Claims
- 1. A method of operating multichannel pulsed droplet deposition apparatus having droplet liquid channels each with a nozzle having a pressure wave reflection coefficient r where r is negative, each channel having a negative pressure wave reflection coefficient at a termination connected to means for supplying droplet liquid, the method comprising the step of ejecting a droplet from a selected channel by generating therein defined pressure changes comprising a negative pressure pulse of duration L/c followed by a positive pressure pulse of duration at least L/c and substantially canceling residual pressure waves in said channel by generating further pressure changes opposed to said defined pressure changes after a delay of 2L/c where L is the length of the channel and c is the effective velocity of pressure waves in the channel.
- 2. A method according to claim 1, comprising the step of relating the amplitude of said further pressure changes to the amplitude of said defined pressure changes by the factor r.
- 3. A method according to claim 1, comprising the step of generating a positive pressure pulse of duration 2L/c.
- 4. A method according to claim 3, comprising the step of generating a first further pressure pulse with a delay of 2L/c after the negative pressure pulse and generating a second further pressure pulse with a delay of 2L/c after the positive pressure pulse.
- 5. A method according to claim 1, wherein said droplet liquid channels of said multichannel pulsed droplet deposition apparatus are bounded by displaceable wall actuators, said apparatus having selected channels and non-selected channels arranged in respective groups of channels which are actuated sequentially with each said selected channel being bounded by a displaceable wall actuator, said actuator also bounding said adjacent non-selected channel, and wherein displacement of said wall actuator generates said defined and further pressure changes, the displacement of the actuator also generating complementary defined pressure changes in the adjacent non-selected channel and complementary further pressure changes in said adjacent non-selected channel which cancels further residual pressure waves in said adjacent channel arising from said complementary defined pressure pulse.
- 6. A method according to claim 5, comprising the step of dividing the channels into at least two groups, the groups being sequentially enabled for actuation, adjacent channels being in different groups.
- 7. A method according to claim 1 wherein said droplet deposition apparatus has droplet liquid channels separated by wall actuators displaceable on the application to the wall actuators of a voltage difference, each said channel having at least one electrode associated with wall actuators bounding that channel such that a voltage difference can be applied to a specified wall actuator by the application of different voltages to respective electrodes of the two channels separated by the said wall actuator, the method comprising the step of actuating a selected channel through the steps of applying in different time periods a first actuating voltage to an electrode of the selected channel and a second actuating voltage of the same polarity to an electrode of non-selected channels, thereby causing expansion and contraction of the droplet liquid volume of the selected channel to generate said defined pressure changes.
- 8. A method according to claim 7, wherein there is applied to one or more electrodes a correcting voltage comprising a first correcting voltage delayed by 2L/c with respect to said first actuating voltage applied to the electrodes of non-selected channels and a second correcting voltage delayed by 2L/c with respect to said second actuating voltage applied to an electrode of the selected channel, where L is the length of the channel and c is the effective velocity of pressure waves of the channel.
- 9. A method according to claim 8, comprising the step of relating the magnitude of said first correcting voltage to the magnitude of said first actuating voltage by a factor less than 1 and relating the magnitude of said second correcting voltage to the magnitude of said second actuating voltage by a factor less than 1.
- 10. A method according to claim 9, comprising the steps of relating the magnitude of said first correcting voltage to the magnitude of said first actuating voltage and relating the magnitude of said second correcting voltage to the magnitude of said second correcting voltage by equal factors less than 1.
- 11. A method according to claim 7, the method comprising the steps of applying a first voltage of relative magnitude 1 to an electrode of the selected channel in a first time period L/c, a second voltage of relative magnitude 1 to the electrodes of non-selected channels in a second time period L/c, a third voltage of relative magnitude between 0 and 1+r to the electrodes of non-selected channels in a third time period L/c, and a fourth voltage of relative magnitude between 0 and 1+r to the electrodes of either the selected channels or non-selected channels in a fourth time period L/c, where the fourth voltage is not zero if the third voltage is zero.
- 12. A method according to claim 11, wherein the relative magnitude of the third voltage is equal to r and wherein the fourth voltage is of relative magnitude r and the method comprises the step of applying said fourth voltage to an electrode of the selected channel.
- 13. A driving circuit for a multichannel pulsed droplet apparatus, said apparatus having droplet liquid channels of length L, having an effective velocity c of pressure waves in the channels, with a droplet ejection nozzle having a pressure wave reflection coefficient r, the driving circuit comprising means for actuating the apparatus according to claim 1.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9405137 |
Mar 1994 |
GBX |
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CROSS REFERENCE TO RELATED APPLICATION
This is a continuation of International Application No. PCT/GB95/00562 filed Mar. 16, 1995, the disclosure of which is incorporated herein by reference.
US Referenced Citations (12)
Foreign Referenced Citations (6)
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0 375 147 |
Jun 1990 |
EPX |
376532 |
Jul 1990 |
EPX |
59-104950 |
Jun 1984 |
JPX |
59-176060 |
Oct 1984 |
JPX |
2-506 |
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3-147022 |
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JPX |
Continuations (1)
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Number |
Date |
Country |
Parent |
PCTGB9500562 |
Mar 1995 |
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