalls516,518of the first and second printheads544,546, respectively. For example, in some embodiments, the distance554between the rear edge522of the bottom face512of the first printhead544and the rear edge522of bottom face512the second printhead546is preferably between approximately 0.0594 inches and 0.0726 inches, and in one such embodiment approximately 0.066 inches. In such embodiments, the gap540,542between the first and second printheads544,546is such that the distance556between adjacent sidewalls516,518of the first and second printheads544,546, respectively, along the web width direction is between approximately 0.0297 inches and 0.0363 inches and in one such embodiment is approximately 0.033 inches.

In some embodiments, the printhead500disposed in the printing unit201is a model Samba G3L and/or Samba G5L printhead sold by Fujifilm Dimatix, Inc., of Santa Clara, California. It should be apparent to one who has ordinary skill in the art that a different printhead that still has a first side edge516and a second side edge518that are not parallel to the process direction538may be used in the printing unit201. Further, the printing unit201may configured to use other printheads wherein such other printheads that are adjacent to one another have bottom faces that overlap in the process direction while print produced by the adjacent printheads is stitched.

FIGS.15through19show another embodiment600of the print module200. Referring toFIGS.15-19, the print module600comprises a first printing unit602having a first plurality of printhead holders604athrough604xthat are slidably mounted along a first side606of a central block608. A printhead500may be secured to a corresponding one of the first plurality of printhead holders604. For clarity,FIG.15shows printheads500disposed in printhead holders604aand604xonly and printhead holders604bthrough604ware shown free of printheads500.

The printhead holders604athrough202xand the printheads500secured thereto are disposed such that the plurality of nozzles526(seeFIG.11) of the printheads500extends along the web width direction536. Thus, each of the printheads500that are secured in the printhead holders604is operable to deposit a first particular fluid (e.g., a primer, a particular color of ink, a coating material, and the like) through the plurality of nozzles526thereof onto the substrate22as such substrate is moved along the process direction538.

In some embodiments, the print module600comprises a second printing unit610comprising a second plurality of printhead holders612that are slidably mounted on a second side614of the central block608, and a printhead500may be secured to each one of the second plurality of printhead holders612. In such embodiments, the printhead holders612are disposed such that the plurality of nozzles526of the printheads500disposed in the printhead holders612extend along the web width direction536. Each of the printheads500disposed in the printhead holders612is operable to deposit a second fluid through the printhead nozzles526thereof onto the substrate22as the substrate is moved continuously along the process direction538. Although the first and second fluids are typically different, it should be apparent to one of ordinary skill in the art that the printheads500disposed in the first plurality of printhead holders604and the printheads disposed in the second plurality of printhead holders612may be operable to deposit the same fluid (e.g., for overprinting or other applications apparent to one who has ordinary skill in the art). It should be apparent the print module200may be configured with as many printhead holders612(and thus printheads500) as necessary so that the nozzles526of the printheads500disposed in such printhead holders612span substrate22along the width direction536to print an image having a desired width.

Each printhead holder612comprises a front plate616and a rear plate618secured to one another. The front plate616includes a mounting apparatus620to which a printhead500may be secured.

A first linear bearing block622(SeeFIG.18) is secured to the rear plate618of each printhead holder612. The first linear bearing block622of each printhead holder612is slidably disposed on a first linear bearing rail624that is secured to the central block608. In some embodiments, a second linear bearing block626is secured to the rear plate618of each printhead holder612and the second linear bearing block626is slidably disposed on a second linear bearing rail628, also secured to the central block608.

Similarly, each of the second plurality of printhead holders604is disposed on the central block608by the corresponding first linear bearing block218adisposed on the first linear bearing rail624and (optionally) the second linear bearing block626disposed on the second linear bearing rail628.

In some embodiments, one or more spacing and alignment members629may be disposed between the front and rear plates616,618to adjust the distance between the front plate616and the first side606of the central block608along the process direction538and/or the angle between the front plate616and the first side606of the central block608. It should be apparent to one of ordinary skill in the art that adjusting the distance and/or angle between the front plate616of a printhead holder604and first side606of the central block608also adjusts the distance and/or angle between the front plate616and first side606and between the printhead500disposed in such printhead holder604and the first side606. The distance and/or angle between the each of the second plurality of printhead holders612and the second side614of the central block608may be adjusted in a similar fashion.

As shown inFIG.15, the first printing unit602includes the printhead holders604athrough604xsecured to the first side606of the central block608and distributed along the web width direction536. In this embodiment, the printhead holders604aand604xare terminal printhead holders and the printhead holders604bthrough604wcomprise intermediate printhead holders disposed therebetween.

In some embodiments, an extensible arm630of a linear actuator632is secured to the terminal printhead holder604a. In some embodiments, the terminal printhead holder604xis secured to an extensible arm630of another linear actuator632a, as shown inFIGS.15and16.

In other embodiments, the terminal printhead holder604xis secured to a stationary block634secured to the first side606of the central block608(as shown inFIGS.19A and19B). The stationary block634provides an anchor that prevents movement of the terminal printhead holder604xalong the first bearing rail624.

Similarly, one of the terminal printhead holders612secured to the second side614of the central block608is secured an extensible arm636of another linear actuator636and another one of the terminal printhead holders612secured to the second side614of the central block608is secured to another stationary block (not shown).

As described in greater detail below, the printhead holders604of the print module200are movable between an operational position (i.e., printing position) and a maintenance position. When in the operational position, the printhead holders604are arranged so there is a predetermined gap between adjacent bottom faces512of printheads500disposed in the printhead holders604that are adjacent to one another along the web width direction536. Such gap depends on the resolution of the adjacent first and second printheads500disposed in the printhead holders604. In particular, the predetermined gap is selected such that a distance between a first nozzle of the plurality of nozzles526of the first printhead500disposed in a first printhead holder604that is adjacent a second nozzle of the plurality of nozzles526of the second printhead500disposed in an adjacent second printhead holder604, respectively, is in accordance with the nozzle pitch of the plurality of nozzles of the first and second printheads500. In some embodiments, the predetermined gap between the sidewalls516,518of adjacent printheads is between approximately 0.0117 inches and 0.0143 inches, and preferably approximately 0.013 inches.

When the first printhead holders604are moved from the operational position to the maintenance position, each one of the printhead holders604is moved a predetermined amount along the first and second linear bearing rails624,628in a direction parallel to the web width direction536such that such printhead holder604(and the printhead500disposed therein) is spaced apart sufficiently from an adjacent printhead holder604(and the printhead500disposed therein). Such spacing facilitates cleaning between the printheads500to remove ink and or debris trapped between adjacent printheads500or printhead holders604and removal of the printhead500disposed in the printhead holder604without contacting an adjacent printhead holder604. In some embodiments, such predetermined gap between the sidewalls516,518of adjacent printheads, when in the maintenance position, is between approximately 0.054 inches and 0.066 inches, and preferably approximately 0.066 inches.

FIGS.19A and19Bare simplified schematic drawings of the printing unit602that illustrate movement the printhead holders604between the operational position and the maintenance position. For purposes of clarity,FIGS.19A and19Bshow the printing unit602having only four printhead holders604athrough604dand certain components of the printing unit201of the print module200discussed above are not shownFIGS.19A and19B. The movement between the operational position and the maintenance position with respect to the four printhead holders604athrough604dis equally applicable to a print module200having more than four holders and to print holders612(not shown inFIGS.19A and19B) of the print module200.

Referring toFIGS.19A and19B, the printhead holders604aand604dcomprise first and second terminal printhead holders and the printhead holders604band604ccomprise intermediary printhead holders disposed between such terminal printhead holders. As described above, the first terminal printhead holder604ais secured to an extensible arm630of the linear actuator632. The second terminal printhead holder is secured to the stationary block or anchor634or an extensible arm630aof another linear actuator632a.

Position projections or slide limiters640athrough640cextend from the second terminal printhead holder604dand the intermediate printhead holders604b,604c, respectively. Each projection640athrough640cextends from first sidewalls642bthrough642dof the rear plates618band618dof the printhead holders604bthrough604d, respectively. Further, each projection640athrough640cextends toward a second sidewall644athrough644cof the adjacent printhead holders604athrough604c, respectively. As described in detail below, the lengths of projections640that extend into the space between printhead holders604determines the spacing between printheads500when the printhead holders604are in the operational position. In one embodiment, the projections640are micrometer screws screwed into the sidewalls642, a wedge disposed on the sidewalls642, or other types of spacers disposed on the sidewalls642apparent to one who has ordinary skill in the art. It should be apparent to one of ordinary skill in the art that other types of projections may be used.

When the plurality of printhead holders604is in the operational (i.e., printing) position (shown inFIG.19A), the extensible arm630of the linear actuator632(and, if used, the extensible arm630aof the linear actuator632a) is in an extended position. In addition, adjacent printhead holders604are positioned such that a sidewall646of each projection640that extends from the first sidewall642of the rear plate618of each first printhead holder604abuts the second sidewall644of a second printhead holder604adjacent to the first printhead holder604. As a result, a space between the sidewalls642,644between adjacent holders is substantially identical to the length of the projection640that extends into such space from the first sidewall642.

In addition, first posts648athrough648care disposed proximate the second sidewalls644athrough644cof the rear plates618athrough618cof the printhead holders202athrough604c, respectively. Second posts650athrough650care disposed proximate the first sidewalls642bthrough642dof the rear plates618bthrough618dof the printhead holders202bthrough604c, respectively. Thus, the first terminal printhead holder604ahas a first post648a, the second terminal printhead holder604dhas a second post650c, and each intermediate printhead holder604b,604chas both a first post648and a second post650. Each first post648disposed on the first printhead holder604and the second post650disposed on the second printhead holder604adjacent thereto are substantially collinear with respect to one another. Further, a link or a loop652couples the first post648on the first printhead holder604and the second post650on the second printhead holder604adjacent thereto.

When the printhead holders604are in the maintenance position (shown inFIG.19B), the extensible arm630of the linear actuator632(and the extensible is in a retracted position and adjacent printhead holders604are positioned such that first and second distal interior ends654,656of each link652contact the first and second posts648,650of adjacent printhead holders604surrounded by such link652. Thus, a space between sidewalls642,644of the rear plates618of adjacent printhead holders604is substantially identical to a length of the opening of the links652(i.e., the distance between the first and second distal interior ends654,656of such links652).

As described above, the global controller110operates the printhead transport apparatus114, in response to operator commands, to move the printhead holders604from the operational position to the maintenance position and from the maintenance position to the operational position. In one embodiment, the printhead transport apparatus114comprises a printhead transport controller658that receives operator commands received by the global controller110, and in response operates the linear actuator632(and the linear632a, if appropriate) as described below.

FIG.20is a flow chart700that shows the processing undertaken by the printhead transport controller658(FIGS.19A,19B) of the global controller110. Referring also toFIG.9, at a block702, the printhead transport controller658waits until a command is received from the operator via the global controller110. At a block704, the printhead transport controller658determines if the command is a directive to move the printhead holders604into the operational position and, if so, the printhead transport controller658proceeds to a block706, otherwise the printhead transport658controller proceeds to a block708.

At the block706, the printhead transport controller658actuates the linear actuator632to extend the arm630. In those embodiments in which the terminal printhead604xis coupled to the extendable arm630aof the linear actuator632a, the printhead transport controller658also actuates the linear actuator632a. Doing so forces the first printhead holder604a(and604a) coupled to the arm630(and arm630a) and the intermediate printhead holders604b,604ccloser together. The printhead transport controller658actuates the linear actuator632(and linear actuator632a) to extend the arm630(and the arm630a) a predetermined distance necessary for all of the sidewalls646of the projections640disposed on the first sidewalls642of the rear plate618dof the second terminal printhead holder604dand the intermediate printhead holders604b,604cto contact and abut the first sidewalls642of the intermediate printhead holders604b,604cand the first terminal printhead holder604a, respectively.

After the block706, the printhead transport controller658proceeds to the block702to await another command.

At the block708, the printhead transport controller658determines if the command received at the block702is a directive to move to the maintenance position. If so, the printhead transport controller658proceeds to a block710, otherwise the printhead transport controller658proceeds to a block712.

At the block710, the printhead transport controller658operates the linear actuator632to retract the arm630. In those embodiments in which the terminal printhead holder604xis coupled to the arm630aof the linear actuator632a, the printhead transport controller658also operates the linear actuator632ato retract the arm630a. Doing so pulls first terminal printhead holder604aand the intermediate printhead holders604b,604ctoward the linear actuator632(the linear actuator632a, if appropriate). The printhead transport controller658operates the linear actuator632(and632a) to cause the arm630(and630a) to retract a predetermined amount necessary for the first and second distal interior ends654,656of all the links652to contact the first and second posts648,650surrounded by such links. In those embodiments in which the second terminal printhead holder604dis anchored to the block634and cannot move, the amount of movement of the first terminal printhead holder604dand the intermediate printhead holders is limited by the distance between the first and second distal interior ends654,656of the links652. Similarly, in those embodiments in which the second terminal printhead holder604xis coupled to the linear actuator632a, movement of the first and second terminal holders604aand604x, and the intermediate printhead holders therebetween is limited by the first and second distal interior ends654,656of the links652. Thereafter, the printhead transport controller658proceeds to the block702to await another command.

At the block712, the printhead transport controller658determines if the command received at the block702is a directive to begin shutdown of the print module200. If so, at a block714, the printhead transport controller658operates the linear actuator632to move the print module200to the maintenance position (or another predetermined position between the operational and maintenance positions) and exits. Otherwise, the printhead transport controller658returns to the block702to await another command.

In some embodiments, the printhead transport controller658, at the blocks706and710, checks whether the arm630(and arm630a) is (are) already in the extended or retracted state, respectively, and if so, does not further extend or retract the arm(s). Similarly, at the block714, the printhead transport controller658checks the position of the arm630(and arm630a) to determine whether to retract, extend, or maintain the position thereof to move the printing unit600into the maintenance or other predetermined other position.

Although the foregoing describes moving the printhead holders604of the printing unit602between the operational and maintenance positions, it should be apparent to one who has ordinary skill in the art that the printhead holder612of the printing unit602may be moved between the operational and maintenance positions in a substantially identical manner. Further, althoughFIGS.19A and19Bshow two intermediate printhead holder604between two terminal printhead holders604, it should be apparent to one of ordinary skill in the art that the printing unit602may comprise more or fewer intermediate printhead holders604disposed between two terminal printhead holder604and that such terminal and more or fewer printhead holders may be moved between the operational and maintenance positions as described above.

FIGS.21and22show another embodiment800of the print module200that is functionally similar to embodiment600described above. Like the embodiment600, the embodiment800includes substantially identical first and second print units802a,802b, disposed on opposite sides of the central bar608. Each print unit802includes terminal printhead holders804aand804h, intermediate printhead holders804bthrough804gdisposed between the terminal printhead holders804a,804h, and a printhead500disposed in each printhead holder804.

First and second transport blocks806,808are fastened to sidewalls810,812of the terminal printhead holders804a,804h, respectively. A stop block814is also fastened to the sidewall810. In particular, the stop block814has a base portion816, first and second side portions818,820extending downward from the base portion816. The base portion816and the side portions818,820combine to form an inverted u-shape. In addition, an extension portion822extends from the second side portion820and is fastened to the sidewall810. In some embodiments, the extension portion822is substantially parallel to the base portion816.

The print unit802further includes first and second linear actuators (such as low friction air cylinders)824,826having extension arms825,827, respectively, coupled to the first and second transport blocks806,808, respectively. In some embodiments, the extension arms825,827comprise a threaded portion that threads into a corresponding threaded portion of the transport blocks806,808, respectively.

Referring also toFIG.22, each intermediate printhead holder804b-804gincludes a first spacer block828a-828f, respectively. In addition, the terminal printhead holder804hthat is distal from the stop block814and to which the second transport block808is secured also includes a first spacer block828g. The terminal printhead holder804adoes not include a first spacer block828. Instead, the extension portion822of the stop block814is disposed in the space that would otherwise be occupied by a first spacer block828and the extension portion822is secured to the terminal printhead holder804a.

Similar to the printhead holders604and projections640described above (seeFIGS.15-19B), each printhead holder804includes a projection830that is secured to and extends outwardly from a sidewall832of a second spacer block836secured to the printhead holder804.

In addition, the second spacer block836includes a cavity840(FIG.21B) into which an extension element842of the first spacer block828is disposed. The cavity840is defined and bounded on one side by a sidewall844.

The printhead transport controller658(seeFIGS.19and20) operates the first and second linear actuators824,826to move the printhead holders804of the print unit802between print and maintenance positions.

In particular, to move the printhead holders804from the print position to the maintenance position, the printhead transport controller658operates the first and second linear actuators824,826(FIG.21) simultaneously to retract the extension arms825,827thereof to move the first and second transport blocks806,808(and thus the printhead holders804) away from one another until the first and second transport blocks806,808contact first and second mechanical stops854,856, respectively. The first mechanical stop854is disposed between the transport block806and the first linear actuator824and the second mechanical stop856disposed between the second transport block808and the second linear actuator826.

In addition, as the terminal printhead holder804ais moved toward the first mechanical stop854because of the retraction of the extension arm827, the sidewall844that defines the cavity840of the second spacer block836acontacts a sidewall846of the extension element842of the first spacer block828a(secured to the intermediate printhead holder804b) thereby urges the intermediate printhead holder804bto also move toward the first mechanical stop854.

Similarly, as retraction of the extension arm827causes the terminal printhead holder804hsecured to the second transport block808to move toward the second mechanical stop856, the sidewall844of the second spacer block836gcontacts the sidewall846of the extension element842of the first spacer block828hof the terminal printhead holder804h, and thereby urges the printhead holder804gto move toward the second mechanical stop856. In this manner, movement of the terminal printhead holders804a,804htoward the first and second mechanical stops854,856, respectively, causes intermediate printhead holders804b-804gto become spaced apart. After the printhead holders804have been moved in this manner, the print unit802is in the maintenance position.

The distance adjacent print holders804are moved is determined by the space between the sidewalls844and846of the adjacent printhead holders804when the print unit802is in the print position802(i.e., when the projection830of one printhead holder804contacts the sidewall834of the printhead holder804adjacent thereto).

It should be apparent to one who has ordinary skill in the art, that instead of using interaction of the sidewalls844of the second spacer blocks836and the sidewalls846of the extension elements842to set the amount of space between the printhead holders804when the print unit802is in the maintenance position, the printhead holders804may be adapted to be coupled using the links or loops652(seeFIGS.19A,19B) described above to control the space therebetween when the print unit802is in the maintenance position.

The printhead holders804may be separated sufficiently when the print unit802is in the maintenance position so that a vacuum device, an air ejection device, cleaning fluid flushing device, and the like may be used to remove any ink and other debris deposited on the sidewalls of the printhead holders804and/or printheads500. Further, having the print unit802in the maintenance position facilities removal and/or replacement of a printhead holder804and/or printhead500without such printhead holder804or printhead500contacting and thus possible damaging an adjacent printhead holder804or printhead500.

In addition, in some embodiments, the positions of the first and second mechanical stops854,856and the dimensions of the cavity840in the second spacer block836and the extension element842of the first spacer block828are selected so that when the print unit802is in the maintenance position, the printhead holders804are separated such that each printhead holder804and the printhead500disposed therein is aligned with a corresponding cleaning device (not shown) that may be operated to clean the bottom face512and/or sidewalls of the printhead holder804and/or the printhead500. Such cleaning device may include one or more wiper(s), one or more fluid ejection device(s), one or more vacuum device(s), a trough and/or a drain to capture purged ink and/or ejected fluid, and the like. In one embodiment, the separation between printhead holders804when the print unit802is in the maintenance position is approximately 0.065 inches. That is, the distance between a sidewall848of the second spacer block836and a sidewall850of an adjacent second spacer block836and that is proximate the sidewall848is approximately 0.065 inches.

In one embodiment, the first mechanical stop854includes a cylindrical head or bumper858fastened to one end of a screw860, the screw860is journaled through and fastened to a block862, and the block862is fastened to the central block608of the print unit802.

Similarly, the second mechanical stop856includes a cylindrical head or bumper866fastened to one end of a screw868that is journaled through and fastened to a block870, and the block870is fastened to the central block608. In one embodiment, the bumpers858,866have a large (e.g., approximately 0.75 inch) diameter that absorbs mechanical energy and thus prevents shock to the printheads500or the printhead holders804when the first and second transport blocks806,808contact the bumpers858,866, respectively.

To move the print unit602from the maintenance position to the print position, the printhead transport controller658operates the first and second linear actuators824,826to extend the extension arms825,827thereof to urge the first and second transport blocks806,808toward one another and thereby move the printhead holders804of the print unit802toward one another. The first and second transport blocks806,808are pushed in this manner until the projections830-830gof printhead holders804a-804gcontact sidewalls834a-834gof the first spacer blocks828a-828gof the printhead holders804b-804h, respectively.

Further, when the printhead holders804are in the print position, an inside wall872(FIG.21) of the first side portion818of the stop block814contacts a third mechanical stop874. Such contact between the inside wall872and the third mechanical stop874prevents further movement of the transport blocks806,808(and thus the printhead holders804) away from the first linear actuator824. The printhead transport controller causes additional movement of the printhead holders804toward one another is caused by operating the second linear actuator826to extend the extension arm827and thereby urge the printhead holders804away from the second linear actuator826and toward the first linear actuator824. Thus, when in the print unit802is in the print position, the terminal printhead holder804ais at a predetermined distance from the third mechanical stop874and the remaining printhead holders804b-804hare at a predetermined distance from the terminal printhead holder804a(and one another) as set by how much the projection830extends from the sidewall832of each second spacer block836.

In some embodiments, the first and second linear actuators824,826are operated to apply different amounts of pressure on the transport blocks806,808when the print unit802is moved into the print position. In one embodiment, the first linear actuator824is operated to apply more pressure on the transport block806than the pressure applied by the linear actuator826on the transport block808. Operating the first and second linear actuators824,826in this manner ensures that the inside wall872of the first side portion818of the stop block814is urged against the third mechanical stop874and thus the printhead500asecured to the stop block814will be at a predetermined position relative to the third mechanical stop874.

In some embodiments, the printhead transport controller658operates the first and second linear actuators824,826to continuously apply pressure to the transport blocks806,808while the print unit802is in the print position so the printhead holders804do not separate inadvertently.

In addition, the printhead transport controller658may adjust the pressure exerted by the first and second linear actuators824,826on the transport blocks806,808while the print unit802is in the print position to force the printhead holders804closer to one another or further apart to allow fine adjustment of the spacing between adjacent the printhead holders804. It should be apparent to one who has ordinary skill in the art that forcing the printhead holders804closer to one another in this manner may temporarily compress the projections830. Such adjustment of the spacing may be undertaken to adjust stitching between printheads500, for example, to compensate for wear on the mechanical components of the print unit802, dirt or loss of lubrication on the linear bearing rails624,628, and the like.

The printhead holder804includes alignment mechanisms to facilitate aligning the printhead500relative to the substrate and a neighboring printhead500.FIGS.22-26show such alignment mechanisms.

Referring toFIGS.18and22-26, like the printhead holders604,612(FIG.18), the printhead holder804includes a first plate900and a second plate902and the printhead500is removably secured to the first plate900. The first plate900and the second plate902are spaced apart and secured to one another by a plurality of compression springs904and leaf springs906.

As described in greater detail below, a projection908extends from a wall910of the second plate902toward the first plate900. As described in greater detail below, the projection908is journaled through a spacer912, journaled through the second plate902, and secured to a thumbwheel914. Compression of the springs904urges the first and second plates900,902toward each other and thereby causes a wall916of the first plate900to maintain contact with the projection908.

Rotating the thumbwheel914in a first direction causes the projection908to extend away from the wall910and thereby urge the first plate900(and the printhead500) proximal the projection908to move away from the second plate902. Because the plurality of leaf spring906also couples the first plate900and the second plate902, such movement causes the leaf springs906to flex and the first plate900(and thus the printhead500) to rotate in a first direction A about a pivot point918that is beyond the leaf spring906.

Rotating the thumbwheel914in a second direction opposite the first direction causes the projection908to retract toward the wall910. Such retraction in combination with the compression of the springs904causes the first plate900proximal the projection908to move toward the second plate902and, because of the leaf springs906, causes the first plate900(and thus the printhead500) to rotate about the pivot point918in a second direction opposite the first direction A. Thus, the thumbwheel914may be used by an operator to align printheads500of the print unit802relative to one another and the central block608(FIG.18).

FIGS.25A and25Bshow details of the projection908. Referring also toFIGS.25A and25B, the projection908includes an end portion920disposed at one end of a finely threaded screw922that is screwed through a bushing or collar924. The bushing924(and thus the screw922) is journaled through the second plate902, and a portion of the threaded screw920that extends beyond the bushing924is inserted into an orifice in the thumbwheel914and such portion is secured to the thumbwheel914by a setscrew926. The bushing is secured to the plate902by a setscrew928.

The predetermined distance between adjacent printheads500that is necessary for to accurately stitch print produced thereby is modified by adjusting an amount the projection830extends from the sidewall832of the second spacer block836secured to the second plate902. The projection830is journaled through the second spacer block836and secured to a thumbwheel926. The projection830is substantially identical to the projection908and is secured to the thumbwheel926in manner similar to how the projection908is secured to the thumbwheel914, as described above in connection withFIGS.23A and23B. Rotating the thumbwheel926in a first direction causes the projection830to extend away from the sidewall832of the second spacer block836and toward the sidewall834of the first spacer block828of an adjacent printhead holder804and rotating the thumbwheel926in a second direction opposite the first direction causes the projection830to retract toward the sidewall832.

In one embodiment, the finely threaded screw922that comprises the projections830and908includes approximately 254 threads per inch to allow fine adjustment of spacing and rotation between the printheads500so that print produced by adjacent printheads500is accurately stitched.

It should be apparent to one has ordinary skill in the art that the alignment features discussed in connection with the printhead holder804may be incorporated into the printhead holders604.

Referring toFIGS.18and26, each printhead holder804includes first and second linear bearing blocks622,626that facilitate securement of the printhead holder804to the first and second linear bearing rails624,628, respectively, of the central block608of the print unit, as described above in connection withFIGS.15-19.

Similar to the print unit201(FIG.12), the print units602,610of the embodiment600and the print units802of the embodiment800of the print module200are configured to be used with one or more printheads500that have first side edges516and second side edges518that are not parallel to the process direction538. Further, these print units602,610,802may also be used with one or more printheads500that have first side edges516and/or second side edges518that are parallel to the process direction538. For example, in addition to the Fuji Samba series of printheads discussed above in connection with the print unit201, the print units602,610,802may be used with, for example, printheads sold by Kyocera Corporation of Kyoto, Japan, as part no. KJ4B-YH06WST-SL1V and the like.

FIG.27is substantially identical toFIG.21discussed above and shows a bar950that may be secured to a frame952of the print unit802. A bottom edge954of the extends toward the substrate approximately 0.010 inches to 0.020 inches beyond the bottom faces512of the printheads500.

The bar950prevents contact between a substrate being printed on, defects in the substrate, and/or any debris that may be disposed on such substrate and the bottom faces512of the printheads500.

INDUSTRIAL APPLICABILITY