AN IMPROVED ANTI-EXPLOSIVE OR SAFETY LAMP APPLICABLE FOR MINING AND GENERAL PURPOSES
Year: 1869

page_text: LETTERS PATENT 1o. Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
AN IMPROVED ANTI-EXPLOSIVE OR SAFETY LAMP APPLICABLE FOR MINING
AND GENERAL PURPOSES Communication from abroad by Nicolas
Tous Beaufils and Jacques Rexroth, both of Paris, in the Empire
A
PROVISIONAL SPECIFICATION left by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 23rd June 1869.
1,
, NLEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agents do hereby declare the nature of the
said Invention for "AN IMPROVED ANTI-EXPLOSIVE OR SAFETY LAMP APPLICABLE
FOR MINING AND GENERAL PURPOSES, to be as follows:-
Thisvention consists, firstly, in applying to any description of lamps
lighted by oil, schist petroleum, or any other illuminating substance an
0 arrangement for allowing the said lamp to burn safe from explosion
Price 6.1

page_text: when used in foul air or inflammable gases, such as are found in coal
mines, and also in public or private establishments through gas escapes.
Secondly. In the use and application of a novel arrangement for
closing the lamp in such manner that when it is required to render
the receptacle or reservoir containing the lighting substance free and
accessible for the purpose of filling it, and also when the wick has to be
trimmed or regulated, or any other operation has to be performed in
the lamp, the light shall be forcibly extinguished, thus avoiding any
danger of explosion which might otherwise result from inattention or
negligence.
This safety lamp consists of two distinct parts, viz., the lamp proper
and the safety apparatus, and the two arrangements above alluded to
may be described substantially as follows:-Two lamp glasses or tubes
of glass, or any other suitable transparent material, and having different
diameters, and which are open at both ends, are placed one inside the
other concentrically and so as to surround the wick or flame. The
lower base of the interior cylinder, tube, or chimney is placed a little
above the upper level of the lamp, and thus leaves an annular free space
around the wick. These two tubes or chimneys are overhung by a
hollow cylindrical cap which can be raised and lowered, and always has
a concentric position with regard to the two tubes aforesaid. The outer
tube rests at its lower base on and forms a perfectly air-tight joint with
an elastic washer laid on the ledge or shoulder of the safety apparatus,
the said ledge being fitted on the top of the lamp proper. The height of
the outer or surrounding cylinder. tube, or chimney is such that when
the cap
is quite down this latter shall overlap, cover, and close it her-
metically all round, whereas when the cap is raised more or less there
shall be an annular space between its edge and the upper brim of the
said outer tube.
On examining these arrangements as described it will be easily
understood that when the cap is raised and the lamp lighted the hot
gases evolved by combustion will rise in the inner tube, fill the cap, and
escape downwards through the annular opening between the said cap
and the outer tube; thus the cold air that would be drawn by the said
annular space into the annular space round the wick at the lower end
of the inner tube can only enter if the descending current of the hot
gases of combustion do not completely close or block up (obstruct) the
annular space between the cap and the outer tube or glass; that is to

page_text: say, if the annular column of hot gases leaves under itself a free space
allowing the access of cold air the latter will then form a downward
current between the two lamp tubes and feed combustion. Hence it
follows that the quantity of cold air fed into the lamp is regulated by
the escaping current of hot gases; and if the lamp should be placed in
or pass through explosive gases the latter will only enter the lamp in
such quantity as to burn and be consumed without danger of firing
outside the lamp. When the cap is down, the annular space round the
upper brim of the exterior tube being then closed, and the air or gas
being prevented from entering the lamp so as to keep up combustion,
the light will naturally go out. Then the lamp may be opened without
fear of explosion by separating it from its safety apparatus. This sepa-
ration can only be effected under those conditions of safety, namely, by
means of a combination of a bayonet lock of the safety apparatus with
the lamp proper and a spring stop, and also of a screw motion actuating
the cap by which the admission of cold air is regulated, the said com-
bination being contrived in such manner that when the lamp is lighted,
i.e., when the cap is lifted, the spring stop secures the bayonet motion
and prevents the separation of the two parts of the lamp; whereas, on
the contrary, when the cap is quite down and causes the light to be
extinguished the spring stop is depressed by a rod fixed to the cap, and
its action being thus interrupted the bayonet lock may be moved so as
to allow the separation of the two parts of the lamp.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Melville Clark in the Great Seal Patent
Office on the 15th December 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-third day of June, in the
year of our Lord One thousand eight hundred and sixty-nine, in the
thirty-third year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Alexander Melville Clark,
Her special licence that I, the said Alexander Melville Clark, my

page_text: executors, administrators, and assigns, or such others as I, the said
Alexander Melville Clark, my executors, administrators, and assigns.
should at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "AN IMPROVED ANTI-EXPLOSIVE OR SAFETY LAMP
APPLICABLE FOR MINING AND GENERAL PURPOSES," a communication to me
from abroad by Nicolas Louis Beautils and Jacques Rexroth, both of
Paris, in the Empire of France, upon the condition (amongst others)
that 1, the said Alexander Melville Clark, my executors or administrators.
by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed.
and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Alexander Melville Clark, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the Sheet of Drawings
hereunto annexed, and to the letters and figures marked thereon (that
is to say):-
This Invention consists, firstly, in applying to any description of lamps
lighted by oil, schist, petroleum, or any other illuminating substance an
arrangement for allowing the said lamp to burn safe from explosion
when used in foul air or inflanumable gases, such as are found in coal
mines, and also in public or private establishments through gas escapes.
Secondly. In the use and application of a novel arrangement for
closing the lamp in such manner that when it is required to render the
receptacle or reservoir containing the lighting substance free and
accessible for the purpose of filling it, and also when the wick has to
be trimmed or regulated, or any other operation has to be performed on
the lamp, the light shall be forcibly extinguished, thus avoiding any
danger of explosion which might otherwise result from inattention or
negligence.
This safety lamp consists of two distinct parts, viz., the lamp proper
and the safety apparatus, and the two arrangements above alluded to
.:

page_text: may be described substantially as follows:-Two lamp glasses or tubes
of glass, or any other suitable transparent material, and having different
diameters, and which are open at both ends, are placed one inside the
The
other concentrically and so as to surround the wick or flame.
lower base of the interior cylinder, tube, or chimney is placed a little
above the upper level of the lamp, and thus leaves an annular free
space around the wick. These two tubes or chimneys are overhung
by a hollow cylindrical cap which can be raised and lowered, and always
The
has a concentric position with regard to the two tubes aforesaid.
outer tube rests at its lower base on and forms a most air-tight joint
with an elastic washer laid on the ledge or shoulder of the safety
apparatus, the said ledge being fitted on the top of the lamp proper.
The height of the outer or surrounding cylinder, tube, or chimney is
such that when the cap is quite down this latter shall overlap, cover,
and close it hermetically all round, whereas when the cap is raised
more or less there shall be an annular space between its edge and the
upper brim of the said outer tube.
On examining these arrangements as described it will be easily
understood that when the cap is raised and the lamp lighted the hot
gases evolved by combustion will rise in the inner tube, fill the cap, and
escape downwards through the annular opening between the said cap
and the outer tube; thus the cold air that could be drawn by the said
annular space into the annular space round the wick at the lower end
of the inner tube can only enter if the descending current of the hot
gases of combustion do not completely close or block up (obstruct) the
annular space between the cap and the outer tube or glass; that is to
say, if the annular column of hot gases leaves under itself a free space
allowing the access of cold air the latter will then form a downward
Hence it
current between the two lamp tubes and feed combustion.
follows that the quantity of cold air fed into the lamp is regulated by
the escaping current of hot gases; and if the lamp should be placed in
or pass through explosible gases the latter shall only enter the lamp
in such quantity as to burn and be consumed without danger of firing
outside the lamp. When the cap is down, the annular space round the
upper brim of the exterior tube being then closed, and the air or gas
being prevented from entering the lamp so as to keep up combustion,
the light will naturally go out. Then the lamp may be opened without
fear of explosion by separating it from its safety apparatus. This

page_text: separation can only be effected under those conditions of safety, namely,
by means of a combination of a bayonet lock of the safety apparatus
with the lamp proper and a spring stop, and also of a screw motion
actuating the cap by which the admittance of cold air is regulated,
the said combination being contrived in such manner that when the
lamp is lighted, i.e., when the cap is lifted, the spring stop secures the
bayonet motion and prevents the separation of the two parts of the
lamp; whereas, on the contrary, when the cap is quite down and causes
the light to be extinguished the spring stop is depressed by a rod fixed to
the cap, and its action being thus interrupted the bayonet lock may
be moved so as to allow the separation of the two parts of the lamp.
In order that this Invention may be better understood and more
readily carried into effect, I will now proceed to describe the same,
reference being had to the annexed Sheet of Drawings, and to the
letters and figures marked thereon.
Figure is an elevation of the inexplodible safety lamp, as herein-
before substantially described, the two component parts of the lamp
being shewn asunder, and hence the lamp extinguished.
Figure 2 is a vertical section through the axis of Figure 1, the lamp
being mounted and lighted, and therefore prevented from being open.
Figure 3 is a vertical section corresponding with Figure 2, the lamp
being mounted but having just been extinguished, the two component
parts of the lamp being separable.
Figure 4 is a plan of the lamp proper shewing in horizontal section
the bayonet arrangement by which it is united with the safety apparatus.
Figure 5 is a top view of the safety apparatus.
Figure 6, a horizontal section of the same through the line T, U.
Figure 7, a horizontal section through the line V, X, and Figure 8 a
section through Y, Z, shewing, like Figure 7, the mode of supporting
the glasses in the safety apparatus. The same letters of references denote
the like parts in all these views.
The lamp proper A has at its upper portion a groove a, a, into
which three or more cross stays b, b, b, are soldered, forming the
male portion of the bayonet joint above described. The said lamp
also carries a sheathe guide or casing c, which contains a spring c
for holding the stop or pin d in an elevated position.
Lastly,

page_text: this lamp is provided with a well-known contrivance, which consists
of a small rod or wire e working vertically and by rotation in a
sheath collar or stuffing box on the lamp, the said wire being bent
like a hook at its upper part, in such manner that by turning it the
point may enter the opening h in the wick carrier for the purpose
of raising or lowering the wick or removing the charred portion of the
same, according to the degree of elevation given to it by hand through
the outside button i. Instead of this system for regulating the wick,
as shewn at Figures 2, 3 and 4, the ordinary rack arrangement may be
used, as shewn at Figure 1.
The safety apparatus may be described as follows:-B, disc or ledge
carrying the whole of the safety apparatus, being connected with the
lamp by means of three or more ears or lugs j, j, j, forming a bayonet
joint with the cross stays b, b, b, of the lamp; C, intermediate disc; D,
upper disc.
These three dises (or more, as the case may be) are con-
nected together by means of a suitable number of soldered and riveted
rods E, E, E, E, E, E', the last of which is made hollow or tubular,
and instead of passing through all three discs only connects those B
and C. F, outer or surrounding cylindrical chimney made of glass or
any other transparent matter, its lower edge rests on a leather washer
on the disc B. The height of this chimney is such that its upper edge
bears against the under face of the disc C. G, interior cylindrical
chimney made of glass or other transparent material, and resting on
the perforated gallery H. This latter is raised or extends to such height
that the chimney G may leave at its bottom part a free space all round
the wick, and allows the cold air to feed the same by passing through
the openings in the gallery H. 1, cylindrical hollowed cap, which is
raised or lowered by means of the screw J and the finger button K.
This cap is guided in its vertical motion by the rods E,
and
its descent is limited by the disc C, on which it will bear by closing it
completely. This cap carries a rod or wire L, which is soldered and
riveted against it, and which shares the vertical motions as they are
imparted to the cap. This wire works in the tube E', and its length is
such that when the cap is lowered completely its lower extremity comes
flush with the under side of the disc B (see Figures 1 and 2). The
interior chimney G lengthens out by a metallic tube M, which ends
near the top of the cap, still allowing its complete descending move-

page_text: ment. It will be readily understood that this portion M of the inner
chimney being contained inside the cap may be made of any suitable
opaque material, thus lessening both the length of the transparent
chimney and its liability to breakage. The perforated galleries H, N, O.
are made in such manner that their flanges nicely clip the chimneys,
which they have to keep in their place, thus avoiding any oscillation,
which might cause breakage; at the same time the apertures of the
said galleries are calculated so as to give free passage to the gas currents.
As has been specified the outer chimney Frests on a piece of leather
laid on the ledge B. To effect this the said leather washer is
inserted under the small spring blades 1, 1, 1, which are riveted to the
ledge B. In order to give to the leather the proper support and body,
which it might lose in consequence of dampness or any other cause, a
thin copper or brass washer m is placed underneath it, in which three
notches n, n, n, are cut corresponding with the springs 1, 1, 1. The
washer is placed in such manner that when the said notelies are
opposite the springs, by pressing on it, and giving it one-fifth or one-
sixth of a turn, the metal and leather washers are firmly united with
the dise or ledge B, and hence with the whole safety apparatus. This
apparatus acts as follows:-Supposing the lamp to be lighted, and
hence closed, it will be seen by Figures 2 and 4 that when the lugs j, j, j,
hug the cross rods b, b, b, however little is raised the cap and the
rod L which it carries, a certain empty space exists at the foot of
the tubular rod E', and as the latter corresponds with the stop d, the
said stop acted upon by its spring enters the tube and thus prevents any
rotary motion by which the bayonet joint might be disengaged; hence
it follows that the two parts of the apparatus are united inseparably as
long as the cap is raised, that is to say, while the lamp is burning.
Supposing the cap to be at the maximum of its elevation deemed
necessary for the proper working of the lamp (see Figure 2) the hot
gases produced by combustion will then rise in the chimney Gand
its extension M, thus filling the cap 1, and escape through its lower
part in the direction of the dotted line arrows, leaving under the current
formed by the said gases a free space, which allows the cold air or
ambiant gas to flow across the gallery N into the annular space left
between the chimneys F, G, whence the said gas or air proceeds to feed
the wick by passing through the openings in the gallery H. The
current formed by the gases feeding the combustion is represented by

page_text: the firm line arrows. When from any cause whatever it becomes of
necessity to separate the safety apparatus from the lamp proper the сар I
is lowered until it closes the aperture of the disc C. The admittance of
the feeding gases being thus stopped, the lamp will go out, and the
rod 1. having pushed back the stop d into its guide or sheath nothing
more prevents the safety apparatus from turning so as to disengage
the lugs or ears j, j, j on it from the cross stays b, b, b, in the lamp,
and the two parts can thus be separated.
It is distinctly understood that the foregoing is only one of the
arrangements that may be employed for constituting the safety lamp by
using the current of hot gases at their issue as a valve for regulating the
admittance of cold air or gas feeding the combustion of the lamp. Thus,
for instance, as a substitute for the outer cylindrical chimney a series
of vertical tubes arranged around the lamp might be used, these tubes
being intended for the introduction of cold air or gas, which introduction
is limited by a certain free space between the said tubes and others
placed over and above the former ones for allowing the hot gases to
escape; also, instead of feeding combustion by a cold air or gas current
proceeding from above the lamp, the tubes last alluded to which allow
the escape of the hot gases may be extended down to the bottom of the
lamp, and the tubes which distribute the cold air or the gas around the
wick may be made to conduct the same in an upward direction.
By these two arrangements the outer chimney is done away with,
although they are based on the same acting principle as the arrangement
represented and described.
CLAIMS.
First. The safety lamp above described, the characteristic feature of
which is the use and application of the current of hot gases evolved
by combustion, the said current being suitably regulated at the escaping
points, and acting in the manner and way of a regulating valve for the
admission of either the quantity of cold air required for combustion or
of inflammable gases, when such are met with, so as to cause the latter
being burnt in the lamp without any danger of firing or exploding the
gases outside.
Second. The above described arrangement of two tubes or chim-
neys F, G, and of the moveable cap I, or any other modification thereof
after the same principle.

page_text: Third. The novel closing arrangement, as described and characterized,
mainly by rendering it impossible for the user to open the safety lamp
without the flame having previously become extinguished.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and seal, this Fourteenth day of Decem
ber, in the year of our Lord 1869.
Witness,
JAMES DAISH,
58, Chancery Lane,
London.
A. M. CLARK. (L.S.)