US1721109A - Loud-speaker - Google Patents

Description

Patented July 16, w29.

UNiTED stares N F F ECE.

RICHARD FRENKEL, 0F BERLIN-GRUNEWALD, GERMANY.

LOUD-SPEAKER.

Application led April 1G, 1926, Serial No. 102,539, and in Germany April 17, 1925.

This invention relates to devices for reproducing sound by the aid of a diaphragm, such as sound boxes vfor gramophones and the like, receivers for telephones, Wireless apparatus and so forth.

The invention comprises in combination with a diaphragm adapted to be vibrated mechanically or electromagnetically, a second diaphragm or membrane stretched substantially parallel with the first at a short distance from it. The invention also comprises the several constructions, means of atttaching and tensioning diaphragms, and conformations of sound box described hereinafter.

Examples of loud speakers constructed in accordance with the invention are illustrated in axial section in the accompanying drawings.

Figure 1 shows one form or embodiment of my invention; Fig. 2 is a similar structure to Fig. 1 but constituting an improved form thereof; Fig. 3 is another embodiment of the invention similar to Fig. 1; .and rig. 4 is an improvedy form of the structure shown in Fig. 3.

In all the constructions illustrated there is a case l, which in an electromagnetically opcrated instrument contains an electromagnet 2. Adjacent the poles of this is a diaphragm 3, which ordinarily is of magnetic material to co-act with the magnet; this closes the mouth of the case. Near the diaphragm 3 and substantially parallel with it there is mounted a second diaphragm or membrane 4. 'l` his mav consist of a thin sheet of metal foil, paper or the like; metal foil of from .001 to l m. in. has been found suitable, and a membrane consisting of copper foil tinned or varnished gives a pleasant soft tone. The two diaphragms are separated by the ring 5. The diaphragms are secured in place by a cover 6. which may be fastened in any suitable way to the case 1, as by screws passing through its edge and the flange of the case as indicated in Figure 4. In the cover 6 there is a sound openingr 8, generally formed with a tubulure for the attachment of a horn or trumpet.

In the construction of Figure 1 the outer part of ring 5 is of less thickness than the inner part, and the flange 7 of the cover 6 is shaped to conform to it. Consequently when the flange is drawn down upon the ring by the fastening means, the diphragm 4 is-both gripped and tensioned. The inner surface of the cover 6 in Figure 1 is flat and substantially parallel with the diaphragms.

, In the construction of Figure 2 the space above the dia hragm 4 is conical. To produce this resu t a ring 9 is inserted between the cover 6 and the diaphragm 4, said ring having a conical interior surface. Alternatively as indicated in Figure 3 the cover 6 itself may be conical, or have a conical interior surface. This conformation of the space between the diaphragms and the sound opening has been found to produce more natural tones. The conical surface may be straight lines or curves of any desired shape.

In the construction of Figure 3 the Aring 5 is made of rubber or other' soft and compressible materal. The cover 6 is formed with annular ribs 10 which extend into the soft ring 5 and thereby bring about the tensioning of the diaphragm 4 substantially as described with reference to Figure 1.

In the construction of Figure 4 the ribs 10 integral with the cover arereplaced by independent rings 11, for instance of wire, which similarly ress the diaphragm 4 into the soft ring 5 and) thereby tension it.

What I claim is 1. In combination a casinof having an opening of small area compared with the crosssection of said casing, two diaphragms extending across said casing parallel with one another and a short distance apart, one of said diaphragms being of magnetic material and the other of said diaphrafrms being of thin metallic foil and means for vibrating said ma etic diaphragm for imparting corresponding vibrations to said thin metallic foil diaphragm.

2. A loud speaking telephone comprising a casing, a magnetic diaphragm secured in said casing, an electro-magnet 1n said casing adjacent said diaphragm, a sheetlike diaphragm fastened in said casing substantially parallel with said magnetic diaphragm and means extending from said casing for stretching said sheet-like diaphragm in radial directions. v

3. A device for reproducing sound comprising a case, a diaphragm closing the mouth of said case, means for vibrating said daphragm, a ring disposed upon said diav phragm, a membrane stretched over said ring tioned diaphragm, and means fastening and tensioning said membrane in position between said case and said ring.

4. A device for reproducing sound, comprising a circular casing having an opening substantially smaller in diameterthan the diameter of said casing and a coned interior surface adjacent said casing, a membrane stretched across the base of said coned surface a diaphragm positioned parallel with said membrane at a short distance therefrom, and means for imparting vibrations to said diaphragm.

5. A device for reproducing sound comprising a iianged case, a diaphragm closing the mouth of said case, means for imparting vibrations to said diaphragm, an annular casing ring resting upon the edge of said diaphragm, a membrane upon said ring, a cover adapted to engage said ring and means interposed between said cover and said spacer ring for tensioning said membrane.

6. A loud speaker comprising a casing, a diaphragm extending across said casing, means for vibrating said diaphragm, a second very thin diaphragm stretched across said casing and a exible member spacing one of said diaphragms substantially parallel to and 'at a short distance from the iii-st.

7. A loud speaker comprising a casing, a

diaphragm extending across said casing, means for Vibratin said diaphragm, and a second very thin diaphragm of tinned co per sheet stretched across said casing su stantially parallel toand at a short distance from thefirst.

8. A loud speaker comprising a casing, a

diaphragm extending across 1said casing, means for vibrating said dia hragm, and a second very thin diaphragm o japanned copper sheet stretched across said casing substantially parallel to and at a short distance from the rst.

9. A sound reproducer comprising an electromagnetic actuating mechanism, a diaphragm driven by said mechanism, a casing enclosing said mechanism and forming an annular support for said diaphragm, a resilient ring member concentrically positioned with respect to said annular support, a metallic foil sheet, and means on said casingpfor pressing said sheet against said resilient ring member and stretching said sheet in a plane parallel to the plane of said diaphragm for establishing a chamber between said diaphragm and sheet and-securing sound reproduction from both said diaphragm and sheet.

ln testimony whereof 1 have signed my name to this specification.

RICHARD FRENKEL.

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