sylphon

noun

syl·​phon

ˈsilˌfän

plural sylphons

: a thin-walled tubular bellows used in temperature and pressure regulators, bellows seals, and expansion joints

In between, a maze of valves, venturis (short tubes with constricted throats), and sylphons (pleated metal bellows) interacted with one another, maintaining conditions inside the airplane as outside pressure varied.

—Nick D'Alto, Air & Space Smithsonian, September 2000

—formerly a U.S. registered trademark

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