Air dryer

Abstract

An air dryer (1) is provided for use with an inkjet printer (50) comprising a printhead (15) for applying an inked image (18) to a substrate (16). The air dryer (1) comprises: a housing (2) in which an inner space (3) is enclosed; an air supply device (5) configured to supply air into the inner space (3) of the housing; a heating element (6) configured to heat air; and an air guide (8) communicating with the internal space (3). The air guide (8) is configured to direct the hot air jet (10) at the inked image (18) on the substrate (16) in order to dry the inked image (18). The air guide (8) is configured such that the hot air jet (10) between the air guide (8) and the substrate (16) forms an angle [theta] of between 0 and 30 degrees with respect to the direction of travel X of the substrate (16).

Description

Technical Field

[0001] The present disclosure relates to an air dryer for use with an inkjet printer including a printhead for applying an inked image to a substrate. More particularly, but not exclusively, the present disclosure relates to an air dryer for use with a continuous inkjet printer to dry an inked image printed by the continuous inkjet printer using water-based ink. Background Art

[0002] Inkjet printing systems are used in a wide variety of printing applications. One such application is printing an inked image (e.g., expiration date, batch number, etc.) on a product package (hereinafter referred to as a substrate) placed in a high-speed automated production line. In an inkjet printing system, the print consists of a single drop of ink generated at the nozzle and propelled toward the substrate. There are two main systems: drop-on-demand, in which ink droplets for printing are generated as needed and when needed; and continuous inkjet printing, in which droplets are continuously generated and only selected droplets are directed to the substrate, recycling other droplets to the ink source. It should be understood that the ink droplets applied to the substrate become wet immediately after printing, and if they are not dried quickly, the wet ink presents a handling problem because it may smear or smudge easily. When the printing process occurs as part of the high-speed operation of the production line, it must be performed quickly and efficiently, that is, the inked image must be applied and dried within a few seconds for further processing.

[0003] A continuous inkjet printer supplies pressurized ink to a printhead droplet generator where a continuous stream of ink emanating from a nozzle is broken up into individual regular droplets by, for example, an oscillating piezoelectric element. The droplets are directed through charging electrodes where they are selectively and individually given a predetermined charge before passing through a transverse electric field provided across a pair of deflection plates. Each charged droplet is deflected by the field by an amount that depends on its charge before impacting the substrate, while uncharged droplets proceed without deflection and are collected at a gutter from which they are recycled to the ink supply for reuse. The charged droplets bypass the gutter and impact the substrate at a position determined by the charge on the droplet and the position of the substrate relative to the printhead. Typically, the substrate moves in one direction relative to the printhead and the droplets are deflected in a direction generally perpendicular thereto, although the deflection plates may be oriented obliquely relative to the vertical to compensate for the velocity of the substrate (the movement of the substrate relative to the printhead between droplet arrivals means that a row of droplets would otherwise not extend completely perpendicular to the direction of movement of the substrate). The maximum width of the droplet line on the substrate in the direction perpendicular to the movement of the substrate can be referred to as the print width of the inkjet printer. The print width of a continuous inkjet printer is usually determined by the maximum deflection angle of the droplets and the printing distance between the print head and the substrate. The print width of a drop-on-demand inkjet printer can be determined by the width of the nozzle array in its print head.

[0004] In continuous inkjet printing, characters are printed by a matrix comprising a regular array of potential drop positions. Each matrix comprises a number of columns (strokes), each column being defined by a line comprising a number of potential drop positions (e.g., seven) determined by the charge applied to the droplets. The maximum width of each column (i.e., the maximum width of the character) is defined by the print width of the continuous inkjet printer. Thus, each available drop is charged according to its expected position in the stroke. If a particular drop is not used, the drop is not charged and is captured at the trough for recycling. The cycle is repeated for all strokes in the matrix and then begins again for the next character matrix.

[0005] The ink is delivered to the printhead under pressure by an ink supply system, which is typically housed in a sealed compartment of a cabinet that includes separate compartments for control circuitry and a user interface panel. The system includes a main pump that draws ink from a tank of the ink supply system via a filter and delivers it under pressure to the printhead. As the ink is consumed, the tank is refilled as needed from a replaceable ink cartridge that is releasably connected to the tank via a supply conduit. The ink is supplied from the tank to the printhead via a flexible delivery conduit. Unused ink drops captured by the gutter are recirculated to the tank via a return conduit by a pump. The flow of ink in each conduit is typically controlled by a solenoid valve and / or other similar components.

[0006] As the ink circulates through the system, there is a tendency for the ink to thicken due to solvent evaporation, particularly in connection with recirculating ink that has been exposed to air in the passages between the nozzles and the gutter. To compensate for this, "make-up" solvent is added to the ink from a replaceable solvent cartridge as needed to keep the ink viscosity within desired limits. The solvent may also be used to rinse parts of the printhead, such as the nozzles and gutter, during a cleaning cycle. Solvents are typically highly volatile chemicals. Therefore, it is expected that significant amounts of solvent evaporate into the environment during operation of a continuous inkjet printer.

[0007] Methyl ethyl ketone (MEK) and other solvents are widely used in inks for continuous inkjet printers. However, these materials have the risk of being classified as carcinogens, mutagens or reproductive toxins (CMR) in the near future, even though they are not currently classified as such. Another risk is that these solvents are classified as volatile organic compounds (VOCs) and are subject to VOC regulations.

[0008] Water-based inks (where water is the only solvent) represent a promising solution for non-CMR and non-VOC inks for continuous inkjet printers. However, in a typical laboratory environment, the drying time of water-based inks (due to natural evaporation) is about 20-25 seconds. In comparison, the typical drying time of MEK-based inks is less than 2 seconds, and the typical drying time of ethanol-based inks is less than 4 seconds. The long drying time of water-based inks presents handling issues for the printed substrate, thus reducing the efficiency of automated production lines.

[0009] It is therefore desirable to provide a drying device that is capable of shortening the drying time of an inked image printed on a substrate by a continuous inkjet printer using water-based inks. It is an object of the present disclosure, inter alia, to provide such a drying device. Summary of the invention

[0010] According to a first aspect of the present disclosure, there is provided an air dryer for use with an inkjet printer, the inkjet printer comprising a print head for applying an inked image to a substrate, wherein the air dryer comprises: a shell, the shell enclosing an internal space therein; an air supply device, the air supply device being configured to supply air into the internal space of the shell; a heating element, the heating element being configured to heat the air; and an air guide, which is connected to the internal space and is used to guide a jet of hot air to the inked image on the substrate so as to dry the inked image, and wherein the air guide is configured so that the jet of hot air between the air guide and the substrate forms an angle between 0 and 30 degrees relative to a direction of travel of the substrate.

[0011] By configuring the air guide so that the hot air jet between the air guide and the substrate forms an angle between 0 and 30 degrees relative to the direction of travel of the substrate, the hot air jet blows in a direction nearly parallel to the direction of travel of the substrate. This arrangement is useful for maximizing the contact time between the inked image / substrate and the hot air, thereby reducing the drying time of the inked image without consuming more electrical energy. As a result, the operating cost of the air dryer is relatively low. Using the air dryer, the drying time of an ink image printed by water-based ink can be shortened from 20-25 seconds to less than 5 seconds, while consuming less than 300 watts of electricity.

[0012] The expression "hot air jet between the air guide and the substrate" refers to the section of the jet just leaving the air guide but before reaching any surface of the substrate. Thus, the jet between the air guide and the substrate travels in a direction mainly determined by the air guide and is substantially unaffected by the surface orientation of the substrate. It should be understood that the hot air jet between the air guide and the substrate travels in a substantially straight line.

[0013] The angle is measured at the intersection between the line along which the jet travels and the line along which the substrate travels. For two intersecting lines that are not perpendicular to each other, there are two angles between the lines - acute angles and obtuse angles. Angles between 0 and 30 degrees refer to the acute angle between the lines. In other words, the air guide is configured so that the jet between the air guide and the substrate forms an angle between 0 and 30 degrees relative to a line parallel to the direction of travel of the substrate.

[0014] The heating element may be arranged between the air supply device and the interior space. Alternatively, the heating element may be arranged within the interior space of the housing.

[0015] At least a portion of the air guide may be attached to the housing, or may be integrally formed with the housing.

[0016] It should be understood that in the present disclosure, the term "in communication with" means "in fluid communication with."

[0017] The air guide may include a nozzle.

[0018] The nozzle may be attached to the housing, or may be formed integrally with the housing.

[0019] The angle may be between 0 and 20 degrees. Further or alternatively, the angle may be between 0 and 15 degrees, between 5 and 30 degrees, between 5 and 20 degrees, or between 5 and 15 degrees.

[0020] The angle may be approximately 10 degrees.

[0021] The air guide may include a tubular structure through which the hot air jet exits the interior space, and wherein the tubular structure forms an angle between 0 and 30 degrees with respect to a direction of travel of the substrate.

[0022] In other words, the tubular structure of the air guide defines the jet direction between the air guide and the substrate and provides a simple mechanism to guide the hot air.The central axis of the tubular structure may form an angle between 0 and 30 degrees relative to the direction of travel of the substrate.

[0023] The tubular structure may have any suitable cross-sectional shape, which is not limited to circular, oval, square, rectangular, polygonal, or even non-geometric shapes, etc. Furthermore, the tubular structure may have a varying cross-sectional area along the central axis.

[0024] The angle may be between 0 and 20 degrees. Further or alternatively, the angle may be between 0 and 15 degrees, between 5 and 30 degrees, between 5 and 20 degrees, or between 5 and 15 degrees.

[0025] The angle may be approximately 10 degrees.

[0026] The air guide may be configured such that a jet between the air guide and the substrate has a velocity component opposite to a direction of travel of the substrate.

[0027] In other words, the air guide is placed at a downstream area of ​​the print head along the traveling direction of the substrate, and a jet of hot air is directed toward the print head.

[0028] By having the velocity component of the hot air jet opposite to the direction of travel of the substrate, the hot air can achieve a greater velocity relative to the substrate, which is useful for reducing the drying time of the inked image. Thus, this arrangement allows power savings to be obtained at the same target drying time, or improved drying time at the same amount of power consumption.

[0029] The air guide may comprise an air outlet from which the hot air jet leaves the air guide, and the cross-sectional area of ​​the air outlet is smaller than the cross-sectional area of ​​the interior space of the housing.

[0030] In particular, the cross-sectional area of ​​the air outlet may be smaller than the cross-sectional area of ​​the interior space of the housing at (or near) the heating element. For example, the cross-sectional area of ​​the air outlet may be at most 20%, 10%, 5% or 1% of the cross-sectional area of ​​the interior space (e.g., at or near the heating element).

[0031] In a situation where the heating element is arranged within the interior space of the shell, the cross-sectional dimensions of the heating element may be smaller than the cross-sectional dimensions of the interior space of the shell, and the cross-sectional area of ​​the air outlet may be further smaller than the cross-sectional area of ​​the heating element (for example, up to 20%, 10%, 5% or 1% of the cross-sectional area of ​​the heating element).

[0032] In other words, the housing and / or the air guide restrict the flow of air supplied into the interior space or heated by the heating element. As a result, the hot air jet leaving the air outlet will have a greater velocity than the air supplied into the interior space of the housing by the air supply device (or the air heated by the heating element). This arrangement is useful for reducing the power consumption of the air dryer at the same target drying time, because the drying time of the inked image is generally reduced by increasing the velocity of the hot air directed toward the inked image. In addition, this arrangement allows the air supply device and the heating element to operate at a lesser intensity in order to provide the same hot air jet velocity, thereby extending the life of the air supply device and the heating element.

[0033] It will be appreciated that the term "cross-sectional area" is defined along a plane perpendicular to the direction of air flow through the air dryer.

[0034] The width of the air outlet can be between 0.5 and 2 times the print width of the inkjet printer. Thus, the width of the hot air jet between the air guide and the substrate will substantially match the print width. This is useful for increasing the efficiency of the air dryer.

[0035] It should be understood that the "width" of the air outlet or the "width" of the jet is defined along a direction perpendicular to a plane which is parallel to both the direction of travel of the substrate and the direction of travel of the hot air jet.

[0036] The air guide may include a converging nozzle.

[0037] The term "converging nozzle" means that the size of the air outlet of the nozzle is smaller than the size of the air inlet of the nozzle. It should be understood that the air outlet of the nozzle is the air outlet of the above-mentioned air guide.

[0038] The converging nozzle may have an air inlet and an air outlet. The cross-sectional area of ​​the air inlet may be at least 4 times the cross-sectional area of ​​the air outlet. The cross-sectional area of ​​the air inlet may be at least 9 times the cross-sectional area of ​​the air outlet.

[0039] The use of a converging nozzle allows power to be saved by using a restricted air flow at the same target drying time. In addition, the restricted air flow will heat up fewer surrounding parts.

[0040] The hot air jet downstream of the air guide may have a temperature between 200°C and 350°C.

[0041] Advantageously, this temperature range does not result in a significant temperature increase of commonly used substrate materials (e.g., cardboard, plastic, glass, etc.). Therefore, the air dryer is less likely to damage the substrate or cause any safety hazards.

[0042] The hot air jet downstream of the air guide may have a temperature between 250°C and 350°C.

[0043] It should be understood that the term "downstream" in the expression "hot air jet downstream of the air guide" is defined along the blowing direction of the hot air jet. Therefore, "hot air jet downstream of the air guide" refers to the section of the jet just leaving the air guide.

[0044] The hot air jet downstream of the air guide may have a temperature between 250°C and 300°C.

[0045] The hot air jet downstream of the air guide may have a velocity relative to the print head of no more than 50 m / s.

[0046] At speeds not exceeding 50 m / s, the hot air jet causes negligible damage to the print quality of the inked image.

[0047] The hot air jet downstream of the air guide may have a velocity relative to the print head of no more than 30 m / s.

[0048] The hot air jet downstream of the air guide may have an air velocity in the range of 6 to 50 m / s or 6 to 30 m / s.

[0049] The hot air jet downstream of the air guide may have a velocity relative to the print head in the range of 10 to 20 m / s.

[0050] The air guide may be spaced apart from the print head by approximately 30 mm to 1500 mm along the direction of travel of the substrate.

[0051] Preferably, the air guide may be spaced apart from the print head by about 70 mm to 300 mm along the traveling direction of the substrate.

[0052] The air guide may be spaced apart from the print head by at least 100 mm along the direction of travel of the substrate.

[0053] The interior space of the housing may include a first flow path and a second flow path, and the air supply device may be configured to supply air to both the first flow path and the second flow path. The air dryer may be configured so that the air supplied to the first flow path flows through the heating element to generate a hot air jet, and the air supplied to the second flow path does not flow through the heating element to generate a cold air jet. The air guide may be configured to guide the hot air jet and the cold air jet out of the interior space.

[0054] It will be appreciated that the cold air jet has a lower temperature than the hot air jet.Although the cold air jet is not directly heated by the heating element, it may have a slightly higher temperature than the air originally coming from the air supply due to the heat exchange between the first and second flow paths.

[0055] The cold air jet acts as an air jacket for the hot air jet. The air jacket is useful to increase the length of the high air velocity and high temperature zone of the hot air jet, thereby reducing the drying time of the inked image.

[0056] The air dryer may be configured such that the cool air jet travels at substantially the same speed as the hot air jet.

[0057] The air dryer may be configured such that the cool air jet travels in a direction substantially parallel to the direction of travel of the hot air jet.

[0058] The air dryer may be configured such that the cold air jet at least partially surrounds the hot air jet.

[0059] Surrounding the heated air with cool air is useful to prevent ambient entrainment. This arrangement is also beneficial because less energy is required to accelerate the air sheath than to heat a larger volume of hot air.

[0060] The cold air jet may comprise a plurality of parallel cold air jets substantially surrounding the hot air jet.

[0061] The first flow path may be separated from the second flow path by at least one inner wall within the housing.

[0062] The second flow path may substantially surround the first flow path. By surrounding the first flow path (along which the hot air jet flows) with the second flow path (along which the cold air jet flows), the housing of the air dryer may be safe for the user without requiring any insulating sleeve.

[0063] The air dryer may further comprise a mounting device on which the housing is mounted.

[0064] The mounting device can be configured to hold the housing so that the position and orientation of the air guide is fixed. In this way, the hot air jet between the air guide and the substrate can form a fixed angle relative to the direction of travel of the substrate.

[0065] The inkjet printer may be a continuous inkjet printer.

[0066] Inkjet printers can use low-volatile inks.

[0067] The low volatility ink may have a drying time of at least 2 seconds at 25°C under ambient conditions.

[0068] The low volatility ink may have a drying time of at least 5 seconds, at least 10 seconds, at least 15 seconds, or at least 20 seconds at 25°C under ambient conditions.

[0069] The expression "under ambient conditions" means that no active heating or air flow is provided to the ink.

[0070] Low volatility inks may contain a mixture of water and organic compounds.

[0071] The low volatility ink may comprise at least 50% by weight water.The low volatility ink may be substantially water-based.

[0072] Low volatility inks may contain less than 20 wt % (or more preferably less than 10 wt % or 5 wt %) of volatile organic compounds (eg, methyl ethyl ketone).

[0073] Inkjet printers can use water-based inks.

[0074] The water-based ink may not contain any solvents that are volatile organic compounds (eg, methyl ethyl ketone).

[0075] According to a second aspect of the present disclosure, there is provided an inkjet printing system comprising: an inkjet printer including a printhead for applying an inked image to a substrate; an air dryer of the first aspect; and a conveyor for moving the substrate past the printhead and the air dryer.

[0076] The inkjet printing system may further include a mounting device on which the air dryer may be mounted.

[0077] The conveyor may take any suitable form as long as it allows the substrate to be transported past the print head and the air dryer. It should be understood that the conveyor is not limited to a belt conveyor or a roller conveyor. The term "conveyor" may be used interchangeably with "conveyor mechanism".

[0078] According to a third aspect of the present disclosure, there is provided a method for drying an inked image printed on a substrate by an inkjet printer, comprising: supplying air into an internal space of a shell; heating the air; and guiding the hot air jet to the inked image using an air guide connected to the internal space, wherein the hot air jet between the air guide and the substrate forms an angle between 0 degrees and 30 degrees relative to a direction of travel of the substrate.

[0079] The angle may be between 0 and 20 degrees. Further or alternatively, the angle may be between 0 and 15 degrees, between 5 and 30 degrees, between 5 and 20 degrees, or between 5 and 15 degrees.

[0080] The angle may be approximately 10 degrees.

[0081] According to a fourth aspect of the present disclosure, there is provided a method for drying an inked image printed on a substrate by an inkjet printer using water-based ink, the method comprising: generating hot air and directing the hot air to the inked image to dry the inked image within 10 seconds using less than 500 watts of power consumption.

[0082] Generating and directing may include generating and directing hot air at the inked image to dry the inked image in less than 5 seconds using less than 300 watts of power consumption.

[0083] Where appropriate, any optional features described above in relation to one aspect of the disclosure may be applied to another aspect of the disclosure.

[0084] It should also be understood that the various numerical ranges or values ​​described in this disclosure allow for a certain degree of variability in the stated values ​​of the endpoints of the ranges or the individual stated values, e.g., ±10%. For example, a stated value of 10° may be In addition, values ​​expressed in range format should be interpreted in a flexible manner to include not only the values ​​explicitly recited as the end points of the range, but also all individual values ​​or sub-ranges encompassed within the range, as if each value and sub-range were explicitly recited. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] In order that the present disclosure may be more fully understood, several embodiments of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0086] Figure 1 is a schematic diagram of an inkjet printing system including an air dryer according to a first aspect of the present disclosure;

[0087] Figure 2 is Figure 1 An enlarged schematic diagram of an air guide used in an air dryer of;

[0088] Figure 3 is a schematic diagram of an inkjet printing system including an air dryer according to a second aspect of the present disclosure;

[0089] Figure 4 It is shown in Figure 1 a graph of measured temperatures of a substrate used in an inkjet printing system;

[0090] Figure 5 It is shown in Figure 1 a graph showing the relationship between the maximum temperature rise of the substrate measured and the temperature of the air leaving the air guide in the inkjet printing system of FIG. 1 ;

[0091] Figure 6 is Figure 1 A photograph of an exemplary air guide for use in an air dryer of;

[0092] Figure 7 is a graph showing the effect of air temperature on drying time and substrate temperature;

[0093] Figure 8 is a graph showing the relationship between drying time and air speed;

[0094] Fig. 9 The drying time is shown Figure 1 A diagram showing a relationship between a distance between an air dryer and a print head of an inkjet printing system;

[0095] Fig.10 is a schematic diagram of an air dryer according to another aspect of the present disclosure;

[0096] Fig.11 When the air dryer housing and the outer wall of the air guide are partially removed Fig.10Schematic diagram of an air dryer;

[0097] Fig.12 Schematically shows the Fig.10 (a) perspective view and (b) side view of a downstream end of an air guide used in an air dryer of;

[0098] Fig.13 Schematically illustrates the processing steps of a method for drying an inked image printed on a substrate by an inkjet printer according to one aspect of the present disclosure;

[0099] Fig.14 The process steps of a method for drying an inked image printed on a substrate using water-based ink by an inkjet printer according to another aspect of the present disclosure are schematically shown.

[0100] It should be understood that the drawings are for illustration purposes only and are not drawn to scale. DETAILED DESCRIPTION

[0101] Figure 1 The inkjet printing system 100 according to the first embodiment of the present disclosure is schematically shown. The inkjet printing system 100 comprises an inkjet printer 50 having a print head 15, an air dryer 1 and a conveyor 20 which moves a substrate 16 in a direction X past the print head 15 and the air dryer 1 .

[0102] Printhead 15 generates ink droplets and directs the ink droplets to the surface of substrate 16 as described above (e.g., Figure 1 The top surface shown in the figure) is provided to apply the inked image 18 to the surface of the substrate 16. The inked image 18 may be one or more of numbers, letters, barcodes, QR codes, images, and / or any other symbol codes or characters, etc. The substrate 16 may be any substrate on which ink is printed, such as bottles, cans, cartons, packages, etc. Common materials for the substrate 16 include, for example, cardboard, plastic, and / or glass, etc.

[0103] The inkjet printer 50 may be a continuous inkjet printer. As described above, if the print head 15 uses water-based ink to print the inked image 18, the natural drying time of the inked image 18 will be about 20-25 seconds in a typical laboratory environment. Therefore, the air dryer 1 is used to reduce the drying time of the inked image 18. The air dryer may also be referred to as a dryer or an ink drying device, which is used interchangeably with the term "air dryer" in this disclosure.

[0104] The air dryer 1 is placed downstream of the print head 15 along the travel direction X of the substrate 16. The substrate 16 having the wet inked image 18 printed thereon then immediately passes through the air dryer 1. Figure 1The air dryer 1 includes a housing 2 enclosing an interior space 3 therein (the housing 2 is generally airtight except for its two ends), an air supply device 5 for supplying air into the interior space 3, a heating element 6 for heating the air supplied into the interior space 3, and an air guide 8 in fluid communication with the interior space 3, so that the air supplied into the interior space 3 leaves at a high speed via the air guide 8 to generate a hot air jet 10. A mounting device 40 (e.g., a mounting bracket or frame) is used to hold the air dryer 1 (particularly the housing 2) in place. It should be understood that the mounting device 40 does not hinder the movement of the base 16 or the conveyor 20.

[0105] The air guide 8 guides the hot air jet 10 from the inner space 3 to the inked image 18 to accelerate the drying of the inked image 18. The distance between the air outlet of the air guide 8 and the print head 15 in the horizontal direction (eg, line X or X') is Figure 1 The inner space 3 can also be called an air chamber.

[0106] The air supply device 5 is Figure 1 However, it should be understood that the air supply device 5 can take other suitable forms as long as it delivers air to the internal space 3 under pressure. For example, the air supply device 5 can be a compressor, or an external pressurized air source connected to the internal space 3 via an air supply line.

[0107] exist Figure 1 In the example of , the heating element 6 is located between the air supply device 5 and the interior space 3, so that the air passes through the heating element 6 before entering the interior space 3. Other suitable arrangements of the heating element 6 can be used, provided that the supplied air is heated before leaving the interior space 3. For example, depending on the size and / or geometry of the housing 2, the heating element 6 can be located in the interior space 3 of the housing 2. The heating element 6 can be an electric heater. In particular, the heating element 6 can include a coil or other controllable heater and can heat the air in the interior space 3 to a temperature preferably in the range of 200°C to 350°C.

[0108] like Figure 1 As shown, the mounting device 40 holds the housing 2 of the air dryer 1 so that the position and inclination of the air dryer 1 relative to the print head 15 are fixed. More specifically, the air guide 8 is configured so that the hot air jet 10 between the air guide 8 and the substrate 16 travels along a direction A, and the direction A forms an angle θ with respect to a line X', which is parallel to the travel direction X of the substrate 16.

[0109] Figure 2 An enlarged view of the air guide 8 is shown. Figure 1 and Figure 2In the example of , the air guide 8 is implemented as a nozzle. However, it should be understood that the air guide 8 can take various suitable forms, including but not limited to one or more of a nozzle, a guide vane, and a guide plate having a surface that defines the travel direction of the jet 10 under the Coanda effect. The air guide 8 can be provided separately and then attached to the housing 2. Alternatively, a part or all of the air guide 8 can be formed integrally with the housing 2.

[0110] refer to Figure 2 , the air guide 8 has a single air inlet 11, a single air outlet 13 and a tubular structure 9 defining the air outlet 13. In particular, the downstream end of the tubular structure 9 is the air outlet 13. The tubular structure 9 has a central axis 17, and the hot air 10 leaving the air guide 8 tends to travel along the central axis 17. In other words, the central axis 17 substantially coincides with the travel direction A of the hot air jet 10.

[0111] Angle θ is defined as the acute angle between two intersecting lines, which include the line where direction A lies and line X'. For two intersecting lines that are not perpendicular to each other, there are always two angles between the lines - an acute angle and an obtuse angle. Angle θ refers to the value of the acute angle between the lines. In the present disclosure, angle θ is between 0°C and 30°C (or not more than 30°C). In this way, the hot air 10 is blown in a direction that is nearly parallel to line X' (or the direction of travel X of the substrate 16). This arrangement is useful for increasing the contact time between the inked image 18 and the hot air 10, which in turn reduces the drying time of the inked image 18 without consuming more electricity. More preferably, angle θ is between 0°C and 20°C (or not more than 20°C) or between 0°C and 15°C (or not more than 15°C).

[0112] The contact time is maximized when the travel direction A of the hot air jet 10 is parallel to the travel direction X of the substrate 16, that is, when the angle θ is 0°C. However, in such an arrangement, a portion of the air guide 8 will be at the same height as the inked image 18, so the air guide 8 will block the travel path of the substrate 16. Therefore, the angle θ is generally greater than 0°C (e.g., not less than 5°C). Therefore, the angle θ can be any value in the range between 5°C and 30°C, between 5°C and 20°C, between 5°C and 15°C. In the most preferred embodiment, the angle θ is about 10°C, which is used to minimize the dyeing time of the inked image 18 while still allowing the substrate 16 to travel through the air guide 8.

[0113] Further references Figure 2, the hot air jet 10 that has just left the air guide 8 (i.e., downstream of the air guide 8 in direction A) has a velocity V along the direction A. The velocity V (relative to the printer 50 or the print head 15) is preferably less than or equal to 50 m / s (meters per second) (e.g., in the range between 6 m / s and 50 m / s). More preferably, the velocity V does not exceed 30 m / s and may be in the range between 6 m / s and 30 m / s (more preferably between 10 m / s and 20 m / s). The velocity V of the jet 10 is determined by the volume velocity of the air supplied into the interior space 3 by the air supply device 5 and the cross-sectional area of ​​the air outlet 13 of the air guide 8. The velocity V can be decomposed into a horizontal velocity component V parallel to the line X' (or the travel direction X of the substrate 16). X and a vertical velocity component V perpendicular to the travel direction X of the substrate 16 Y Since the angle θ is between 0° and 30°, the horizontal velocity component V X The magnitude of is close to the magnitude of velocity V.

[0114] exist Figure 1 and Figure 2 In the example of FIG. 5 , the hot air jet 10 is blown into the inked image 18 downstream of the print head 15 in an upstream direction along the path of the substrate 16 moving through the printer 50. In other words, the air guide 8 directs the hot air jet from a position downstream of the print head 15 toward the print head 15. The term "downstream" as used herein is with reference to the direction of travel X of the substrate 16. Thus, the horizontal velocity component V X This is opposite to the travel direction X of the substrate 16 . In this way, the speed of the hot air jet 10 relative to the substrate 16 is close to the sum of the travel speed of the hot air jet 10 and the travel speed of the substrate 16 .

[0115] It should be understood that in order to achieve an angle of 0° to 30° between the direction of travel A and the line X' (or the direction of travel X) as defined above, the air dryer may also be arranged as follows: Figure 3 Place in the orientation shown. Figure 3 An inkjet printing system 100a according to a second embodiment of the present disclosure is schematically shown. Elements of the inkjet printing system 100a that are identical to elements of the inkjet printing system 100 are identified using the same reference numerals. Elements that correspond to but are different from those of the inkjet printing system 100 are identified using the same numerical references, but the letter "a" is used for differentiation. The features and advantages described above with reference to the first embodiment generally apply to the second embodiment. Figure 3 The air dryer 1a can be turned horizontally Figure 1In particular, the air dryer 1a blows the hot air jet 10a in a downstream direction along the path of travel of the substrate 16. In other words, the air guide 8a guides the hot air jet 10a away from the print head 15 from a position downstream of the print head 15. It should be understood that in Figure 3 In FIG. 1 , the horizontal velocity component of the hot air jet 10a is in the same direction as the travel direction X of the substrate 16. Thus, the velocity of the hot air jet 10a relative to the substrate 16 is close to the travel velocity of the hot air jet 10a minus the travel velocity of the substrate 16.

[0116] As reference below Figure 7 As mentioned above, a higher speed of the hot air jet relative to the substrate 16 will reduce the drying time of the inked image 18. Therefore, the hot air jet 10 is blown toward the print head 15 ( Figure 1 ) than blowing the hot air jet 10a away from the print head 15 ( Figure 3 ) is more beneficial. Compared with air dryer 1a, air dryer 1 allows power saving at the same drying time target.

[0117] exist Figure 1 In the configuration of the hot air jet 10, it will be appreciated that the air velocity should be controlled so as to minimize any adverse effects of the air on the printing process. It has been found that an air velocity of 50 m / s (relative to the print head 15) does not disrupt the print quality (e.g., legibility or consistency with the original design) of an inked image 18 (e.g., applied by a typical continuous inkjet printer) when the distance D between the air guide 8 and the print head 15 is not less than about 4 inches (about 10.16 cm). In particular, with an air velocity not exceeding 50 m / s, the hot air jet 10 is less likely to disrupt the deposition of ink droplets on the substrate 16 or disturb the position of the substrate 16.

[0118] In addition, Figure 3 Compared to the setting of Figure 1 The substrate 16 tends to move a much shorter distance from the print head 15. This is because the hot air jet 10 can act on the inked image 18 immediately after the print head 15 applies the inked image 18. However, in Figure 3 In the embodiment of the present invention, the substrate 16 having the inked image 18 must travel a considerable distance before coming into contact with the hot air jet 10a.

[0119] In the case where the substrate 16 contains temperature-sensitive food or other items or the material of the substrate 16 (e.g., paper, plastic, glass) may be easily damaged by high temperatures, it is preferred that the air dryer 1 does not subject the substrate 16 to significant temperature increases. For example, in some applications, the maximum temperature that the substrate 16 can reach is 60°C. Figure 4Experimental data indicating the real-time temperature of substrate 16 as substrate 16 travels through air dryer 1 is shown. The experiment was conducted when conveyor 20 traveled at a speed of 1.7 m / s and the temperature of hot air jet 10 leaving air guide 8 (i.e., immediately downstream of air guide 8 in direction A) was about 200°C. It should be understood that at Figure 1 In the arrangement of , the temperature of the air leaving the air guide 8 is substantially the same as the temperature of the air guide 8 (e.g., near the air outlet 13). Therefore, the temperature of the air leaving the air guide 8 can be measured by using a temperature sensor to sense the temperature of the air guide 8. The wireless temperature sensor is attached to the top surface of the substrate 16 to continuously monitor the temperature of the substrate 16. Figure 4 It can be seen that as the substrate 16 travels through the contact zone with the hot air 10, the temperature of the substrate 16 increases from about 31°C to about 37.5°C. Figure 5 Further shown is the temperature increase of the substrate 16 at different temperatures of the air leaving the air guide 8. Again, the conveyor 20 travels at a fixed speed of 1.7 m / s. Figure 5 , the temperature rise of the substrate 16 increases with the temperature of the air leaving the air guide 8. When the temperature of the air is 250° C., the temperature rise of the substrate 16 is about 10° C. Therefore, the air dryer 1 is unlikely to cause a temperature rise of the substrate 16 that is large enough to cause concern.

[0120] refer to Figure 1 to Figure 2 , the air guide 8 is shown as a convergent nozzle, which means that the air outlet 13 of the air guide 8 has a smaller cross-sectional area than the air inlet 11 of the air guide 8. In this way, at the same volume flow, the air velocity at the air outlet 13 is greater than the air velocity at the air inlet 11. Figure 6 A practically used converging nozzle is shown, which can be used as an air dryer 1 ( Figure 1 ) of the air guide 8. Figure 6 In the example of FIG. 1 , the cross-sectional area of ​​the air inlet 11 is approximately 16 times the cross-sectional area of ​​the air outlet 13 .

[0121] Table 1 shows the Figure 6 The air guide 8 is used together with the air dryer 1 Figure 1 The experiment was conducted when the conveyor 20 was traveling at a speed of 1.7 m / s, and the laboratory conditions were an average of 21° C. and 60% relative humidity (RH). Under such conditions, the baseline natural drying time of the water-based ink applied by the continuous inkjet printer was about 25 seconds.

[0122] Table 1- Figure 6 The air guide 8 is used together with the air dryer 1

[0123]

[0124] Use a rubber ring wiper ( Figure 1 A set of pneumatic pistons (not shown in FIG. 1 ) determine the drying time of the inked image 18. The pneumatic pistons with rubber ring wipers are placed downstream of the air dryer 1 along the travel direction X of the substrate 16. The pneumatic pistons have individually adjustable time delays and are designed to imitate the rubbing of the inked image 18 by a thumb. If the inked image 18 is not smeared by the rubber wing wipers, it means that the inked image 18 is dry enough for subsequent processing.

[0125] In Table 1, the air speed refers to the speed of the hot air jet 10 downstream of the air outlet 13 relative to the conveyor 20. For simplicity, the air speed is considered to be the sum of the speed of the jet 10 (relative to the stationary printer 50) and the speed of the conveyor 20 (relative to the stationary printer 50), without taking into account the angle θ. In the case of a speed of the conveyor 20 of 1.7 m / s, the speed of the hot air jet relative to the printer 50 is 12 m / s, 16 m / s and 30 m / s in Table 1. The air temperature indicates the temperature of the hot air jet 10 immediately downstream of the air guide 8 along the direction A. The power consumption refers to the total power consumed by the air supply device 5 and the heating element 6 of the air dryer 1. The drying time refers to the drying time of the inked image 18 (which is printed with aqueous ink). It can be seen that using Figure 6 With the air guide 8 , the air dryer 1 can achieve a drying time of 5 seconds at a power consumption of less than 300 W (particularly 259 W and 290 W).

[0126] Table 2 - Using Air Dryer 1 without Converging Nozzle

[0127]

[0128] Comparative experiments were also performed under the same experimental setup (under which Table 1 was obtained), but without using Figure 6 In contrast, a nozzle with a much wider air outlet is used as the air guide 8. Table 2 shows various combinations of parameters obtained from the comparative experiments.

[0129] As shown in Table 2, in order to provide a drying time of less than 5 seconds, the power consumption of the air dryer 1 is much higher than in an arrangement involving the use of a converging nozzle as the air guide 8 .

[0130] By comparing Table 1 with Table 2, it can be seen that the use of a converging nozzle as the air guide 8 is beneficial to reducing the power consumption of the air dryer 1 at the same target drying time. This is because the air guide 8 (i.e., the converging nozzle) constricts the air flow from the housing 2. Therefore, in order to provide the same air speed, a lower volume flow rate is required from the air supply device 5, which therefore consumes less power. In addition, in order to generate and heat air with a lower volume flow rate, the working intensity of the air supply device 5 and the heating element 6 can be reduced, thereby extending the life of the air supply device 5 and the heating element 6. Smaller air outlets and lower total volume flow rates also mean that the heat and velocity of the air are reduced at a much shorter distance from the air guide 8. In addition, the restricted air flow provided by the air guide 8 will heat fewer surrounding components.

[0131] To provide significant power savings, the cross-sectional area of ​​the air inlet 11 may be at least 4 times the cross-sectional area of ​​the air outlet 13. More preferably, the cross-sectional area of ​​the air inlet 11 is at least 9 times the cross-sectional area of ​​the air outlet 13.

[0132] In the above example, the contraction of the air flow is mainly provided by the air guide 8. It should be understood that, further or alternatively, the housing 2 may be tapered to contract the air flow supplied by the air supply device 5 and / or heated by the heating element 6. For example, the housing 2 may have an outlet that is smaller than its inlet (where the air supplied by the air supply device 5 is received by the housing 2 and heated by the heating element 6). In this case, even if the air guide 8 has a non-contracting profile (for example, the air outlet 13 has the same size as the air inlet 11), the shape of the housing 2 itself may be sufficient to provide a contracting jet of hot air 10, thereby enabling power savings for the air dryer 1. In general, the contraction of the air flow through the air dryer 1 can be provided by making the air outlet 13 of the air guide 8 have a smaller cross-sectional area at or near the heating element 6 than the interior space 3 of the housing 1. In order to provide significant energy savings, the cross-sectional area of ​​the air outlet 13 of the air guide 8 may be up to 20%, 10%, 5% or 1% of the cross-sectional area of ​​the air inlet of the interior space (near the heating element 6). It should be understood that the above-mentioned “cross-sectional” area is perpendicular to the flow direction 30 ( Figure 1 ) plane limit. Figure 1 In the example of FIG. 5 , the flow direction 30 generally coincides with a center axis of the housing 2 and a center axis of the air guide 8 .

[0133] Furthermore, it should be understood that the size of the air outlet 13 of the air guide 8 can be selected based on the print width of the inkjet printer 50 (as described above). In order to maximize the efficiency of the air dryer 1, the hot air jet 10 width can be matched to the print width so that the hot air jet 10 does not substantially impact areas of the substrate 16 beyond the borders of the inked image 18. Typically, the width of the air outlet 13 can be between 0.5 and 2 times the print width. Figure 1 In the example of FIG. 5 , the printing width of the inkjet printer 50 is generally defined along a direction perpendicular to the direction X on the top surface of the substrate 16. Therefore, the width of the hot air jet 10 or the width of the air outlet 13 is defined along the same direction (ie, perpendicular to the directions A and X).

[0134] As described above, the drying time of the inked image 18 is affected by the contact time (and therefore the angle θ) between the inked image 18 and the hot air jet 10. The inventors of the present disclosure have discovered that the drying time of the inked image 18 is also affected by the following factors: (1) the temperature of the hot air jet 10; (2) the speed of the hot air jet 10 relative to the substrate 16; and (3) the distance between the air guide 8 and the print head 15. Figures 7 to 9 Describe this.

[0135] Figure 7 is a graph showing the effect of air temperature on drying time and substrate temperature. Figure 1 The settings are obtained Figure 7 data. Figure 7 The X-axis is the temperature of the hot air jet 10 in the direction A immediately downstream of the air guide 8 . Figure 7 The left Y-axis (“Drying Time”) is the drying time of the inked image 18 . Figure 7 The right Y-axis ("substrate temperature") is the temperature of the substrate 16. When the conveyor 20 travels at a speed of 1.7 m / s, the Figure 7 The data of the environment is 60% humidity and the speed of the hot air jet 10 downstream of the air guide 8 (relative to the stationary printer 50, regardless of the speed of the conveyor 20) is 2.7 m / s. Under such conditions, the baseline natural drying time of the water-based ink applied by the continuous inkjet printer is about 25 seconds. Figure 7 It is shown that as the air temperature increases, the drying time of the inked image 18 decreases significantly. When the air temperature is 250°C, the drying time of the inked image is about 4.75 seconds, which is an 81% reduction in the baseline drying time. Therefore, the temperature of the hot air jet 10 has a significant effect on the drying time of the inked image 18. Figure 7It is further shown that when the air temperature is 80° C., the substrate temperature is about 27° C., and when the air temperature is 260° C., the substrate temperature is about 40° C. Thus, while the temperature of the substrate 16 does increase with air temperature, the air temperature has little effect on the maximum substrate temperature produced. Figure 7 Confirmed Figure 4 and Figure 5 The finding is that the air dryer 1 is unlikely to cause a significant temperature increase of the substrate 16. The temperature of the hot air jet 10 downstream of the air guide 8 is preferably in the range between 250°C and 300°C in order to keep the substrate temperature low.

[0136] Figure 8 It is a graph showing the relationship between drying time and air speed. Figure 8 The data is for a large fan setting (which is similar to Figure 1 setting, but without shrinking the air guide 8). Figure 8 The X-axis ("air speed") is the speed of the hot air jet 10 generated by the air dryer 1 relative to the conveyor 20. For simplicity, the air speed is considered to be the sum of the speed of the hot air jet 10 (relative to the stationary printer 50) and the speed of the conveyor 20 (relative to the stationary printer 50) without taking into account the angle θ. The Y-axis ("drying time") is the drying time of the inked image 18. The test was conducted with air at 260°C. Figure 8 It is shown that the drying time is reduced by increasing the air speed. In particular, when the air speed increases from 3m / s to about 10m / s, the drying time is significantly reduced. Above an air speed of 10m / s, the drying time decreases slowly. Therefore, for Figure 8 For the setting, an air velocity of about 10 m / s is considered to be the optimum air velocity because it gives the greatest benefit at the lowest power consumption. It should be understood that the optimum air velocity may vary with the specific geometry of the air guide 8 used with the air dryer 1 (e.g., the cross-sectional dimensions of the outlet 13 of the air guide 8).

[0137] use Figure 1 The settings are obtained Fig. 9 It is a graph showing the relationship between the drying time (Y axis) of the inked image 18 and the distance D in the horizontal direction (X axis) between the air guide 8 and the print head 15. The test was conducted with hot air 10 at 200°C and an air speed of 16 m / s (relative to the static printer 50). Fig. 9It is shown that as the air dryer 1 is moved away from the print head 15, the drying time decreases. This is because the distance D affects the amount of time that the substrate 16 spends in the hot air jet 10. A greater distance D increases the contact time between the substrate 16 and the hot air jet 10, thereby reducing the drying time of the inked image 18. In general, there is a trade-off between the space required on the production line and the drying time. Furthermore, it will be appreciated that once the distance D reaches a sufficient level, the effect of the distance on the drying time will decrease. This is explained by Fig. 9 It is shown that the slope of the curve becomes flatter above 100mm. Generally, the distance D is preferably in the range between 30mm and 1500mm. More preferably, the distance D is in the range between 70mm and 300mm, and / or not less than 100mm.

[0138] Figures 10 to 12 An air dryer 1 b according to another embodiment is schematically shown.

[0139] and Figure 1 Elements of air dryer 1 that are identical to elements of air dryer 1b are identified using the same reference numerals. Elements that correspond to but are different from elements of air dryer 1 are identified using the same reference numerals, but for the sake of distinction, the letter "b" is used. The features and advantages described above with reference to the first embodiment generally apply to this embodiment.

[0140] The difference between the air dryer 1b and the air dryer 1 is that the air dryer 1b sprays a hot air jet 10b ( Fig.12 ) and cold air jet 27 ( Fig.12 ), the cold air jet 27 forms an air sheath around the hot air jet 10b.

[0141] In order to provide a cold air jacket, the inner space 3b of the housing 2 includes a first flow path 31 and a second flow path 32 separated by a divider 22. The air flow directions in the flow paths 31 and 32 are Fig.10 and Fig.11 The dotted arrow in FIG. 2 schematically shows the first flow path 31. The partition 22 is located in the housing 2 and is substantially cylindrical. In particular, the first flow path 31 is defined as a space surrounded by the partition 22, and the second flow path 32 is defined as a space between the partition 22 and the housing 2. In other words, the second flow path 32 surrounds the first flow path 31.

[0142] The air supply device 5 of the air dryer 1b supplies cool air from the surrounding environment to each of the first flow path 31 and the second flow path 32. Fig.10 and Fig.11As shown, the air splitter 29 is arranged between the air supply device 5 and the first flow path 31 and the second flow path 32. The air splitter 29 is conical, and the hole 21 extends through its side wall. The conical shape guides a part of the supplied air into the first flow path 31. The remaining part of the supplied air enters the second flow path 32 via the hole 21.

[0143] A heating chamber 30 surrounding a heating element (not shown) is located between the air diverter 29 and the first flow path 31. Therefore, the heating element heats the air entering the first flow path 31. However, the air entering the second flow path 32 does not pass through the heating element. Therefore, the heating element does not directly heat the air supplied into the second flow path 32. However, due to the heat exchange between the first flow path 31 and the second flow path 32, the temperature of the air in the second flow path 32 may still be slightly higher than the temperature of the air originally coming from the air supply device 5. Since the second flow path 32 surrounds the first flow path 31, the housing 2 of the air dryer 1b is safe for the user without the need for any heat insulating sleeve.

[0144] The air guide 8b of the air dryer 1b includes a first nozzle 25 and a second nozzle 26. The first nozzle 25 is in fluid communication with the first flow path 31. The space between the first nozzle 25 and the second nozzle 26 is in fluid communication with the second flow path 32. Fig.11 and Fig.12 As shown, each of the first nozzle 25 and the second nozzle 26 is similar to Figure 2 In addition, as shown in Fig.12 As shown in (b), the second nozzle 26 surrounds the first nozzle 25 and has a larger size than the first nozzle 25. As a result, the hot air from the first flow path 31 is ejected from the first nozzle 25 to form the hot air jet 10b. The unheated cold air from the second flow path 32 is ejected from the second nozzle 26 through the space between the side wall of the first nozzle 25 and the side wall of the second nozzle 26 to form the cold air jet 27. In this way, the cold air jet 27 forms an air sheath around the hot air jet 10b.

[0145] Air dryer 1b can be used with Figure 1 The air dryer 1 in the inkjet printing system 100 or Figure 3 In the embodiment of the present invention, the air dryer 1a in the inkjet printing system 100a of the present invention is used in a similar manner. In particular, the air guide 8b is angled so that the hot air jet 10b leaving the first nozzle 25 of the air guide 8b travels in a direction nearly parallel to the travel direction X of the substrate 16. Preferably, the cold air jet 27 travels in a direction substantially parallel to the travel direction of the hot air jet 10b. In addition, the cold air jet 27 preferably travels at a similar speed to the hot air jet 10b.

[0146] Surrounding the hot air jet 10b with the cold air jet 27 is useful for preventing ambient entrainment because the cold air jet 27 isolates the hot air jet 10b from the ambient atmosphere. This arrangement is also beneficial because less energy is required to accelerate the air jacket than to heat a larger volume of hot air. In addition, the cold air jet 27 is useful for increasing the length of the high speed and high temperature region of the hot air jet 10b. This will reduce the drying time of the inked image 18 because the effective drying length of the hot air jet 10b will be increased.

[0147] It should be understood that the first flow path 31 and the second flow path 32 and / or the air guide 8b may take forms different from those described above. Fig.10 and Fig.11 In the example of , the cold air jet 27 has an annular shape that completely surrounds the hot air jet 10b. It should be understood that the air guide 8b can be modified so that the cold air jet 27 partially surrounds the hot air jet 10b. In addition, the partition 22 separating the first flow path 31 and the second flow path 32 may not be airtight and may include holes. The partition 22 may not be cylindrical and / or may not share the same central axis of the housing 2. In other examples, the partition 22 may be replaced by a guide vane that produces a hot air jet flowing through the central area of ​​the interior space 3b; and the air guide 8b may be replaced by a flow straightener that ejects multiple parallel air jets, wherein the middle air jet is a hot air jet and the peripheral air jet is a cold air jet. The cold air jet generated by the flow straightener will substantially but not completely surround the hot air jet. In addition, the air splitter 29 may have a different design and may not be conical.

[0148] exist Fig.10 and Fig.11 In the example of the embodiment of the present invention, the heating element (enclosed by the heating chamber 30) is arranged in the inner space 3b of the housing 2. In order to achieve significant power savings and also to extend the life of the heating element (via the air flow contraction as described above), the cross-sectional area of ​​the air outlet of the first nozzle 25 (through which the hot air jet 10b leaves the air guide 8b) can be up to 20%, 10%, 5% or 1% of the cross-sectional area of ​​the heating chamber 30 (or the heating element).

[0149] Fig.13 The process steps of a method of drying an inked image (eg, inked image 18 ) printed on a substrate (eg, substrate 16 ) by an inkjet printer (eg, printer 50 ) are schematically illustrated.

[0150] In step S1 , air is supplied into an internal space (eg, the internal space 3 or 3 b ) of a housing (eg, the housing 2 ).

[0151] In step S2 , the air is heated, for example by means of a heating element 6 .

[0152] In step S3, a hot air jet (e.g., jet 10, 10a, or 10b) is directed to the inked image using an air guide (e.g., air guide 8, 8a, 8b) communicating with the interior space. The air guide is configured such that the hot air jet between the air guide and the substrate forms an angle between 0 and 30 degrees relative to the direction of travel of the substrate (e.g., direction X). The definition of the angle is similar to that described above with respect to Figure 1 and Figure 3 Definition of the angle θ.

[0153] It should be understood that the steps may be performed in a different time sequence than that described. For example, step S2 may be performed before step S1 and / or simultaneously with step S1.

[0154] Fig.14 The process steps of a method of drying an inked image (eg, inked image 18) printed on a substrate (eg, substrate 16) using water-based ink by an inkjet printer (eg, printer 50) are schematically illustrated.

[0155] In step M1 , hot air (eg, hot air jets 10 , 10 a or 10 b ) is generated and directed toward the inked image to dry the inked image within 10 seconds using less than 500 watts of power consumption.

[0156] Optionally, hot air can be generated and directed toward the inked image to dry the inked image in less than 5 seconds using less than 300 watts of power consumption.

[0157] Step M1 may include sub-steps such as steps S1 to S3 described above.

[0158] Although the air dryer described in the present disclosure is particularly advantageous for use with a continuous inkjet printer operating with a water-based ink, it should be understood that the air dryer can be used with other types of inkjet printers (e.g., drop-on-demand inkjet printers) and / or other types of inks (e.g., low volatility inks) to reduce the drying time of a printed ink image. Low volatility inks (especially inks in which a mixture of water and volatile organic compounds acts as a solvent) can be used to reduce the amount of CMR / VOCs that evaporate into the environment during operation of the inkjet printer. The drying time of the low volatility ink can be at least 2 seconds, 5 seconds, 10 seconds, 15 seconds, or 20 seconds at room temperature (e.g., 25° C.) under ambient conditions (e.g., 60% RH, no active heating or air flow), depending on the percentage of volatile organic compounds in the mixture. In terms of ink compositions, the low volatility ink may contain at least 50% by weight of water, or less than 20% by weight (or more preferably less than 10% by weight or 5% by weight) of volatile organic compounds (e.g., methyl ethyl ketone). Air dryers can also be used with highly volatile or fast drying inks (eg, MEK or ethanol based inks) if there is a need to further reduce the drying time of these inks in order to increase the line speed of the production line.

[0159] In addition, although the above-described embodiments heat and direct hot air to the inked image, it should be understood that other types of gases (e.g., N2, CO2) may be used in a similar manner to accelerate the drying time of the inked image. In this case, the above-described terms "air dryer," "air supply," "air guide," "hot air jet," and "cold air jet" may be more generally referred to as a dryer, a gas supply, a gas guide, a hot gas jet, and a cold air jet, respectively.

[0160] The terms "having", "containing", "including", "comprising" and the like are open ended, and these terms indicate the presence of stated structures, elements or features, but do not exclude the presence of additional elements or features. The articles "a", "an" and "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0161] Those skilled in the art will appreciate that in the foregoing description and the appended claims, positional terms such as "top", "horizontal", "vertical", etc. are made with reference to conceptual illustrations of inkjet printing systems, such as those shown in the accompanying drawings. These terms are used for ease of reference and are not intended to be limiting. Therefore, these terms should be understood to refer to elements when in the orientation as shown in the accompanying drawings.

[0162] Although the present disclosure has been described in terms of the preferred embodiments described above, it should be understood that these embodiments are illustrative only and the claims are not limited to those embodiments. In view of this disclosure, those skilled in the art will be able to make modifications and substitutions, which are considered to fall within the scope of the appended claims. Each feature disclosed or shown in this specification may be combined in the present disclosure, either alone or in any appropriate combination with any other features disclosed or shown herein.

Claims

1. An air dryer for use with an inkjet printer, the inkjet printer comprising a print head for applying an inked image to a substrate, wherein the air dryer comprises: a housing enclosing an interior space therein; an air supply device configured to supply air into the interior space of the housing; a heating element configured to heat the air; and An air guide connected to the internal space is used to guide a hot air jet to the inked image on the substrate so as to dry the inked image, and wherein the air guide is configured so that the hot air jet between the air guide and the substrate forms an angle between 0 degrees and 30 degrees relative to the travel direction of the substrate.

2. The air dryer of claim 1, wherein the air guide comprises a nozzle.

3. An air dryer according to claim 1 or 2, wherein the angle is between 0 degrees and 20 degrees.

4. An air dryer according to any one of the preceding claims, wherein the angle is about 10 degrees.

5. An air dryer according to any one of the preceding claims, wherein the air guide comprises a tubular structure through which the hot air jet leaves the interior space, and wherein the tubular structure forms an angle between 0 and 30 degrees relative to the direction of travel of the substrate.

6. An air dryer according to any one of the preceding claims, wherein the air guide is configured such that a jet between the air guide and the substrate has a velocity component opposite to the direction of travel of the substrate.

7. An air dryer according to any one of the preceding claims, wherein the air guide comprises an air outlet from which the hot air jet leaves the air guide and wherein the cross-sectional area of ​​the air outlet is smaller than the cross-sectional area of ​​the interior space of the housing. 8 . The air dryer according to claim 7 , wherein a width of the air outlet is 0.5 to 2 times a printing width of the inkjet printer.

9. An air dryer according to any one of the preceding claims, wherein the air guide comprises a converging nozzle.

10. An air dryer according to any one of the preceding claims, wherein the hot air jet downstream of the air guide has a temperature between 200°C and 350°C.

11. The air dryer of claim 10, wherein the hot air jet downstream of the air guide has a temperature between 250°C and 300°C.

12. An air dryer according to any one of the preceding claims, wherein the jet of hot air downstream of the air guide has a velocity of no more than 50 m / s relative to the print head.

13. An air dryer according to any one of the preceding claims, wherein the air guide is spaced apart from the print head by approximately 30 mm to 1500 mm along the direction of travel of the substrate.

14. An air dryer according to any one of the preceding claims, wherein the air guide is spaced apart from the print head by at least 100 mm in the direction of travel of the substrate.

15. An air dryer according to any one of the preceding claims, wherein: The interior space of the housing includes a first flow path and a second flow path, and the air supply device is configured to supply air to both the first flow path and the second flow path; the air dryer being configured such that air supplied to the first flow path flows through the heating element to produce the hot air jet, and air supplied to the second flow path does not flow through the heating element to produce the cold air jet; and The air guide is configured to guide the hot air jet and the cold air jet out of the interior space.

16. The air dryer of claim 15, wherein the air dryer is configured such that the cool air jet travels at substantially the same speed as the hot air jet.

17. An air dryer according to claim 15 or 16, wherein the air dryer is configured so that the cool air jet travels in a direction substantially parallel to the direction of travel of the hot air jet.

18. An air dryer according to any one of claims 15 to 17, wherein the air dryer is configured such that the cold air jet at least partially surrounds the hot air jet.

19. An air dryer according to any preceding claim, further comprising a mounting arrangement to which the housing is mounted.

20. An air dryer according to any one of the preceding claims, wherein the inkjet printer is a continuous inkjet printer.

21. An air dryer according to any one of the preceding claims, wherein the inkjet printer uses low volatility inks.

22. An air dryer according to any one of the preceding claims, wherein the inkjet printer uses water-based inks.

23. An inkjet printing system comprising: An inkjet printer comprising a printhead for applying an inked image to a substrate; An air dryer according to any preceding claim; and A conveyor is provided for moving the substrate past the print head and the air dryer.

24. A method of drying an inked image printed on a substrate by an inkjet printer, comprising: supplying air into the interior space of the housing; Heating the air; and The hot air jet is directed to the inked image using an air guide in communication with the interior space, wherein the hot air jet between the air guide and the substrate forms an angle between 0 and 30 degrees relative to a direction of travel of the substrate.

25. A method of drying an inked image printed on a substrate by an inkjet printer using a water-based ink, the method comprising: Using less than 500 watts of power consumption, hot air is generated within 10 seconds and directed to the inked image to dry the inked image.

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