US1745686A - Mounting for phonic diaphragms - Google Patents

Description

Feb. 4, 1930. c. R. MOORE MOUNTING FOR FHONIC DIAPHRAGMS Original Filed June 15, 1923 Mme/#0 fl/mr/a; A? Maare, fi W a zm my Patented Feb. 4, 193o.

UNITED STATES PATENT, OFFICE i CHARLES R. MOORE, OF MAPLEW'OOD, JERSEY, ASSIGNOR TO WESTERN ELECTRIC GOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK MOUNTING FOR PHONIG DIAPHRAGMS Application filed June 15,

This invention relates to large direct acting diaphragms and more part1cularly to means for mounting them.

With particular reference to large direct acting phonic diaphragms, it has been proposed to mount such diaphragms by means of rings which clamp the periphery of the diaphragm. The diaphragm thus mounted v1- brates in a manner analogous to a closed pipe, and the lowest prominent natural frequency thereof is higher than in the case of another arrangement which has been previously used, that is, a diaphragm mounting which per mits the periphery to vibrate freely. The latter diaphragm vibrates in a manner analogous to an open pipe and reproduces low notes better than the diaphragm with the clamped periphery. In the case of either the clamped periphery or the free perlphery, there is more or less reflection at the periphery which prevents the quality of transm1ssion from being as good as is the case with the present invention and according to which the periphery is damped in its vibratlon, the amount of the damping preferably automatr cally increasing with the increased vibration of the diaphragm. 1 i

Such a damping means may conveniently take the form of so-called book damplng which comprises a loose stack of sheets of paper or'the like, the spacing factor, for 1nstance, being fifty per cent.

The mode of operation of this damping means will be made clear by considering the following analogy. If a stone is dropped into a pond of water, waves will proceed to the shore and will be reflected from the shore, the reflected waves interfering with the initial waves. A somewhat similar interference occurs in the case of the diaphragm having either a clamped or a free periphery.

If, however, we consider the action of the initial waves at a shore which is closely set with grass or weeds, it is seen that the initial waves will be absorbed at the shore and that there will be no reflection to cause interference.

192-3. Serial No. 645,615.

the last mentioned shore which prevents reflection. Y

For further details of the invention, ref erence may be made to the drawing wherein is shown an elevation partly in cross-section of a diaphragm mounting as applied to a transmitter. v

Referring to the drawing, the diaphragm 1 is illustrated as a large direct acting conical diaphragm which may be of paper or other light and stiff material and which may be of the order of six inches or more in diameter, and if six inches in diameter, may be about two inches high. The periphery of this diaphragm is supported between loosely packed sheets of paper 2 confined in the space between clamping rings 3 and 4 suitably held together by means such as bolts 5- Due to this looseness in packing, a plurality of cushioning air films will be presentbetween said sheets of paper or other suitable material. To the ring 4 is clamped, by means of bolts 6, a ring 7 which supports the stationary elements of a carbon button transmitter, of any suitable type, the movable element of the transmitter having fastened thereto a rod 8 which is riveted or otherwise fastened to the diaphragm 1 at its center 9.

For small vibrations in the diaphragm, damping at the periphery will be small due to the limited motion of the periphery between the loosely packed sheets of paper. Itwill be apparent that as the vibration of the diaphragm increases, the effectiveness of the peripheral damping will increase also. As the frequency of the drive increases the stiffness factor, that is, the elasticity of the diaphragm support at the edge, increases also. The result of this is to raise any apparent natural frequency the diaphragm may have. 90

WVhile the invention has been shown as applied to a conical diaphragm, it is not necessary that the diaphragm should have this form. Furthermore, the diaphragm may be used for loud speaking receivers, as well as for transmitters.

What is claimed is:

1. A lar e direct-acting diaphragm, a support there or, and a plurality of thin sheets of light material stacked loosely to provide 100 a multiplicity of air films interposed between said support and the peripheral margin of said diaphragm.

2. A cone-shaped diaphragm, a rigid support about the periphery an out of contact with the sides said diaphragm, and loosely disposed light material between said support and the peripheral margin of said diaphragm. m '3. A large direct-acting diaphragm, a rigid support for said diaphragm, and yielding means comprising a plurality of layers of loosely disposed material between said support and the peripheral margin of said dia- 4. In combination a direct acting diaphragm, a support for said diaphragm and means comprising a plurality of layers of paper on both sides of the periphery thereof,

between said support and the diaphragm,

for effectively reducing reflection of-vibrations from the periphery along the dia- 5. e combination with a large directee acting diaphragm having a configuration to impart to it inherent stiffness from the center outwardly, of a rigid support about the edge portion and out of contact with the sides of said diaphragm, and yielding material into terposed between said support and the edge portion of the diaphragm for permitting limited vibration of the edge portion thereof. 6. A diaphragm exposed on at least one side to the free air composed .of a sheet-like material of uniform thickness and so shaped as to impart stiffness to it, a rigid support, a yielding material at the rim portion of said diaphragm between the rim of said diaphragm and said support, said diaphragm eing free from restraint with respect to axial movement except for the resistance offered by said yielding material.

7. A lar%e direct acting conical diaphragm having a ange portion, a channel shaped as support for said diaphragm, and loosely disposed material on both sides of said diaphragm at its flange portion between said diaphragm and said support, said diaphragm being free to move axially except for the re- Slilfilllt offered by said loosely disposed mater1 In witness whereof, I hereunto subscribe my name this 7th day of June, A. D. 1923.

= LES RPMOORE.

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