IMPROVEMENTS IN SAFETY LAMPS
Year: 1868

page_text: LETTERS PATENT to William Hann and Edmund Mills Hann, of
Hetton Colliery, near Fence Houses, in the County of Durham, for
the Invention of "IMPROVEMENTS IN SAFETY LAMPS."
Sealed the 2nd February 1869, and dated the 6th August 1868.
PROVISIONAL SPECIFICATION left by the said William Hann and
Edmund Mills Hann at the Office of the Commissioners of Patents,
with their Petition, on the 6th August 1868.
We, WILLIAM HANN and EDMUND MILLS HANN, of Hetton Colliery,
near Fence Houses, in the County of Durham, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN SAFETY LAMPS," to be as
follows:-
This Invention has for its object to so protect the flame of the lamp
from pressures of wind that only sufficient air is admitted to supply
the combustion of the flame and to prevent the admission of such a
quantity of air as would endanger the safety of the lamp when exposed
to an explosive mixture travelling at a high velocity.

page_text: The improvements relate chiefly to the class of lamp known as the
Stephenson lamp in which a glass chimney is employed within the
outer cylindrical wire casing. In order to prevent the passage of any
current between the wire gauze casing and the glass chimney we
fit the bottom of the chimney to the upper surface of a ring which
has projecting up from it a cylindrical flange which fits within the
bottom of the glass chimney, the glass chimney being fitted to the ring
and its flange by grinding or it might be by the interposition at the ends
of some elastic but non-combustible substance to prevent breakage, the
outer circumference of this ring at a point below the bottom of the
glass chimney is caused to nip or embrace the wire gauze cylinder
between itself and the lower part of the lamp frame which the ring
screws into, the gauze is thus embraced or held all round between
two closely fitting metal surfaces so that no explosion could pass at
this point to the exterior of the lamp. The glass chimney is held down
by the top of the lamp so that it cannot rise up off the ring upon which
its lower end rests. Air is admitted to the lamp through apertures
in the lower frame, and the air after passing through the lower portion
of the wire gauze cylinder passes through apertures cut or bored in
the screw ring which the glass rests upon, and rises up through a
horizontal gauze or perforated plate before it can reach the burner. The
horizontal gauze or perforated plate may either be attached to the screw
ring on which the glass rests or it may be fitted to the wick tube or to
both. This arrangement of admitting air into an annular chamber and
allowing it to rise up therefrom to the burner through a horizontal
gauze or perforated plate may be adapted to other forms of safety lamps.
For protecting the tops of safety lamps from currents of air wo
employ a cap or top of a hemispherical form with apertures through its
sides for the exit of the products of combustion. At the lower end of
the hemispherical top we fix an arched internal shield which has a
central opening formed through it, or numerous small openings might
be formed through the arched shield in place of the one central opening.
Internal arched shields or guards of this description may also be used
with tops, or caps of other forms. A cap or top such as above, described
may be applied to the top of a single tube of metal fitted to the top of
the glass of the lamp; this tube may either be of a cylindrical or
conical form, and it may have within it one or more arched guards
or shields such as above described. It may also have within it a

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Hann and Edmund Mills Hann in the
Great Seal Patent Office on the 5th February 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, WILLIAM
HANN and EDMUND MILLS HANN, of Hetton Colliery, near Fence
Houses, in the County of Durham, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixth day of August, in the year
of our Lord One thousand eight hundred and sixty-eight, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said William Hann and Edmund Mills
Hann, Her special licence that we, the said William Hann and Edmund
Mills Hann, our executors, administrators, and assigns, or such others.
as we, the said William Hann and Edmund Mills Hann,, our 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 "IMPROVEMENTS IN SAFETY.
LAMPS," upon the condition (amongst others) that we, the said William
Hann and Edmund Mills Hann, our executors or administrators, by an
instrument in writing under our or their hands and seals, or under the
hand aud seal of one of us or them, 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 we, the said William Hann and Edmund
Mills Hann, 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 thereof, that is. to.
say:-

page_text: This Invention has for its object so to protect the flame of the lamp
from pressures of wind that only sufficient air is admitted to supply
the combustion of the flame, and to prevent the admission of such a
quantity of air as would endanger the safety of the lamp when exposed
to an explosive mixture travelling at a high velocity.
The improvements relate chiefly to the class of lamp known as the
Stephenson lamp in which a glass chimney is employed within an outer
casing of wire gauze. In order to prevent the passage of any current
of air or gas between the gauze and lower end of the glass chimney,
we fit the bottom of the glass to the upper surface of a ring which
has projecting from its upper surface a cylindrical flange which fits
within or it might be to the outside of the glass. Such glass chimney
being fitted both to the flat surface of the ring, and to the flange by
grinding, a ring of some clastic and non-combustible substance may
be used between the glass and ring to reduce the risk of breakage. The
cylindrical gauze casing which surrounds the glass is continued down
below the glass, and through this lower part of the gauze air is admitted
to the lamp, the outer circumference of the ring which carries the glass
fits accurately to the interior of the gauze casing above the point of
inlet of air, whilst at the same point the exterior of the gauze is cm-
braced by the lower framework of the lamp, and the gauze being thus
held between two metal surfaces fitting closely against it, it is impossible
for an explosion to be communicated to the external atmosphere at
this part. The air is admitted through holes in the lower frame and
after passing through the gauze cylinder passes through apertures cut
or bored in the screw ring and below the surface of the flange which
holds the glass, and may then if desired rise through a horizontal gauze
or perforated plate before reaching the burner, but this we do not find
to be essential. The air after passing the burner rises through the
glass and through a non-perforated metal chimney on the top thereof,
which metal chimney fits within the top cap of the lamp, and the glass
and metal chimney are thereby held in place, a flange on the metal
chimney overlaps the end of the glass, which renders the joint perfectly
secure, whilst the upper end of the metal chimney fits within a
flange, projecting downwards from the top framework in which a side
projection keeps it a little below the under plate of the top or cap,
the gauze being embraced between the two so as to render it impossible

page_text: over the top of the metal chimney.
Having thus described the nature. of our Invention, we will proceed
to describe more fully the manner of performing the same.
Figure 1 of the Drawings hereunto annexed shows a vertical section,
and Figure 2 shows a side view of a safety lamp constructed as above
described.
a is the oil vessel of the lamp, on to this screws a ring 6 which carries
the upper parts of the lamp, so that by unscrewing this ring the whole
of the upper parts of the lamp can be removed. Into the interior of
this ring screws the ring c, to the upper flat surface of which the lower
end of the glass chimney d is fitted by grinding, there being a cylindrical
flange projecting up from the ring to which the exterior of the glass is
similarly fitted; or, as before stated, the flange might be of a diameter
to fit within the glass. The rings b and c are perforated for admitting
air to the lamp as shown; the glass chimney has above it a metal
chimney composed of a single tube of metal e, the lower end of which
fits on to the top of the glass, whilst its upper end fits into the cap or
guard which forms the top of the lamp and which protects the top of
the chimney from any currents of air impinging directly against it; the
cap or guard is held down by rods to the ring b as is usual, and as the
top of the metal chimney fits up against the cap the glass and metal
chimney will thereby be held securely in their places, which is of very
great advantage. f is the cylinder of wire gauze which surrounds both
the glass and metal chimney, it extends down below the bottom of the
glass so that the air entering through the perforations in the ring b has
to pass through the gauze before entering the perforations in the ring c,
the lower end of the gauze is held at a point below these perforations
between a flange on the bottom of the ring c and an internal flange on
the ring b, so forming a tight joint; above the perforations the gauze is
embraced between the upper part of the ring c and another internal
flange on the ring b, so that no explosion can pass at this point. The
cap or guard of the lamp shown in the Drawing is formed as we prefer
it should be in a similar manner to that described in the Specification of a
former Patent granted to one of us on the 7 February 1868 (No. 419),
but for the sake of convenience, in place of making numerous perforations

page_text: in the side of the dome, we make a double plated top, a clear space being
left all round between the plates in place of the perforations. The
plates are held at a slight distance apart from one another by distance
pieces, the lower one has a central opening for the products of com-
bustion from the lamp to rise up through it, whilst the central portion of
the other plate is dished or arched as shown. A flange on the lower
disc of the cap extends downwards and overlaps the top of the metal
chimney and the wire gauze, so making a tight joint.
At Figures 3 and 4 of the Drawings hereunto annexed is shown a lamp
of the kind known as the Clanny lamp, the glass of this lamp. is similarly
fitted at its lower end by grinding to the flat surface of a ring of metal
which has a flange standing up from it, to which the glass is similarly
fitted by grinding whilst air is admitted to the lamp, first through
perforations in the ring b, and then through perforations in the ring
upon which the glass rests, the perforations in this ring being in this
case small safety perforations, as there is no gauze in front of them.
Having thus described the nature of our Invention, and the manner
of performing the same, we would have it understood that what we
claim is,-
First. Constructing safety lamps in such manner that whilst air is
admitted to the lamp through the lower part of the outer gauze casing
and through perforations in a ring upon which the glass rests, any
explosion is prevented passing between the gauze and glass by the
gauze being held above the point where the air enters between the
ring upon which the glass rests, and an outer ring as herein described.
Second. Constructing safety lamps which have an inner glass chimney
surrounded by an outer casing of wire gauze with the glass chimney
fitted at its lower end by grinding to a flat seat and to a cylindrical
flange projecting up from it, such glass chimney being held down on to
the seat by the top of the lamp.
Third. Constructing safety lamps with an outer casing of wire
gauze surrounding a non-perforated chimney formed wholly of glass or
at its lower end of glass and at its upper end of a tube of metal having
a partition of wire gauze across it, and with the top of the chimney
fitted into a cap or guard to protect it from currents of air, as herein
described.

page_text: Fourth. Constructing safety lamps in such manner that air is admitted
to the lamp through perforations or holes in a ring, upon which the
bottom of the glass rests whilst the glass is fitted to such ring by a tight
joint, as herein described and shown at Figures 3 and 4.
Fifth. The general combination or arrangement of parts of safety
lamps, substantially as herein shown and described.
In witness whereof, we, the said William Hann and Edmund Mills
Hann, have hereunto set our hands and seals, this Third day
of February, in the year of our Lord One thousand eight hundred
and sixty-nine.
WILLIAM HANN.
(L.S.)
EDMUND MILLS HANN. (L.S.)