Thermal ink jet print device having phase change cooling

• US 5,272,491 A
• Filed: 04/03/1992
• Issued: 12/21/1993
• Est. Priority Date: 10/31/1990
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Stoffel, John L., Mohr, John A., Asakawa, Stuart D., Firl, Gerold G., Mueller, Bruce E., Kappele, William D.
• Primary Examiner(s): Hartary, Joseph W.
• Application Number:
  US07/863,521
• Time in Patent Office: 627 Days
• Field of Search: 346/140 R, 400/719, 400/124 TC, 361/386, 361/382, 165/104.33
• US Class Current: 347/18
• CPC Class Codes: B41J 2/05 produced by the application of heat
• CPC Class Codes: B41J 2/1408 Structure dealing with thermal variations, e.g. cooling device, thermal coefficients of materials
• CPC Class Codes: B41J 29/377 Cooling or ventilating arrangements

Abstract

A thermal ink jet print device having a phase change material, a solid or fluid, disposed in heat exchange proximity to the thermal ink jet printhead to absorb printhead heat energy by changing physical state at a printhead temperature below that at which unacceptable printing takes place and at a rate commensurate with the rate of heat energy input.

Claims

1. A thermal ink jet print device, comprising:

a body having a first cavity containing ink and having a second cavity containing a phase change material;

a rectangular printhead having a plurality of nozzles through which ink is ejected, said printhead having a rectangular back face disposed on said body adjacent said first cavity and said second cavity, said rectangular back face having a length dimension larger than a width dimension, said rectangular printhead having a length-wise slot formed through said back face and substantially centered with respect to said width dimension of said back face so as to divide said back face into a first half and a second half, said slot being in fluid communication with said first cavity via an ink passage for allowing ink to flow into priming cavities, each priming cavity being associated with one of said nozzles;

electrical heating means at each priming cavity for each nozzle of the plurality of nozzles, each electrical heating means when heated ejecting ink from the priming cavity through the nozzle thereat;

said second cavity comprising a first half portion and a second half portion, said first half portion having a first wall only contacting said first half of said back face of said printhead, said second half portion having a second wall only contacting said second half of said back face of said printhead,

said ink passage, in fluid communication with said slot, running between said first half portion and said second half portion of said second cavity,

said phase change material in said second cavity having two physical states with change from one physical state to the other physical state in the presence of printhead heat energy at a predetermined printhead temperature below that at which unacceptable printing occurs,

said phase change material in said second cavity being in heat exchange relationship with said back face of said printhead to be exposed to and to absorb printhead heat energy in changing physical state, said phase change material existing in both physical, states during phase change cooling and having a rate of change of physical state at said predetermined temperature which is substantially commensurate with the rate of delivery of heat energy by said printhead.

2. The invention according to claim 1 in which:

said phase change material is a solid which has a melting point below printhead temperatures at which printing degrades.

3. The invention according to claim 1 in which said phase change material is a solid which has a melting point in the range of about 35°

to 85°

C. and has a thermal conductivity of about ten (10) watts per meter per degree Kelvin.

4. The invention according to claim 1 in which said phase change material is gallium.

5. The invention according to claim 1 in which said phase change material is polyethylene glycol.

6. The invention according to claim 1 in which said phase change material is low temperature solder.

7. The invention according to claim 1 in which said body is plastic.

8. The invention according to claim 1 in which said body is metal.

9. The invention according to clam 1, in which:

said second cavity comprises at least one heat pipe structure in a substantially upright position in said body, having a bottom hot junction disposed in heat exchange relationship with said back face of said printhead and an upper cold junction for rejecting heat energy from said body, and

said phase change material is a fluid within said heat pipe structure pooled at said hot junction in heat exchange relationship with said back face of said printhead, which vaporizes at a temperature below that at which print degradation occurs and which vaporizes at a rate substantially commensurate with the rate of delivery of heat energy from said printhead, whereby vapor rises in said heat pipe structure, condenses in contact with said cold junction and flows down a wall of said heat pipe structure to said hot junction.

10. The invention according to claim 9, in which:

said back face of said printhead is connected directly to said heat pipe structure at said hot junction, and

said fluid is in contact with said back face of said printhead.

11. The invention according to claim 10, in which:

said fluid is freon.

12. The invention according to claim 10, in which:

said fluid is methanol.

13. The invention according to claim 10, in which:

said fluid is ethanol.

14. The invention according to claim 10, in which:

said fluid is I.P. alcohol.

15. The invention according to claim 10, in which:

said fluid is pentane.