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AIR COOLING FOR THERMAL INK JET PRINTHEAD

IP.com Disclosure Number: IPCOM000027511D
Original Publication Date: 1997-Jun-30
Included in the Prior Art Database: 2004-Apr-08
Document File: 4 page(s) / 137K

Publishing Venue

Xerox Disclosure Journal

Abstract

Air is proposed as an insulating and cooling blanket for the printheads in a thermal ink jet printer. Thermal ink jet printheads are maintained at an operating temperature of 32 k 2°C to control drop size and velocity. If the environmental temperature surrounding the printhead is maintained at 125°C (as with drum dryer configurations), then the printheads must be insulated. By taking advantage of an existing air exchange, a curtain of air provides a thermal barrier between the printheads and the oven. The air exchange already prevents moisture build up from the ink and paper passing through the oven.

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XEROX DISCLOSURE JOURNAL

AIR COOLING FOR THERMAL INK JET PRINTHEAD U. S. C1. 347/026 Robert S. Karz

Proposed Classification

Int. C1. B41j 02/165

30.. ..

.

...

28 -

FIG. 7

XEROX DISCLOSURE JOURNAL - Vol. 22, No. 3 May/June 1997 145

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AIR COOLING FOR THERMAL INK JET PRINTHEAD (CONT'D)

Air is proposed as an insulating and cooling blanket for the printheads in a thermal ink jet printer. Thermal ink jet printheads are maintained at an operating temperature of 32 k 2°C to control drop size and velocity. If the environmental temperature surrounding the printhead is maintained at 125°C (as with drum dryer configurations), then the printheads must be insulated. By taking advantage of an existing air exchange, a curtain of air
provides a thermal barrier between the printheads and the oven. The air exchange already prevents moisture build up from the ink and paper passing through the oven.

Referring to Figure 1, a cowling 10 having a layer of insulation 13 between an inner wall 12 and outer wall 14 encloses a printhead assembly 20. The printhead assembly 20 comprises a printed circuit board 28, heat sink 22, print die 24, and an ink manifold 26. A laminar stream of outside air 30 flows over the printhead assembly 20. If turbulence is avoided, air flow 30 is an excellent insulator having a thermal conductivity of

146 XEROX DISCLOSURE JOURNAL - Vol. 22, No. 3 May/June 1997

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AIR COOLING FOR THERMAL INK JET PRINTHEAD (CONT'D)

approximately 0.3 milliwatts/cm"K. It can be shown that an air flow 30 of about 0.4 cubic feet per minute would be adequate to keep the temperature rise at the surface of printhead assembly 20 below about 10°C. A lumped parameter model of the thermal path is discussed hereinafter with reference to Figure 2.

The method of cooling thermal ink jet printheads shown in Figure 1 is inexpensive because it uses an existing exhaust blower for air flow. Accordingly, the method also avoids liquid handling complications inherent in circulating fluid systems.

Figure 2 schematically illustrates the lumped parameter mo...