DESCRIPTION

[TECHNICAL FIELD]

The present invention relates to a printing machine, in particular a printing machine for textiles. More in detail, the invention relates to a printing machine of the oval type.

[PRIOR ART]

As is known, oval printing machines are fitted with a plurality of plates movable along guides that define a closed path (typically oval); the items to be printed, e.g. garments such as, for example, T-shirts or the like, are positioned on the plates. The plates carry the items to be printed to operating stations arranged along the path of the guides. The operating stations may be silkscreen printing stations, drying stations, stations for "flocking" applications, stations for "foiling" applications, etc.

The Applicant has noticed that the machines known in the art often suffer from important operational limitations.

By way of example, let us consider the case wherein a "flocking" application is required on a digitally printed fabric. The machines currently available cannot appropriately fulfil this requirement. In fact, after having been digitally printed on a different machine, the item must be picked up from that machine, re-positioned on a plate of the oval machine, and then subjected to the desired treatment.

This clearly implies a number of drawbacks, which are due both to the time necessary for moving the item and to the substantial impossibility of positioning the item in a precise manner for executing the "flocking" application with high accuracy relative to the already printed parts. Note that this is only one example, among many others, that may be useful to comprehend the need, felt by the Applicant, for broadening the functionality of traditional oval machines. The Applicant has also observed that the oval silkscreen printing machines known in the art involve very high costs, particularly as concerns the construction of printing matrices. Such costs are industrially bearable only for large production volumes. In other words, the machines known in the art suffer from important criticalities from an economical viewpoint when they have to be used for small production volumes, e.g. samples, which may be limited to as few as 40 items per lot.

[OBJECTS AND SUMMARY OF THE INVENTION] It is therefore one object of the present invention to provide an oval printing machine that offers broadened functionality.

It is another object of the invention to provide an oval printing machine that involves bearable industrial costs for large and small volumes.

It is a further object of the invention to provide an oval printing machine that allows operation at variable printing speed and quality, depending on the requirements of every single production lot.

It is yet another object of the present invention to provide an oval printing machine that can exploit at best the waiting times entailed by the operations being carried out.

These and other objects are substantially achieved through a printing machine as described in the appended claims.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Further features and advantages will become more apparent from the following detailed description of some preferred but non-limiting embodiments of the invention.

This description will refer to the annexed drawings, which are also provided merely as explanatory and non-limiting examples, wherein:

Figure 1 is a schematic perspective view of a machine in accordance with the present invention;

Figure 2 is a simplified plan view of the machine of Figure 1;

Figures 3 and 4 are perspective views of some elements of the machine of Figure 1 ; Figure 5 is a front view of the machine of Figure 1;

Figure 6a shows a detail of one embodiment of the invention;

Figure 6b shows a detail of one embodiment of the invention;

Figure 6c shows a detail of one embodiment of the invention.

[DETAILED DESCRIPTION OF THE INVENTION]

With reference to the appended drawings, numeral 1 designates a printing machine in accordance with the invention.

The printing machine 1 is preferably an oval printing machine for textiles.

The machine 1 comprises, first of all, a guide 10 that defines a path P.

Preferably, the path P is a closed path.

The path P may have a circular, elliptical, oval, etc. shape.

In one embodiment, the path P has two straight sides parallel and close to each other, and two curved portions that connect the homologous ends of said straight sides, as schematically shown by way of example in Figure 2.

The machine 1 further comprises one or more supports 20a-20d that are movable on the guide 10.

The supports 20a-20d are adapted to support items to be printed, e.g. garments.

The supports 20a-20d may consist, in practice, of plates, e.g. substantially rectangular in shape, whereon the textile items to be printed can be laid.

In particular, on each support 20a-20d a respective item to be printed can be arranged.

The supports 20a-20d are fitted with suitable drive members engaged with the guide 10, so that the supports 20a-20d can be moved on the guide 10 along the path P, as schematically shown by arrows Fl, F2 in Figure 2.

The supports 20a-20d can be moved by using different techniques. Some examples that may be taken into account are the driving technique described in International patent application no. PCT/IB2015/059212 by MACHINES HIGHEST MECHATRONIC GMBH, or the technique described in European patent no. EP 2 509 791 Bl to Arioli S.p.A.

It should be noted, however, that the invention is also applicable to printing machines wherein the supports for the items to be printed are moved according to techniques other than those mentioned above.

The machine 1 further comprises one or more operating stations 30a-30c positioned along said path P for processing the items to be printed.

Advantageously, the operating stations 30a-30c comprise at least one silkscreen printing station.

Preferably, the operating stations 30a-30c comprise one or more of:

a drying station;

a flocking station;

a foiling station;

a fixing station;

a preparation station;

a station for loading/unloading the items onto/from the supports 20a-20d.

In accordance with the invention, the machine 1 further comprises a digital printing station 40. The digital printing station 40 is arranged in a specific position along the path P for digitally printing the items supported by the supports 20a-20d. The printing station 40 comprises a structure 41 substantially integral with the guide 10.

The structure 41 preferably comprises a base 41a and a frame 41b.

The frame 41b is preferably mounted on the base 41a and supports the first printing element 42, which will be described later on.

Preferably, the frame 41b comprises first and second uprights 41c-41d, each one extending from a respective portion of said base 41a.

Preferably, the frame 41b comprises also a third upright 41f, interposed between said first upright 41c and said second upright 4 Id.

Preferably, the frame 41b further comprises a first crosspiece 41e mounted on said uprights 41c-41d.

Preferably, the first crosspiece 41e is supported also by said third upright 41f.

In particular, the first and second uprights 41c, 41d have respective engagement zones Al, A2 adapted to be constrained to corresponding constraint zones Bl, B2 of said first crosspiece 41e. Advantageously, also the third upright 41f has an engagement zone A3, adapted to be coupled to a corresponding constraint zone B3 of the first crosspiece 41e.

Preferably, the two uprights 41c-41d are located on opposite sides of the guide 10, so that the first crosspiece 41e extends over two distinct portions of the guide 10.

In other words, in a preferred embodiment both uprights 41c-41d are located externally to the closed path P, as shown in Figure 1, preferably in substantially symmetrical positions relative to the median axis Y of the guide 10.

Preferably, the third upright 41f is located within the area delimited by the path P (Figure 1). As aforementioned, the digital printing station 40 further comprises a first printing element 42 associated with the structure 41 and movable relative to the structure 41.

The function of the first printing element 42 is to carry out digital printing operations on the items supported by the supports 20a-20d.

Preferably, the first printing element 42 can accommodate a number N of colour heads. This number N is related to the machine configuration.

Preferably, the machine configuration takes into account the following factors:

- Print width (in the direction D2 of Figure 2): the number N of print heads grows with the value of this parameter; in particular, the number N can be determined by the following relation: N = (design print width / head footprint), rounded up;

- Number of colours: the higher this datum, the higher the number N of heads. This is a direct relationship when the head can only use one colour; conversely, if multiple-channel heads are used, it will be necessary to consider the maximum number of channels and the maximum number of colours to be used. In this respect, it must be pointed out that the minimum number of colours is 4 (CMYK four-colour process);

- Minimum print resolution: this datum depends on the native resolution of the head.

All heads of one colour will have to be arranged along the same direction (parallel to the direction D2 indicated in Figure 2) and, for the purpose of ensuring drop spacing uniformity, each head must be mechanically constrained to the printing element in such a way that the last nozzle of the preceding head will be positioned, relative to the first nozzle of the next head, at a distance equal to 1" / (native resolution of the head in dpi). Constant nozzle pitch will thus be ensured throughout the row of heads of the same colour along the direction D2.

The head arrays thus arranged will ensure, as the first printing element 42 moves along the direction Dl, printing at native resolution in the direction D2.

Merely by way of example, heads having a native resolution of 150 dpi may be taken into consideration. Due to the above-described arrangement, when the first printing element 42 is moved at its maximum speed (along the direction Dl), printing will occur at a resolution of 150 dpi (direction Dl) x 150 dpi (direction D2). Or, by moving the first printing element 42 at a lower speed along the direction Dl, it will be possible to print at a resolution of 300 dpi (direction Dl) x 150 dpi (direction D2).

If one wants to print at a higher resolution than the native resolution of the head (along the direction D2), it will be necessary to multiply said machine configuration by a predefined factor K. The final resolution achieved in the direction D2 will be equal to the next integer of K*(native resolution in dpi).

It is important to underline that, when multiplying the machine configuration for the purpose of increasing the final resolution in the direction D2, the additional lines of colour heads will have to be mechanically constrained to the printing element in such a way that the nozzles of the additional head array will be so positioned as to provide an offset, in the direction D2, equal to half the pitch of the nozzles of the head array of the printing configuration at native resolution.

The Applicant also wishes to point out that the basic element of the printing element consists of a head of piezoelectric or thermal nature, capable of printing both fixed-size drops and variable-size drops, using the so-called DOD (Drop On Demand) concept or the ink circulation concept, and capable of using both pure inks (which is typical of the CMYK four-colour process) and pre-mixed inks (also known as spot colours).

The first printing element 42 is preferably constrained to the first crosspiece 41e, in a manner such that it can be moved along the first crosspiece 41e.

The first printing element 42 is preferably movable in a substantially straight line, along a first direction Dl .

Preferably, the first direction Dl coincides with the longitudinal development of the first crosspiece 41e.

The first direction Dl is transversal to a second direction D2, in which the guide 10 extends at the digital printing station 40.

Preferably, the first direction Dl is substantially orthogonal to the second direction D2.

Merely by way of example, in the reference system of Figure 2 the first direction Dl is horizontal, while the second direction D2 is vertical.

In one embodiment, the first printing element 42 cannot substantially be moved, while executing printing operations, along the second direction D2.

In this embodiment, the first printing element 42 can only be moved along the first direction Dl (in addition to vertically, towards/away from the item to be printed).

In one embodiment, the first printing element 42 can also be moved along the second direction D2, so as to create an offset between the trajectories (parallel to Dl) followed during successive passes over the item(s) to be printed. This solution can be used, for example, in order to double the print resolution with the same printing element.

Preferably, the first printing element 42 is movable between a first position XI, in which it can execute a printing operation at a first tract Tl of the guide 10, and a second position X2, in which it can execute a printing operation at a second tract T2 of the guide 10.

Preferably, the first tract Tl and the second tract T2 are located on opposite sides relative to a median axis Y of the guide 10.

Preferably, the first tract Tl is substantially parallel to the second tract T2.

Preferably, the supports 20a-20d are moved over the first tract Tl in a first direction (arrow Fl in Figure 2).

Preferably, the supports 20a-20d are moved over the second tract T2 in a second direction (arrow F2 in Figure 2).

Preferably, the second direction is opposite to the first direction. In other words, in a plan view like the one schematized in Figure 2, a support 20a-20d is moved, for example, upwards in the first tract Tl and downwards in the second tract T2.

This is a consequence of the fact that, as aforesaid, the path P is a closed one and the support 20a-20d are always moved clockwise as schematically shown in Figure 2 (or, in a variant embodiment not shown, counterclockwise) during a printing process.

Preferably, the third upright 4 If is interposed between the first tract Tl and the second tract T2. It is thus possible to print, through the first printing element 42, on two different items in a substantially simultaneous manner: the first item is supported by a support 20a-20d positioned on the first tract Tl of the guide 10, while the second item is supported by a support 20a-20d positioned on the second tract T2 of the guide 10.

The Applicant wishes to point out that this allows for more flexible and efficient management of the waiting times entailed by the printing operations.

In fact, the Applicant has verified that, when the digital printing station 40 operates on just one tract of the guide 10, i.e. only processes one item at a time, the time necessary for printing can be estimated to be approx. 4-5 seconds. Conversely, when the digital printing station 40 operates on two tracts (e.g. the above-mentioned first and second tracts Tl, T2) of the guide 10, i.e. it processes two items during each printing step, the time required is approximately twice as much. In other words, there will be a pause of about 10 seconds between one movement of the supports and the next. This pause can advantageously be used for carrying out other operations (preparation, fixing, drying, positioning the items on the supports, etc.), which may require a time longer than 4-5 seconds and which may constitute a "bottleneck" in the timing of the entire process.

In other words, while keeping the throughput of the machine essentially unchanged (e.g. expressed as the number of totally treated items per hour, or items/hour), more time is available for operations that require it, so that they can be carried out in a more accurate, reliable and effective manner.

With this technical solution it is also possible to print the same fabric twice by means of the printing station 40: once at the first tract Tl and again at the second tract T2.

For moving the first printing element 42 vertically (i.e. orthogonally to the plane of the sheet, in the diagram of Figure 2), along the direction Dl and, if available, along the direction D2, respective linear electric motors and/or pneumatic actuators can be used. Such motors/actuators are per se known, and will not therefore be described herein any further. In one embodiment, the printing station 40 comprises, in addition to said first printing element 42, a second printing element 42a (Figures 6a-6c).

The second printing element 42a may essentially have the same technical features as the first printing element 42.

Preferably, the second printing element 42a is mounted on the first crosspiece 41e.

In one embodiment, the second printing element 42a is mounted on the first crosspiece 41e on the side opposite to that of the first printing element 42 with respect to a vertical plane VI substantially parallel to the first direction Dl and passing through the first crosspiece 41e. Figure 6a shows a schematic sectional view of this embodiment in a plane orthogonal to the longitudinal development of the first crosspiece 41e. The second printing element 42a can be made to move along the longitudinal development of the first crosspiece 41e by using technologies and modalities wholly similar to those described in regard to the first printing element 42.

In one embodiment, the second printing element 42a is mounted on a second crosspiece 41e' belonging to said frame 41b and supported by said uprights 41c, 4 Id. The second crosspiece 41e' is mounted on the uprights 41c, 4 Id on the side opposite to that of the first crosspiece 41e with respect to a vertical plane V2 substantially parallel to the first direction Dl and passing through the uprights 41c, 4 Id. Figure 6b shows a schematic sectional view of this embodiment in a plane orthogonal to the longitudinal development of the first crosspiece 41e. The second printing element 42a can be made to move along the longitudinal development of the second crosspiece 41e' by using technologies and modalities wholly similar to those already described for the first printing element 42, with reference to the first crosspiece.

In one embodiment, the second printing element 42a is mounted on the first crosspiece 41e on the same side as the first printing element 42. Preferably, the length of the first crosspiece 41 e in the longitudinal direction is such that the second printing element 42a can be kept inactive at a longitudinal end END of the first crosspiece 41e, while the first printing element 42 is operating on the first tract Tl and on the second tract T2. Figure 6c shows a schematic plan view of this embodiment. The second printing element 42a is movable along the longitudinal development of the first crosspiece 42a, just like the first printing element 42. The movements of the first and second printing elements 42, 42a are controlled in such a way as to avoid any collisions. Note that the second printing element 42a may turn out to be advantageous, for example, for printing white colour on black fabric, before the first printing element 42 prints the actual colours on the same fabric. In addition or as an alternative, the second printing element 42a may be useful to print colours other than white, also on products not treated by the first printing element 42. In Figure 6c, references El, E2 indicate the outermost end-of-travel positions, with respect to the path P, taken by the first printing element 42. As can be observed, the length and position of the first crosspiece 41 e are such that it can support the second printing element 42a with its own end END when the first printing element 42 is in the end-of-travel position El (i.e. the end-of-travel position proximal to the end END of the first crosspiece 41e). Preferably, the guide 10 is partially formed in the structure 41 of the digital printing station 40. In particular, the guide 10 has a first section SI that extends from the digital printing station 40, a second section (S2) formed in the structure 41 of the digital printing station 40, and a third section S3 that extends on the opposite side of the digital printing station 40 with respect to the first section S 1.

In practice, the second section S2 of the digital printing station 40 comprises said first tract Tl and second tract T2.

As aforesaid, the first crosspiece 41 e extends over two distinct portions of the guide 10; said distinct portions are, advantageously, the first tract Tl and the second tract T2.

Preferably, the machine 1 further comprises an enclosure 50, within which said digital printing station 40 is located.

Preferably, the operating stations 30a-30c are not located within the enclosure 50.

In practice, the enclosure 50 delimits the spatial region in which only the digital printing station

40 extends.

Preferably, the enclosure 50 is associated with an adjustment system 60; the system 60 is configured for adjusting the temperature and/or humidity within the enclosure 50.

In this manner, the digital printing station 40 is allowed to operate under controlled environmental conditions, which are typically better than the general conditions of the structures where the machine 1 is located.

The Applicant has noticed, in fact, that printing machines are often used in geographical areas where the climate is particularly dry and the temperature can reach very high and/or very low values. This may lead to serious criticalities for digital printing, because print heads need certain temperature/humidity conditions to work properly. In particular, the Applicant has observed that, in environments where humidity is too low, the ink may dry on the heads, preventing them from operating properly. Likewise, excessively low or high temperatures may cause chemical/physical variations (e.g. viscosity, surface tension, etc.) in the inks, thus preventing correct drop formation.

Thanks to the enclosure 50 and the adjustment system 60, the digital printing station 40 can be made to work in adequate conditions, without nevertheless incurring heavy expenses.

From an operational viewpoint, the following must be pointed out.

The items to be printed are arranged on the supports 20a-20d.

The supports 20a-20d are then moved in order to carry and hold the items at the operating stations 30a-30c and/or at the digital printing station 40.

This means that the supports 20a-20d are moved to respective target positions, and are then held stationary in such positions in order to let the operating stations 30a-30c and/or the digital printing station 40 process the items.

Preferably, one of the supports 20a-20d is stopped on the first tract Tl of the guide 10, and another support 20a-20d is stopped on the second tract T2 of the guide 10.

In other words, said two supports are preferably stopped in different positions belonging to the second section S2 of the guide 10.

In this manner, the digital printing station 40 can process two different items during the same pause between the movements of the supports 20a-20d.

In the case wherein the digital printing station 40 operates on just one tract of the guide 10, only one of the supports 20a-20d will be positioned at the digital printing station 40.

Once the supports 20a-20d have been positioned, the respective stations 30a-30c, 40 can start processing the respective items.

When processing is complete, the supports 20a-20d will be moved again to carry the items to the next station.

The invention offers significant advantages.

First and foremost, the printing machine according to the present invention features broadened functionality, since it allows attaining a broader range of results compared to prior-art machines.

Furthermore, the machine according to the invention entails bearable industrial costs for large and small volumes.

A further advantage of the invention lies in the fact that the machine described and claimed herein can operate at variable printing speed and quality, depending on the requirements of every single production lot. In addition, some preferred embodiments of the invention allow for better exploitation of the waiting times entailed by the operations being carried out.