Inkjet printing systems include scanning type systems and single-pass systems that deliver ink to printable media through printheads. In single-pass printing systems, a printhead assembly includes multiple printheads on a print bar that is pre-filled with an internal ink supply. The print bar spans the width of the media and ejects ink as the media continually advances in a direction perpendicular to the print bar. In scanning type printing systems, printhead assemblies include a printhead integrated on a cartridge that has an internal ink supply. One or more cartridges are held by a scanning carriage that scans back and forth across the media as the media is incrementally advanced in a direction perpendicular to the scanning. In either case, the printhead assemblies (i.e., print bars pre-filled with ink, individual print cartridges) encounter water loss during shipping and storage. Water loss can result in print quality defects and reduced printhead life.
Example implementations will now be described with reference to the accompanying drawings, in which:
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.
Overview
As noted above, printhead assemblies that include one or more printheads and an internal integrated ink supply (e.g., print bars pre-filled with ink, print cartridges) can encounter water loss during shipping and storage that results in print quality defects and reduced printhead life. Water loss can occur, for example, through evaporation between seals that join different sections of the printhead assembly, such as manifold, filtration, and pressure regulation sections. In addition, movement during shipping, as well as altitude and temperature variations encountered during shipping, can cause ink or other printhead fluid to spill out or be expelled from the printhead assembly through its fluid interconnects.
As water is lost from a printhead assembly, the decreasing fluid volume creates an increasing negative pressure or vacuum within the assembly. The negative internal pressure can be relieved by an ingestion of air proportionate in volume to the lost water. In the case of refillable printhead assemblies, such as pre-filled page-wide-array (PWA) print bars, air can be ingested either through the printhead nozzles or through the fluid interconnect ports (e.g., fluid interconnect needles). Air ingested through the printhead nozzles causes problems such as ink blockage and poor nozzle performance. Air ingested through the fluid interconnects, however, does not cause such problems, as it generally collects in areas of the assembly housing where it can be removed through various purging techniques. Therefore, allowing air to enter the assembly through the fluid interconnects is desirable because it alleviates internal negative pressure from water loss but avoids air ingestion through printhead nozzles.
Prior solutions that address the water loss and ink spillage from printhead assemblies have mainly involved sealing the assemblies within a pouch and sealing off the fluid interconnects to the assemblies. A pouch is typically made of a metalized material that provides a high barrier to both water loss and air infiltration, and thus maintains the printhead assembly in a humidified atmosphere. The pouch solution works well for smaller, individual print cartridges that have a single printhead and an internal/integrated ink supply. However, a pouch is not practicable for larger PWA print bars with multiple printheads that are pre-filled at a factory with an internal ink supply. Pre-filled PWA print bars begin losing water from the moment they are filled at the factory, and as noted above, they can spill ink through the fluid interconnects during shipping. Print bars are typically shipped from a factory to another location where they are then installed into printers. Printers with pre-installed print bars are then shipped to customers. Neither a print bar nor a printer with a pre-installed print bar are suitable for shipment within a pouch.
To avoid ink spilling out of printhead assemblies through fluid interconnects during shipping, print bars have typically been shipped with seals that cover the fluid interconnects, such as rubber plugs. Prior fluid interconnect seals are impervious to both air and fluid, however, and this attribute unfortunately prevents air from entering the print bar through the interconnects to offset the volume of water being lost through evaporation. Thus, prior interconnect seals do not address the challenge of avoiding undesirable air ingestion through printhead nozzles. Furthermore, the impervious nature of prior fluid interconnect seals often inhibits the seals from preventing ink spilling out of the printhead assembly through the interconnects, because the seals can pop off during shipping due to altitude and temperature variations that cause air within the print bar to expand and contract.
Example printhead assemblies disclosed herein comprise air-permeable, fluid resistant, fluid interconnect covers or seals that improve on prior efforts to reduce the adverse effects of water loss, while also preventing fluid from spilling out of the assemblies through the fluid interconnects. The air-permeable, fluid resistant, fluid interconnect covers allow air to enter the printhead assembly which compensates for the volume of water within the assembly lost during shipping and/or storage. The diffusion of air through the covers alleviates the build up of negative pressure within the assembly and avoids harmful ingestion of air through the printhead nozzles. The air-permeable, fluid resistant, covers allow air to collect upstream of a pressure regulator within a print bar where it can be removed through standard purge routines within the printer. The air-diffusivity and expandability of the fluid interconnect covers also reduce the chances that the covers will pop off during altitude and temperature excursions, which decreases the likelihood that printhead fluid (e.g., ink) will be spilled out of, or expelled from, the printhead assembly through the fluid interconnects.
In one example implementation, a printhead assembly includes a fluid intake section, a fluid interconnect integrated with the fluid intake section to receive fluid from an ink supply assembly, and an air-permeable, fluid-resistant, fluid interconnect cover installed over the fluid interconnect. An example of such a fluid interconnect cover includes an air-permeable, fluid-resistant, fluid interconnect plug comprising a bladder section that enables air to diffuse through bladder walls and into an interior bladder cavity, and retains fluid that escapes from the fluid interconnect.
In another example implementation, a printhead assembly comprises a page-wide-array print bar that includes, a printhead array section comprising multiple printheads, a manifold section to route ink through the print bar to different printheads in the printhead array section, a filter section to filter the ink, a pressure regulation section to regulate ink pressure within the print bar, a fluid intake section to receive the ink and route it to the pressure regulation section, a fluid interconnect on the fluid intake section, and an air-permeable, fluid-resistant fluid interconnect cover to cover the fluid interconnect.
Ink supply assembly 104 supplies fluid ink to printhead assembly 102 and includes a reservoir 120 for storing ink. Ink flows from reservoir 120 to inkjet printhead assembly 102. In one implementation, ink supply assembly 104 is separate from inkjet printhead assembly 102 and supplies ink to inkjet printhead assembly 102 through a fluid interconnect 113 on the printhead assembly 102. For example, a fluid interconnect 113 on printhead assembly 102 may comprise a fluid interconnect needle that penetrates a septum of the ink supply assembly 104 when the supply assembly 104 is installed in the printing system 100, allowing ink to flow from the supply assembly 104 to the printhead assembly 102. In another implementation, inkjet printhead assembly 102 and ink supply assembly 104 are housed together in an inkjet cartridge or pen. In this case, reservoir 120 includes a local reservoir located within the cartridge, but may also include a larger reservoir located separately from the cartridge to refill the local reservoir through a fluid interconnect, such as a supply tube or interconnect needle. In different implementations, an ink supply assembly 104 and/or reservoir 120 can be removed, replaced, and/or refilled.
Mounting assembly 106 positions the printhead assembly 102 relative to the media advance mechanism 108, and the media advance mechanism 108 positions a media page 118 relative to the printhead assembly 102. Thus, a print zone 122 is defined adjacent to nozzles 116 in an area between the printhead assembly 102 and media page 118. In one implementation, inkjet printing system 100 is a scanning type printer that scans inkjet printhead assembly 102 back and forth across the media page 118 as the media advance mechanism 108 incrementally advances the page 118 between scans. In another implementation, inkjet printing system 100 is a single-pass printer with a printhead assembly 102 configured as a page-wide-array (PWA) print bar having multiple printheads 114 to eject ink onto the media page 118 as the media advance mechanism 108 continuously advances the page 118. Thus, media advance mechanism 108 moves the media page 118 through the printer 100 along a print media path that properly positions the page 118 relative to inkjet printhead assembly 102 as drops of ink are ejected onto the page 118. Media advance mechanism 108 can include, for example, a variety of media advance rollers, a moving platform, a motor such as a DC servo motor or a stepper motor to power the media advance rollers and/or moving platform, combinations of such mechanisms, and so on.
Referring still to
Electronic controller 110 receives data 128 from a host system, such as a computer, and stores the data 128 in memory 126. Data 128 represents, for example, a document or image file to be printed. As such, data 128 forms a print job for inkjet printing system 100 that includes one or more print job commands and/or command parameters. Thus, using data 128, electronic controller 110 controls inkjet printhead assembly 102 to eject ink drops from nozzles 116 onto a media page 118 to define patterns of ejected ink drops that form characters, symbols, and/or other graphics or images on the page 118.
The print bar 200 also includes a fluid intake section 212 above the regulation section 210 that receives ink, and functions as an upper manifold to route the ink to appropriate regulators within the pressure regulation section 210. The fluid intake section 212 receives ink through fluid interconnects 113 from one or more ink supply assemblies 104 (not shown in
Referring generally to
The dimensions of the air-permeable, fluid-resistant, fluid interconnect plug 400 depend at least in part on the size of the fluid interconnect needle 300 (or other fluid interconnect 113) the plug 400 is designed to cover. In one implementation, the fluid interconnect plug 400 is on the order of 20 mm in length, with an inner diameter in the range of approximately 6 to 2 mm from the interior bladder cavity 406 to an interior neck cavity 410. The thickness of the plug walls 408 varies from one end of the plug 400 to the other, but in some implementations the thickness of the thin-walled bladder section 402 is on the order of 0.5 mm. The diameter of the interior bladder cavity 406 tapers down in size to a smaller diameter within the interior neck cavity 410. The smaller diameter of the interior neck cavity 410 enables a firm fluidic seal to develop around the fluid interconnect needle 300 when the plug 400 is installed over the interconnect needle 300. In some implementations, the diameter of the interior neck cavity 410 tapers down further to form a pinch section 412 that firmly grasps the fluid interconnect needle 300 and further prevents fluid from escaping the plug 400. The fluid interconnect plug 400 also includes a flared entrance 414 area that facilitates the installation of the plug 400 over the fluid interconnect needle 300.
The fluid interconnect plug 400 can be formed of any air-permeable, fluid resistant material that allows air to diffuse through its outer walls 408 and into its interior bladder cavity 406, while also preventing liquid (e.g., ink) from passing through the walls 408 from its interior cavity 406 to the outside of the plug 400. Furthermore, such material is compliant and enables the thin-walled bladder section 402 to expand like a small balloon under conditions in which the internal pressure of the printhead assembly 102 (e.g., print bar 200) exceeds its external pressure, such as during transportation at high altitudes. Such materials can include, for example, polyisoprene, santoprene, silicone, EPDM (ethylene propylene diene monomer (M-class) rubber), polyethelene, Teflon, Gor-Tex, polyvinylidene fluoride, combinations thereof, and the like.
The dimensions and material composition of an air-permeable, fluid-resistant, fluid interconnect cover 111, in general, depend upon the amount of water loss expected from the printhead assembly 102 (e.g., print bar 200). However, the rate of water loss from one assembly to another can vary. In addition, the amount of water lost from a printhead assembly 102 depends on the amount of time that expires between when the assembly 102 is pre-filled with printhead fluid and when the assembly 102 begins being used. Therefore, the greater the storage and/or shipping time is for a given printhead assembly 102, the higher the water loss will be for that assembly 102. As noted above, the process of air diffusing through the walls of the interconnect cover 111 occurs when there is a build up of negative pressure within the assembly 102. However, the air diffusion does not occur when there is no negative pressure. Accordingly, in view of the difficulty noted in determining the amount of water that will be lost from a printhead assembly 102, the dimensions and material composition of an air-permeable, fluid-resistant, fluid interconnect cover 111, should be selected to accommodate the largest expected amount of water loss from the printhead assembly 102. In general, fluid interconnect covers 111 with larger diffusive surface areas (e.g., greater bladder wall areas in a fluid interconnect plug 400) that are formed out of materials having greater air-permeability (but that are still fluid restrictive), will provide sufficient air diffusivity to accommodate larger volumes of water loss from a printhead assembly 102. Cost and ease of use are also factors to be considered in the dimensions and material composition of an air-permeable, fluid-resistant, fluid interconnect cover 111.
While one example of an air-permeable, fluid-resistant, fluid interconnect cover 111 for a printhead assembly 102 has been described, any number of other interconnect covers 111 having different sizes, shapes and configurations may be suitable, and are contemplated by this disclosure. For example,
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Child | 15260044 | US |