# How Canon's Bubble Jet Printers Make Ink Droplets > Canon's 1988 patent on bubble jet printing uses a tiny heater to instantly vaporize ink, creating a bubble that pushes out a droplet of ink from the printer head. - **Patent:** US 4723129 - **Original title:** Bubble jet recording method and apparatus in which a heating element generates bubbles in a liquid flow path to project droplets - **Owner:** Canon Inc - **Granted:** 1988 - **Status:** Public domain (expired) - **Times cited:** 1,806 - **Field:** consumer_electronics, semiconductors, mechanical ## What it does 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 it does NOT cover - 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. ## The clever bit The innovation lies in the precise control of heat. Instead of just warming the ink, the patent claims a method to heat it so rapidly and locally that it causes a 'change of state' – essentially, a tiny, explosive bubble. This bubble generation is far more efficient for ejecting droplets than slower heating methods. ## Real-world examples 1. Canon Bubble Jet printers (e.g., BJ series) 2. HP thermal inkjet printers 3. Epson thermal inkjet printers 4. Most consumer-grade inkjet printers ## Why it matters This patent is foundational for bubble jet (also known as thermal inkjet) printing technology. It enabled Canon to develop its highly successful line of inkjet printers, which brought affordable color printing to homes and offices worldwide. This technology is still a dominant force in the consumer inkjet printer market. ## Frequently asked questions ### What does How Canon's Bubble Jet Printers Make Ink Droplets cover? Canon's 1988 patent on bubble jet printing uses a tiny heater to instantly vaporize ink, creating a bubble that pushes out a droplet of ink from the printer head. ### Who owns patent US 4723129? Canon Inc owns this patent, granted in 1988. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 4723129 cited by? This patent has been cited by 1806 later patents that build on its ideas. ### What problem does this patent solve? This patent is foundational for bubble jet (also known as thermal inkjet) printing technology. It enabled Canon to develop its highly successful line of inkjet printers, which brought affordable color printing to homes and offices worldwide. This technology is still a dominant force in the consumer inkjet printer market. ### What does this patent NOT cover? Printing methods that use continuous streams of ink droplets. **Full plain-English explainer:** https://patentbrief.org/patent/us/4723129/inkjet-bubble-jet-printing **Original patent:** https://patents.google.com/patent/US4723129 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Thermal Inkjet Printers Use Two-Step Heating to Shoot Ink](https://patentbrief.org/patent/us/4490728/thermal-inkjet-printing) — Hewlett-Packard's 1982 patent on a two-stage electrical pulse method that preheats ink before vaporizing it, allowing thermal inkjet printers to reliably eject precise droplets without clogging. - [How Piezoelectric Inkjet Printing Works](https://patentbrief.org/patent/us/3946398/drop-on-demand-inkjet) — A 1970 patent describing how to print images by using electrical pulses to bend a tiny crystal plate, squeezing individual ink drops out of a nozzle on demand. - [How 3D Printers Build Objects Layer by Layer from Liquid](https://patentbrief.org/patent/us/4575330/stereolithography-3d-printing) — This patent describes the foundational method for 3D printing, where a machine builds a three-dimensional object layer by layer by hardening a liquid material with light or other energy. - [How Laser Printers Use Rotating Mirrors to Write Information](https://patentbrief.org/patent/us/3867571/laser-printer-starkweather) — A 1972 Xerox patent describing how to use a spinning mirror to scan a laser beam across a page, adjusting the speed of the data to keep the image sharp. - [How Polaroid's Instant Film Pods Work](https://patentbrief.org/patent/us/2543181/polaroid-instant-camera) — A 1951 invention by Edwin Land that enabled instant photography by packaging liquid developer inside a breakable pod attached to the film sheet.