US3663768A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electret transducer
Assignee: Nortel Networks Ltd
•
Filing: 1971-01-15
•
Granted: 1972-05-16
•
Expires: 1991-01-15
Abstract
Abstract An electret transducer comprising a metallized diaphragm tensioned in juxtaposition with a metallic backplate in which the width to height of the air gap between the two is selected so that the sensitivity remains substantially constant over the life of the transducer. The backplate contains ridges over which the diaphram is tensioned.
Inventors
- 👤 Henning Schmidt Madsen
- 👤 Cornelis Wilfred Reedyk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:26
CPC Classifications
H; H04; H04R; H04R19/00; H04R19/01
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
99 words
An electret transducer comprising: a perforated backplate having both a conductive surface and a plurality of parallel ridges on one side thereof; and an electret diaphragm tensioned over the parallel ridges; the diaphragm having a metallized surface on the side opposite that in contact with the ridges; in which the ratio of the distance between said ridges to the height of the ridges is between about 100:1 and 40:1 whereby the sensitivity of the transducer remains substantially constant when the equivalent bias voltage resulting from the surface charge density of the electret varies between about 200 and 50 volts.
Claim 2
Dependent Claim
99 words
An electret transducer comprising: a perforated backplate having both a conductive surface and a plurality of parallel ridges on one side thereof; and an electret diaphragm tensioned over the parallel ridges; the diaphragm having a metallized surface on the side opposite that in contact with the ridges; in which the ratio of the distance between said ridges to the height of the ridges is between about 100:1 and 40:1 whereby the sensitivity of the transducer remains substantially constant when the equivalent bias voltage resulting from the surface charge density of the electret varies between about 200 and 50 volts.
Claim 3
Dependent Claim
24 words
An electret transducer as defined in claim 1 in which the tension on the diaphragm is between about 10 and 20 Newtons per meter.
Claim 4
Dependent Claim
27 words
An electret transducer as defined in claim 2 in which the ratio of the distance between said ridges to the height of the ridges is about 70:1.
Claim 5
Dependent Claim
36 words
An electret transducer as defined in claim 1 which has a plurality of conductive areas between said ridges interconnected by narrow conductive portions over the ridges so as to minimize the fixed capacity of the transducer.
Claim 6
Dependent Claim
26 words
An electret transducer as defined in claim 1 in which the coefficient of expansion of the perforated backplate and the electret diaphragm are substantially the same.
Claim 7
Dependent Claim
29 words
An electret transducer as defined in claim 5 in which the material in the backplate consists of acrylonitrile butadiene styrene and the material in the diaphragm consists of tetrafluoroethylene.
Claim 8
Dependent Claim
71 words
In an electret transducer comprising: a perforated backplate having a plurality of parallel ridges on one side thereof; an electret diaphragm tensioned over the parallel ridges, the diaphragm having a metallized surface on the side opposite that in contact with the ridges; the improvement comprising: said backplate having conductive areas between said ridges interconnected by narrow conductive portions over the ridges so as to minimize the fixed capacity of the transducer.
Claim 9
Dependent Claim
71 words
In an electret transducer comprising: a perforated backplate having a plurality of parallel ridges on one side thereof; an electret diaphragm tensioned over the parallel ridges, the diaphragm having a metallized surface on the side opposite that in contact with the ridges; the improvement comprising: said backplate having conductive areas between said ridges interconnected by narrow conductive portions over the ridges so as to minimize the fixed capacity of the transducer.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-16 | 1975-11-15 | 1976-05-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-16 | 1979-11-15 | 1980-05-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-16 | 1983-11-15 | 1984-05-16 | $7700.00 | Window Closed / Lapsed |