You can freely build on How Canon's Bubble Jet Printers Make Ink Droplets

What this patent covers

This patent describes how bubble jet printers work. Imagine a tiny tube, called a liquid flow path, with ink inside. At one end is an opening, the orifice, where ink droplets come out. Near this opening, but not too close, is a heating element. When the printer needs to make a dot, it sends a signal to this heater. The heater instantly gets super hot, boiling the ink right next to it. This creates a bubble. The bubble expands and pushes the ink in front of it out of the orifice, forming a droplet. Once the bubble pops, the heater cools down, and more ink flows in to fill the path, ready for the next droplet. The key is heating the ink *really* fast and only in a small spot, so it's a violent bubble, not just gentle simmering.

What is now free to use

All 1 claims of US 4723129 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Printing methods that use continuous streams of ink droplets.

• Printing methods that rely on mechanical pressure or vibration to eject ink.

• Printing methods where the heating element heats the entire ink chamber uniformly.

• Printing methods that do not involve the formation and collapse of a vapor bubble in the ink.

• Inkjet printers that use piezoelectric crystals to eject ink.

Who is building on this today

Canon Inc. remains a primary developer and user of this technology. Other major printer manufacturers like HP and Epson also employ similar thermal inkjet principles, though they may have developed their own patented variations or improvements on the core concept.

Products built on expired version of this technology

How to cite this patent in your documentation

Canon Inc. US Patent 4723129. Bubble jet recording method and apparatus in which a heating element generates bubbles in a liquid flow path to project droplets. Granted 1988, expired 2006. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.