US 4,734,706 AGranted

Film-protected print head for an ink jet printer or the like

AssigneeTektronix, Inc.

InventorsHue P. Le, James C. Oswald

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Abstract

A viscoelastic and ink-immiscible fluid is used to form a membrane over the ink orifice of a drop-on-demand, pressure pulse ink jet head. The membrane lies in a plane perpendicular to the direction of emission of ink drops, and provides a barrier between the ink orifice and the external atmosphere. Evaporation of the ink, or entry of contaminants including air into the ink, is thus inhibited. The elimination of evaporative clogging then permits the use of a smaller orifice. Wetting of the exterior surface of the ink jet head by the flow of ink through the ink orifice is also inhibited, thus making possible the production of more uniform ink drops that will emerge in a constant direction. The elastic property of the membrane permits the passage of an ink drop therethrough, followed by the closing up of the membrane. The viscous property of the membrane permits it to absorb any energy of a pressure pulse that is not consumed in ejecting an ink drop, thus inhibiting the occurrence of pressure oscillations that could cause either variations in the speed of ejected ink drops or the appearance of satellite ink droplets.

Claims21

Dependent claims

A print head comprising

a print head body defining a horn-shaped fluid chamber having a wide end and an opposite narrow end,
an orifice plate attached to the print head body at the narrow end of said fluid chamber, forming a containing wall thereto and defining an orifice in communication with said fluid chamber and opening in the direction of the external atmosphere,
a fluid supply tube connected to said fluid chamber,
a fluid reservoir connected to said fluid supply tube and adapted to provide a continuous supply of fluid through said fluid supply tube to said fluid chamber,
a pressure diaphragm attached to the print head body at the wide end of said fluid chamber and forming a containing wall thereto,
a piezoelectric element attached to said pressure diaphragm on the opposite side thereof to said fluid chamber, said piezoelectric element being adapted to apply a mechanical pressure to the fluid contained within said fluid chamber for causing ejection of fluid through said orifice, upon application of a voltage to said piezoelectric element,
a liquid membrane lying perpendicular to the axis of said orifice and separating said orifice from the external atmosphere,
a membrane plate adapted for the containment of said membrane in a plane parallel to and adjacent to said orifice plate,
a liquid supply tube connected to said membrane plate at a location adapted to provide liquid for the formation of said membrane, and
a liquid reservoir connected to said liquid supply tube and adapted to provide a continuous supply of liquid through said liquid supply tube to said membrane plate for the formation of said liquid membrane, said liquid being a polysilicone material having the general formula ##STR2## wherein n is an integer having a value in the range of about 200 to 800.

7 more elements

Dependencies are inferred from the claim text.