You can freely build on How William Coolidge Invented the Modern X-Ray Tube
This patent expired in 1933. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
General Electric Co
Patent granted
1916
Expired
1933
Forward citations
32
What this patent covers
The patent describes a vacuum tube designed for generating X-rays by heating a tungsten filament to emit electrons. Unlike previous designs that relied on residual gas to conduct electricity, this tube maintains a high vacuum, allowing the user to precisely control the electron beam's intensity and energy. By adjusting the filament temperature, the operator can independently regulate the number of electrons hitting the target, which directly controls the X-ray output.
What is now free to use
All 0 claims of US 1203495 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 X-ray tubes that rely on gas discharge for electron production.
Does not cover non-vacuum electronic tubes or cold-cathode discharge devices.
Does not cover the medical imaging software or digital sensors used to process X-ray data.
Who is building on this today
General Electric continued to dominate the medical imaging market for decades, evolving this technology into the sophisticated CT scanners and diagnostic systems produced by GE HealthCare today.
Products built on expired version of this technology
Early 20th-century medical X-ray machines
Industrial radiography equipment
High-voltage vacuum rectifiers
How to cite this patent in your documentation
General Electric Co. US Patent 1203495. Vacuum-tube.. Granted 1916, expired 1933. 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.