IMPROVEMENTS IN THE CONSTRUCTION OF ELECTRIC LAMPS, AND IN SEALING ELECTRICAL CONDUCTORS INTO AIR TIGHT RECEIVERS."
Year: 1881

page_text: "
PROVISIONAL SPECIFICATION left by Charles Henry Gimingham at the
Office of the Commissioners of Patents on the 12th May 1881.
CHARLES HENRY GIMINGHAM, of Camden Square, in the County of Middlesex.
IMPROVEMENTS IN THE CONSTRUCTION OF ELECTRIC LAMPS, AND IN SEALING
ELECTRICAL CONDUCTORS INTO AIR TIGHT RECEIVERS."
My improvements in the construction of electric lamps relate to the hermetic
sealing of the conductors carrying the carbon filament of an incandescent lamp into
the glass envelope or bulb. This bulb or envelope is usually exhausted or filled
with gas, and the maintenance of the vacuum or the gaseous atmosphere
indispensable to the continued working of the lamp depends upon the absolutely
hermetic sealing of the conductors into the bulb, which has hitherto been difficult
of accomplishment, even by highly skilled glass blowers.
The objects of the Invention are to ensure a perfectly hermetic joint, to prevent
longitudinal leakage through the conducting wires, to enable such lamps to be made
easily and cheaply without the employment of skilled labor, and to enable the
conductors to be withdrawn and replaced for the purpose of renewing the carbon
filament without the necessity of cutting the glass or of employing the blow pipe
to reseal it.
The Invention is also applicable to sealing electrical conductors of any size or
kind into chambers or receivers, either exhausted or filled with gas other than those
of clectric lamps.
According to my Invention the conductors are embedded in a stopper consisting
of a short and slightly conical glass tube accurately ground to fit the neck or stem
of the glass bulb or envelope through which tube the conductors are passed, and
into which plaster and cement are run around the conductors in the following way,
vis. A short length of the tube at the inner end is filled with plaster of Paris or
other hard cement to hold the conductors in place, and when this has set hard, the
middle portion of the length of the tube is filled with a particular kind of cement
known as "
vacuum cement," consisting of a mixture of beeswax and resin, which
does not give off vapor in vacuo, and is as impervious as glass to air, and the
remainder of the tube is filled up with plaster of Paris or other hard cement.
The stopper thus formed is cemented with the above mentioned vacuum cement
into the neck of the bulb or envelope, from which it may at any time be removed
for renewing the carbon filament by merely warming the cement, and replaced in
the same way.

page_text: To prevent longitudinal leakage through the conductors, each conductor before
being inserted in the stopper as above described, is severed, and the severed portions
of the conductor reconnected by twisting the end of the one portion about the
other. In embedding the conductors in the stopper, care is taken that the severed
ends and the junction shall be wholly embedded in the vacuum cement, so as to 5
prevent leakage from the one portion of the conductor to the other.
The bulb is exhausted or filled with gas through a small stem on the bulb, which
is sealed in the usual way by the blow pipe.