How Hovercrafts Use Flexible Skirts to Ride on Air
This patent describes a gas-cushion vehicle, or hovercraft, that uses a specific arrangement of flexible walls to contain a cushion of pressurized gas and separate foreign matter from the escaping air.
Original patent title: “Gas-cushion vehicles”
This patent describes a gas-cushion vehicle, or hovercraft, that uses a specific arrangement of flexible walls to contain a cushion of pressurized gas and separate foreign matter from the escaping air. Granted to Hovercraft Development Ltd in 1967 with 2 claims and 2 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
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 claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1.
The gap
What does this patent NOT cover?
- 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The clever part is the specific design of the double flexible wall system that creates a vertical chamber. This chamber forces the escaping air to flow upwards, which allows heavier foreign matter, like water droplets or dust, to fall out of the airflow and separate, preventing it from being recirculated or ejected in a way that could cause damage or reduce efficiency.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
SR.N4 Mountbatten class hovercraft
Griffon Hoverwork 8000TD hovercraft
Textron Systems Ship-to-Shore Connector (SSC)
Various commercial and recreational hovercrafts
Why it matters
The bigger picture
This patent is foundational for hovercraft technology, building on the work of Sir Christopher Cockerell, who is widely recognized as the inventorinventorThe person who actually conceived the invention. Listed on the patent regardless of who owns it.Read more → of the modern hovercraft. His designs enabled vehicles to travel over various surfaces, including water, land, and ice, by riding on a cushion of air. The principles laid out here were critical for developing practical hovercrafts used in transport and military applications.
Filed
May 24, 1965
Granted
May 23, 1967
Market context
Who's building on this
Companies in this space
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.
Market impact
The invention of the hovercraft created a new niche in the transportation market, offering a unique capability to traverse both land and water. While not replacing conventional ships or aircraft, hovercrafts found specialized roles in military logistics, search and rescue, and specific ferry services, particularly where amphibious capabilities were crucial. This patent helped solidify the engineering principles that enabled these applications.
Claim 1 — Plain English
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.
The clever bit
The clever part is the specific design of the double flexible wall system that creates a vertical chamber. This chamber forces the escaping air to flow upwards, which allows heavier foreign matter, like water droplets or dust, to fall out of the airflow and separate, preventing it from being recirculated or ejected in a way that could cause damage or reduce efficiency.
What it does not cover
- 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.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Limited data
Citation count
10/40
Early citations
Claim breadth
1/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$3K – $10K
Midpoint $6K · expired or expiring · industry ×0.9
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
1 independent claim · 0 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
2 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Sydney, C. C. (1967). How Hovercrafts Use Flexible Skirts to Ride on Air (U.S. Patent No. 3,321,037). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/3321037/hovercraft-cockerell
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Hovercrafts Use Flexible Skirts to Ride on Air cover?
This patent describes a gas-cushion vehicle, or hovercraft, that uses a specific arrangement of flexible walls to contain a cushion of pressurized gas and separate foreign matter from the escaping air.
Who owns patent US 3321037?
Hovercraft Development Ltd owns this patent, granted in 1967.
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 3321037 cited by?
This patent has been cited by 2 later patents that build on its ideas.
What problem does this patent solve?
This patent is foundational for hovercraft technology, building on the work of Sir Christopher Cockerell, who is widely recognized as the inventor of the modern hovercraft. His designs enabled vehicles to travel over various surfaces, including water, land, and ice, by riding on a cushion of air. The principles laid out here were critical for developing practical hovercrafts used in transport and military applications.
What does this patent NOT cover?
Does not cover air-cushion vehicles that lack the specific 'wall means' creating an upward-flowing chamber for foreign matter separation.
Patent monitoring