Patent ID: 6113221
Filing Date: 2000-09-05
Classification: B41J

Abstract:
A printhead for ejecting fluid droplets comprising:a chamber member defining a chamber having a chamber volume, the chamber member defining an orifice and a fluid inlet through which fluid flows to the chamber;a heating member located within the chamber for heating fluid within the chamber for ejecting a single fluid droplet having a volume substantially equal to the chamber volume in response to activation of the heating member; anda separate fluid channel which communicates with the chamber by means of the fluid inlet;wherein the heating of the fluid within the chamber by the heating member forms a vapor bubble with a bubble front that extends outwardly in a radial direction from the heating member, the fluid inlet providing a blowback resistance between the separate fluid channel and the chamber so that the expanding bubble front serves to displace substantially all fluid within the chamber through the orifice to form the fluid droplet; andwherein the vapor bubble front expands through a plane of the orifice until the vapor bubble vents causing discharge of substantially all vapor within the vapor bubble out of the chamber through the orifice to an atmosphere surrounding the printhead causing ejection of the fluid displaced from the chamber through the orifice as the fluid droplet, to prevent cooling of the vapor bubble and subsequent collapse of the vapor bubble within the chamber and onto the heating member.