Methods and apparatus for droplet deposition

1 . A method for depositing droplets of fluid onto a medium utilising a droplet deposition head, the droplet deposition head comprising:

an array of fluid chambers separated by interspersed walls formed of a piezoelectric material, each fluid chamber communicating with an aperture for the release of droplets of fluid, each of said walls separating two neighbouring fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber, and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction;

wherein each of said walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively settable to one of (a) a drive potential that is different from the common potential, and (b) the common potential;

wherein each of said walls is actuable such that, in response to the application of the drive potential to the respective first electrode, the respective wall will move in the first direction from a neutral position into a deformed position, and in response to the application of the common potential to the respective first electrode, the respective wall will return to, or remains in, the neutral position;

the method comprising, for an actuation cycle, the steps of:

receiving input data;

assigning, based on said input data, all the fluid chambers within said array as either firing chambers or non-firing chambers so as to produce bands of one or more contiguous firing chambers separated by bands of one or more contiguous non-firing chambers; and

applying the common potential to the second electrodes and, based on said input data, selectively applying either the drive potential or the common potential to the first electrodes to actuate the walls of said chambers such that:

for each non-firing chamber,

if the non-firing chamber is adjacent to a band of firing chambers, one wall is actuated in the first direction while the other wall remains in the neutral position,

if the non-firing chamber is a single non-firing chamber between bands of firing chambers, both walls are actuated concurrently in the first direction, and

if the non-firing chamber is not adjacent to a band of firing chambers, both walls either remain in the neutral position, or are actuated concurrently in the first direction, or are actuated concurrently in the second direction; and

for each firing chamber,

each of the first and second walls are actuated consecutively in the first direction;

said actuations during the actuation cycle resulting in each said firing chamber of the band of one or more contiguous firing chambers releasing at least one droplet, the resulting droplets forming bodies of fluid disposed on a line on said medium, said bodies of fluid being separated on said line by respective gaps for each of said bands of non-firing chambers, the size of each such gap generally corresponding in size to the respective band of non-firing chambers.

2 . The method according to claim 1 , wherein, for a first firing chamber, the method comprises, in the actuation cycle:

actuating the first wall of the first firing chamber in the first direction while the second wall of the first firing chamber remains in the neutral position, thereby increasing the volume of the first firing chamber and causing it to draw in a quantity of fluid, and then returning the first wall of the first firing chamber to the neutral position; and then

actuating the second wall of the first firing chamber in the first direction while the first wall of the first firing chamber remains in the neutral position, thereby decreasing the volume of the first firing chamber and causing the first firing chamber to eject a droplet of the fluid therein, and then returning the second wall of the first firing chamber to the neutral position.

3 . The method according to claim 2 , wherein a second firing chamber is adjacent to the first firing chamber, the second firing chamber being in the second direction relative to the first firing chamber such that the second wall of the first firing chamber is the first wall of the second firing chamber,

wherein, in the actuation cycle, the said actuating of the second wall of the first firing chamber in the first direction is performed while the second wall of the second firing chamber remains in the neutral position, thereby increasing the volume of the second firing chamber and causing the second firing chamber to draw in a quantity of fluid concurrently with the ejection of the droplet from the first firing chamber.

4 . The method according to claim 3 , wherein, in the actuation cycle, the said returning of the second wall of the first firing chamber to the neutral position causes the ejection of a droplet of the fluid from within the second firing chamber;

or wherein the method further comprises, in the actuation cycle, actuating the second wall of the second firing chamber in the first direction while the first wall of the second firing chamber remains in the neutral position, thereby decreasing the volume of the second firing chamber to cause the second firing chamber to eject a droplet of the fluid therein, and then returning the second wall of the second firing chamber to the neutral position.

5 . The method according to claim 1 , wherein, for a first band of firing chambers and a second band of firing chambers separated by a single non-firing chamber, the non-firing chamber being in the second direction relative to the first band of firing chambers, and the second band of firing chambers being in the second direction relative to the non-firing chamber, such that,

of the first band of firing chambers, the second wall of a first firing chamber that is adjacent the non-firing chamber is the first wall of the non-firing chamber, and

of the second band of firing chambers, the first wall of a second firing chamber that is adjacent the non-firing chamber is the second wall of the non-firing chamber,

the method comprises, in the actuation cycle:

actuating the first wall of the first firing chamber in the first direction while the second wall of the first firing chamber remains in the neutral position, and then returning the first wall of the first firing chamber to the neutral position; and then

actuating the second wall of the first firing chamber and the first wall of the second firing chamber concurrently in the first direction while the second wall of the second firing chamber remains in the neutral position, thereby causing the first firing chamber to eject a droplet of the fluid therein, and then returning the second wall of the first firing chamber and the first wall of the second firing chamber to the neutral position; and then

actuating the second wall of the second firing chamber in the first direction while the first wall of the second firing chamber remains in the neutral position, thereby causing the second firing chamber to eject a droplet of the fluid therein, and then returning the second wall of the second firing chamber to the neutral position.

6 . The method according to any preceding claim 1 , wherein the common potential is ground potential or OV, or wherein the common potential is a positive potential greater than ground potential; and/or

wherein the drive potential is greater than the common potential.

7 . A method for depositing droplets of fluid onto a medium utilising a droplet deposition head, the droplet deposition head comprising:

an array of fluid chambers separated by interspersed walls formed of a piezoelectric material, each fluid chamber communicating with an aperture for the release of droplets of fluid, each of said walls separating two neighbouring fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber, and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction;

wherein each of said walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively settable to one of (a) a drive potential that is different from the common potential, and (b) the common potential;

wherein each of said walls is actuable such that, in response to the application of the drive potential to the respective first electrode, the respective wall will move in the first direction from a neutral position into a deformed position, and in response to the application of the common potential to the respective first electrode, the respective wall will return to, or remains in, the neutral position;

the method comprising, for an actuation cycle, the steps of:

receiving input data;

assigning, based on said input data, all the fluid chambers within said array as either firing chambers or non-firing chambers so as to produce bands of one or more contiguous firing chambers separated by bands of one or more contiguous non-firing chambers; and

applying the common potential to the second electrodes and, based on said input data, selectively applying either the drive potential or the common potential to the first electrodes to actuate the walls of said chambers such that:

for at least a first firing chamber,

the first wall of the first firing chamber is repeatedly actuated in the first direction and then returned to the neutral position while the second wall of the first firing chamber is kept in the neutral position; and

at a time in the actuation cycle at which the first firing chamber is to eject a droplet of the fluid therein, the second wall of the first firing chamber is selectively actuated in the first direction substantially concurrently with the returning of the first wall of the first firing chamber to the neutral position, thereby causing the first firing chamber to eject a droplet of the fluid therein, and then the second wall of the first firing chamber is returned to the neutral position;

said actuations during the actuation cycle resulting in each said firing chamber of the band of one or more contiguous firing chambers releasing at least one droplet, the resulting droplets forming bodies of fluid disposed on a line on said medium, said bodies of fluid being separated on said line by respective gaps for each of said bands of non-firing chambers, the size of each such gap generally corresponding in size to the respective band of non-firing chambers.

8 . The method according to claim 7 , wherein the first firing chamber is a member of a first group of firing chambers that are interleaved by respective firing chambers of a second group of one or more firing chambers, and wherein the first wall of each of the members of the first group of firing chambers are simultaneously repeatedly actuated in the first direction and then returned to the neutral position.

9 . The method according to claim 7 ,

wherein a second firing chamber that is a member of the second group of firing chambers is adjacent the first firing chamber, the second firing chamber being in the second direction relative to the first firing chamber such that the second wall of the first firing chamber is the first wall of the second firing chamber,

and wherein the method further comprises, in the actuation cycle:

keeping the second wall of the second firing chamber in the neutral position while the second wall of the first firing chamber is actuated to eject said droplet of the fluid therein; and then

actuating the second wall of the second firing chamber in the first direction substantially concurrently with the first wall of the second firing chamber being in the neutral position, thereby causing the second firing chamber to eject a droplet of the fluid therein, and then returning the second wall of the second firing chamber to the neutral position;

optionally wherein the second wall of the second firing chamber is repeatedly actuated in the first direction and returned to the neutral position in synchronicity with the repeated actuation of the first wall of the first firing chamber.

10 . The method according to claim 7 , wherein, in the actuation cycle, for each non-firing chamber,

if the non-firing chamber is a single non-firing chamber between bands of firing chambers, both walls are actuated concurrently in the first direction, otherwise

one wall is actuated in the first direction while the other wall remains in the neutral position, or both walls remain in the neutral position.

11 . The method according to claim 7 , wherein the repeatedly-actuated wall(s) are actuated one or more times before the step of assigning, based on said input data, all the fluid chambers within said array as either firing chambers or non-firing chambers;

or wherein the first wall of the or each firing chamber is actuated at substantially the resonant frequency of the firing chambers, or at substantially a harmonic or subharmonic of the resonant frequency of the firing chambers.

12 . The method according to claim 7 , wherein the common potential is ground potential or OV, or wherein the common potential is a positive potential greater than ground potential; and/or

wherein the drive potential is greater than the common potential.

13 . A method for depositing droplets of fluid onto a medium utilising a droplet deposition head, the droplet deposition head comprising:

an array of fluid chambers separated by interspersed walls formed of a piezoelectric material, each fluid chamber communicating with an aperture for the release of droplets of fluid, each of said walls separating two neighbouring fluid chambers, and each fluid chamber being defined by a first wall in a first direction relative to the fluid chamber, and a second wall in a second direction relative to the fluid chamber, the second direction being opposite to the first direction;

wherein each of said walls has a first electrode on a first side of the wall and a second electrode on a second side of the wall, wherein the second electrode of each of the walls is connected to a common potential, and wherein the first electrode of each of the walls is selectively settable to one of (a) a first drive potential, (b) a second drive potential, and (c) the common potential, the common potential being between the first drive potential and the second drive potential;

wherein each of said walls is actuable such that, in response to the application of the first drive potential to the respective first electrode, the respective wall will move in the first direction from a neutral position into a deformed position, in response to the application of the second drive potential to the respective first electrode, the respective wall will move in the second direction from the neutral position into a deformed position, and in response to the application of the common potential to the respective first electrode, the respective wall will return to, or will remain in, the neutral position;

the method comprising, for an actuation cycle, the steps of:

receiving input data;

assigning, based on said input data, all the fluid chambers within said array as either firing chambers or non-firing chambers so as to produce bands of one or more contiguous firing chambers separated by bands of one or more contiguous non-firing chambers; and

applying the common potential to the second electrodes and, based on said input data, selectively applying either the first drive potential, the second drive potential or the common potential to the first electrodes to actuate the walls of said chambers such that:

for at least a first firing chamber,

the first wall of the first firing chamber is repeatedly actuated in the first direction and then the second direction while the second wall of the first firing chamber is kept in the neutral position; and

at a time in the actuation cycle at which the first firing chamber is to eject a droplet of the fluid therein, the second wall of the first firing chamber is selectively actuated in the first direction substantially concurrently with the actuating of the first wall of the firing chamber in the second direction, thereby causing the first firing chamber to eject a droplet of the fluid therein, and then the second wall of the first firing chamber is returned to the neutral position;

said actuations during the actuation cycle resulting in each said firing chamber of the band of one or more contiguous firing chambers releasing at least one droplet, the resulting droplets forming bodies of fluid disposed on a line on said medium, said bodies of fluid being separated on said line by respective gaps for each of said bands of non-firing chambers, the size of each such gap generally corresponding in size to the respective band of non-firing chambers.

14 . The method according to claim 13 , wherein the first firing chamber is a member of a first group of firing chambers that are interleaved by respective firing chambers of a second group of one or more firing chambers, and wherein the first wall of each of the members of the first group of firing chambers are simultaneously repeatedly actuated in the first direction and then the second direction.

15 . The method according to claim 13 , wherein, in the actuation cycle, for each non-firing chamber, the walls are actuated such that:

if the band of non-firing chambers is not a single non-firing chamber in between bands of firing chambers, one wall is actuated either in the first direction only or in both the first and second directions while the other wall remains in the neutral position; or

both walls remain in the neutral position;

or wherein, in the actuation cycle, for each non-firing chamber, the walls are actuated such that:

if a single non-firing chamber is between bands of firing chambers:

one wall is actuated in the first direction while the second wall remains in the neutral position; and then

one wall is actuated in the first direction while the other wall is actuated in the second direction.

16 . The method according to claim 15 , wherein, for a band of a plurality of contiguous firing chambers, the firing chambers are actuated to deposit droplets as a plurality of consecutive lines.

17 . The method according to claim 13 , wherein the second wall of the first firing chamber is actuated in the second direction concurrently with an actuation of the first wall of the first firing chamber in the first direction, immediately prior to the time in the actuation cycle at which the first firing chamber is to eject a droplet of the fluid therein;

or wherein the second wall of the first firing chamber is actuated in the second direction concurrently with an actuation of the first wall of the first firing chamber in the second direction, prior to the time in the actuation cycle at which the first firing chamber is to eject a droplet of the fluid therein.

18 . The method according to claim 17 , wherein said actuation of the second wall of the first firing chamber in the second direction is performed by applying a second drive potential to the first electrode of the second wall of the first firing chamber, the second drive potential being such that the difference between the second drive potential and the common potential is less than the difference between the common potential and the first drive potential.

19 . The method according to claim 13 , wherein the common potential is a positive potential greater than ground potential;

optionally wherein the first drive potential is greater than the common potential and the second drive potential is less than the common potential;

optionally wherein the second drive potential is ground potential or OV.

20 . The method according to claim 13 , wherein the repeatedly-actuated wall(s) are actuated one or more times before the step of assigning, based on said input data, all the fluid chambers within said array as either firing chambers or non-firing chambers;

or wherein the first wall of the or each firing chamber is actuated at substantially the resonant frequency of the firing chambers, or at substantially a harmonic or subharmonic of the resonant frequency of the firing chambers.