Patent Publication Number: US-10773530-B2

Title: Printing machine

Description:
BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     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. 
     2. The Relevant Technology 
     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: 
         FIG. 1  is a schematic perspective view of a machine in accordance with the present invention; 
         FIG. 2  is a simplified plan view of the machine of  FIG. 1 ; 
         FIGS. 3 and 4  are perspective views of some elements of the machine of  FIG. 1 ; 
         FIG. 5  is a front view of the machine of  FIG. 1 ; 
         FIG. 6 a    shows a detail of one embodiment of the invention; 
         FIG. 6 b    shows a detail of one embodiment of the invention; 
         FIG. 6 c    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  FIG. 2 . 
     The machine  1  further comprises one or more supports  20   a - 20   d  that are movable on the guide  10 . 
     The supports  20   a - 20   d  are adapted to support items to be printed, e.g., garments. 
     The supports  20   a - 20   d  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  20   a - 20   d  a respective item to be printed can be arranged. 
     The supports  20   a - 20   d  are fitted with suitable drive members engaged with the guide  10 , so that the supports  20   a - 20   d  can be moved on the guide  10  along the path P, as schematically shown by arrows F 1 , F 2  in  FIG. 2 . 
     The supports  20   a - 20   d  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 B1 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  30   a - 30   c  positioned along said path P for processing the items to be printed. 
     Advantageously, the operating stations  30   a - 30   c  comprise at least one silkscreen printing station. 
     Preferably, the operating stations  30   a - 30   c  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  20   a - 20   d.          

     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  20   a - 20   d.    
     The printing station  40  comprises a structure  41  substantially integral with the guide  10 . 
     The structure  41  preferably comprises a base  41   a  and a frame  41   b.    
     The frame  41   b  is preferably mounted on the base  41   a  and supports the first printing element  42 , which will be described later on. 
     Preferably, the frame  41   b  comprises first and second uprights  41   c - 41   d , each one extending from a respective portion of said base  41   a.    
     Preferably, the frame  41   b  comprises also a third upright  41   f , interposed between said first upright  41   c  and said second upright  41   d.    
     Preferably, the frame  41   b  further comprises a first crosspiece  41   e  mounted on said uprights  41   c - 41   d.    
     Preferably, the first crosspiece  41   e  is supported also by said third upright  41   f.    
     In particular, the first and second uprights  41   c ,  41   d  have respective engagement zones A 1 , A 2  adapted to be constrained to corresponding constraint zones B 1 , B 2  of said first crosspiece  41   e.    
     Advantageously, also the third upright  41   f  has an engagement zone A 3 , adapted to be coupled to a corresponding constraint zone B 3  of the first crosspiece  41   e.    
     Preferably, the two uprights  41   c - 41   d  are located on opposite sides of the guide  10 , so that the first crosspiece  41   e  extends over two distinct portions of the guide  10 . 
     In other words, in a preferred embodiment both uprights  41   c - 41   d  are located externally to the closed path P, as shown in  FIG. 1 , preferably in substantially symmetrical positions relative to the median axis Y of the guide  10 . 
     Preferably, the third upright  41   f  is located within the area delimited by the path P ( FIG. 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  20   a - 20   d.    
     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 D 2  of  FIG. 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 D 2  indicated in  FIG. 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 D 2 . 
     The head arrays thus arranged will ensure, as the first printing element  42  moves along the direction D 1 , printing at native resolution in the direction D 2 . 
     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 D 1 ), printing will occur at a resolution of 150 dpi (direction D 1 )×150 dpi (direction D 2 ). Or, by moving the first printing element  42  at a lower speed along the direction D 1 , it will be possible to print at a resolution of 300 dpi (direction D 1 )×150 dpi (direction D 2 ). 
     If one wants to print at a higher resolution than the native resolution of the head (along the direction D 2 ), it will be necessary to multiply said machine configuration by a predefined factor K. The final resolution achieved in the direction D 2  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 D 2 , 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 D 2 , 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  41   e , in a manner such that it can be moved along the first crosspiece  41   e.    
     The first printing element  42  is preferably movable in a substantially straight line, along a first direction D 1 . 
     Preferably, the first direction D 1  coincides with the longitudinal development of the first crosspiece  41   e.    
     The first direction D 1  is transversal to a second direction D 2 , in which the guide  10  extends at the digital printing station  40 . 
     Preferably, the first direction D 1  is substantially orthogonal to the second direction D 2 . 
     Merely by way of example, in the reference system of  FIG. 2  the first direction D 1  is horizontal, while the second direction D 2  is vertical. 
     In one embodiment, the first printing element  42  cannot substantially be moved, while executing printing operations, along the second direction D 2 . 
     In this embodiment, the first printing element  42  can only be moved along the first direction D 1  (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 D 2 , so as to create an offset between the trajectories (parallel to D 1 ) 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 X 1 , in which it can execute a printing operation at a first tract T 1  of the guide  10 , and a second position X 2 , in which it can execute a printing operation at a second tract T 2  of the guide  10 . 
     Preferably, the first tract T 1  and the second tract T 2  are located on opposite sides relative to a median axis Y of the guide  10 . 
     Preferably, the first tract T 1  is substantially parallel to the second tract T 2 . 
     Preferably, the supports  20   a - 20   d  are moved over the first tract T 1  in a first direction (arrow F 1  in  FIG. 2 ). 
     Preferably, the supports  20   a - 20   d  are moved over the second tract T 2  in a second direction (arrow F 2  in  FIG. 2 ). 
     Preferably, the second direction is opposite to the first direction. 
     In other words, in a plan view like the one schematized in  FIG. 2 , a support  20   a - 20   d  is moved, for example, upwards in the first tract T 1  and downwards in the second tract T 2 . 
     This is a consequence of the fact that, as aforesaid, the path P is a closed one and the support  20   a - 20   d  are always moved clockwise as schematically shown in  FIG. 2  (or, in a variant embodiment not shown, counter clockwise) during a printing process. 
     Preferably, the third upright  41   f  is interposed between the first tract T 1  and the second tract T 2 . 
     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  20   a - 20   d  positioned on the first tract T 1  of the guide  10 , while the second item is supported by a support  20   a - 20   d  positioned on the second tract T 2  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 T 1 , T 2 ) 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 T 1  and again at the second tract T 2 . 
     For moving the first printing element  42  vertically (i.e., orthogonally to the plane of the sheet, in the diagram of  FIG. 2 ), along the direction D 1  and, if available, along the direction D 2 , 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  42   a  ( FIGS. 6 a -6 c   ). 
     The second printing element  42   a  may essentially have the same technical features as the first printing element  42 . 
     Preferably, the second printing element  42   a  is mounted on the first crosspiece  41   e.    
     In one embodiment, the second printing element  42   a  is mounted on the first crosspiece  41   e  on the side opposite to that of the first printing element  42  with respect to a vertical plane V 1  substantially parallel to the first direction D 1  and passing through the first crosspiece  41   e .  FIG. 6 a    shows a schematic sectional view of this embodiment in a plane orthogonal to the longitudinal development of the first crosspiece  41   e . The second printing element  42   a  can be made to move along the longitudinal development of the first crosspiece  41   e  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  42   a  is mounted on a second crosspiece  41   e ′ belonging to said frame  41   b  and supported by said uprights  41   c ,  41   d . The second crosspiece  41   e ′ is mounted on the uprights  41   c ,  41   d  on the side opposite to that of the first crosspiece  41   e  with respect to a vertical plane V 2  substantially parallel to the first direction D 1  and passing through the uprights  41   c ,  41   d .  FIG. 6 b    shows a schematic sectional view of this embodiment in a plane orthogonal to the longitudinal development of the first crosspiece  41   e . The second printing element  42   a  can be made to move along the longitudinal development of the second crosspiece  41   e ′ 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  42   a  is mounted on the first crosspiece  41   e  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  42   a  can be kept inactive at a longitudinal end END of the first crosspiece  41   e , while the first printing element  42  is operating on the first tract T 1  and on the second tract T 2 .  FIG. 6 c    shows a schematic plan view of this embodiment. The second printing element  42   a  is movable along the longitudinal development of the first crosspiece  42   a , just like the first printing element  42 . The movements of the first and second printing elements  42 ,  42   a  are controlled in such a way as to avoid any collisions. Note that the second printing element  42   a  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  42   a  may be useful to print colours other than white, also on products not treated by the first printing element  42 . In  FIG. 6 c   , references E 1 , E 2  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  42   a  with its own end END when the first printing element  42  is in the end-of-travel position E 1  (i.e., the end-of-travel position proximal to the end END of the first crosspiece  41   e ). 
     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 S 1  that extends from the digital printing station  40 , a second section (S 2 ) formed in the structure  41  of the digital printing station  40 , and a third section S 3  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 S 2  of the digital printing station  40  comprises said first tract T 1  and second tract T 2 . 
     As aforesaid, the first crosspiece  41   e  extends over two distinct portions of the guide  10 ; said distinct portions are, advantageously, the first tract T 1  and the second tract T 2 . 
     Preferably, the machine  1  further comprises an enclosure  50 , within which said digital printing station  40  is located. 
     Preferably, the operating stations  30   a - 30   c  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  20   a - 20   d.    
     The supports  20   a - 20   d  are then moved in order to carry and hold the items at the operating stations  30   a - 30   c  and/or at the digital printing station  40 . 
     This means that the supports  20   a - 20   d  are moved to respective target positions, and are then held stationary in such positions in order to let the operating stations  30   a - 30   c  and/or the digital printing station  40  process the items. 
     Preferably, one of the supports  20   a - 20   d  is stopped on the first tract T 1  of the guide  10 , and another support  20   a - 20   d  is stopped on the second tract T 2  of the guide  10 . 
     In other words, said two supports are preferably stopped in different positions belonging to the second section S 2  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  20   a - 20   d.    
     In the case wherein the digital printing station  40  operates on just one tract of the guide  10 , only one of the supports  20   a - 20   d  will be positioned at the digital printing station  40 . 
     Once the supports  20   a - 20   d  have been positioned, the respective stations  30   a - 30   c ,  40  can start processing the respective items. 
     When processing is complete, the supports  20   a - 20   d  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.