Inkjet printhead, in particular for sewing/embroidering machines, a method for making said inkjet printhead, and a method for coloring a thread

An inkjet printhead, in particular for sewing/embroidering machines, includes a support structure; a plurality of firing cells included in the support structure, each firing cell being adapted to eject ink through a respective nozzle for coloring a thread to be used in a sewing/embroidering machine; a guide element, provided on the support structure, for guiding the thread in a position facing said nozzles. Also disclosed are a sewing/embroidering machine including the printhead and a method for making the printhead.

The present invention relates to an inkjet printhead for sewing/embroidering machines.

The present invention also relates to a sewing/embroidering machine provided with an inkjet printhead for coloring a thread before the same thread is used for sewing and/or embroidering.

The present invention also relates to a method for making an inkjet printhead for use in a sewing/embroidering machine.

As it is known, the state of the art comprises sewing/embroidering machines provided with an inkjet printhead for coloring a thread before the same thread is used for sewing and/or embroidering.

In more detail, such machines include a bobbin around which a thread is wound; a printing station to which the thread is provided and wherein, the thread is colored through an inkjet printhead; a drying station, wherein the colored thread is heated and dried, so that such thread is suitable for being used for sewing or embroidering a predetermined product, such as for example a textile product; an operative station, wherein said product is properly positioned and sewed and/or embroidered with said thread.

Document U.S. Pat. No. 6,189,989 discloses an ink jet printing apparatus having a station for dyeing a thread for embroidering by discharging ink onto the thread from an ink jet head. A printing controller controls the amount of ink discharged per unit of time onto the thread according to the speed of the relative movement of the thread and the ink jet head. Also, it is taken into account the length of non-usable thread per unit time between an ink jet printing unit and the tip of an embroidery needle in an embroidery machine.

A drawback shown in the machines according to the state of the art regards the imprecise alignment of the thread with respect to the ejecting nozzles.

In fact, after being unwound from the above mentioned bobbin, the thread is generally guided by a first pulley, mounted between the bobbin and the printing station.

Then, after being colored and dried, the thread is guided by a second pulley, which feeds the sewing/embroidering members.

In other words, the relative position between the thread and the nozzles is defined by the cited first and second pulleys.

The applicant noted that, in case the distance between the first and second pulley is about 30 cm, even a minimum error or tolerance in the position of the pulleys with respect to the printhead (and in particular with respect to the nozzles) prevents the thread from being precisely placed in front of the nozzles.

Moreover, unavoidable tolerances in the assembling of the printhead, in the position of the printhead on the machine and of the active members which bring the printhead in the printing position, contribute to the misalignment of the thread with respect to the nozzles.

Such imprecise mutual positioning causes a non uniform and inhomogeneous coloring of the thread, and a decrease of the quality of the final product obtained after sewing or embroidering.

By way of example, the tolerance in the positioning of the first pulley with respect to the frame of the machine is about ±1 mm; the tolerance in the position of the nozzles on the printhead is about ±0.05 mm; the tolerance in the positioning of the printhead with respect to the carriage support is about ±0.1 mm; the tolerance in the positioning of the carriage support with respect to the frame of the machine is about ±0.25 mm; the tolerance in the positioning of the second pulley with respect to the frame of the machine is about ±1 mm.

Therefore, in the worst case, the misalignment of the thread with respect to the nozzles is of about ±1.4 mm.

The applicant found a possible solution: an additional guide element is mounted on the carriage which supports the printhead and with respect to which the printhead is regularly moved during its functioning.

In this solution, the maximum misalignment between the thread and the nozzles is reduced, but it is still unacceptable.

In fact, taking into account that: ±0.25 mm is the tolerance between the frame of the machine and the support carriage; ±0.1 mm is the tolerance between the support carriage and the printhead mounted thereon; ±0.05 mm is the tolerance between the printhead and the nozzles; ±0.05 mm is the tolerance between the printhead and the guide element mounted on the support carriage; ±1 mm is the tolerance between the second pulley and the machine frame, the following result is obtained, in case the distance between the first and second pulley is 25 cm, the distance between the first pulley and the first nozzle is 10 cm, and the distance between the first nozzle and the last nozzle is 11 cm:

(0.25+0.1+0.05)+1250·(10+11)=±0.12⁢⁢mm
and the maximum misalignment is substantially equal to:
0.05+0.05+0.12=±0.22 mm

Another possible solution would be to increase the number of inkjet units and/or the number of nozzles, so that a larger ejecting area is obtained and the likelihood of provision of ink to the thread is correspondingly increased.

However, such solutions show unacceptable drawbacks, such as, for example, the increase of the number of components to be used (two printheads instead of a single one); the large amount of ink that is wasted, since only a small portion of the ejected ink is actually received by the thread; the increase of energetic consumption, since a higher number of firing cells have to be activated for increasing the amount of ink ejected.

The Applicant has noted that, by using an additional guide element, the position of the thread with respect to the ejecting nozzles can be defined in a very precise way, thereby solving the aforementioned problem and overcoming the cited drawbacks.

More particularly, the guide element is provided on the printhead, so as to be at least partly substantially integral with the same printhead. Likewise, irrespective of the position of the first and second pulleys, the thread is properly guided in a position facing the ejecting nozzles.

According to a first aspect, the invention regards an inkjet printhead, in particular for sewing/embroidering machines, comprising:a support structure;a plurality of firing cells included in said support structure, each firing cell being adapted to eject ink through a respective nozzle for coloring a thread to be used in a sewing/embroidering machine;a guide element, provided on said support structure, for guiding said thread in a position facing said nozzles.

Preferably, the guide element defines the position of the thread in a first direction, substantially parallel to a plate-like element in which the nozzles are made and substantially perpendicular to a thread alignment direction, and in a second direction, substantially perpendicular to said plate-like element.

Likewise, both alignment with the nozzles and distance therefrom are defined by means of said guide element.

According to another aspect, the invention regards a machine for sewing and/or embroidering comprising:a feeding member for providing at least a thread;a printing station adapted to receive said thread and to color the same;a drying station, wherein the colored thread provided by the printing station is dried;an operative station, wherein said thread is used for sewing and/or embroidering a predetermined product
wherein said printing station comprises the aforementioned inkjet printhead.

According to another aspect, the invention regards a method for making an inkjet printhead for use in a sewing/embroidering machine, said method comprising:providing a support structure including a plurality of firing cells, each firing cell being adapted to eject ink through a respective nozzle for coloring a thread to be used in a sewing/embroidering machine;providing a guide element on said support structure, for guiding said thread in a position facing said nozzles.

Preferably, the method further comprises the following steps:mounting said guide element on said support structure in an initial position, said guide element being movable on said support structure in two or more positions, each corresponding to a respective position of said thread when said printhead is in use;defining a target position of said guide element with respect to said nozzles;detecting a current position of said guide element;detecting a position of said nozzles;comparing the position of said guide element with the position of said nozzles;moving said guide element depending on said comparison in order to arrange said guide element in said target position.

When the guide element is in its target position, the same guide element is fixed to the support structure. With reference to the above cited example, in case the additional guide element is co-moulded with the support structure of the printhead, the maximum misalignment between the thread and the nozzles will be determined by the following contributions:

±0.05 mm which is the tolerance between the printhead and the nozzles;

±0.02 mm which is the tolerance between the printhead and the guide element;

±1 mm which is the tolerance between the second pulley and the machine frame.

Therefore
(1/250)·(7+11)=±0.07 mm
and the maximum misalignment is substantially equal to
0.05+0.01+0.07=±0.13 mm

In case the additional guide element is regulated before being fixed to the structure of the printhead, the maximum misalignment is limited to
(1/250)·(7+11)=±0.07 mm
thereby obtaining a significant improvement in the alignment between the thread and the nozzles.

According to a still further aspect, the invention regards a method of coloring a thread to be used in a sewing/embroidering machine, comprising:providing a thread to a printing station included in a sewing/embroidering machine, said printing station being provided with an inkjet printhead comprising a support structure including a plurality of nozzles;guiding said thread in a position facing said nozzles through a guide element provided on said support structure;ejecting ink trough said nozzles for coloring said thread.

With reference to the drawings, the inkjet printhead according to the present invention is generally denoted at1.

Inkjet printhead1is included in a sewing/embroidering machine2.

As schematically shown inFIG. 1, the machine2includes a feeding member3, which is adapted to provide a thread4to the other members included in the machine2.

For example, the feeding member3can be realized as a bobbin, around which a thread4is wound.

The thread is, for example, a polyester thread, although other textile materials are also possible for the thread.

The feeding member3feeds the thread4to a printing station5, where the printhead1is located. The printhead1ejects ink onto the thread4, so as to color the same.

The machine2further comprises a drying station6, wherein the colored thread is dried, preferably by heating, so that the same thread is suitable for being used for sewing or embroidering a predetermined product, such as for example a textile product.

The machine2further comprises an operative station7, wherein said product is properly positioned and sewed and/or embroidered with said thread4.

Thus, the thread4has an advancing direction D that is preferably defined by the succession of feeding member3, printing station5, drying station6and operative station7.

In more detail, the printhead1(FIGS. 2-5) comprises a support structure10, which can be in the form of a substantially parallelepiped box structure. The support structure10includes a plurality of firing cells11; each firing cell11is adapted to eject ink through a respective nozzle12for coloring the thread4.

Preferably, the nozzles12are made in a plate-like element13, integral with the support structure10; in particular, the nozzles12are through-holes made in said plate-like element13.

Each firing cell11is hydraulically connected to an ink reservoir, for receiving ink to be ejected.

Each firing cell11is also provided with a respective resistor which, when properly heated through a suitable current, causes formation of a bubble and ejection of an ink droplet.

Preferably the printhead1further comprises a control circuit (not shown) for selectively activating the firing cells11; in particular, the control circuit generates firing current commands for heating the resistors of the firing cells11.

Advantageously, the printhead1further comprises a guide element20, provided on said support structure10, for guiding the thread4in a position facing the aforementioned nozzles12.

The guide element20defines the position of the thread4with respect to the nozzles12.

In particular, the guide element20defines the position of the thread4along a first direction X, which is substantially parallel to the plate-like element13and substantially perpendicular to the thread alignment direction, and along a second direction Y which is transverse, and preferably substantially perpendicular, with respect to said plate-like element13.

As schematically shown inFIGS. 2-5, the guide element20comprises a first portion21for defining the position of the thread4in the first direction X, and a second portion22for defining the position of the thread4in the second direction Y.

Preferably the first portion21has a main longitudinal direction L that is transverse, and in particular perpendicular, with respect to the plate-like element13.

Preferably, the second portion22has a main longitudinal direction K that is substantially parallel to the plate-like element13and preferably substantially perpendicular to the thread alignment direction.

For example, the second portion22of the guide element20defines a distance of the thread4from the nozzles12which can be comprised between 0.5 mm and 1.5 mm.

Preferably, the guide element20is provided on the support structure10so as to precede the nozzles12according to the advancing direction D of the thread4.

In other words, the thread4fed by the feeding member3is guided by the guide element20before the same thread4faces the nozzles12.

Accordingly, the guide element4can properly define the position of the thread4with respect to the nozzles12.

Preferably, the nozzles12are arranged on the plate-like element13so that such arrangement has a symmetry axis S.

Preferably, the symmetry axis S defines the path along which the thread4should be aligned.

Preferably, the first portion21of the guide element20is not symmetrically arranged with respect to the symmetry axis S of the nozzles12.

Likewise, a part of the external surface of the first portion21is substantially aligned (or substantially tangent) to the symmetry axis S so that the thread4, being guided by such part of the external surface of the first portion21, can be properly arranged along said symmetry axis S.

Such position of the thread4with respect to the nozzles12allows a precise and efficient coloring of the same thread4.

Preferably the guide element20is at least partly integral with the support structure10; in particular, the guide element20can be completely integral with the support structure10.

Preferably the guide element20is integral with the plate-like element13.

FIGS. 2-3schematically shows a first embodiment of the guide element20.

In the first embodiment, the guide element20is completely integral with the support structure10; preferably the support structure10and the guide element20are co-moulded.

In the first embodiment, the guide element20is preferably “L” shaped.

The vertical portion of the “L” shape constitutes the first portion21of the guide element20, i.e. the portion that defines the position of the thread4in a direction X parallel to the plate-like element13. Preferably the first portion21is perpendicular to the plate-like element13.

The horizontal portion of the “L” shape constitutes the second portion22, that defines the position of the thread according to a direction Y perpendicular to the plate-like element13.

Preferably the second portion22is parallel to the plate-like element13.

The second portion22can constitute a shim to define a proper distance between the nozzles12and the thread4.

Preferably, in the first embodiment, the support structure10and the guide element20are made of the same material, such as for example Polyphenylene Oxide (PPO), Polysulfone (PSU), Polyethylene terephthalate (PET), Polyethylene terephthalate blended with Polybutylene terephthalate (PET+PBT), etc.

FIG. 4-5schematically shows a second embodiment of the guide element20.

In the second embodiment, the first portion21of the guide element20comprises a plate-like base23, and a pin24eccentrically mounted on the base23and integral with the same.

In the second embodiment, the first portion21is preferably made in a material different than the support structure10.

The first portion21of the guide element20can be made, for example, of Polyphenylene Oxide (PPO) blended with Glass Fibers (PPO+GF), Polyethylene terephthalate blended with Polybutylene terephthalate and Glass Fibers (PET+PBT+GF), etc.

The first portion21can be fixed to the support structure10by ultrasound welding, for example, or through an adhesive substance, suitably interposed between the first portion21and the support structure10.

It is to be noted that, using two different materials for the support structure10and the first portion21of the guide, element20can allow achievement of advantages in terms of resistance to wear due to the action of the thread during its sliding on the same guide element20.

In fact, the material of which the support structure is made has primarily to resist to contact with ink, which can have erosive properties.

If a different material is used for the guide element20, major concern may be dedicated to resistance to the action of the sliding thread.

Furthermore, if the first portion21is not ultrasound welded to the support structure10, more possibilities are available in the choice of the material of the first portion21, since no constraint is present as to compatibility with ultrasound welding.

In the second embodiment, the second portion22can be realized as a shim, mounted on or fixed to the support structure10, on the same side of the first portion21with respect to the nozzles12. In particular, the shim can be interposed between the nozzles12and the first portion21of the guide element20.

As mentioned above, the invention also relates to a method for making the inkjet printhead1.

In general, such method comprises the following steps:providing the support structure10;mounting the firing cells11on the support structure10;mounting the guide element20on the support structure10, for guiding the thread4in a position facing the nozzles12.

In particular, with reference to the second embodiment of the guide element20, the support structure10and the first portion21of the guide element20are initially separated.

Then the method preferably comprises a step of mounting the first portion21of the guide element20on the support structure10in an initial position.

In other words, a projecting portion of the first portion21, which extends on the opposite side of the plate-like base23with respect to the pin24, is inserted in a seat of the support structure10.

Thus, the first portion21of the guide element20is movable on the support structure10in a number of different positions, since the first portion21can be rotated around the axis defined by the longitudinal extension of the pin24and projecting portion.

It is to be noted that since the pin24is eccentrically positioned on the plate-like base23, each position of the first portion21on the support structure10corresponds to a respective position of the thread4with respect to the nozzles12when the machine is in use.

A target position is determined for said guide element20, which corresponds to an arrangement of a thread which is substantially aligned with the symmetry axis S of the nozzles12.

In other words, it is desirable that the thread be positioned along the symmetry axis S of the nozzles12, so that it can be properly and efficiently colored.

Then, through an optical system, the current position of the guide element20with respect to the nozzles12is determined.

If the guide element20is properly positioned, so that a hypothetical thread is arranged along the symmetry axis S of the nozzle arrangement, i.e. if the guide element20is in the target position, the position of the first portion21of the guide element20is correct, and it needs only to be fixed to the support structure10.

If the guide element20is not properly positioned, so that the hypothetical thread guided by said guide element20is not aligned with the symmetry axis S of the nozzle arrangement, i.e. if the guide element20is not in the target position, the first portion21of the guide element20is moved, in order to change correspondingly the position of the guide element20and cause the same to reach the target position.

Preferably the aforementioned optical system is connected to an electronic unit, which processes the data provided by the optical system and compares the current position of the guide element with the target position.

Preferably the electronic unit is adapted to drive, according to said comparison, an electromechanical actuator which moves the first portion21of the guide element20, so that the same guide element20can reach the target position.

In practice, the electromechanical actuator comprises an operative tool which is adapted to engage the hexagonal perimeter of the plate-like base23, in order to rotate the first portion21in a proper position.

Advantageously, the support structure10and the plate-like base23are provided with marking portions25, such as for example marking cavities, in order to let the optical system define their position and properly changing the position of the first portion21if necessary.

Preferably, since the guide element20is provided, the maximum misalignment between the thread4and the nozzles20is less than ±0.13 mm, and more preferably less than ±0.07 mm.

After the guide element20, and in particular the first portion21is arranged in a position such that the guide element20is in its target position, the same first portion21is fixed to the support structure10.

The fixing step can be carried out through an adhesive substance (such as, for example, epoxy resin (Ecobond E3200, DELO VE43309, DELO monopox), acrylate resin, etc.; in particular, the adhesive substance can be interposed between the plate-like base23and the support structure10. The adhesive substance can also fill in partly the seat before the projecting portion is inserted therein.

The adhesive substance allows changes of the first portion21for a few seconds, then it fixes the same first portion21to the support structure10.

As an alternative, ultrasound welding can be employed to fix the first portion21to the support structure10.

It is to be noted that, in both embodiments, the first portion21of guide element20engages the thread4on one side only, i.e. for example the downwardly directed side inFIG. 3or the upwardly directed side inFIG. 5), in order to let the printhead1move without removing the thread4from the machine2.

In fact, the printhead1needs to be moved away from its working position when it has to be replaced, when at the end of the day it has to be positioned in an anti-evaporating non-working position.