| 摘要 |
PCT No. PCT/US96/04963 Sec. 371 Date Dec. 4, 1996 Sec. 102(e) Date Dec. 4, 1996 PCT Filed Apr. 9, 1996 PCT Pub. No. WO96/32286 PCT Pub. Date Oct. 17, 1996A method of clearing nozzles of thermally activated drop on demand printing head which have been blocked by dried ink by applying a consecutive sequence of heater energizing pulses. The method is particularly applicable to coincident forces drop on demand printing systems. A series of consecutive pulses is applied to the heater. These pulses accumulate heat at the nozzle tip, and the ink in contact with the tip, above the boiling point of the ink. The formation of vapor bubbles at the tip can dislodge a crust of dried ink, which is then expelled with the ink drop. A single power pulse of longer than normal duration, or greater than normal energy, can be used. However, this may require substantial additional electronic circuitry to generate. The need for this circuitry is eliminated by applying an integral number (greater than one) of consecutive power pulses of the energy, duration, and time varying power profile that is used to expel drops on demand under normal operating conditions. A nozzle clearing sequence can be automatically applied to all nozzles before printing each page.
|
