HP 51626A, 51640, 51645A, 51641A, 51638A manual Introduction, Background on Thermal Inkjet Technology

1. INTRODUCTION

This document acts as a guide for the maintenance and care of Hewlett-Packard disposable print cartidge products including the HP51626A, HP51638A, HP51633M, HPC6117A, HP51640(A,C,M,Y), HP51641A, HPC6105A, HPC1823A, HPC6116A, HP51645A, HPC6168A, HPC6169A, HPC6170A, and HPC6104A. Each pen consists of a printhead and a pressurized ink source.

1.1 Background on Thermal Inkjet Technology

The disposable Hewlett-Packard cartridges are used in drop-on-demand thermal inkjet systems. Inkjet systems fire small drops of ink to form text and images on various types of medium.

Thermal inkjet uses a firing resistor to vaporize a small amount of ink. The vaporization process causes a small bubble to form. This bubble formation causes a small drop of ink to be forced out of the firing chamber through the nozzle. Figure 1 shows the major components of the thermal inkjet system. In the figure, the entire ink supply is located near the printhead of the print cartridge. This is the case for all of the Hewlett Packard disposable print cartridges. Back pressure is controlled in the local ink supply by a spring or foam which prevents the ink from seeping out of the nozzles. The filter screen keeps any large particles or air bubbles away from the firing chambers. Bubbles or particles in the firing chambers will prevent ink from coming out of the nozzle when the resistor heats up. There is a firing resistor for every nozzle on the printhead.

Ink Supply (Local or Bulk)

Filter Screen	Standpipe
Firing
Resistor
Substrate	Section
Ink Barrier
	of a
Orifice	Printhead
Surface	Nozzle

Figure 1: Anatomy of a Printhead

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