US3652810A

US3652810A - Microphone having a protective cap

Info

Publication number: US3652810A
Application number: US31863A
Authority: US
Inventors: Bernhard Weingartner
Original assignee: AKG Akustische und Kino Geraete GmbH
Current assignee: AKG Acoustics GmbH
Priority date: 1965-04-23
Filing date: 1970-05-01
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28
Also published as: GB1102306A; DE1290978B; DE1290978C2; AT252343B

Abstract

A microphone includes a microphone housing having a sound transducer therein. A cover of substantially cup-shaped configuration fits over one end of the housing above the transducer and it is made of a material which comprises a plurality of particles which are sintered together or fused together in a manner to define tortuous passages therebetween and to define hollow spaces remaining between the particles, and which hollow spaces are interconnected, thus forming irregular channels which assure the sound permeability of the cap but are impenetrable by dust or other air pollutants.

Description

United States Patent Weingartner [4 1 Mar. 28, 1972 MICROPHONE HAVING A i 1 References Cited PROTECTIVE CAP UNITED STATES PATENTS 1 lnvemorl W Welngmner, Mauerbers, 2,702,318 2/1955 Dvorsky ..179/121 1) ma 3,236,328 2/1966 Burroughs ..l79/l84 [73] Assignee: Akustische U. Kino-Gerate Gesellschaft 2,556,168 6/1951 Cragg a1 -179/184 Vienna, Austria 2,444,620 7/ 1948 Williams et al. ..l79/l 10 [22] Filed: May 1970 Primary Examiner-Kathleen l-l. Claffy [211 App} NOJ 31,863 Assistant Examiner-Thomas W. Brown Attorney-McGlew and Toren Related US. Application Data [63] Continuation of Ser. No. 542,419, Apr. 13, 1966, [57] ABSTRACT abandoned. A microphone includes a microphone housing having a sound transducer therein. A cover of substantially cup'shaped con- Foreign Application Priority Data figuration fits over one end of the housing above the trans ducer and it is made of a material which comprises a plurality Apr. 23, i965 Austrla A374 2 of particles which are Simered together fused together in a [52] us Cl I I I "179/184 179/179 manner to define tortuous passages therebetween and to 51 1m.c1.IIILI.....IIIIIII.I.IIII.....IIIIIIIIIII ..l-l04rl/08 define Spaces remaimng between Particles and [58] Field of Search ..179/121 D 184 which Spaces are imemnnected, fmming lar channels which assure the sound permeability of the cap but are impenetrable by dust or other air pollutants.

9 Claims, 1 Drawing Figure I g 8 I 817" A 6 50 JAN/\JAL PATENTED MAR 28 I972 INVENTOR BERN HARD WEIN6/IRTNER MM W ATTORNEY 5 MICROPHONE HAVING A PROTECTIVE CAP This is a continuation of application Ser. No. 542,419, filed Apr. 13, 1966, now abandoned.

This invention relates in general to microphone construction and in particular to a new and useful microphone housing and cover construction and to an improved microphone cover composed of three-dimensional particles which are sintered together.

Microphones are usually provided with a protective cover which protects the thin and extremely delicate diaphragms of the transducer system from mechanical damage and prevents penetration of dust and dirt particles into the transducer system. Such covers are usually made up of a plurality of separate part elements which are fitted together; for example, they usually include a rigid part or mechanical protection and a filter element consisting of a very fine meshed wire or gauze fabric for the protection of the transducer system from dirt and similar impurities. The mechanical protection part may require a considerable manufacturing expense and may comprise, for example, a thick stiff wire formed into a hemispherical structure or a hollow body of plastic or metal material which is formed with sound inlet apertures. Sometimes a further layer is added which comprises a sound permeable material such as a foamed plastic or nonwoven textile or the like which also affords protection against Wind. In spite of the expense of manufacture, these covers have the disadvantage that iron particles may penetrate into the microphones and interfere with the function thereof especially if they become deposited in the narrow gap of the microphone, particularly in electrodynamic microphone, particularly in electrodynamic microphones which have a working air gap permeated by a very strong magnetic field.

In accordance with the present invention the disadvantages of the prior art are overcome by providing a cover which is formed of a sintered material having particles of spherical or irregular shape which are formed together into a single cover element, which is capable of performing all of the functions required for protection and operation of the microphone. In the preferred arrangement of the invention, the sintered material of the cover comprises preferably metallic particles such as spherical bronze particles about 0.7 to l millimeter in diameter. In special cases where a lesser filtering action will be satisfactory, it is possible to use a sintered plastic material comprising spherical particles of thermoplastic material which are partially sintered together. In accordance with a feature of the invention, the wall thickness of the protective cover should not exceed twice the diameter ofa spherical particle of the sintered material. A cover made up of sintered particles constructed in accordance with the invention provides an extremely high mechanical stability as well as a pleasing appearance in spite of its great strength. When the particles are sintered together into a cover construction, they have a sufficient spacing for sound permeability, but they define a tortuous and long path for the flow of impurities with the inflow passage being regularly curved and provided with corner spaces where the impurities will deposit before they can enter into the microphones. A further advantage is that since the sound waves must also traverse a relatively long path into the transducer portions of the microphone there is an inherently good protection of the microphone from the effects of wind.

Accordingly, it is an object of the invention to provide a microphone housing and cover construction in which the cover is easily and simply fitted over the housing and is made of three dimensional particles which are sintered together.

A further object of the invention is to provide a microphone cover which is made up of sintered particles such as spherical bronze particles of from 0.7 to 1 millimeter in diameter, plastic particles and the like, which provides a safe protection of the microphone from dust and impurities and which provides for satisfactory sound transmissions.

A further object of the invention is to provide a microphone cover and a microphone cover and housing construction which are simple in design, economical to manufacture and rugged in construction.

The various features of novelty which characterize the invention are pointed out with particularlity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

The only figure of the drawing indicates a partial elevational and partial transverse sectional view of a microphone constructed in accordance with the invention.

Referring to the drawing, in particular, the invention embodied therein includes a microphone housing generally designated 1 which is of tubular configuration and includes an upper flared portion 3. The upper flared portion 3 includes an internal annular recessed portion 3a defining a ledge 7 which forms an annular seat for a transducer assembly generally designated 2. The transducer assembly 2 includes a collar portion 8 having a top bevel 8a and a bottom bevel 8b. The bottom bevel portion 8b fits into the recess 3a and conforms to the side walls of the recess 30 and the microphone transducer assembly 2 rests on the ledge portion 7.

In accordance with a feature of the invention, the housing is formed in a simple manner so that the transducer assembly 2 may be positioned on the groove 7 and secured in position such as with securing bolts 6 which extend through the wall of the flared portion 3 into the collar 8.

In accordance with a further feature of the invention, the microphone includes a unitary construction cover or cap 5 which is made up of a plurality of particles, preferably metallic particles such as spherical bronze particles of from 0.7 to 1 millimeter in diameter, which are sintered or fused together. In the embodiment illustrated, the cover 5 is made of a cupshaped configuration and it has a top wall 5t which is sound permeable and

internal walls

5a and 5b which are of the same slope as the bevelled portion 8a of the collar 8 so that the cover may be easily positioned thereover. In some instances, it is also preferable to provide securing screws (not shown) similar to the screws 6 which will extend downwardly through the cover 5 into the collar 8. Where only a small filtering action is desired, it will be possible to form the cover 5 of a sintered plastic material such as spherical particles of thermoplastic material. In the preferred arrangement, the wall thickness of the protective cover could not exceed twice the diameter of a spherical particle of the sintered material which is used to make the cover. The term sintering is used in this specification to indicate a caking together of material particles at elevated temperatures and is generally used to be synonymous with the term fused which is also employed herein. When the particles are sintered, they bond together at the points of contact and where they are not in contact a cavity remains which communicates with the next adjacent cavities so that a channel or passage is defined through the sintered material and such passages become finer or smaller the smaller the dimensions of the sintered particles are.

The protective cover 5 may be matched to various housing materials by suitable surface finishing treatments such as anodizing, electroplating, etc. When it is made of sintered plastic materials, the materials employed may be of different colors.

The sintered material which constitutes at least the top 5: of the protective cover 5 and advantageously also the

side walls

5a and 5b must be permeable to sound so that the sound will be transmitted through the cover without any modification. This is achieved through the multiplicity of passages which are formed between the sintered particles. Because of the sintered structure of the cover 5, these passages are nonlinear so that they will not permit a laminar flow of air through the cover.

The particles which are sintered together may be spherical or may have an irregular shape.

The protective cover 5 has various advantages over covers of other types. It has an extremely high mechanical stability and a pleasing appearance in spite of its high strength. The

path to be traversed by any impurities which would tend to enter through the protective cover 5 will be much longer than a corresponding path, for example, in a well known protecting device such as a gauze shield, for example. The path defined between adjacent particles which are sintered together is irregularly curved and is provided with corner spaces or dead areas which trap any impurities and insure that they cannot inflict damage. The fact that sound must traverse the protective cover along a relatively long path provides a good protection against wind interference.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A dynamic microphone construction comprising a microphone housing, a dynamic sound transducer mounted in said housing, and substantially acoustically neutral shielding means for protecting the transducer and for minimizing the effect on the acoustic response of said transducer to sound outside the shielding means, said shielding means forming a cover for said housing extending over said sound transducer, said cover being of unitary construction and made up of a plurality of three dimensional particles sintered together and defining tortuous passages therebetween and defining at least one sound permeable wall portion adjacent said transducer; said cover, with said sound transducer, defining a large volume air space, and being spaced from said transducer; said cover being self supporting, the sintered particles defining tortuous sound wave air passages to trap impurities and to protect against wind effects.

2. A microphone according to claim 1, in which said three dimensional particles are substantially spherical.

3. A microphone according to claim 1, in which said three dimensional particles have an irregular shape.

4. A microphone according to claim 1, wherein said particles are metal.

5. A microphone according to claim 1, wherein said three dimensional particles are spherical bronze.

6. A microphone according to claim 1, wherein said three dimensional particles are spherical and are synthetic plastic material.

7. A microphone according to claim 1, wherein said particles have a diameter in the range from 0.7 to 1.0 millimeters.

8. A microphone according to claim 1, wherein said cover has a wall thickness which is approximately twice the diameter of said three dimensional particles.

9. A microphone according to claim 1, wherein said housing is substantially tubular and includes an upwardly and outwardly flaring tip portion, said upwardly flaring portion having an internal annular recess defining an annular ledge at the bottom of said recess, a transducer assembly supported on said ledge, said transducer assembly including a collar having a bevelled edge complementary to the surface of said recess and further including an upwardly and an inwardly bevelled top edge, said cover including a flat top portion and two divergent side wall portions, said side wall portions having a slope complementary to the bevelled top edge of said annular ring of said transducer and fitting therearound.

Claims

4. A microphone according to claim 1, wherein said particles are metal.