Ink recirculating system for an inkjet printer

1 . An ink recirculating system for an inkjet printer, comprising:

a) a tank for said ink, comprising:

a body delimiting a cavity having an upper and a lower portion, wherein:

the lower portion comprises a side wall, which converges towards a bottom and closing wall of the tank, and has a circular, decreasing cross-section;

an outlet duct for the outlet of the ink from the tank, provided inside the cavity of the tank;

wherein said outlet duct is coaxial to a longitudinal axis of the tank;

an inlet opening for the ink to be moved out of the tank, provided above and near said bottom and closing wall;

an inlet duct for supplying the inlet in the tank to be mixed, comprising:

an end portion having an opening for the ink supply to the tank,

wherein said end portion of the inlet duct is provided in the lower portion of the tank, in correspondence with a circular sector;

b) a pump in fluid communication with said outlet duct and said inlet duct, to convey under pressure an ink present in the tank from said outlet duct to said inlet duct;

wherein

the end portion of the first ink inlet duct is substantially tangent to a portion of the circular sector of the side wall, of the lower portion of the tank, such as to create a substantially swirling flow in the ink present in the tank and a mixing of the ink or components thereof present in the tank, wherein the substantially swirling flow in the ink starts from the lower portion of the tank.

2 . The ink recirculating system according to claim 1 , further including a ventilation duct.

3 . The ink recirculating system according to claim 1 , further including at least one sensor adapted to detect the level of ink in the tank.

4 . The ink recirculating system according to claim 1 , wherein the opening ( 10 B) of the end portion ( 10 A) of the inlet duct ( 10 ) is provided at a distance (D 1 ) from the bottom wall ( 2 F) of the tank between 80% and 20% of the overall height (D 2 ) of the converging sidewall ( 2 E) of the tank ( 2 ).

5 . The ink recirculating system according to claim 4 , wherein the distance (D 1 ) is between 30% and 60% of the height (D 2 ).

6 . The ink recirculating system according to claim 1 , wherein the opening ( 10 B) of the end portion ( 10 A) of the inlet duct ( 10 ) is provided below or at the same distance as the opening ( 9 A) of the outlet duct ( 9 ) for the ink outlet from the tank.

7 . The ink recirculating system according to claim 1 , wherein a distance (D 3 ) of said opening ( 9 A) of the outlet duct ( 9 ) from the bottom wall ( 2 F) is between 1% and 25% of the overall inner height (D 12 ) of the tank.

8 . The ink recirculating system according to claim 7 , wherein the distance (D 3 ) is between 5% and 15% of this height (D 12 ).

9 . The ink recirculating system according to claim 8 , wherein the distance (D 3 ) is equal to about 10% of the overall inner height (D 12 ).

10 . The ink recirculating system according to claim 1 , wherein the tank comprises therein and at the bottom wall thereof a filtering element and in that said opening of the outlet duct is housed inside said filtering element, so as to protect components of the system to which the outlet duct supplies the ink.

11 . The ink recirculating system according to claim 1 , characterized in that the flow rate (P) of the ink generated by the pump ( 11 ) is between: 1 m/s and 15 m/s, wherein said flow rate leaving the opening ( 10 B) is calculated by dividing the volume of the ink fed in the time unit by the pump ( 11 ) to the duct ( 10 ) by the cross-section of the outlet opening ( 10 B) of said duct ( 10 ).

12 . The ink recirculating system according to claim 11 , wherein the flow rate (P) of the ink generated by the pump ( 11 ) is between 3 m/s and 7 m/s.

13 . The ink recirculating system according to claim 12 , characterized in that the flow rate (P) of the ink generated by the pump ( 11 ) is equal to about 5 m/s.

14 . The ink recirculating system according to claim 1 , wherein the tank comprises therein and at the bottom wall thereof a filtering element and in that said opening of the outlet duct is housed inside said filtering element, so as to protect components of the system to which the outlet duct supplies the ink, wherein the filtering element comprises one or more of the following features:

the filtering element has a body having a substantially circular cross-section; or

the filtering element rests against the bottom wall of the tank, or

the filtering element closes the tank at the bottom; or

the filtering element is coaxial to a longitudinal axis of the tank; or

the filtering element having a body that is cylindrical in shape including an upper wall, a lower wall and a side wall.

15 . The ink recirculating system according to claim 14 , wherein the upper wall has an opening which extends axially through the upper wall and is adapted to be penetrated in a sealed manner by an end portion of the outlet duct for the ink outlet, so that the opening is axially housed inside the filtering element.

16 . The ink recirculating system according to claim 1 , wherein a lower wall of a filtering element rests against the bottom wall of the tank and is flush housed in a recessed seat, obtained in the bottom wall of the tank.

17 . The ink recirculating system according to claim 10 , wherein the tank is substantially closed at the bottom by the filtering element, and the inclined wall of the tank, at the bottom, substantially reaches the filtering element, or it reaches a small distance from the filtering element, so as to limit the portion in contact with the ink, of the bottom wall of the tank, to a limited size circular crown.

18 . The ink recirculating system according to claim 10 , wherein the filtering element has a height between 100% and 50% of the overall height of the lower portion of the tank.

19 . The ink recirculating system according to claim 10 , wherein the filtering element has a height between 100% and 80% of the overall height, and a diameter of its side wall between 100% and 50% of the diameter of the bottom wall of the tank.

20 . The ink recirculating system according to claim 10 , wherein the side wall is between 100% and 80% of the diameter of the bottom wall of the tank.

21 . The ink recirculating system according to claim 1 , characterized that the tank ( 2 ) comprises one or more of the following features:

the body ( 2 A) of the tank ( 2 ) has an axial symmetry and also the upper portion ( 2 C) thereof has a circular cross-section, having an inner diameter (D 9 ) which is constant and equal to the maximum inner diameter (D 10 ) of the lower portion ( 2 D) of the tank having the side wall ( 2 E) converging towards the bottom wall ( 2 F) of the tank; or

the height (D 2 ) of the lower portion is between 20% and 40% of the height (D 10 ) of the upper portion ( 2 C) of the tank; or

the height (D 2 ) of the lower portion is between 20% and 40% of the height (D 10 ) of the upper portion ( 2 C) of the tank is equal to about 30% of the height (D 10 ); or

the converging wall ( 2 E) is inclined by an angle (K) between 100° and 170°; or

the converging wall ( 2 E) is inclined by an angle (K) between 120° and 150°; or

the tank has a ratio between the maximum height/diameter which is between 1:1 and 2.5:1; or the tank has a ratio between the maximum height/diameter which is between equal to about 2:1; or

the tank has a volume between 0.21 and 61; or

the tank has a volume between 0.51 and 21; or

the tank has a volume equal to about 11; or

the tank is sized and shaped in such a way as to provide an optimal level (M) for filling the tank which is provided at a distance (D 20 ) from the bottom ( 2 F) of the tank between 40% and 70% of the overall inner height (D 16 ) of the tank, so that the tank provides a wall ( 2 J) of the tank not occupied by the ink, which has a height (D 15 ) which is between 20% and 60% of the overall height (D 16 ) of the tank; or

the tank is sized and shaped in such a way as to provide an optimal level (M) for filling the tank which is provided at a distance (D 20 ) from the bottom ( 2 F) of the tank between 40% and 70% of the overall inner height (D 16 ) of the tank, so that the tank provides a wall ( 2 J) of the tank not occupied by the ink, which has a height (DIS) which is between 30% and 40% of the overall height (D 16 ) of the tank; or

the duct ( 9 ) for the ink outlet from the tank is coaxial to the longitudinal axis (L) of the tank, and is a straight duct; or

the inlet duct ( 10 ) is a flexible plastic tube; or

the inlet duct ( 10 ) has an inner diameter between 1.0 mm and 5.0 mm; or

the inlet duct ( 10 ) has a substantially helicoidal course, and forms an angle equal to about 360° or greater than 360° from its upper end portion to the lower one ( 10 A); or

the converging wall ( 2 E) has a regular cross-section, coaxial to the longitudinal axis (L) of the tank and decreasing towards the bottom of the tank; or

the converging wall ( 2 E) has a circular or elliptical or polygonal in shape.

22 . The ink recirculating system according to claim 1 , characterized in that the tank ( 2 ) comprises means ( 15 ) for fixing the end portion ( 10 A) of the inlet duct ( 10 ) in the desired position, tangent to the inclined wall ( 2 E) of the lower part ( 2 D) of the tank,

wherein the fixing means ( 15 ) comprise a fixing element ( 15 A) and a shaped seat ( 15 B) adapted to at least partially house said shaped element ( 15 A), provided in the inclined wall ( 2 E) of the lower part ( 2 D) of the tank and forming a recess in said sloping wall.

23 . The ink recirculating system according to claim 1 , characterized that the tank ( 2 ) comprises:

at least one second inlet duct ( 17 ) for the inlet into the tank of: ink and/or ink components, in fluid communication:

with a inkjet printer printhead ( 5 ), to convey the ink not used by said printhead ( 5 ) into the tank; or

with a refill module ( 7 ), adapted to supply the ink or the components thereof consumed during printing to the tank ( 2 ); and in that said second inlet duct ( 17 ) comprises one or more of the following features:

said second inlet duct ( 17 ) provides an opening ( 17 A) for discharging the liquid recirculating in said second duct ( 17 ) into the tank, wherein said opening ( 17 A) is provided in the upper portion ( 2 C) of the tank and above an optimal level (M) of the ink in the tank, or

the second inlet duct ( 17 ) provides an opening ( 17 A) for discharging the liquid recirculating in said second duct ( 17 ) into the tank, and a guide element ( 17 B) comprising a sheet inclined towards the bottom of the tank, adapted to guide said liquid up to an inner side wall ( 2 J) of the upper portion ( 2 C) of the tank, wherein a free edge ( 17 C) of said guide element is provided at a distance (D 13 ) from the inner face of the wall ( 2 J) of the tank between 1 mm and 5 mm, so as to create a film of said liquid which flows along the inner wall ( 2 J) of the tank; or

the second inlet duct ( 17 ) provides an opening ( 17 A) for discharging the liquid recirculating in said second duct ( 17 ) into the tank, wherein said opening ( 17 A), and in particular the guide element ( 17 B) thereof, is provided at a significant distance (D 14 ) from the tank maximum optimal filling level (M), which allows a film of the liquid fed into the tank to flow from the second duct ( 17 ) along a wide surface of the inner wall ( 2 J) of the tank exposed to the air and not covered by the ink, wherein the tank is sized in such a way as to provide a height (D 15 ) of the wall ( 2 J) of the tank not occupied by the ink and along which the liquid can flow which is between 20% and 60% of the overall height (D 16 ) of the tank and wherein said discharge opening ( 17 A) is positioned at a distance (D 14 ) from the tank optimal filling level (M) between 20% and 60% of the overall height (D 16 ) of the tank.

24 . The ink recirculating system according to claim 1 , characterized in that the tank ( 2 ) comprises a lid ( 14 ) adapted to close the top of the tank itself, in that said lid ( 14 ) comprises connecting means ( 14 A) for removably fixing it to the tank ( 2 );

and in that said lid ( 14 ) comprises first connecting means ( 20 A) ( 20 B) for connecting to the lid at least the duct ( 9 ) for ink outlet from the tank ( 2 ), and also at least the first duct ( 10 ) for the ink inlet in the tank ( 2 );

and in that said lid comprises one or more of the following features:

the lid comprises further connecting means ( 20 D) for also connecting a ventilation duct ( 18 ) to the lid; or

the lid comprises further connecting means ( 20 C) for connecting a second duct ( 17 ) for the inlet of the ink or the components thereof to the lid; or

the lid comprises further connecting means ( 20 E) for connecting at least one sensor ( 16 ) to the lid to detect the level ( 16 ) of the ink in the tank; or

at least one of said connecting means ( 20 A-E) is at least partially made in one piece or associated with the lid ( 14 ); or

at least one of said connecting means ( 20 A-D) for said ducts ( 9 ), ( 10 ), ( 17 ), ( 18 ) comprises:

a first connecting element ( 21 A-D) that faces the inside of the tank adapted to receive and sealingly connect one end of said ducts ( 9 ), ( 10 ), ( 17 ), ( 18 );

at least one intermediate tubular element ( 22 A-D) adapted to connect said first connecting element ( 21 A-D) and therefore also the respective ducts ( 9 ), ( 10 ), ( 17 ), ( 18 ), to second connecting elements ( 23 A-D) provided outside the lid and adapted to connect the tank to ducts ( 3 A), ( 6 A), ( 8 A) of the ink recirculating system, provided, respectively, for the ink outlet from the tank ( 2 ), for the ink and ( 7 A) and the components ( 7 B) thereof feeding into the tank and for feeding the recirculated ink into the tank; or

the connecting means ( 20 E) of at least one sensor ( 16 ) comprise at least one first element ( 21 E) which faces the inside of the tank, adapted to receive and sealingly connect one end of the level sensor ( 16 ), an intermediate element ( 22 E) for connecting the sensor ( 16 ) to at least one second connecting element ( 23 E) provided outside the lid.

25 . An inkjet printer comprising an ink recirculating system according to claim 1 .