IMPROVEMENTS IN SAFETY LAMPS
Year: 1854

page_text: LETTERS PATENT to Thomas Purdon, of the Town and County of Hull,
Ironmonger, for the Invention of "IMPROVEMENTS IN SAFETY LAMPS."
Sealed the 6th March 1855, and dated the 14th September 1854.
PROVISIONAL SPECIFICATION left by the said Thomas Purdon at the
Office of the Commissioners of Patents, with his Petition, on the
14th September 1854.
I, THOMAS PURDON, of the Town and County of Hull, Ironmonger, do
hereby declare the nature of my said Invention for "IMPROVEMENTS IN SAFETY
LAMPS to be as follows:-
This Invention relates to various arrangements of the details of safety
lamps as used in mining operations and in other pursuits, the objects being
the obtainment of superior safety and higher degree of illuminating power than
is at present secured by the ordinary lamps. The oil for the light is contained
in a shallow base chamber, arranged to be screwed or otherwise attached from
beneath into the bottom of the lantern part; the wick is of the flat thin kind,
so as to secure a good clear body of flame with but little heat. The lantern
portion immediately surrounding the light is preferred to consist of a rect-
angular frame, the vertical pieces of which are grooved out to receive the
window picces, which are passed in as slides. These window pieces consist of a

page_text: central sheet of glass, defended by an outer and an inner sheet of talc, thus
forming a compound diaphragm of great strength. When the sheets of talc
are laid upon the glass, copal varnish or other transparent matter is introduced
between the contact surfaces; this interposed matter binds the three sheets
together, and it dries near the edge whilst it remains fluid or partially so
towards the centre. The talc defends the glass from accidental fracture, and
if the central glass sheet should be broken, the interposed varnish entering the
cracks strengthens the injured part. The lantern portion of the lamp is
covered in by a slightly convex metallic disc, forming the base of a tall and
narrow perforated cylinder or chimney, this disc being of use in preventing
injury from the fall of water. The base of the chimney is filled in by fine wire
gauze, either in the form of a flat diaphragm or a hollow cone. The chimney
is coarsely perforated, and is of stout metal; it is surmounted by an elevated
open cover piece, with a suspension ring at the top. The lamp may be either
carried by this ring or grasped by the perforated chimney, the great area of
which prevents the occurrence of intense heat. One of the sides of the lantern
portion. is fitted with a reflector, behind which there is no glass, the space being
filled up by two wiro gauze diaphragms, with a non-conducting air spaco
between them.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Purdon in the Great Seal Patent Office on the
14th March 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, 1, THOMAS
PURDON, of the Town and County of Hull, Ironmonger, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of September, in the year of our
Lord One thousand eight hundred and fifty-four, in the eighteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
ine, the said Thomas Purdon, Her special license that I, the said Thomas
Purdon, my executors, administrators, and assigns, or such others as I, the
said Thomas Purdon, my executors, administrators, or 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

page_text: SAFETY LAMPS," upon the condition (amongst others) that I, the said Thomas
Purdon, by an instrument in writing under my hand and seal, should par-
ticularly 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 Thomas Purdon, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the accompanying Drawings, and to the
letters and figures marked thereon, that is to say:-
My said Invention relates to various arrangements of the details of safety
lamps, as used in mining operations and in other pursuits, the objects being
the obtainment of superior safety and a higher degree of illuminating power
than is at present secured by the ordinary lamps. The oil for the light is con-
tained in a shallow base chamber, arranged to be screwed or otherwise
attached from beneath into the bottom of the lantern part. The wick is of the
flat thin kind, so as to secure a good clear body of flame with but little heat.
The lantern portion immediately surrounding the light is preferred to consist
of a rectangular frame, the vertical pieces of which are grooved out to receive
the window pieces, which are passed in as slides. These window pieces con-
sist of a central sheet of glass, defended by an outer and an inner sheet of tale,
thus forming a compound diaphragm of great strength. When the sheets of
tale are laid upon the glass, copal varnish or other transparent matter is intro-
duced between the contact surfaces. This interposed matter binds the three
sheets together, and it drys near the edge, whilst it remains fluid or partially
so towards the centre. The tale defends the glass from accidental fracture,
and if the central glass sheet should be broken, the interposed varnish entering
the cracks strengthens the injured part. The lantern portion of the lamp is
covered in by a slightly convex metallic disc, forming the base of a tall and
narrow perforated cylinder or chimney, this disc being of use in preventing
injury from the fall of water. The base of the chimney is filled in by fine wire
gauze, either in the form of a flat diaphragm or a hollow cone. The chimney
is coarsely perforated, and is of stout metal; it is surmounted by an elevated
open cover piece, with a suspension ring at the top. The lamp may either be
carried by this ring or grasped by the perforated chimney, the great area of
which prevents the occurrence of intense heat. One of the sides of the lantern
portion is fitted with a reflector, behind which there is no glass, the space being

page_text: filled up by two wire gauze diaphragms, with a non-conducting air space
between.
And in order that my said Invention may be more readily understood,
I shall now proceed to describe the several Figures on the Sheet of Drawings
hereunto annexed.
Figure 1 of my Drawings represents a side elevation of the lamp complete,
nearly full size; Figure 2 is a corresponding plan of the same, with the upper
portion or chimney of the lamp removed; Figure 3 is a vertical section of the
lamp; Figure 4 is a corresponding sectional plan of the same, taken along
the line 1, 2, in Figure 3; Figure 5 is a vertical section, taken at right angles
to Figure 3; and Figure 6 is a corresponding sectional plan of the same,
taken along the line 3, 4, in Figure 5. The oil for the light is contained in
the shallow base chamber A, which is screwed or otherwise attached from
beneath on to the bottom B of the lantern part. The wick C is of the double
flat thin kind, so as to secure a good clear body of flame with but little heat.
It is fitted into an ordinary flat wick holder, which is secured in the usual
manner to the top of the oil pan A. The lantern portion of the lamp is
preferred to consist of a rectangular metal frame, the vertical supports D of
which are secured by rivets to the top plate D₁ of the lantern, and may be
formed each out of a single piece of tin plate or sheet brass, which is so
doubled or shaped as to constitute two lateral grooves at right angles to each
other, as shown in the section Figure 4. These grooves serve to contain the
wire gauze frame E, and the window pieces F, F, of the lantern, which are
slid into them from above, and secured and made perfectly close by means of
plaster of Paris or other material in the form of cement, when the upper or
chimney part of the lamp is removed. The window pieces consist each of a
central sheet of glass, colored green in the enlarged sectional detail, Figure 7
of the Drawings, defended by an outer and an inner sheet of tale, shewn by
yellow lines in the same Figure, thus forming a compound transparent
diaphragm of great strength. The sheets of talc are laid on to and secured
to the sides of the glass by copal varnish or other suitable transparent material,
as herein-before described. The lantern portion of the lamp is covered in by
a slightly convex metallic disc G, forming the base of the tall and narrow
perforated cylinder or chimney H, which is screwed at I on to the top plate D₁
of the lantern part of the lamp, and fixed by a small pinching screw at 1'.
The disc G serves to protect the lantern portion of the lamp from injury by
the falling of water. The base of the chimney is filled by two diaphragms J
of fine wire gauze, either in the form of flat discs or of hollow cones, or both

page_text: combined, a non-conducting air space being left between such diaphragms.
The chimney H is coarsely perforated, and is of stout metal; it is surmounted
by an elevated open cover piece K, with a suspension ring at the top. The
lamp may either be carried by this ring or grasped by the perforated chimney,
the great area of which prevents the occurrence of intense heat. On the wire
gauze side E of the lantern is fitted a reflector L, for the purpose of increasing
the illuminating power of the lamp, and throwing forward the light. The
wire gauze sido E is composed of two diaphragms, as in the gauze at the base
of the chimney, an air space being left between the two diaphragms. By this
construction and arrangement of safety lamp, no rush of air can pass through
the lamp when being carried, as one square only is open for the admission of
air, and that square is placed at the back of the lamp.
Another advantage derived from the use of only a small portion of wire
gauze is, that as a less amount of air is admitted to the light, any deterioration
or want of oxygen in such air will all the more readily have effect upon the
flame, and finally extinguish it entirely, when the atmosphere becomes so
vitiated as to become highly dangerous. The lamp is locked by a very simple
contrivance; the vertical bolt of the lock, which is fixed to the oil pan, taking
into a covered or protected slot or hole in the base plate M of the lantern, as
shewn in the section, Figure 3. The bolt of the lock when shot up enters the
covered hole in the plato M, and consequently prevents the oil pan or base A
of the lamp from being turned round to unscrew it from the lantern part. As
the glasses are fixed in grooves, they can easily be replaced when required by
simply unscrewing the chimney and disc G, when the broken ones may be slid
out and fresh glasses inserted.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe, in conclusion, that I do not confine or restrict myself to
the precise details or arrangements which I have had occasion to describe or
refer to, as many variations may be made therefrom without deviating from
the principles or main features of my said Invention; but what I consider to
be novel and original, and therefore claim as the Invention secured to me by
the herein-before in part recited Letters Patent, is,-
First, the general combination or arrangement of parts constituting a safety
lamp, as herein-before described and illustrated in my Drawings.
Second, the application and use of glasses in safety lamps, such glasses or
window pieces being protected on one or both sides by a sheet or sheets of
talc, as herein-before described.

page_text: Third, the application and use of the reflector in combination with the double
ganze diaphragm E, such diaphragm enclosing only a small portion of the
lamp in place of entirely surrounding the flame.
Fourth, the application and use of the double wire gauze diaphragm J
in combination with the coarsely perforated chimney H, as herein-before
described.
In witness whereof, I, the said Thomas Purdon, have hereunto set my
hand and seal, the Twelfth day of March, One thousand eight hundred
and fifty-five.
THOMAS PURDON. (L.S.)
THOMAS PURDON. (L.B.)