BACKGROUND

[1] Substrates like textiles may have a surface product, such as lint or textile fibers on their respective surfaces. This surface product of the substrate may form an irregular surface structure which may affect a printing quality in direct to garment applications because ink may be applied in a non-uniform layer on the irregular surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[2] For the purpose of illustration, certain examples will now be described with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic illustration of a conditioning device according to an example in a side view;

Fig.2 shows a schematic illustration of a conditioning device according to an example in a top view;

Fig.3 shows a schematic diagram illustrating a method according to an example; and

Fig.4 shows a schematic diagram illustrating a computer-implemented method according to an example

DETAILED DESCRIPTION

[3] In the following detailed description, reference is made to the accompanying drawings. The examples in the description and drawings should be considered illustrative and are not to be considered as limiting to the specific example or element described. Multiple examples may be derived from the following description and/or drawings through modification, combination or variation of certain elements. Furthermore, it may be understood that also examples or elements that are not literally disclosed may be derived from the description and drawings by a person skilled in the art. Whereas different examples are described herein, it is understood that features of these examples may be used individually or in combination thereof to derive further variations beyond those explicitly describes herein. [4] Fig. 1 shows an example of a conditioning device 100 for removing a surface product L of a substrate S. The surface product may be lint and textile fibers which may be considered as artifact of a substrate and may comprise small and loosely attached or loose filaments extending from the substrate. Lint and fibers further may be considered part of the substrate itself as they originate from the material of the substrate.

[5] The conditioning device too comprises a conductive plate 10, a conductive head 20 and a high voltage generator 30. The conductive plate 10 may receive a substrate S. The conductive plate has a width in an x direction and a length in a y direction. The vertical direction is designated as z.

[6] The conductive plate 10 may be electrically connected to ground (GND). The GND connection may be located at a bottom side of the conductive plate 10 or at any other suitable location. Further, the conductive plate 10 may be a metal plate or may comprise metal, for example a sheet metal. The GND connection may be in the form of a terminal, like a plug. A further terminal may be provided at the conductive plate 10 for connecting the high voltage generator 30. This may also be in the form of a plug, see connection 31 in Fig. 1. In an alternative, the conductive plate is not directly connected to the high voltage generator 30 but both the conductive plate 10 and the high voltage generator 30 are connected to GND or another reference potential.

[7] In the example of Fig. 1, the conductive head 20 may have at least one voltage output or multiple voltage outputs 25, as shown in Fig. 1. The voltage outputs 25 may be in the form of metal tips regularly spaced from one another, arranged on a downward facing surface of the conductive head 20. The multiple voltage outputs 25 may be arranged in an array including one or a plurality of rows which may form a matrix of voltage outputs 25. The multiple voltage outputs 25 may be evenly spaced in one or two directions of the array. Fig. 1 shows one row of five voltage outputs 25 which are arranged in a direction extending along the width direction x of the conductive plate 10. The multiple voltage outputs 25 may have the same or a similar shape, for example the shape of a conical or tapered metal tip. Further, the dimensions of each of the multiple voltage outputs 25 in the x, y and/or z directions may be the same. In particular, the metal tips of the multiple voltage outputs 25 may have a same length in the z direction. Thus, a distance G, also referred to as air gap, between the multiple voltage outputs 25 arranged on the conductive head 20 and the substrate S located on the conductive plate 10 may be the same for all of the multiple voltage outputs 25.

[8] A spacer (not shown) may be provided between each of the multiple voltage outputs

25 to isolate the respective voltage outputs 25 from each other and to prevent a current breakthrough from one voltage output 25 to an adjacent one. For example, each of the multiple voltage outputs 25 may have a spacer in the form of an isolation layer for electrically isolating the voltage outputs 25. For example, the isolation layer may surround each one of the voltage outputs 25, respectively. The tip of the voltage outputs 25 is exposed from the isolation layer.

[9] In the example of Fig. 1, the high voltage generator 30 is electrically connected between the conductive plate 10 and the conductive head 20. The high voltage generator 30 is to generate and apply a voltage between the conductive plate 10 and the conductive head 20. For example, the high voltage generator 30 may be connected via connection 31, e.g. a low potential connection, to the conductive plate 10 and via connection 32, e.g. a high potential connection, to the conductive head 20. Alternatively, the high voltage generator 30 is not directly connected to the conductive plate 10 but both the conductive plate 10 and the high voltage generator 30 are connected to GND or another reference potential via separate connections.

[10] The high voltage generator 30 may be a stand-alone device external to the conductive head 20 and connected thereto via a terminal. This may be in the form of a plug, see connection 32 in Fig. 1. The high voltage generator 30 also may be provided within the conductive head 20. In Fig. 1 an external high voltage generator 30 is shown for illustration purposes. Nevertheless, the high voltage generator 30 may form part of or be located in a carrier (not shown) of the conductive head 20 and the conductive head 20 may thus house the high voltage generator 30. Thus, the high voltage generator 30 may form an integral part of the conductive head 20.

[11] In some examples, the high voltage provided by the high voltage generator 30 may range from 1 kV to 100 kV, or from 1 kV to 30 kV, for example. Further, the power provided by the high voltage generator 30 may range from 1 W to 100 W, or 1 W to 30 W, for example. Thus, a current generated based on the voltage output of the high voltage generator 30 may be in the range of 1 mA to 100 mA, or 1 mA to 30 mA, for example, as describe in further detail below. An intensity of the discharge current can be modulated by adapting the high voltage and the distance G. In different examples, the distance G between the high voltage outputs 25 and the substrate S may be between 1 mm and 10 mm, more specifically between 2 mm and 5 mm.

[12] In the example of Fig. 1, the conditioning device 100 provides a pretreatment of the substrate S to prepare the substrate S for printing. The substrate may bea textile, fabric or garment, for example, comprising natural fibers. Examples for natural fibers are wool, silk, camel hair, angora, cotton, flax, hemp, and jute. Examples of garments are T-shirts, sweaters, jackets, shorts and the like. A textile also may be provided in the form of a sheet or in the form of a continuous web which is fed from a textile supply roll. The pretreatment may be an operation to remove lint and surface fibers from the substrate S to generate a smooth surface area for printing.

[13] In the example of Fig. 1, the substrate S to be treated, comprises a main substrate layer B and a surface layer L. The main substrate layer B includes bound or densely distributed fibers in a woven, non-woven, knitted or similar arrangement. The surface layer L includes loosely arranged or loose fibers or lint described herein as surface product L or artifact extending and/or formed from the main substrate layer B of the substrate S. In one example, a fiber density of the main substrate layer B is at least 10 times, or even at least 20 or 100 times, higher than a fiber density of the surface layer L. Due to the difference in fiber density, the surface layer L has a lower thermal mass than the main substrate layer B. Consequently, an ohmic resistance of the surface layer L is also lower than an ohmic resistance of the main substrate layer B. For example, the ratio of thermal mass between the main substrate layer B and the surface layer L is between 10 and 100. Similarly, the ratio of ohmic resistance between the main substrate layer B and the surface layer L is between 10 and 100.

[14] In the example of Fig. 1, the substrate S is placed on the conductive plate 10 between the conductive head 20 and the conductive plate 10. In one example, dimensions of the conductive plate 10 may be such that at least a substrate Sofa size of a regular T-shirt may be received. For example, at least one of a width and a length of the conductive plate 10 may be between 0.5 meters and 5 meters or between 0.5 meters and 2 meters. In Fig. 1, the length of the substrate may be defined in the y direction and the width may be defined in the x direction. The conductive plate 10 may be substantially plane or flat. The substrate S is provided on the conductive plate 10 so as to provide a substantially plane substrate surface on the conductive plate 10.

[15] In the example of Fig. 1, the at least one or multiple voltage outputs 25 may have a fixed relation to the substrate S and the conductive plate 10, such as a fixed distance G, during a pretreatment of the substrate S. The pretreatment may comprise providing the at least one or multiple voltage outputs 25 with the high voltage and setting a distance G between the at least one or multiple voltage outputs 25 and the substrate S. When the high voltage is applied, an electrical discharge in the form of an electric arc is generated in an air gap between the voltage outputs 25 and the substrate S. The electrical discharge generates a discharge current that flows through the fibers and lint in the surface layer L. Due to the relativdy low electric impedance of the fibers and lint, the current can be relatively high, such as in the order of 30-100 mA, or any maximum or dose to maximum current to be generated by the high voltage generator 30, which generates local heat suffident to bum the low impedance lint and fibers of the surface layer L. Once the current reaches the higher density main substrate layer B, the current is divided across a larger number of fibers and is reduced by the higher mass and hence higher impedance of the material in the main substrate layer until it reaches the conductive plate 10. Due to the fiber density difference between the surface layer L and the main substrate layer B, a higher current and more heat is generated in the surface layer L so that lint and fibers of the surface layer L are burnt while lower currents and less heat are generated in the bound or densely distributed fibers of the main substrate layer B which hence remains substantially unaffected.

[i6] By controlling the high voltage to be applied via the high voltage outputs 25 and the distance G between the voltage outputs 25 and the top surface of the substrate S, the intensity of the current and hence the heat to be generated and the burning effect can be modulated and can be adapted to different types of substrate material.

[17] Fig. 2 shows another example of a conditioning device 200 for removing the surface product L in a predetermined area A of the substrate S in a top view. The predetermined area A is shown as a heart shape in Fig. 2. The conditioning device 200 can comprise a conditioning device 100 as described with respect to Fig. 1 and can further comprise a 2-axis carriage 42. The 2-axis carriage is to move the conductive head 20 in two dimensions parallel to and above the conductive plate 10. The 2-axis carriage may comprise an x-axis guide bar to guide and move the conductive head 20 along the width direction x of the conductive plate 10. Further, the 2-axis carriage may comprise two y-axis guide bars 44 to support the x-axis guide bar and to guide and move the conductive head 20 along the length direction y of the conductive plate 10. Further, the 2-axis carriage may comprise a carriage device, a drive unit and a control unit to carry and control the movement of the conductive head 20. Thus, the conductive head 20 may be arranged moveably in the x and y directions over the conductive plate 10.

[18] During the parallel movement at the set distance G between the conductive head 20 and the substrate S, the high voltage provided by the high voltage generator 30 may also be set to a fixed voltage value.

[19] In one example, the conductive head 20 may have a single voltage output 25. The conductive head 20 may be scanned along the width direction x of the conductive plate 10 by means of the 2-axis carriage 42 across a strip portion of the substrate S between left- and right-hand boundaries (as seen in Fig. 2) of the predetermined area A. A strip portion may be defined as a row or swath along the width direction x of the conductive plate 10.

[20] After scanning one strip portion, the conductive head 20 may be moved along the length direction y of the conductive plate 10 in order to arrange the conductive head 20 for scanning a next adjacent strip portion between left and right-hand boundaries of the predetermined area A. The offset between two subsequent strip portions may be in the order of about 1 cm, for example The scanning speed may be in the order of 100-200 cm/s, for example. This procedure may be repeated until the predetermined area A has been fully scanned by the conductive head 20. Scanning in the x direction may be performed both from left to right and from right to left (as seen in Fig. 2).

[21] The scanning of one strip portion may be performed eontin uously or in steps. During continuous scanning, the single voltage output 25 of the conductive head 20 may continuously output the high voltage and scan across the substrate to generate an electric discharge which moves along the x direction. During stepwise scanning, the single voltage output 25 may intermittently output the high voltage after each scanning step for a specific time interval, for example for a duration of between 0.1 ms and 10 ms. The specific time interval is a time in-between two consecutive steps. The stepwise scanning may be performed in steps having a step width in the range of about 1 cm, for example.

[22] In another example, the conductive head 20 may have a plurality of voltage outputs 25 which are arranged in an array along the width direction x of the conductive plate 10. For example, a width of the array may extend across the width of the substrate S, the width of the predetermined area A or the entire width of the conductive plate 10. Further, the width of the array may be larger than the width of the substrate S, or the width of the predetermined area A or the width of the conductive plate 10. At least a subset of the plurality of voltage outputs 25 may be successively or simultaneously provided with the high voltage to scan across a strip portion of the substrate S between left- and right-hand boundaries of the predetermined area A. If the width of the array of voltage outputs 25 is at least as large as the width of the predetermined area A to be treated, the array of voltage outputs can be positioned above and aligned to the predetermined area by moving the carriage in the x and y directions and then a strip portion of the substrate is scanned by successively or simultaneously applying the high voltage to the high voltage outputs 25 of the array.

[23] After scanning the strip portion, the conductive head 20 may be moved along the length direction y of the conductive plate 10 for scanning a next adjacent strip portion between the left- and right-hand boundaries of the predetermined area A. This procedure may be repeated until the entire predetermined area A has been scanned by the conductive head 20. The subset of the plurality of voltage outputs 25 may be selected separately for each strip portion so as to scan strips portions of different width depending on the shape of the predetermined area A

[24] In another example, the conductive head 20 may have a plurality of voltage outputs

25 which are arranged in a matrix along the width and length directions of the conductive plate 10. An extent of the matrix in width and length directions may be larger than an extent of the predetermined area A of the substrate S. In this case, the array of voltage outputs can be aligned to and positioned above the predetermined area using the 2-axis carriage 42, and at least a subset of the plurality of voltage outputs 25 may be successively or simultaneously provided with the high voltage to scan across the predetermined area A between the boundaries of the predetermined area A

[25] In another example, an extent of the matrix in the length and width directions of the conductive plate may be smaller than an extent of the predetermined area A of the substrate S. In this case, the array of voltage outputs can be aligned to and positioned above a portion of the predetermined area using the 2-axis carriage 42, and the portion of the predetermined area A of the substrate S may be scanned by successively or simultaneously providing the plurality of voltage outputs 25 with the high voltage. After scanning the portion of the predetermined area A, the conductive head 20 can be moved along the length and/or width directions of the conductive plate 10 using the 2-axis carriage 42 in order to locate the conductive head 20 above a next portion of the predetermined area for scanning a next portion between boundaries of the predetermined area A The next portion may be scanned by at least a subset of the plurality of voltage outputs 25 depending on the size of the area to be scanned. This procedure may be repeated until the entire predetermined area A has been scanned by the conductive head 20.

[26] In another example, where the conductive head comprises a voltage output array having a width spanning the width of the conductive plate 10, also designated as page wide array, or a designated treatment area thereof, the conductive head can be provided on a y- axis carriage for movement in the y direction. Scanning in the x direction could be performed by sequentially or simultaneously activating the high voltage outputs and scanning in the y direction can be performed by moving the carriage in the y direction.

[27] In a further example, the conditioning device may comprise a feed mechanism to feed a substrate in the form of a sheet or continuous web through a treatment zone, e.g. in the lengthwise direction y, with the conductive head located above the treatment zone. The conductive head may comprise a page wide voltage output array or maybe located on an x- axis carriage for scanning in the x direction.

[28] The conditioning device too or 200 may be a stand-alone device to which the substrate is supplied and from which the substrate is taken after treatment. In another example, the conditioning device 100 or 200 may be part of a processing line wherein it may be located upstream of printer, for example. In still a further example, the conditioning device 100 or 200 can be part of a printer, with the conductive head to be located on a printer carriage. The substrate can be treated within the printer either by first treating the entire predetermined area A and then printing an image in the area A, or by sequentially treating and printing subsequent stripe portions. In the latter case, the conductive head could be arranged on the carriage together with printheads, upstream from the printheads.

[29] Fig.3 shows a schematic diagram illustrating a method for removing a surface product L of a substrate S. Reference is made to Fig. 1 and 2 where applicable. The surface product L of the substrate S can be surface fiber or lint on a surface area A of the substrate S.

[30] In the example of Fig.3, the substrate can be provided, at 110, on a conductive plate 10. For example, the substrate S can be laid on the conductive plate 10 by hand or by automatically placing the substrate S on the conductive plate 10. The conductive plate 10 may be connected to ground (GND), for example o V. However, the conductive plate 10 also can have a different electric reference potential.

[31] In the example of Fig. 3, a head 20 may be provided above the substrate S, at 120. The head 20 may have at least one voltage output 25, but may also have multiple voltage outputs 25. The at least one or the multiple voltage outputs 25 may be conductive, for example comprise a metal. Also, the head 20 may have a single voltage output 25. The at least one voltage output 25 may have an electrical tip for generating an electric field at the tip. The head 20 may be provided such that a surface of the substrate S provided on the conductive plate 10 faces the at least one voltage output 25 or the multiple voltage outputs 25. The head 20 may be provided over the conductive plate 10 at a specific distance from the conductive plate 10. In particular, the head 20 may be moveably arranged opposite the conductive plate 10 such that the head 20 can scan across an area A to be treated.

[32] In the example of Fig.3, a high voltage may be provided between the conductive plate

10 and the at least one voltage output 25. The high voltage may be provided by a voltage generator 30 having terminals 31, 32 to electrically connect the high voltage generator to the conductive plate 10 and to the at least one voltage output 25, respectively. The high-voltage may range from 1 kV to 100 kV, or 1 kV to 30 kV, for example. In particular, the potential at the at least one voltage output 25 may be considered as the high potential. The potential at the conductive plate 10 may be considered as the low potential.

[33] The method may further comprise adapting 130 a distance between the conductive plate 10 and the at least one voltage output 25 as a function of a thickness and material of the substrate. The thickness may be defined as a sum of layer heights of layers L and B or a height of layer B as shown in Fig. 1. The distance between the conductive plate 10 and the at least one voltage output 25 may be set such that the distance G between the surface of the substrate S and the at least one voltage output 25 may range from 1 mm to 6 mm. In another example, the distance G may range from 2 to 5 mm.

[34] The method further comprises treating, at 140, the surface area A of the substrate S by burning the surface product L of the substrate S from the surface area A Burning of the surface product L as part of treating 140 can be a result of discharging a current through the surface product L of the substrate S as a function of the high voltage and the distance between the at least one voltage output 25 and the conductive plate 10 or the substrate S. The surface area A may be a limited or predetermined area, which may to be printed after the pretreatment by the conditioning device 100 or 200. The current to be discharged through the substrate S can be controlled in order to have the surface product L burnt but not the bound fibers of the substrate S (in layer B). An intensity of a discharge current can be modulated by controlling the high voltage and the distance G between the substrate S and the at least one voltage output 25

[35] After the surface product L has been burnt, the method may comprise printing 150 an image on the substrate S in the treated surface area A Since the surface area A has been treated by burning any lint and fibers on the substrate surface, the treated surface area A becomes flat and smooth and any image printed thereon may have a uniform constitution.

[36] Fig.4 shows an example of a computer-implemented method. Reference is made to

Fig. 1 and 2 where applicable. The computer-implemented method comprises controlling 210 a conductive head 20 to move parallel to a conductive plate 10 across a limited area A of a substrate S received on the conductive plate 10. The method may comprise controlling the 2- axis table 42 as described with respect to Fig. 2 above, for example. Further, the method comprises controlling 220 a high voltage generator 30 to apply a high voltage between the conductive head 10 and the conductive plate 10 to cause a discharge current to flow through the substrate within the limited area A to bum the artifact L from the substrate surface in the limited surface area A. Then, a printer is instructed 230 to print an image in the limited surface area A. Thus, a uniform printed image can be provided.

[37] Experiments have shown that the method and device described herein can safely remove lint and surface fibers from a textile substrate without damaging the bulk of the substrate. In the treated area the texture of the substrate can be perceived more clearly. The method and device can be selective in that portions of the substrate not to be treated remain unaffected. For example, a soft and “hairy” textile will preserve its soft touch and feel outside of treated areas. Further, the method is compatible with most features and protrusions of the substrate, such as knitting patterns, decorative stitching, ornamental or functional seams, buttons, applk^fes and the like, except for electrically conductive elements.

[38] The result of the pretreatment is very uniform and provides a smooth and flat surface suitable for printing an image thereon. The processing time is relatively low, such as less than a minute, depending on the size of the area to be treated. Treatment consumes little energy and no other resources, such as water or other treatment fluids. Costs and complexity are low.

[39] Further, the conditioning device can be integrated in a printer and make use of printer equipment, such as a substrate holding mechanism, substrate feed mechanism and a carriage mechanism.

[40] The statements set forth herein under use of hardware circuits, software or a combination thereof may be implemented. The software means can be related to programmed microprocessors or a general computer, an ASIC (Application Specific Integrated Circuit) and/or DSPs (Digital Signal Processors). Whereas some details have been described in terms of a computer-implemented method, these details may also be implemented or realized in a suitable device, a computer processor or a memory connected to a processor, wherein the memory can be provided with one or more programs that perform the method, when executed by the processor.