Improvements in Microphone Mechanism.
Year: 1892

page_text: Date of Application, 29th June, 1892
Complete Specification Left, 28th Apr., 1893-Accepted, 2nd June, 1893
PROVISIONAL SPECIFICATION.
Improvements in Microphone Mechanism.
I, CHARLES AMBROSE McEvoy, of 69 Victoria Street, in the City of
Westminster, Engineer, do hereby declare the nature of this invention to be as
follows:-
My improvements have mainly for their object to improve the construction of
microphone mechanism either to be submerged in the open sea or channels
wherever it is desired that notice should be given of any vessel passing near to the
spot where the mechanism is submerged or to give warning of the passage of
troops when used on land. I use a bell or casing open at the bottom but closed at
top. To the inside of the top of the casing I cause a light frame to be held up by
springs, this frame carries the flexible diaphragm and contacts of the microphone.
For the flexible diaphragm I use a disc of india rubber stretched across the lower
part of the frame and held to it all around its edge or the diaphragm might be of
thin hard material such as metal, wood or ebonite or other suitable material might
be used-the centre of the disc carries a small carbon block having a central hollow
on its upper face.
A second carbon block with a hole formed centrally through it is carried by a
bar which passes across the frame above the diaphragm.
A carbon or it might be a metal rod is passed down through the hole in the
upper carbon and its lower end allowed to rest in the hollow in the lower carbon.
The lower carbon is connected by a light conducting wire with the metal frame
and so to "earth" the upper carbon is connected with an insulated conducting
wire led away through the lower part of the outer case or bell to a telephone or
relay or other instrument at a distance.
The outer case is made of such a depth that the carbons remain surrounded by
air when the bell is submerged-preferably the bell is lowered until it rests on the
bottom.
The above construction forms a very sensitive microphone mechanism and can be
used for a variety of purposes. If desired the upper and lower blocks in place of
being of carbon might be of metal or faced with metal.
In some cases it is desirable to provide means for giving slight taps to the
diaphragm so that if for any reason the rod should get into a position in which the
microphone is not so sensitive as it should be it may be shaken from that position
into another in which it will act more efficiently. To do this I have a light rod
rising up from a small plate secured to the upper face of the diaphragm.
The bar which passes across the frame above the diaphragm I make to carry a
small electro magnet, and the armature of this magnet when attracted I cause to
strike against the upper end of this light rod and so to jerk the diaphragm.
For passing a current through the magnet coils whenever necessary I connect
one end of the coil to the outer metal case and so to earth and the other to an
insulated wire led away with the telephone wire.
Dated this 29th day of June 1892.

page_text: COMPLETE SPECIFICATION.
Improvements in Microphone Mechanism.
I, CHARLES AMBROSE MCEVOY, of 69 Victoria Street, in the City of
Westminster, Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement :-
My improvements have mainly for their object to improve the construction of
microphone mechanism either to be submerged in the open sea or channels wherever
it is desired that notice should be given of any vessel passing near to the spot
where the mechanism is submerged or to give warning of the passage of troops
when used on land. In some cases when the mechanism is to be submerged I use
a bell or casing open at the bottom but closed at top and secure the mechanisin to
the top of the bell on the inside.
The mechanism is composed of a rod or rods passed down through a hole or
holes in an upper fixed contact block or plate and resting at the bottom on a
second block or plate carried by a vibrating support.
The outer case may be made of such a depth that the contact blocks remain
surrounded by air when the bell is submerged or the sensitive vibrating mechanism
may be enclosed in a watertight casing of sufficient strength to withstand the
pressure to which it will have to be subjected.
One block is put in electrical connection with the bell-the other is coupled to
an insulated conductor led away to a battery and telephone or relay or other
instrument at the spot where warning is to be given.
In some cases it is desirable to provide means for giving slight taps to the
vibrating support which carries the lower block so that if for any reason the rod
should get into a position in which the microphone is not so sensitive as it should
be it may be shaken from that position into another in which it will act more
efficiently. To do this I have a light rod rising up from the vibrating support and
provide a small electromagnet the armature of which when attracted will strike
the top of the rod and so give a jerk to the support.
For passing a current through the magnet coils whenever necessary I connect
one end of the coil to the outer metal case and so to earth and the other to an
insulated wire led away with the telephone wire.
Figure 1 is a vertical section of my improved vibrating mechanism in the form
in which I prefer to construct it.
Another form of the vibrating mechanism is shewn in Figures 2, 3, 4 and 5.
Figure 2 is a vertical section of a heavy metallic bell which can be sunk and
which carries within it the vibrating mechanism.
Figure 3 is a vertical section on a larger scale of the vibrating mechanism.
Figure 4 is an elevation and Figure 5 a plan of the same.
H see Figure 2 is a bell heavily weighted around its rim, I is a casing con-
taining the vibrating mechanism. As before stated the bell may be either open
or closed at the bottom. If open it must be deep enough for the casing I to be
always surrounded with air enclosed in the bell unless the casing I be made
watertight and sufficiently strong to withstand the pressure to which it would be
subjected. The bell with the vibrating mechanism within it I have named a hydro-
phone. The casing rests upon springs H₁ these as shewn are made to surround
screw pins H and rest upon nuts screwed on to the screw pins-or the casing
might otherwise be secured within the upper part of the bell.
From the bottom of the casing (see Figure 3) a disc J of nonconducting material
is similarly supported on springs J¹ and above this a metal bar K rigidly secured
by metallic bolts K' to the bottom of the casing. K' is a carbon block secured to
the centre of the bar K and having a hole formed centrally through it. L is a
wire passed through the hole and also into a similar hole formed in a carbon block M

page_text: which is secured to the centre of the lower disc J. Preferably the bottom of the
wire is made to rest on a metal disc L' which is placed between the carbon block M
and disc J. A wire L' coming from one pole of the battery is coupled to this
disc L' and the battery circuit is completed through the wire L carbon block K'
metallic bar K and so to the metallic bell and through "earth" to the other pole
of the battery.
•
Any movement of the wire will vary the contact which it makes with the lower
disc and upper carbon block and so the amount of current passing through the
circuit will be varied by any vibration given to the mechanism.
N is a small electro magnet carried by the bar K. L' is an insulated wire led
through contact mechanism from one pole of a battery to an insulated coupling
connection carried by the bar and from thence through the coils of the electro
magnet to the bar K and so through "earth" to the other pole of the battery-
O is the magnet armature held away from the magnet poles by a light spring. When
the battery circuit is completed and the armature attracted by the magnet it strikes
against the end of a rod P which projects up from the disc J by completing the
battery circuit a slight jerk or tap can therefore at any time be given to the disc
should the wire L from any reason get into such a position that the mechanism
which acts in the manner of a microphone is not so sensitive as it should be the
wire can therefore be shaken from this position into some other position in which it
will act more efficiently. L' is a guard to keep the wire L from being jerked out
of the hole in the lower carbon block.
If the vibrating mechanism is to be placed under ground say for giving warning
of the passage of troops it may be carried as herein before described within a bell
and this bell may be similar to that used in the hydrophone but lighter or it may be
carried within any suitable casing not necessarily metallic if suitable provision is
made for readily completing an earth return or coupling to a return conductor.
The instrument when constructed for land use I call a geophone.
In the construction of vibrating mechanism shewn in Figure 1 I is a metal
casing, K a metal bar passing across it. K³ a metal block secured to the bar,
L are metal wires lying in holes bored through the block K' and resting at the
bottom on a flexible vibrating tongue J of thin spring metal which at one end is
secured to a block K³ of insulating material fixed on the underside of the bar K-
M is a strong spring stop carried by another block of insulating material fixed to
the bar K-it limits the extent to which the tongue J can vibrate and so prevents its
being crippled if it be subjected to too strong a jerk, R is a weight fixed on the
free end of the spring-S is a screw by which the height of the stop M can be
adjusted-T an insulated wire conveying current to the vibrating tongue-L' a
guard to prevent the rods from being jerked out of position.
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 I
claim is :-
1. Vibrating electrical contact mechanism consisting of a fixed upper block with
a hole or holes formed downwards through it, a rod or rods lying in these holes and
resting at the bottom on a lower block carried by a flexible vibrating support
substantially as described.
2: The combination of heavy metallic bell and vibrating contact mechanism
carried within it substantially as described.
3. The construction of vibrating electrical contact mechanism substantially as
described with reference to Figure 1.
4. The construction of vibrating electrical contact mechanism substantially as
described with reference to Figures 3, 4 and 5.
Dated this 29th day of March 1893.