Patent Description:
Inkjet printers are typically used to digitally print various products, such as labels, textiles, ceramic tiles and many more, by dispensing small ink droplets through nozzles of a printing head.

In order to achieve consistent and high-quality prints, the ink parameters, such as the ink viscosity, the ink flow rate and the ink pressure, have to be controlled precisely. If the ink viscosity is too high and/or the ink meniscus pressure too low, the ink might not be able to exit the printing head nozzles. In contrast, a too low ink viscosity or a too high meniscus pressure may result in formation of satellite droplets and overall lower print quality. Furthermore, when performing inkjet printing on porous substrates, the resulting printing dot is influenced by viscosity dependent spreading of the ink on the substrate and penetration of the ink into the substrate.

Especially in high-throughput industrial inkjet printing, the ink control is often complex and requires a sophisticated ink management system with a manifold that distributes the ink to the single print heads and controls the ink temperature such that a desired viscosity is reached.

Inkjet manifolds known from the state of the art typically comprise a plurality of many different parts, such as hoses, connectors and seals that are made from different materials and assembled together. As a result, the manifolds are prone to errors and/or disturbances, such as sealing leakage or clogging caused by formation of ink deposits, which can appear if the ink is incompatible with one of the materials the manifold consists of. <CIT> dislcoses the preamble of claim <NUM>.

The object of the invention is to provide an inkjet manifold that is less prone to such errors and/or disturbances and thus improves the stability of the printing process.

The object of the invention is solved by a manifold for an inkjet printer, comprising a main body with an ink cavity and a temperature control fluid cavity which is in thermal contact with the ink cavity. The manifold further comprises at least one ink inlet, at least one ink outlet, at least one temperature control fluid inlet and at least one temperature control fluid outlet, wherein the main body, the at least one ink inlet, the at least one ink outlet, the at least one temperature control fluid inlet and the at least one temperature control fluid outlet consist of the same material and form a single piece.

In this context, the term "inlet" refers to openings through which a liquid can enter the manifold. The term "outlet" refers to openings through which a liquid can leave the manifold.

The proposed manifold structure with the different manifold elements forming a single piece from the same material reduces the effort for assembling the manifold. Furthermore, compared to conventional manifolds, the total number of applied individual parts and materials and thus potential points of failure is reduced.

In one embodiment, the main body, the at least one ink inlet, the at least one ink outlet, the at least one temperature control fluid inlet and the at least one temperature control fluid outlet are manufactured by rapid prototyping, in particular 3D printing, and consist of a metal.

The rapid prototyping and/or 3D printing technique enables to manufacture the main elements of the manifold in a single time and cost saving processing step, even if the manifold geometry is complex.

Preferably, the main body, the at least one ink inlet, the at least one ink outlet, the at least one temperature control fluid inlet and the at least one temperature control fluid outlet consist of titanium. This metal offers high hardness and excellent corrosion resistivity. Furthermore, titanium is antimagnetic and therefore not prone to interfere with electronic parts.

It is conceivable that the main body comprises a thermally conductive wall separating the ink cavity and the temperature control fluid cavity. In particular, the wall can be made of 3D-printed titanium. The wall prevents direct contact between the printing ink and the temperature control fluid and at the same time allows to effectively transfer heat between both liquids.

In one variant, the main body comprises a plurality of thermally conductive lamellae within the ink cavity. The lamellae may also consist of 3D printed titanium. They provide an additional contact surface between the ink and the main body through which heat can be transferred. Furthermore, the lamellae can influence the ink flow within the ink cavity such that a homogeneous velocity and/or ink pressure distribution is achieved.

In order to further improve the heat transfer between the ink and the temperature control fluid, the lamellae can be arranged such that they extend perpendicularly from the thermally conductive wall through the ink cavity. It is conceivable that the lamellae extend perpendicularly from the thermally conductive wall throughout the whole cross section of the ink cavity.

To allow ink to spread in between the lamellae and/or to flow through the whole cavity, each of the lamellae may comprise at least one opening for ink to pass through. Of course, a lamella can also comprise more than one opening. The ink openings can for example be circular and equidistantly distributed across the lamella to achieve a laminar and/or homogeneous ink flow through the ink cavity.

In one embodiment, the main body comprises a plurality of thermally conductive lamellae within the control fluid cavity. The lamella increase the contact surface between the main body and the temperature control fluid and thus the heating and/or cooling efficiency.

Preferably, the ink cavity and the control fluid cavity are both equipped with lamellae. As an example, the lamellae in the ink cavity and in the control fluid cavity can be oriented parallel or perpendicularly to each other to achieve an efficient heat transfer between the ink and the temperature control fluid across the whole cavity dimensions.

In a further embodiment, the manifold comprises at least four ink outlets, each configured to supply ink to a corresponding print head and/or ink conditioner and at least four ink inlets, each configured to return ink from the corresponding print head and/or ink conditioner such that ink can circulate between the manifold and the print heads and/or ink conditioners during a printing process. By using the manifold to supply ink to a plurality of print heads, the overall number of individual printer parts can be reduced, thus saving manufacturing costs and reducing potential causes of errors. Furthermore, the ink circulation through the manifold reduces or prevents ink deterioration, such as sedimentation and/or formation of debris inside the ink channels, thereby improving the overall stability of the printing process.

In another variant of the manifold, at least one temperature control fluid outlet is configured to supply temperature control fluid to a print head control circuit board cooler and at least one temperature control fluid inlet is configured to return the temperature control fluid from print head control circuit board cooler to the manifold. This allows using the temperature control fluid from the manifold to cool print head control circuit boards, in particular the firing pulse generator for piezoelectric print heads. A separate unit for cooling the electronics is thus not necessary.

In a further embodiment, the main body of the manifold comprises a thermally conductive substantially flat outer surface which is thermally connected to the temperature control fluid cavity. The flat surface allows mounting driving and/or control electronics directly on top of the manifold. Preferably, the main body surface consists of metal, in particular 3D-printed titanium. This material has a high thermal conductivity of > <NUM> W/m*K and can effectively dissipate heat from contacting circuit boards.

Further advantages and features will become apparent from the following description of the invention and from the appended figures, which show a nonlimiting exemplary embodiment of the invention and in which:.

<FIG> schematically shows a side view of a printing unit <NUM> for an industrial single pass inkjet printer. It is conceivable that the inkjet printer is equipped with multiple such printing units <NUM>, which form a stack that defines the print width of the printer.

The printing unit <NUM> comprises a manifold <NUM>, four ink conditioners <NUM> and four piezoelectric inkjet print heads <NUM>, for example Dimatix Samba print heads with a plurality of individually addressable nozzles arranged on a trapezoidal nozzle plate.

The manifold <NUM> comprises a main body <NUM> with an ink cavity <NUM>, a temperature control fluid cavity <NUM>, which is in thermal contact with the ink cavity <NUM>, and an ink collection cavity <NUM>.

A thermally conductive wall <NUM>, which is part of the main body <NUM>, separates the ink cavity <NUM> and the temperature control fluid <NUM> cavity from each other such that ink cannot get in direct contact with the temperature control fluid.

In the given example, the control fluid cavity <NUM> surrounds the ink cavity <NUM> at its bottom as well as the top side. This enables a fast and precise temperature adjustment of ink inside the ink cavity <NUM> by heat conduction through the wall <NUM>.

The manifold <NUM> further comprises a plurality of ink inlets <NUM> through which ink can enter the manifold <NUM>, in particular a main ink inlet <NUM> and four ink return inlets <NUM>.

The main ink inlet <NUM> is adapted to connect an ink supply, for example an ink reservoir, to the ink cavity <NUM> within the main body <NUM>.

The four ink return inlets <NUM> are adapted to connect ink outlets of the print heads <NUM> and/or conditioners <NUM> to the ink return cavity <NUM>.

The manifold <NUM> further comprises a plurality of ink outlets <NUM> through which ink can leave the manifold <NUM>, in particular a main ink outlet <NUM> and four print head feed outlets <NUM>.

The main ink outlet <NUM> is configured to drain ink from the ink return cavity <NUM>, for example into an ink purification unit and/or ink store or into the ink cavity <NUM>.

The four print head feed outlets <NUM> are each adapted to be connected to a corresponding conditioner inlet or print head inlet and thus to supply ink from the ink cavity <NUM> to the conditioner <NUM> and/or print head <NUM> for printing.

In the described embodiment, the ink may flow for example from an ink store into the ink cavity <NUM> within the manifold <NUM>, where it is heated or cooled to a certain temperature. The ink may further flow from the ink cavity <NUM> into the conditioners <NUM> and/or the print heads <NUM>, where part of the ink is ejected from the nozzles. The remaining ink may further flow from the conditioners <NUM> and/or the print heads <NUM> into the ink return cavity <NUM> of the manifold <NUM> and from the ink return cavity <NUM> into a purification unit and/or ink store and eventually back into the ink cavity <NUM>. In other words, the manifold <NUM> can be part of an ink circulation system. Ink may for example circulate between the manifold <NUM> and the print heads <NUM> and/or ink conditioner <NUM> during a printing process.

The manifold <NUM> further comprises a plurality of temperature control fluid inlets <NUM> through which temperature control fluid can enter the manifold <NUM>, in particular a main temperature control fluid inlet <NUM> and two or more temperature control fluid return inlets <NUM>.

The main temperature control fluid inlet <NUM> is adapted to be connected to a chiller such that temperature control fluid of a certain temperature can be supplied from the chiller via the main temperature control fluid inlet <NUM> into the temperature control fluid cavity <NUM>.

The two or more temperature control fluid return inlets <NUM> are adapted to connect further parts of the inkjet printer, for example coolers for electronics, in particular coolers for the conditioners <NUM> and/or the print heads <NUM> and/or a print head control circuit board coolers <NUM> (such as a firepulse generator cooler), to the manifold, in particular to the temperature control fluid cavity <NUM> or to an additional control fluid return cavity <NUM>, such that temperature control fluid can flow from the further parts into the manifold <NUM>.

The manifold <NUM> further comprises a plurality of temperature control fluid outlets <NUM> through which temperature control fluid can leave the manifold <NUM>, in particular a main temperature control fluid outlet <NUM> and two or more peripheral temperature control fluid outlets <NUM>.

The main temperature control fluid outlet <NUM> is adapted to be connected to the chiller such that temperature control fluid can be supplied from the manifold <NUM>, in particular from the control fluid cavity <NUM> or from the additional control fluid return cavity <NUM>, to the chiller.

The two or more peripheral temperature control fluid outlets <NUM> are adapted to connect the temperature control fluid cavity <NUM> to the aforementioned further parts of the inkjet printer that require cooling such that temperature control fluid can flow from the temperature control fluid cavity <NUM> to these parts.

In the described embodiment, the temperature control fluid may flow for example from the chiller into the temperature control fluid cavity <NUM> within the manifold <NUM>, from the temperature control fluid cavity <NUM> to the further parts (e.g. coolers for the conditioners <NUM> and/or the print heads <NUM> and/or the firepulse generator cooler <NUM>), from the further parts into the temperature control fluid return cavity <NUM> and from the temperature control fluid return cavity <NUM> back into the chiller.

It is conceivable that the described temperature control fluid circulation comprises parallel flow paths, for example one path comprising the firepulse generator cooler <NUM> and another path comprising coolers for the conditioners <NUM> and/or the print heads <NUM>. This results in decreased flow resistance of the liquid flow and thus a lower required pump power compared to a series connection.

A schematic 3D illustration of the manifold <NUM> is shown in <FIG>. In the described embodiment, the main body <NUM>, the ink inlets <NUM>, the ink outlets <NUM>, the temperature control fluid inlets <NUM> and the temperature control fluid outlets <NUM> form a single piece and consist of 3D printed titanium. It is conceivable that the whole manifold <NUM> as depicted in <FIG> forms a single 3D printed structure.

Despite the high number of liquid inlets, outlets and cavities, the manifold <NUM> does not comprise any sealing or similar parts made from rubber or similar materials. It is thus very robust and due to the inert nature of the titanium surface highly compatible with many different types of inks, in particular inks containing polar and/or nonpolar and/or organic solvents.

In the described embodiment, the upper outer surface <NUM> of the manifold <NUM> is flat. As the whole manifold <NUM> is made of titanium, the surface <NUM> is thermally connected to the temperature control fluid cavity <NUM> located directly underneath. It is thus possible to mount driving and/or control electronics, such as firepulse generating circuit boards directly on top of the manifold <NUM> and to dissipate their processing and/or waste heat through the outer shell of the manifold <NUM>. This enables an efficient cooling process and a compact design of the printing unit <NUM>.

<FIG> shows a side view of the manifold <NUM> with two indicated cross section lines A-A and B-B.

<FIG> and <FIG> depict the first cross section A-A of <FIG>, showing a cut through the ink cavity <NUM>.

In the described embodiment, the main body <NUM> comprises a plurality of thermally conductive lamellae <NUM> within the ink cavity <NUM>.

The lamellae <NUM> extend perpendicularly from the thermally conductive wall <NUM> through the ink cavity <NUM>, thereby separating the ink cavity <NUM> into a plurality of thin elongated chambers. In order to enable an ink flow between these chambers, each lamella <NUM> comprises a plurality of equidistantly spaced circular holes <NUM> through which ink can pass. In this way, a laminar ink flow with homogeneous flow velocity distribution throughout the whole ink cavity <NUM> can be achieved.

Furthermore, the lamella <NUM> increase the contact surface between the manifold <NUM> and the ink flowing through the ink cavity <NUM>. This enables fast transfer of thermal energy from the titanium structure of the manifold <NUM> to the ink and thus rapid heating and/or cooling of the ink.

<FIG> shows the second cross section B-B of <FIG>, illustrating a cut through the temperature control fluid cavity <NUM>.

In the embodiment, also the control fluid cavity <NUM> is equipped with lamellae <NUM>, which form part of the main body <NUM>. Similar to the ink chamber lamellae <NUM>, also the temperature control chamber lamellae <NUM> improve the transfer of thermal energy and homogenize the flow velocity across the cavity.

Claim 1:
A manifold for an inkjet printer, comprising a main body (<NUM>) with an ink cavity (<NUM>) and a temperature control fluid cavity (<NUM>) which is in thermal contact with the ink cavity (<NUM>), the manifold (<NUM>) further comprising at least one ink inlet, (<NUM>) at least one ink outlet (<NUM>), at least one temperature control fluid inlet (<NUM>) and at least one temperature control fluid outlet (<NUM>), characterised in that the main body (<NUM>), the at least one ink inlet (<NUM>), the at least one ink outlet (<NUM>), the at least one temperature control fluid inlet (<NUM>) and the at least one temperature control fluid outlet (<NUM>) consist of the same material and form a single piece.