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   Patents 1921 - 1930



*U.S. Patent No. 1,637,119 , 07/26/1927 [DjVu119KB]
Electromagnetic Sound Reproducer
Kolster, Frederick A. and Sollie, Sigurd A. (assignee Federal Telegraph Company)
     One of the objects of the invention is to provide a practical construction of free edge sound reproducing diaphragm where-in mechanical vibrations may be imparted to the cone shaped sound reproducing diaphragm where the diaphragm is suspended intermediate the apex and peripheral edge thereof.

*U.S. Patent No. 1,693,401 , 11/27/1928 [DjVu77KB]
Telephone Circuits and apparatus
Nyman, Alexander and Conrad, Frank (assignee Westinghouse Electric and Manufacturing Company)

     Our invention relates to telephone systems and apparatus and particularly to sound translating apparatus employing vibratory elements.

     The principal object Of our invention is to provide circuits and apparatus of such nature as to admit of the elimination or substantial reduction of the undesirable resonance effects common to apparatus of the above-mentioned type.

*U.S. Patent No. 1,761,100 , 06/03/1930 (app. 01/23/1928) [DjVu55KB]
Baldwin, Nathaniel
Abstract: The present invention appertains to acoustic diaphragms and particularly to that class in which large diaphragms are used without horns for loud speakers. The principal object of the invention is to produce a diaphragm which is extremely light, delicate, and sensitive and yet forcefully responsive throughout to the impulses communicated to it.

*U.S. Patent No. 1,730,528 , 10/08/1929 (app. 02/28/1927) [DjVu126KB]
ACOUSTIC TRANSFORMER (class: 369/156; 181/163; 181/400)
Robbins, Percy A.
Abstract: One object of my invention is to provide a means whereby the area, and therefore the thickness, and therefore the weight of the diaphragm may be reduced.
   When a sound wave is propagated through air at atmospheric conditions, it impinges upon a diaphragm with a certain velocity of its particles due to their amplitude of vibration. The inertia of the diaphragm is so great that during acceleration a certain number of air particles rebound without having imparted their full store of energy to the diaphragm, and not until the diaphragm has acquired a velocity equal to one-half of the velocity of the air particles is there a full absorption of the energy of the sound wave. During retardation, the inertia of the diaphragm carries it too far ahead and it therefore fails to receive the energy of certain air particles.
   Thus a considerable dissipation of energy occurs at the surface of the diaphragm, and the velocity of motion imparted to the diaphragm is much less than the velocity of the air particles.
   When vibrations are emitted by the diaphragm and absorbed by the air particles, the converse is true. The diaphragm compresses an air wave at its surface owing to the elasticity of the air, and this air wave, owing to the energy stored in it, springs from the diaphragm with a greater amplitude of vibration than that of the diaphragm. Owing to the slight resistance opposed to the diaphragm by the air it is not possible to impart all of the energy of the diaphragm to the air and much of this energy is dissipated in doing internal work upon the substance of which the diaphragm is composed.
   If a medium be opposed to the action the diaphragm, which medium is capable of absorbing a greater amount of the energy stored in the vibrations of the diaphragm, then in order to produce a desired effect a less violent vibration of the diaphragm will produce the desired effect.
   A second object of my invention is to provide such a medium.

*U.S. Patent No. 1,730,531 , 10/08/1929 (app. 11/30/1928) [DjVu97KB]
Acoustic Transformer (class: 381/166; 381/186)
Robbins, Percy A.
Abstract: ”Loudness” of tone depends upon the amplitude of vibrations at the ear of the listener, and the loudness of tone emitted by a diaphragm depends upon the number of air particles acted upon by the diaphragm and the degree of violence with which the air particles are vibrated. Loudness may therefore be increased by increasing the area of the diaphragm and maintaining a fixed amplitude of vibration: by retaining a fixed area but increasing the amplitude of vibration: by crowding a greater number of air particles into contact with the diaphragm: or by providing a gas heavier than air to receive the vibrations from the diaphragm.

*U.S. Patent No. 1,730,532 , 10/08/1929 (app. 11/30/1928) [DjVu48KB]
Acoustic Transformer (class: 181/153; 181/157)
Robbins, Percy A.
Abstract: This present invention relates to a special form of the invention disclosed in my co-pending application No. 322,897 of even date herewith. In that application there is disclosed a closed chanber containing a gaseous medium having a greater power-transmitting capacity than air at atmospheric pressure in which chamber is totally immersed a vibratable diaphragm from which or to which vibrations pass solely through the gaseous medium to or from a second diaphragm exposed at one side to the atmosphere and at the other side to the pressure within the chamber.
   My object in the present invention is to provide a simple form of the invention which is cheaply and easily made, and which gives a miximum area to the second diaphragm obtainable within given over all dimensions of the apparatus.
   I attain my object by reducing the rigid part of the chamber to such dimensions as suffice only for the connection and support of the parts, and by utilizing, to complete the chamber and form the diaphragm, a substantially spherical shell formed of a flexible elastic material such as thin rubber.

*U.S. Patent No. 1,748,407 , 02/25/1930 (app. 07/18/1927) [DjVu172KB]
Loud-Speaker Unit (class: 335/231; 335/274; 381/417)
Bottorff, Charles A. (assignee: Trimm Radio Manufacturing Co.)
Abstract: The invention relates to improvements in loud speaker units. It is of particular value in connection with loud speakers of the "cone" type, although the construction may be employed in other types of telephones, the term "telephone" being used to include any electrical device designed to transform electrical current impulses or waves into sound.
   The object of the invention is to provide a telephone unit of high efficiency, simple design, economical construction, quick accessibility, great durability, capable of being assembled cheaply, rapidly, and having the ability to withstand hard service.


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