MACHINE FOR IN-DEPTH PRINTING ON A POLYESTER PILE LAYER CARPET COVERING

AND ASSOCIATED METHOD OF OPERATION

TECHNICAL FIELD The present invention concerns a machine for in-depth printing on a pile layer carpet covering and associated method of operation .

In particular, the present invention concerns a machine capable of printing, using the so-called "inkjet" technique, on a carpet such as a doormat, a rug, or a carpet, essentially comprising a flat backing layer in a flexible synthetic material and a pile layer covering the flat backing layer, which is positioned above the backing and is composed of a multiplicity of strands or semi-rigid bristles in polyester or polyamide, each of which is firmly fixed on the flat backing layer itself, to which the treatment that follows shall make explicit reference, but without any loss in generality.

It is opportune to specify that in the following, the technical term "inkjet" shall be intended as the printing technique that consists in depositing miniscule drops of a liquid dye on a medium to be printed on.

BACKGROUND ART

As is known, one of the most strongly felt needs to date of manufacturers of carpets with a polyester or polyamide pile layer is that of being able to print a multicolour image on the upper face of the pile layer using "inkjet" techniques and, at the same time, obtain complete colour penetration into the pile layer, i.e. uniform colouring of each strand for the entire thickness of the pile layer.

In fact, it is known that an objective technical difficulty currently exists in obtaining both high resolution and complete colour penetration inside the pile layer when using

"inkjet" printing techniques on the polyester or polyamide pile layer of a carpet.

At present, obtaining high definition in the printed image prejudices obtaining high colour penetration in the pile layer. For example, to achieve high definition, some inkjet techniques contemplate depositing extremely small drops of colour on the pile layer. However, due to their small size, these colour drops remain firmly constrained on the free tips of the strands due to the high surface tension exhibited by the drops themselves, which prevents their descent to the underlying backing. In this way, the strands that constitute the pile layer are only coloured at the top and remain neutral below, thus resulting in a poor aesthetic effect.

In order to achieve complete colour penetration in the layer and hence uniform colouring of the strands, it would thus be necessary to increase the size of the deposited drops, but this would obviously cause significant reduction in the definition achievable for the printed image.

DISCLOSURE OF THE INVENTION

The object of the present invention is to create a method for printing on the polyester or polyamide pile layer of a carpet using an "inkjet" technique that is able to simultaneously achieve high printing resolution and complete colour penetration inside the pile layer itself.

According to the present invention, a machine is thus embodied for printing on the polyester or polyamide pile layer of a carpet as expressed in claim 1 and preferably, but not necessarily, in any of the claims directly or indirectly dependent on claim 1.

According to the present invention, a method of operation is also provided for a machine for printing on the polyester or

polyamide pile layer of a carpet as expressed in claim 10 and preferably, but not necessarily, in any of the claims directly or indirectly dependent on claim 11.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention shall now be described with reference to the enclosed drawings, which show a non-limitative example of embodiment, where:

Figure 1 is a schematic side-elevation view of a machine embodied according to the principles of the present invention for printing on the pile layer of a carpet,

Figure 2 is a large-scale perspective view, with parts removed for clarity, of the printing device of the machine shown in Figure 1, while - Figures 3-6 are schematic views of four drop-discharge phases of the print heads present on the printing device shown in Figure 2.

BEST MODE FOR CARRYING OUT THE INVENTION With reference to Figure 1, reference numeral 1 indicates, in its entirety, a machine that uses the so-called "inkjet" technique for printing on a carpet 2, which basically comprises a flat backing layer 3 in a flexible synthetic material and a pile layer 4, positioned on top of and covering the flat backing layer 3, which is composed of a multiplicity of strands 5 or semi-rigid bristles in polyester or polyamide, each of which is firmly fixed on the flat backing layer 3 itself.

It is opportune to specify that in the following, the term carpet shall be an explicit reference to a rug, or carpet, or doormat, or car-mat, or any other type of carpet in polyester or polyamide and the like.

Basically, the machine 1 comprises: a surface 6 supporting the carpet 2, which is preferably, but not necessarily,

horizontal, is supported by a floor-standing frame 6a and extends between a loading station for the carpet 2 (not shown) and an unloading station for the printed carpet 2 (not shown) , and a printing device 9, which is supported by the frame 6a via a support unit (not shown) and arranged above the surface 6 in a position facing the carpet 2 to print an image on the pile layer 4 of the carpet 2 itself.

The machine 1 also comprises a transport member 10 able to feed the carpet 2 forwards over the surface 6 in a predefined direction D between the loading station and the unloading station and preferably, but not necessarily, a transport unit

11, which is able to move the printing device 9 at least along an axis of movement X orthogonal to the feed direction D of the carpet 2.

In the example shown in Figure 1, the transport member 10 comprises a feed belt 13 for the carpets 2 that extends over the surface 6 beneath the printing device 9 for the entire length of the surface 6 itself, and a series of powered rollers 13a that are connected to the frame 6a and able to make the upper part of the belt 13 advance in direction D so as to feed the carpets 2.

Instead, concerning the transport unit 11 in the example shown in Figure 2, this comprises a guide 14 that faces the surface 6 and extends in a transverse direction with respect to direction D, and a carriage 15, preferably motorized, which supports the printing device 9 and is mounted such that it can slide on the guide 14 to move, under command, across the entire width of the carpet 2.

With reference to Figure 1, the machine 1 also comprises a drying device 16, which is positioned downstream of the printing device 9 in the feed direction D and is able to dry and fix the colour (s) deposited on the pile layer 4 of the

carpet 2 itself. In the case in point, the drying device 16 can include a colour-setting oven, such as a hot-air oven, an infrared oven, a microwave oven or an ultrasonic oven.

The machine 1 also comprises a colour supply device 19, which basically comprises a series of main tanks 18 (Figure 1) containing respective dyes for polyester or polyamide fabrics, each of which is associated with a primary colour that can be used in combination with the other colours during printing to create a desired colour. In particular, main tanks 18 contain liquid dyes associated with specific primary colours. For example, each main tanks 18 may contain preferably, thought not necessary, cyan disperse dye, or magenta disperse dye, or yellow disperse dye or black disperse dye, or orange disperse dye, or green disperse dye or any other similar disperse dye colour .

The colour supply device 19 also comprises at least one secondary tank 22 able to hold a liquid wetting agent additive that, as shall be described in detail further on, is used during the printing operation on the carpet 2 to reduce the surface tension of the liquid dye deposited on the pile layer 4 in a controlled manner, in this way regulating its penetration inside the pile layer 4 itself.

In the case in point, the liquid wetting agent additive can consist of water and/or a liquid surface-active agent composition able to lower the surface tension of the liquid dye, facilitating the "wettability" of the pile layer 4.

For example, the liquid surface-active agent composition fed to each print head 12 could be the BIOMEGAPAL ® wetting agent and/or the IDROSOLVAN 1000 ® wetting agent or similar compositions .

In particular, to carry out printing on a twist carpet with a

weight between 300-600 grams, the liquid dye mixture can comprise, for example, 1-1.5% of liquid surface-active agent composition and 98.5-99% of dye.

Instead, to carry out printing on a pile carpet with a weight between 300-600 grams, the liquid dye mixture can comprise, for example, 0.1-0.5% of liquid surface-active agent composition and 99.5-99.9% of dye.

In particular, the main 18 and secondary 22 tanks have a set internal pressure and are connected to the printing device 9 through respective feed lines 23.

The machine 1 can also comprise a regulator device 17, which is connected to the main tanks 18 and the secondary tank 22 to control the flow of the liquid dye and/or the flow of the liquid wetting agent additive supplied in output from each tank 18 and 22 respectively and feeding the printing device 9.

In the case in point, the regulator device 17 could be able to selectively control the pressure inside each tank 18 or 22 and/or the pressure of the fluid in output from them. The regulator device 17 can, for example, comprise a compressor

17a connected to each tank 18 and/or 22, and/or solenoid control valves 17b inserted between the output of each tank 18 and the printing device 9.

The regulator device 17 can also comprise sensors (not shown) able to detect the pressure present inside each tank 18 or 22.

The printing device 9 comprises a plurality of main print heads 24, each of which is connected to a respective main tank 18 through a feed line 23 to receive the liquid dye and, when commanded, discharge a minuscule drop of liquid dye able to deposit itself on a preset point PX of the outer surface of the pile layer 4 of the carpet 2.

Unlike the printing devices present in carpet printing machines of the known type, the printing device 9 also comprises one or more secondary print heads 25, which are connected to secondary tanks 22 through respective tubular lines 23 and are able, when commanded, to discharge a minuscule drop of liquid wetting agent additive on a preset point PX of the upper surface of the pile layer 4 of the carpet 2.

It is opportune to specify that in the following, the term "minuscule" drop shall be intended as a drop with volume varying between approximately 1 nano-litre and 200 nano- litres .

With reference to the example shown in Figures 3-6, the main 24 and secondary 25 print heads each comprise a microvalve shutter, which in turn comprises a body 26, inside which a chamber or channel 27 is obtained in the centre that is able to hold a fluid and which extends along a longitudinal axis L and has an inlet (not shown) connected to a feed line 23 and an outlet connected to a fluid discharge nozzle 28.

The microvalve of the main 24 or secondary 25 print head also comprises a shutter member 29 mounted inside the channel 27 along the longitudinal axis L in a manner such that it can move between a closed position for the nozzle 28 (Figures 4 and 6) , in which the liquid dye or the liquid wetting agent additive remains inside the channel 27, and an open position for the nozzle 28 (Figures 3 and 5), in which the liquid dye or the liquid wetting agent additive freely flows from the nozzle 28 to the outside so as to form the minuscule drop to be deposited.

The microvalve of the print heads 24 or 25 also comprises an electric drive system able to move the shutter member 29 between the open position and the closed position. In the

example shown in Figures 3-6, the electric drive system comprises an inductor block 30 firmly connected to the body 26 and opportunely coupled to the shutter 29 and which, when traversed by an electrical current, is able to generate a magnetic field that causes the linear movement, and thus operation, of the shutter member 29 to the open position, against the opposing action of a spring 20 fitted on the stem of the shutter member 29 itself.

According to a different embodiment (not shown) , instead of inductor block 30, the electric drive system comprises a piezoelectric module, for example, a piezoelectric crystal, which is inserted between the body 26 and the shutter 29 and is able to mechanically deform itself under the action of an electric signal so as to cause, when commanded, the movement of the shutter 29 between the first and the second position.

With reference to Figure 1, the machine 1 also comprises an electronic control unit 31 able to coordinate the various operations implemented by the machine 1. In particular, the electronic control unit 31 is able to control: the transport member 10 to feed each carpet 2 along the surface 6 in direction D, the transport unit 11 to change the instantaneous position of the carriage 15 along the guide 14 during the feeding of the carpet 2, and each main print head 24 and each secondary print head 25 so as to control the discharge of the drops of liquid dye and/or liquid wetting agent additive onto a preset point of the upper face of the pile layer 4.

The electronic control unit 31 is also able to control the regulator device 17 so as to vary flow of the liquid dye and/or flow of the liquid wetting agent additive fed to the printing device 9.

The machine 1 also comprises a user interface device 32, a keyboard for example, through which it is possible to input a

series of characteristics to the electronic control unit 31 that are associated with the type of carpet 2 in polyester or polyamide for printing and/or the chemical/physical characteristics of the liquid dye present in each tank 18.

In particular, the characteristics associated with the type of carpet 2 include the thickness S of the pile layer 4, and/or the type TF of strand or bristle, which, for example, could be loop pile, cut pile, needled or tufted, and/or a parameter CP associated with the capillary rating of the strand or bristle when it is in contact with a liquid dye.

Instead, with regards to the characteristics associated with the type of liquid dye, these can include a parameter GV indicating the level of viscosity, and/or a parameter GT correlated to the contact surface tension of the dye with a polyester strand or bristle.

The electronic control unit 31 also comprises a memory device 33 containing at least one table 33a comprising a plurality of volumes Vci associated with the drops of liquid dye to be discharged and, for each dye drop volume Vci, a corresponding volume Vca for the drop of liquid wetting agent additive to be discharged.

More in detail, each volume Vci listed in the table 33a is unambiguously associated with a corresponding combination of the characteristics S, TF and CP associated with the type of carpet 2 and with a combination of chemical/physical characteristics GV and GT of the liquid dye present in each tank 18.

The volumes opening intervals Vci and Vca listed in the table

33a are each associated in an unambiguous manner with a respective opening interval δtl of the main print heads 24 and, respectively, with an opening interval δt2 of the

secondary print heads 25.

In addition, the volumes Vci and Vca listed in the table 33a are each preferably, but not necessarily, associated with an output pressure Pl of the main tanks 18 and an output pressure P2 of the secondary tank 22.

The electronic control unit 31 is able to process the characteristics S, TF AND CP associates with the type of carpet 2, and/or the characteristics GV and GT associated with each liquid dye used during printing, to determine the volumes Vci and Vca of the drops to discharge in function of these characteristics, by means of the first table 33a. After determining the volumes Vci and Vca, the electronic control unit 31 controls the opening of the print heads 24 and/or 25 in function of the opening intervals δtl and/or δt2 and preferably, but not necessarily, controls the regulator device 17 in function of the pressures Pl and P2 associated with the volumes Vci and/or Vca in question.

The method of operation of the machine 1 shall now be described. Initially, the characteristics S, TF and CP associated with the type of carpet 2 and/or the characteristics GV and GT associated with each liquid dye that will be used in the course of the printing operation are supplied to the electronic control unit 31 through the interface device 32.

At this point, the electronic control unit 31 processes the characteristics S, TF and CP associated with the type of carpet 2 and/or the characteristics GV and GT associated with each liquid dye to determine, via the table 33a, the volume

Vci of the drops of liquid dye that must be discharged by each main print head 24 and the volume Vca of the drops of liquid wetting agent additive that must be discharged by the secondary print head 25 during printing. After determining the

volumes Vci and Vca, the electronic control unit 31 is able to calculate, by means of the table 33a: the opening interval δtl to be controlled on each main print head 24, the opening interval δt2 to be controlled on each secondary print head 25, the output pressure Pl to be controlled on each main tank 18 and the output pressure P2 to be controlled on the secondary tank 22.

Upon completion of setting up for the above-indicated control parameters, the electronic control unit 31 controls the feeding of the carpet 2 along the surface 6 so as to position it in correspondence to the printing device 9. When the carpet 2 reaches a preset position, the electronic control unit 31 operates the printing device 9, opportunely synchronizing and coordinating the feeding of the carpet 2 with respect to the printing device 9 and the transversal movements of the carriage 15, and synchronizing these movements with the open and close commands of each main 24 or secondary 25 print head, in function of the image to be printed.

In this phase, the electronic control unit 31 controls the opening/closing of each secondary print head 25 so as to discharge minuscule drops of wetting agent (indicate by I in Figure 3 and 4), having volume Vca, in one or more preset points Px (only one of which is shown in Figures 3-6) . In this phase, the electronic control unit 31 also operates the opening/closing of each main print head 24 (Figures 5 and 6) according to the opening interval δt2 so as to discharge minuscule drops of liquid dye (indicate by C in Figures 5 and 6) , each having set volume Vci, in at least one of the same preset points Px.

More in detail, during printing, the electronic control unit

31 controls each main head 24 and each secondary print head 25 such that for each point Px on the upper surface of the pile layer 4, at least one drop of liquid wetting agent additive of

volume Vca (Figure 4) and one or more drops of liquid dye of volume Vci are deposited (Figure 6) .

In the case in point, according to a first embodiment shown in Figures 3-6, the electronic control unit 31 controls each main print head 24 and each print head 25 such that for each point Px on the upper surface of the pile layer 4, at least one drop of liquid wetting agent additive and, successively, one or more drops of liquid dye are deposited.

According to a different embodiment, the electronic control unit 31 controls each main print head 24 and each print head 25 such that for each point Px on the upper surface of the pile layer 4 associated with the image to be printed, one or more drops of liquid dye are deposited and, successively, at least one drop of liquid wetting agent additive is deposited on top of the deposited drops of liquid dye.

Regarding that described above, it is opportune to specify that the drop of liquid wetting agent additive deposits itself on one or more strands 5 of the pile layer 4 wetting their outer surface and so causing a precise reduction in the contact surface tension of the drops of liquid dye in contact with the strands.

When printing is completed, the electronic control unit 31 controls feeding of the carpet 2 to the drying device 16, which dries and fixes the printed image on the carpet 2 itself. After drying is completed, the electronic control unit 31 controls feeding of the printed carpet 2 to the unloading station .

According to a possible embodiment, the electronic control unit 31 is able to modulate the depth of colouring of the pile layer 4 at each point Px in a specific manner, according to colour. In particular, the electronic control unit 31 could be

able to control each secondary head 25 so as to modulate the volume Vca of the drops of wetting agent in function of the depth of colouring that it is wished to achieve within the pile layer 4 for a specific colour. For example, the electronic control unit 31 could be able to reduce the volume Vca of the drops of wetting agent deposited in some points associated with the colour red so as to achieve less penetration of red liquid dye into the layer, and, at the same time, increase the volume Vca of the drops of wetting agent deposited in some points associated with the colour yellow so as to achieve more penetration and thus greater depth in the pile layer 4 with yellow liquid dye.

In this way, the machine 1 can advantageously be capable of achieving precise and differentiated print depth regulation of the image within the pile layer 4 based on the different colours used in the image.

In addition, the electronic control unit 31 can advantageously be capable of simultaneously controlling each main 24 and secondary 25 head so as to modulate the volumes Vci and Vca of the drops to be deposited at the same point Px, in function of the shade of colouring that it is wished to obtain at that point Px.

The advantages deriving from utilization of the above- described machine 1 are evident. Firstly, the precise depositing of drops of wetting agent on the points to be coloured allows a reduction in the surface tension to which the drops of liquid dye are subjected, thereby determining uniform colouring of the strands for their entire length.

Furthermore, the operation of modulating the volume Vca of each drop of liquid wetting agent additive, in combination with the modulation of the volume Vci of the drops of liquid dye, allows the right quantity of colour needed to completely

colour the entire strand to be discharged with precision, thus eliminating conditions of colour wastage and additional operations needed to clean excess dyes from the carpet.

Lastly, modulation of the volume Vca of each drop of liquid wetting agent additive allows different levels of colour penetration to be obtained within the pile layer for a printed image, thereby achieving three-dimensional aesthetical effects .

In conclusion, it is clear that modifications and variants can be made to the above-described machine 1 and the associated method of operation without however leaving the scope of the present invention, as defined according to the enclosed claims.

In particular, according to a variant (not shown) , the machine 1 is devoid of the transport member 11 and the printing device 9 comprises a plurality of fixed main print heads 24, which are arranged coplanar to each other in side-by-side positions according to a matrix layout, and a plurality of fixed secondary print heads 25, which are arranged coplanar to each other in side-by-side positions preferably, but not necessarily, aligned. In use, printing on the carpet 2 is carried out by jog advancement of the belt 13, and therefore of the carpet 2 with respect to the print head 9, and concomitantly operating the opening of each main 24 or secondary 25 print head so as to discharge one or more drops of wetting agent and/or dye onto a preset point of the underlying carpet 2.