Cooling rate and thermal gradient control to reduce bubbles and voids in phase change ink
AssigneePalo Alto Research Center Incorporated
InventorJohn S. Paschkewitz
Life of this patent
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Abstract
The Niyama number of a flow path for phase change ink is the ratio of cooling rate of the ink to the thermal gradient of the ink along the ink flow path. Print head assemblies can be designed and configured to achieve ink flow paths having Niyama numbers that are greater than a critical Niyama value. These designs reduce entrapment of air in the ink as the ink is changing phase and provide optimal bubble and void mitigation for phase change ink. The thermal gradient of the ink flow path can be achieved using passive and/or active thermal elements disposed along the ink flow path.
Claims26
A print head assembly for an ink jet printer, comprising:
- one or more components fluidically coupled to define an ink flow path;
- and
- one or more thermal elements disposed along the ink flow path and configured to maintain a ratio of cooling rate to thermal gradient along the ink flow path to be above a critical Niyama value for the ink flow path.
A method of making a print head assembly, comprising:
- forming an ink flow path that is defined by one or more fluidically coupled components;
- and
- disposing one or more thermal elements along the ink flow path, the thermal elements configured to maintain a ratio of cooling rate to thermal gradient along the ink flow path to be above a critical Niyama value for the ink flow path.
A method of operating a print head assembly of an ink jet printer, comprising:
- heating phase change ink along an ink flow path;
- and
- controlling a thermal gradient of the ink during a time that the ink is changing phase using one or more thermal elements disposed, respectively, at one or more locations along an ink flow path;
- and
- maintaining a ratio of cooling rate to the thermal gradient along the ink flow path to be above a critical Niyama value for the ink flow path during the time that the ink is changing phase.
An ink jet printer, comprising:
- a print head assembly comprising a print head with ink jets configured to selectively eject ink toward a print medium according to predetermined pattern;
- a transport mechanism configured to provide relative movement between the print medium and the print head, wherein the print head assembly further includes:
- an ink flow path defined by one or more components of the print head assembly;
- and
- one or more thermal elements disposed along the ink flow path and configured to maintain a ratio of cooling rate to thermal gradient along the ink flow path to be above a critical Niyama value for the ink flow path.
Dependencies are inferred from the claim text.