Patent Application
20090179967
The present invention relates to the field of fluid couplings and in particular, fluid couplings for supplying ink to inkjet printheads.
The following applications have been filed by the Applicant simultaneously with the present application:
The disclosures of these co-pending applications are incorporated herein by reference. The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned.
The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference.
The Applicant has developed a wide range of printers that employ pagewidth printheads instead of traditional reciprocating printhead designs. Pagewidth designs increase print speeds as the printhead does not traverse back and forth across the page to deposit a line of an image. The pagewidth printhead simply deposits the ink on the media as it moves past at high speeds. Such printheads have made it possible to perform full colour 1600 dpi printing at speeds in the vicinity of 60 pages per minute; speeds previously unattainable with conventional inkjet printers.
Printing at these speeds consumes ink quickly and this gives rise to problems with supplying the printhead with enough ink. Not only are the flow rates higher but distributing the ink along the entire length of a pagewidth printhead is more complex than feeding ink to a relatively small reciprocating printhead.
Some of the Applicant's printers provide the printhead as a user removable cartridge. This recognizes that individual ink ejection nozzles may fail over time and eventually there are enough dead nozzles to cause artifacts in the printed image. Allowing the user to replace the printhead maintains the print quality without requiring the entire printer to be replaced. It also permits the user to substitute a different printhead for different print jobs. A draft quality printhead can be installed for some low resolution documents printed at high speed, and subsequently removed and replaced with the original high resolution printhead.
A number of the Applicant's printhead cartridges do not have an inbuilt ink supply for the printhead. These printhead cartridges need to be fluidically coupled to the ink supply upon installation. The supply flowrate to the pagewidth printhead is too high for needle valves because of the narrow internal diameter. This requires the coupling conduits to be relatively large and while the complementary structures on each side of the coupling may be self sealing upon disengagement, the wet surfaces can have enough residual ink to drip or run over the exterior surface of the coupling.
Cross contamination of different colored inks is very detrimental to print quality. A drip from the black ink conduit onto the yellow ink conduit can change the color balance for many pages of printing. To avoid this, the conduits should be spaced from each other and positioned such that one conduit is never likely to be vertically above another during installation or removal. However, spacing the conduits apart is counter to compact design and structurally there is less flex in the components during engagement and disengagement if the conduits are clustered around a central axis.
Accordingly, the present invention provides a fluid coupling for an inkjet printhead, the fluid coupling comprising:
an interface plate supporting a plurality of spouts positioned for sealed engagement with corresponding apertures in a complementary socket in order to establish fluid communication between an inkjet printhead and an ink supply; wherein,
the interface plate has surface formations individually associated with each of the spouts respectively, the surface formations defining a preferred flow path along the interface plate for any residual ink draining away from the spouts under gravity, the preferred flow paths being configured to avoid any of the other spouts.
The invention recognizes that subtle surface modifications can be used to define a fluid flow path that residual drops will follow with good reliability. This permits the spouts to be clustered together with little chance of any cross contamination between the colors.
Preferably, the surface formations are grooves in the interface plate. In a further preferred form, the spouts are arranged in a circular formation on the interface plate. In a particularly preferred form, the inkjet printhead is provided as a user replaceable cartridge for installation in a printer body that has the ink supply, the interface plate being positioned on the exterior of the printhead cartridge and the socket being positioned on the printer body. In a particularly preferred form, the grooves extend in a generally vertical direction when the printhead cartridge is oriented as it would be when installed, the grooves deviating from generally vertical to avoid one of the spouts of different color.
In some embodiments, the printhead cartridge has a recess feature the grooves begin at their respective spouts and end at the recess feature. In particularly preferred embodiments, the printhead is a pagewidth printhead. In some embodiments, the printer is an A4 printer and the printhead can print at speeds greater than 40 pages per minute. In some embodiments, each of the apertures in the socket has a shut off valve that is biased closed, the shut off valve being held open when engaged with the corresponding spout. Preferably, the printhead cartridge has an inlet manifold and an outlet manifold, both the inlet and outlet manifolds having a fluid coupling according to the present invention.
Preferred embodiments of the invention will now be described by way of example only, with reference to the accompanying figures, in which:
As best shown in
Disengaging the printhead cartridge 2 from the apertures 122 in the sockets 120 can cause residual ink to dribble from the spouts 52. As discussed above, the spouts on each manifold are clustered together. Grooves 110 are formed in the interface plates 76 to control the flow direction of any residual ink as it runs from a spout under gravity. Without any flow control measures, there is a good chance that the residual ink from one spout would flow onto the spout of a different color. The resulting color mixing is reasonably rapid and pervasive throughout the printhead cartridge 2. If the cartridge is subsequently re-installed in the print engine, the color mixing changes the color balance and is detrimental to image quality. The grooves 110 define a flow path that is generally vertically downwards to be consistent with the gravity feed of the residual drops. The grooves 110 deviate from the vertical in order to avoid other spouts. The grooves 110 terminate in a recess 112 beneath the circle of spouts 52. Residual ink collects in the recess 112 so as to avoid inadvertent spillage and ink stains.
The grooves 110 can be small relative to the size of the residual ink drops draining from the spout 52. Rather than contain the flow, the grooves can merely define a preferred flow path that the drop chooses in preference to all others. For this, the grooves need only be enough to draw and guide the drop by capillary action. The ordinary worker will appreciate that the preferential flow path may also be defined by a ridge, or a series of discrete formations spaced along the interface plate.
The above embodiments are purely illustrative and not restrictive or limiting on the scope of the invention. The skilled worker will readily recognize many variations and modifications which do not depart from the spirit and scope of the broad inventive concept.
