I■- PROVEMENTS IN SAFETY LAMPS
Year: 1875

page_text: LETTERS PATENT. to Edmund Edwards, of the Firm of Edwards and
Co., 38, Southampton Buildings, Chancery Lane, in the County of
Middlesex, Engineers and Patent Agents, for the Invention of “I■-
PROVEMENTS IN SAFETY LAMPS." -A communication from abroad by

page_text: the same, and have made solemn Declaration that the said Invention
has been communicated to me from abroad by Alfred Bernard Boullenot,
the elder. of Paris, France.
NOW KNOW YE, that I, the said Edmund Edwards, do hereby declare
that the following Complete Specification, under my hand and seal, fully
describes and ascertains the nature of the said Invention, and in what
manner the same is to be performed, in and by the following state-
ment and accompanying Drawing (that is to say):-
But
This improved safety lamp is intended to revolutionize the ordinary
system of lighting mines. This ordinary system which for simple
candles of tallow. lamps of iron or copper, or even flint wheels in mines
producing gas has substituted with advantage since the month of
January 1816 the wire gauze lamps of the celebrated English chemist
Sir Humphrey Davy, constitutes a real step in advance for the security
of the lives of miners although giving but a bad light.
however ingenious the Davy lamp may be, based as it is upon an
important observation made by him during his experiments upon fire-
damp (which is only a combination of hydrogen and of carbon in the
proportion of four parts by weight of the former, and eleven and half
parts of the latter), it is but a small progressive step in advance and does
not completely solve the question. Many frightful accidents from 1816
to the present time only shew this foo plainly.
Davy's observation was the following:-" That metallic gauze composed
of wires of from 0.0007 metres to 0.0019 metres in diameter, and con-
taining 28 wires or 784 openings to 27 millimetres gives absolute
security in an explosive mixture inasmuch as though the flame of the
lamp is increased in length on the lamp being plunged into the gas, yet
that the latter when inflamed cannot pass the gauze on account of the
rapid cooling caused by the metal wires, and consequently cannot fire
the gas outside. The lamp became extinguished directly the carbonic
hydrogen gas formed a third part of the volume of the atmospheric air,
and it was necessary to remedy this serious inconvenience by a fabric of
numerous platinum wires of a diameter of about 0.0003 metres. To
meet successfully these difficulties M. Alfred Bernard Boullenot the
elder, long a Member of the Societé des Agriculteurs de France.
(Section du genie rural), has invented a system of permanent lighting
radically different from the former system, perfected as above described
by the Invention of the Davy lamp.

page_text: The Inventor considers that it is necessary to adopt one or other of the
following views:-Either to supply the lamps freely with the sur-
rounding air where the gas is constantly present, or to supply the lamp
of the kind invented by him with external air and consequently pure
and free from gas.
It is obvious that the system which avoids the gas altogether is that
which should be adopted, the lives of the workmen being at stake, and
it is then a matter of indifference even as to what proportion of coal gas
mixed with air becomes explosive, the improved lamp herein-after
described being entirely independent of these conditions and dangers.
That the air of a mine becomes explosive when containing one-twelfth
or one-thirteenth of hydrocarbon gas (which the miners perceive by the
smell, a more significant indication than that of the elongated flame in
the Davy lamp) is of little consequence where the improved lamp is
used, since the latter can never become filled with dangerous gas like the
Davy lamp, and consequently will never be extinguished so long as the
supply of oil lasts.
The following is a description of the Invention:-A pipe of a size
calculated to furnish air to the requisite number of the improved lamps
is brought from a reservoir or air receiver, fixed outside the mine near
the principal pit and the steam engine. This reservoir is filled with air
compressed to the requisite pressure by means of a lever or other
suitable apparatus driven by the steam engine, and working a pump
which forces the air into the receiver and thence into the fixed main air
pipe, a pressure gauge being provided to indicate the pressure. This
fixed pipe may be of wrought or cast iron, copper, lead, or other suitable
material, and is carried down the principal pit and if necessary down the
other pits, whence it is conducted by means of branches through the
whole mine, the several parts of the pipe being connected together by
suitable couplings. At distances calculated for the good and sufficient
lighting of the mine nozzles are provided, each one furnished with a
stop-cock for closing and regulating the supply of air to the lamps which
are screwed to the nozzles.
•
The following is a description of the improved lamps to be used for
this purpose, and which are easily constructed and arranged. Each
lamp is cylindrical in plan for about half its height, and may be made of
sheet iron, zinc, or other suitable metal, and contains first, the air,

page_text: chamber; second, the oil vessel containing sixty-five grammes of linseed
or nut oil, this being a sufficient quantity for one shift. This oil rises to
the wick by capillary attraction assisted by the pressure of the air upon
it, and if it happens that the oil overflows at the wick from too great
pressure it falls back into the vessel from which it proceeded; third,
round the oil vessel are pierced numerous small holes to direct upon the
wick the oxygen of the air which is continually being renewed. The
wick may be either flat or round and a small wheel or analogous con-
trivance moved by an exterior knob attached to the bottom of the lamp
by a chain allows the wick to be raised or lowered in the usual way as
desired. The stem of the knob fits into a square conical orifice in the
end of the axis of the small wheel above mentioned. The knob and
stem can thus be drawn back when it is desired to withdraw the oil
vessel from the lamp outside the mine, for the purpose of cleaning it or
of renewing the oil or wick. The oil vessel instead of having a flat or
round burner may have an argand burner. In this case the air will pass
from the air chamber through and round the wick. It will be under-
stood that the light in this case will be brighter and better, but the
consumption of oil and air will be greater.
Where the metal of the lower part of the lamp ends a cylindrical glass
or crystal begins about 3 millimetres thick, and about 18 centimetres
high. This glass or crystal is cemented at its lower edge so that it
practically is in one piece with the bottom of the lamp. The glass
or crystal is surmounted by a cover formed of a ring of copper or other
metal supporting two pieces of cap-shaped wire gauze, leaving between
them a space of about 1 centimetre. This cover fits the cylinder of
crystal or glass and can easily be removed when outside the mine. In
the centre of the cover is formed a circular opening about half
centimetre in diameter, of which the lower part terminates in a truncated
cone, usually closed by a stopper attached to a chain fixed to the copper
or other ring of the cover. This opening serves to introduce the appa-
ratus for lighting the lamp as herein-after described. A protecting cage
formed of neat iron bars serves to protect the crystal or glass in the same
way as in some forms of the Davy lamp, and this cage is supported at
the bottom on a metal bracket or ledge at the foot of the lamp, where
the glass or crystal is cemented to it. Finally a reflector which can be
turned as desired round the outside of the lower part of the lamp, and
rises to about half the height of the glass or crystal cylinder is placed so
as to direct most of the rays of light to any desired point.

page_text: The accompanying Drawing is in illustration of the Invention and
represents a lamp full size. In the several Figures the game letters of
reference indicate the same parts.
Figure 1 is a vertical section of one of the improved lamps fitted upon
the pipe through which the air is supplied; Figure 2 is a horizontal
section of the same.
The lamp is composed of the following parts:- is the air chamber in
sheet iron, copper, zinc, or other suitable material; g is the transparent
cylinder of glass or crystal which is fixed hermetically or cemented to
the top of the air chamber a, and is supported and protected by the bars
h, h; c is the oil vessel furnished with wick and regulator, and supported*
in the upper part of the air chamber a by three or more supports e, e, e,
resting upon the plate which forms part of the chamber a. The wick
& may be flat, as shewn in Figures 1, 2, 3, and 4, or tubular, as shewn in-
Figures 5 and 6. A metal wire e' serves to remove and replace the
vessel c without its being necessary to detach the glass cylinder. The
wire stem by which with the knob and wheel shewn at u, u, uª, the
wick is raised or lowered, is made in two pieces, so that when it is
required to withdraw the reservoir c, the part u, is drawn back until the
stop u comes against the projection a. By means of the inclined
guide e" the oil vessel c is always made to occupy the same position, so
that the square end of the part of the wire stem u" may always enter
the hollow square end of the other part u'; i is a cover which fits
exactly over the top of the tube or cylinder g. This cover is fitted with
two or more woven metallic wire gauzes which cover the whole of
the upper end of the transparent cylinder with the exception of a small
hole j, which can be closed by the metal stopper j¹. Finally a reflector
k carried by means of the supports upon a moveable ring k³ is
arranged, so that the light may be reflected in any required direction.
The chamber a receives its necessary air from a general supply pipe a"
by the intervention of an elbow pipe or nozzle a', or by a straight pipe
or nozzle a¹. Whether this pipe be straight or bent it is furnished with
a screw coupling b which may be readily connected or disconnected, and
with a stop-cock b' which closes the pipe more or less so as to regulate
the inflow of the air.
Figures 7, 8, 9, 10, and 11, shew on an enlarged scale so that the
more important details may be better understood a long tube or metallic.
sheath small enough to be passed through the hole j. This sheath
'

page_text: encloses a spring clip m which grasps and retains an ordinary lucifer
match, which can be withdrawn into the interior of the tube by a
ring o to which is fixed the clip m.
The lighting of the lamp is accomplished as follows:-The lamp being
furnished with a wick supplied with oil and screwed upon its air pipe a',
the long tube provided with its match as shewn in Figure 7, is intro-
duced through the hole j. The match can be rubbed upon the rough
surface p which is arranged for the purpose. The air cock 6' is opened,
the match is struck by a circular movement upon the rough surface, and
when it is lighted it is moved towards the wick of the lamp, and when
the latter is also lighted before withdrawing the tube from the lamp,
the ring o which is worked from the outside is raised and draws with it
the clip, causing the light to re-enter its tube as shewn in Figure 8, and
it is immediately extinguished. The tube may then be safely with-
drawn from the lamp, the stopper j¹ is replaced in the hole j, and the
lamp is then in proper order for work without any direct communication
with the surrounding air. The miner will never have to touch the
lamps, a special attendant being charged with this duty.
•
The following advantages are obtained by this system of permanent
lighting. There will no longer be any fear of the lamp becoming
extinguished since in the first place, the firedamp will not enter it;
secondly, the carbonic acid expelled by the hot air will escape through
the wire gauzes of the cover, and will drive away the gas which is
present above and round the latter; third, the flame will be completely
protected from currents of air, an advantage which Davy could only
obtain in his safety lamp by means of a screen which only effected the
object very imperfectly and on one side; fourth, there will be no longer
any fear of carbonic oxide. The lamps will be cleaned outside the mine
into which they will be sent completely prepared, that is to say, supplied
with oil and wick, and they will be screwed upon the nozzles of the
fixed air supply pipe either vertically at suitable distances apart or
horizontally.
In order to clean the lamp, first, the cage which protects the glass or
crystal is removed; secondly, the cover; thirdly, the rectangular iron
wire which is rivetted to the oil vessel is taken hold of by a hook, and so
the vessel is removed from the glass cylinder, the knob by which the
wick is raised or lowered being first withdrawn and being returned to its

page_text: position when the oil vessel has been replaced filled with oil. The
miners will have their movements in no way inconvenienced when at
work, since they will only have to use their tools whilst every part to
which they penetrate will be lighted like the streets of a town at night.
As a gallery or level is extended an additional length of the fixed air
supply pipe is added, and one or more lamps screwed upon it.
The Inventor considers the use of flexible tubes (gutta percha or other
vegetable material), both dangerous and impracticable in the damp and
variable atmosphere and temperature of mines, and he therefore
confines himself to the use of rigid pipes of wrought or cast iron,
copper, or lead.
In exceptional cases where a miner may require a self-supplying lamp
separated from the fixed air supply pipe, the safety lamp as above
described may be screwed upon a sphere in the same way as it wäs
screwed to the fixed air supply pipe as above described, and this sphere
may be filled outside the mine with compressed air or oxygen, and the
lamp may also be lighted there. A conical valve or spring should be
fixed upon the cover which carries the wire gauze.
In order to utilize and adapt to his system the numerous existing
Davy lamps, the Inventor has only to make a slight modification in
these lamps which it is proposed by his system to abolish, as both giving
little light and a security far from complete.
Finally he claims considerable economy when working in the midst of
dangerous gases as compared with the ordinary methods.
In witness whereof, I, the said Edmund Edwards, have hereunto
set my hand and seal, this Eighth day of January, in the year
of our Lord One thousand eight hundred and seventy-five.