Ink protection system for inkjet printers

Abstract: An ink protection device for an inkjet printhead comprises a flap member (330,340,350,370) associated with the printhead and extending generally parallel to the ink ejection surface of the printhead (50) so that when the printhead is mounted in the carriage (40) the flap member extends between the carriage and a face of the printhead, particularly the electrical interconnect (100) face. The device may be in a two part laminar form attached to the bottom of a carriage of the printer and having a flexible part for contacting all four faces of the printheads and a stiff part for support. Both parts having openings aligned with the openings in the carriage through which the printhead snout passes.

Description: The present invention relates to an ink protection device for an inkjet printhead, and in particular to a protection device which protects the electricalinterconnect of a printhead from ink. The present invention relates to the art of inkjet printing mechanisms whether of the thermal or piezo variety which may be included in a variety of different products including copiers and facsimile machines in addition to standalone printers either desktop mounted, portable or freestanding. Herein a freestanding printer will be used to illustrate the present invention. Printers of this type have a printhead carriage which is mounted for reciprocal movement on the printer in a direction orthogonal to the direction of movement of the paper or other medium on which printing is to take place through the printer. The printer carriage of a color printer typically has two or more, usually four, thermal ink jet printheads mounted thereon which may be removable. Each of the printheads contains or is attached to a remote supply of ink which is fed via ink channels within the printhead to an ink ejection mechanism generally in the lower part of the printhead and ejected as drops through a nozzle plate mounted on an ink ejection surface of the printhead. The nozzle plate having numerous small orifices or nozzles therethrough. For thermal (as opposed to piezo-electric)inkjet printheads ink channels or conduits lead to firing chambers each associated with heater elements, such as resistors, which are energized to heat ink within the firing chambers. Upon heating, an ink drop is ejected from a nozzle associated with the energized resistor. To service, that is clean, maintain, protect or recover the correct operation of the printhead, typically a "service station" mechanism is mounted within the printer so the printhead can be moved over to the station for servicing. For storage, or during non-printing periods, the service stations usually include a capping system which hermetically seals the printhead nozzles from contaminants and prevents drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit or other mechanism thatdraws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as "spitting," with the waste ink being collected in a "spittoon" reservoir portion of the service station. After spitting, uncapping, priming or occasionally during printing, most service stations have an elastomeric wiper that wipes the ink ejection surface of the printhead to remove ink residue, as well as any paper dust or other debris that has collected on the face of the printhead. During printing and spitting, some small ink droplets may become airborne within the printer, forming what is known as "ink aerosol". Unfortunately, this ink aerosol often lands in undesirable locations on the inkjet printhead that are not normally cleaned by the printhead service station. For example, this ink aerosol may collect along a portion of the printhead exterior next to the electrical interconnect that sends the firing signals to the printhead. Moreover, the process of wiping the printhead often deposits ink on this portion of the printhead adjacent the electrical interconnect. Beyond leaving the printhead dirty with ink residue, unfortunately, many inkjet inks are also electrically conductive, so any ink smeared on the conductors of the electrical interconnect has the potential for causing a short circuit between the conductors. Ink residue deposited on the printhead next to the electrical interconnect may be smeared on the interconnect conductors when the printhead is removed, and then further smeared across the interconnect when a new printhead is installed increasing the chances for a short circuit to occur. Futhermore such ink may cause corrosion of the electrical contact pads of either the carriage or the printhead. A prior art solution to ink residue adjacent the electrical interconnect comprises the use of a so called "snout wiper" which is a wiper similar to those conventionally used to wipe the ink ejection surface of the printhead, to wipe an area of the vertical interconnect face of the printhead below the electrical interconnect pads. However, in addition to imposing further complication on the service station of the printer and its associated servicing routines it has been found that such snout wiping is insufficient to remove all such ink residue. Furthermore any ink residue that remains has been found to migrate upwards towards the electrical interconnect pads of the printhead through capilliary forces. A further problem due to ink residue (and which is not resolved by snout wiping) is that it has been found that ink aerosol can build up within the stalls of the printer carriage in which the printheads are located and can make its way between the datum surfaces on the printhead and the carriage which serve to accurately align the printhead within the carriage. This can lead to printing errors in images printed due to misplacement of ink droplets fired by the printhead on print media. A further factor in the buildup of ink residue on inkjet printheads is that the lifetimes required of the printheads is increasing, particularly for printheads that are utilised in combination with large volume ink reservoirs which are remote from the printhead (so called "off-axis" systems) and which may be replaced without replacing the printhead. The ink residue problem is exacerbated in an off-axis system because the printheads are replaced less frequently during the useful life of the printer so this residue may build-up over a longer period in contrast to a replaceable printhead system, which requires replacement of the printhead when empty. According to the present invention there is provided an inkjet printing mechanism having a carriage comprising at least one stall for receiving a removably mountable inkjet printhead, the printhead having an ink ejection surface through which ink is ejected and a plurality of faces extending from the ink ejection surface, such that when the printhead is mounted in the carriage stall there exists a gap between at least one face of the printhead and the carriage, and an ink protection device, the device comprising at least one flap member which extends generally parallel to the ink ejection surface ofthe printhead when mounted within the carriage stall, so that the flap member extends at least partially across said gap between the carriage and the face of the printhead and acts as a barrier to the passage of ink, ejected from the printhead, into the carriage. It has been found by the present Applicants that a simple physical barrier to the passage of ink which acts on the printhead when it is mounted in the carriage is effective in greatly reducing the level of ink passing into the carriage past the printhead either in the form of aerosol or liquid in contact with a face of the printhead. Although the flap member may be mounted on the printhead, preferably, the flap member is mounted on the carriage and contacts a face of the printhead. Advantageously, the flap member is composed of a material which is both compliant and resilient so that it is able to repeatedly contact the printhead and form a substantially ink tight seal. Preferably, the flap member is generally parallel to the ink ejection surface of the printhead prior to the insertion of the printhead into the carriage, more preferably the flap member extends at an angle of less than 30 degrees to the plane of the ejection surface ofthe printhead, most preferably at an angle of less than 15 degrees. However, it is advantageous that the printhead deflects the flap member when it is installed so that the flap member curves downwardly, preferably at an angle of less than 45 degrees. In a specific embodiment, the ink protection device comprises four flap members per printhead, one associated with each face of the printhead. This has been found to be very effective at impeding the entry of ink aerosol in the carriage and thus preventing ink residue on the datum surfaces of the printhead and carriage. Conveniently, the device comprises a first substantially laminar component formed of a flexible material and asecond substantially laminar component formed of stiffer material, the first component comprising a plurality of openings each having at least one flap member and the second component comprising a plurality of openings located to be in alignment with the openings in the first component and wherein both components are adapted to be mounted to a surface of the carriage of the printer which is close to a print zone of the printer so that the first component is supported by the second component. This design avoids the need to make any changes to the printer carriage since thedevice can simply be attached to the bottom of the carriage. As printer carridges are complex and serve may functions this is a particularly advantageous and lowcost method of achieving the benefits of the present invention. Preferably, the openings in the second components are larger than the openings in the first component and wherein the relative size of the openings is determined dependent on the flexibility of the first component and the desired contact force between the at least one flap member of the first component and a printhead. The correct contact force between the flap member and the printhead is important since if the force is too low, ink may leak past the flap member and if the force is too high, the flap member may prevent the correct positioning of the printhead within the carriage. Advantageously, the second component comprises a baffle member, for protecting components of the carriage from mechanical damage, located proximate to an interconnect flap member of said first component. This has been found to be useful for purposes other than ink protection, namely for the protection of delicate components of the carriage particularly the electrical interconnect from damage from other components of the printer such as parts of the media handling mechanisms, particularly in the event of a "paper crash" (wherein a protruding portion of a print media interferes with the motion of the carriage. This function is aided if the baffle member extends away from the second component ofthe device at an angle to the plane of the second component and further improved if it comprises, at its extreme ends in the scanning axis direction, a deflector angled further away from the plane of the second component of the device. This deflector is able to act as a ski tip and help the carriage to avoid paper crashes. As an alternatively to this two part construction of the ink protection device, the device may simply comprise a flap member mounted on an electrical connection member of the carriage. This embodiment is preferred when only a single flap member in contact with the interconnect face of each printhead is desired. According to a further aspect of the present invention, there is provided a printhead, adapted for use in an inkjet printing mechanism according to the first aspect of the present invention, the printhead being removably mountable in a carriage of the inkjet printing mechanism and having an ink ejection surface through which ink is ejected and a plurality of faces extending from the ink ejection surface, such that when the printhead is mounted in a carriage stall of the inkjet printing mechanism there exists a gap between at least one face of the printhead and the carriage, the printhead comprising at least one flap member which extends generally parallel to the ink ejection surface of the printhead when mounted within the carriage stall, so that the flap member extends at least partially across said gap between the carriage and the face of the printhead and acts as a barrier to the passage of ink, ejected from the printhead, into the carriage. Further advantages and objects of the present invention will be appreciated from specific embodiments of the present invention which will now be described by way of example only and with reference to the following drawings in which: FIG. 1 illustrates an inkjet printing mechanism, here shown as an inkjet printer 20, in which embodiments of the present invention may be implemented. A variety of inkjet printing mechanisms are commercially available. For instance, some of the printing mechanisms that may embody the present invention include desk top printers, portable printing units, copiers, cameras, video printers, and facsimile machines. For convenience the concepts of the present invention are illustrated in the environment of an inkjet printer 20. The inkjet printer 20 includes a chassis 22 surrounded by a housing or casing enclosure 24, typically of a plastic material, together forming a print assembly portion 26 of the printer 20. While it is apparent that the print assembly portion 26 may be supported by a desk or tabletop, it is preferred to support the print assembly portion 26 with a pair of leg assemblies 28. The printer 20 also has a printer controller, illustrated schematically as a microprocessor 30, that receives instructions from a host device, typically a computer, such as a personal computer or a computer aided drafting (CAD) computer system (not shown). The printer controller 30 may also operate in response to user inputs provided through a key pad and status display portion 32, located on the exterior of the casing 24. A conventional print media handling system (not shown) may be used to advance a continuous sheet of print media 34 from a roll through a printzone 35. The print media may be any type of suitable sheet material, such as paper, poster board, fabric, transparencies, mylar, and the like, but for convenience, the illustrated embodiment is described using paper as the print medium. A carriage guide rod 36 is mounted to the chassis 22 to define a scanning axis 38, with the guide rod 36 slideably supporting an inkjet carriage 40 for travel back and forth, reciprocally, across the printzone 35. A conventional carriage drive motor (not shown) may be used to propel the carriage 40 in response to a control signal received from the controller 30. To provide carriage positional feedback information to controller 33, a conventional metallic encoder strip (not shown) may be extended along the length of the printzone 35 and over the servicing region 42. A conventional optical encoder reader may be mounted on the back surface of printhead carriage 40 to read positional information provided by the encoder strip. Upon completion of printing an image, the carriage 40 may be used to drag a cutting mechanism across the final trailing portion of the media to sever the image from the remainder of the roll 34. Moreover, the illustrated inkjet printing mechanism may also be used for printing images on pre-cut sheets, rather than on media supplied in a roll 34. In the printzone 35, the media sheet receives ink from an inkjet printhead, such as a black ink printhead 50 and three monochrome color ink printheads 52, 54 and 56. The black ink printhead 50 is illustrated herein as containing a pigment-based ink. For the purposes of illustration, color printheads 52, 54 and 56 are described as each containing a dye-based ink of the colors yellow, magenta and cyan, respectively, although it is apparent that the color printheads 52-56 may also contain pigment-based inks in some implementations. It is apparent that other types of inks may also be used in the printheads 50-56, such as paraffin-based inks, as well as hybrid or composite inks having both dye and pigment characteristics. The illustrated printer 20 uses an "off-axis" ink delivery system, having main stationary reservoirs (not shown) for each ink (black, cyan, magenta, yellow) located in an ink supply region 58. In this off-axis system, the printheads 50-56 may be replenished by ink conveyed through a conventional flexible tubing system (not shown) from the stationary main reservoirs, so only a small ink supply is propelled by carriage 40 across the printzone 35 which is located "off-axis" from the path of printhead travel. As used herein, the term "printhead" may also refer to replaceable printheads where each printhead has a reservoir that carries the entire ink supply as the printhead reciprocates over the printzone. The illustrated printheads 50, 52, 54 and 56 have ink ejection surfaces having nozzle plates 60, 62, 64 and 66, respectively, which selectively eject ink to from an image on a sheet of media 34 in the printzone 35. These inkjet printheads 60-66 have a large print swath, for instance about 20 to 25 millimeters (about one inch) wide or wider, although the ink protection concepts described herein may also be applied to smaller inkjet printheads. The concepts disclosed herein for protecting the printheads 60-66 and carriage 40 apply equally to the totally replaceable inkjet printheads, as well as to the illustrated off-axis semi-permanent or permanent printheads, although the greatest benefits of the illustrated system may be realized in an off-axis system where extended printhead life is particularly desirable. The printheads 60, 62, 64 and 66 each have an nozzle plate with a plurality of nozzles formed therethrough in a manner well known to those skilled in the art. The nozzles of each printhead 60-66 are typically formed in at least one, but typically two linear arrays along the nozzle plate. Each linear array is typically aligned in a longitudinal direction perpendicular to the scanning axis 38, with the length of each array determining the maximum image swath for a single pass of the printhead. The illustrated printheads 60-66 are thermal inkjet printheads, although other types of printheads may be used, such as piezoelectric printheads. The thermal printheads 60-66 typically include a plurality of resistors which are associated with the nozzles. Upon energizing a selected resistor, a bubble of gas is formed which ejects a droplet of ink from the nozzle and onto a sheet of paper in the printzone 35 under the nozzle. The printhead resistors are selectively energized in response to firing command control signals delivered from the controller 30 to the printhead carriage 40. FIG.2 illustrates several details of the manner in which the pens 50-56 are installed within the carriage 40. For the purposes of illustration, the black pen 50 is shown, and the concepts illustrated herein are typical to pens 52, 54 and 56. The pen 50 includes an electrical interconnect 100 located along a rearward facing portion of the cartridge. The electrical interconnect 100 comprises a flexible strip which has a series of conductive contact pads located to be in electrical contact with a series of matching contact pads on a flex strip 102 mounted along an interior portion of the carriage 40. To provide a solid physical contact between the pads of the printhead flex strip 100 and the carriage flex strip 102, preferably he carriage flex 102 is mounted above a pusher member 104, which is biased by a spring 105 to push the carriage flex strip 102 into contact with the printhead flex 100, as illustrated by arrow 106 in FIG. 2. The printhead flex 100 carries the electrical signals received from the carriage flex 102 to the firing resistors which heat the ink to eject droplets from nozzles 108 of printhead 50. To allow the printhead 50 to receive black ink from the main storage reservoir 60 in the illustrated off-axis printer 20, the printhead 50 has a straight, hollow inlet needle 110, located along a forward portion of the printhead50. The needle 110 is guarded by a shroud 112 to prevent an operator's fingers from inadvertently coming in contact with the needle. The carriage 40 also supports an inlet valve 114 which has an elastomeric septum 115 defining a performed slit 116 therethrough. The valve 114 also has a flanged inlet port 118, to which a black ink tube 58' is coupled to receive black ink from the mainreservoir 60. The black ink tube 58' is part of the tube assembly of the printer 20 in FIG.1 that delivers ink from each of the main reservoirs 58 to the respective printheads 50-56. As mentioned above, during printing some of the ink droplets ejected from the nozzles 108 never reach the print media, or a spittoon portion (not shown) of the service station 80 during a spitting cycle, but instead these droplets become floating ink aerosol satellites. This ink aerosolfloats until it eventually lands, often on one of the printer components. One exposed region of the printhead 50 which is not cleaned by the conventional, service station black printhead wiper, is shown in FIG.2, where ink residue 120 has accumulated and collected along a lower nose or snout portion 122 of the printhead flex strip 100. Moreover, the act of wiping the printhead 50 with a conventional wiper may also deposits ink on this nose portion 122 in two different ways. The first type of deposit, known as "flicked ink", occurs when wiping the printhead 50 by moving the wiper toward the rear of the printer 20, that is, to the right or negative Y direction in FIG.2. After the end tip of flexed conventional wiper clearsthe edge of the printhead 50, the elastomeric nature of the wiper tries to return b an upright rest position, but instead over-compensates, first by flexing to the far right, then unfortunately by swinging back to the left, eventually dampening out to anupright rest position. During the return-stroke portion of this dampening travel, the wiper flicks ink residue back on the interconnect nose 122. The second type of wiper deposit, known as "wiper scrape", occurs when wiping the printhead 50 in the opposite direction toward the front of printer 20, that is, to the left or positiveY direction in FIG.3 Here, the conventional wiper actually contacts the nose 122 because there is a mandatory interference fit between the wiper and the printhead face, which is required to flex the wiper into wiping contact with the printhead. Thus, the wiper scrapes any ink residue on the front surface of the blade directly onto the nose 122. While it is know to utilise additional specialised snout wipers to wipe the nosel 22 or snout which operate generally at a right angle to the direction of operation of conventional nozzle plate wipers, in an attempt to remove the ink residue 120, it has been found these have disadvantages. Firstly, they require a different operation of the service station of a printer from that required for conventional wiping since they require a different wiping motion. Secondly, if cross contaminantion between different printheads is to be avoided, one snout wiper per printhead must be provided in addition to the conventional nozzle wipers and other service components. Thirdly, such snout wipers have been found to not be completely effective in preventing remaining ink residue from migratingup the interconnect 100 of printheads by capilliary action to reach the electrical connection pads of the printhead or carriage. Fouthly, snout wipers are completely ineffective in preventing ingress of aerosol between the carriage 40 and the printhead 50. Although embodiments of the present invention are useful and advantageous when employed with all types of inkjet printhead and carriages, a particular printhead installation process will now be described (which is required due the ink delivery system employed) which worsens the above described problem of ink residue forming on the snout and being passed to the interconnect. The inlet needle 110 on the printhead 50 is rigidly mounted within the shroud to pierce the septum 115 along slit 116 during printheadinstallation. The shroud 112 is sized to surround the valve 114. While the valve 114 is preferably constructed to tilt slightly with respect to the carriage 40, it is apparent from this construction that insertion of needle 110 into septum 115, as well as removal therefrom, must use a substantially linear motion as indicated by arrow 123 in FIG 2. Thus, if printhead installation/removal for the inlet valve 114 at the front of the cartridge must be in a substantially vertical direction 123, then installation/removal at the rear of the cartridge where the electrical interconnect is located must also be vertical, as illustrated by arrow 124 in FIG. 2. Unfortunately, the inks used in inkjet printers oftenhave an electrically conductive nature, so ink residue smeared between contact pads of the carriage interconnect 102 may form an electrical bridge between those contact pads, causing them to short out. Then when a fresh printhead is installed vertically, the spring 105 again pushes the carriage interconnect 102 into contact with the interconnect 100 of the fresh cartridge, smearing this ink residue across both interconnects 100 and 102. With this smeared ink now smeared randomly between the contact pads, there exists a likelihood that two ormore the contact pads of interconnects 100, 102 may become shorted out, causing nozzles to either not fire or to misfire, either occasion of which severely degrades print quality. Worse yet, this short circuit condition may permanently damage the printhead, the printer 20, or both. As shown in FIG. 2, the printhead 50 has a number of alignment datums 134, 160, 170. These printhead alignment datums mate againstmatching carriage alignment datums to align the printhead with the carriage in the X, Y and Z directions, as wel as with respect to the 0x, 0y and 0z rotational degrees of freedom about these axes to ensure accurate dot placement on the media. A further problem caused by ink aerosol rather than by the build up of ink residue on the snout of a printhead is that it has been found that ink aerosol can build up within the stalls of the printer carriage in which the printheads are located and can make its way between the datum surfaces on the printhead and the carriage which serve to accurately align the printhead within the carriage. This can lead to printing errors in images printed due to misplacement of ink droplets fired by the printhead on print media. Refering now to FIGS. 3, 4 and 5, which show a carriage dam 380 and a carridge protector 400. The dam 380 is formed from a single sheet of polyester of 0.125mm thickness having a tensile strength of 190 Kg/cm2 longitudinally and 120 Kg/cm2 tranversely. Within the sheet four openings 310 have been punched in a conventional manner. Lines 320 show where the sheet has been cut, thus it can be seen that each opening 310 is surrounded by four flaps 340, 350, 370, 330 of the material of the sheet which are attached to the sheet at one of their sides and free to move at the other of their sides. The size of the openings 310 measuring from the free sides of the flaps is 13.1 mm by 31.5 mm. The dam 380 also has holes 360 cut through it to facilitate mounting on the carridge 40. It will be noted that the two end flaps 340, 350 have been cut to include more material of the sheet at their ends 315 than is included in the ends 325 of the side flaps 330, 370. Thus the end flaps 340, 350 extend to their greatest allowed width. These two end flaps will engage the end faces 150, 180 of the printhead. Flap 340 engaging the interconnect face 150 of the printhead and flap 350 engaging the opposite end face 180 of the printhead. The side flaps 330, 370 will engage the side faces 190, 195 of the printhead. Finally it should be noted that the side flap 330 at its end 390 has been cut so as to avoid contact with the side face 190 of the printhead. With reference to Fig 4, a carriage protector 400 is formed from a single sheet of stainless steel of thickness 0.5mm and has four openings 410 punched through it of size 21 mm by 40 mm. The centres of the openings 410 are spaced at the same separation as the centres of the openings 310 in the dam 380. At one side of the protector 400 is a baffle 430 runing the length of the protector and having a deflector 440 at each of its ends. The baffle 430 is bent away from the plane of the protector 400 along the line 450 and the deflectors 440 are bent further away from the plane of the protector along the lines 460. The protector 400 has holes 420 cut through it which have the same separation as the holes 360 in the dam 380. Fig. 5 is an exploded perspective view showing the assembly of the dam 380 and protector 400 onto the carriage 40. Carriage 40 has a number of plastic moulded studs 510 which protrude from its lower surface 520. The dam 380 is first aligned with the bottom 520 of the carriage 40 and mounted so that the studs 510 protrude through the holes 360 in the dam. Then protector 400 is place on top of dam 380 so that the studs 510 also protrude through the holes 420 in the protector. Heat and pressure is then applied to the studs 510 so that they deform against the surface of the protector 400 to firmly hold both the protector and the dam 380 on the bottom of the carriage. It will be appreciate that other attachment means such as screws or glue may be employed. Fig. 6 is a view from below the bottom 520 of the carriage 40 looking upwards and shows the dam and protector in place and the protrusion of the flaps 330, 370, 340, 350 past the edges of the openings 410 in the protector. Also it can be seen that the openings 310 in the dam 380 are aligned with stalls 500 in the carriage. Fig. 7 is a view of the same assembly as Fig 6 taken from above and additionally carriage datum700, 710, 720 can be seen which interact with printhead datums shown in Fig 2. Fig. 8 is perspective view from below and to the side showing one printhead 50 mounted in the carriage and engaged with the flaps of the dam. Fig. 9 is a magnified view of Fig 8 also showing the nozzles 108 and interconnect 100 of the printhead. From the above description and figures it can be seen that when a printhead is mounted within the carriage of a printer provide with a dam and protector the flaps of the dam engage the printhead and in some cases flex against it. The flaps effectively cover the gap between the printhead and the carriage on all sides of the printhead and thus prevent aerosol from entering the carriage from the printzone. Also the flap 340 prevents any ink on the printhead snout from progressing up the interconnect 100 towards the electrical pads (not shown). It will be appreciated that the relative sizes of the openings in the dam and the protector and the size of the snout of the printhead are important to achieve the right level of interference between the printhead and the flaps. In this embodiment the snout is 14.6 mm by 31.7mm. The interference between the flaps and the printhead is as follows 0 mm for flap 350 the front flap for face 180, 0.5 mm for the rear flap 340 for the interconnect face 150, 0.5mm for the side flap 330, for the other side flap 1.0 mm 370. This last flap 370 protects the Y datums and thus has a large interference because if the printhead was moved away from the datum due to a paper crash the maximum possible displacement of the printhead is 0.6mm and with the maximum positioning error due to tolerancing of 0.3mm this will ensure that the flap will always remain in contact and bent downwards. The gap 390 in the flap 330 is in order (when employing a snout wiper) to allow any dried ink accumulated on the side face of the printhead 190 to pass the flap 330 without contact so that the flap does not knock this ink off the printhead and onto the printing surface. Figure 10A shows an alternative embodiment in which only a single flap 340 for the interconnect face 150 is provided. The flaps 340 are glued at 820 directly onto a carriage flex circuit which is then mounted on the carriage. Figure 10B shows the flex circuit in a carriage and the flap 340 acting on a printhead 50. Figure 11 shows a pinch wheel arrangement 900 of a media system of the printer in relation to the baffle 430 and deflector 440. Figure 12 shows a general view of the pinch wheel arrangement in the printer.

Claims: An inkjet printing mechanism (20) having: a carriage (40) comprising at least one stall (500) for receiving a removably mountable inkjet printhead (50-56), the printhead (50-56) having an ink ejection surface through which ink is ejected and a plurality of faces (150, 180, 190, 195) extending from the ink ejection surface, such that when the printhead (50-56) is mounted in the carriage stall (500) there exists a gap between at least one face (150, 180, 190, 195) of the printhead (50-56) and the carriage (40), and an ink protection device, the device comprising: at least one flap member (340, 350, 370, 330) which extends generally parallel to the ink ejection surface of the printhead (50-56) when mounted within the carriage stall (500), so that the flap member (340, 350, 370, 330) extends at least partially across said gap between the carriage (40) and the face (150, 180, 190, 195) of the printhead (50-56) and acts as a barrier to the passage of ink, ejected from the printhead (50-56), into the carriage (40). An inkjet printing mechanism (20) according to claim 1, wherein one of said plurality of faces (150, 180, 190, 195) of the printhead (50-56) is an interconnect face (150) for electrical connection with the carriage (40), and wherein said flap member (340, 350, 370, 330) is positioned within the carriage (40) so as to form a barrier to the passage of ink to said interconnect face (150). An inkjet printing mechanism (20) according to claim 1 or 2, wherein said flap member (340, 350, 370, 330) is formed of a resilient material and a first end of the flap member (340, 350, 370, 330) is attached to the carriage (40) of the printer and a second end of the flap member (340, 350, 370, 330) is free to move. An inkjet printing mechanism (20) according to claim 3, wherein said second end of the flap member (340, 350, 370, 330) is arranged to be deflected when the printhead (50-56) is installed into a stall (500) of the carriage (40). An inkjet printing mechanism (20) according to claim 4, the flap member (340, 350, 370, 330) is arranged to be deflected, by the printhead (50-56), by less than 45 degrees. An inkjet printing mechanism (20) according to claim 5, wherein prior to said deflection of the flap member (340, 350, 370, 330), the flap member (340, 350, 370, 330) extends at an angle of less than 30 degrees to the plane of the ejection surface of the printhead (50-56) when mounted in the carriage (40). An inkjet printing mechanism (20) according to any preceding claim, wherein said flap member (340, 350, 370, 330) is formed of a compliant material and wherein upon installation of the printhead (50-56) into a stall (500) of the carriage (40), the flap member (340, 350, 370, 330) engages a face (150, 180, 190, 195) of the printhead (50-56) so as to substantially prevent ink from flowing past the flap member (340, 350, 370, 330). An inkjet printing mechanism (20) according to any preceding claim, comprising a plurality of flap members (340, 350, 370, 330) each arranged to be aligned with a different face (150, 180, 190, 195) of the printhead (50-56). An inkjet printing mechanism (20) according to claim 8, when dependent on any one of claims 3 to 7, wherein the flap members (340, 350, 370, 330) are arranged so that the amount of deflection caused by the installation of the printhead (50-56) for two of said plurality of flap members (340, 350, 370, 330) is different. An inkjet printing mechanism (20) according to claim 9, wherein the flap members (340, 350, 370, 330) are arranged so that amount of deflection of a flap member (340, 350, 370, 330) aligned with a printhead face (150, 180, 190, 195) having a positioning datum surface (134, 160, 170) is greater than the amount of deflection of a flap member (340, 350, 370, 330) aligned with a printhead face (150, 180, 190, 195) not having a positioning datum surface (134, 160, 170). An inkjet printing mechanism (20) according to any one of claims 8 to 10, wherein said plurality of flap members (340, 350, 370, 330) are formed from a single substantially laminar sheet (380) mounted to a lower part of the carriage (40). An inkjet printing mechanism (20) according to claim 11, wherein the flap members (340, 350, 370, 330) surround an opening in a stall (500) of the carriage (40) through which the printhead ink ejection surface passes during installation in the carriage (40). An inkjet printing mechanism (20) according to any one of claims 8 to 12, wherein the device comprises four flap members (340, 350, 370, 330) associated with the printhead (50-56). An inkjet printing mechanism (20) according to any one of claims 12 or 13, wherein the flap member (340) aligned with the interconnect face (150) of the printhead (50-56) extends the full width of said opening in the stall (500) of the carriage (40) and wherein the flap member(s) (350, 370, 330) aligned with neighbouring faces (180, 190, 195) of the printhead (50-56) extend less than the whole width of the opening in the stall (500). An inkjet printing mechanism (20) according to claim 14, wherein a flap member (330) neighbouring the interconnect face flap member (340), at an end of said flap member adjacent the interconnect face flap member (340), comprises a portion which, when a printhead (50-56) is installed in the carriage (40), does not extend far enough to engage the printhead (50-56). An inkjet printing mechanism (20) according to any one of claims 11 to 15, wherein said single substantially laminar sheet (380) comprises a plurality of openings each having a plurality of flap members (340, 350, 370, 330) and wherein said openings are located to be in alignment with openings in stalls (500) of the carriage (40) through which printhead ink ejection surfaces pass during installation of printheads (50-56) into the carriage (40). An inkjet printing mechanism (20) according to any preceding claim, comprising a first substantially laminar component (380) formed of a flexible material and a second substantially laminar component (400) formed of stiffer material, the first component (380) comprising a plurality of openings each having at least one flap member (340, 350, 370, 330) and the second component (400) comprising a plurality of openings located to be in alignment with said openings in the first component (380) and wherein both components are adapted to be mounted to a surface of the carriage (40) which is close to a print zone of the inkjet printing mechanism (20) so that the first component (380) is supported by the second component (400). An inkjet printing mechanism (20) according to claim 17, wherein said openings in said second component (400) are larger than said openings in said first component (380). An inkjet printing mechanism (20) according to claim 17 or 18, wherein said second component (400) comprises a baffle member (430), for protecting components of the carriage (40) from mechanical damage, located proximate to an interconnect flap member (340) of said first component (380). An inkjet printing mechanism (20) according to claim 19, wherein the baffle member (430) extends away from the second component (400) at an angle to the plane of the second component (400). An inkjet printing mechanism (20) according to claim 19 or 20, wherein the baffle member (340) extends along a scanning axis of the carriage (40) and comprises at its extreme ends in the scanning axis direction, a deflector (440) angled further away from the plane of the second component (400). An inkjet printing mechanism (20) according to any preceding claim, wherein the carriage (40) comprises an electrical connection member (800) for establishing electrical connection to an interconnect face (150) of a printhead (50-56) and wherein said flap member (340) is mounted on said electrical connection member (800) of the carriage (40). A printhead (50-56), adapted for use in the inkjet printing mechanism (20) claimed in any preceding claim, the printhead (50-56) being removably mountable in a carriage (40) of the inkjet printing mechanism (20) and having an ink ejection surface through which ink is ejected and a plurality of faces (150, 180, 190, 195) extending from the ink ejection surface, such that when the printhead (50-56) is mounted in a carriage stall (500) of the inkjet printing mechanism (20) there exists a gap between at least one face (150, 180, 190, 195) of the printhead (50-56) and the carriage (40), the printhead (50-56) comprising at least one flap member (340, 350, 370, 330) which extends generally parallel to the ink ejection surface of the printhead (50-56) when mounted within the carriage stall, so that the flap member (340, 350, 370, 330) extends at least partially across said gap between the carriage (40) and the face (150, 180, 190, 195) ofthe printhead (50-56) and acts as a barrier to the passage of ink, ejected from the printhead (50-56), into the carriage (40). A printhead (50-56) according to claim 23, wherein said flap member (340, 350, 370, 330) is mounted on a face (150, 180, 190, 195) of the printhead (50-56) and engages the carriage (40) when the printhead (50-56) is installed into the carriage (40).

Inventors: ALVAREZ JOSE A, TAYLOR CHRISTOPHER, ALVAREZ, JOSE A., TAYLOR, CHRISTOPHER, Alvarez, José A.
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1999
Main classification: B41J2
IPC codes: B41J2