You can freely build on Chester Carlson's Original Xerography Patent

What this patent covers

This patent describes the fundamental process of xerography, a method for making dry copies of documents. It involves charging a surface with static electricity, exposing it to an image to create an electrostatic latent image, dusting the charged surface with a dry powder (toner), transferring that powder to paper, and then fusing the powder to make the image permanent. The core idea is using static electricity to attract toner particles to form an image, which is then heated to create a lasting copy.

What is now free to use

All 0 claims of US 2297691 are in the public domain. Specifically:

The 0 dependent claims 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.

• Does not cover wet copying processes

• Does not cover processes that use liquid developers instead of dry powder

• Does not cover methods that do not involve an electrostatic latent image

• Does not cover processes that do not use heat to fuse the toner

• Does not cover digital scanning or printing technologies

Who is building on this today

Xerox Corporation, as the direct descendant of Carlson's invention, remains a key player. However, the fundamental principles of xerography are now so widespread that virtually all manufacturers of laser printers and copiers, including Canon, HP, and Brother, build upon this foundational technology.

Products built on expired version of this technology

How to cite this patent in your documentation

Individual. US Patent 2297691. Electrophotography. Granted 1942, expired 1959. 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.