Control method for detecting the operating status of the nozzles of an ink-jet printhead

1. A control method for detecting the operating status of the nozzles of an ink-jet printhead, comprising the following steps:

detecting an inlet pressure and an outlet pressure within a feeding channel ( 5 ) of the nozzles ( 6 ) in a closing condition of all nozzles ( 6 );

detecting a first reference pressure differential (D1) between the inlet pressure and the outlet pressure;

opening each nozzle ( 6 ) in sequence, separately from the others;

detecting the pressure differential (Di) between the inlet pressure and the outlet pressure in an opening condition of each single nozzle ( 6 );

comparing the pressure differential detected (Di) with the first reference pressure differential (D1).

2. A control method according to claim 1 , comprising the following steps:

identifying the nozzle ( 6 ) as properly working if the pressure differential detected (Di) differs from the first reference pressure differential (D1) beyond a preset value;

identifying the nozzle ( 6 ) as not properly working if the pressure differential detected (Di) does not differ from the first reference pressure differential (D1) beyond said preset value.

3. A control method for detecting the operating status of the nozzles of an ink-jet printhead, comprising the following steps:

detecting a reference pressure differential (D2) in an initial switching on condition of the printhead and of all open nozzles ( 6 );

on the basis of a position coefficient (Cpi) for each nozzle ( 6 ), an ideal pressure (Pw) of the printing fluid within the feeding channel ( 5 ) and the number of nozzles ( 6 ) arranged within the printhead,

calculating an ideal loss of pressure (Api) for each printhead nozzle ( 6 ) as:

Api

=

Pw

-

D

⁢

⁢

2

number

⁢

⁢

of

⁢

⁢

nozzles

×

Cpi

.

4. A control method according to claim 3 , comprising the following steps:

opening each nozzle ( 6 ) in sequence, separately from the others;

detecting the pressure differential (Di) between the inlet pressure and the outlet pressure in an opening condition of each single nozzle ( 6 );

comparing the pressure differential detected (Di) with the loss of ideal pressure (Api).

5. A control method according to claim 4 , comprising the following step:

signaling a nozzle as a malfunctioning nozzle, if the differential detected (Di) for a nozzle ( 6 ), differs from a loss of ideal pressure (Api) beyond a certain threshold.

6. A control method according to claim 3 , comprising a step of:

identifying a first set of nozzles pairs ( 6 ) adjacent one to another, which comprises all the present nozzles ( 6 );

identifying a second set of nozzles pairs ( 6 ) adjacent one to another not comprising two nozzles ( 6 ) located at end positions;

for each pair of the adjacent nozzles ( 6 ), calculating a loss of ideal pressure as:

Apc i,i+1 =Ap i +Ap i+1 .

7. A control method according to claim 6 , comprising the following steps:

opening each pair of adjacent nozzles ( 6 ) in sequence that belong to the first set of nozzles, separately from the other nozzles;

detecting the pressure differential (Di,i+1) between the inlet pressure and the outlet pressure in the opening condition of each pair of nozzles ( 6 );

for each pair of adjacent nozzles ( 6 ), comparing the pressure differential detected (Di,i+1) with the loss of ideal pressure (Apc i,i+1 ) in respect to that adjacent pair of nozzles.

8. A control method according to claim 7 , comprising the following steps:

signaling both nozzles as malfunctioning nozzles if the pressure differential detected (Di,i+1) in respect of a pair of adjacent nozzles is substantially equal to zero;

signaling both nozzles as functioning correctly if the pressure differential detected (Di, i+1) for a pair of adjacent nozzles is substantially equal to the loss of ideal pressure (Apc i,i+1 ) for that pair of adjacent nozzles;

signaling the pair of adjacent nozzles as operating under uncertain conditions, if the pressure differential detected (Di, i+1) in respect to a pair of adjacent nozzles, substantially differs from the loss of ideal pressure (Apc i,i+1 ) in respect to said pair of adjacent nozzles.

9. A control method according to claim 8 , comprising the following step:

opening the pairs of nozzles ( 6 ) adjacent to the second set of nozzles, separately from the other nozzles, in respect to which pairs of nozzles ( 6 ), one nozzle was signaled as operating under uncertain conditions;

detecting the pressure differential (Di, i+1) between the inlet pressure and the outlet pressure in the opening condition of each pair of open nozzles ( 6 );

for each pair of adjacent nozzles ( 6 ), comparing the pressure differential detected (Di,i+1) with the loss of ideal pressure (Apc i,i+1 ) in respect to that adjacent pair of nozzles.

10. A printhead for an ink-jet printer, comprising a feeding circuit, the feeding circuit comprising: a feeding channel ( 5 ), arranged to feed a printing fluid to a plurality of nozzles ( 6 ), which feeding channel ( 5 ) is provided with an inlet section ( 1 ) and an outlet section ( 2 ); characterized in that the feeding circuit comprises: a first pressure sensor ( 3 ), that is so arranged as to detect pressure in the inlet section ( 1 ) of the channel ( 5 ), or in an area next to the inlet section ( 1 ); a second pressure sensor ( 4 ), that is so arranged as to detect the pressure in the outlet section ( 2 ) of the channel ( 5 ), or in an area next to the outlet section ( 2 ); wherein the nozzles ( 6 ) directly communicate with the feeding channel ( 5 ) and wherein each nozzle ( 6 ) is provided with a respective shutter ( 7 ), which is at least partially inserted within the feeding channel ( 5 ); the printhead further comprising a control processor arranged to control operating of each shutter ( 7 ) and to detect the pressure signals of the first and second pressure sensors ( 3 , 4 ); wherein the control processor is configured to perform a control method for detecting the operating status of the nozzles of the printhead, the control method comprising the following steps:

detecting an inlet pressure and an outlet pressure within the feeding channel ( 5 ) of the nozzles ( 6 ) in a closing condition of all nozzles ( 6 );

detecting a first reference pressure differential (D1) between the inlet pressure and the outlet pressure;

opening each nozzle ( 6 ) in sequence separately from the others;

detecting the pressure differential (Di) between the inlet pressure and the outlet pressure in an opening condition of each single nozzle ( 6 );

comparing the pressure differential detected (Di) with the first reference pressure differential (D1).