Improvements in Microphones.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Microphones.
I. WILHELM DECKERT, of 34 Favoriten Strasse, Vienna IV, in the Empire of
Austria, machine maker, do hereby declare the nature of this invention, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
My invention relates to carbon microphones and consists in an improved construc-
tion of carbon blocks and arrangement of insulating brushes for said microphones.
On the sheet of drawings appended hereunto fig. 1 shows the microphone in section
on an enlarged scale.
Fig. 2, a front view, one half the mouthpiece removed.
Fig. 3, a back view.
The microphone consists mainly of the carbon block k and the thin carbon
membrane p placed opposite to the former. The block k is preferably made with a
circular section as shewn, but may also have a regular polygonal section. The face of
the block turned towards the membrane p is formed with crossing wedgeshaped
grooves c, whereby numerous pointed pyramids are formed; or similarly arranged
pointed cones may be formed on said face..
Each point carries a small brush i fixed to the point by an adhesive substance, the
brush being made of wool, cotton or silk fibres, or flax or hemp down. In putting
the microphone together, care is taken that the body k is close enough to the
membrane p for the elastic fibres of the brushes to touch the same without impeding
it in its vibrations. The grooves c of the body are filled with small particles of
carbon which in the vertical position of the microphone (fig. 1) effect a conducting
connection between the grooved surface of the body k and the inner surface of the
membrane p, the carbon block & presenting a large contact surface to said particles.
An elastic ring v formed of wool, cotton, or silk fibres, or flax or hemp down, and
lying in a circular groove in the case b, also bears against the membrane p which is
screwed fast to the case by means of the mouthpiece m made of wood, vulcanite,
metal or horn and the cloth or flannel masher t.
The ring as well as the brushes i prevent the carbon particles from becoming
locked or fixed between the body k and membrane p, whereby the elasticity of the
latter might be destroyed or a short-circuit produced. The ring v also receives the
carbon dust formed through a prolonged use of the microphone.
A principal
advantage of the elastic bearing of the ring and brushes against the membrane p
consists in the damping of the latter, whereby a loud, clear and true reproduction
of the voice is obtained.
The position of the carbon body k is regulated by the screw which is screwed
fast in the body and can be screwed in and out in the metal nutu. A spring pressing
against the back of the body k and the bottom of the recess in case b prevents
the loosening of the connected parts. Through an opening in the plate fa screw
driver can be inserted for turning the screw s. The latter may also be made long
enough to protrude through the plate and have a milled head, so that it can be
adjusted by hand.
From the contact spring g one wire of a double cable his led to the metal nut u ;
from the other wire of the cable is conducted to the membrane p as shewn
and indicated in figures 3 and 1. The metallic connection is made by means of
interposed copper wires.
The double cable h is flexible so as to allow the case to be turned by half a revolu-
tion. The arrangement for this purpose is shewn by fig. 3. Through the semicircular
slot a the back of the case is seen, into which the projecting stop screws and r¹ are
screwed. These screws prevent the case 6 with the microphone being turned for more

page_text: than a semicircle. The cable which enters the microphone through a hole between
the screws, and c, and participates in the turning of the case b. The object of turning
the microphone is to change the position of the carbon particles between k and p after
prolonged use and to obtain new points of contact. In turning the microphone a
quarter turn, the grooves c are brought into a vertical position, so that the carbon
particles can slide down in them and change their position. By turning for another
quarter turn, the grooves are brought again into an inclined position with other
surfaces of the pyramids at the top, and prevent the further downwards settling
of the carbon particles.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what 1
clain is, in carbon microphones,
-
Firstly, the carbon block k with numerous pointed projections arranged in zig-zag
rows substantially as hereinbefore described and illustrated and for the purpose of
preventing the downward settling of the carbon particles placed between said
projections.
Secondly, in combination with a carbon block formed as specified in the first claim
the arrangement of small elastic brushes for the purpose of insulating the points of
the carbon block from the membrane and obtaining a clear and distinct reproduction
of the voice, substantially as hereinbefore described and illustrated.
Dated this 13th day of July 1889.
EMMOTT & Co.,
Agents for the Applicant.