Electret acoustic transducer and method of making

Claim 2

In an electroacoustic transducer having a backplate element and a diaphragm element, the combination of a first electrode serving as onE of said elements, an electret and a second electrode bonded together serving as the other of said elements, a set of supporting members disposed in a predetermined pattern between said elements normally to hold said elements a substantially fixed distance apart and to form therewith a plurality of similar individual transducing cells in parallel and means for holding said diaphragm in taut disposition across the supporting members of said set.

Claim 3

In an electroacoustic transducer as defined in claim 1, the combination wherein one of said elements is imperforate and the other of said elements is perforated.

Claim 4

In an electroacoustic transducer as defined in claim 2, the combination wherein the grid of supporting members is an integral part of the perforated backplate element and is fabricated of molded plastic and coated with metal to provide electrical conductivity.

Claim 5

In an electroacoustic transducer as defined in claim 2, the combination wherein said electret consists essentially of a polyhalocarbon.

Claim 6

In an electroacoustic transducer as defined in claim 4, the combination wherein said polyhalocarbon comprises a material containing at least 95 percent polychlorotrifluoroethylene.

Claim 7

An electroacoustic transducer, comprising a pair of electrodes, at least one of said electrodes comprising a metallized film fixed to an electret having a dielectric surface confronting the other electrode, a first of said electrodes comprising a membrane serving as a diaphragm, a grid of supporting elements attached to the surface of the other electrode confronting said first electrode and adapted to engage the confronting surface of the first electrode to hold it a fixed distance from the surface of the other electrode and to form therewith a plurality of individual, similar transducing cells in parallel, and means for retaining said electrodes in assembled condition with said first electrode stretched over said grid of supporting elements and closing said cells.

Claim 8

An electroacoustic transducer, comprising a pair of electrodes, at least one of said electrodes comprising a metallized film fixed to an electret having a dielectric surface confronting the other electrode, a first of said electrodes comprising a membrane serving as a diaphragm, a grid of supporting elements attached to the surface of the other electrode confronting said first electrode and adapted to engage the confronting surface of the first electrode to hold it a fixed distance from the surface of the other electrode and to form therewith a plurality of individual, similar transducing cells in parallel, and means for retaining said electrodes in assembled condition with said first electrode stretched over said grid of supporting elements and closing said cells.

Claim 9

In an electroacoustic transducer of the type comprising two electrodes, one attached to a diaphragm and the other forming a backplate confronting the diaphragm, one of said electrodes comprising a metallized surface on an electret, said electret forming the diaphragm and including an internally polarized sheet of dielectric material confronting the other electrode, the improvement comprising a set of supporting elements formed on the side of the backplate confronting the diaphragm, said supporting elements engaging the diaphragm to form therewith a plurality of individual transducing cells in parallel, to control the spacing between the diaphragm and the backplate and prevent electroacoustic sticking of the diaphragm to the backplate and means for holding said diaphragm in taut disposition across said supporting elements.

Claim 10

In an electroacoustic transducer of the type comprising two electrodes, one attached to a diaphragm and the other forming a backplate confronting the diaphragm, one of said electrodes comprising a metallized surface on an electret, said electret forming the diaphragm and including an internally polarized sheet of dielectric material confronting the other electrode, the improvement comprising a set of supporting elements formed on the side of the backplate confronting the diaphragm, said supporting elements engaging the diaphragm to form therewith a plurality of individual transducing cells in parallel, to control the spacing between the diaphragm and the backplate and prevent electroacoustic sticking of the diaphragm to the backplate and means for holding said diaphragm in taut disposition across said supporting elements.

Claim 11

The transducer of claim 6 in which said first electrode is attached to an electret and the other electrode is a conductive metal backplate, in which said supporting elements comprise fine metal supports extending outwardly from the surface of the backplate to engage the dielectric surface of the electret, further comprising means including apertures formed in the backplate to provide a compression chamber large compared to the volume swept by the diaphragm during the operation of the transducer.

Claim 12

In combination, two transducers of claim 7 in which a set of apertures are formed in the backplates to put the spaces between the diaphragms and backplates into acoustic communication with the surfaces of the backplates opposite the diaphragms, and means mounting the transducers together with the last recited surfaces of the backplates in engagement and the metallized surfaces of the electrets forming the outer surfaces of the mounted combination.

Claim 13

An electroacoustic transducer, comprising an apertured conducting metal plate, a grid of fine metal wires formed on both sides of said plate, two electret diaphragms each comprising a layer of internally polarized dielectric material aNd a layer of metal bonded to said dielectric layer, and means for holding each of said diaphragms stretched over a different side of said apertured metal plate and supported on said metal wires, the dielectric layers of said diaphragms being in contact with said wires to form a plurality of individual similar transducing cells in parallel relationship.

Claim 14

An electroacoustic transducer, comprising an apertured conducting metal plate, a grid of fine metal wires formed on both sides of said plate, two electret diaphragms each comprising a layer of internally polarized dielectric material aNd a layer of metal bonded to said dielectric layer, and means for holding each of said diaphragms stretched over a different side of said apertured metal plate and supported on said metal wires, the dielectric layers of said diaphragms being in contact with said wires to form a plurality of individual similar transducing cells in parallel relationship.

Claim 15

An electroacoustic transducer, comprising an electret, a metallic diaphragm, and means holding the diaphragm stretched over and confronting a first surface of said electret, said electret comprising a relatively thick sheet of internally polarized dielectric material permeated with holes and having formed on said first surface a grid of supporting elements in contact with said diaphragm to form a plurality of individual transducing cells, to control the spacing between the diaphragm and the electret and to prevent electrostatic sticking of the diaphragm to the electret, and a metallic coating on a second side of said electret opposite said first side.

Claim 16

An electroacoustic transducer, comprising an electret, a metallic diaphragm, and means holding the diaphragm stretched over and confronting a first surface of said electret, said electret comprising a relatively thick sheet of internally polarized dielectric material permeated with holes and having formed on said first surface a grid of supporting elements in contact with said diaphragm to form a plurality of individual transducing cells, to control the spacing between the diaphragm and the electret and to prevent electrostatic sticking of the diaphragm to the electret, and a metallic coating on a second side of said electret opposite said first side.

Claim 17

An electroacoustic transducer, comprising an electret, a metallic diaphragm, and means holding the diaphragm stretched over and confronting a first surface of said electret, said electret comprising a relatively thick sheet of internally polarized dielectric material permeated with holes and having formed on said first surface a grid of supporting elements in contact with said diaphragm to form a plurality of individual transducing cells to control the spacing between the diaphragm and the electret and to prevent electrostatic sticking of the diaphragm to the electret, a metallic coating on a second side of said electret opposite said first side, a sheet of nonporous conducting material, means forming a chamber sealed at one end by said diaphragm and at an opposite end by said material, and a grid of nonconducting support elements in said chamber and supporting said electret above said material whereby the interstices between the support elements provide a compression chamber for said transducer, an electrical connection between one side of said material and said diaphragm, and an electrical connection between the other side of said material and said metallic coating.

Claim 18

An electroacoustic transducer, comprising an electret, a metallic diaphragm, and means holding the diaphragm stretched over and confronting a first surface of said electret, said electret comprising a relatively thick sheet of internally polarized dielectric material permeated with holes and having formed on said first surface a grid of supporting elements in contact with said diaphragm to form a plurality of individual transducing cells to control the spacing between the diaphragm and the electret and to prevent electrostatic sticking of the diaphragm to the electret, a metallic coating on a second side of said electret opposite said first side, a sheet of nonporous conducting material, means forming a chamber sealed at one end by said diaphragm and at an opposite end by said material, and a grid of nonconducting support elements in said chamber and supporting said electret above said material whereby the interstices between the support elements provide a compression chamber for said transducer, an electrical connection between one side of said material and said diaphragm, and an electrical connection between the other side of said material and said metallic coating.

Claim 19

An electroacoustic transducer, comprising a pair of plates mounted in confronting relationship, one of said plates comprising an electret having a dielectric surface confronting the other electrode, and an opposed metallized surface, the other of said plates comprising a metallic conductor, one of said plates being relatively rigid and pierced for acoustic airflow to serve as a backplate, the other of said plates being imperforate and flexible to serve as a diaphragm, a grid of supporting elements formed on the surface of the relatively rigid plate confronting the other plate, said elements and said pair of plates forming a plurality of similar individual transducing cells, and means for holding said diaphragm in taut disposition across said grid of supporting elements.

Claim 20

An electroacoustic transducer, comprising a pair of plates mounted in confronting relationship, one of said plates comprising an electret having a dielectric surface confronting the other electrode, and an opposed metallized surface, the other of said plates comprising a metallic conductor, one of said plates being relatively rigid and pierced for acoustic airflow to serve as a backplate, the other of said plates being imperforate and flexible to serve as a diaphragm, a grid of supporting elements formed on the surface of the relatively rigid plate confronting the other plate, said elements and said pair of plates forming a plurality of similar individual transducing cells, and means for holding said diaphragm in taut disposition across said grid of supporting elements.

Claim 21

A weather-resistant electroacoustic transducer, comprising a first diaphragm, a second diaphragm, and means forming a container closed by said first diaphragm, said first diaphragm comprising an extensible, flexible imperforate seal to permit expansion and contraction of the space enclosed by the container, said second diaphragm comprising a first flexible, imperforate electrode, a second perforated electrode mounted in a confronting relation to said first electrode, one of said electrodes comprising an electret having a conducting surface and a dielectric surface, said dielectric surface confronting the other electrode, and a grid of support elements formed on the surface of the second electrode confronting the first electrode for engaging and supporting the first electrode in substantially fixed spaced relationship, said elements and said electrodes forming a plurality of individual transducing cells in parallel relationship.

Claim 22

A weather-resistant electroacoustic transducer, comprising a first diaphragm, a second diaphragm, and means forming a container closed by said first diaphragm, said first diaphragm comprising an extensible, flexible imperforate seal to permit expansion and contraction of the space enclosed by the container, said second diaphragm comprising a first flexible, imperforate electrode, a second perforated electrode mounted in a confronting relation to said first electrode, one of said electrodes comprising an electret having a conducting surface and a dielectric surface, said dielectric surface confronting the other electrode, and a grid of support elements formed on the surface of the second electrode confronting the first electrode for engaging and supporting the first electrode in substantially fixed spaced relationship, said elements and said electrodes forming a plurality of individual transducing cells in parallel relationship.

Claim 23

The transducer of claim 14, further comprising means forming a chamber having a sUbstantially constant volume within said container and closed by said second diaphragm, said chamber enclosing said perforated electrode, and said chamber having at least one restricted passage in communication with the region of said container closed by said first diaphragm to permit gradual equalization of pressures on opposite sides of said second diaphragm.

Claim 24

An electret which consists essentially of an electrostatically polarized polyhalocarbon.

Claim 25

An electret which consists essentially of an electrostatically polarized polyhalocarbon.

Claim 26

An electret as defined in claim 16 wherein said polyhalocarbon is at least 95 percent polychlorotrifluoroethylene.

Claim 27

An electret as defined in claim 17 in the form of a film having a thickness between 0.0005 inch and 0.010 inch.

Claim 28

The electroacoustic transducer of claim 1 wherein said means for holding said diaphragm in taut disposition comprises support means in fixed position relative to said backplate and means for firmly pressing said diaphragm against said support means.

Claim 29

The electroacoustic transducer of claim 1 wherein said set of supporting element is in grid configuration.