An Apparatus for Notifying the Presence in the Air of Gases such. as Fire Damp.
Year: 1893

page_text: Date of Application, 11th Aug., 1893
Complete Specification Left, 11th May, 1894-Accepted, 11th Aug., 1894
PROVISIONAL SPECIFICATION.
An Apparatus for Notifying the Presence in the Air of Gases such.
as Fire Damp.
I, EDOUARD HARDY of Dreux in the Republic of France, Electrician, do
hereby declare the nature of this invention to be as follows :—
If two soniferous organ tubes having the same note when fed with ordinary air
are supplied with air or air and gas, of different density; that is to say, one with
pure air and the other with air mixed with some kind of gas, their vibrations and
tones will be dissimilar.
This is the principle of my invention.
To carry out my invention practically as for instance in a coal pit, liable to fire
damp, I station the instruments in different parts of the mine and connect them
electrically. In each apparatus I construct two bellows fed with currents of air
and operated by any suitable mechanical means. One bellows is supplied with pure
air from outside, the other with the air of the mine. The air from each passes
through a similar but distinct soniferous tube. Directly one bellows begins to
receive fire damp the vibrations of the tube it feeds and consequently the sound it
emits will vary from those of the other tube.
To automatically transmit a warning of this change to other parts of the
mine or to the surface, I add to the foregoing, telephonic instruments furnished
with microphones and transmitters, which I attach to the apparatus in such a way
that any variation from the pure air note is at once notified at any required distance
by means of electric wires acting on bells or other suitable signals.
A portable form of my apparatus can also be made. This will necessarily be
intermittent in its action, as the bellows must be operated from time to time by the
person carrying it.
Dated this 11th dew of A 19002
S. S. BROMHEAD,
97, Newgate Street, London, E.C., Agent for Applicant.
COMPLETE SPECIFICATION.
An Apparatus for Notifying the Presence in the Air of Gases such
as Fire Damp.
I EDOUARD HARDY of Dreux, in the Republic of France, Electrician, 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:-
When two organ pipes capable of emitting the same sound are actuated at the
same time by the aid of two different blast apparatus fed by pure air (the pipes
being tuned) one unique and pure sound is heard. On the other hand if one of
the blast apparatus instead of being supplied with pure air, is fed with a mixture
of air and another gas of different density for instance with fire-damp or carbonic-
acid, the number of vibrations of the organ pipe so treated is modified, and the two
pipes, sounding at the same time will produce more or less frequent beats as the

page_text: gaseous mixture is more or less rich in foreign gas. The number of beats produced
in a given time may be shown on a board or device indicating the quantity of
foreign gas contained in the gaseous mixture.
The organ pipe, sounding by pure air which is only destined to produce the same
number of vibrations may be replaced by any other source capable of emitting
known sounds or notes, for instance a tuning fork, but owing to the temperature
and the atmospheric pressure it is preferable to make use of an organ pipe.
What has been said with regard to air is likewise true for any other gas, and
what is said with regard to pure and foul air, applies likewise to any pure or
foul gas.
The above principle forms the basis of this gas mixture indicator.
The description of the apparatus is as follows: A lever A (Fig. 1) moved either
by hand or by other motive force actuates on the one hand the air bellows B for
supplying pure air and on the other the feed pump B¹ for supplying foul air.
When the bellows B open, the valve C will open likewise, the valve D remains
closed, the pure air contained in the air tight casing P passes through the tube E
and the valve C into the bellows B. When the bellows B close, the valve C closes
likewise, the valve D opens, pure air passes into the governor bellows, G, flows at
the same time through pipe F, makes the organ pipe J (Fig. 2) sound, and returns
into the air tight casing P by the tube E.
Owing to sufficiently rapid action of the lever A, pure air is introduced in excess
into the governing bellows G which open more and more, until the safety valve H
opens and establishes a convenient governing effect.
To avoid these differences of pressure due to the action of the bellows B it is.
preferable to set a caoutchouc pocket I, filled with pure air, in communication
with the air tight casing P, so as to regulate the pressure in said casing.
In order that the organ pipe J may be sounded purely and independently on such
small differences of pressure, as may result from the action of the safety valve H,
the air may be passed through any convenient blast regulator, which apparatus
being known, is not shown in the drawing.
In order that the organ pipe J may be always sounded with pure air, even if the
apparatus be plunged in a foul atmosphere, it is necessary that the feeding
bellows B, the communication pipes and the pocket I be made airtight, and that the
governor bellows G and the organ pipe J be contained in an air-tight casing P.
The pure air contained in this air-tight apparatus never leaves the same, it
being only set in circulation by the bellows B, so as to make the organ pipe J
Bound.
When the pump B' rises, it produces a vacuum above one or more purifiers K
(Fig. 3) by the tube L' and the valve C¹ the foul air (for instance of the mine)
taken in by the tube L having a rubber joint, gets rid of the dust and the carbonic
acid which it may contain, in this purifier K which is filled with water and an
alkaline solution. The carbonic acid may also be removed by purifiers analogous
to those used in gasworks. However those purifiers must be appropriate to the
gaseous mixtures to be analysed. When the pump B' falls, the air of the mine,
cleared from dust and carbonic acid, passes in the governor bellows G¹, flows at the
same time through the pipe F¹, sounds the organ pipe J' and thereupon passes off
freely in the atmosphere by the orifice M.
Owing to sufficiently rapid action of the lever A, the air of the mine arrives in
excess into the regulatory bellows G' which open more and more until the safety
valve H opens and establishes a convenient mode of governing.
A blast regulator may be arranged for removing the small irregularities in the
pressure originating from this safety valve H'.
The arrangement just described may be replaced by any other arrangement of
bellows, delivering a constant flow of pure air and foul air, the bellows for pure air
being air-tight as described hereinbefore.
A portion of the tubes F and F¹ (Fig. 2) is widened or expanded as at a, b,
and a, b and furnished inside with a series of partitions of fine metallic cloth.

page_text: These portions, a, b and a', b¹ are placed sideways each other in a receiver N filled
with water. The gases which arrive through these tubes F and F' pass through
these partitions of metallic cloth and take up the temperature. These gases it is
understood are reduced to the same temperature as those which make the organ
pipes J and J¹ sound.
In order that the sound produced by the organ pipe J enclosed in the air tight
casing P be transmitted with sufficient intensity it is necessary that this casing be
closed at a suitable place by a membrane O, it is good that the casing P¹ which
contains the organ pipe J' be likewise closed by a membrane O¹ although the
casing P' is not air-tight. These membranes may be of different substances, but it
is preferable that they may be made of metal. Their thickness and tension are
such that these membranes vibrate nearly in concert with the organ pipes J and J¹.
They thus vibrate strongly when the pipes are sounding. If the apparatus is
arranged in a noisy workshop, one may place above those membranes O and O¹ two
boxes or drums to be connected to the ear by means of two rubber tubes.
The beats are then heard with great intensity in spite of outside noise. If a
microphone be arranged upon each of the organ pipes and an electric current be
successively passed through these microphones, and thereupon conveyed to an
ordinary telephonic receiver, placed at any distance, this receiver will repeat the
exact sound of the pipes or as the case may be the beats, with absolute clearness.
The arrangement for hearing the beats only.
To attain this result, it is necessary that an electric current be passed in a
telephonic or other receiver only at each beat, when the vibrations of the two
organ pipes unite and produce their strongest sound, that is to say when the
membranes O and O¹ vibrate with the greatest intensity.
The arrangement for attaining this result may be any convenient one, for instance
a "Helmholz" resonator R (Fig. 4) is placed between the two membranes O and O¹,
and is closed at one side by a suitable membrane S.
When the organ pipes J and J¹ sound at the same time and produce beats, the
membrane S of the resonator R repeats the vibrations of each organ pipe and
reproduces the beats. The vibrations are alternately strong and slight ones.
A very light metallic style T rests on this membrane and participates in its
vibrations when said style alternately describes large and small oscillations. An
electric contact U touches this style only at its large oscillations when the electric
current, which passes through by this contact, is led through an ordinary telephonic
receiver or any other sufficiently perceptible receiver. This receiver, placed at
any distance from the apparatus, only sounds at the large vibrations of the
membrane of the resonator, that is to say, only at each beat; or a metallic style
may be provided also on each of the membranes O and O', in such a way that these
styles touch one another and produce an electric contact, when a coincidence takes
place between the vibrations of the membranes, whilst they do not touch each
other when the coincidence is broken up. As can be seen, this arrangement
likewise allows an electric contact at each beat to be obtained.
The device may be connected with a recording instrument, indicated in
Figs. 5 and 6.
A clockwork movement V causes a strip of paper W to unroll at a velocity of
about two millimeters per five minutes, when the automatic observations are wanted
to be recorded every five minutes. A registering hand or lever X, which always
starts from the zero point is arranged so as to move transversely on the strip of
paper W, leaving thereon a trace. The electric current, instead of arriving at the
receiver hereinbefore mentioned, passes through an electro-magnet Y which latter
actuates the recording lever and displaces it a small portion at each passage of the
current.
One of the moving parts Z of the clockwork establishes an electric contact
at Z¹ Z¹ every five minutes during several seconds for instance 30.
The electric current passes this contact Z' before arriving at the electro
magnet Y of the recording hand, which hand or lever it will be understood only

page_text: marks on said strip of paper those beats which have taken place during 30 seconds
in the whole space of time of five minutes.
The recording lever is then sent back to the zero point by any suitable
arrangement.
The recording, instead of being effected every five minutes may also take place,
Bay every minute, or at any desired interval of time, and may be made on a rotary
cylinder.
The recording apparatus may be placed at any distance apart from the apparatus
and be outside the mine.
The apparatus and recording instrument can be used to test the products from
flues or otherwise so that the indications thus afforded may be used as a guide in
the estimation of the quantity of air necessary for the combustion to be introduced
in furnaces, or for other purposes.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. An improved method and apparatus for analysing gases by the medium of
sonorous vibrations and beats for ascertaining the presence of gas of a different
density in the air and for guidance in or towards effecting any desired mixture of
the air and other gases, referring more particularly to the presence of fire damp
and carbonic acid, and in general to any gas occuring in combination with another
of different density.
2. The use of airtight bellows constructed to always take in pure air, and for
forcing the same into an airtight apparatus so as to sound an organ pipe placed
in said air-tight apparatus.
3. The use of two tubes partitionel by metallic cloth and placed one beside
the other into one and the same receiver, filled with water or other liquid, in
order to reduce the two gases to the same temperature.
4. The method for making audible the beats only.
5. The method explained for recording at given moments the quantity of
foreign gas existing in the gaseous mixture; "all substantially as and for the purpose
U
Dated this 11th day of May 1894.
R. HADDAN,
Of the Firm of Herbert Haddan & Co.,
18, Buckingham Street, Strand, London, W.C., Agent for the Applicant.