You can freely build on How Hovercrafts Use Flexible Skirts to Ride on Air

What this patent covers

The patent outlines a vehicle body supported by a cushion of gas. It features an inner flexible wall structure, with its upper part fixed to the vehicle and its lower part hanging freely, which helps contain the gas cushion. Crucially, there's an outer 'wall means' spaced from this inner flexible wall, forming a vertical chamber. This outer wall also has a flexible part that hangs down, reaching at least the same level as the inner flexible wall. Gas is supplied directly into the space beneath the vehicle. As gas escapes from the cushion, it flows upward through this chamber, allowing foreign matter like water spray or dust to separate and settle within the chamber, as described in claim 1.

What is now free to use

All 1 claims of US 3321037 are in the public domain. Specifically:

• Claim 1: A GAS-CUSHION VEHICLE — 1 specific element

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 air-cushion vehicles that lack the specific 'wall means' creating an upward-flowing chamber for foreign matter separation.

• Does not cover hovercraft designs where the outer flexible wall does not extend downward to substantially the same level as the inner flexible wall.

• Does not cover vehicles that use rigid skirts or walls instead of the described flexible wall structures.

• Does not cover hovercrafts where the escaping gas does not flow upward through a chamber designed to separate foreign matter.

Who is building on this today

Companies like Griffon Hoverwork and Textron Systems continue to develop and manufacture hovercrafts for military, commercial, and rescue operations. These modern designs build upon the fundamental principles established in early patents like this one, focusing on improvements in efficiency, payload capacity, and operational versatility.

Products built on expired version of this technology

How to cite this patent in your documentation

Hovercraft Development Ltd. US Patent 3321037. Gas-cushion vehicles. Granted 1967, expired 1985. 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.