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

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

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, a carpet, or a car-mat, which comprises 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 polyester strands or semi-rigid bristles, 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 discharging miniscule drops of a liquid dye on preset points of a printing surface.

BACKGROUND ART As is known, one of the most strongly felt needs to date of manufacturers of carpets with a polyester pile layer is that of being able to print a multicolour image on the flat upper face of this pile layer with a high dot pitch using "inkjet" techniques and, at the same time, obtain complete dye 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 penetration of the liquid dye within the pile layer when using "inkjet" printing techniques on the polyester 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 dye on the pile layer. However, due to their small size, these drops of dye remain firmly constrained on the free tips of the strands because of the high surface tension that acts on the drops when they make contact with the strands prevents their descent to the underlying backing. In consequence, the strands that constitute the pile layer are only coloured on their tops and remain neutral, or rather uncoloured, on the part 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 discharged 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 the polyester pile layer of a carpet using an "inkjet" technique that is able to 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 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 for printing on the polyester pile layer of a carpet is also provided, as expressed in claim 5 and preferably, but not necessarily, in

any of the claims directly or indirectly dependent on claim 5.

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, while - Figure 2 is a schematic side-elevation view of a variant of the machine for printing the pile layer of a carpet shown in Figure 1.

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 in-depth printing on a polyester carpet 2, which basically comprises a flat backing layer 3 in a flexible synthetic material and a polyester pile layer 4 covering the flat backing layer 3, which is arranged on top of the backing 3 and is composed of a multiplicity of strands 5 or semi-rigid bristles in polyester, 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 similar type of polyester carpet .

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 7 and is able to move each carpet 2 in a feed direction D between a loading station for the carpet 2 (not shown) and an unloading station for the printed carpet 2 (not shown), and an "inkjet" printing device 10, which is supported by the frame 7 via a

support unit (not shown) and arranged above the surface 6 between the loading station and the unloading station.

The machine 1 also comprises a setting oven 16 positioned downstream of the printing device 10 in the feed direction D to dry and fix the dye(s) deposited on the pile layer 4 of the carpet 2 itself. In the case in point, the setting oven 16 can comprise a hot-air oven, an infrared oven or a microwave oven.

With regard to the "inkjet" printing device 10, this is of a known type and shall not be described further, except for specifying that it comprises a plurality of mobile-shutter print heads 12, each able to discharge, upon command, minuscule drops of a liquid dye mixture (described further on) onto the carpet 2 positioned below the printing device 10. It is opportune to specify that in the following, the term "minuscule" drop shall be intended as a drop whose volume varies between approximately 1 nano-litre and 200 nano-litres.

More in detail, the printing device 10 can be fixed or mobile with respect to the surface 6, while the print heads 12 each comprise a mobile-shutter microvalve, which in turn comprises a body 12a, inside which a chamber or channel 12b is obtained in the centre that is able to hold the dye mixture, a shutter 12c mounted inside the chamber in a mobile manner such that it can move between a closed position in which it prevents discharge of the dye mixture in the chamber and an open position in which the chamber is opened to discharge a drop of dye mixture, and an electromechanical or electromagnetic drive system (not shown) able to move the shutter 12c between the closed position and the open position, upon command.

With reference to Figure 1, the machine 1 also comprises a supply unit 13 for the dye mixture, which is connected to the printing device 10 by feed lines 14 to supply the liquid dye mixture in a selective manner to each print head 12, this

mixture containing a certain quantity of dye and a certain quantity of liquid surface-active agent composition, which is able to reduce the surface tension of the dye when it comes into contact with the strands 5 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, 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 comprises, 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 comprises, for example, 0.1-0.5% of liquid surface-active agent composition and 99.5-99.9% of dye.

In the example shown, the supply unit 13 comprises a plurality of containers or tanks 15, which contain the liquid dye mixtures associated with the corresponding colours, for example, the primary colours, and are connected to the print heads 12 through the feed lines 14 in order to feed them with the liquid dye mixtures at a given pressure.

In detail, the quantity of disperse dye and the quantity of liquid surface-active agent composition suitable for being contained in each tank 15 can be calculated on the basis of a series of print formulas, each of which is associated with a certain type of polyester carpet 2 for printing, and/or a certain type of disperse dye. In the case in point, the quantity of disperse dye and the quantity of liquid surface- active agent composition contemplated by each print formula can be determined in a testing phase, prior to printing, according to 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 disperse dye, and/or a parameter GV indicating the level of viscosity of the disperse dye contained in the tank, and/or a parameter GT correlated to the contact surface tension of the disperse dye with a polyester strand or bristle.

The machine 1 also comprises an electronic control unit 18 able to govern the feed surface 6 so as to move each carpet to a given position in direction D, the supply unit 13 so as to control the supply of dye mixture to the print heads 12, and the printing device 10 so as to control the opening and closing of each print head 12 in function of the image to be printed on the carpet 2.

Basically, the method for printing the carpet 2 provides for the following phases: prepare in each tank 15 the quantity of disperse dye and the quantity of liquid surface-active agent composition contemplated in the print formula associated with the type of carpet to be printed and/or the type of disperse dye used in the same tank 15, in order to obtain a dye mixture in each tank 15 - selectively feed the dye mixture contained in each tank 15 to the print heads 12 - pilot the print heads 12 so as to discharge the drops of dye mixture onto the carpet 2 and, at the same time, feed the carpet 2 along the support surface so that each drop is deposited on the carpet 2 in a preset position, in function of the image to be printed - activate the setting oven 16 in order to dry/fix the dye mixture on the strands 5 of the pile layer 4.

The above-described machine and method have the advantage of ensuring complete penetration of the dye mixture within the pile layer, uniformly colouring each polyester strand in the carpet. In fact, use of the dye mixture comprising the

disperse dye and the liquid surface-active agent composition allows the surface tension encountered by each drop in contact with the strands to be reduced, in this way letting the same drop of dye to flow over the outer surface of the strands, completely colouring them for their entire length.

The embodiment shown in Figure 2 regards a machine 20 for printing polyester carpets 2 that is similar to machine 1, and the component parts of which shall be indicated, as far as possible, by the same reference numerals as the corresponding parts of machine 1.

The machine 20 for printing polyester carpets comprises a device 21 capable of supplying a certain quantity of liquid surface-active agent composition to each tank 15, a memory unit 22 containing a plurality of print formulas and a suitable interface device 23 to allow a user to select a given print formula.

In detail, each print formula is unambiguously associated with a type of polyester carpet 2 and/or the type of disperse dye that can be contained in the tank 15, in which the type of carpet is indicated by the thickness S and/or the type TF of strand or bristle, while the type of dye is indicated by the above-described parameter CP and/or parameter GV and/or parameter GT.

In the example shown, the device 21 comprises a holding tank 24 for the liquid surface-active agent composition, which is connected to each tank 15 through a feed line 26 to supply, upon command, the liquid surface-active agent composition to each tank 15, and a device 27 able to regulate the quantity of liquid surface-active agent composition transferred from tank 23 to tank 15.

In particular, tank 24 could have a certain internal pressure,

while device 27 could comprise a series of solenoid metering valves 25 each of which is positioned on a feed line 26 and is able, upon command, to meter the quantity of liquid surface- active agent composition that flows from tank 24 to tank 15.

The electronic control unit 18 is able to control each solenoid metering valve 25 so as to opportunely regulate the quantity of liquid surface-active agent composition fed to each tank 15.

The printing method also provides for the following phases: store a plurality of print formulas in the memory unit 22, each of which is unambiguously associated with a type of polyester carpet 2 and includes a plurality of dye mixtures, each containing a certain quantity of disperse dye and a certain quantity of liquid surface-active agent composition - select a given print formula from the various print formulas stored in the memory unit 22 via the interface device 23 - operate device 21 to add the quantity of liquid surface-active agent composition provided for in the dye mixture specified in the print formula to each tank 15 - feed the dye mixture contained in each tank 15 to the print heads 12 - pilot the print heads 12 so as to discharge the drops of dye mixture onto the carpet 2 and, at the same time, feed the carpet 2 along the surface 6 so that each drop is deposited on the carpet 2 in a preset position, in function of the image to be printed - activate the setting oven 16 in order to dry/fix the dye mixture on the strands 5 of the pile layer 4.

The machine 20 is extremely advantageous as, in addition to the advantages of machine 1 described above, it allows the automatic adjustment of the quantity of liquid surface-active agent composition to add in each tank 15, thereby increasing the metering precision of the liquid surface-active agent composition and considerable simplifying the operations required of the operator of the machine 20 itself.

Lastly, it is clear that modifications and variants can be made to the above-described machines 1 and 20 and the method without however leaving the scope of the present invention, as defined according to the enclosed claims.