US1604788A - Means for supporting the diaphragm of a telephone transmitter or receiver - Google Patents

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Oct. 26 1926. 1,604,788

H. J. ROUND MEANS FOR SUPPORTING THE DIAPHRAGM OF A TELEPHONE TRANSMITTER 0R RECEIVER Filed July 18, 1924 HENRY JOSEPH RWNO INVENTOR 'ITORNEY Patented Oct. 26, 1926.

UNITED STATES PATENT OFFICE.

HENRY JOSEPH BOUND, OF LONDON, ENGLAND, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE.

MEANS FOR surronrme THE DIAPHRAGM or A TELEPHONE TRANSMITTER on RECEIVER.

Application filed July 18, 1924, Serial No. 726,693, and in Great Britain-July 25 1923.

One of the difiiculties in obtaining a really accurate reproduction of sound is the difliculty in obtaining an aperiodic dia phragm.

If it were possible to employ a diaphragm of infinite extent and sound were allowed to impinge only upon a small area thereof, the diaphragm would be perfectly aperiodic because there would be no reflection from the edges of the diaphragm.

If again the material of which a diaphragm of limited area is constructed be self damping, then assuming't-hat the self damping is suflicient for all wavelengths,

1 any wave force applied to the centre will be absorbed before it reaches the edge and again the result will be that there will be no resonance.

In order to obtain or approximate to such result with a diaphragm formed of a material such as ebonite or steel which will not absorb all the ener'y due to a sound wave before it has traveled from the centre to the edge andback again, I so support a diaphragm that a slight damping is applied to the whole surface except at one part which is exposed to the air. referably the damping is graduahotherwise reflection may occur at the place where an abrupt change of damping occurs. For instance, I may support a large flat circular diaphragm in wool, felt or the like, leaving only a small area at thecentre not so supported, the wool or the like being itself supported in a casing of wood or metal. At thecentre of the diaphragm may be attached a coilenclosed in a magnetic field for setting the diaphragm in vibration or for producing E. M. F. when the diaphragm is set in vibration by sound waves.

In the case of-a strip diaphragm a portion of the strip may be left exposed to the air while the remainder is insulated from the sound waves and immersed in a damping medium such as cotton wool or felt or even a magnetic field. p

Again, I may employ a diaphragm which is not fiat.

In general the total area of the diaphragm must be large compared with the area exposed to the air in order that the damping edge shall not be abrupt and the total damping shall be suflicient. p

My invent-ion is illustrated by the accompanying drawing, which shows a large flat circular diaphragm A supported in cotton wool B contained in a sound insulator 1 formed of a wooden box C; The middle of the diaphragm is exposed to the air and carries a coil D in the field of'a magnet E. A horn F is provided in the side of the box C ppposite to the middle of the diaphragm.

aving described my invention what I claim is i 1. In a telephone transmitter or receiver, 55 a diaphragm of which only a small portion is exposed to the air and which is so supported between layers of fibrous material, whereby the reflection of vibrations is practically eliminated, substantially as described. I

2. In a tele hone transmitter or receiver, an aperiodic iaphragm consisting of a vibratory body and -'a fibrous body covering only a portion of each face thereof. I

3. In a-telephone transmitter or. receiver having a diaphragm, means to support said diaphragm foraperiodic. vibration, said means comprising a body of fibrous material covering a portion only of the diaphragm. i

4. n a telephone transmitter or receiver,

a diaphragm adapted to vibrate tin, accordance with audible impulses, and means supporting said diaphragm to. prevent resonant 5 vibration thereof, said means being associated with a portion only of both sides of said diaphragm.

HENRY JosErHRoUNDo

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