US3571813A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Acoustical ear muff with cone-type cushions
Assignee: RTX BBN Technologies Corp
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Filing: 1969-05-21
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Granted: 1971-03-23
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Expires: 1989-05-21
Abstract
Abstract This disclosure deals with a novel acoustical ear muff and the like employing a novel cushion that provides a soft and compliant seal, conforming readily to the irregular contour of the head even when that contour varies with time, as when the wearer is talking or chewing; but, when firmly sealed to the head around the entire periphery of the cushion, the cushion then presents a high stiffness against alternating forces induced by an incident sound field, thus minimizing any resulting change in enclosed volume of the ear muff and consequently minimizing the sound pressure developed at the ear.
Inventors
- 👤 Clayton H Allen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 22:07
CPC Classifications
A; A61; A61F; A61F11/00; A61F11/06; A61F11/14
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
148 words
An acoustical ear muff having, in combination, a hard shell, a frustoconical cushion member the larger end of which is intimately connected with and restrained by said hard shell, the cushion member being free to deflect at its smaller end in a direction normal to the surface of the cone thereof to accommodate to the shape of the head around the ear of the wearer and having elastic restoring means tending to maintain such frustoconical shape, said restoring means comprising a viscoelastic material of time constant that enables rapid accommodation of changes in shape of the surface of the head of the wearer, as during talking, chewing and the like at frequencies under approximately 5 Hz. but said time constant being short compared with the period of vibratory forces impressed on the cushion member by sound waves of audible frequencies above approximately 50 Hz. incident upon the muff.
Claim 2
Dependent Claim
148 words
An acoustical ear muff having, in combination, a hard shell, a frustoconical cushion member the larger end of which is intimately connected with and restrained by said hard shell, the cushion member being free to deflect at its smaller end in a direction normal to the surface of the cone thereof to accommodate to the shape of the head around the ear of the wearer and having elastic restoring means tending to maintain such frustoconical shape, said restoring means comprising a viscoelastic material of time constant that enables rapid accommodation of changes in shape of the surface of the head of the wearer, as during talking, chewing and the like at frequencies under approximately 5 Hz. but said time constant being short compared with the period of vibratory forces impressed on the cushion member by sound waves of audible frequencies above approximately 50 Hz. incident upon the muff.
Claim 3
Dependent Claim
27 words
An acoustical ear muff as claimed in claim 1 and in which said hard shell is generally ellipsoidal and has hiGh vibration loss factor at acoustic frequencies.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-22 | 1974-09-21 | 1975-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-22 | 1978-09-21 | 1979-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-22 | 1982-09-21 | 1983-03-23 | $7700.00 | Window Closed / Lapsed |