BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a device for patterning workpieces according to an embodiment of the invention;
FIG. 2 is a schematic partial plan view of the device shown in FIG. 1;
FIG. 3 is a schematic, partially cut-away front view of the device shown in FIG. 1;
FIG. 4 shows further details of the printing means of the device shown in FIG. 1;
FIG. 5 shows further details of the printing means of the device shown in FIG. 1; and
FIG. 6 illustrates the operation of the device shown in FIG. 1.
DETAILED DESCRIPTION
Preferred embodiments of the present invention will be described hereinafter in detail with reference to the accompanying drawings.
FIG. 1 is a schematic perspective view of a device 1 for patterning workpieces as a preferred embodiment of the present invention. The device is used for patterning workpieces 2 which, in the preferred embodiment, consist at least partially of wood, wood materials, plastics materials or the like, such as are frequently used in the field of furniture and kitchen design.
The device 1 comprises an ink-jet printing means 10 which, in the present embodiment, operates in accordance with the drop-on-demand principle. As may be seen most clearly in FIG. 4, the ink-jet printing means 10 comprises a plurality of nozzles 12 from which drops of ink can be expelled and which, in the present embodiment, are disposed in a plurality of rows, each row being provided for expelling a predetermined colour, for example the colours cyan, magenta, yellow and black.
Also provided on the printing means 10 are drying units 14, for example UV driers, which are used promptly to dry the ink applied by the printing means in order to prevent possible distortion or smudging of the printed image.
The printing means 10 is in the present embodiment provided on or inserted into a spindle unit 6, although this is not shown in detail in FIG. 1. The spindle unit is preferably a spindle unit which is also suitable for the insertable and exchangeable receiving of machining tools or machining installations. The spindle unit 6 is provided on a portal 4 so as to be movable in the y direction, wherein the portal may itself, in turn, be configured so as to be movable in the x direction. In this regard, the present embodiment provides two portals 4 which can each carry one or a plurality of spindle units 6 which may optionally be disposed on opposing sides of the respective portal 4. It should be noted in this regard that the portals 4 may, if appropriate, also be configured as jibs. The spindle units 6 can be automatically or manually fitted via tool magazines (not shown in detail in this case) with machining tools and/or machining installations and one or more printing means 10.
In the present embodiment, there extends below the portals 4 a workpiece table 20 for carrying the respective workpieces 2 to be patterned, which table is movable in the x direction shown in FIG. 1. The workpiece table 20 can have a broad range of configurations and, for example, also be formed by a circulating conveyor belt or the like. On account of its movability, the workpiece table 20 forms at the same time a workpiece carrier means and a portion of the conveyor device according to the present invention.
FIG. 2 is a detailed plan view of the disposal of a plate-like workpiece 2 on the workpiece table 20. In the present embodiment, the workpiece table 20 has extensible stop pins 22 against which the workpiece 2 can be placed for rough positioning. Also disposed on the workpiece table 20 is a plurality of distance sensors 52 which are part of a rough detection means 50. The distance sensors shown in FIG. 2 are configured to detect the distance between the sensors and a lateral surface (narrow surface) of each workpiece 2. In the present embodiment, the sensors 52 are in this regard rotatable about an axis extending orthogonally to the surface of the workpiece table 20 and are optionally movable parallel to the surface. The rough detection means 50 is thus used for roughly detecting the geometry and positioning of each workpiece 2.
Further details of the workpiece table 20 are shown in FIG. 3 which is a partially cut-away front view of the device shown in FIG. 1. It may be seen from FIG. 3 that the respective workpiece 2 may be fixed on the workpiece table 20, for example via vacuum suction means 24. It is also possible to integrate appropriate suction means or suction openings into the workpiece table or a workpiece belt.
The device 1 according to the invention further comprises a detection means 40 for detecting the relative position of the ink-jet printing means 10 and the respective surface to be patterned of a workpiece 2. In the present embodiment, the detection means 40 has a plurality of types of sensors 42, 46 which can be seen most clearly in FIGS. 3, 4 and 5. In the present embodiment, the detection means 40 comprises first of all three distance sensors 42 which are disposed on the printing means 10 adjacently to the nozzles 12 and measure in a direction substantially parallel to the direction in which ink is expelled from the nozzles 12 (FIG. 4). On the one hand, these distance sensors can be used to determine the absolute distance between the printing means 10 and the workpiece 2; however, in addition, the precise contour of each workpiece 2 can also be inferred from the distance data obtained.
As may be seen most clearly in FIGS. 3 and 5, further distance sensors 42 are disposed on the printing means 10, in each case via an element 44 which, in the present embodiment, is able to pivot. The pivotable element 44 allows each sensor to be brought into an extended position which can be seen most clearly in FIG. 5. In this position, the sensors 42, shown in FIG. 5, measure in a direction substantially orthogonal to the direction in which ink is expelled from the nozzles 12. This allows the thickness or height of each region to be imprinted to be detected and an overspray to be avoided.
In addition, in the present embodiment, there is disposed on the printing means 10, adjacently to the ink expelling nozzles 12, an image detection sensor 46 which also measures in a direction substantially parallel to the direction in which ink is expelled from the nozzles 12. The image detection sensor 46 may, for example, be a CCD camera or the like which can produce a complete image of a region of the respective workpiece 2 that is to be imprinted or has already been imprinted.
Although not shown in the figures, all of the sensors, on the one hand, and the printing means and preferably also the remaining operating components of the device 1, on the other hand, are connected to a control means which evaluates the respective data collected by the sensors and on this basis controls the operation of the device, in particular of the printing means. The device may in this regard be operated as follows.
First of all, a workpiece 2 is roughly positioned on the workpiece table 20 via the stop pins 22 and fixed via the vacuum suction means 24. Subsequently, the positioning and/or contour of the workpiece 2 on the workpiece table 20 are detected by the sensors 52 and this data is forwarded to the control means.
The workpiece table 20 is then moved in the x direction, so the workpiece 2 can be machined or refined by tools, installations or printing units inserted into the spindle units 6. In this regard, the printing means is, for example, operated as follows.
Based on the data from the sensors 52, the printing means 10 is moved with the corresponding spindle 6 along the portal 4 to the workpiece 2 to be imprinted. In this regard, the sensors 42, 46 continuously perform a measuring operation, thus allowing the presence and, if appropriate, the distance of each workpiece and, in addition (by way of the image detection sensor 46), further information about the workpiece 2 to be obtained. Based on this data, the control means issues print signals to the respective nozzles 12 (or the associated piezoelectric actuators or thermocouples), so the workpiece 2 is imprinted. Individual nozzles or groups of nozzles can in this regard be switched on or off as a function of the detection data of the sensors 42, 46 in order to compensate for dimensional, positional or other tolerances or deviations of the workpiece 2. Alternatively or additionally, it is also possible, within the scope of the invention, for individual nozzles or a plurality of nozzles of the printing means 10 to be produced via piezo adjustment means or the like, in order to adapt the position or direction of expulsion thereof to the workpiece 2.
When imprinting a large lateral surface of a workpiece 2, there operate, in addition to the image detection sensor 46, primarily the sensors 42 which are disposed next to the nozzles 12 and can be seen most clearly in FIG. 4. In order to imprint a narrow surface of the workpiece 2, use is alternatively or additionally made of the sensors 42 which are extensible via pivotable elements 44 in order to detect the height of the narrow surface and thus to prevent an overspray.
Once a surface portion has been imprinted, it can optionally be dried by the drying units 14, if necessary simultaneously to the printing process.
FIG. 6 illustrates schematically the paths of movement of the printing means 10 and/or the workpiece 2. The left-hand drawing in FIG. 6 shows an operation in what is known as transverse printing in which the printing means 10 moves back and forth in the y direction, together with the spindle unit 6, along the portal 4, and the workpiece table 20 further clocks the workpiece 2 in the x direction.
Alternatively, it is also possible to use the printing model which is shown on the right-hand side in FIG. 6 and is referred to as longitudinal printing. In this model, the printing means 10 is itself substantially stationary during the printing process, and the workpiece 2 is moved back and forth in the x direction with the workpiece table 20. The printing means 10 has therefore merely to be further clocked in the y direction once the printing of a web is completed. In addition, within the scope of the present invention, combinations of both operations are also possible, and webs disposed, for example, obliquely or the like can be printed.
Patent Application
20080048388
