IMPROVEMENTS IN SAFETY LAMPS FOR USE IN MINES AND SUCH LIKE PLACES
Year: 1884

page_text: WO WILLIAM GEORGE THRESHER of South Street Wilton and HORACE JOIN
LLOYD FAREBROTHER of the City of Salisbury Gentleman both in the County of
Wilts do hereby declare the nature of our invention for IMPROVEMENTS IN SAFETY
LAMPS FOR USE IN MINES AND SUCH LIKE PLACES to be as follows:-
The object of the improvements is to obviate the danger which arises from
miners' safety lamps when exposed to a current of explosive gas becoming so
heated as eventually to cause an explosion or ignition of the gas.
This object Wo attain by so arranging the parts of the safety lamp, that upon the
gas of an explosive nature entering the lamp, the light therein is extinguished
mechanically and all danger of the lamp becoming incandescent and exploding the
surrounding gases is avoided.
For this purpose We take advantage of the law of diffusion of gases which
obtains in respect of marsh gas and atmospheric air whereby their relative diffusion
into a chamber through a porous division or diaphragm is unequal in rate.
The rates of diffusion may be taken for our purpose to be as follows 132 inches
of Marsh gas will in a certain interval diffuse into a given porous chamber (in say
a Miners lamp) whereas in the same interval 100 cubic inches of air only would
diffuse out so that an excess of pressure takes place inside tho porous chamber, or
chamber covered at its open parts by porous material, and we employ this natural
property in the operation of our improved safety lamp by providing such a porous
part through which any explosive gas as marsh gas diffuses into a chamber and
this chamber has a part of it formed open, except that it is covered by an
expansible meinbrane, or s' cet, capable of distention by the gas of greater diffusion,
on its power being exerted in that chamber.
This expansion and distension of the membrane, or flexible cover operates a part
or lever suitably centred, or connected that it may through the intervention of an
intermediary sliding, or rocking pieco, cause the flame of the Safety lamp to be
extinguished, or it (the said diffusiometer) may act directly.
This extinguishing of the lamp will take place before any dangerous admixture
of gases within the lamp can take place. And to prevent the miner working
with a naked fiume, or from tampering with the flame in any way, a detent is
released immediately the gauze is attempted to be removed which detent releasing
a spring actuates the extinguisher and thus puts out the light.
Dated this 10th day of January 1884.
WILLIAM BROOKES,
Avent.

page_text: We WILLIAM GEORGE THRESHER of Wilton in the County of Wilts Schoolmaster
and HORACE JOHN LLOYD FAREBROTHER of Salisbury in the County of Wilts
Dental Surgeon do hereby declare the nature of our invention for IMPROVEMENTS
IN SAFETY LAMPS FOR USE IN MINES AND SUCH LIKE PLACES, and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
The object of this Invention is. To increase the Safety of the lamps used in
mines and such like places. This wo propose to do by means which cause the flame
of the lamp to te automatically extinguished before sufficient explosive gas can
accumulato to cause an explosion: for this purpose We take advantage of tho
principle known in Chemistry as the "diffusion of Gases" By the laws of this
principle if two Gases of different densities be separated from each other by a
porous diaphragm they have a tendency to flow together through the diaphragın
until a complete admixture of the two Gurs has taken place. The Rates however
at which the Gases pass through the Diaphragm is not the same for the lighter of
the two passes through much more quickly than the heavier or denser and their
rates of diffusion have been found to be inversely as the square root of their
density. In regard to ordinary atinospheric air and Marsh Gas the Marsh Cas
diffuses through the diaphragm 1-3375 times more quickly than the atmospheric
air and thus causes an increase of pressure on the chamber containing such air.
To take advantage of this principle and to cause by means thereof an extinction
of the flame in the lamp a chamber having a thin plate of unglazed porcelain for
one of its sides is fixed to the reservoir of the lamp and this chamber has an
opening covered with a piece of india-rubber or expansible membrane capable of
being distended by pressure from the inside of the chamber. This india-rubber or
membrane in the act of distension presses against and moves a crank or lever
passing through the collars which hold the reservoir and the glasses together and
the motion of this crank or lever pushes a sliding cap over the flame and at once
extinguishes it. To enable the glasses to be removed from the reservoir this crank
is made in two paris viz: An inner part working like a screw on the inside collar
and an outside part touching the distension part of the diffusion chamber. The
inner half has its end squared and the outer half fits on it like a clock key and is
held in position by a small spring.
The saine result can be attained by slightly lengthening the collar on which the
glasses are screwed and by passing the crank under the outside collar through the
inside one.
To prevent the miner exposing the flame by opening the lamp an horizontal
opening is made in the inside collar and a small block of metal is pivoted on this
opening so as to swing horizontally. On the outside a short spring is fixed and on
the inside a stem (terminating in a flat piece) just long enough to reach to the
wick holler.
When the glasses are being screwed on to the reservoir the spring is pressed
down close to the block and offers no resistance but when the collar is screwed
right on, the spring opens, the end then falls into a notch in the outside collar and
on an attempt being made to unscrew the glasses this block is moved round
carrying the llat end of the stem over the flame and extinguishes it before the lamp
can be opened.

page_text: To prevent the glasses cracking by direct contact with the flame as when the
lamp is tipped or falls over a weighted piece of brass slides horizontally in guides
round the wickholder.
This piece of brass has a slot in it the width of the wickholder, and the slot is
bent upwards at right angles and again being bent terminates in a flat piece.
When therefore the lamp falls over, the piece of brass slides through the guides and
covers the flame, being obliged to do this by the force of gravity, which acts on the
weighted end and brings it to the lowest possible point while the flat piece being
at the other end of the slot is bound to follow the movement of the weight and to
cover the flame.
The construction of the lamp to prevent currents drawing the flame through the
gauze is as follows-
To the reservoir two cylinders of glass secured in grooves, in brass plates at top
and bottom are screwed. The air passes in through holes covered with fine gauze
in the top plate and downwards through similarly covered holes in the bottom
plate to the flame. The heated air from the flame passes upward through
four gauzes, fixed at intervals in a brass chimney screwed to outside of the
top plate.
The plates holding the glasses are held together by stays which passing through
both plates are brought up over the chimney to allow of the lamp being held or
carried.
Figure 1. Section
A
B
The reservoir of the lamp.
The external Glass shield.
с
F2
G
The internal Class shield.
The diffusion chamber.
Distension part covered with membrane.
Crank set in motion by distension of membrane.
Sliding cap.
Extinguisher to prevent glasses cracking.
1.23.4 Gauzes to protect flame.

page_text: we claim is the Automatic Extinction of a Safety Lamp before an explosion can
take place by means of apparatus fixed in a suitable position on a Safety Lamp
and also the rendering it impossible for the Miner to cause an explosion by
uncovering the flame.
Tati 10th of October 1881