You can freely build on How Glass Fibers Are Spun for Insulation
This patent expired in 1955. 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
Owens Illinois Glass Co
Patent granted
1938
Expired
1955
Forward citations
22
What this patent covers
The patent details a method for producing glass wool by melting glass and using high-velocity steam or air jets to attenuate the molten material into thin, flexible fibers. These fibers are then collected to form a mat or batt of insulating material. By controlling the temperature of the glass and the pressure of the gas blast, the process creates a lightweight, fire-resistant, and thermally efficient material that traps air within the fiber matrix.
What is now free to use
All 0 claims of US 2133235 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 the chemical composition of the glass itself.
Does not cover the use of centrifugal force or spinning disks to form fibers.
Does not cover the application of binding resins to hold the fibers together.
Who is building on this today
Owens Corning, the successor to the original research efforts, remains a global leader in fiberglass production. Modern manufacturers continue to refine the energy efficiency and fiber diameter control of this basic thermal attenuation process.
Products built on expired version of this technology
Residential attic insulation batts
Commercial building HVAC duct lining
Industrial pipe insulation
How to cite this patent in your documentation
Owens Illinois Glass Co. US Patent 2133235. Method and apparatus for making glass wool. Granted 1938, expired 1955. 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.