Patent US3856995A successfully refreshed from Google Patents.
US3856995A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pressure gradient piezoelectric microphone
Assignee: International Standard Electric Corp
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Filing: 1973-05-11
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Granted: 1974-12-24
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Expires: 1993-05-11
Abstract
Abstract This invention relates to pressure gradient microphones. A piezoelectric ceramic disc is bonded, face to face, with a thin flexible metal disc. The composite disc is mounted in the center of an open ended hollow cylinder and transversely to the axis of said cylinder. The composite disc is driven by pressure differences between its two faces.
Inventors
- 👤 W Cragg
- 👤 S Bradley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:27
CPC Classifications
H; H04; H04R; H04R17/00; H04R17/02
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
113 words
A pressure gradient microphone comprising: a hollow cylinder having two open ends of equal diameter; a piezoelectric disc transducer; and means for mounting said disc transducer within said cylinder such that the major surfaces of said disc transducer are normal to the longitudinal axis of the cylinder, said means for mounting including a foraminated membrane peripherally fastened to the inside surface of said cylinder, with said disc having one major surface thereof centrally arranged relative to said foraminated membrane and directly attached thereto; said disc transducer when mounted in said cylinder by said means for mounting forming two empty chambers within said cylinder, each of said two chambers providing unrestricted air flow therein.
Claim 2
Dependent Claim
113 words
A pressure gradient microphone comprising: a hollow cylinder having two open ends of equal diameter; a piezoelectric disc transducer; and means for mounting said disc transducer within said cylinder such that the major surfaces of said disc transducer are normal to the longitudinal axis of the cylinder, said means for mounting including a foraminated membrane peripherally fastened to the inside surface of said cylinder, with said disc having one major surface thereof centrally arranged relative to said foraminated membrane and directly attached thereto; said disc transducer when mounted in said cylinder by said means for mounting forming two empty chambers within said cylinder, each of said two chambers providing unrestricted air flow therein.
Claim 3
Dependent Claim
19 words
A pressure gradient microphone according to claim 1 further including a gauze cover over each end of said cylinder.
Claim 4
Dependent Claim
28 words
A pressure gradient microphone according to claim 1 wherein the combination of said foraminated membrane and said transducer is centrally positioned relative to the ends of said cylinder.
Claim 5
Dependent Claim
42 words
A pressure gradient microphone according to claim 3 wherein said transducer has a pair of leads extending therefrom, and wherein the wall of said hollow cylinder proximate said transducer is adapted to permit said leads to extend Out of the cylinder interior.
Claim 6
Dependent Claim
18 words
A pressure gradient microphone according to claim 1 wherein said foraminated membrane is a taut woven gauze membrane.
Claim 7
Dependent Claim
64 words
A pressure gradient microphone according to claim 1 wherein said transducer comprises: a first piezoelectric disc; a first electrode attached to one major surface of said first piezoelectric disc; a second electrode attached to the other major surface of said first piezoelectric disc; and a second disc having equal acoustic stiffness as said first piezoelectric disc attached face to face with said piezoelectric disc.
Claim 8
Dependent Claim
17 words
A pressure gradient microphone according to claim 6 wherein said second disc is a flexible metal disc.
Claim 9
Dependent Claim
45 words
A pressure gradient microphone according to claim 6 wherein said second disc includes: a second piezoelectric disc; a third electrode attached to one major surface of said second piezoelectric disc; and a fourth electrode attached to the other major surface of said second piezoelectric disc.
Claim 10
Dependent Claim
33 words
A pressure gradient microphone according to claim 8 further including two leads connected one to each of the outer electrodes and wherein said first and second piezoelectric discs are polarized in opposite directions.
Claim 11
Dependent Claim
42 words
A pressure gradient microphone according to claim 8 further including two leads connected one to both of the outer electrodes and the other to both of the center electrodes and wherein said first and second piezoelectric discs are polarized in like directions.
Claim 12
Dependent Claim
21 words
A pressure gradient microphone according to claim 8 wherein said first and second piezoelectric discs are made of piezoelectric ceramic material.
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) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |