Ink Regulator for Inkjet Printer

Abstract

The present invention relates to an ink regulator (14) for an inkjet printer, the ink regulator (14) comprising a body (18) having an ink attenuation cavity (24), the ink regulator (14) further comprising a heat transfer element (26), at least one ink inlet (28), and at least one ink outlet (34), the body (18), the heat transfer element (26), at least one ink inlet (28), and at least one ink outlet (34) being made of the same material and forming a one-piece molded article.

Description

Technical Field

[0001] The present invention relates to an ink regulator for an inkjet printer.

Background Art

[0002] An inkjet printer is typically used to eject small ink droplets from the nozzles of a print head for digital printing on various products such as labels, fabrics, ceramic tiles, etc.

[0003] In order to achieve stable high-quality printing, it is necessary to accurately control ink parameters such as ink viscosity, ink flow rate, and ink pressure. If the ink viscosity is too high and / or the meniscus pressure of the ink is too low, the ink may not be able to come out of the nozzles of the print head. In contrast, if the ink viscosity is too low or the meniscus pressure is too high, satellite droplets may be formed as a result, and the print quality may be degraded overall. Furthermore, when performing inkjet printing on a porous substrate, the resulting printed dots are affected by the spread of the ink on the substrate and the penetration of the ink into the substrate, which depends on the viscosity.

[0004] In particular, in high-throughput industrial inkjet printing, ink control is often complex and requires an advanced ink management system having a manifold for distributing the ink to a single print head and / or controlling the ink temperature to achieve a desired viscosity.

[0005] Furthermore, in a high-performance inkjet printer, an ink regulator is applied that enables direct and accurate control of ink parameters at the inlet and / or outlet of the print head. Such an ink regulator may include means for measuring and adjusting ink pressure, means for measuring and adjusting ink temperature, means for flushing the print head, means for circulating ink through the print head, means for damping ink vibrations, and / or means for equalizing fluctuations in ink flow rate and / or ink pressure that may be caused by an ink circulation pump.

[0006] Conventionally known ink regulators typically comprise a plurality of different components made of different materials, such as hoses, connectors, seals, etc., assembled together. As a result, the ink regulator is prone to errors and / or malfunctions, such as seal leakage or clogging due to the formation of ink deposits, which may occur when the ink is incompatible with one of the materials forming the manifold.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an ink regulator for an inkjet printer in which such errors and / or malfunctions are less likely to occur, and thus the stability of the printing process is improved.

Means for Solving the Problems

[0008] The object of the present invention is solved by an ink regulator for an inkjet printer, the ink regulator comprising a body having an ink damping cavity, the ink regulator further comprising a heat transfer element, at least one ink inlet, and at least one ink outlet, the body, the heat transfer element, at least one ink inlet, and at least one ink outlet being made of the same material and forming a one-piece molded article.

[0009] In this context, the term "inlet" refers to an opening through which liquid can enter the ink regulator. The term "outlet" refers to an opening through which liquid can exit the ink regulator.

[0010] The purpose of the ink damping cavity is thought to be to dampen vibrations in the ink and / or to equalize fluctuations in the ink flow rate and / or ink pressure. The heat transfer element can be used to adjust the temperature of the ink.

[0011] The proposed ink regulator structure with different ink regulator elements formed from the same material reduces the labor required to assemble the ink regulator. Furthermore, compared to conventional ink regulators, the total number of individual parts and materials applied, and thus potential failure points, is reduced.

[0012] In one embodiment, the body, the heat transfer element, at least one ink inlet, and at least one ink outlet are manufactured by rapid prototyping, specifically 3D printing, and are composed of metal.

[0013] Rapid prototyping and / or 3D printing technology enables the main elements of the ink regulator to be manufactured in a single cost-saving process step, even if the ink regulator shape is complex.

[0014] Preferably, the body, the heat transfer element, at least one ink inlet, and at least one ink outlet are composed of titanium. This metal is highly hard and has excellent corrosion resistance. Furthermore, titanium is non-magnetic and thus less likely to cause interference with electronic components.

[0015] In a further embodiment, the ink regulator comprises a membrane and a spring plate that seals the ink damping cavity, and the membrane is disposed between the body and the spring plate. The membrane is elastically deformable. When the ink pressure in the ink damping cavity fluctuates, the membrane can flex inwardly and / or outwardly so that the pressure fluctuations are dampened. The spring plate stabilizes the membrane and limits the maximum flexure.

[0016] The ink attenuation cavity may be of circular shape. This enables the application of a circular membrane that seals the ink attenuation cavity. Due to the circular shape, the membrane deforms symmetrically. This enables attenuation in a relatively high pressure region and generally improves process control.

[0017] To achieve a very compact design, the body can comprise at least one linear path having an opening inside the ink attenuation cavity, where a spring plate guiding element can be arranged inside. Specifically, the spring plate guiding element can be a piston with a spring attached that presses on the spring plate to ensure accurate and smooth movement of the spring plate.

[0018] In another variant, the heat transfer element comprises a cavity configured to receive a heating element and an ink path surrounding the cavity. This enables heating of the ink without direct contact between the ink and the heating element.

[0019] Preferably, the ink path comprises an ink outlet configured to be directly connected to the inlet of the print head. The arrangement close to the print head increases the accuracy of print temperature control. The deviation between the set temperature and the actual print temperature is prevented or at least minimized by the short flow path between the sensor and the print head.

[0020] In a further embodiment, the ink regulator comprises a first pressure sensor configured to measure the ink pressure in a first pressure range inside the ink path and a second pressure sensor configured to measure the ink pressure in a second pressure range inside the ink path. Specifically, the first pressure sensor can be configured to accurately measure a low ink pressure of up to 50 mbar. The second pressure sensor can be configured to measure a high pressure of up to 1 bar. This improves the overall accuracy of ink pressure measurement and / or control over the pressure ranges relevant to all applications.

[0021] In addition, the ink regulator can comprise a coupling region configured to receive screws or bolts that directly couple the ink regulator to the print head. This facilitates assembly. Furthermore, a rigid coupling can be formed between the ink regulator and the print head, which reduces the risk of leakage at the interface of both components.

[0022] In a further variant, the ink regulator comprises a valve for flushing the print head. This enables quick and easy cleaning of the print head, for example, to return a clogged nozzle to a normal state, without the need to disassemble the printing press and / or the printing unit.

[0023] Further advantages and features should become apparent from the following description of the invention and the accompanying drawings, which illustrate non-limiting exemplary embodiments of the invention.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0025] FIG. 1 schematically shows a side view of a printing unit 10 of an industrial single-pass inkjet printing press. It is conceivable that the inkjet printing press comprises a plurality of such printing units 10 that form a stack defining the printing width of the printer.

[0026] The printing unit 10 includes a manifold 12, four ink regulators 14, and four piezoelectric inkjet printheads 16 (e.g., a Dimatix Samba printhead having a plurality of individually addressable nozzles arranged on a trapezoidal nozzle plate). Each ink regulator 14 corresponds to an individual printhead 16.

[0027] In the described embodiment, the manifold 12 has means for controlling the ink temperature, such as a body 18 having an ink cavity 20 that is in thermal contact with a temperature-controlled fluid cavity 22, and means for distributing the ink to the individual ink regulators 14, specifically, a plurality of inlets and outlets for the ink.

[0028] FIG. 2 shows a schematic 3D view of an ink regulator 14 according to the present invention adapted to receive ink from the manifold 12. The ink regulator 14 includes a body 18 having a circular ink damping cavity 24 for damping pressure fluctuations of the ink by means of a circulation pump, in particular.

[0029] The ink regulator 14 further includes a heat transfer element 26 for finely adjusting the ink temperature, two ink inlets 28 through which ink can enter the ink regulator 14, specifically, a main ink inlet 30 and an ink return inlet 32, and two ink outlets 34 through which ink can exit the ink regulator 14, specifically, a main ink outlet 36 and a printhead supply outlet 38.

[0030] The ink regulator 14 further includes a coupling region 40 configured to receive screws or bolts for directly coupling the ink regulator 14 to the printhead 16.

[0031] In the described embodiment, the body 18, the heat transfer element 26, the ink inlets 28, the ink outlets 34, and the coupling region 40 form a one-piece molded article and are composed of 3D printed titanium.

[0032] Figure 3 shows a schematic 3D view of this integrally formed article.

[0033] The integrally formed article can further comprise additional elements such as a liquid inlet, for example, a flushing liquid inlet 42 through which flushing liquid for cleaning the print head can enter the ink regulator 14.

[0034] In an embodiment, the integrally formed article has an opening 46 inside the ink attenuation cavity 24 and further comprises three linear paths 44 for receiving movable parts, specifically guide elements.

[0035] The entire structure including the body 18, the heat transfer element 26, the ink inlet 28, the ink outlet 34, the coupling region 40, the flushing liquid inlet 42, and the three linear paths 44 as shown in Figure 3 can be 3D printed in a single and cost-saving process step.

[0036] Despite the numerous different elements and complex structure, the integrally formed article does not include any seals or similar parts made of rubber or equivalent materials. Thus, the integrally formed article is very robust and highly compatible with many different types of inks, specifically inks containing polar solvents and / or non-polar solvents and / or organic solvents, due to the inert nature of the titanium surface.

[0037] In the described embodiment, the ink regulator 14 includes a plurality of additional parts attached to the 3D printed titanium structure.

[0038] Figure 4 shows an exploded view of these ink regulator parts, which includes a circulation pump 48, a valve 50 for regulating the liquid flow through the print head supply outlet 38, a valve 52 for enabling flushing of the print head, and specifically a sealed circuit board 54 for controlling the circulation pump 48 and / or the valves 50, 52.

[0039] In the described embodiment, the circulation pump 48 is disposed between the ink return inlet 32 and the main ink outlet 36. As a result, the circulating ink flows through the print head 16 before passing through the circulation pump 48.

[0040] The manifold 12 may be considered to form part of the ink circulation system. As an example, the circulation pump 48 can generate an ink flow from the manifold 12 to the ink regulator 14, from the ink regulator 14 to the print head 16, from the print head 16 to the ink regulator 14, and back from the ink regulator 14 to the manifold 12.

[0041] The valve 50 can adjust and / or block the ink circulation, for example, when cleaning and / or flushing of the print head is intended.

[0042] The ink regulator 14 further includes a circular membrane 56 for sealing the ink damping cavity 24, a spring plate 58, and a spring plate guide element 60.

[0043] FIG. 5 shows a first cross-section of the assembled ink regulator 14, specifically the ink damping cavity 24 and the corresponding components.

[0044] The membrane 56 is elastically deformable and is disposed between the body 18 and the spring plate 58. When the ink pressure in the ink damping cavity 24 varies, the membrane 56 can deform and / or flex symmetrically towards and / or away from the body 18, such that the cavity volume changes to attenuate the pressure fluctuations. The spring plate 58 stabilizes the membrane 56 during flexure and limits its maximum movement.

[0045] The spring plate guide element 60 is a piston to which a spring is attached, and this piston is movably fitted within the linear path 44 of the body 18. Due to the spring attachment, the spring plate guide element 60 compresses the diaphragm 56 and / or the spring plate 58, thereby ensuring accurate and smooth movement of the spring plate. It is conceivable that the damping characteristics of the ink damping cavity 24 depend on the Young's modulus of the attachment spring and / or the spring plate 58.

[0046] Figure 6 shows a second cross-section of the assembled ink regulator 14, specifically of the heat transfer element 26.

[0047] In an embodiment, the heat transfer element 26 comprises a cavity with a heating element 64, specifically a resistive heater, disposed therein.

[0048] The heat transfer element 26 further comprises an ink path surrounding the heater cavity.

[0049] The walls forming the heater cavity, as well as the surrounding ink path, may be composed of 3D printed titanium with high thermal conductivity. Thus, heat from the heating element 64 is efficiently conducted towards the ink within the ink path.

[0050] The ink path comprises a printhead supply outlet 38 directly connected to an ink outlet and, in an embodiment, to the inlet of the printhead 16. Thus, the temperature of the ink can be adjusted immediately before the ink enters the printhead 16.

[0051] In the described embodiment, the ink regulator 14 further comprises a first pressure sensor 68 configured to measure the ink pressure within a first pressure range within the ink path, and a second pressure sensor 70 configured to measure the ink pressure within a second pressure range within the ink path.

[0052] The use of a plurality of pressure sensors 68, 70 with different ranges improves the overall accuracy of ink pressure measurement and thus process control.

Description of Reference Numerals

[0053] 14 Ink regulator 18 Main body 24 Ink attenuation cavity 26 Heat transfer element 28 Ink inlet 34 Ink outlet

Claims

1. An ink regulator for an inkjet printer, comprising a main body (18) having an ink attenuation cavity (24), wherein the ink regulator (14) further comprises a heat transfer element (26), at least one ink inlet (28), and at least one ink outlet (34), the main body (18), the heat transfer element (26), the at least one ink inlet (28), and the at least one ink outlet (34) are made of the same material and form an integrally molded product, the ink regulator.

2. The ink regulator according to claim 1, wherein the main body (18), the heat transfer element (26), the at least one ink inlet (28), and the at least one ink outlet (34) are made of 3D printed metal.

3. The ink regulator according to claim 1 or 2, wherein the main body (18), the heat transfer element (26), the at least one ink inlet (28), and the at least one ink outlet (34) are made of titanium.

4. The ink regulator according to any one of claims 1 to 3, wherein the ink attenuation cavity (24) has a circular shape.

5. The ink regulator according to any one of claims 1 to 4, further comprising a membrane (56) and a spring plate (58) for sealing the ink attenuation cavity (24), and the membrane (56) is disposed between the main body (18) and the spring plate (58).

6. The ink regulator according to any one of claims 1 to 5, wherein the main body (18) comprises at least one linear path (44) having an opening (46) inside the ink attenuation cavity (24) configured to receive the spring plate guide element (60).

7. The ink regulator according to any one of claims 1 to 6, wherein the heat transfer element (26) comprises a cavity configured to receive a heating element (64) and an ink path surrounding the cavity.

8. The ink regulator according to claim 7, wherein the ink path comprises an ink outlet (34) configured to be directly connected to an inlet of a print head (16).

9. A first pressure sensor (68) configured to measure an ink pressure within a first pressure range inside the ink flow path, and a second pressure sensor (70) configured to measure an ink pressure within a second pressure range inside the ink flow path. The ink regulator according to claim 7 or 8 further comprises.

10. The ink regulator according to any one of claims 1 to 9, further comprising a coupling region (40) configured to receive a screw or bolt for directly coupling the ink regulator (14) to the print head (16).

11. The ink regulator according to any one of claims 1 to 10, further comprising a valve (52) for flushing the print head.

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