Manufacture of Electric Lamps.
Year: 1885

page_text: Manufacture of Electric Lamps.
I WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake, and Co, Patent Agents,
Southampton Buildings, in the County of Middlesex do hereby declare the nature
of my invention for "AN IMPROVED AIR PUMP CHIEFLY DESIGNED FOR USE IN
THE MANUFACTURE OF ELECTRIC LAMPS and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
33
This invention relates to a pump chiefly designed for exhausting the air from
the glass bulbs of electrical incandescence lamps, but also applicable for other
purposes. The improved pump enables the air pressure in the said bulbs to be
reduced to 7.000.000 of the atmospheric pressure and even below this point.
In the accompanying drawing,
Figure 1 is a longitudinal section of a pump constructed according to this
invention.
Figures 2 and 3 are views of details.
The pump consists of a cylinder or tube a, about 125 centimetres long, with an
internal diameter of 12, 7 centimetres. The top end of the cylinder a is closed by
a lid b, through which passes the toothed rod or rack c of the piston d and the
rod e for opening and shutting a stop-cock as will be hereinafter described.
The lid b is provided with a small support f carrying a shaft on which are fixed
a pinion g, gearing with the toothed rod or rack cand a crank h; another shaft
carries a guide pulley j.
The piston d of the pump is formed of a series of round pieces of leather clamped
between the spherical bottom of the piston and a nut i.
The lower end of the cylinder a is closed by a cover k provided with a spherical
cavity corresponding to the spherical bottom of the piston d and very tightly
closing the cylinder. The spherical cavity of the bottom k is carefully fitted to

page_text: the spherical bottom of, the piston d, so that the volume of oil contained between
these parts cannot exceed 200 cubic millimetres. The piston d is provided with
a cavity in which oil is poured. Through the bottom k passes a central conduit,
which is closed by a stop-cock m.
This conduit leads to a small reservoir n,
designed to collect the drops of oil and provided with a bent tube o which, by
means of a glass tube p having two spherical enlargements communicates with the
lamp from which the air is to be exhausted.
Beneath the glass tube p is suspended a small india-rubber reservoir q which is
provided with a spiral spring and is filled with oil. This reservoir serves to
indicate the action of the apparatus as will be hereinafter describe.J.
The piston rod c, screwed into the central boss of the piston, is provided with a
very fine central conduit, closed by a stop-cock r of the construction shown in
Figures 2 and 3. The key or nut 8 of the said stop-cock is provided with two
channels at right angles to each other and connecting (when the handle of the
stop-cock is in the position shown in Figures 1 and 2 of the drawing) with the
fine central conduit of the rod c and of the bottom k, and with the cavity / of
the piston d.
The operation of the improved pump is as follows, that is to say:-when the
riston d is at the bottom of the cylinder a the stop-cocks r and m are shut and
the lamp is very tightly connected (by means of an india-rubber tube) with the
end of the glass tube p.
By turning the crank h the piston d is caused to ascend and the air in the
cylinder is rarefied. As soon as the piston arrives at the end of its stroke, the
stop-cock m is opened for one or two seconds at the utmost so that the air issuing
from the bulb of the lamp, is also rarefied and passes into the cylinder a. By
opening the stop-cock m suddenly a drop of oil will be projected from the top of
the reservoir g into the enlargement p¹ of the glass tube p.
After shutting the stop-cock m, the stop-cock r is opened by means of the rod Z,
and the crank h is turned, causing the piston d to descend.
During this descending motion, the air below the piston passes through the
central conduit of the rod c and through the stop-cock to the outside.
When the piston arrives at the end of its stroke, the stop-cock r is again shut
and the crank is turned in the opposite direction, causing the piston d to rise and
the air in the cylinder to be further rarefied. At the end of the ascending motion
of the piston the stop-cock m is again opened for a short space of time, whereby a
further rarefaction of the air in the bulb is produced.
A few strokes of the piston are sufficient to attain the limit of the vacuum
which, with a cylinder having the aforementioned dimensions is about 7000,000 of
the atmospheric pressure. The operation is stopped as soon as no motion is
observed with the oil drop in the glass tube p, when the stop-cock m is suddenly
opened.
The reservoir q is made of india-rubber, in consequence whereof it can be
stretched by hand in order to diminish the volume of the oil drop moving in the
glass tube p, because this drop, as will be easily understood, towards the end of
the operation must be as light as possible, in order that it may be moved by the
action of the insignificant quantity of air still remaining in the bulb of the lamp.
By making the cylinder a longer, evidently a still greater rarefaction of air is
obtained; the degree of rarefaction is likewise increased if the bulb of the lamp is
heated whilst the pump is in action.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that I claim in a vacuum pump such
as that above described and shown in the accompanying drawing
First. The combination of the cylinder a of considerable length, and the piston d
provided with a stop-cock for alternately shutting and opening a fine conduit made

page_text: in the rod of the piston and communicating with the reservoir from which the air
is to be exhausted.
Second. The application of an indicator consisting of an india-rubber tube q
filled with oil and acting as described.
Third. The construction and combination of the parts constituting the said
vacuum pump, substantially as set forth and shown in the accompanying
drawing.
TL
1002
HASELTINE, LAKE & Co.,
For the Applicant.