The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in order to provide what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
In the drawings:
The principles and operation of a printing apparatus according to the present invention may be better understood with reference to the drawings and accompanying description.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
The present invention relates to a digital printing system for various substrates that permits accurate, high quality, high resolution, multi-color printing directly onto a substrate in a relatively simple system. A preferred embodiment of the present invention is useful for printing over materials that usually cause the ink to smear over the material, such as fibrous materials, porous materials and other ink absorbing materials, and materials having high surface tension with the ink liquid. A preferred embodiment of the present invention is thus provided for the garment industry in general, and for T-shirt printing industry in particular.
A preferred embodiment of the present invention comprises
A pre-printing assembly for wetting the substrate prior to printing. This wetting sub-system typically comprises an array of spraying nozzles operative to apply a wetting composition over the printed material. This wetting composition interferes with the engagement of the ink with the printed material so as to limit the spread of the ink over, or within, the material;
The abovementioned wetting assembly and printing assembly preferably comprises of one or more units capable of applying liquid over selected areas of the material to be printed. Such units are known in the art as spraying nozzles, dripping nozzles, droplet injectors, drop-on-demand piezoelectric inkjet nozzles, continuous piezoelectric inkjet nozzles, roller pads, stamping pads, offset printing stencil and a screen printing stencil, etc.
The abovementioned garment handling assembly preferably comprises an accurate X, Y, Z motion system and a printing table. Since the printing system is particularly suited to printing on a garment, it has been described herein with respect to garment printing, by way of example only. However, it will be appreciated that any other suitable substrate can alternatively be utilized.
A preferred embodiment of a digital printing system according to the present invention typically comprises electronically controlled wetting and printing units such as spraying nozzles, dripping nozzles, droplet injectors, drop-on-demand piezoelectric inkjet nozzles, continuous piezoelectric inkjet nozzles, etc. that are capable of creating image pixels in a controllable manner.
A preferred embodiment of the present invention shown and described below comprises the combination of wetting by spraying technology and printing by inkjet technology. It is appreciated that the present invention pertains to every possible combination of wetting technology and printing technology.
The digital printing system has the following advantages over conventional screen-printing devices:
Reference is now made to
Perpendicular to the X-axis direction, an accurate linear motion Y-axis stage 14 is installed above the printing table assembly 13, preferably on a bridge 15. The X-axis 12 and the Y-axis 14 stages are known in the art as linear stages, such as linear rails, like rails marketed by THK Co., Ltd., Tokyo, Japan, a linear encoder like that sold by RSF Elektronik Ges.m.b.H., Tarsdorf, Austria, and a moving plate supported on the rails. According to a preferred embodiment of the invention, the X-axis stage 12 is a linear motor driven stage, capable of high acceleration rate and stiffness, for example, Anorad brand model LW10 of Rockwell Automation, Shirley, New York, USA. Closed loop control is responsible for the high accuracy and motion smoothness. The position of the printing table 13 along the rails of the X-axis stage 12 is measured by a linear encoder, and is used also to determine the firing timing of the inkjet nozzles and the wetting nozzles. The Y-axis stage 14 is preferably a linear motor stage similar to the X-axis stage 12.
A printing head 16, preferably comprising a plurality of inkjet nozzles, is connected to a vertical Z-axis system 17, which is preferably a ball screw driven stage. The Z-axis stage 17 is supported on an Y-axis moving plate 18, to allow motion perpendicular to the direction of movement of the printing table 13. The gap between the printing heads array 16 and the printed surface on the printing table assembly 13 is an important parameter for high quality printing. The Z stage 17 enables movement of the printing heads array 16 in the vertical direction for calibration for different media heights.
It is appreciated that any other ink applying apparatus can be used for the printing head 16, such as a dripping nozzle, a droplet injector, a drop-on-demand piezoelectric inkjet nozzle, a continuous piezoelectric inkjet nozzle, a roller pad, an offset printing stencil and a screen printing stencil.
It is also appreciated that, while the system is particularly suited for printing on a finished garment, other media can alternatively be employed. The present invention will be described with regard to a finished garment, for ease of description by way of example.
The printing system 10 optionally comprises an ironing unit 19 and also optionally comprises a curing unit 20. The ironing unit 19 is preferably supported on the frame 11 above the X-axis stage 12, preferably on a bridge, such that the printing table assembly 13 can move underneath. The ironing unit 19 prepares the media for printing, as will be further explained in detail below. The curing unit 20 is preferably supported on the bridge 15 over the rigid frame 11. Alternatively, the curing unit 20 can be mounted over a separate bridge in a similar manner to the ironing unit 19. According to one embodiment of the present invention the curing unit 20 is an infrared heating unit that evaporates the ink carrier as printing is accomplished or during print passes. According to another embodiment of the present invention the curing unit 20 is a hot air blower. Alternatively, any other curing unit can be utilized, which is suited to the type of ink printed on the garment.
A main computer 21, preferably a microprocessor, controls the entire system, and is coupled to each of the various units for coordination, synchronization, and activation, in accordance with a pre-programmed printing process. Main computer 21 coordinates a large number of functions. It receives images from an image file, processes the images to be printed, activates the curing unit, and controls the motion systems, the ironing unit, and more. Preferably, movement of the X-axis and the Y-axis stages is coordinated by the microprocessor with the nozzles firing command by a print heads controller, so that precise printing of a desired object or symbol can be performed. In a preferred embodiment of the present invention, computer 21 is augmented with a programmable logic controller (PLC), later shown and described in accordance with
Reference is now made to
Reference is now made to
Reference is now made to
It is appreciated that the wetting the garment prior to printing limits the penetration of the ink into the garment so that a larger amount of ink remains on the external, visual, layers of the fabric, and that the printing head is thereafter capable of creating smaller dots of ink. Therefore the printed image has a higher quality, through higher resolution and stronger colors.
It is also appreciated that the method and the apparatus for wetting the garment can be alternatively used to coat any other surface that is capable of absorbing the ink, or that has a relatively high surface tension with the ink liquid, so as to limit the smearing of the ink through, or over, the surface.
It is further appreciated that the spraying nozzle 19 can be replaced by other means for applying liquid onto a surface, such as a dripping nozzle, a droplet injector, a drop-on-demand piezoelectric inkjet nozzle, a continuous piezoelectric inkjet nozzle, a roller pad, an offset printing stencil and a screen printing stencil.
It is additionally appreciated that the printing head 16 can be replaced by other means for applying ink onto a surface, such as a dripping nozzle, a droplet injector, a drop-on-demand piezoelectric inkjet nozzle, a continuous piezoelectric inkjet nozzle, a roller pad, an offset printing stencil and a screen printing stencil, in any possible combination of wetting technology and printing technology. Such possible combinations include, but are not limited to:
Wetting using dripping and printing using drop-on-demand piezoelectric inkjet nozzle;
Wetting using roller pad and printing using continuous piezoelectric inkjet nozzle;
Wetting using spraying and printing using screen printing stencil; and
Wetting using droplet injector and printing using inkjet nozzle.
Reference is now made to
Reference is now made to
Reference is now made to
After mounting the garment on the printing table 13, as will be described in further details below, the operator instructs the computer 21 to start the printing process. The computer 21, with the aid of the PLC 40, moves the printing table 13, under the battery 41, until one edge of the area to be printed is placed directly below the battery 41. Then the computer 21 and the PLC 40 operate the adequate spraying nozzles 19, while moving the printing table 13 beneath, until at least a part of the area to be printed is wetted. Preferably all and only the area to be printed is wetted. Preferably the spraying nozzles are operated intermittently to apply adequate amount of wetting composition to the wetted area. At this stage the garment is ready for printing and the printing table 13 is moved under the printing head 16 to commence printing as will be described below.
It is appreciated that the operation of selected spraying nozzles 19 while moving the garment below enables the wetting of only selected areas of the garment, particularly those areas to be printed, while other areas are left intact.
Optionally the computer 21, with the aid of the PLC 40, operate the curing assembly 20 while moving the printing table underneath, to cure, at least partially, the wetting composition, prior to printing.
It is appreciated that the wetting assembly 25, as well as the printing system 43, can be easily modified for printing objects other than garments.
Reference is now made to
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According to another embodiment of this invention, the garment mounting assembly is a simple, flattened plate, made of aluminum or wood on which a textile piece or a garment is positioned. Flattened plates are well known by those who are familiar with the garment printing industry.
Reference is now made to
According to one preferred embodiment of the invention, printing heads assembly 54 is a massive array of conventional piezoelectric drop-on-demand or continuous inkjet heads, which perform the high-speed printing. It is a particular feature of the present invention that at least a 500, and preferably several thousands (i.e., 2,000) nozzles are provided for simultaneous printing, resulting in a very quick and accurate process. Each printing head 55 consists of dozens of nozzles 56 that are controlled independently by main computer 21, optionally via PLC 40.
Reference is now made to
According to a preferred embodiment, the distances between nozzles and between printing heads are bigger than the printing resolution, hence several print passes are needed to complete the image. After each pass in the X-axis, here created by movement of the printing table assembly with media 53, the printing head 55 moves incrementally in the Y-axis to prepare for the next pass. It will be appreciated that the computer 21 is programmed to control the relative motion of the printing heads and the printing table assembly so as to obtain this accurate and complete coverage.
The printing process is performed while relative motion occurs between the printing heads array 55 and the printing table assembly. At least two axes of motion are needed for this multi-color printing: X-axis motion that is in the printing direction; and Y-axis motion that is perpendicular to the printing direction. As stated above, the distances between nozzles and between printing heads are bigger than the printing resolution, hence several print passes are needed to complete the image. This is accomplished by moving the printing table assembly back and forth along the X-axis while moving the heads array perpendicular to the line of printing. The X-axis is the printing line and the Y-axis is the line on which the printing heads array moves after each pass to fill the gaps between printed lines in the next pass. Multi-color printing is performed as the table surface passes below the drop-on-demand inkjet nozzles array.
According to an alternative embodiment of the invention, the Y-axis is the fast-moving axis, while the X-axis moves incrementally to permit filling in of the gaps between printed lines.
A printing command is sent by the printing heads driver (not shown) to each nozzle at the exact time and location for ink firing. The printing command is actually an electronic pulse, with exact width, voltage level, rise time and decay time. Printing heads drivers are commercial systems known in the industry, such as Inca drivers, of IncaDigital Printers, Cambridge, England. When printing is completed, the printing table is moved to a loading position. Then, the printed garment is unloaded and a new garment is loaded onto the printing table.
Reference is now made to
The printing system of the embodiments described above incorporates three processes, one after the other:
1. Loading and unloading garments.
2. Wetting at least a part of the area of the garment to be printed.
3. Printing an image on the mounted over at least a part of the wetted area.
In order to increase the throughput of the system, these processes can be performed in parallel, as seen in the above embodiments of the invention.
It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims that follow.
It is expected that during the life of this patent many relevant liquid applicator devices and ink applicator devices and systems will be developed and the scope of the terms herein, particularly of the terms “spraying nozzles” and “inkjet nozzles”, is intended to include all such new technologies a priori.
Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.
Number | Date | Country | Kind |
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162231 | May 2004 | IL | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL05/00166 | 2/10/2005 | WO | 00 | 5/14/2007 |