WO2023237984A1 - Recirculating printer and kit for the recirculation of a printing fluid inside a recirculating printer - Google Patents

Abstract

The recirculating printer (1) comprises: - a print head (2); - a supply assembly (3) for sending the printing fluid (F) to the print head (2); - a recirculation unit (4) for the movement of the printing fluid (F) inside the print head (2) comprising: - a first container (5); - a second container (6); - a first recirculation assembly (7) adapted to move the printing fluid (F) from the first container (5) towards the second container (6) passing through the print head (2); - a second recirculation assembly (8) adapted to move the printing fluid (F) from the second container (6) towards the first container (5) without passing through the print head (2); - an auxiliary recirculation assembly (21) adapted to direct the printing fluid (F) alternately towards the first container (5) or the supply assembly (3).

Description

RECIRCULATING PRINTER AND KIT FOR THE RECIRCULATION

OF A PRINTING FLUID INSIDE A RECIRCULATING PRINTER

Technical Field

The present invention relates to a recirculating printer and a kit for the recirculation of a printing fluid inside a recirculating printer.

Background Art

To date, it is particularly popular to use printers to deliver a printing fluid, such as e.g. an ink or paint, onto the outer surface of certain objects and/or semifinished products in order to change the aesthetic look thereof.

For example, the outer surface of such objects can be printed to make a decoration, to make visible some merchandise and/or commercial information of the product, to insert a logo, etc.

The objects and/or products involved in the aforementioned printing process can be very different from each other, both from the point of view of the material of manufacture and from the point of view of their geometric conformation.

For example, it is common practice to print the outer surface of packaging boxes made of plastic and/or paperboard materials, pieces of fabric or slabs of ceramic material in order to give them special aesthetic effects.

A special category of printers is commonly known as recirculating printer and involves subjecting the printing fluid to a recirculation cycle inside the dispensing head when the same is not being dispensed.

A particular type of recirculating printer is described in patent documents EP2875956B1 and EP3315307B1.

Such a recirculating printer comprises a supply assembly which sends the printing fluid to one or more print heads that deliver it onto the outer surface of the product to be printed.

The supply assembly usually comprises one or more storage tanks of the printing fluid and a pump which draws the printing fluid from the tanks and sends it to the print heads.

Print heads are provided with a plurality of nozzles through which the printing fluid flows out and is distributed onto the product to be printed.

When using the printer, it is often necessary to modulate the flow rate of the printing fluid delivered by the print heads according to working requirements and, in some contexts, it may be necessary to stop dispensing completely.

The non-dispensed printing fluid stays within the print heads and can solidify, thus undergoing deterioration and creating fouling within the print head which can make it difficult for the ink to subsequently flow out of the nozzles.

To overcome these drawbacks, the use of a recirculation unit mounted on board the printer itself is provided which keeps the printing fluid moving inside the print head.

The recirculation unit comprises a first container and a second container of the printing fluid which are small in size compared to the size of the storage tank, are placed adjacent to each other and allocated at the same distance from the ground.

The first and the second containers are usually made in a single body piece.

The first container is connected to both the supply assembly and the print head in a fluidic manner, is located upstream of the print head and receives the printing fluid directly from the supply assembly.

The second container is connected downstream of the print head in a fluidic manner and receives the printing fluid not dispensed by the latter.

The recirculation unit comprises a first recirculation assembly, which moves the printing fluid from the first container towards the print head and the second container, and a second recirculation assembly, which moves the printing fluid from the second container to the first container, without passing through the print head.

The first recirculation assembly usually comprises a first pumping device, which is connected to the first container and to the second container through an air-operated circuit and which draws air from the second container, resulting in a negative pressure there, that is, a lower pressure than atmospheric pressure.

The first container is, usually, kept at atmospheric pressure or at a negative but higher pressure than that of the second container. The pressure gradient between the first container and the second container causes the movement of the printing fluid from the first container to the second container, passing through the print head.

The second recirculation assembly comprises a second pumping device which transfers the printing fluid from the second container to the first container without passing through the print head.

In this way, the printing fluid not dispensed by the print head is made to recirculate between the second container and the first container and can be sent back again to the print head through the activation of the first recirculation assembly.

Moreover, the recirculation unit comprises a treatment assembly of the printing fluid associated with at least one of either the first container or the second container which is activated to adjust some physical parameters of the printing fluid itself.

For example, the treatment assembly comprises a temperature control device which controls the temperature of the printing fluid contained in the container with which it is associated, by heating or cooling it.

The recirculating printers of known type do, however, have some drawbacks which are mainly related to the degradation of certain physical and chemical properties of the printing fluid which may occur during the use of the printers themselves.

Particularly, the rheological properties can be deteriorated and, for example, a decrease in viscosity may occur.

These unpleasant occurrences are mainly attributable to the fact that the size of the first container and of the second container is particularly small and, therefore, the volume of printing fluid subjected to recirculation is very small and is subjected to a large number of recirculations, especially when the printing fluid dispensing is blocked for long periods.

In addition, under such circumstances, the printing fluid is thermally conditioned by the treatment assembly for long intervals of time, which contributes to the rapid degradation of the chemical and physical properties of the printing fluid.

The loss of viscosity of the printing fluid can complicate the subsequent dispensing phase of the same from the print head and/or worsen the relevant ability to set on the surface to be printed, thus generating a poor quality finished product.

Description of the Invention

The main aim of the present invention is to devise a recirculating printer and a kit for the recirculation of a printing fluid inside a recirculating printer which make it possible to limit the degradation of the chemical and physical properties of the printing fluid during the use of the printer itself.

Inside the scope of this aim, the present invention aims to devise a recirculating printer and a kit for the recirculation of a printing fluid inside a recirculating printer which allow limiting the loss of viscosity of the printing fluid.

Another object of the present invention is to devise a recirculating printer and a kit for the recirculation of a printing fluid inside a recirculating printer which enable the quality of the finished product to be improved.

Another object of the present invention is to devise a recirculating printer and a kit for the recirculation of a printing fluid inside a recirculating printer which allow the aforementioned drawbacks of the prior art to be overcome within the framework of a simple, rational, easy and effective to use as well as cost- effective solution.

The aforementioned objects are achieved by this recirculating printer having the characteristics of claim 1.

The aforementioned objects are also achieved by this kit for the recirculation of a printing fluid inside a recirculating printer having the characteristics of claim 10.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a recirculating printer and a kit for the recirculation of a printing fluid inside a recirculating printer, illustrated by way of an indicative, yet non-limiting example, in the attached tables of drawings in which:

Figure 1 is a schematic view of a printer according to the invention;

Figure 2 is a schematic view of a kit according to the invention.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally denotes a recirculating printer.

The recirculating printer 1 comprises at least one print head 2 for the dispensing of at least one printing fluid F.

Within the scope of this disclosure, for simplicity of description and graphical representation, reference is made to a recirculating printer 1 provided with a single print head 2.

Alternative embodiments of the recirculating printer 1 cannot however be ruled out, wherein there is a plurality of print heads 2.

Preferably, the print head 2 comprises at least one dispensing channel of the printing fluid F on the outer surface of at least one product to be printed.

In more detail, the dispensing channel comprises, where the relevant outwardfacing end of the print head 2 is located, at least one nozzle for the outflow of the printing fluid F.

Preferably, there is a plurality of nozzles arranged in mutually side-by-side rows.

The number of nozzles in each row varies depending on the desired print quality of the printed image.

The printing fluid F is preferably ink consisting of a liquid solution inside which dyes or pigment suspensions are dispersed.

Alternative embodiments of the recirculating printer 1 cannot however be ruled out wherein the printing fluid F has a different nature and, e.g., is of the type of a paint, ceramic glaze, ceramic ink or the like.

The product to be printed, as described above, may be made of different materials and/or have widely varying geometric conformation.

For example, the product to be printed may be of the type of an object made of paper and/or cardboard and/or textile material and/or metal material and/or wood material and/or ceramic material, etc.

Again, the geometric conformation of the product to be printed can be highly variable and, e.g., may be of the type of a sheet element (a sheet of paper), a box (a cardboard box), a slab (a ceramic tile), etc.

The recirculating printer 1 comprises at least one supply assembly 3 for sending the printing fluid F to the print head 2.

In the context of this disclosure, the terms downstream and upstream and the verbal terms or phrases derived from them should be understood in relation to the normal direction of movement of the printing fluid F inside the recirculating printer 1 such as, e.g., the direction from the supply assembly 3 towards the print head 2.

The print head 2 is selectively controllable, in a manner substantially known to the technician in the field, to deposit the printing fluid F onto the product to be printed according to a predetermined pattern.

Precisely, the dispensing of the printing fluid F from the print head 2 can occur in a continuous and regular manner or be limited or completely blocked, depending on the particular production requirements.

In the event of the printing fluid F not being dispensed from the print head 2, it remains inside the print head 2 and may often undergo a consolidation process inside the print head 2 itself.

Under these conditions, deposits and fouling of the printing fluid F can form inside the print head 2, which can make it difficult for the printing fluid F to subsequently flow out of the print head 2.

To limit the occurrence of such unpleasant occurrences, the recirculating printer 1 comprises at least one recirculation unit 4 for the movement of the printing fluid F inside the print head 2.

The recirculation unit 4 comprises: at least a first container 5 of the printing fluid F connected downstream of the supply assembly 3 and upstream of the print head 2 in a fluid- operated manner and adapted to receive the printing fluid F coming from the supply assembly 3; at least a second container 6 of the printing fluid F connected downstream of the print head 2 in a fluid- operated manner and adapted to receive the printing fluid F coming from the print head 2; at least a first recirculation assembly 7 adapted to move the printing fluid F from the first container 5 towards the second container 6 passing through the print head 2; at least a second recirculation assembly 8 adapted to move the printing fluid F from the second container 6 towards the first container 5 without passing through the print head 2.

During the normal operation of the recirculating printer 1 , the printing fluid F is sent from the supply assembly 3 towards the first container 5 and, due to the activation of the first recirculation assembly 7, is transferred towards the second container 6, passing through the print head 2.

Precisely, as will be described later, the first recirculation assembly 7 is activated to generate a pressure gradient between the first container 5 and the second container 6 such that the second container 6 has a lower pressure than that of the first container 5.

In this way, the printing fluid F in the first container 5 returns to the second container 6, passing through the print head 2.

In case the printing fluid F is not dispensed from the print head 2, it is sent from the second container 6 towards the first container 5 through the activation of the second recirculation assembly 8.

The printing fluid F is thus made to re-circulate continuously between the first container 5 and the second container 6.

Preferably, the base of the first container 5 and the base of the second container 6 are placed at a first height Hl and a second height H2 respectively, where the second height H2 is greater than the first height Hl.

In the context of this disclosure, it is specified that the term “height” is meant the vertical distance above the ground.

As mentioned, the printing fluid F contained in the first container 5 is kept at a higher pressure than the printing fluid F contained in the second container 6. Therefore, due to the attainment of an equipotential surface between the two containers 5, 6, communicating in a fluid-operated manner to each other, the printing fluid F tends to move from the first container 5 towards the second container 6 passing through the print head 2.

Conveniently, the supply assembly 3 comprises: at least one storage tank 9 of the printing fluid F; at least one feeding pump 10 adapted to take the printing fluid F from the storage tank 9 and to send it to the first container 5.

The feeding pump 10 is positioned between the storage tank 9 and the first container 5 in a fluid- operated manner.

In the particular embodiment shown in the figures, the recirculating printer 1 is connected in a fluid- operated manner to an auxiliary supply assembly A, B, C adapted to send the printing fluid F to the supply assembly 3.

Precisely, the auxiliary supply assembly A, B, C comprises: at least one auxiliary storage tank A of the printing fluid F; at least one auxiliary feeding pump B adapted to take the printing fluid F from the auxiliary storage tank A and to send it to the storage tank 9; at least one auxiliary filtering device C connected in a fluid- operated manner downstream of the auxiliary feeding pump B and upstream of the storage tank 9 and adapted to filter the printing fluid F out of the auxiliary feeding pump B.

The auxiliary storage tank A, in actual facts, consists of a tank or a cistern outside the recirculating printer 1 , which has a larger holding capacity than the storage tank 9 of the recirculating printer 1 and is used to periodically refill the storage tank 9.

In the context of this disclosure, reference is made to a recirculating printer 1 provided with only one storage tank 9.

Alternative embodiments of the recirculating printer 1 cannot, however, be ruled out wherein there is a different number of storage tanks 9.

For example, alternative embodiments of the recirculating printer 1 can be provided where there are two or more storage tanks 9. Advantageously, the supply assembly 3 comprises: at least one collecting channel 11 positioned between the storage tank 9 and the feeding pump 10 in a fluid- operated manner and adapted to transfer the printing fluid F from the storage tank 9 towards the feeding pump 10; at least one delivery channel 12 positioned between the feeding pump 10 and the first container 5 in a fluid- operated manner and adapted to transfer the printing fluid F from the feeding pump 10 towards the first container 5.

When using the recirculating printer 1, the printing fluid F inside the storage tank 9 is sent towards the recirculation unit 4, and more specifically towards the first container 5, from the feeding pump 10.

Specifically, the feeding pump 10 is activated to draw the printing fluid F from the storage tank 9, moving it along the collecting channel 11, and to send the printing fluid F to the first container 5, moving it along the delivery channel 12. The delivery channel 12 is connected to the first container 5 where a relevant end portion is located.

Preferably, the delivery channel 12 is connected to the first container 5 where the upper portion of the latter is located.

The special expedient of inserting the printing fluid F into the first container 5 through the relevant upper portion makes it possible to reduce the turbulence which can be induced in the printing fluid F already contained in the first container 5 and to limit the occurrence of air bubbles in the printing fluid F to be sent to the print head 2.

Conveniently, the supply assembly 3 comprises first filtering means 35 associated with at least one of either the collecting channel 11 or the delivery channel 12 and adapted to filter the printing fluid F passing through the collecting channel 11 and/or the delivery channel 12.

According to the preferred embodiments shown in the figures, the first filtering means 35 consist, e.g., of a filtering device, positioned along the delivery channel 12 and adapted to filter the printing fluid F out of the feeding pump 10. Alternatively and/or in combination thereof, the first filtering means 35 may comprise a filtering device positioned along the collecting channel 11 and adapted to filter the printing fluid F out of the storage tank 9.

Again, in a possible embodiment not shown in the figures, the supply assembly 3 comprises mixing means associated with the storage tank 9 and adapted to periodically mix the printing fluid F contained inside the storage tank 9.

Advantageously, the first recirculation assembly 7 comprises at least one air- operated pumping device 13 connected to at least one of either the first container 5 or the second container 6 in a fluid- operated manner and adapted to pressurize/depressurize at least one of either the first container 5 or the second container 6.

As previously described, the air-operated pumping device 13, which consists e.g. of a compressor, is activated to generate a pressure gradient between the first container 5 and the second container 6 in order to determine the displacement of the printing fluid F between the containers 5 and 6.

According to the preferred embodiments shown in the figures, the first recirculation assembly 7 comprises just one air-operated pumping device 13 connected to the first container 5 and to the second container 6 in a fluid- operated manner and which is activated to depressurize both containers 5 and 6. Precisely, a negative pressure is generated in both containers 5 and 6, i.e., lower than atmospheric pressure, wherein the pressure in the first container 5 is still kept higher than the pressure in the second container 6.

The pressure gradient thus generated between the first container 5 and the second container 6 generates the displacement of the printing fluid F from the first container 5 to the second container 6 through the print head 2.

Conveniently, the first recirculation assembly 7 comprises air-operated connecting means 14a, 14b, 15 adapted to connect the air-operated pumping device 13 to the first container 5 and to the second container 6 in a fluid- operated manner.

Preferably, the air-operated connecting means 14a, 14b, 15 comprise: at least a first air-operated connecting pipe 14a connected to the first container 5 in a fluid- operated manner and adapted to transfer air from the first container 5 to the air-operated pumping device 13; at least a second air-operated connecting pipe 14b connected to the second container 6 in a fluid- operated manner and adapted to transfer air from the second container 6 to the air-operated pumping device 13; at least a third air-operated connecting pipe 15 connected to the air-operated connecting pipes 14a and 14b and to the air-operated pumping device 13 in a fluid- operated manner and adapted to transfer air coming from the air- operated connecting pipes 14a, 14b to the air-operated pumping device 13.

In actual facts, the air-operated pumping device 13 creates a vacuum inside the third connecting pipe 15 which results in the collecting of air from the containers 5, 6 through the first connecting pipe 14a and the second connecting pipe 14b, respectively.

Conveniently, the first recirculation assembly 7 comprises: at least a first air-operated valve element 28 positioned between the air- operated pumping device 13 and the first container 5 and in a fluid- operated manner and adapted to modulate the suction/blowing of air from/into the first container 5 by the air-operated pumping device 13; at least a second air-operated valve element 29 positioned between the air- operated pumping device 13 and the second container 6 in a fluid- operated manner and adapted to modulate the suction/blowing of air from/into the second container 6 by the air-operated pumping device 13.

Advantageously, the first air-operated valve element 28 is associated with the first air-operated connecting pipe 14a, while the second air-operated valve element 29 is associated with the second air-operated connecting pipe 14b.

Preferably, the first air-operated valve element 28 and the second air-operated valve element 29 are air-operated valves which are operationally controllable so as to choke the air intake from the first container 5 and from the second container 6.

In other words, depending on the pressure value measured in the first container 5 and in the second container 6 and depending on the pressure gradient to be maintained between the first container 5 and the second container 6, it is possible to adjust the flow of air coming out of the containers 5, 6 by adjusting the opening/closing of the air-operated valve elements 28, 29.

Conveniently, the first recirculation assembly 7 comprises pressure measuring means 31 adapted to measure the air pressure value within at least one of the air-operated connecting means 14a, 14b, 15, the first container 5 and the second container 6.

For example, the pressure measuring means 31 comprise at least one of (preferably all of): a first vacuum gauge 32a, which is associated with the first air-operated connecting pipe 14a and which is adapted to measure the pressure value inside the first air-operated connecting pipe 14a; a second vacuum gauge 32b, which is associated with the second air- operated connecting pipe 14b and which is adapted to detect the pressure value inside the second air-operated connecting pipe 14b; a third vacuum gauge 32c, which is associated with the third air-operated connecting pipe 15 and which is adapted to detect the pressure value inside the third air-operated connecting pipe 15; a first pressure sensor 33a, which is associated with the first air-operated connecting pipe 14a between the first air-operated valve element 28 and the third air-operated connecting pipe 15 and which is adapted to measure the pressure value inside the first air-operated connecting pipe 14a; a second pressure sensor 33b, which is associated with the second air- operated connecting pipe 14b between the second air-operated valve element 29 and the third air-operated connecting pipe 15 and which is adapted to measure the pressure value inside the second air-operated connecting pipe 14b; a pressure gauge 34, which is associated with the first air-operated connecting pipe 14a between the first air-operated valve element 28 and the first container 5 and which is adapted to measure the pressure value inside the first air-operated connecting pipe 14a.

In this way, depending on the pressure values measured by the pressure measuring means 31, it is possible to modulate the flow rate of air coming out of the containers 5, 6 by operating on the degree of opening/closing of the air- operated valve elements 28, 29.

Preferably, the first recirculation assembly 7 comprises at least one auxiliary vacuum tank 30 associated with the third air-operated connecting pipe 15 in a fluid- operated manner.

Preferably, the third vacuum gauge 32c is placed between the auxiliary vacuum tank 30 and the air-operated pumping device 13.

The air-operated pumping device 13 draws air from the auxiliary vacuum tank 30 by generating a pressure there below the atmospheric pressure which draws air from the first container 5 and from the second container 6.

The fine adjustment of pressure in the containers 5, 6 is achieved through the combined action of the pressure measuring means 31, the first air-operated valve element 28 and the second air-operated valve element 29.

Additionally, the first container 5 is connected upstream of the print head 2 through a first connecting channel 16 which is adapted to transfer the printing fluid F from the first container 5 to the print head 2.

The second container 6 is connected downstream of the print head 2 through a second connecting channel 17 which is adapted to transfer the printing fluid F from the print head 2 towards the second container 6.

According to an alternative embodiment, not shown in the figures, the first recirculation assembly 7 comprises protection means of the air-operated pumping device 13 adapted to prevent the printing fluid F from being transferred from the first container 5 and/or from the second container 6 towards the air-operated pumping device 13.

Preferably, the protection means of the air-operated pumping device 13 comprise a first protection tank, positioned between the first container 5 and the air-operated pumping device 13 in a fluid- operated manner, and a second protection tank, positioned between the second container 6 and the air-operated pumping device 13 in a fluid- operated manner.

Precisely, the first protection tank is associated with the first air-operated connecting pipe 14a and the second protection tank is associated with the second air-operated connecting pipe 14b.

Advantageously, the second recirculation assembly 8 comprises: at least one collecting device 18 connected to the first container 5 and to the second container 6 in a fluid- operated manner and adapted to collect the printing fluid F from the second container 6 and send it towards the first container 5; hydraulic connection means 19, 20 between the collecting device 18, the first container 5 and the second container 6.

Preferably, the hydraulic connection means 19, 20 comprise: at least one collecting pipe 19 positioned between the second container 6 and the collecting device 18 in a fluid- operated manner; at least one delivery pipe 20 positioned between the collecting device 18 and the first container 5 in a fluid- operated manner.

According to the preferred embodiments shown in the figures, the second recirculation assembly 8 comprises second filtering means 36 associated with at least one of either the collecting pipe 19 or the delivery pipe 20 and adapted to filter the printing fluid F passing through the collecting pipe 19 and the delivery pipe 20.

Preferably, the second filtering means 36 comprise a filter 36, positioned along the delivery pipe 20 and adapted to filter the printing fluid F out of the collecting device 18.

Alternatively and/or in combination thereof, the second filtering means 36 comprise an auxiliary filter, positioned along the collecting line 19 and adapted to filter the printing fluid F out of the second container 6.

The collecting device 18 which e.g. consists of a pump, draws the printing fluid F from the second container 6, moving it along the collecting pipe 19 and sends it towards the first container 5, moving it along the delivery pipe 20.

Due to the activation of the first recirculation assembly 7, on the other hand, the printing fluid F returns from the first container 5 to the second container 6 by moving inside the print head 2.

In this way, when the printing fluid F is not dispensed through the print head 2, it does not remain perpetually inside the print head 2 and is made to re-circulate between the print head 2, the first container 5 and the second container 6.

According to the invention, the recirculation unit 4 comprises at least one auxiliary recirculation assembly 21 of the printing fluid F positioned between the second recirculation assembly 8 and the supply assembly 3 and adapted to direct the printing fluid F alternately towards the first container 5 or the supply assembly 3.

Conveniently, the auxiliary recirculation assembly 21 comprises: at least one auxiliary delivery channel 22 associated with the second recirculation assembly 8 and with the supply assembly 3 in a fluid- operated manner; at least one valve element 23 positioned between the second recirculation assembly 8 and the auxiliary delivery channel 22 in a fluid- operated manner and alternately positionable in at least: a first working configuration wherein it diverts the printing fluid F coming from the second container 6 towards the first container 5; and a second working configuration wherein it diverts the printing fluid F coming from the second container 6 towards the supply assembly 3, through the auxiliary delivery channel 22.

Precisely, the valve element 23 is connected to the delivery pipe 20 and to the auxiliary delivery channel 22 and is selectively controllable to divert the printing fluid F alternately towards the supply assembly 3 or towards the first container 5.

For example, the valve element 23 is of the type a three-way valve.

Depending on working requirements, it may be useful to place the valve element 23 alternately in the first working configuration or the second working configuration.

During the blocking phases of the dispensing of the printing fluid F from the print head 2, it may be useful to place the valve element 23 in the second working configuration to send the printing fluid F towards the supply assembly 3. In this way, the printing fluid F is moved along a longer hydraulic path than that it travels when the valve element 23 is in the first working configuration, and thus a larger amount of printing fluid F can be subjected to recirculation and the number of recirculations between the first container 5 and the second container 6 can be reduced.

Next, the printing fluid F is again sent from the supply assembly 3 to the first container 5 through the activation of the feeding pump 10.

As soon as it is again necessary to dispense the printing fluid F from the print head 2, the valve element 23 is allocated to the first working configuration.

In this way, the printing fluid F is moved from the second container 6 towards the first container 5 and can be dispensed from the print head 2 without having to go through the supply assembly 3.

Conveniently, the recirculating printer 1 comprises at least one management and control unit 24 operationally connected to the supply assembly 3, the print head 2 and the recirculation unit 4.

The management and control unit 24 is configured to monitor and manage the operation of the supply assembly 3 and, for example, turns on/off the feeding pump 10 to move the printing fluid F from the storage tank 9 towards the recirculation unit 4.

Again, through the management and control unit 24 it is possible to adjust the operation of the print head 2 and, specifically, it is possible to take action on the opening/closing of the print head nozzles to adjust the flow rate of the printing fluid F.

In addition, the management and control unit 24 is configured to monitor and manage the operation of the first recirculation assembly 7, by turning on/off the air-operated pumping device 13, and of the second recirculation assembly 8, by turning on/off the collecting device 18.

Conveniently, the recirculating printer 1 comprises at least one of: first detection means associated with the first container 5 and adapted to detect the amount of the printing fluid F in the first container 5; and second detection means associated with the second container 6 and adapted to detect the amount of the printing fluid F in the second container 6.

For simplicity of representation, the first and second detection means are not represented in the figures.

The first and second detection means are operationally connected to the management and control unit 24.

The first detection means comprise, e.g., a first level sensor associated with the first container 5 and adapted to detect the level of printing fluid F in the first container 5.

The second detection means comprise, e.g., a second level sensor associated with the second container 6 and adapted to detect the level of printing fluid F in the second container 6.

The first level sensor and the second level sensor can be, e.g., of the type of optical sensors, magnetic sensors, floating bodies, etc.

The management and control unit 24, depending on the data detected by the first level sensor and by the second level sensor, turns on/off the first recirculation assembly 7 and the second recirculation assembly 8 in order to ensure a certain filling (previously established) of the first container 5 and of the second container 6.

The management and control unit 24 is configured to manage the operation of the auxiliary recirculation assembly 21 and, specifically, takes action to alternately position the valve element 23 in the first working configuration or the second working configuration.

A special way of adjusting the auxiliary recirculation assembly 21 involves, for example, the use of a timing device which communicates to the management and control unit 24 the elapsed time interval since the last dispensing of printing fluid F from the print head 2.

The management and control unit 24 can place the valve element 23 in the second working configuration, e.g., after a predetermined time interval has elapsed since the last dispensing of printing fluid F from the print head 2.

As soon as the dispensing of the printing fluid F from the print head 2 is reactivated, the valve element 23 is placed by the management and control unit 24 in the first working configuration.

An alternative mode of operation for adjusting the auxiliary recirculation assembly 21 through the management and control unit 24 may involve the management and control unit 24 placing the valve element 23 in the second working configuration immediately after the interruption of the dispensing of the printing fluid F from the print head 2.

Conveniently, the recirculating printer 1 comprises treatment means 25 of the printing fluid F associated with at least one of the storage tank 9, the first container 5 or the second container 6 and adapted to adjust at least one physical parameter of the printing fluid F.

Preferably, the treatment means 25 comprise at least one temperature control device which is adapted to cool or heat the printing fluid F.

For example, the temperature control device may comprise an electrical resistance and/or a cooling member.

Conveniently, the recirculating printer 1 comprises recovery means 26 of the printing fluid F out of the print head 2 during the cleaning operations of the print head 2.

During the cleaning operations of the print head 2, it is usually planned to increase the pressure inside the print head 2, operating on the first recirculation assembly 7, in order to purge the nozzles by the forced outflow of a small amount of printing fluid F from the nozzles themselves.

The recovery means 26 preferably comprise a collecting container placed under the print head 2 and adapted to receive the printing fluid F out of the nozzles of the print head 2 during the cleaning operations.

According to a further aspect, the present invention relates to a kit 27 for the recirculation of a printing fluid inside a recirculating printer.

The kit 27 comprises: at least one supply assembly 3 for sending at least one printing fluid F to at least one print head 2 of at least one recirculating printer 1 ; at least one recirculation unit 4 for the movement of the printing fluid F inside the print head 2 comprising: at least a first container 5 of printing fluid F connected downstream of the supply assembly 3 in a fluid- operated manner and connectable upstream of the print head 2 in a fluid- operated manner and adapted to receive the printing fluid F coming from the supply assembly 3; at least a second container 6 of the printing fluid F connectable downstream of the print head 2 in a fluid- operated manner and adapted to receive the printing fluid F coming from the print head 2; at least a first recirculation assembly 7 adapted to move the printing fluid F from the first container 5 towards the second container 6 passing through the print head 2; at least a second recirculation assembly 8 adapted to move the printing fluid F from the second container 6 towards the first container 5 without passing through the print head 2.

According to the invention, the recirculation unit 4 comprises at least one auxiliary recirculation assembly 21 of the printing fluid F positioned between the second recirculation assembly 8 and the supply assembly 3 in a fluid- operated manner and adapted to direct the printing fluid F alternately towards the first container 5 or the supply assembly 3.

The kit 27 has additional characteristics that are the same as those described previously for the recirculating printer 1 , a description to which is fully referred to.

The operation of the recirculating printer 1 according to the invention is substantially as follows.

The printing fluid F is sent to the recirculation unit 4 and, specifically, to the first container 5 through the activation of the supply assembly 3.

At this point, the first recirculation assembly 7 is activated which causes a pressure gradient between the first container 5 and the second container 6 and which causes the printing fluid F to flow from the first container 5 towards the second container 6, passing through the print head 2.

During the active printing phase of the recirculating printer 1, i.e., when the print head 2 is to dispense the printing fluid F, the print head 2 is selectively controlled, in a per se known way, to make the printing fluid F flow out through its nozzles; any excess printing fluid F in the print head 2 during dispensing can re-circulate, i.e., reach the second container 6 and return to the first container 5 through the second recirculation assembly 8, with the valve element 23 placed in the first working configuration.

During the resting phase of the recirculating printer 1, i.e., when the print head 2 is not to dispense the printing fluid F, the print head 2 is selectively controlled, in a per se known way, so as not to make the printing fluid F flow out.

Under this circumstance, that is, during the resting phase of the recirculating printer 1, the printing fluid F can be made to re-circulate from the second container 6 towards the first container 5 in two ways: through the second recirculation assembly 8, with the valve element 23 placed in the first working configuration; or alternatively and more conveniently, through the auxiliary recirculation assembly 21, i.e., by positioning the valve element 23 in the second working configuration so that the printing fluid F in the second container 6 is sent to the supply assembly 3 and, through the latter, returns to the first container 5.

As soon as it is again necessary to dispense the printing fluid F from the print head 2, the valve element 23 is repositioned to the first working configuration so that the printing fluid F in the second container 6 can return to the first container 5 without passing through the supply assembly 3.

It has in practice been ascertained that the described invention achieves the intended objects.

Particularly, the recirculating printer and the kit according to the invention make it possible to limit the degradation of the chemical and physical properties of the printing fluid during the use of the printer itself.

In fact, the special expedient of providing the auxiliary recirculation assembly allows the printing fluid to travel a longer path than is normally the case in recirculating printers of known type. In this way, the number of recirculations between the first container and the second container can be decreased, thus reducing the occurrence of physical deterioration of the printing fluid.

In detail, the recirculating printer and the kit according to the invention make it possible to limit the loss of viscosity of the printing fluid during the use of the recirculating printer itself.

Additionally, thanks to the possibility to limit the deterioration of the physical properties of the printing fluid and the possibility to limit viscosity reduction, the subsequent dispensing of the printing fluid from the print head is simplified, thus facilitating the attachment thereof to the outer surface of the product to be printed.

This makes it possible to obtain high-quality finished products, especially in terms of printed image definition.

Claims

1 ) Recirculating printer ( 1 ) comprising : at least one print head (2) for the dispensing of at least one printing fluid (F); at least one supply assembly (3) for sending said printing fluid (F) to said print head (2); at least one recirculation unit (4) for the movement of said printing fluid (F) inside said print head (2) comprising: at least a first container (5) of said printing fluid (F) connected downstream of said supply assembly (3) and upstream of said print head (2) in a fluid- operated manner and adapted to receive said printing fluid (F) coming from said supply assembly (3); at least a second container (6) of said printing fluid (F) connected downstream of said print head (2) in a fluid- operated manner and adapted to receive said printing fluid (F) coming from said print head (2); at least a first recirculation assembly (7) adapted to move said printing fluid (F) from said first container (5) towards said second container (6) passing through said print head (2); at least a second recirculation assembly (8) adapted to move said printing fluid (F) from said second container (6) towards said first container (5) without passing through said print head (2); characterized by the fact that said recirculation unit (4) comprises at least one auxiliary recirculation assembly (21) of said printing fluid (F) positioned between said second recirculation assembly (8) and said supply assembly (3) in a fluid- operated manner and adapted to direct said printing fluid (F) alternately towards said first container (5) or said supply assembly (3).

2) Recirculating printer (1) according to claim 1, characterized by the fact that said auxiliary recirculation assembly (21) comprises: at least one auxiliary delivery channel (22) associated with said second recirculation assembly (8) and with said supply assembly (3) in a fluid- operated manner; at least one valve element (23) positioned between said second recirculation assembly (8) and said auxiliary delivery channel (22) in a fluid- operated manner and alternately positionable in at least: a first working configuration wherein it diverts said printing fluid (F) coming from said second container (6) towards said first container (5); and a second working configuration wherein it diverts said printing fluid (F) coming from said second container (6) towards said supply assembly (3), through said auxiliary delivery channel (22).

3) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that said supply assembly (3) comprises: at least one storage tank (9) of said printing fluid (F); at least one feeding pump (10) adapted to take said printing fluid (F) from said storage tank (9) and to send it to said first container (5), said feeding pump (10) being positioned between said storage tank (9) and said first container (5) in a fluid- operated manner.

4) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that said supply assembly (3) comprises: at least one collecting channel (11) positioned between said storage tank (9) and said feeding pump (10) in a fluid- operated manner and adapted to transfer said printing fluid (F) from said storage tank (9) towards said feeding pump (10); at least one delivery channel (12) positioned between said feeding pump (10) and said first container (5) in a fluid- operated manner and adapted to transfer said printing fluid (F) from said feeding pump (10) towards said first container (5).

5) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that said first recirculation assembly (7) comprises at least one air-operated pumping device (13) connected to at least one of either said first container (5) or said second container (6) in a fluid- operated manner and adapted to pressurize/depressurize at least one of either said first container (5) or said second container (6).

6) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that said first recirculation assembly (7) comprises: at least a first air-operated valve element (28) positioned between said air- operated pumping device (13) and said first container (5) in a fluid- operated manner and adapted to modulate the suction/blowing of air from/into said first container (5) by said air-operated pumping device (13); at least a second air-operated valve element (29) positioned between said air-operated pumping device (13) and said second container (6) in a fluid- operated manner and adapted to modulate the suction/blowing of air from/into said second container (6) by said air-operated pumping device (13).

7) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that said second recirculation assembly (8) comprises: at least one collecting device (18) connected to said first container (5) and to said second container (6) in a fluid- operated manner and adapted to collect said printing fluid (F) from said second container (6) and send it towards said first container (5); hydraulic connection means (19, 20) between said collecting device (18), said first container (5) and said second container (6).

8) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that said hydraulic connection means (19, 20) comprise: at least one collecting pipe (19) positioned between said second container (6) and said collecting device (18) in a fluid- operated manner; at least one delivery pipe (20) positioned between said collecting device (18) and said first container (5) in a fluid- operated manner.

9) Recirculating printer (1) according to one or more of the preceding claims, characterized by the fact that it comprises recovery means (26) of said printing fluid (F) exiting said print head (2) during the cleaning operations of said print head (2).

10) Kit (27) for the recirculation of a printing fluid inside a recirculating printer, comprising: at least one supply assembly (3) for sending at least one printing fluid (F) to at least one print head (2) of at least one recirculating printer (1); at least one recirculation unit (4) for the movement of said printing fluid (F) inside said print head (2) comprising: at least a first container (5) of said printing fluid (F) connected downstream of said supply assembly (3) in a fluid- operated manner and connectable upstream of said print head (2) in a fluid- operated manner and adapted to receive said printing fluid (F) coming from said supply assembly (3); at least a second container (6) of said printing fluid (F) connectable downstream of said print head (2) in a fluid- operated manner and adapted to receive said printing fluid (F) coming from said print head (2); at least a first recirculation assembly (7) adapted to move said printing fluid (F) from said first container (5) towards said second container (6) passing through said print head (2); at least a second recirculation assembly (8) adapted to move said printing fluid (F) from said second container (6) towards said first container (5) without passing through said print head (2); characterized by the fact that said recirculation unit (4) comprises at least one auxiliary recirculation assembly (21) of said printing fluid (F) positioned between said second recirculation assembly (8) and said supply assembly (3) in a fluid- operated manner and adapted to direct said printing fluid (F) alternately towards said first container (5) or said supply assembly (3).