IMPROVEMENTS IN THE CONSTRUCTION OF OIL LAMPS
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Thomas Wright Shaw at the Office
of the Commissioners of Patents on the 21st August 1878.
THOMAS WRIGHT SHAW, of the City of Edinburgh, North Britain, Gentleman.
"IMPROVEMENTS IN THE CONSTRUCTION OF OIL LAMPS."
This Invention relates to improvements in the construction of oil lamps for ships,
signals, railway, tramway, and other carriages, and for other lighting purposes for
which oil lamps have heretofore been employed, which improvements render such
lamps capable of burning the crude or heavy mineral oils, such as hitherto used
only for lubricating purposes, whereby a great saving is effected in the cost of oil
for these lamps, which are also much safer than the ordinary lamps, and will not
explode under a heat of 240° or thereabouts when burning these heavy oils.
And the nature and novelty of the Invention consist in forming the lamp with a
double top and bottom, that is, an annular air space or chamber is formed above
and below the light by horizontal divisions converging from the sides towards the
centre of the lamp case. The upper air chamber or space is partially open above,
as the uppermost. division or plate does not extend inwards quite to the chimney of
the lamp, this opening allowing free ingress for the air to enter the tubes herein-
after referred to, the lower plate or division of this air chamber being preferably.
convex on its lower side, facing the flame, so as to act as a reflector or deflector of
the light towards the lense, the convexity being sufficiently prominent to bring the
bright surface of the metal within the focus of the lense.
It is preferred to carry or extend the chimney of the lamp down through the
lower plate of the upper air space to near the highest level of the flame, and its
lower end is trumpet mouthed for the better conducting of the heat up through it
to the exit end.
The bottom air chamber is formed by horizontal divisions or plates in a similar
manner, converging from the sides towards the centre, but not quite close to the
centre, so that room is left for the wick passing up from the oil well or fountain
below, the air chamber or space being placed immediately above the level of the oil
well, but under the level of the light.

page_text: In order then to get a circulation of air from the upper chamber to the lower
one, and thence to the flame to support combustion, two pipes or tubes are led
from the one chamber to the other, the upper ends of the pipes being open into the
upper air chamber to receive the air, and their lower ends fit into short sockets or
joint pieces projecting slightly up from the lower chamber, so that on closing the
lamp the lower ends of the tubes slip into these sockets, and the junction from
above is complete.
The lid proper of the lamp is slightly larger than the diameter of the air entrance
to the upper chamber and is hinged, so that when closed down a considerable
opening is left below between it and this top entrance, which is fitted with an
annular ring outside to prevent the outer air from blowing direct in, this ring being
so secured to the top of the lamp as to leave a space all round its lower edge to
admit the air for supporting combustion in a narrow annular stream up over the
upper edge of the entrance to the air chamber, while the waste product of com-
bustion escape up the central chimney and out along the under surface of the lid,
thence out through the upper annular space between it and the outer guard ring,
and to which the lid may be hinged, and the handle for carrying the lamp secured.
The air thus admitted from the top of the lamp into the upper chamber, where it
is heated, passes down the tubes into the lower chamber, thence up through the
air space, fitted with the usual finely perforated plates, to the flame of the wick,
which is directed by the usual wide cut or slotted deflector cap, all surrounding the
wick holder; the air and oil are thus consumed together, and give a very bright
and smokeless flame. The upper ends of the tubes being placed at the sides of the
lamp are overlapped by the upper plate or division of the air chamber, so that
down draughts are entirely prevented, and a steady light is constantly maintained
in all weathers or under any circumstances.
In other respects the lamp or lamp case is of the ordinary construction, and
fitted with the ordinary side glass or lenses, but instead of the air tubes being
inside they may be outside of the lamp, and have their ends connected or led
through the sides at the level of the top and bottom chambers, and so produce the
same results, but the inside arrangement is preferred as being most compact.
In applying these improvements to railway carriage or other roof lamps, which
require to open at the top and reflect the light downwards through glass below,
instead of having the lower air chamber in the base of the lamp itself a special air
chamber of a similar construction, with oil well below or contained in it, is sus-
pended in or near the centre of the ordinary glass globe by the lower ends of the
two air tubes being soldered or fitted thereinto, thus conducting the air from the
upper compartiment of the lamp to the flame in the same manner as in the ship or
signal lamp by two tubes, which are jointed by sockets attached to the upper air
chamber in the top of the lamp, which sockets, when the top of the lamp is closed,
come down over the upper ends of the tubes, which pass down through the concave
reflector and its back supporting plate carried on a metal ring or. seat round the
inside of the lamp above the glass, and made to carry the lower part of the conical
metal chimney, which in this case is made in two parts, the upper part overlapping
the upper end of the lower part, and is carried in and passes up through the upper
air chamber, in the top of the lamp to near the lid, which is hinged and fitted with
the outer guard ring, all substantially as described in reference to the signal or side
light lamp, the air for supporting combustion passing down the tubes to the wick
and flame, as herein-before described, and any surplus air not passing down the
lower tubes from the upper chamber passes out through the socket joint, so as to
cool the back plate of the reflector.
The upper compartment or division of the railway carriage or roof lamp case
may when desired be made to serve as the upper air chamber of the ship or side-
light lamp already described.
In order to burn the ordinary heavy or lubricating oils, for which this lamp is
specially designed, certain proportions of diameter of the air tubes to the dimensions

page_text: of wick are found to give the best light; for example, I have found that when
burning a /, inch flat wick with the said heavy oils two tubes of 3/8 inch inside
diameter answers best, and for greater or less sizes of wicks and lighter densities of
oils proportionately greater or less diameter of tubes should be used in order to
give the necessary supply of air to ensure the combustion of the particular oil used,
but other means may be adopted for regulating this supply of air, such as controlling
valves in the said air tubes or ducts.